1 /*
   2  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   3  *
   4  * This code is free software; you can redistribute it and/or modify it
   5  * under the terms of the GNU General Public License version 2 only, as
   6  * published by the Free Software Foundation.  Oracle designates this
   7  * particular file as subject to the "Classpath" exception as provided
   8  * by Oracle in the LICENSE file that accompanied this code.
   9  *
  10  * This code is distributed in the hope that it will be useful, but WITHOUT
  11  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  12  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  13  * version 2 for more details (a copy is included in the LICENSE file that
  14  * accompanied this code).
  15  *
  16  * You should have received a copy of the GNU General Public License version
  17  * 2 along with this work; if not, write to the Free Software Foundation,
  18  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  19  *
  20  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  21  * or visit www.oracle.com if you need additional information or have any
  22  * questions.
  23  */
  24 
  25 /* pngrutil.c - utilities to read a PNG file
  26  *
  27  * This file is available under and governed by the GNU General Public
  28  * License version 2 only, as published by the Free Software Foundation.
  29  * However, the following notice accompanied the original version of this
  30  * file and, per its terms, should not be removed:
  31  *
  32  * Last changed in libpng 1.6.35 [July 15, 2018]
  33  * Copyright (c) 1998-2002,2004,2006-2018 Glenn Randers-Pehrson
  34  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
  35  * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
  36  *
  37  * This code is released under the libpng license.
  38  * For conditions of distribution and use, see the disclaimer
  39  * and license in png.h
  40  *
  41  * This file contains routines that are only called from within
  42  * libpng itself during the course of reading an image.
  43  */
  44 
  45 #include "pngpriv.h"
  46 
  47 #ifdef PNG_READ_SUPPORTED
  48 
  49 png_uint_32 PNGAPI
  50 png_get_uint_31(png_const_structrp png_ptr, png_const_bytep buf)
  51 {
  52    png_uint_32 uval = png_get_uint_32(buf);
  53 
  54    if (uval > PNG_UINT_31_MAX)
  55       png_error(png_ptr, "PNG unsigned integer out of range");
  56 
  57    return (uval);
  58 }
  59 
  60 #if defined(PNG_READ_gAMA_SUPPORTED) || defined(PNG_READ_cHRM_SUPPORTED)
  61 /* The following is a variation on the above for use with the fixed
  62  * point values used for gAMA and cHRM.  Instead of png_error it
  63  * issues a warning and returns (-1) - an invalid value because both
  64  * gAMA and cHRM use *unsigned* integers for fixed point values.
  65  */
  66 #define PNG_FIXED_ERROR (-1)
  67 
  68 static png_fixed_point /* PRIVATE */
  69 png_get_fixed_point(png_structrp png_ptr, png_const_bytep buf)
  70 {
  71    png_uint_32 uval = png_get_uint_32(buf);
  72 
  73    if (uval <= PNG_UINT_31_MAX)
  74       return (png_fixed_point)uval; /* known to be in range */
  75 
  76    /* The caller can turn off the warning by passing NULL. */
  77    if (png_ptr != NULL)
  78       png_warning(png_ptr, "PNG fixed point integer out of range");
  79 
  80    return PNG_FIXED_ERROR;
  81 }
  82 #endif
  83 
  84 #ifdef PNG_READ_INT_FUNCTIONS_SUPPORTED
  85 /* NOTE: the read macros will obscure these definitions, so that if
  86  * PNG_USE_READ_MACROS is set the library will not use them internally,
  87  * but the APIs will still be available externally.
  88  *
  89  * The parentheses around "PNGAPI function_name" in the following three
  90  * functions are necessary because they allow the macros to co-exist with
  91  * these (unused but exported) functions.
  92  */
  93 
  94 /* Grab an unsigned 32-bit integer from a buffer in big-endian format. */
  95 png_uint_32 (PNGAPI
  96 png_get_uint_32)(png_const_bytep buf)
  97 {
  98    png_uint_32 uval =
  99        ((png_uint_32)(*(buf    )) << 24) +
 100        ((png_uint_32)(*(buf + 1)) << 16) +
 101        ((png_uint_32)(*(buf + 2)) <<  8) +
 102        ((png_uint_32)(*(buf + 3))      ) ;
 103 
 104    return uval;
 105 }
 106 
 107 /* Grab a signed 32-bit integer from a buffer in big-endian format.  The
 108  * data is stored in the PNG file in two's complement format and there
 109  * is no guarantee that a 'png_int_32' is exactly 32 bits, therefore
 110  * the following code does a two's complement to native conversion.
 111  */
 112 png_int_32 (PNGAPI
 113 png_get_int_32)(png_const_bytep buf)
 114 {
 115    png_uint_32 uval = png_get_uint_32(buf);
 116    if ((uval & 0x80000000) == 0) /* non-negative */
 117       return (png_int_32)uval;
 118 
 119    uval = (uval ^ 0xffffffff) + 1;  /* 2's complement: -x = ~x+1 */
 120    if ((uval & 0x80000000) == 0) /* no overflow */
 121       return -(png_int_32)uval;
 122    /* The following has to be safe; this function only gets called on PNG data
 123     * and if we get here that data is invalid.  0 is the most safe value and
 124     * if not then an attacker would surely just generate a PNG with 0 instead.
 125     */
 126    return 0;
 127 }
 128 
 129 /* Grab an unsigned 16-bit integer from a buffer in big-endian format. */
 130 png_uint_16 (PNGAPI
 131 png_get_uint_16)(png_const_bytep buf)
 132 {
 133    /* ANSI-C requires an int value to accommodate at least 16 bits so this
 134     * works and allows the compiler not to worry about possible narrowing
 135     * on 32-bit systems.  (Pre-ANSI systems did not make integers smaller
 136     * than 16 bits either.)
 137     */
 138    unsigned int val =
 139        ((unsigned int)(*buf) << 8) +
 140        ((unsigned int)(*(buf + 1)));
 141 
 142    return (png_uint_16)val;
 143 }
 144 
 145 #endif /* READ_INT_FUNCTIONS */
 146 
 147 /* Read and check the PNG file signature */
 148 void /* PRIVATE */
 149 png_read_sig(png_structrp png_ptr, png_inforp info_ptr)
 150 {
 151    size_t num_checked, num_to_check;
 152 
 153    /* Exit if the user application does not expect a signature. */
 154    if (png_ptr->sig_bytes >= 8)
 155       return;
 156 
 157    num_checked = png_ptr->sig_bytes;
 158    num_to_check = 8 - num_checked;
 159 
 160 #ifdef PNG_IO_STATE_SUPPORTED
 161    png_ptr->io_state = PNG_IO_READING | PNG_IO_SIGNATURE;
 162 #endif
 163 
 164    /* The signature must be serialized in a single I/O call. */
 165    png_read_data(png_ptr, &(info_ptr->signature[num_checked]), num_to_check);
 166    png_ptr->sig_bytes = 8;
 167 
 168    if (png_sig_cmp(info_ptr->signature, num_checked, num_to_check) != 0)
 169    {
 170       if (num_checked < 4 &&
 171           png_sig_cmp(info_ptr->signature, num_checked, num_to_check - 4))
 172          png_error(png_ptr, "Not a PNG file");
 173       else
 174          png_error(png_ptr, "PNG file corrupted by ASCII conversion");
 175    }
 176    if (num_checked < 3)
 177       png_ptr->mode |= PNG_HAVE_PNG_SIGNATURE;
 178 }
 179 
 180 /* Read the chunk header (length + type name).
 181  * Put the type name into png_ptr->chunk_name, and return the length.
 182  */
 183 png_uint_32 /* PRIVATE */
 184 png_read_chunk_header(png_structrp png_ptr)
 185 {
 186    png_byte buf[8];
 187    png_uint_32 length;
 188 
 189 #ifdef PNG_IO_STATE_SUPPORTED
 190    png_ptr->io_state = PNG_IO_READING | PNG_IO_CHUNK_HDR;
 191 #endif
 192 
 193    /* Read the length and the chunk name.
 194     * This must be performed in a single I/O call.
 195     */
 196    png_read_data(png_ptr, buf, 8);
 197    length = png_get_uint_31(png_ptr, buf);
 198 
 199    /* Put the chunk name into png_ptr->chunk_name. */
 200    png_ptr->chunk_name = PNG_CHUNK_FROM_STRING(buf+4);
 201 
 202    png_debug2(0, "Reading %lx chunk, length = %lu",
 203        (unsigned long)png_ptr->chunk_name, (unsigned long)length);
 204 
 205    /* Reset the crc and run it over the chunk name. */
 206    png_reset_crc(png_ptr);
 207    png_calculate_crc(png_ptr, buf + 4, 4);
 208 
 209    /* Check to see if chunk name is valid. */
 210    png_check_chunk_name(png_ptr, png_ptr->chunk_name);
 211 
 212    /* Check for too-large chunk length */
 213    png_check_chunk_length(png_ptr, length);
 214 
 215 #ifdef PNG_IO_STATE_SUPPORTED
 216    png_ptr->io_state = PNG_IO_READING | PNG_IO_CHUNK_DATA;
 217 #endif
 218 
 219    return length;
 220 }
 221 
 222 /* Read data, and (optionally) run it through the CRC. */
 223 void /* PRIVATE */
 224 png_crc_read(png_structrp png_ptr, png_bytep buf, png_uint_32 length)
 225 {
 226    if (png_ptr == NULL)
 227       return;
 228 
 229    png_read_data(png_ptr, buf, length);
 230    png_calculate_crc(png_ptr, buf, length);
 231 }
 232 
 233 /* Optionally skip data and then check the CRC.  Depending on whether we
 234  * are reading an ancillary or critical chunk, and how the program has set
 235  * things up, we may calculate the CRC on the data and print a message.
 236  * Returns '1' if there was a CRC error, '0' otherwise.
 237  */
 238 int /* PRIVATE */
 239 png_crc_finish(png_structrp png_ptr, png_uint_32 skip)
 240 {
 241    /* The size of the local buffer for inflate is a good guess as to a
 242     * reasonable size to use for buffering reads from the application.
 243     */
 244    while (skip > 0)
 245    {
 246       png_uint_32 len;
 247       png_byte tmpbuf[PNG_INFLATE_BUF_SIZE];
 248 
 249       len = (sizeof tmpbuf);
 250       if (len > skip)
 251          len = skip;
 252       skip -= len;
 253 
 254       png_crc_read(png_ptr, tmpbuf, len);
 255    }
 256 
 257    if (png_crc_error(png_ptr) != 0)
 258    {
 259       if (PNG_CHUNK_ANCILLARY(png_ptr->chunk_name) != 0 ?
 260           (png_ptr->flags & PNG_FLAG_CRC_ANCILLARY_NOWARN) == 0 :
 261           (png_ptr->flags & PNG_FLAG_CRC_CRITICAL_USE) != 0)
 262       {
 263          png_chunk_warning(png_ptr, "CRC error");
 264       }
 265 
 266       else
 267          png_chunk_error(png_ptr, "CRC error");
 268 
 269       return (1);
 270    }
 271 
 272    return (0);
 273 }
 274 
 275 /* Compare the CRC stored in the PNG file with that calculated by libpng from
 276  * the data it has read thus far.
 277  */
 278 int /* PRIVATE */
 279 png_crc_error(png_structrp png_ptr)
 280 {
 281    png_byte crc_bytes[4];
 282    png_uint_32 crc;
 283    int need_crc = 1;
 284 
 285    if (PNG_CHUNK_ANCILLARY(png_ptr->chunk_name) != 0)
 286    {
 287       if ((png_ptr->flags & PNG_FLAG_CRC_ANCILLARY_MASK) ==
 288           (PNG_FLAG_CRC_ANCILLARY_USE | PNG_FLAG_CRC_ANCILLARY_NOWARN))
 289          need_crc = 0;
 290    }
 291 
 292    else /* critical */
 293    {
 294       if ((png_ptr->flags & PNG_FLAG_CRC_CRITICAL_IGNORE) != 0)
 295          need_crc = 0;
 296    }
 297 
 298 #ifdef PNG_IO_STATE_SUPPORTED
 299    png_ptr->io_state = PNG_IO_READING | PNG_IO_CHUNK_CRC;
 300 #endif
 301 
 302    /* The chunk CRC must be serialized in a single I/O call. */
 303    png_read_data(png_ptr, crc_bytes, 4);
 304 
 305    if (need_crc != 0)
 306    {
 307       crc = png_get_uint_32(crc_bytes);
 308       return ((int)(crc != png_ptr->crc));
 309    }
 310 
 311    else
 312       return (0);
 313 }
 314 
 315 #if defined(PNG_READ_iCCP_SUPPORTED) || defined(PNG_READ_iTXt_SUPPORTED) ||\
 316     defined(PNG_READ_pCAL_SUPPORTED) || defined(PNG_READ_sCAL_SUPPORTED) ||\
 317     defined(PNG_READ_sPLT_SUPPORTED) || defined(PNG_READ_tEXt_SUPPORTED) ||\
 318     defined(PNG_READ_zTXt_SUPPORTED) || defined(PNG_SEQUENTIAL_READ_SUPPORTED)
 319 /* Manage the read buffer; this simply reallocates the buffer if it is not small
 320  * enough (or if it is not allocated).  The routine returns a pointer to the
 321  * buffer; if an error occurs and 'warn' is set the routine returns NULL, else
 322  * it will call png_error (via png_malloc) on failure.  (warn == 2 means
 323  * 'silent').
 324  */
 325 static png_bytep
 326 png_read_buffer(png_structrp png_ptr, png_alloc_size_t new_size, int warn)
 327 {
 328    png_bytep buffer = png_ptr->read_buffer;
 329 
 330    if (buffer != NULL && new_size > png_ptr->read_buffer_size)
 331    {
 332       png_ptr->read_buffer = NULL;
 333       png_ptr->read_buffer = NULL;
 334       png_ptr->read_buffer_size = 0;
 335       png_free(png_ptr, buffer);
 336       buffer = NULL;
 337    }
 338 
 339    if (buffer == NULL)
 340    {
 341       buffer = png_voidcast(png_bytep, png_malloc_base(png_ptr, new_size));
 342 
 343       if (buffer != NULL)
 344       {
 345          memset(buffer, 0, new_size); /* just in case */
 346          png_ptr->read_buffer = buffer;
 347          png_ptr->read_buffer_size = new_size;
 348       }
 349 
 350       else if (warn < 2) /* else silent */
 351       {
 352          if (warn != 0)
 353              png_chunk_warning(png_ptr, "insufficient memory to read chunk");
 354 
 355          else
 356              png_chunk_error(png_ptr, "insufficient memory to read chunk");
 357       }
 358    }
 359 
 360    return buffer;
 361 }
 362 #endif /* READ_iCCP|iTXt|pCAL|sCAL|sPLT|tEXt|zTXt|SEQUENTIAL_READ */
 363 
 364 /* png_inflate_claim: claim the zstream for some nefarious purpose that involves
 365  * decompression.  Returns Z_OK on success, else a zlib error code.  It checks
 366  * the owner but, in final release builds, just issues a warning if some other
 367  * chunk apparently owns the stream.  Prior to release it does a png_error.
 368  */
 369 static int
 370 png_inflate_claim(png_structrp png_ptr, png_uint_32 owner)
 371 {
 372    if (png_ptr->zowner != 0)
 373    {
 374       char msg[64];
 375 
 376       PNG_STRING_FROM_CHUNK(msg, png_ptr->zowner);
 377       /* So the message that results is "<chunk> using zstream"; this is an
 378        * internal error, but is very useful for debugging.  i18n requirements
 379        * are minimal.
 380        */
 381       (void)png_safecat(msg, (sizeof msg), 4, " using zstream");
 382 #if PNG_RELEASE_BUILD
 383       png_chunk_warning(png_ptr, msg);
 384       png_ptr->zowner = 0;
 385 #else
 386       png_chunk_error(png_ptr, msg);
 387 #endif
 388    }
 389 
 390    /* Implementation note: unlike 'png_deflate_claim' this internal function
 391     * does not take the size of the data as an argument.  Some efficiency could
 392     * be gained by using this when it is known *if* the zlib stream itself does
 393     * not record the number; however, this is an illusion: the original writer
 394     * of the PNG may have selected a lower window size, and we really must
 395     * follow that because, for systems with with limited capabilities, we
 396     * would otherwise reject the application's attempts to use a smaller window
 397     * size (zlib doesn't have an interface to say "this or lower"!).
 398     *
 399     * inflateReset2 was added to zlib 1.2.4; before this the window could not be
 400     * reset, therefore it is necessary to always allocate the maximum window
 401     * size with earlier zlibs just in case later compressed chunks need it.
 402     */
 403    {
 404       int ret; /* zlib return code */
 405 #if ZLIB_VERNUM >= 0x1240
 406       int window_bits = 0;
 407 
 408 # if defined(PNG_SET_OPTION_SUPPORTED) && defined(PNG_MAXIMUM_INFLATE_WINDOW)
 409       if (((png_ptr->options >> PNG_MAXIMUM_INFLATE_WINDOW) & 3) ==
 410           PNG_OPTION_ON)
 411       {
 412          window_bits = 15;
 413          png_ptr->zstream_start = 0; /* fixed window size */
 414       }
 415 
 416       else
 417       {
 418          png_ptr->zstream_start = 1;
 419       }
 420 # endif
 421 
 422 #endif /* ZLIB_VERNUM >= 0x1240 */
 423 
 424       /* Set this for safety, just in case the previous owner left pointers to
 425        * memory allocations.
 426        */
 427       png_ptr->zstream.next_in = NULL;
 428       png_ptr->zstream.avail_in = 0;
 429       png_ptr->zstream.next_out = NULL;
 430       png_ptr->zstream.avail_out = 0;
 431 
 432       if ((png_ptr->flags & PNG_FLAG_ZSTREAM_INITIALIZED) != 0)
 433       {
 434 #if ZLIB_VERNUM >= 0x1240
 435          ret = inflateReset2(&png_ptr->zstream, window_bits);
 436 #else
 437          ret = inflateReset(&png_ptr->zstream);
 438 #endif
 439       }
 440 
 441       else
 442       {
 443 #if ZLIB_VERNUM >= 0x1240
 444          ret = inflateInit2(&png_ptr->zstream, window_bits);
 445 #else
 446          ret = inflateInit(&png_ptr->zstream);
 447 #endif
 448 
 449          if (ret == Z_OK)
 450             png_ptr->flags |= PNG_FLAG_ZSTREAM_INITIALIZED;
 451       }
 452 
 453 #if ZLIB_VERNUM >= 0x1290 && \
 454    defined(PNG_SET_OPTION_SUPPORTED) && defined(PNG_IGNORE_ADLER32)
 455       if (((png_ptr->options >> PNG_IGNORE_ADLER32) & 3) == PNG_OPTION_ON)
 456          /* Turn off validation of the ADLER32 checksum in IDAT chunks */
 457          ret = inflateValidate(&png_ptr->zstream, 0);
 458 #endif
 459 
 460       if (ret == Z_OK)
 461          png_ptr->zowner = owner;
 462 
 463       else
 464          png_zstream_error(png_ptr, ret);
 465 
 466       return ret;
 467    }
 468 
 469 #ifdef window_bits
 470 # undef window_bits
 471 #endif
 472 }
 473 
 474 #if ZLIB_VERNUM >= 0x1240
 475 /* Handle the start of the inflate stream if we called inflateInit2(strm,0);
 476  * in this case some zlib versions skip validation of the CINFO field and, in
 477  * certain circumstances, libpng may end up displaying an invalid image, in
 478  * contrast to implementations that call zlib in the normal way (e.g. libpng
 479  * 1.5).
 480  */
 481 int /* PRIVATE */
 482 png_zlib_inflate(png_structrp png_ptr, int flush)
 483 {
 484    if (png_ptr->zstream_start && png_ptr->zstream.avail_in > 0)
 485    {
 486       if ((*png_ptr->zstream.next_in >> 4) > 7)
 487       {
 488          png_ptr->zstream.msg = "invalid window size (libpng)";
 489          return Z_DATA_ERROR;
 490       }
 491 
 492       png_ptr->zstream_start = 0;
 493    }
 494 
 495    return inflate(&png_ptr->zstream, flush);
 496 }
 497 #endif /* Zlib >= 1.2.4 */
 498 
 499 #ifdef PNG_READ_COMPRESSED_TEXT_SUPPORTED
 500 #if defined(PNG_READ_zTXt_SUPPORTED) || defined (PNG_READ_iTXt_SUPPORTED)
 501 /* png_inflate now returns zlib error codes including Z_OK and Z_STREAM_END to
 502  * allow the caller to do multiple calls if required.  If the 'finish' flag is
 503  * set Z_FINISH will be passed to the final inflate() call and Z_STREAM_END must
 504  * be returned or there has been a problem, otherwise Z_SYNC_FLUSH is used and
 505  * Z_OK or Z_STREAM_END will be returned on success.
 506  *
 507  * The input and output sizes are updated to the actual amounts of data consumed
 508  * or written, not the amount available (as in a z_stream).  The data pointers
 509  * are not changed, so the next input is (data+input_size) and the next
 510  * available output is (output+output_size).
 511  */
 512 static int
 513 png_inflate(png_structrp png_ptr, png_uint_32 owner, int finish,
 514     /* INPUT: */ png_const_bytep input, png_uint_32p input_size_ptr,
 515     /* OUTPUT: */ png_bytep output, png_alloc_size_t *output_size_ptr)
 516 {
 517    if (png_ptr->zowner == owner) /* Else not claimed */
 518    {
 519       int ret;
 520       png_alloc_size_t avail_out = *output_size_ptr;
 521       png_uint_32 avail_in = *input_size_ptr;
 522 
 523       /* zlib can't necessarily handle more than 65535 bytes at once (i.e. it
 524        * can't even necessarily handle 65536 bytes) because the type uInt is
 525        * "16 bits or more".  Consequently it is necessary to chunk the input to
 526        * zlib.  This code uses ZLIB_IO_MAX, from pngpriv.h, as the maximum (the
 527        * maximum value that can be stored in a uInt.)  It is possible to set
 528        * ZLIB_IO_MAX to a lower value in pngpriv.h and this may sometimes have
 529        * a performance advantage, because it reduces the amount of data accessed
 530        * at each step and that may give the OS more time to page it in.
 531        */
 532       png_ptr->zstream.next_in = PNGZ_INPUT_CAST(input);
 533       /* avail_in and avail_out are set below from 'size' */
 534       png_ptr->zstream.avail_in = 0;
 535       png_ptr->zstream.avail_out = 0;
 536 
 537       /* Read directly into the output if it is available (this is set to
 538        * a local buffer below if output is NULL).
 539        */
 540       if (output != NULL)
 541          png_ptr->zstream.next_out = output;
 542 
 543       do
 544       {
 545          uInt avail;
 546          Byte local_buffer[PNG_INFLATE_BUF_SIZE];
 547 
 548          /* zlib INPUT BUFFER */
 549          /* The setting of 'avail_in' used to be outside the loop; by setting it
 550           * inside it is possible to chunk the input to zlib and simply rely on
 551           * zlib to advance the 'next_in' pointer.  This allows arbitrary
 552           * amounts of data to be passed through zlib at the unavoidable cost of
 553           * requiring a window save (memcpy of up to 32768 output bytes)
 554           * every ZLIB_IO_MAX input bytes.
 555           */
 556          avail_in += png_ptr->zstream.avail_in; /* not consumed last time */
 557 
 558          avail = ZLIB_IO_MAX;
 559 
 560          if (avail_in < avail)
 561             avail = (uInt)avail_in; /* safe: < than ZLIB_IO_MAX */
 562 
 563          avail_in -= avail;
 564          png_ptr->zstream.avail_in = avail;
 565 
 566          /* zlib OUTPUT BUFFER */
 567          avail_out += png_ptr->zstream.avail_out; /* not written last time */
 568 
 569          avail = ZLIB_IO_MAX; /* maximum zlib can process */
 570 
 571          if (output == NULL)
 572          {
 573             /* Reset the output buffer each time round if output is NULL and
 574              * make available the full buffer, up to 'remaining_space'
 575              */
 576             png_ptr->zstream.next_out = local_buffer;
 577             if ((sizeof local_buffer) < avail)
 578                avail = (sizeof local_buffer);
 579          }
 580 
 581          if (avail_out < avail)
 582             avail = (uInt)avail_out; /* safe: < ZLIB_IO_MAX */
 583 
 584          png_ptr->zstream.avail_out = avail;
 585          avail_out -= avail;
 586 
 587          /* zlib inflate call */
 588          /* In fact 'avail_out' may be 0 at this point, that happens at the end
 589           * of the read when the final LZ end code was not passed at the end of
 590           * the previous chunk of input data.  Tell zlib if we have reached the
 591           * end of the output buffer.
 592           */
 593          ret = PNG_INFLATE(png_ptr, avail_out > 0 ? Z_NO_FLUSH :
 594              (finish ? Z_FINISH : Z_SYNC_FLUSH));
 595       } while (ret == Z_OK);
 596 
 597       /* For safety kill the local buffer pointer now */
 598       if (output == NULL)
 599          png_ptr->zstream.next_out = NULL;
 600 
 601       /* Claw back the 'size' and 'remaining_space' byte counts. */
 602       avail_in += png_ptr->zstream.avail_in;
 603       avail_out += png_ptr->zstream.avail_out;
 604 
 605       /* Update the input and output sizes; the updated values are the amount
 606        * consumed or written, effectively the inverse of what zlib uses.
 607        */
 608       if (avail_out > 0)
 609          *output_size_ptr -= avail_out;
 610 
 611       if (avail_in > 0)
 612          *input_size_ptr -= avail_in;
 613 
 614       /* Ensure png_ptr->zstream.msg is set (even in the success case!) */
 615       png_zstream_error(png_ptr, ret);
 616       return ret;
 617    }
 618 
 619    else
 620    {
 621       /* This is a bad internal error.  The recovery assigns to the zstream msg
 622        * pointer, which is not owned by the caller, but this is safe; it's only
 623        * used on errors!
 624        */
 625       png_ptr->zstream.msg = PNGZ_MSG_CAST("zstream unclaimed");
 626       return Z_STREAM_ERROR;
 627    }
 628 }
 629 
 630 /*
 631  * Decompress trailing data in a chunk.  The assumption is that read_buffer
 632  * points at an allocated area holding the contents of a chunk with a
 633  * trailing compressed part.  What we get back is an allocated area
 634  * holding the original prefix part and an uncompressed version of the
 635  * trailing part (the malloc area passed in is freed).
 636  */
 637 static int
 638 png_decompress_chunk(png_structrp png_ptr,
 639     png_uint_32 chunklength, png_uint_32 prefix_size,
 640     png_alloc_size_t *newlength /* must be initialized to the maximum! */,
 641     int terminate /*add a '\0' to the end of the uncompressed data*/)
 642 {
 643    /* TODO: implement different limits for different types of chunk.
 644     *
 645     * The caller supplies *newlength set to the maximum length of the
 646     * uncompressed data, but this routine allocates space for the prefix and
 647     * maybe a '\0' terminator too.  We have to assume that 'prefix_size' is
 648     * limited only by the maximum chunk size.
 649     */
 650    png_alloc_size_t limit = PNG_SIZE_MAX;
 651 
 652 # ifdef PNG_SET_USER_LIMITS_SUPPORTED
 653    if (png_ptr->user_chunk_malloc_max > 0 &&
 654        png_ptr->user_chunk_malloc_max < limit)
 655       limit = png_ptr->user_chunk_malloc_max;
 656 # elif PNG_USER_CHUNK_MALLOC_MAX > 0
 657    if (PNG_USER_CHUNK_MALLOC_MAX < limit)
 658       limit = PNG_USER_CHUNK_MALLOC_MAX;
 659 # endif
 660 
 661    if (limit >= prefix_size + (terminate != 0))
 662    {
 663       int ret;
 664 
 665       limit -= prefix_size + (terminate != 0);
 666 
 667       if (limit < *newlength)
 668          *newlength = limit;
 669 
 670       /* Now try to claim the stream. */
 671       ret = png_inflate_claim(png_ptr, png_ptr->chunk_name);
 672 
 673       if (ret == Z_OK)
 674       {
 675          png_uint_32 lzsize = chunklength - prefix_size;
 676 
 677          ret = png_inflate(png_ptr, png_ptr->chunk_name, 1/*finish*/,
 678              /* input: */ png_ptr->read_buffer + prefix_size, &lzsize,
 679              /* output: */ NULL, newlength);
 680 
 681          if (ret == Z_STREAM_END)
 682          {
 683             /* Use 'inflateReset' here, not 'inflateReset2' because this
 684              * preserves the previously decided window size (otherwise it would
 685              * be necessary to store the previous window size.)  In practice
 686              * this doesn't matter anyway, because png_inflate will call inflate
 687              * with Z_FINISH in almost all cases, so the window will not be
 688              * maintained.
 689              */
 690             if (inflateReset(&png_ptr->zstream) == Z_OK)
 691             {
 692                /* Because of the limit checks above we know that the new,
 693                 * expanded, size will fit in a size_t (let alone an
 694                 * png_alloc_size_t).  Use png_malloc_base here to avoid an
 695                 * extra OOM message.
 696                 */
 697                png_alloc_size_t new_size = *newlength;
 698                png_alloc_size_t buffer_size = prefix_size + new_size +
 699                    (terminate != 0);
 700                png_bytep text = png_voidcast(png_bytep, png_malloc_base(png_ptr,
 701                    buffer_size));
 702 
 703                if (text != NULL)
 704                {
 705                   memset(text, 0, buffer_size);
 706 
 707                   ret = png_inflate(png_ptr, png_ptr->chunk_name, 1/*finish*/,
 708                       png_ptr->read_buffer + prefix_size, &lzsize,
 709                       text + prefix_size, newlength);
 710 
 711                   if (ret == Z_STREAM_END)
 712                   {
 713                      if (new_size == *newlength)
 714                      {
 715                         if (terminate != 0)
 716                            text[prefix_size + *newlength] = 0;
 717 
 718                         if (prefix_size > 0)
 719                            memcpy(text, png_ptr->read_buffer, prefix_size);
 720 
 721                         {
 722                            png_bytep old_ptr = png_ptr->read_buffer;
 723 
 724                            png_ptr->read_buffer = text;
 725                            png_ptr->read_buffer_size = buffer_size;
 726                            text = old_ptr; /* freed below */
 727                         }
 728                      }
 729 
 730                      else
 731                      {
 732                         /* The size changed on the second read, there can be no
 733                          * guarantee that anything is correct at this point.
 734                          * The 'msg' pointer has been set to "unexpected end of
 735                          * LZ stream", which is fine, but return an error code
 736                          * that the caller won't accept.
 737                          */
 738                         ret = PNG_UNEXPECTED_ZLIB_RETURN;
 739                      }
 740                   }
 741 
 742                   else if (ret == Z_OK)
 743                      ret = PNG_UNEXPECTED_ZLIB_RETURN; /* for safety */
 744 
 745                   /* Free the text pointer (this is the old read_buffer on
 746                    * success)
 747                    */
 748                   png_free(png_ptr, text);
 749 
 750                   /* This really is very benign, but it's still an error because
 751                    * the extra space may otherwise be used as a Trojan Horse.
 752                    */
 753                   if (ret == Z_STREAM_END &&
 754                       chunklength - prefix_size != lzsize)
 755                      png_chunk_benign_error(png_ptr, "extra compressed data");
 756                }
 757 
 758                else
 759                {
 760                   /* Out of memory allocating the buffer */
 761                   ret = Z_MEM_ERROR;
 762                   png_zstream_error(png_ptr, Z_MEM_ERROR);
 763                }
 764             }
 765 
 766             else
 767             {
 768                /* inflateReset failed, store the error message */
 769                png_zstream_error(png_ptr, ret);
 770                ret = PNG_UNEXPECTED_ZLIB_RETURN;
 771             }
 772          }
 773 
 774          else if (ret == Z_OK)
 775             ret = PNG_UNEXPECTED_ZLIB_RETURN;
 776 
 777          /* Release the claimed stream */
 778          png_ptr->zowner = 0;
 779       }
 780 
 781       else /* the claim failed */ if (ret == Z_STREAM_END) /* impossible! */
 782          ret = PNG_UNEXPECTED_ZLIB_RETURN;
 783 
 784       return ret;
 785    }
 786 
 787    else
 788    {
 789       /* Application/configuration limits exceeded */
 790       png_zstream_error(png_ptr, Z_MEM_ERROR);
 791       return Z_MEM_ERROR;
 792    }
 793 }
 794 #endif /* READ_zTXt || READ_iTXt */
 795 #endif /* READ_COMPRESSED_TEXT */
 796 
 797 #ifdef PNG_READ_iCCP_SUPPORTED
 798 /* Perform a partial read and decompress, producing 'avail_out' bytes and
 799  * reading from the current chunk as required.
 800  */
 801 static int
 802 png_inflate_read(png_structrp png_ptr, png_bytep read_buffer, uInt read_size,
 803     png_uint_32p chunk_bytes, png_bytep next_out, png_alloc_size_t *out_size,
 804     int finish)
 805 {
 806    if (png_ptr->zowner == png_ptr->chunk_name)
 807    {
 808       int ret;
 809 
 810       /* next_in and avail_in must have been initialized by the caller. */
 811       png_ptr->zstream.next_out = next_out;
 812       png_ptr->zstream.avail_out = 0; /* set in the loop */
 813 
 814       do
 815       {
 816          if (png_ptr->zstream.avail_in == 0)
 817          {
 818             if (read_size > *chunk_bytes)
 819                read_size = (uInt)*chunk_bytes;
 820             *chunk_bytes -= read_size;
 821 
 822             if (read_size > 0)
 823                png_crc_read(png_ptr, read_buffer, read_size);
 824 
 825             png_ptr->zstream.next_in = read_buffer;
 826             png_ptr->zstream.avail_in = read_size;
 827          }
 828 
 829          if (png_ptr->zstream.avail_out == 0)
 830          {
 831             uInt avail = ZLIB_IO_MAX;
 832             if (avail > *out_size)
 833                avail = (uInt)*out_size;
 834             *out_size -= avail;
 835 
 836             png_ptr->zstream.avail_out = avail;
 837          }
 838 
 839          /* Use Z_SYNC_FLUSH when there is no more chunk data to ensure that all
 840           * the available output is produced; this allows reading of truncated
 841           * streams.
 842           */
 843          ret = PNG_INFLATE(png_ptr, *chunk_bytes > 0 ?
 844              Z_NO_FLUSH : (finish ? Z_FINISH : Z_SYNC_FLUSH));
 845       }
 846       while (ret == Z_OK && (*out_size > 0 || png_ptr->zstream.avail_out > 0));
 847 
 848       *out_size += png_ptr->zstream.avail_out;
 849       png_ptr->zstream.avail_out = 0; /* Should not be required, but is safe */
 850 
 851       /* Ensure the error message pointer is always set: */
 852       png_zstream_error(png_ptr, ret);
 853       return ret;
 854    }
 855 
 856    else
 857    {
 858       png_ptr->zstream.msg = PNGZ_MSG_CAST("zstream unclaimed");
 859       return Z_STREAM_ERROR;
 860    }
 861 }
 862 #endif /* READ_iCCP */
 863 
 864 /* Read and check the IDHR chunk */
 865 
 866 void /* PRIVATE */
 867 png_handle_IHDR(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
 868 {
 869    png_byte buf[13];
 870    png_uint_32 width, height;
 871    int bit_depth, color_type, compression_type, filter_type;
 872    int interlace_type;
 873 
 874    png_debug(1, "in png_handle_IHDR");
 875 
 876    if ((png_ptr->mode & PNG_HAVE_IHDR) != 0)
 877       png_chunk_error(png_ptr, "out of place");
 878 
 879    /* Check the length */
 880    if (length != 13)
 881       png_chunk_error(png_ptr, "invalid");
 882 
 883    png_ptr->mode |= PNG_HAVE_IHDR;
 884 
 885    png_crc_read(png_ptr, buf, 13);
 886    png_crc_finish(png_ptr, 0);
 887 
 888    width = png_get_uint_31(png_ptr, buf);
 889    height = png_get_uint_31(png_ptr, buf + 4);
 890    bit_depth = buf[8];
 891    color_type = buf[9];
 892    compression_type = buf[10];
 893    filter_type = buf[11];
 894    interlace_type = buf[12];
 895 
 896    /* Set internal variables */
 897    png_ptr->width = width;
 898    png_ptr->height = height;
 899    png_ptr->bit_depth = (png_byte)bit_depth;
 900    png_ptr->interlaced = (png_byte)interlace_type;
 901    png_ptr->color_type = (png_byte)color_type;
 902 #ifdef PNG_MNG_FEATURES_SUPPORTED
 903    png_ptr->filter_type = (png_byte)filter_type;
 904 #endif
 905    png_ptr->compression_type = (png_byte)compression_type;
 906 
 907    /* Find number of channels */
 908    switch (png_ptr->color_type)
 909    {
 910       default: /* invalid, png_set_IHDR calls png_error */
 911       case PNG_COLOR_TYPE_GRAY:
 912       case PNG_COLOR_TYPE_PALETTE:
 913          png_ptr->channels = 1;
 914          break;
 915 
 916       case PNG_COLOR_TYPE_RGB:
 917          png_ptr->channels = 3;
 918          break;
 919 
 920       case PNG_COLOR_TYPE_GRAY_ALPHA:
 921          png_ptr->channels = 2;
 922          break;
 923 
 924       case PNG_COLOR_TYPE_RGB_ALPHA:
 925          png_ptr->channels = 4;
 926          break;
 927    }
 928 
 929    /* Set up other useful info */
 930    png_ptr->pixel_depth = (png_byte)(png_ptr->bit_depth * png_ptr->channels);
 931    png_ptr->rowbytes = PNG_ROWBYTES(png_ptr->pixel_depth, png_ptr->width);
 932    png_debug1(3, "bit_depth = %d", png_ptr->bit_depth);
 933    png_debug1(3, "channels = %d", png_ptr->channels);
 934    png_debug1(3, "rowbytes = %lu", (unsigned long)png_ptr->rowbytes);
 935    png_set_IHDR(png_ptr, info_ptr, width, height, bit_depth,
 936        color_type, interlace_type, compression_type, filter_type);
 937 }
 938 
 939 /* Read and check the palette */
 940 void /* PRIVATE */
 941 png_handle_PLTE(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
 942 {
 943    png_color palette[PNG_MAX_PALETTE_LENGTH];
 944    int max_palette_length, num, i;
 945 #ifdef PNG_POINTER_INDEXING_SUPPORTED
 946    png_colorp pal_ptr;
 947 #endif
 948 
 949    png_debug(1, "in png_handle_PLTE");
 950 
 951    if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
 952       png_chunk_error(png_ptr, "missing IHDR");
 953 
 954    /* Moved to before the 'after IDAT' check below because otherwise duplicate
 955     * PLTE chunks are potentially ignored (the spec says there shall not be more
 956     * than one PLTE, the error is not treated as benign, so this check trumps
 957     * the requirement that PLTE appears before IDAT.)
 958     */
 959    else if ((png_ptr->mode & PNG_HAVE_PLTE) != 0)
 960       png_chunk_error(png_ptr, "duplicate");
 961 
 962    else if ((png_ptr->mode & PNG_HAVE_IDAT) != 0)
 963    {
 964       /* This is benign because the non-benign error happened before, when an
 965        * IDAT was encountered in a color-mapped image with no PLTE.
 966        */
 967       png_crc_finish(png_ptr, length);
 968       png_chunk_benign_error(png_ptr, "out of place");
 969       return;
 970    }
 971 
 972    png_ptr->mode |= PNG_HAVE_PLTE;
 973 
 974    if ((png_ptr->color_type & PNG_COLOR_MASK_COLOR) == 0)
 975    {
 976       png_crc_finish(png_ptr, length);
 977       png_chunk_benign_error(png_ptr, "ignored in grayscale PNG");
 978       return;
 979    }
 980 
 981 #ifndef PNG_READ_OPT_PLTE_SUPPORTED
 982    if (png_ptr->color_type != PNG_COLOR_TYPE_PALETTE)
 983    {
 984       png_crc_finish(png_ptr, length);
 985       return;
 986    }
 987 #endif
 988 
 989    if (length > 3*PNG_MAX_PALETTE_LENGTH || length % 3)
 990    {
 991       png_crc_finish(png_ptr, length);
 992 
 993       if (png_ptr->color_type != PNG_COLOR_TYPE_PALETTE)
 994          png_chunk_benign_error(png_ptr, "invalid");
 995 
 996       else
 997          png_chunk_error(png_ptr, "invalid");
 998 
 999       return;
1000    }
1001 
1002    /* The cast is safe because 'length' is less than 3*PNG_MAX_PALETTE_LENGTH */
1003    num = (int)length / 3;
1004 
1005    /* If the palette has 256 or fewer entries but is too large for the bit
1006     * depth, we don't issue an error, to preserve the behavior of previous
1007     * libpng versions. We silently truncate the unused extra palette entries
1008     * here.
1009     */
1010    if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
1011       max_palette_length = (1 << png_ptr->bit_depth);
1012    else
1013       max_palette_length = PNG_MAX_PALETTE_LENGTH;
1014 
1015    if (num > max_palette_length)
1016       num = max_palette_length;
1017 
1018 #ifdef PNG_POINTER_INDEXING_SUPPORTED
1019    for (i = 0, pal_ptr = palette; i < num; i++, pal_ptr++)
1020    {
1021       png_byte buf[3];
1022 
1023       png_crc_read(png_ptr, buf, 3);
1024       pal_ptr->red = buf[0];
1025       pal_ptr->green = buf[1];
1026       pal_ptr->blue = buf[2];
1027    }
1028 #else
1029    for (i = 0; i < num; i++)
1030    {
1031       png_byte buf[3];
1032 
1033       png_crc_read(png_ptr, buf, 3);
1034       /* Don't depend upon png_color being any order */
1035       palette[i].red = buf[0];
1036       palette[i].green = buf[1];
1037       palette[i].blue = buf[2];
1038    }
1039 #endif
1040 
1041    /* If we actually need the PLTE chunk (ie for a paletted image), we do
1042     * whatever the normal CRC configuration tells us.  However, if we
1043     * have an RGB image, the PLTE can be considered ancillary, so
1044     * we will act as though it is.
1045     */
1046 #ifndef PNG_READ_OPT_PLTE_SUPPORTED
1047    if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
1048 #endif
1049    {
1050       png_crc_finish(png_ptr, (png_uint_32) (length - (unsigned int)num * 3));
1051    }
1052 
1053 #ifndef PNG_READ_OPT_PLTE_SUPPORTED
1054    else if (png_crc_error(png_ptr) != 0)  /* Only if we have a CRC error */
1055    {
1056       /* If we don't want to use the data from an ancillary chunk,
1057        * we have two options: an error abort, or a warning and we
1058        * ignore the data in this chunk (which should be OK, since
1059        * it's considered ancillary for a RGB or RGBA image).
1060        *
1061        * IMPLEMENTATION NOTE: this is only here because png_crc_finish uses the
1062        * chunk type to determine whether to check the ancillary or the critical
1063        * flags.
1064        */
1065       if ((png_ptr->flags & PNG_FLAG_CRC_ANCILLARY_USE) == 0)
1066       {
1067          if ((png_ptr->flags & PNG_FLAG_CRC_ANCILLARY_NOWARN) != 0)
1068             return;
1069 
1070          else
1071             png_chunk_error(png_ptr, "CRC error");
1072       }
1073 
1074       /* Otherwise, we (optionally) emit a warning and use the chunk. */
1075       else if ((png_ptr->flags & PNG_FLAG_CRC_ANCILLARY_NOWARN) == 0)
1076          png_chunk_warning(png_ptr, "CRC error");
1077    }
1078 #endif
1079 
1080    /* TODO: png_set_PLTE has the side effect of setting png_ptr->palette to its
1081     * own copy of the palette.  This has the side effect that when png_start_row
1082     * is called (this happens after any call to png_read_update_info) the
1083     * info_ptr palette gets changed.  This is extremely unexpected and
1084     * confusing.
1085     *
1086     * Fix this by not sharing the palette in this way.
1087     */
1088    png_set_PLTE(png_ptr, info_ptr, palette, num);
1089 
1090    /* The three chunks, bKGD, hIST and tRNS *must* appear after PLTE and before
1091     * IDAT.  Prior to 1.6.0 this was not checked; instead the code merely
1092     * checked the apparent validity of a tRNS chunk inserted before PLTE on a
1093     * palette PNG.  1.6.0 attempts to rigorously follow the standard and
1094     * therefore does a benign error if the erroneous condition is detected *and*
1095     * cancels the tRNS if the benign error returns.  The alternative is to
1096     * amend the standard since it would be rather hypocritical of the standards
1097     * maintainers to ignore it.
1098     */
1099 #ifdef PNG_READ_tRNS_SUPPORTED
1100    if (png_ptr->num_trans > 0 ||
1101        (info_ptr != NULL && (info_ptr->valid & PNG_INFO_tRNS) != 0))
1102    {
1103       /* Cancel this because otherwise it would be used if the transforms
1104        * require it.  Don't cancel the 'valid' flag because this would prevent
1105        * detection of duplicate chunks.
1106        */
1107       png_ptr->num_trans = 0;
1108 
1109       if (info_ptr != NULL)
1110          info_ptr->num_trans = 0;
1111 
1112       png_chunk_benign_error(png_ptr, "tRNS must be after");
1113    }
1114 #endif
1115 
1116 #ifdef PNG_READ_hIST_SUPPORTED
1117    if (info_ptr != NULL && (info_ptr->valid & PNG_INFO_hIST) != 0)
1118       png_chunk_benign_error(png_ptr, "hIST must be after");
1119 #endif
1120 
1121 #ifdef PNG_READ_bKGD_SUPPORTED
1122    if (info_ptr != NULL && (info_ptr->valid & PNG_INFO_bKGD) != 0)
1123       png_chunk_benign_error(png_ptr, "bKGD must be after");
1124 #endif
1125 }
1126 
1127 void /* PRIVATE */
1128 png_handle_IEND(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
1129 {
1130    png_debug(1, "in png_handle_IEND");
1131 
1132    if ((png_ptr->mode & PNG_HAVE_IHDR) == 0 ||
1133        (png_ptr->mode & PNG_HAVE_IDAT) == 0)
1134       png_chunk_error(png_ptr, "out of place");
1135 
1136    png_ptr->mode |= (PNG_AFTER_IDAT | PNG_HAVE_IEND);
1137 
1138    png_crc_finish(png_ptr, length);
1139 
1140    if (length != 0)
1141       png_chunk_benign_error(png_ptr, "invalid");
1142 
1143    PNG_UNUSED(info_ptr)
1144 }
1145 
1146 #ifdef PNG_READ_gAMA_SUPPORTED
1147 void /* PRIVATE */
1148 png_handle_gAMA(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
1149 {
1150    png_fixed_point igamma;
1151    png_byte buf[4];
1152 
1153    png_debug(1, "in png_handle_gAMA");
1154 
1155    if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
1156       png_chunk_error(png_ptr, "missing IHDR");
1157 
1158    else if ((png_ptr->mode & (PNG_HAVE_IDAT|PNG_HAVE_PLTE)) != 0)
1159    {
1160       png_crc_finish(png_ptr, length);
1161       png_chunk_benign_error(png_ptr, "out of place");
1162       return;
1163    }
1164 
1165    if (length != 4)
1166    {
1167       png_crc_finish(png_ptr, length);
1168       png_chunk_benign_error(png_ptr, "invalid");
1169       return;
1170    }
1171 
1172    png_crc_read(png_ptr, buf, 4);
1173 
1174    if (png_crc_finish(png_ptr, 0) != 0)
1175       return;
1176 
1177    igamma = png_get_fixed_point(NULL, buf);
1178 
1179    png_colorspace_set_gamma(png_ptr, &png_ptr->colorspace, igamma);
1180    png_colorspace_sync(png_ptr, info_ptr);
1181 }
1182 #endif
1183 
1184 #ifdef PNG_READ_sBIT_SUPPORTED
1185 void /* PRIVATE */
1186 png_handle_sBIT(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
1187 {
1188    unsigned int truelen, i;
1189    png_byte sample_depth;
1190    png_byte buf[4];
1191 
1192    png_debug(1, "in png_handle_sBIT");
1193 
1194    if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
1195       png_chunk_error(png_ptr, "missing IHDR");
1196 
1197    else if ((png_ptr->mode & (PNG_HAVE_IDAT|PNG_HAVE_PLTE)) != 0)
1198    {
1199       png_crc_finish(png_ptr, length);
1200       png_chunk_benign_error(png_ptr, "out of place");
1201       return;
1202    }
1203 
1204    if (info_ptr != NULL && (info_ptr->valid & PNG_INFO_sBIT) != 0)
1205    {
1206       png_crc_finish(png_ptr, length);
1207       png_chunk_benign_error(png_ptr, "duplicate");
1208       return;
1209    }
1210 
1211    if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
1212    {
1213       truelen = 3;
1214       sample_depth = 8;
1215    }
1216 
1217    else
1218    {
1219       truelen = png_ptr->channels;
1220       sample_depth = png_ptr->bit_depth;
1221    }
1222 
1223    if (length != truelen || length > 4)
1224    {
1225       png_chunk_benign_error(png_ptr, "invalid");
1226       png_crc_finish(png_ptr, length);
1227       return;
1228    }
1229 
1230    buf[0] = buf[1] = buf[2] = buf[3] = sample_depth;
1231    png_crc_read(png_ptr, buf, truelen);
1232 
1233    if (png_crc_finish(png_ptr, 0) != 0)
1234       return;
1235 
1236    for (i=0; i<truelen; ++i)
1237    {
1238       if (buf[i] == 0 || buf[i] > sample_depth)
1239       {
1240          png_chunk_benign_error(png_ptr, "invalid");
1241          return;
1242       }
1243    }
1244 
1245    if ((png_ptr->color_type & PNG_COLOR_MASK_COLOR) != 0)
1246    {
1247       png_ptr->sig_bit.red = buf[0];
1248       png_ptr->sig_bit.green = buf[1];
1249       png_ptr->sig_bit.blue = buf[2];
1250       png_ptr->sig_bit.alpha = buf[3];
1251    }
1252 
1253    else
1254    {
1255       png_ptr->sig_bit.gray = buf[0];
1256       png_ptr->sig_bit.red = buf[0];
1257       png_ptr->sig_bit.green = buf[0];
1258       png_ptr->sig_bit.blue = buf[0];
1259       png_ptr->sig_bit.alpha = buf[1];
1260    }
1261 
1262    png_set_sBIT(png_ptr, info_ptr, &(png_ptr->sig_bit));
1263 }
1264 #endif
1265 
1266 #ifdef PNG_READ_cHRM_SUPPORTED
1267 void /* PRIVATE */
1268 png_handle_cHRM(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
1269 {
1270    png_byte buf[32];
1271    png_xy xy;
1272 
1273    png_debug(1, "in png_handle_cHRM");
1274 
1275    if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
1276       png_chunk_error(png_ptr, "missing IHDR");
1277 
1278    else if ((png_ptr->mode & (PNG_HAVE_IDAT|PNG_HAVE_PLTE)) != 0)
1279    {
1280       png_crc_finish(png_ptr, length);
1281       png_chunk_benign_error(png_ptr, "out of place");
1282       return;
1283    }
1284 
1285    if (length != 32)
1286    {
1287       png_crc_finish(png_ptr, length);
1288       png_chunk_benign_error(png_ptr, "invalid");
1289       return;
1290    }
1291 
1292    png_crc_read(png_ptr, buf, 32);
1293 
1294    if (png_crc_finish(png_ptr, 0) != 0)
1295       return;
1296 
1297    xy.whitex = png_get_fixed_point(NULL, buf);
1298    xy.whitey = png_get_fixed_point(NULL, buf + 4);
1299    xy.redx   = png_get_fixed_point(NULL, buf + 8);
1300    xy.redy   = png_get_fixed_point(NULL, buf + 12);
1301    xy.greenx = png_get_fixed_point(NULL, buf + 16);
1302    xy.greeny = png_get_fixed_point(NULL, buf + 20);
1303    xy.bluex  = png_get_fixed_point(NULL, buf + 24);
1304    xy.bluey  = png_get_fixed_point(NULL, buf + 28);
1305 
1306    if (xy.whitex == PNG_FIXED_ERROR ||
1307        xy.whitey == PNG_FIXED_ERROR ||
1308        xy.redx   == PNG_FIXED_ERROR ||
1309        xy.redy   == PNG_FIXED_ERROR ||
1310        xy.greenx == PNG_FIXED_ERROR ||
1311        xy.greeny == PNG_FIXED_ERROR ||
1312        xy.bluex  == PNG_FIXED_ERROR ||
1313        xy.bluey  == PNG_FIXED_ERROR)
1314    {
1315       png_chunk_benign_error(png_ptr, "invalid values");
1316       return;
1317    }
1318 
1319    /* If a colorspace error has already been output skip this chunk */
1320    if ((png_ptr->colorspace.flags & PNG_COLORSPACE_INVALID) != 0)
1321       return;
1322 
1323    if ((png_ptr->colorspace.flags & PNG_COLORSPACE_FROM_cHRM) != 0)
1324    {
1325       png_ptr->colorspace.flags |= PNG_COLORSPACE_INVALID;
1326       png_colorspace_sync(png_ptr, info_ptr);
1327       png_chunk_benign_error(png_ptr, "duplicate");
1328       return;
1329    }
1330 
1331    png_ptr->colorspace.flags |= PNG_COLORSPACE_FROM_cHRM;
1332    (void)png_colorspace_set_chromaticities(png_ptr, &png_ptr->colorspace, &xy,
1333        1/*prefer cHRM values*/);
1334    png_colorspace_sync(png_ptr, info_ptr);
1335 }
1336 #endif
1337 
1338 #ifdef PNG_READ_sRGB_SUPPORTED
1339 void /* PRIVATE */
1340 png_handle_sRGB(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
1341 {
1342    png_byte intent;
1343 
1344    png_debug(1, "in png_handle_sRGB");
1345 
1346    if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
1347       png_chunk_error(png_ptr, "missing IHDR");
1348 
1349    else if ((png_ptr->mode & (PNG_HAVE_IDAT|PNG_HAVE_PLTE)) != 0)
1350    {
1351       png_crc_finish(png_ptr, length);
1352       png_chunk_benign_error(png_ptr, "out of place");
1353       return;
1354    }
1355 
1356    if (length != 1)
1357    {
1358       png_crc_finish(png_ptr, length);
1359       png_chunk_benign_error(png_ptr, "invalid");
1360       return;
1361    }
1362 
1363    png_crc_read(png_ptr, &intent, 1);
1364 
1365    if (png_crc_finish(png_ptr, 0) != 0)
1366       return;
1367 
1368    /* If a colorspace error has already been output skip this chunk */
1369    if ((png_ptr->colorspace.flags & PNG_COLORSPACE_INVALID) != 0)
1370       return;
1371 
1372    /* Only one sRGB or iCCP chunk is allowed, use the HAVE_INTENT flag to detect
1373     * this.
1374     */
1375    if ((png_ptr->colorspace.flags & PNG_COLORSPACE_HAVE_INTENT) != 0)
1376    {
1377       png_ptr->colorspace.flags |= PNG_COLORSPACE_INVALID;
1378       png_colorspace_sync(png_ptr, info_ptr);
1379       png_chunk_benign_error(png_ptr, "too many profiles");
1380       return;
1381    }
1382 
1383    (void)png_colorspace_set_sRGB(png_ptr, &png_ptr->colorspace, intent);
1384    png_colorspace_sync(png_ptr, info_ptr);
1385 }
1386 #endif /* READ_sRGB */
1387 
1388 #ifdef PNG_READ_iCCP_SUPPORTED
1389 void /* PRIVATE */
1390 png_handle_iCCP(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
1391 /* Note: this does not properly handle profiles that are > 64K under DOS */
1392 {
1393    png_const_charp errmsg = NULL; /* error message output, or no error */
1394    int finished = 0; /* crc checked */
1395 
1396    png_debug(1, "in png_handle_iCCP");
1397 
1398    if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
1399       png_chunk_error(png_ptr, "missing IHDR");
1400 
1401    else if ((png_ptr->mode & (PNG_HAVE_IDAT|PNG_HAVE_PLTE)) != 0)
1402    {
1403       png_crc_finish(png_ptr, length);
1404       png_chunk_benign_error(png_ptr, "out of place");
1405       return;
1406    }
1407 
1408    /* Consistent with all the above colorspace handling an obviously *invalid*
1409     * chunk is just ignored, so does not invalidate the color space.  An
1410     * alternative is to set the 'invalid' flags at the start of this routine
1411     * and only clear them in they were not set before and all the tests pass.
1412     */
1413 
1414    /* The keyword must be at least one character and there is a
1415     * terminator (0) byte and the compression method byte, and the
1416     * 'zlib' datastream is at least 11 bytes.
1417     */
1418    if (length < 14)
1419    {
1420       png_crc_finish(png_ptr, length);
1421       png_chunk_benign_error(png_ptr, "too short");
1422       return;
1423    }
1424 
1425    /* If a colorspace error has already been output skip this chunk */
1426    if ((png_ptr->colorspace.flags & PNG_COLORSPACE_INVALID) != 0)
1427    {
1428       png_crc_finish(png_ptr, length);
1429       return;
1430    }
1431 
1432    /* Only one sRGB or iCCP chunk is allowed, use the HAVE_INTENT flag to detect
1433     * this.
1434     */
1435    if ((png_ptr->colorspace.flags & PNG_COLORSPACE_HAVE_INTENT) == 0)
1436    {
1437       uInt read_length, keyword_length;
1438       char keyword[81];
1439 
1440       /* Find the keyword; the keyword plus separator and compression method
1441        * bytes can be at most 81 characters long.
1442        */
1443       read_length = 81; /* maximum */
1444       if (read_length > length)
1445          read_length = (uInt)length;
1446 
1447       png_crc_read(png_ptr, (png_bytep)keyword, read_length);
1448       length -= read_length;
1449 
1450       /* The minimum 'zlib' stream is assumed to be just the 2 byte header,
1451        * 5 bytes minimum 'deflate' stream, and the 4 byte checksum.
1452        */
1453       if (length < 11)
1454       {
1455          png_crc_finish(png_ptr, length);
1456          png_chunk_benign_error(png_ptr, "too short");
1457          return;
1458       }
1459 
1460       keyword_length = 0;
1461       while (keyword_length < 80 && keyword_length < read_length &&
1462          keyword[keyword_length] != 0)
1463          ++keyword_length;
1464 
1465       /* TODO: make the keyword checking common */
1466       if (keyword_length >= 1 && keyword_length <= 79)
1467       {
1468          /* We only understand '0' compression - deflate - so if we get a
1469           * different value we can't safely decode the chunk.
1470           */
1471          if (keyword_length+1 < read_length &&
1472             keyword[keyword_length+1] == PNG_COMPRESSION_TYPE_BASE)
1473          {
1474             read_length -= keyword_length+2;
1475 
1476             if (png_inflate_claim(png_ptr, png_iCCP) == Z_OK)
1477             {
1478                Byte profile_header[132]={0};
1479                Byte local_buffer[PNG_INFLATE_BUF_SIZE];
1480                png_alloc_size_t size = (sizeof profile_header);
1481 
1482                png_ptr->zstream.next_in = (Bytef*)keyword + (keyword_length+2);
1483                png_ptr->zstream.avail_in = read_length;
1484                (void)png_inflate_read(png_ptr, local_buffer,
1485                    (sizeof local_buffer), &length, profile_header, &size,
1486                    0/*finish: don't, because the output is too small*/);
1487 
1488                if (size == 0)
1489                {
1490                   /* We have the ICC profile header; do the basic header checks.
1491                    */
1492                   const png_uint_32 profile_length =
1493                      png_get_uint_32(profile_header);
1494 
1495                   if (png_icc_check_length(png_ptr, &png_ptr->colorspace,
1496                       keyword, profile_length) != 0)
1497                   {
1498                      /* The length is apparently ok, so we can check the 132
1499                       * byte header.
1500                       */
1501                      if (png_icc_check_header(png_ptr, &png_ptr->colorspace,
1502                          keyword, profile_length, profile_header,
1503                          png_ptr->color_type) != 0)
1504                      {
1505                         /* Now read the tag table; a variable size buffer is
1506                          * needed at this point, allocate one for the whole
1507                          * profile.  The header check has already validated
1508                          * that none of this stuff will overflow.
1509                          */
1510                         const png_uint_32 tag_count = png_get_uint_32(
1511                             profile_header+128);
1512                         png_bytep profile = png_read_buffer(png_ptr,
1513                             profile_length, 2/*silent*/);
1514 
1515                         if (profile != NULL)
1516                         {
1517                            memcpy(profile, profile_header,
1518                                (sizeof profile_header));
1519 
1520                            size = 12 * tag_count;
1521 
1522                            (void)png_inflate_read(png_ptr, local_buffer,
1523                                (sizeof local_buffer), &length,
1524                                profile + (sizeof profile_header), &size, 0);
1525 
1526                            /* Still expect a buffer error because we expect
1527                             * there to be some tag data!
1528                             */
1529                            if (size == 0)
1530                            {
1531                               if (png_icc_check_tag_table(png_ptr,
1532                                   &png_ptr->colorspace, keyword, profile_length,
1533                                   profile) != 0)
1534                               {
1535                                  /* The profile has been validated for basic
1536                                   * security issues, so read the whole thing in.
1537                                   */
1538                                  size = profile_length - (sizeof profile_header)
1539                                      - 12 * tag_count;
1540 
1541                                  (void)png_inflate_read(png_ptr, local_buffer,
1542                                      (sizeof local_buffer), &length,
1543                                      profile + (sizeof profile_header) +
1544                                      12 * tag_count, &size, 1/*finish*/);
1545 
1546                                  if (length > 0 && !(png_ptr->flags &
1547                                      PNG_FLAG_BENIGN_ERRORS_WARN))
1548                                     errmsg = "extra compressed data";
1549 
1550                                  /* But otherwise allow extra data: */
1551                                  else if (size == 0)
1552                                  {
1553                                     if (length > 0)
1554                                     {
1555                                        /* This can be handled completely, so
1556                                         * keep going.
1557                                         */
1558                                        png_chunk_warning(png_ptr,
1559                                            "extra compressed data");
1560                                     }
1561 
1562                                     png_crc_finish(png_ptr, length);
1563                                     finished = 1;
1564 
1565 # if defined(PNG_sRGB_SUPPORTED) && PNG_sRGB_PROFILE_CHECKS >= 0
1566                                     /* Check for a match against sRGB */
1567                                     png_icc_set_sRGB(png_ptr,
1568                                         &png_ptr->colorspace, profile,
1569                                         png_ptr->zstream.adler);
1570 # endif
1571 
1572                                     /* Steal the profile for info_ptr. */
1573                                     if (info_ptr != NULL)
1574                                     {
1575                                        png_free_data(png_ptr, info_ptr,
1576                                            PNG_FREE_ICCP, 0);
1577 
1578                                        info_ptr->iccp_name = png_voidcast(char*,
1579                                            png_malloc_base(png_ptr,
1580                                            keyword_length+1));
1581                                        if (info_ptr->iccp_name != NULL)
1582                                        {
1583                                           memcpy(info_ptr->iccp_name, keyword,
1584                                               keyword_length+1);
1585                                           info_ptr->iccp_proflen =
1586                                               profile_length;
1587                                           info_ptr->iccp_profile = profile;
1588                                           png_ptr->read_buffer = NULL; /*steal*/
1589                                           info_ptr->free_me |= PNG_FREE_ICCP;
1590                                           info_ptr->valid |= PNG_INFO_iCCP;
1591                                        }
1592 
1593                                        else
1594                                        {
1595                                           png_ptr->colorspace.flags |=
1596                                              PNG_COLORSPACE_INVALID;
1597                                           errmsg = "out of memory";
1598                                        }
1599                                     }
1600 
1601                                     /* else the profile remains in the read
1602                                      * buffer which gets reused for subsequent
1603                                      * chunks.
1604                                      */
1605 
1606                                     if (info_ptr != NULL)
1607                                        png_colorspace_sync(png_ptr, info_ptr);
1608 
1609                                     if (errmsg == NULL)
1610                                     {
1611                                        png_ptr->zowner = 0;
1612                                        return;
1613                                     }
1614                                  }
1615                                  if (errmsg == NULL)
1616                                     errmsg = png_ptr->zstream.msg;
1617                               }
1618                               /* else png_icc_check_tag_table output an error */
1619                            }
1620                            else /* profile truncated */
1621                               errmsg = png_ptr->zstream.msg;
1622                         }
1623 
1624                         else
1625                            errmsg = "out of memory";
1626                      }
1627 
1628                      /* else png_icc_check_header output an error */
1629                   }
1630 
1631                   /* else png_icc_check_length output an error */
1632                }
1633 
1634                else /* profile truncated */
1635                   errmsg = png_ptr->zstream.msg;
1636 
1637                /* Release the stream */
1638                png_ptr->zowner = 0;
1639             }
1640 
1641             else /* png_inflate_claim failed */
1642                errmsg = png_ptr->zstream.msg;
1643          }
1644 
1645          else
1646             errmsg = "bad compression method"; /* or missing */
1647       }
1648 
1649       else
1650          errmsg = "bad keyword";
1651    }
1652 
1653    else
1654       errmsg = "too many profiles";
1655 
1656    /* Failure: the reason is in 'errmsg' */
1657    if (finished == 0)
1658       png_crc_finish(png_ptr, length);
1659 
1660    png_ptr->colorspace.flags |= PNG_COLORSPACE_INVALID;
1661    png_colorspace_sync(png_ptr, info_ptr);
1662    if (errmsg != NULL) /* else already output */
1663       png_chunk_benign_error(png_ptr, errmsg);
1664 }
1665 #endif /* READ_iCCP */
1666 
1667 #ifdef PNG_READ_sPLT_SUPPORTED
1668 void /* PRIVATE */
1669 png_handle_sPLT(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
1670 /* Note: this does not properly handle chunks that are > 64K under DOS */
1671 {
1672    png_bytep entry_start, buffer;
1673    png_sPLT_t new_palette;
1674    png_sPLT_entryp pp;
1675    png_uint_32 data_length;
1676    int entry_size, i;
1677    png_uint_32 skip = 0;
1678    png_uint_32 dl;
1679    size_t max_dl;
1680 
1681    png_debug(1, "in png_handle_sPLT");
1682 
1683 #ifdef PNG_USER_LIMITS_SUPPORTED
1684    if (png_ptr->user_chunk_cache_max != 0)
1685    {
1686       if (png_ptr->user_chunk_cache_max == 1)
1687       {
1688          png_crc_finish(png_ptr, length);
1689          return;
1690       }
1691 
1692       if (--png_ptr->user_chunk_cache_max == 1)
1693       {
1694          png_warning(png_ptr, "No space in chunk cache for sPLT");
1695          png_crc_finish(png_ptr, length);
1696          return;
1697       }
1698    }
1699 #endif
1700 
1701    if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
1702       png_chunk_error(png_ptr, "missing IHDR");
1703 
1704    else if ((png_ptr->mode & PNG_HAVE_IDAT) != 0)
1705    {
1706       png_crc_finish(png_ptr, length);
1707       png_chunk_benign_error(png_ptr, "out of place");
1708       return;
1709    }
1710 
1711 #ifdef PNG_MAX_MALLOC_64K
1712    if (length > 65535U)
1713    {
1714       png_crc_finish(png_ptr, length);
1715       png_chunk_benign_error(png_ptr, "too large to fit in memory");
1716       return;
1717    }
1718 #endif
1719 
1720    buffer = png_read_buffer(png_ptr, length+1, 2/*silent*/);
1721    if (buffer == NULL)
1722    {
1723       png_crc_finish(png_ptr, length);
1724       png_chunk_benign_error(png_ptr, "out of memory");
1725       return;
1726    }
1727 
1728 
1729    /* WARNING: this may break if size_t is less than 32 bits; it is assumed
1730     * that the PNG_MAX_MALLOC_64K test is enabled in this case, but this is a
1731     * potential breakage point if the types in pngconf.h aren't exactly right.
1732     */
1733    png_crc_read(png_ptr, buffer, length);
1734 
1735    if (png_crc_finish(png_ptr, skip) != 0)
1736       return;
1737 
1738    buffer[length] = 0;
1739 
1740    for (entry_start = buffer; *entry_start; entry_start++)
1741       /* Empty loop to find end of name */ ;
1742 
1743    ++entry_start;
1744 
1745    /* A sample depth should follow the separator, and we should be on it  */
1746    if (length < 2U || entry_start > buffer + (length - 2U))
1747    {
1748       png_warning(png_ptr, "malformed sPLT chunk");
1749       return;
1750    }
1751 
1752    new_palette.depth = *entry_start++;
1753    entry_size = (new_palette.depth == 8 ? 6 : 10);
1754    /* This must fit in a png_uint_32 because it is derived from the original
1755     * chunk data length.
1756     */
1757    data_length = length - (png_uint_32)(entry_start - buffer);
1758 
1759    /* Integrity-check the data length */
1760    if ((data_length % (unsigned int)entry_size) != 0)
1761    {
1762       png_warning(png_ptr, "sPLT chunk has bad length");
1763       return;
1764    }
1765 
1766    dl = (png_uint_32)(data_length / (unsigned int)entry_size);
1767    max_dl = PNG_SIZE_MAX / (sizeof (png_sPLT_entry));
1768 
1769    if (dl > max_dl)
1770    {
1771       png_warning(png_ptr, "sPLT chunk too long");
1772       return;
1773    }
1774 
1775    new_palette.nentries = (png_int_32)(data_length / (unsigned int)entry_size);
1776 
1777    new_palette.entries = (png_sPLT_entryp)png_malloc_warn(png_ptr,
1778        (png_alloc_size_t) new_palette.nentries * (sizeof (png_sPLT_entry)));
1779 
1780    if (new_palette.entries == NULL)
1781    {
1782       png_warning(png_ptr, "sPLT chunk requires too much memory");
1783       return;
1784    }
1785 
1786 #ifdef PNG_POINTER_INDEXING_SUPPORTED
1787    for (i = 0; i < new_palette.nentries; i++)
1788    {
1789       pp = new_palette.entries + i;
1790 
1791       if (new_palette.depth == 8)
1792       {
1793          pp->red = *entry_start++;
1794          pp->green = *entry_start++;
1795          pp->blue = *entry_start++;
1796          pp->alpha = *entry_start++;
1797       }
1798 
1799       else
1800       {
1801          pp->red   = png_get_uint_16(entry_start); entry_start += 2;
1802          pp->green = png_get_uint_16(entry_start); entry_start += 2;
1803          pp->blue  = png_get_uint_16(entry_start); entry_start += 2;
1804          pp->alpha = png_get_uint_16(entry_start); entry_start += 2;
1805       }
1806 
1807       pp->frequency = png_get_uint_16(entry_start); entry_start += 2;
1808    }
1809 #else
1810    pp = new_palette.entries;
1811 
1812    for (i = 0; i < new_palette.nentries; i++)
1813    {
1814 
1815       if (new_palette.depth == 8)
1816       {
1817          pp[i].red   = *entry_start++;
1818          pp[i].green = *entry_start++;
1819          pp[i].blue  = *entry_start++;
1820          pp[i].alpha = *entry_start++;
1821       }
1822 
1823       else
1824       {
1825          pp[i].red   = png_get_uint_16(entry_start); entry_start += 2;
1826          pp[i].green = png_get_uint_16(entry_start); entry_start += 2;
1827          pp[i].blue  = png_get_uint_16(entry_start); entry_start += 2;
1828          pp[i].alpha = png_get_uint_16(entry_start); entry_start += 2;
1829       }
1830 
1831       pp[i].frequency = png_get_uint_16(entry_start); entry_start += 2;
1832    }
1833 #endif
1834 
1835    /* Discard all chunk data except the name and stash that */
1836    new_palette.name = (png_charp)buffer;
1837 
1838    png_set_sPLT(png_ptr, info_ptr, &new_palette, 1);
1839 
1840    png_free(png_ptr, new_palette.entries);
1841 }
1842 #endif /* READ_sPLT */
1843 
1844 #ifdef PNG_READ_tRNS_SUPPORTED
1845 void /* PRIVATE */
1846 png_handle_tRNS(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
1847 {
1848    png_byte readbuf[PNG_MAX_PALETTE_LENGTH];
1849 
1850    png_debug(1, "in png_handle_tRNS");
1851 
1852    if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
1853       png_chunk_error(png_ptr, "missing IHDR");
1854 
1855    else if ((png_ptr->mode & PNG_HAVE_IDAT) != 0)
1856    {
1857       png_crc_finish(png_ptr, length);
1858       png_chunk_benign_error(png_ptr, "out of place");
1859       return;
1860    }
1861 
1862    else if (info_ptr != NULL && (info_ptr->valid & PNG_INFO_tRNS) != 0)
1863    {
1864       png_crc_finish(png_ptr, length);
1865       png_chunk_benign_error(png_ptr, "duplicate");
1866       return;
1867    }
1868 
1869    if (png_ptr->color_type == PNG_COLOR_TYPE_GRAY)
1870    {
1871       png_byte buf[2];
1872 
1873       if (length != 2)
1874       {
1875          png_crc_finish(png_ptr, length);
1876          png_chunk_benign_error(png_ptr, "invalid");
1877          return;
1878       }
1879 
1880       png_crc_read(png_ptr, buf, 2);
1881       png_ptr->num_trans = 1;
1882       png_ptr->trans_color.gray = png_get_uint_16(buf);
1883    }
1884 
1885    else if (png_ptr->color_type == PNG_COLOR_TYPE_RGB)
1886    {
1887       png_byte buf[6];
1888 
1889       if (length != 6)
1890       {
1891          png_crc_finish(png_ptr, length);
1892          png_chunk_benign_error(png_ptr, "invalid");
1893          return;
1894       }
1895 
1896       png_crc_read(png_ptr, buf, length);
1897       png_ptr->num_trans = 1;
1898       png_ptr->trans_color.red = png_get_uint_16(buf);
1899       png_ptr->trans_color.green = png_get_uint_16(buf + 2);
1900       png_ptr->trans_color.blue = png_get_uint_16(buf + 4);
1901    }
1902 
1903    else if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
1904    {
1905       if ((png_ptr->mode & PNG_HAVE_PLTE) == 0)
1906       {
1907          /* TODO: is this actually an error in the ISO spec? */
1908          png_crc_finish(png_ptr, length);
1909          png_chunk_benign_error(png_ptr, "out of place");
1910          return;
1911       }
1912 
1913       if (length > (unsigned int) png_ptr->num_palette ||
1914          length > (unsigned int) PNG_MAX_PALETTE_LENGTH ||
1915          length == 0)
1916       {
1917          png_crc_finish(png_ptr, length);
1918          png_chunk_benign_error(png_ptr, "invalid");
1919          return;
1920       }
1921 
1922       png_crc_read(png_ptr, readbuf, length);
1923       png_ptr->num_trans = (png_uint_16)length;
1924    }
1925 
1926    else
1927    {
1928       png_crc_finish(png_ptr, length);
1929       png_chunk_benign_error(png_ptr, "invalid with alpha channel");
1930       return;
1931    }
1932 
1933    if (png_crc_finish(png_ptr, 0) != 0)
1934    {
1935       png_ptr->num_trans = 0;
1936       return;
1937    }
1938 
1939    /* TODO: this is a horrible side effect in the palette case because the
1940     * png_struct ends up with a pointer to the tRNS buffer owned by the
1941     * png_info.  Fix this.
1942     */
1943    png_set_tRNS(png_ptr, info_ptr, readbuf, png_ptr->num_trans,
1944        &(png_ptr->trans_color));
1945 }
1946 #endif
1947 
1948 #ifdef PNG_READ_bKGD_SUPPORTED
1949 void /* PRIVATE */
1950 png_handle_bKGD(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
1951 {
1952    unsigned int truelen;
1953    png_byte buf[6];
1954    png_color_16 background;
1955 
1956    png_debug(1, "in png_handle_bKGD");
1957 
1958    if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
1959       png_chunk_error(png_ptr, "missing IHDR");
1960 
1961    else if ((png_ptr->mode & PNG_HAVE_IDAT) != 0 ||
1962        (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE &&
1963        (png_ptr->mode & PNG_HAVE_PLTE) == 0))
1964    {
1965       png_crc_finish(png_ptr, length);
1966       png_chunk_benign_error(png_ptr, "out of place");
1967       return;
1968    }
1969 
1970    else if (info_ptr != NULL && (info_ptr->valid & PNG_INFO_bKGD) != 0)
1971    {
1972       png_crc_finish(png_ptr, length);
1973       png_chunk_benign_error(png_ptr, "duplicate");
1974       return;
1975    }
1976 
1977    if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
1978       truelen = 1;
1979 
1980    else if ((png_ptr->color_type & PNG_COLOR_MASK_COLOR) != 0)
1981       truelen = 6;
1982 
1983    else
1984       truelen = 2;
1985 
1986    if (length != truelen)
1987    {
1988       png_crc_finish(png_ptr, length);
1989       png_chunk_benign_error(png_ptr, "invalid");
1990       return;
1991    }
1992 
1993    png_crc_read(png_ptr, buf, truelen);
1994 
1995    if (png_crc_finish(png_ptr, 0) != 0)
1996       return;
1997 
1998    /* We convert the index value into RGB components so that we can allow
1999     * arbitrary RGB values for background when we have transparency, and
2000     * so it is easy to determine the RGB values of the background color
2001     * from the info_ptr struct.
2002     */
2003    if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
2004    {
2005       background.index = buf[0];
2006 
2007       if (info_ptr != NULL && info_ptr->num_palette != 0)
2008       {
2009          if (buf[0] >= info_ptr->num_palette)
2010          {
2011             png_chunk_benign_error(png_ptr, "invalid index");
2012             return;
2013          }
2014 
2015          background.red = (png_uint_16)png_ptr->palette[buf[0]].red;
2016          background.green = (png_uint_16)png_ptr->palette[buf[0]].green;
2017          background.blue = (png_uint_16)png_ptr->palette[buf[0]].blue;
2018       }
2019 
2020       else
2021          background.red = background.green = background.blue = 0;
2022 
2023       background.gray = 0;
2024    }
2025 
2026    else if ((png_ptr->color_type & PNG_COLOR_MASK_COLOR) == 0) /* GRAY */
2027    {
2028       if (png_ptr->bit_depth <= 8)
2029       {
2030          if (buf[0] != 0 || buf[1] >= (unsigned int)(1 << png_ptr->bit_depth))
2031          {
2032             png_chunk_benign_error(png_ptr, "invalid gray level");
2033             return;
2034          }
2035       }
2036 
2037       background.index = 0;
2038       background.red =
2039       background.green =
2040       background.blue =
2041       background.gray = png_get_uint_16(buf);
2042    }
2043 
2044    else
2045    {
2046       if (png_ptr->bit_depth <= 8)
2047       {
2048          if (buf[0] != 0 || buf[2] != 0 || buf[4] != 0)
2049          {
2050             png_chunk_benign_error(png_ptr, "invalid color");
2051             return;
2052          }
2053       }
2054 
2055       background.index = 0;
2056       background.red = png_get_uint_16(buf);
2057       background.green = png_get_uint_16(buf + 2);
2058       background.blue = png_get_uint_16(buf + 4);
2059       background.gray = 0;
2060    }
2061 
2062    png_set_bKGD(png_ptr, info_ptr, &background);
2063 }
2064 #endif
2065 
2066 #ifdef PNG_READ_eXIf_SUPPORTED
2067 void /* PRIVATE */
2068 png_handle_eXIf(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
2069 {
2070    unsigned int i;
2071 
2072    png_debug(1, "in png_handle_eXIf");
2073 
2074    if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
2075       png_chunk_error(png_ptr, "missing IHDR");
2076 
2077    if (length < 2)
2078    {
2079       png_crc_finish(png_ptr, length);
2080       png_chunk_benign_error(png_ptr, "too short");
2081       return;
2082    }
2083 
2084    else if (info_ptr == NULL || (info_ptr->valid & PNG_INFO_eXIf) != 0)
2085    {
2086       png_crc_finish(png_ptr, length);
2087       png_chunk_benign_error(png_ptr, "duplicate");
2088       return;
2089    }
2090 
2091    info_ptr->free_me |= PNG_FREE_EXIF;
2092 
2093    info_ptr->eXIf_buf = png_voidcast(png_bytep,
2094              png_malloc_warn(png_ptr, length));
2095 
2096    if (info_ptr->eXIf_buf == NULL)
2097    {
2098       png_crc_finish(png_ptr, length);
2099       png_chunk_benign_error(png_ptr, "out of memory");
2100       return;
2101    }
2102 
2103    for (i = 0; i < length; i++)
2104    {
2105       png_byte buf[1];
2106       png_crc_read(png_ptr, buf, 1);
2107       info_ptr->eXIf_buf[i] = buf[0];
2108       if (i == 1 && buf[0] != 'M' && buf[0] != 'I'
2109                  && info_ptr->eXIf_buf[0] != buf[0])
2110       {
2111          png_crc_finish(png_ptr, length);
2112          png_chunk_benign_error(png_ptr, "incorrect byte-order specifier");
2113          png_free(png_ptr, info_ptr->eXIf_buf);
2114          info_ptr->eXIf_buf = NULL;
2115          return;
2116       }
2117    }
2118 
2119    if (png_crc_finish(png_ptr, 0) != 0)
2120       return;
2121 
2122    png_set_eXIf_1(png_ptr, info_ptr, length, info_ptr->eXIf_buf);
2123 
2124    png_free(png_ptr, info_ptr->eXIf_buf);
2125    info_ptr->eXIf_buf = NULL;
2126 }
2127 #endif
2128 
2129 #ifdef PNG_READ_hIST_SUPPORTED
2130 void /* PRIVATE */
2131 png_handle_hIST(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
2132 {
2133    unsigned int num, i;
2134    png_uint_16 readbuf[PNG_MAX_PALETTE_LENGTH];
2135 
2136    png_debug(1, "in png_handle_hIST");
2137 
2138    if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
2139       png_chunk_error(png_ptr, "missing IHDR");
2140 
2141    else if ((png_ptr->mode & PNG_HAVE_IDAT) != 0 ||
2142        (png_ptr->mode & PNG_HAVE_PLTE) == 0)
2143    {
2144       png_crc_finish(png_ptr, length);
2145       png_chunk_benign_error(png_ptr, "out of place");
2146       return;
2147    }
2148 
2149    else if (info_ptr != NULL && (info_ptr->valid & PNG_INFO_hIST) != 0)
2150    {
2151       png_crc_finish(png_ptr, length);
2152       png_chunk_benign_error(png_ptr, "duplicate");
2153       return;
2154    }
2155 
2156    num = length / 2 ;
2157 
2158    if (num != (unsigned int) png_ptr->num_palette ||
2159        num > (unsigned int) PNG_MAX_PALETTE_LENGTH)
2160    {
2161       png_crc_finish(png_ptr, length);
2162       png_chunk_benign_error(png_ptr, "invalid");
2163       return;
2164    }
2165 
2166    for (i = 0; i < num; i++)
2167    {
2168       png_byte buf[2];
2169 
2170       png_crc_read(png_ptr, buf, 2);
2171       readbuf[i] = png_get_uint_16(buf);
2172    }
2173 
2174    if (png_crc_finish(png_ptr, 0) != 0)
2175       return;
2176 
2177    png_set_hIST(png_ptr, info_ptr, readbuf);
2178 }
2179 #endif
2180 
2181 #ifdef PNG_READ_pHYs_SUPPORTED
2182 void /* PRIVATE */
2183 png_handle_pHYs(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
2184 {
2185    png_byte buf[9];
2186    png_uint_32 res_x, res_y;
2187    int unit_type;
2188 
2189    png_debug(1, "in png_handle_pHYs");
2190 
2191    if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
2192       png_chunk_error(png_ptr, "missing IHDR");
2193 
2194    else if ((png_ptr->mode & PNG_HAVE_IDAT) != 0)
2195    {
2196       png_crc_finish(png_ptr, length);
2197       png_chunk_benign_error(png_ptr, "out of place");
2198       return;
2199    }
2200 
2201    else if (info_ptr != NULL && (info_ptr->valid & PNG_INFO_pHYs) != 0)
2202    {
2203       png_crc_finish(png_ptr, length);
2204       png_chunk_benign_error(png_ptr, "duplicate");
2205       return;
2206    }
2207 
2208    if (length != 9)
2209    {
2210       png_crc_finish(png_ptr, length);
2211       png_chunk_benign_error(png_ptr, "invalid");
2212       return;
2213    }
2214 
2215    png_crc_read(png_ptr, buf, 9);
2216 
2217    if (png_crc_finish(png_ptr, 0) != 0)
2218       return;
2219 
2220    res_x = png_get_uint_32(buf);
2221    res_y = png_get_uint_32(buf + 4);
2222    unit_type = buf[8];
2223    png_set_pHYs(png_ptr, info_ptr, res_x, res_y, unit_type);
2224 }
2225 #endif
2226 
2227 #ifdef PNG_READ_oFFs_SUPPORTED
2228 void /* PRIVATE */
2229 png_handle_oFFs(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
2230 {
2231    png_byte buf[9];
2232    png_int_32 offset_x, offset_y;
2233    int unit_type;
2234 
2235    png_debug(1, "in png_handle_oFFs");
2236 
2237    if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
2238       png_chunk_error(png_ptr, "missing IHDR");
2239 
2240    else if ((png_ptr->mode & PNG_HAVE_IDAT) != 0)
2241    {
2242       png_crc_finish(png_ptr, length);
2243       png_chunk_benign_error(png_ptr, "out of place");
2244       return;
2245    }
2246 
2247    else if (info_ptr != NULL && (info_ptr->valid & PNG_INFO_oFFs) != 0)
2248    {
2249       png_crc_finish(png_ptr, length);
2250       png_chunk_benign_error(png_ptr, "duplicate");
2251       return;
2252    }
2253 
2254    if (length != 9)
2255    {
2256       png_crc_finish(png_ptr, length);
2257       png_chunk_benign_error(png_ptr, "invalid");
2258       return;
2259    }
2260 
2261    png_crc_read(png_ptr, buf, 9);
2262 
2263    if (png_crc_finish(png_ptr, 0) != 0)
2264       return;
2265 
2266    offset_x = png_get_int_32(buf);
2267    offset_y = png_get_int_32(buf + 4);
2268    unit_type = buf[8];
2269    png_set_oFFs(png_ptr, info_ptr, offset_x, offset_y, unit_type);
2270 }
2271 #endif
2272 
2273 #ifdef PNG_READ_pCAL_SUPPORTED
2274 /* Read the pCAL chunk (described in the PNG Extensions document) */
2275 void /* PRIVATE */
2276 png_handle_pCAL(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
2277 {
2278    png_int_32 X0, X1;
2279    png_byte type, nparams;
2280    png_bytep buffer, buf, units, endptr;
2281    png_charpp params;
2282    int i;
2283 
2284    png_debug(1, "in png_handle_pCAL");
2285 
2286    if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
2287       png_chunk_error(png_ptr, "missing IHDR");
2288 
2289    else if ((png_ptr->mode & PNG_HAVE_IDAT) != 0)
2290    {
2291       png_crc_finish(png_ptr, length);
2292       png_chunk_benign_error(png_ptr, "out of place");
2293       return;
2294    }
2295 
2296    else if (info_ptr != NULL && (info_ptr->valid & PNG_INFO_pCAL) != 0)
2297    {
2298       png_crc_finish(png_ptr, length);
2299       png_chunk_benign_error(png_ptr, "duplicate");
2300       return;
2301    }
2302 
2303    png_debug1(2, "Allocating and reading pCAL chunk data (%u bytes)",
2304        length + 1);
2305 
2306    buffer = png_read_buffer(png_ptr, length+1, 2/*silent*/);
2307 
2308    if (buffer == NULL)
2309    {
2310       png_crc_finish(png_ptr, length);
2311       png_chunk_benign_error(png_ptr, "out of memory");
2312       return;
2313    }
2314 
2315    png_crc_read(png_ptr, buffer, length);
2316 
2317    if (png_crc_finish(png_ptr, 0) != 0)
2318       return;
2319 
2320    buffer[length] = 0; /* Null terminate the last string */
2321 
2322    png_debug(3, "Finding end of pCAL purpose string");
2323    for (buf = buffer; *buf; buf++)
2324       /* Empty loop */ ;
2325 
2326    endptr = buffer + length;
2327 
2328    /* We need to have at least 12 bytes after the purpose string
2329     * in order to get the parameter information.
2330     */
2331    if (endptr - buf <= 12)
2332    {
2333       png_chunk_benign_error(png_ptr, "invalid");
2334       return;
2335    }
2336 
2337    png_debug(3, "Reading pCAL X0, X1, type, nparams, and units");
2338    X0 = png_get_int_32((png_bytep)buf+1);
2339    X1 = png_get_int_32((png_bytep)buf+5);
2340    type = buf[9];
2341    nparams = buf[10];
2342    units = buf + 11;
2343 
2344    png_debug(3, "Checking pCAL equation type and number of parameters");
2345    /* Check that we have the right number of parameters for known
2346     * equation types.
2347     */
2348    if ((type == PNG_EQUATION_LINEAR && nparams != 2) ||
2349        (type == PNG_EQUATION_BASE_E && nparams != 3) ||
2350        (type == PNG_EQUATION_ARBITRARY && nparams != 3) ||
2351        (type == PNG_EQUATION_HYPERBOLIC && nparams != 4))
2352    {
2353       png_chunk_benign_error(png_ptr, "invalid parameter count");
2354       return;
2355    }
2356 
2357    else if (type >= PNG_EQUATION_LAST)
2358    {
2359       png_chunk_benign_error(png_ptr, "unrecognized equation type");
2360    }
2361 
2362    for (buf = units; *buf; buf++)
2363       /* Empty loop to move past the units string. */ ;
2364 
2365    png_debug(3, "Allocating pCAL parameters array");
2366 
2367    params = png_voidcast(png_charpp, png_malloc_warn(png_ptr,
2368        nparams * (sizeof (png_charp))));
2369 
2370    if (params == NULL)
2371    {
2372       png_chunk_benign_error(png_ptr, "out of memory");
2373       return;
2374    }
2375 
2376    /* Get pointers to the start of each parameter string. */
2377    for (i = 0; i < nparams; i++)
2378    {
2379       buf++; /* Skip the null string terminator from previous parameter. */
2380 
2381       png_debug1(3, "Reading pCAL parameter %d", i);
2382 
2383       for (params[i] = (png_charp)buf; buf <= endptr && *buf != 0; buf++)
2384          /* Empty loop to move past each parameter string */ ;
2385 
2386       /* Make sure we haven't run out of data yet */
2387       if (buf > endptr)
2388       {
2389          png_free(png_ptr, params);
2390          png_chunk_benign_error(png_ptr, "invalid data");
2391          return;
2392       }
2393    }
2394 
2395    png_set_pCAL(png_ptr, info_ptr, (png_charp)buffer, X0, X1, type, nparams,
2396        (png_charp)units, params);
2397 
2398    png_free(png_ptr, params);
2399 }
2400 #endif
2401 
2402 #ifdef PNG_READ_sCAL_SUPPORTED
2403 /* Read the sCAL chunk */
2404 void /* PRIVATE */
2405 png_handle_sCAL(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
2406 {
2407    png_bytep buffer;
2408    size_t i;
2409    int state;
2410 
2411    png_debug(1, "in png_handle_sCAL");
2412 
2413    if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
2414       png_chunk_error(png_ptr, "missing IHDR");
2415 
2416    else if ((png_ptr->mode & PNG_HAVE_IDAT) != 0)
2417    {
2418       png_crc_finish(png_ptr, length);
2419       png_chunk_benign_error(png_ptr, "out of place");
2420       return;
2421    }
2422 
2423    else if (info_ptr != NULL && (info_ptr->valid & PNG_INFO_sCAL) != 0)
2424    {
2425       png_crc_finish(png_ptr, length);
2426       png_chunk_benign_error(png_ptr, "duplicate");
2427       return;
2428    }
2429 
2430    /* Need unit type, width, \0, height: minimum 4 bytes */
2431    else if (length < 4)
2432    {
2433       png_crc_finish(png_ptr, length);
2434       png_chunk_benign_error(png_ptr, "invalid");
2435       return;
2436    }
2437 
2438    png_debug1(2, "Allocating and reading sCAL chunk data (%u bytes)",
2439        length + 1);
2440 
2441    buffer = png_read_buffer(png_ptr, length+1, 2/*silent*/);
2442 
2443    if (buffer == NULL)
2444    {
2445       png_chunk_benign_error(png_ptr, "out of memory");
2446       png_crc_finish(png_ptr, length);
2447       return;
2448    }
2449 
2450    png_crc_read(png_ptr, buffer, length);
2451    buffer[length] = 0; /* Null terminate the last string */
2452 
2453    if (png_crc_finish(png_ptr, 0) != 0)
2454       return;
2455 
2456    /* Validate the unit. */
2457    if (buffer[0] != 1 && buffer[0] != 2)
2458    {
2459       png_chunk_benign_error(png_ptr, "invalid unit");
2460       return;
2461    }
2462 
2463    /* Validate the ASCII numbers, need two ASCII numbers separated by
2464     * a '\0' and they need to fit exactly in the chunk data.
2465     */
2466    i = 1;
2467    state = 0;
2468 
2469    if (png_check_fp_number((png_const_charp)buffer, length, &state, &i) == 0 ||
2470        i >= length || buffer[i++] != 0)
2471       png_chunk_benign_error(png_ptr, "bad width format");
2472 
2473    else if (PNG_FP_IS_POSITIVE(state) == 0)
2474       png_chunk_benign_error(png_ptr, "non-positive width");
2475 
2476    else
2477    {
2478       size_t heighti = i;
2479 
2480       state = 0;
2481       if (png_check_fp_number((png_const_charp)buffer, length,
2482           &state, &i) == 0 || i != length)
2483          png_chunk_benign_error(png_ptr, "bad height format");
2484 
2485       else if (PNG_FP_IS_POSITIVE(state) == 0)
2486          png_chunk_benign_error(png_ptr, "non-positive height");
2487 
2488       else
2489          /* This is the (only) success case. */
2490          png_set_sCAL_s(png_ptr, info_ptr, buffer[0],
2491              (png_charp)buffer+1, (png_charp)buffer+heighti);
2492    }
2493 }
2494 #endif
2495 
2496 #ifdef PNG_READ_tIME_SUPPORTED
2497 void /* PRIVATE */
2498 png_handle_tIME(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
2499 {
2500    png_byte buf[7];
2501    png_time mod_time;
2502 
2503    png_debug(1, "in png_handle_tIME");
2504 
2505    if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
2506       png_chunk_error(png_ptr, "missing IHDR");
2507 
2508    else if (info_ptr != NULL && (info_ptr->valid & PNG_INFO_tIME) != 0)
2509    {
2510       png_crc_finish(png_ptr, length);
2511       png_chunk_benign_error(png_ptr, "duplicate");
2512       return;
2513    }
2514 
2515    if ((png_ptr->mode & PNG_HAVE_IDAT) != 0)
2516       png_ptr->mode |= PNG_AFTER_IDAT;
2517 
2518    if (length != 7)
2519    {
2520       png_crc_finish(png_ptr, length);
2521       png_chunk_benign_error(png_ptr, "invalid");
2522       return;
2523    }
2524 
2525    png_crc_read(png_ptr, buf, 7);
2526 
2527    if (png_crc_finish(png_ptr, 0) != 0)
2528       return;
2529 
2530    mod_time.second = buf[6];
2531    mod_time.minute = buf[5];
2532    mod_time.hour = buf[4];
2533    mod_time.day = buf[3];
2534    mod_time.month = buf[2];
2535    mod_time.year = png_get_uint_16(buf);
2536 
2537    png_set_tIME(png_ptr, info_ptr, &mod_time);
2538 }
2539 #endif
2540 
2541 #ifdef PNG_READ_tEXt_SUPPORTED
2542 /* Note: this does not properly handle chunks that are > 64K under DOS */
2543 void /* PRIVATE */
2544 png_handle_tEXt(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
2545 {
2546    png_text  text_info;
2547    png_bytep buffer;
2548    png_charp key;
2549    png_charp text;
2550    png_uint_32 skip = 0;
2551 
2552    png_debug(1, "in png_handle_tEXt");
2553 
2554 #ifdef PNG_USER_LIMITS_SUPPORTED
2555    if (png_ptr->user_chunk_cache_max != 0)
2556    {
2557       if (png_ptr->user_chunk_cache_max == 1)
2558       {
2559          png_crc_finish(png_ptr, length);
2560          return;
2561       }
2562 
2563       if (--png_ptr->user_chunk_cache_max == 1)
2564       {
2565          png_crc_finish(png_ptr, length);
2566          png_chunk_benign_error(png_ptr, "no space in chunk cache");
2567          return;
2568       }
2569    }
2570 #endif
2571 
2572    if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
2573       png_chunk_error(png_ptr, "missing IHDR");
2574 
2575    if ((png_ptr->mode & PNG_HAVE_IDAT) != 0)
2576       png_ptr->mode |= PNG_AFTER_IDAT;
2577 
2578 #ifdef PNG_MAX_MALLOC_64K
2579    if (length > 65535U)
2580    {
2581       png_crc_finish(png_ptr, length);
2582       png_chunk_benign_error(png_ptr, "too large to fit in memory");
2583       return;
2584    }
2585 #endif
2586 
2587    buffer = png_read_buffer(png_ptr, length+1, 1/*warn*/);
2588 
2589    if (buffer == NULL)
2590    {
2591       png_chunk_benign_error(png_ptr, "out of memory");
2592       return;
2593    }
2594 
2595    png_crc_read(png_ptr, buffer, length);
2596 
2597    if (png_crc_finish(png_ptr, skip) != 0)
2598       return;
2599 
2600    key = (png_charp)buffer;
2601    key[length] = 0;
2602 
2603    for (text = key; *text; text++)
2604       /* Empty loop to find end of key */ ;
2605 
2606    if (text != key + length)
2607       text++;
2608 
2609    text_info.compression = PNG_TEXT_COMPRESSION_NONE;
2610    text_info.key = key;
2611    text_info.lang = NULL;
2612    text_info.lang_key = NULL;
2613    text_info.itxt_length = 0;
2614    text_info.text = text;
2615    text_info.text_length = strlen(text);
2616 
2617    if (png_set_text_2(png_ptr, info_ptr, &text_info, 1) != 0)
2618       png_warning(png_ptr, "Insufficient memory to process text chunk");
2619 }
2620 #endif
2621 
2622 #ifdef PNG_READ_zTXt_SUPPORTED
2623 /* Note: this does not correctly handle chunks that are > 64K under DOS */
2624 void /* PRIVATE */
2625 png_handle_zTXt(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
2626 {
2627    png_const_charp errmsg = NULL;
2628    png_bytep       buffer;
2629    png_uint_32     keyword_length;
2630 
2631    png_debug(1, "in png_handle_zTXt");
2632 
2633 #ifdef PNG_USER_LIMITS_SUPPORTED
2634    if (png_ptr->user_chunk_cache_max != 0)
2635    {
2636       if (png_ptr->user_chunk_cache_max == 1)
2637       {
2638          png_crc_finish(png_ptr, length);
2639          return;
2640       }
2641 
2642       if (--png_ptr->user_chunk_cache_max == 1)
2643       {
2644          png_crc_finish(png_ptr, length);
2645          png_chunk_benign_error(png_ptr, "no space in chunk cache");
2646          return;
2647       }
2648    }
2649 #endif
2650 
2651    if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
2652       png_chunk_error(png_ptr, "missing IHDR");
2653 
2654    if ((png_ptr->mode & PNG_HAVE_IDAT) != 0)
2655       png_ptr->mode |= PNG_AFTER_IDAT;
2656 
2657    /* Note, "length" is sufficient here; we won't be adding
2658     * a null terminator later.
2659     */
2660    buffer = png_read_buffer(png_ptr, length, 2/*silent*/);
2661 
2662    if (buffer == NULL)
2663    {
2664       png_crc_finish(png_ptr, length);
2665       png_chunk_benign_error(png_ptr, "out of memory");
2666       return;
2667    }
2668 
2669    png_crc_read(png_ptr, buffer, length);
2670 
2671    if (png_crc_finish(png_ptr, 0) != 0)
2672       return;
2673 
2674    /* TODO: also check that the keyword contents match the spec! */
2675    for (keyword_length = 0;
2676       keyword_length < length && buffer[keyword_length] != 0;
2677       ++keyword_length)
2678       /* Empty loop to find end of name */ ;
2679 
2680    if (keyword_length > 79 || keyword_length < 1)
2681       errmsg = "bad keyword";
2682 
2683    /* zTXt must have some LZ data after the keyword, although it may expand to
2684     * zero bytes; we need a '\0' at the end of the keyword, the compression type
2685     * then the LZ data:
2686     */
2687    else if (keyword_length + 3 > length)
2688       errmsg = "truncated";
2689 
2690    else if (buffer[keyword_length+1] != PNG_COMPRESSION_TYPE_BASE)
2691       errmsg = "unknown compression type";
2692 
2693    else
2694    {
2695       png_alloc_size_t uncompressed_length = PNG_SIZE_MAX;
2696 
2697       /* TODO: at present png_decompress_chunk imposes a single application
2698        * level memory limit, this should be split to different values for iCCP
2699        * and text chunks.
2700        */
2701       if (png_decompress_chunk(png_ptr, length, keyword_length+2,
2702           &uncompressed_length, 1/*terminate*/) == Z_STREAM_END)
2703       {
2704          png_text text;
2705 
2706          if (png_ptr->read_buffer == NULL)
2707            errmsg="Read failure in png_handle_zTXt";
2708          else
2709          {
2710             /* It worked; png_ptr->read_buffer now looks like a tEXt chunk
2711              * except for the extra compression type byte and the fact that
2712              * it isn't necessarily '\0' terminated.
2713              */
2714             buffer = png_ptr->read_buffer;
2715             buffer[uncompressed_length+(keyword_length+2)] = 0;
2716 
2717             text.compression = PNG_TEXT_COMPRESSION_zTXt;
2718             text.key = (png_charp)buffer;
2719             text.text = (png_charp)(buffer + keyword_length+2);
2720             text.text_length = uncompressed_length;
2721             text.itxt_length = 0;
2722             text.lang = NULL;
2723             text.lang_key = NULL;
2724 
2725             if (png_set_text_2(png_ptr, info_ptr, &text, 1) != 0)
2726                errmsg = "insufficient memory";
2727          }
2728       }
2729 
2730       else
2731          errmsg = png_ptr->zstream.msg;
2732    }
2733 
2734    if (errmsg != NULL)
2735       png_chunk_benign_error(png_ptr, errmsg);
2736 }
2737 #endif
2738 
2739 #ifdef PNG_READ_iTXt_SUPPORTED
2740 /* Note: this does not correctly handle chunks that are > 64K under DOS */
2741 void /* PRIVATE */
2742 png_handle_iTXt(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
2743 {
2744    png_const_charp errmsg = NULL;
2745    png_bytep buffer;
2746    png_uint_32 prefix_length;
2747 
2748    png_debug(1, "in png_handle_iTXt");
2749 
2750 #ifdef PNG_USER_LIMITS_SUPPORTED
2751    if (png_ptr->user_chunk_cache_max != 0)
2752    {
2753       if (png_ptr->user_chunk_cache_max == 1)
2754       {
2755          png_crc_finish(png_ptr, length);
2756          return;
2757       }
2758 
2759       if (--png_ptr->user_chunk_cache_max == 1)
2760       {
2761          png_crc_finish(png_ptr, length);
2762          png_chunk_benign_error(png_ptr, "no space in chunk cache");
2763          return;
2764       }
2765    }
2766 #endif
2767 
2768    if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
2769       png_chunk_error(png_ptr, "missing IHDR");
2770 
2771    if ((png_ptr->mode & PNG_HAVE_IDAT) != 0)
2772       png_ptr->mode |= PNG_AFTER_IDAT;
2773 
2774    buffer = png_read_buffer(png_ptr, length+1, 1/*warn*/);
2775 
2776    if (buffer == NULL)
2777    {
2778       png_crc_finish(png_ptr, length);
2779       png_chunk_benign_error(png_ptr, "out of memory");
2780       return;
2781    }
2782 
2783    png_crc_read(png_ptr, buffer, length);
2784 
2785    if (png_crc_finish(png_ptr, 0) != 0)
2786       return;
2787 
2788    /* First the keyword. */
2789    for (prefix_length=0;
2790       prefix_length < length && buffer[prefix_length] != 0;
2791       ++prefix_length)
2792       /* Empty loop */ ;
2793 
2794    /* Perform a basic check on the keyword length here. */
2795    if (prefix_length > 79 || prefix_length < 1)
2796       errmsg = "bad keyword";
2797 
2798    /* Expect keyword, compression flag, compression type, language, translated
2799     * keyword (both may be empty but are 0 terminated) then the text, which may
2800     * be empty.
2801     */
2802    else if (prefix_length + 5 > length)
2803       errmsg = "truncated";
2804 
2805    else if (buffer[prefix_length+1] == 0 ||
2806       (buffer[prefix_length+1] == 1 &&
2807       buffer[prefix_length+2] == PNG_COMPRESSION_TYPE_BASE))
2808    {
2809       int compressed = buffer[prefix_length+1] != 0;
2810       png_uint_32 language_offset, translated_keyword_offset;
2811       png_alloc_size_t uncompressed_length = 0;
2812 
2813       /* Now the language tag */
2814       prefix_length += 3;
2815       language_offset = prefix_length;
2816 
2817       for (; prefix_length < length && buffer[prefix_length] != 0;
2818          ++prefix_length)
2819          /* Empty loop */ ;
2820 
2821       /* WARNING: the length may be invalid here, this is checked below. */
2822       translated_keyword_offset = ++prefix_length;
2823 
2824       for (; prefix_length < length && buffer[prefix_length] != 0;
2825          ++prefix_length)
2826          /* Empty loop */ ;
2827 
2828       /* prefix_length should now be at the trailing '\0' of the translated
2829        * keyword, but it may already be over the end.  None of this arithmetic
2830        * can overflow because chunks are at most 2^31 bytes long, but on 16-bit
2831        * systems the available allocation may overflow.
2832        */
2833       ++prefix_length;
2834 
2835       if (compressed == 0 && prefix_length <= length)
2836          uncompressed_length = length - prefix_length;
2837 
2838       else if (compressed != 0 && prefix_length < length)
2839       {
2840          uncompressed_length = PNG_SIZE_MAX;
2841 
2842          /* TODO: at present png_decompress_chunk imposes a single application
2843           * level memory limit, this should be split to different values for
2844           * iCCP and text chunks.
2845           */
2846          if (png_decompress_chunk(png_ptr, length, prefix_length,
2847              &uncompressed_length, 1/*terminate*/) == Z_STREAM_END)
2848             buffer = png_ptr->read_buffer;
2849 
2850          else
2851             errmsg = png_ptr->zstream.msg;
2852       }
2853 
2854       else
2855          errmsg = "truncated";
2856 
2857       if (errmsg == NULL)
2858       {
2859          png_text text;
2860 
2861          buffer[uncompressed_length+prefix_length] = 0;
2862 
2863          if (compressed == 0)
2864             text.compression = PNG_ITXT_COMPRESSION_NONE;
2865 
2866          else
2867             text.compression = PNG_ITXT_COMPRESSION_zTXt;
2868 
2869          text.key = (png_charp)buffer;
2870          text.lang = (png_charp)buffer + language_offset;
2871          text.lang_key = (png_charp)buffer + translated_keyword_offset;
2872          text.text = (png_charp)buffer + prefix_length;
2873          text.text_length = 0;
2874          text.itxt_length = uncompressed_length;
2875 
2876          if (png_set_text_2(png_ptr, info_ptr, &text, 1) != 0)
2877             errmsg = "insufficient memory";
2878       }
2879    }
2880 
2881    else
2882       errmsg = "bad compression info";
2883 
2884    if (errmsg != NULL)
2885       png_chunk_benign_error(png_ptr, errmsg);
2886 }
2887 #endif
2888 
2889 #ifdef PNG_READ_UNKNOWN_CHUNKS_SUPPORTED
2890 /* Utility function for png_handle_unknown; set up png_ptr::unknown_chunk */
2891 static int
2892 png_cache_unknown_chunk(png_structrp png_ptr, png_uint_32 length)
2893 {
2894    png_alloc_size_t limit = PNG_SIZE_MAX;
2895 
2896    if (png_ptr->unknown_chunk.data != NULL)
2897    {
2898       png_free(png_ptr, png_ptr->unknown_chunk.data);
2899       png_ptr->unknown_chunk.data = NULL;
2900    }
2901 
2902 #  ifdef PNG_SET_USER_LIMITS_SUPPORTED
2903    if (png_ptr->user_chunk_malloc_max > 0 &&
2904        png_ptr->user_chunk_malloc_max < limit)
2905       limit = png_ptr->user_chunk_malloc_max;
2906 
2907 #  elif PNG_USER_CHUNK_MALLOC_MAX > 0
2908    if (PNG_USER_CHUNK_MALLOC_MAX < limit)
2909       limit = PNG_USER_CHUNK_MALLOC_MAX;
2910 #  endif
2911 
2912    if (length <= limit)
2913    {
2914       PNG_CSTRING_FROM_CHUNK(png_ptr->unknown_chunk.name, png_ptr->chunk_name);
2915       /* The following is safe because of the PNG_SIZE_MAX init above */
2916       png_ptr->unknown_chunk.size = (size_t)length/*SAFE*/;
2917       /* 'mode' is a flag array, only the bottom four bits matter here */
2918       png_ptr->unknown_chunk.location = (png_byte)png_ptr->mode/*SAFE*/;
2919 
2920       if (length == 0)
2921          png_ptr->unknown_chunk.data = NULL;
2922 
2923       else
2924       {
2925          /* Do a 'warn' here - it is handled below. */
2926          png_ptr->unknown_chunk.data = png_voidcast(png_bytep,
2927              png_malloc_warn(png_ptr, length));
2928       }
2929    }
2930 
2931    if (png_ptr->unknown_chunk.data == NULL && length > 0)
2932    {
2933       /* This is benign because we clean up correctly */
2934       png_crc_finish(png_ptr, length);
2935       png_chunk_benign_error(png_ptr, "unknown chunk exceeds memory limits");
2936       return 0;
2937    }
2938 
2939    else
2940    {
2941       if (length > 0)
2942          png_crc_read(png_ptr, png_ptr->unknown_chunk.data, length);
2943       png_crc_finish(png_ptr, 0);
2944       return 1;
2945    }
2946 }
2947 #endif /* READ_UNKNOWN_CHUNKS */
2948 
2949 /* Handle an unknown, or known but disabled, chunk */
2950 void /* PRIVATE */
2951 png_handle_unknown(png_structrp png_ptr, png_inforp info_ptr,
2952     png_uint_32 length, int keep)
2953 {
2954    int handled = 0; /* the chunk was handled */
2955 
2956    png_debug(1, "in png_handle_unknown");
2957 
2958 #ifdef PNG_READ_UNKNOWN_CHUNKS_SUPPORTED
2959    /* NOTE: this code is based on the code in libpng-1.4.12 except for fixing
2960     * the bug which meant that setting a non-default behavior for a specific
2961     * chunk would be ignored (the default was always used unless a user
2962     * callback was installed).
2963     *
2964     * 'keep' is the value from the png_chunk_unknown_handling, the setting for
2965     * this specific chunk_name, if PNG_HANDLE_AS_UNKNOWN_SUPPORTED, if not it
2966     * will always be PNG_HANDLE_CHUNK_AS_DEFAULT and it needs to be set here.
2967     * This is just an optimization to avoid multiple calls to the lookup
2968     * function.
2969     */
2970 #  ifndef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
2971 #     ifdef PNG_SET_UNKNOWN_CHUNKS_SUPPORTED
2972    keep = png_chunk_unknown_handling(png_ptr, png_ptr->chunk_name);
2973 #     endif
2974 #  endif
2975 
2976    /* One of the following methods will read the chunk or skip it (at least one
2977     * of these is always defined because this is the only way to switch on
2978     * PNG_READ_UNKNOWN_CHUNKS_SUPPORTED)
2979     */
2980 #  ifdef PNG_READ_USER_CHUNKS_SUPPORTED
2981    /* The user callback takes precedence over the chunk keep value, but the
2982     * keep value is still required to validate a save of a critical chunk.
2983     */
2984    if (png_ptr->read_user_chunk_fn != NULL)
2985    {
2986       if (png_cache_unknown_chunk(png_ptr, length) != 0)
2987       {
2988          /* Callback to user unknown chunk handler */
2989          int ret = (*(png_ptr->read_user_chunk_fn))(png_ptr,
2990              &png_ptr->unknown_chunk);
2991 
2992          /* ret is:
2993           * negative: An error occurred; png_chunk_error will be called.
2994           *     zero: The chunk was not handled, the chunk will be discarded
2995           *           unless png_set_keep_unknown_chunks has been used to set
2996           *           a 'keep' behavior for this particular chunk, in which
2997           *           case that will be used.  A critical chunk will cause an
2998           *           error at this point unless it is to be saved.
2999           * positive: The chunk was handled, libpng will ignore/discard it.
3000           */
3001          if (ret < 0)
3002             png_chunk_error(png_ptr, "error in user chunk");
3003 
3004          else if (ret == 0)
3005          {
3006             /* If the keep value is 'default' or 'never' override it, but
3007              * still error out on critical chunks unless the keep value is
3008              * 'always'  While this is weird it is the behavior in 1.4.12.
3009              * A possible improvement would be to obey the value set for the
3010              * chunk, but this would be an API change that would probably
3011              * damage some applications.
3012              *
3013              * The png_app_warning below catches the case that matters, where
3014              * the application has not set specific save or ignore for this
3015              * chunk or global save or ignore.
3016              */
3017             if (keep < PNG_HANDLE_CHUNK_IF_SAFE)
3018             {
3019 #              ifdef PNG_SET_UNKNOWN_CHUNKS_SUPPORTED
3020                if (png_ptr->unknown_default < PNG_HANDLE_CHUNK_IF_SAFE)
3021                {
3022                   png_chunk_warning(png_ptr, "Saving unknown chunk:");
3023                   png_app_warning(png_ptr,
3024                       "forcing save of an unhandled chunk;"
3025                       " please call png_set_keep_unknown_chunks");
3026                       /* with keep = PNG_HANDLE_CHUNK_IF_SAFE */
3027                }
3028 #              endif
3029                keep = PNG_HANDLE_CHUNK_IF_SAFE;
3030             }
3031          }
3032 
3033          else /* chunk was handled */
3034          {
3035             handled = 1;
3036             /* Critical chunks can be safely discarded at this point. */
3037             keep = PNG_HANDLE_CHUNK_NEVER;
3038          }
3039       }
3040 
3041       else
3042          keep = PNG_HANDLE_CHUNK_NEVER; /* insufficient memory */
3043    }
3044 
3045    else
3046    /* Use the SAVE_UNKNOWN_CHUNKS code or skip the chunk */
3047 #  endif /* READ_USER_CHUNKS */
3048 
3049 #  ifdef PNG_SAVE_UNKNOWN_CHUNKS_SUPPORTED
3050    {
3051       /* keep is currently just the per-chunk setting, if there was no
3052        * setting change it to the global default now (not that this may
3053        * still be AS_DEFAULT) then obtain the cache of the chunk if required,
3054        * if not simply skip the chunk.
3055        */
3056       if (keep == PNG_HANDLE_CHUNK_AS_DEFAULT)
3057          keep = png_ptr->unknown_default;
3058 
3059       if (keep == PNG_HANDLE_CHUNK_ALWAYS ||
3060          (keep == PNG_HANDLE_CHUNK_IF_SAFE &&
3061           PNG_CHUNK_ANCILLARY(png_ptr->chunk_name)))
3062       {
3063          if (png_cache_unknown_chunk(png_ptr, length) == 0)
3064             keep = PNG_HANDLE_CHUNK_NEVER;
3065       }
3066 
3067       else
3068          png_crc_finish(png_ptr, length);
3069    }
3070 #  else
3071 #     ifndef PNG_READ_USER_CHUNKS_SUPPORTED
3072 #        error no method to support READ_UNKNOWN_CHUNKS
3073 #     endif
3074 
3075    {
3076       /* If here there is no read callback pointer set and no support is
3077        * compiled in to just save the unknown chunks, so simply skip this
3078        * chunk.  If 'keep' is something other than AS_DEFAULT or NEVER then
3079        * the app has erroneously asked for unknown chunk saving when there
3080        * is no support.
3081        */
3082       if (keep > PNG_HANDLE_CHUNK_NEVER)
3083          png_app_error(png_ptr, "no unknown chunk support available");
3084 
3085       png_crc_finish(png_ptr, length);
3086    }
3087 #  endif
3088 
3089 #  ifdef PNG_STORE_UNKNOWN_CHUNKS_SUPPORTED
3090    /* Now store the chunk in the chunk list if appropriate, and if the limits
3091     * permit it.
3092     */
3093    if (keep == PNG_HANDLE_CHUNK_ALWAYS ||
3094       (keep == PNG_HANDLE_CHUNK_IF_SAFE &&
3095        PNG_CHUNK_ANCILLARY(png_ptr->chunk_name)))
3096    {
3097 #     ifdef PNG_USER_LIMITS_SUPPORTED
3098       switch (png_ptr->user_chunk_cache_max)
3099       {
3100          case 2:
3101             png_ptr->user_chunk_cache_max = 1;
3102             png_chunk_benign_error(png_ptr, "no space in chunk cache");
3103             /* FALLTHROUGH */
3104          case 1:
3105             /* NOTE: prior to 1.6.0 this case resulted in an unknown critical
3106              * chunk being skipped, now there will be a hard error below.
3107              */
3108             break;
3109 
3110          default: /* not at limit */
3111             --(png_ptr->user_chunk_cache_max);
3112             /* FALLTHROUGH */
3113          case 0: /* no limit */
3114 #  endif /* USER_LIMITS */
3115             /* Here when the limit isn't reached or when limits are compiled
3116              * out; store the chunk.
3117              */
3118             png_set_unknown_chunks(png_ptr, info_ptr,
3119                 &png_ptr->unknown_chunk, 1);
3120             handled = 1;
3121 #  ifdef PNG_USER_LIMITS_SUPPORTED
3122             break;
3123       }
3124 #  endif
3125    }
3126 #  else /* no store support: the chunk must be handled by the user callback */
3127    PNG_UNUSED(info_ptr)
3128 #  endif
3129 
3130    /* Regardless of the error handling below the cached data (if any) can be
3131     * freed now.  Notice that the data is not freed if there is a png_error, but
3132     * it will be freed by destroy_read_struct.
3133     */
3134    if (png_ptr->unknown_chunk.data != NULL)
3135       png_free(png_ptr, png_ptr->unknown_chunk.data);
3136    png_ptr->unknown_chunk.data = NULL;
3137 
3138 #else /* !PNG_READ_UNKNOWN_CHUNKS_SUPPORTED */
3139    /* There is no support to read an unknown chunk, so just skip it. */
3140    png_crc_finish(png_ptr, length);
3141    PNG_UNUSED(info_ptr)
3142    PNG_UNUSED(keep)
3143 #endif /* !READ_UNKNOWN_CHUNKS */
3144 
3145    /* Check for unhandled critical chunks */
3146    if (handled == 0 && PNG_CHUNK_CRITICAL(png_ptr->chunk_name))
3147       png_chunk_error(png_ptr, "unhandled critical chunk");
3148 }
3149 
3150 /* This function is called to verify that a chunk name is valid.
3151  * This function can't have the "critical chunk check" incorporated
3152  * into it, since in the future we will need to be able to call user
3153  * functions to handle unknown critical chunks after we check that
3154  * the chunk name itself is valid.
3155  */
3156 
3157 /* Bit hacking: the test for an invalid byte in the 4 byte chunk name is:
3158  *
3159  * ((c) < 65 || (c) > 122 || ((c) > 90 && (c) < 97))
3160  */
3161 
3162 void /* PRIVATE */
3163 png_check_chunk_name(png_const_structrp png_ptr, const png_uint_32 chunk_name)
3164 {
3165    int i;
3166    png_uint_32 cn=chunk_name;
3167 
3168    png_debug(1, "in png_check_chunk_name");
3169 
3170    for (i=1; i<=4; ++i)
3171    {
3172       int c = cn & 0xff;
3173 
3174       if (c < 65 || c > 122 || (c > 90 && c < 97))
3175          png_chunk_error(png_ptr, "invalid chunk type");
3176 
3177       cn >>= 8;
3178    }
3179 }
3180 
3181 void /* PRIVATE */
3182 png_check_chunk_length(png_const_structrp png_ptr, const png_uint_32 length)
3183 {
3184    png_alloc_size_t limit = PNG_UINT_31_MAX;
3185 
3186 # ifdef PNG_SET_USER_LIMITS_SUPPORTED
3187    if (png_ptr->user_chunk_malloc_max > 0 &&
3188        png_ptr->user_chunk_malloc_max < limit)
3189       limit = png_ptr->user_chunk_malloc_max;
3190 # elif PNG_USER_CHUNK_MALLOC_MAX > 0
3191    if (PNG_USER_CHUNK_MALLOC_MAX < limit)
3192       limit = PNG_USER_CHUNK_MALLOC_MAX;
3193 # endif
3194    if (png_ptr->chunk_name == png_IDAT)
3195    {
3196       png_alloc_size_t idat_limit = PNG_UINT_31_MAX;
3197       size_t row_factor =
3198          (size_t)png_ptr->width
3199          * (size_t)png_ptr->channels
3200          * (png_ptr->bit_depth > 8? 2: 1)
3201          + 1
3202          + (png_ptr->interlaced? 6: 0);
3203       if (png_ptr->height > PNG_UINT_32_MAX/row_factor)
3204          idat_limit = PNG_UINT_31_MAX;
3205       else
3206          idat_limit = png_ptr->height * row_factor;
3207       row_factor = row_factor > 32566? 32566 : row_factor;
3208       idat_limit += 6 + 5*(idat_limit/row_factor+1); /* zlib+deflate overhead */
3209       idat_limit=idat_limit < PNG_UINT_31_MAX? idat_limit : PNG_UINT_31_MAX;
3210       limit = limit < idat_limit? idat_limit : limit;
3211    }
3212 
3213    if (length > limit)
3214    {
3215       png_debug2(0," length = %lu, limit = %lu",
3216          (unsigned long)length,(unsigned long)limit);
3217       png_chunk_error(png_ptr, "chunk data is too large");
3218    }
3219 }
3220 
3221 /* Combines the row recently read in with the existing pixels in the row.  This
3222  * routine takes care of alpha and transparency if requested.  This routine also
3223  * handles the two methods of progressive display of interlaced images,
3224  * depending on the 'display' value; if 'display' is true then the whole row
3225  * (dp) is filled from the start by replicating the available pixels.  If
3226  * 'display' is false only those pixels present in the pass are filled in.
3227  */
3228 void /* PRIVATE */
3229 png_combine_row(png_const_structrp png_ptr, png_bytep dp, int display)
3230 {
3231    unsigned int pixel_depth = png_ptr->transformed_pixel_depth;
3232    png_const_bytep sp = png_ptr->row_buf + 1;
3233    png_alloc_size_t row_width = png_ptr->width;
3234    unsigned int pass = png_ptr->pass;
3235    png_bytep end_ptr = 0;
3236    png_byte end_byte = 0;
3237    unsigned int end_mask;
3238 
3239    png_debug(1, "in png_combine_row");
3240 
3241    /* Added in 1.5.6: it should not be possible to enter this routine until at
3242     * least one row has been read from the PNG data and transformed.
3243     */
3244    if (pixel_depth == 0)
3245       png_error(png_ptr, "internal row logic error");
3246 
3247    /* Added in 1.5.4: the pixel depth should match the information returned by
3248     * any call to png_read_update_info at this point.  Do not continue if we got
3249     * this wrong.
3250     */
3251    if (png_ptr->info_rowbytes != 0 && png_ptr->info_rowbytes !=
3252           PNG_ROWBYTES(pixel_depth, row_width))
3253       png_error(png_ptr, "internal row size calculation error");
3254 
3255    /* Don't expect this to ever happen: */
3256    if (row_width == 0)
3257       png_error(png_ptr, "internal row width error");
3258 
3259    /* Preserve the last byte in cases where only part of it will be overwritten,
3260     * the multiply below may overflow, we don't care because ANSI-C guarantees
3261     * we get the low bits.
3262     */
3263    end_mask = (pixel_depth * row_width) & 7;
3264    if (end_mask != 0)
3265    {
3266       /* end_ptr == NULL is a flag to say do nothing */
3267       end_ptr = dp + PNG_ROWBYTES(pixel_depth, row_width) - 1;
3268       end_byte = *end_ptr;
3269 #     ifdef PNG_READ_PACKSWAP_SUPPORTED
3270       if ((png_ptr->transformations & PNG_PACKSWAP) != 0)
3271          /* little-endian byte */
3272          end_mask = (unsigned int)(0xff << end_mask);
3273 
3274       else /* big-endian byte */
3275 #     endif
3276       end_mask = 0xff >> end_mask;
3277       /* end_mask is now the bits to *keep* from the destination row */
3278    }
3279 
3280    /* For non-interlaced images this reduces to a memcpy(). A memcpy()
3281     * will also happen if interlacing isn't supported or if the application
3282     * does not call png_set_interlace_handling().  In the latter cases the
3283     * caller just gets a sequence of the unexpanded rows from each interlace
3284     * pass.
3285     */
3286 #ifdef PNG_READ_INTERLACING_SUPPORTED
3287    if (png_ptr->interlaced != 0 &&
3288        (png_ptr->transformations & PNG_INTERLACE) != 0 &&
3289        pass < 6 && (display == 0 ||
3290        /* The following copies everything for 'display' on passes 0, 2 and 4. */
3291        (display == 1 && (pass & 1) != 0)))
3292    {
3293       /* Narrow images may have no bits in a pass; the caller should handle
3294        * this, but this test is cheap:
3295        */
3296       if (row_width <= PNG_PASS_START_COL(pass))
3297          return;
3298 
3299       if (pixel_depth < 8)
3300       {
3301          /* For pixel depths up to 4 bpp the 8-pixel mask can be expanded to fit
3302           * into 32 bits, then a single loop over the bytes using the four byte
3303           * values in the 32-bit mask can be used.  For the 'display' option the
3304           * expanded mask may also not require any masking within a byte.  To
3305           * make this work the PACKSWAP option must be taken into account - it
3306           * simply requires the pixels to be reversed in each byte.
3307           *
3308           * The 'regular' case requires a mask for each of the first 6 passes,
3309           * the 'display' case does a copy for the even passes in the range
3310           * 0..6.  This has already been handled in the test above.
3311           *
3312           * The masks are arranged as four bytes with the first byte to use in
3313           * the lowest bits (little-endian) regardless of the order (PACKSWAP or
3314           * not) of the pixels in each byte.
3315           *
3316           * NOTE: the whole of this logic depends on the caller of this function
3317           * only calling it on rows appropriate to the pass.  This function only
3318           * understands the 'x' logic; the 'y' logic is handled by the caller.
3319           *
3320           * The following defines allow generation of compile time constant bit
3321           * masks for each pixel depth and each possibility of swapped or not
3322           * swapped bytes.  Pass 'p' is in the range 0..6; 'x', a pixel index,
3323           * is in the range 0..7; and the result is 1 if the pixel is to be
3324           * copied in the pass, 0 if not.  'S' is for the sparkle method, 'B'
3325           * for the block method.
3326           *
3327           * With some compilers a compile time expression of the general form:
3328           *
3329           *    (shift >= 32) ? (a >> (shift-32)) : (b >> shift)
3330           *
3331           * Produces warnings with values of 'shift' in the range 33 to 63
3332           * because the right hand side of the ?: expression is evaluated by
3333           * the compiler even though it isn't used.  Microsoft Visual C (various
3334           * versions) and the Intel C compiler are known to do this.  To avoid
3335           * this the following macros are used in 1.5.6.  This is a temporary
3336           * solution to avoid destabilizing the code during the release process.
3337           */
3338 #        if PNG_USE_COMPILE_TIME_MASKS
3339 #           define PNG_LSR(x,s) ((x)>>((s) & 0x1f))
3340 #           define PNG_LSL(x,s) ((x)<<((s) & 0x1f))
3341 #        else
3342 #           define PNG_LSR(x,s) ((x)>>(s))
3343 #           define PNG_LSL(x,s) ((x)<<(s))
3344 #        endif
3345 #        define S_COPY(p,x) (((p)<4 ? PNG_LSR(0x80088822,(3-(p))*8+(7-(x))) :\
3346            PNG_LSR(0xaa55ff00,(7-(p))*8+(7-(x)))) & 1)
3347 #        define B_COPY(p,x) (((p)<4 ? PNG_LSR(0xff0fff33,(3-(p))*8+(7-(x))) :\
3348            PNG_LSR(0xff55ff00,(7-(p))*8+(7-(x)))) & 1)
3349 
3350          /* Return a mask for pass 'p' pixel 'x' at depth 'd'.  The mask is
3351           * little endian - the first pixel is at bit 0 - however the extra
3352           * parameter 's' can be set to cause the mask position to be swapped
3353           * within each byte, to match the PNG format.  This is done by XOR of
3354           * the shift with 7, 6 or 4 for bit depths 1, 2 and 4.
3355           */
3356 #        define PIXEL_MASK(p,x,d,s) \
3357             (PNG_LSL(((PNG_LSL(1U,(d)))-1),(((x)*(d))^((s)?8-(d):0))))
3358 
3359          /* Hence generate the appropriate 'block' or 'sparkle' pixel copy mask.
3360           */
3361 #        define S_MASKx(p,x,d,s) (S_COPY(p,x)?PIXEL_MASK(p,x,d,s):0)
3362 #        define B_MASKx(p,x,d,s) (B_COPY(p,x)?PIXEL_MASK(p,x,d,s):0)
3363 
3364          /* Combine 8 of these to get the full mask.  For the 1-bpp and 2-bpp
3365           * cases the result needs replicating, for the 4-bpp case the above
3366           * generates a full 32 bits.
3367           */
3368 #        define MASK_EXPAND(m,d) ((m)*((d)==1?0x01010101:((d)==2?0x00010001:1)))
3369 
3370 #        define S_MASK(p,d,s) MASK_EXPAND(S_MASKx(p,0,d,s) + S_MASKx(p,1,d,s) +\
3371             S_MASKx(p,2,d,s) + S_MASKx(p,3,d,s) + S_MASKx(p,4,d,s) +\
3372             S_MASKx(p,5,d,s) + S_MASKx(p,6,d,s) + S_MASKx(p,7,d,s), d)
3373 
3374 #        define B_MASK(p,d,s) MASK_EXPAND(B_MASKx(p,0,d,s) + B_MASKx(p,1,d,s) +\
3375             B_MASKx(p,2,d,s) + B_MASKx(p,3,d,s) + B_MASKx(p,4,d,s) +\
3376             B_MASKx(p,5,d,s) + B_MASKx(p,6,d,s) + B_MASKx(p,7,d,s), d)
3377 
3378 #if PNG_USE_COMPILE_TIME_MASKS
3379          /* Utility macros to construct all the masks for a depth/swap
3380           * combination.  The 's' parameter says whether the format is PNG
3381           * (big endian bytes) or not.  Only the three odd-numbered passes are
3382           * required for the display/block algorithm.
3383           */
3384 #        define S_MASKS(d,s) { S_MASK(0,d,s), S_MASK(1,d,s), S_MASK(2,d,s),\
3385             S_MASK(3,d,s), S_MASK(4,d,s), S_MASK(5,d,s) }
3386 
3387 #        define B_MASKS(d,s) { B_MASK(1,d,s), B_MASK(3,d,s), B_MASK(5,d,s) }
3388 
3389 #        define DEPTH_INDEX(d) ((d)==1?0:((d)==2?1:2))
3390 
3391          /* Hence the pre-compiled masks indexed by PACKSWAP (or not), depth and
3392           * then pass:
3393           */
3394          static PNG_CONST png_uint_32 row_mask[2/*PACKSWAP*/][3/*depth*/][6] =
3395          {
3396             /* Little-endian byte masks for PACKSWAP */
3397             { S_MASKS(1,0), S_MASKS(2,0), S_MASKS(4,0) },
3398             /* Normal (big-endian byte) masks - PNG format */
3399             { S_MASKS(1,1), S_MASKS(2,1), S_MASKS(4,1) }
3400          };
3401 
3402          /* display_mask has only three entries for the odd passes, so index by
3403           * pass>>1.
3404           */
3405          static PNG_CONST png_uint_32 display_mask[2][3][3] =
3406          {
3407             /* Little-endian byte masks for PACKSWAP */
3408             { B_MASKS(1,0), B_MASKS(2,0), B_MASKS(4,0) },
3409             /* Normal (big-endian byte) masks - PNG format */
3410             { B_MASKS(1,1), B_MASKS(2,1), B_MASKS(4,1) }
3411          };
3412 
3413 #        define MASK(pass,depth,display,png)\
3414             ((display)?display_mask[png][DEPTH_INDEX(depth)][pass>>1]:\
3415                row_mask[png][DEPTH_INDEX(depth)][pass])
3416 
3417 #else /* !PNG_USE_COMPILE_TIME_MASKS */
3418          /* This is the runtime alternative: it seems unlikely that this will
3419           * ever be either smaller or faster than the compile time approach.
3420           */
3421 #        define MASK(pass,depth,display,png)\
3422             ((display)?B_MASK(pass,depth,png):S_MASK(pass,depth,png))
3423 #endif /* !USE_COMPILE_TIME_MASKS */
3424 
3425          /* Use the appropriate mask to copy the required bits.  In some cases
3426           * the byte mask will be 0 or 0xff; optimize these cases.  row_width is
3427           * the number of pixels, but the code copies bytes, so it is necessary
3428           * to special case the end.
3429           */
3430          png_uint_32 pixels_per_byte = 8 / pixel_depth;
3431          png_uint_32 mask;
3432 
3433 #        ifdef PNG_READ_PACKSWAP_SUPPORTED
3434          if ((png_ptr->transformations & PNG_PACKSWAP) != 0)
3435             mask = MASK(pass, pixel_depth, display, 0);
3436 
3437          else
3438 #        endif
3439          mask = MASK(pass, pixel_depth, display, 1);
3440 
3441          for (;;)
3442          {
3443             png_uint_32 m;
3444 
3445             /* It doesn't matter in the following if png_uint_32 has more than
3446              * 32 bits because the high bits always match those in m<<24; it is,
3447              * however, essential to use OR here, not +, because of this.
3448              */
3449             m = mask;
3450             mask = (m >> 8) | (m << 24); /* rotate right to good compilers */
3451             m &= 0xff;
3452 
3453             if (m != 0) /* something to copy */
3454             {
3455                if (m != 0xff)
3456                   *dp = (png_byte)((*dp & ~m) | (*sp & m));
3457                else
3458                   *dp = *sp;
3459             }
3460 
3461             /* NOTE: this may overwrite the last byte with garbage if the image
3462              * is not an exact number of bytes wide; libpng has always done
3463              * this.
3464              */
3465             if (row_width <= pixels_per_byte)
3466                break; /* May need to restore part of the last byte */
3467 
3468             row_width -= pixels_per_byte;
3469             ++dp;
3470             ++sp;
3471          }
3472       }
3473 
3474       else /* pixel_depth >= 8 */
3475       {
3476          unsigned int bytes_to_copy, bytes_to_jump;
3477 
3478          /* Validate the depth - it must be a multiple of 8 */
3479          if (pixel_depth & 7)
3480             png_error(png_ptr, "invalid user transform pixel depth");
3481 
3482          pixel_depth >>= 3; /* now in bytes */
3483          row_width *= pixel_depth;
3484 
3485          /* Regardless of pass number the Adam 7 interlace always results in a
3486           * fixed number of pixels to copy then to skip.  There may be a
3487           * different number of pixels to skip at the start though.
3488           */
3489          {
3490             unsigned int offset = PNG_PASS_START_COL(pass) * pixel_depth;
3491 
3492             row_width -= offset;
3493             dp += offset;
3494             sp += offset;
3495          }
3496 
3497          /* Work out the bytes to copy. */
3498          if (display != 0)
3499          {
3500             /* When doing the 'block' algorithm the pixel in the pass gets
3501              * replicated to adjacent pixels.  This is why the even (0,2,4,6)
3502              * passes are skipped above - the entire expanded row is copied.
3503              */
3504             bytes_to_copy = (1<<((6-pass)>>1)) * pixel_depth;
3505 
3506             /* But don't allow this number to exceed the actual row width. */
3507             if (bytes_to_copy > row_width)
3508                bytes_to_copy = (unsigned int)/*SAFE*/row_width;
3509          }
3510 
3511          else /* normal row; Adam7 only ever gives us one pixel to copy. */
3512             bytes_to_copy = pixel_depth;
3513 
3514          /* In Adam7 there is a constant offset between where the pixels go. */
3515          bytes_to_jump = PNG_PASS_COL_OFFSET(pass) * pixel_depth;
3516 
3517          /* And simply copy these bytes.  Some optimization is possible here,
3518           * depending on the value of 'bytes_to_copy'.  Special case the low
3519           * byte counts, which we know to be frequent.
3520           *
3521           * Notice that these cases all 'return' rather than 'break' - this
3522           * avoids an unnecessary test on whether to restore the last byte
3523           * below.
3524           */
3525          switch (bytes_to_copy)
3526          {
3527             case 1:
3528                for (;;)
3529                {
3530                   *dp = *sp;
3531 
3532                   if (row_width <= bytes_to_jump)
3533                      return;
3534 
3535                   dp += bytes_to_jump;
3536                   sp += bytes_to_jump;
3537                   row_width -= bytes_to_jump;
3538                }
3539 
3540             case 2:
3541                /* There is a possibility of a partial copy at the end here; this
3542                 * slows the code down somewhat.
3543                 */
3544                do
3545                {
3546                   dp[0] = sp[0]; dp[1] = sp[1];
3547 
3548                   if (row_width <= bytes_to_jump)
3549                      return;
3550 
3551                   sp += bytes_to_jump;
3552                   dp += bytes_to_jump;
3553                   row_width -= bytes_to_jump;
3554                }
3555                while (row_width > 1);
3556 
3557                /* And there can only be one byte left at this point: */
3558                *dp = *sp;
3559                return;
3560 
3561             case 3:
3562                /* This can only be the RGB case, so each copy is exactly one
3563                 * pixel and it is not necessary to check for a partial copy.
3564                 */
3565                for (;;)
3566                {
3567                   dp[0] = sp[0]; dp[1] = sp[1]; dp[2] = sp[2];
3568 
3569                   if (row_width <= bytes_to_jump)
3570                      return;
3571 
3572                   sp += bytes_to_jump;
3573                   dp += bytes_to_jump;
3574                   row_width -= bytes_to_jump;
3575                }
3576 
3577             default:
3578 #if PNG_ALIGN_TYPE != PNG_ALIGN_NONE
3579                /* Check for double byte alignment and, if possible, use a
3580                 * 16-bit copy.  Don't attempt this for narrow images - ones that
3581                 * are less than an interlace panel wide.  Don't attempt it for
3582                 * wide bytes_to_copy either - use the memcpy there.
3583                 */
3584                if (bytes_to_copy < 16 /*else use memcpy*/ &&
3585                    png_isaligned(dp, png_uint_16) &&
3586                    png_isaligned(sp, png_uint_16) &&
3587                    bytes_to_copy % (sizeof (png_uint_16)) == 0 &&
3588                    bytes_to_jump % (sizeof (png_uint_16)) == 0)
3589                {
3590                   /* Everything is aligned for png_uint_16 copies, but try for
3591                    * png_uint_32 first.
3592                    */
3593                   if (png_isaligned(dp, png_uint_32) &&
3594                       png_isaligned(sp, png_uint_32) &&
3595                       bytes_to_copy % (sizeof (png_uint_32)) == 0 &&
3596                       bytes_to_jump % (sizeof (png_uint_32)) == 0)
3597                   {
3598                      png_uint_32p dp32 = png_aligncast(png_uint_32p,dp);
3599                      png_const_uint_32p sp32 = png_aligncastconst(
3600                          png_const_uint_32p, sp);
3601                      size_t skip = (bytes_to_jump-bytes_to_copy) /
3602                          (sizeof (png_uint_32));
3603 
3604                      do
3605                      {
3606                         size_t c = bytes_to_copy;
3607                         do
3608                         {
3609                            *dp32++ = *sp32++;
3610                            c -= (sizeof (png_uint_32));
3611                         }
3612                         while (c > 0);
3613 
3614                         if (row_width <= bytes_to_jump)
3615                            return;
3616 
3617                         dp32 += skip;
3618                         sp32 += skip;
3619                         row_width -= bytes_to_jump;
3620                      }
3621                      while (bytes_to_copy <= row_width);
3622 
3623                      /* Get to here when the row_width truncates the final copy.
3624                       * There will be 1-3 bytes left to copy, so don't try the
3625                       * 16-bit loop below.
3626                       */
3627                      dp = (png_bytep)dp32;
3628                      sp = (png_const_bytep)sp32;
3629                      do
3630                         *dp++ = *sp++;
3631                      while (--row_width > 0);
3632                      return;
3633                   }
3634 
3635                   /* Else do it in 16-bit quantities, but only if the size is
3636                    * not too large.
3637                    */
3638                   else
3639                   {
3640                      png_uint_16p dp16 = png_aligncast(png_uint_16p, dp);
3641                      png_const_uint_16p sp16 = png_aligncastconst(
3642                         png_const_uint_16p, sp);
3643                      size_t skip = (bytes_to_jump-bytes_to_copy) /
3644                         (sizeof (png_uint_16));
3645 
3646                      do
3647                      {
3648                         size_t c = bytes_to_copy;
3649                         do
3650                         {
3651                            *dp16++ = *sp16++;
3652                            c -= (sizeof (png_uint_16));
3653                         }
3654                         while (c > 0);
3655 
3656                         if (row_width <= bytes_to_jump)
3657                            return;
3658 
3659                         dp16 += skip;
3660                         sp16 += skip;
3661                         row_width -= bytes_to_jump;
3662                      }
3663                      while (bytes_to_copy <= row_width);
3664 
3665                      /* End of row - 1 byte left, bytes_to_copy > row_width: */
3666                      dp = (png_bytep)dp16;
3667                      sp = (png_const_bytep)sp16;
3668                      do
3669                         *dp++ = *sp++;
3670                      while (--row_width > 0);
3671                      return;
3672                   }
3673                }
3674 #endif /* ALIGN_TYPE code */
3675 
3676                /* The true default - use a memcpy: */
3677                for (;;)
3678                {
3679                   memcpy(dp, sp, bytes_to_copy);
3680 
3681                   if (row_width <= bytes_to_jump)
3682                      return;
3683 
3684                   sp += bytes_to_jump;
3685                   dp += bytes_to_jump;
3686                   row_width -= bytes_to_jump;
3687                   if (bytes_to_copy > row_width)
3688                      bytes_to_copy = (unsigned int)/*SAFE*/row_width;
3689                }
3690          }
3691 
3692          /* NOT REACHED*/
3693       } /* pixel_depth >= 8 */
3694 
3695       /* Here if pixel_depth < 8 to check 'end_ptr' below. */
3696    }
3697    else
3698 #endif /* READ_INTERLACING */
3699 
3700    /* If here then the switch above wasn't used so just memcpy the whole row
3701     * from the temporary row buffer (notice that this overwrites the end of the
3702     * destination row if it is a partial byte.)
3703     */
3704    memcpy(dp, sp, PNG_ROWBYTES(pixel_depth, row_width));
3705 
3706    /* Restore the overwritten bits from the last byte if necessary. */
3707    if (end_ptr != NULL)
3708       *end_ptr = (png_byte)((end_byte & end_mask) | (*end_ptr & ~end_mask));
3709 }
3710 
3711 #ifdef PNG_READ_INTERLACING_SUPPORTED
3712 void /* PRIVATE */
3713 png_do_read_interlace(png_row_infop row_info, png_bytep row, int pass,
3714     png_uint_32 transformations /* Because these may affect the byte layout */)
3715 {
3716    /* Arrays to facilitate easy interlacing - use pass (0 - 6) as index */
3717    /* Offset to next interlace block */
3718    static PNG_CONST unsigned int png_pass_inc[7] = {8, 8, 4, 4, 2, 2, 1};
3719 
3720    png_debug(1, "in png_do_read_interlace");
3721    if (row != NULL && row_info != NULL)
3722    {
3723       png_uint_32 final_width;
3724 
3725       final_width = row_info->width * png_pass_inc[pass];
3726 
3727       switch (row_info->pixel_depth)
3728       {
3729          case 1:
3730          {
3731             png_bytep sp = row + (size_t)((row_info->width - 1) >> 3);
3732             png_bytep dp = row + (size_t)((final_width - 1) >> 3);
3733             unsigned int sshift, dshift;
3734             unsigned int s_start, s_end;
3735             int s_inc;
3736             int jstop = (int)png_pass_inc[pass];
3737             png_byte v;
3738             png_uint_32 i;
3739             int j;
3740 
3741 #ifdef PNG_READ_PACKSWAP_SUPPORTED
3742             if ((transformations & PNG_PACKSWAP) != 0)
3743             {
3744                 sshift = ((row_info->width + 7) & 0x07);
3745                 dshift = ((final_width + 7) & 0x07);
3746                 s_start = 7;
3747                 s_end = 0;
3748                 s_inc = -1;
3749             }
3750 
3751             else
3752 #endif
3753             {
3754                 sshift = 7 - ((row_info->width + 7) & 0x07);
3755                 dshift = 7 - ((final_width + 7) & 0x07);
3756                 s_start = 0;
3757                 s_end = 7;
3758                 s_inc = 1;
3759             }
3760 
3761             for (i = 0; i < row_info->width; i++)
3762             {
3763                v = (png_byte)((*sp >> sshift) & 0x01);
3764                for (j = 0; j < jstop; j++)
3765                {
3766                   unsigned int tmp = *dp & (0x7f7f >> (7 - dshift));
3767                   tmp |= (unsigned int)(v << dshift);
3768                   *dp = (png_byte)(tmp & 0xff);
3769 
3770                   if (dshift == s_end)
3771                   {
3772                      dshift = s_start;
3773                      dp--;
3774                   }
3775 
3776                   else
3777                      dshift = (unsigned int)((int)dshift + s_inc);
3778                }
3779 
3780                if (sshift == s_end)
3781                {
3782                   sshift = s_start;
3783                   sp--;
3784                }
3785 
3786                else
3787                   sshift = (unsigned int)((int)sshift + s_inc);
3788             }
3789             break;
3790          }
3791 
3792          case 2:
3793          {
3794             png_bytep sp = row + (png_uint_32)((row_info->width - 1) >> 2);
3795             png_bytep dp = row + (png_uint_32)((final_width - 1) >> 2);
3796             unsigned int sshift, dshift;
3797             unsigned int s_start, s_end;
3798             int s_inc;
3799             int jstop = (int)png_pass_inc[pass];
3800             png_uint_32 i;
3801 
3802 #ifdef PNG_READ_PACKSWAP_SUPPORTED
3803             if ((transformations & PNG_PACKSWAP) != 0)
3804             {
3805                sshift = (((row_info->width + 3) & 0x03) << 1);
3806                dshift = (((final_width + 3) & 0x03) << 1);
3807                s_start = 6;
3808                s_end = 0;
3809                s_inc = -2;
3810             }
3811 
3812             else
3813 #endif
3814             {
3815                sshift = ((3 - ((row_info->width + 3) & 0x03)) << 1);
3816                dshift = ((3 - ((final_width + 3) & 0x03)) << 1);
3817                s_start = 0;
3818                s_end = 6;
3819                s_inc = 2;
3820             }
3821 
3822             for (i = 0; i < row_info->width; i++)
3823             {
3824                png_byte v;
3825                int j;
3826 
3827                v = (png_byte)((*sp >> sshift) & 0x03);
3828                for (j = 0; j < jstop; j++)
3829                {
3830                   unsigned int tmp = *dp & (0x3f3f >> (6 - dshift));
3831                   tmp |= (unsigned int)(v << dshift);
3832                   *dp = (png_byte)(tmp & 0xff);
3833 
3834                   if (dshift == s_end)
3835                   {
3836                      dshift = s_start;
3837                      dp--;
3838                   }
3839 
3840                   else
3841                      dshift = (unsigned int)((int)dshift + s_inc);
3842                }
3843 
3844                if (sshift == s_end)
3845                {
3846                   sshift = s_start;
3847                   sp--;
3848                }
3849 
3850                else
3851                   sshift = (unsigned int)((int)sshift + s_inc);
3852             }
3853             break;
3854          }
3855 
3856          case 4:
3857          {
3858             png_bytep sp = row + (size_t)((row_info->width - 1) >> 1);
3859             png_bytep dp = row + (size_t)((final_width - 1) >> 1);
3860             unsigned int sshift, dshift;
3861             unsigned int s_start, s_end;
3862             int s_inc;
3863             png_uint_32 i;
3864             int jstop = (int)png_pass_inc[pass];
3865 
3866 #ifdef PNG_READ_PACKSWAP_SUPPORTED
3867             if ((transformations & PNG_PACKSWAP) != 0)
3868             {
3869                sshift = (((row_info->width + 1) & 0x01) << 2);
3870                dshift = (((final_width + 1) & 0x01) << 2);
3871                s_start = 4;
3872                s_end = 0;
3873                s_inc = -4;
3874             }
3875 
3876             else
3877 #endif
3878             {
3879                sshift = ((1 - ((row_info->width + 1) & 0x01)) << 2);
3880                dshift = ((1 - ((final_width + 1) & 0x01)) << 2);
3881                s_start = 0;
3882                s_end = 4;
3883                s_inc = 4;
3884             }
3885 
3886             for (i = 0; i < row_info->width; i++)
3887             {
3888                png_byte v = (png_byte)((*sp >> sshift) & 0x0f);
3889                int j;
3890 
3891                for (j = 0; j < jstop; j++)
3892                {
3893                   unsigned int tmp = *dp & (0xf0f >> (4 - dshift));
3894                   tmp |= (unsigned int)(v << dshift);
3895                   *dp = (png_byte)(tmp & 0xff);
3896 
3897                   if (dshift == s_end)
3898                   {
3899                      dshift = s_start;
3900                      dp--;
3901                   }
3902 
3903                   else
3904                      dshift = (unsigned int)((int)dshift + s_inc);
3905                }
3906 
3907                if (sshift == s_end)
3908                {
3909                   sshift = s_start;
3910                   sp--;
3911                }
3912 
3913                else
3914                   sshift = (unsigned int)((int)sshift + s_inc);
3915             }
3916             break;
3917          }
3918 
3919          default:
3920          {
3921             size_t pixel_bytes = (row_info->pixel_depth >> 3);
3922 
3923             png_bytep sp = row + (size_t)(row_info->width - 1)
3924                 * pixel_bytes;
3925 
3926             png_bytep dp = row + (size_t)(final_width - 1) * pixel_bytes;
3927 
3928             int jstop = (int)png_pass_inc[pass];
3929             png_uint_32 i;
3930 
3931             for (i = 0; i < row_info->width; i++)
3932             {
3933                png_byte v[8]; /* SAFE; pixel_depth does not exceed 64 */
3934                int j;
3935 
3936                memcpy(v, sp, pixel_bytes);
3937 
3938                for (j = 0; j < jstop; j++)
3939                {
3940                   memcpy(dp, v, pixel_bytes);
3941                   dp -= pixel_bytes;
3942                }
3943 
3944                sp -= pixel_bytes;
3945             }
3946             break;
3947          }
3948       }
3949 
3950       row_info->width = final_width;
3951       row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth, final_width);
3952    }
3953 #ifndef PNG_READ_PACKSWAP_SUPPORTED
3954    PNG_UNUSED(transformations)  /* Silence compiler warning */
3955 #endif
3956 }
3957 #endif /* READ_INTERLACING */
3958 
3959 static void
3960 png_read_filter_row_sub(png_row_infop row_info, png_bytep row,
3961     png_const_bytep prev_row)
3962 {
3963    size_t i;
3964    size_t istop = row_info->rowbytes;
3965    unsigned int bpp = (row_info->pixel_depth + 7) >> 3;
3966    png_bytep rp = row + bpp;
3967 
3968    PNG_UNUSED(prev_row)
3969 
3970    for (i = bpp; i < istop; i++)
3971    {
3972       *rp = (png_byte)(((int)(*rp) + (int)(*(rp-bpp))) & 0xff);
3973       rp++;
3974    }
3975 }
3976 
3977 static void
3978 png_read_filter_row_up(png_row_infop row_info, png_bytep row,
3979     png_const_bytep prev_row)
3980 {
3981    size_t i;
3982    size_t istop = row_info->rowbytes;
3983    png_bytep rp = row;
3984    png_const_bytep pp = prev_row;
3985 
3986    for (i = 0; i < istop; i++)
3987    {
3988       *rp = (png_byte)(((int)(*rp) + (int)(*pp++)) & 0xff);
3989       rp++;
3990    }
3991 }
3992 
3993 static void
3994 png_read_filter_row_avg(png_row_infop row_info, png_bytep row,
3995     png_const_bytep prev_row)
3996 {
3997    size_t i;
3998    png_bytep rp = row;
3999    png_const_bytep pp = prev_row;
4000    unsigned int bpp = (row_info->pixel_depth + 7) >> 3;
4001    size_t istop = row_info->rowbytes - bpp;
4002 
4003    for (i = 0; i < bpp; i++)
4004    {
4005       *rp = (png_byte)(((int)(*rp) +
4006          ((int)(*pp++) / 2 )) & 0xff);
4007 
4008       rp++;
4009    }
4010 
4011    for (i = 0; i < istop; i++)
4012    {
4013       *rp = (png_byte)(((int)(*rp) +
4014          (int)(*pp++ + *(rp-bpp)) / 2 ) & 0xff);
4015 
4016       rp++;
4017    }
4018 }
4019 
4020 static void
4021 png_read_filter_row_paeth_1byte_pixel(png_row_infop row_info, png_bytep row,
4022     png_const_bytep prev_row)
4023 {
4024    png_bytep rp_end = row + row_info->rowbytes;
4025    int a, c;
4026 
4027    /* First pixel/byte */
4028    c = *prev_row++;
4029    a = *row + c;
4030    *row++ = (png_byte)a;
4031 
4032    /* Remainder */
4033    while (row < rp_end)
4034    {
4035       int b, pa, pb, pc, p;
4036 
4037       a &= 0xff; /* From previous iteration or start */
4038       b = *prev_row++;
4039 
4040       p = b - c;
4041       pc = a - c;
4042 
4043 #ifdef PNG_USE_ABS
4044       pa = abs(p);
4045       pb = abs(pc);
4046       pc = abs(p + pc);
4047 #else
4048       pa = p < 0 ? -p : p;
4049       pb = pc < 0 ? -pc : pc;
4050       pc = (p + pc) < 0 ? -(p + pc) : p + pc;
4051 #endif
4052 
4053       /* Find the best predictor, the least of pa, pb, pc favoring the earlier
4054        * ones in the case of a tie.
4055        */
4056       if (pb < pa)
4057       {
4058          pa = pb; a = b;
4059       }
4060       if (pc < pa) a = c;
4061 
4062       /* Calculate the current pixel in a, and move the previous row pixel to c
4063        * for the next time round the loop
4064        */
4065       c = b;
4066       a += *row;
4067       *row++ = (png_byte)a;
4068    }
4069 }
4070 
4071 static void
4072 png_read_filter_row_paeth_multibyte_pixel(png_row_infop row_info, png_bytep row,
4073     png_const_bytep prev_row)
4074 {
4075    unsigned int bpp = (row_info->pixel_depth + 7) >> 3;
4076    png_bytep rp_end = row + bpp;
4077 
4078    /* Process the first pixel in the row completely (this is the same as 'up'
4079     * because there is only one candidate predictor for the first row).
4080     */
4081    while (row < rp_end)
4082    {
4083       int a = *row + *prev_row++;
4084       *row++ = (png_byte)a;
4085    }
4086 
4087    /* Remainder */
4088    rp_end = rp_end + (row_info->rowbytes - bpp);
4089 
4090    while (row < rp_end)
4091    {
4092       int a, b, c, pa, pb, pc, p;
4093 
4094       c = *(prev_row - bpp);
4095       a = *(row - bpp);
4096       b = *prev_row++;
4097 
4098       p = b - c;
4099       pc = a - c;
4100 
4101 #ifdef PNG_USE_ABS
4102       pa = abs(p);
4103       pb = abs(pc);
4104       pc = abs(p + pc);
4105 #else
4106       pa = p < 0 ? -p : p;
4107       pb = pc < 0 ? -pc : pc;
4108       pc = (p + pc) < 0 ? -(p + pc) : p + pc;
4109 #endif
4110 
4111       if (pb < pa)
4112       {
4113          pa = pb; a = b;
4114       }
4115       if (pc < pa) a = c;
4116 
4117       a += *row;
4118       *row++ = (png_byte)a;
4119    }
4120 }
4121 
4122 static void
4123 png_init_filter_functions(png_structrp pp)
4124    /* This function is called once for every PNG image (except for PNG images
4125     * that only use PNG_FILTER_VALUE_NONE for all rows) to set the
4126     * implementations required to reverse the filtering of PNG rows.  Reversing
4127     * the filter is the first transformation performed on the row data.  It is
4128     * performed in place, therefore an implementation can be selected based on
4129     * the image pixel format.  If the implementation depends on image width then
4130     * take care to ensure that it works correctly if the image is interlaced -
4131     * interlacing causes the actual row width to vary.
4132     */
4133 {
4134    unsigned int bpp = (pp->pixel_depth + 7) >> 3;
4135 
4136    pp->read_filter[PNG_FILTER_VALUE_SUB-1] = png_read_filter_row_sub;
4137    pp->read_filter[PNG_FILTER_VALUE_UP-1] = png_read_filter_row_up;
4138    pp->read_filter[PNG_FILTER_VALUE_AVG-1] = png_read_filter_row_avg;
4139    if (bpp == 1)
4140       pp->read_filter[PNG_FILTER_VALUE_PAETH-1] =
4141          png_read_filter_row_paeth_1byte_pixel;
4142    else
4143       pp->read_filter[PNG_FILTER_VALUE_PAETH-1] =
4144          png_read_filter_row_paeth_multibyte_pixel;
4145 
4146 #ifdef PNG_FILTER_OPTIMIZATIONS
4147    /* To use this define PNG_FILTER_OPTIMIZATIONS as the name of a function to
4148     * call to install hardware optimizations for the above functions; simply
4149     * replace whatever elements of the pp->read_filter[] array with a hardware
4150     * specific (or, for that matter, generic) optimization.
4151     *
4152     * To see an example of this examine what configure.ac does when
4153     * --enable-arm-neon is specified on the command line.
4154     */
4155    PNG_FILTER_OPTIMIZATIONS(pp, bpp);
4156 #endif
4157 }
4158 
4159 void /* PRIVATE */
4160 png_read_filter_row(png_structrp pp, png_row_infop row_info, png_bytep row,
4161     png_const_bytep prev_row, int filter)
4162 {
4163    /* OPTIMIZATION: DO NOT MODIFY THIS FUNCTION, instead #define
4164     * PNG_FILTER_OPTIMIZATIONS to a function that overrides the generic
4165     * implementations.  See png_init_filter_functions above.
4166     */
4167    if (filter > PNG_FILTER_VALUE_NONE && filter < PNG_FILTER_VALUE_LAST)
4168    {
4169       if (pp->read_filter[0] == NULL)
4170          png_init_filter_functions(pp);
4171 
4172       pp->read_filter[filter-1](row_info, row, prev_row);
4173    }
4174 }
4175 
4176 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
4177 void /* PRIVATE */
4178 png_read_IDAT_data(png_structrp png_ptr, png_bytep output,
4179     png_alloc_size_t avail_out)
4180 {
4181    /* Loop reading IDATs and decompressing the result into output[avail_out] */
4182    png_ptr->zstream.next_out = output;
4183    png_ptr->zstream.avail_out = 0; /* safety: set below */
4184 
4185    if (output == NULL)
4186       avail_out = 0;
4187 
4188    do
4189    {
4190       int ret;
4191       png_byte tmpbuf[PNG_INFLATE_BUF_SIZE];
4192 
4193       if (png_ptr->zstream.avail_in == 0)
4194       {
4195          uInt avail_in;
4196          png_bytep buffer;
4197 
4198          while (png_ptr->idat_size == 0)
4199          {
4200             png_crc_finish(png_ptr, 0);
4201 
4202             png_ptr->idat_size = png_read_chunk_header(png_ptr);
4203             /* This is an error even in the 'check' case because the code just
4204              * consumed a non-IDAT header.
4205              */
4206             if (png_ptr->chunk_name != png_IDAT)
4207                png_error(png_ptr, "Not enough image data");
4208          }
4209 
4210          avail_in = png_ptr->IDAT_read_size;
4211 
4212          if (avail_in > png_ptr->idat_size)
4213             avail_in = (uInt)png_ptr->idat_size;
4214 
4215          /* A PNG with a gradually increasing IDAT size will defeat this attempt
4216           * to minimize memory usage by causing lots of re-allocs, but
4217           * realistically doing IDAT_read_size re-allocs is not likely to be a
4218           * big problem.
4219           */
4220          buffer = png_read_buffer(png_ptr, avail_in, 0/*error*/);
4221 
4222          png_crc_read(png_ptr, buffer, avail_in);
4223          png_ptr->idat_size -= avail_in;
4224 
4225          png_ptr->zstream.next_in = buffer;
4226          png_ptr->zstream.avail_in = avail_in;
4227       }
4228 
4229       /* And set up the output side. */
4230       if (output != NULL) /* standard read */
4231       {
4232          uInt out = ZLIB_IO_MAX;
4233 
4234          if (out > avail_out)
4235             out = (uInt)avail_out;
4236 
4237          avail_out -= out;
4238          png_ptr->zstream.avail_out = out;
4239       }
4240 
4241       else /* after last row, checking for end */
4242       {
4243          png_ptr->zstream.next_out = tmpbuf;
4244          png_ptr->zstream.avail_out = (sizeof tmpbuf);
4245       }
4246 
4247       /* Use NO_FLUSH; this gives zlib the maximum opportunity to optimize the
4248        * process.  If the LZ stream is truncated the sequential reader will
4249        * terminally damage the stream, above, by reading the chunk header of the
4250        * following chunk (it then exits with png_error).
4251        *
4252        * TODO: deal more elegantly with truncated IDAT lists.
4253        */
4254       ret = PNG_INFLATE(png_ptr, Z_NO_FLUSH);
4255 
4256       /* Take the unconsumed output back. */
4257       if (output != NULL)
4258          avail_out += png_ptr->zstream.avail_out;
4259 
4260       else /* avail_out counts the extra bytes */
4261          avail_out += (sizeof tmpbuf) - png_ptr->zstream.avail_out;
4262 
4263       png_ptr->zstream.avail_out = 0;
4264 
4265       if (ret == Z_STREAM_END)
4266       {
4267          /* Do this for safety; we won't read any more into this row. */
4268          png_ptr->zstream.next_out = NULL;
4269 
4270          png_ptr->mode |= PNG_AFTER_IDAT;
4271          png_ptr->flags |= PNG_FLAG_ZSTREAM_ENDED;
4272 
4273          if (png_ptr->zstream.avail_in > 0 || png_ptr->idat_size > 0)
4274             png_chunk_benign_error(png_ptr, "Extra compressed data");
4275          break;
4276       }
4277 
4278       if (ret != Z_OK)
4279       {
4280          png_zstream_error(png_ptr, ret);
4281 
4282          if (output != NULL)
4283             png_chunk_error(png_ptr, png_ptr->zstream.msg);
4284 
4285          else /* checking */
4286          {
4287             png_chunk_benign_error(png_ptr, png_ptr->zstream.msg);
4288             return;
4289          }
4290       }
4291    } while (avail_out > 0);
4292 
4293    if (avail_out > 0)
4294    {
4295       /* The stream ended before the image; this is the same as too few IDATs so
4296        * should be handled the same way.
4297        */
4298       if (output != NULL)
4299          png_error(png_ptr, "Not enough image data");
4300 
4301       else /* the deflate stream contained extra data */
4302          png_chunk_benign_error(png_ptr, "Too much image data");
4303    }
4304 }
4305 
4306 void /* PRIVATE */
4307 png_read_finish_IDAT(png_structrp png_ptr)
4308 {
4309    /* We don't need any more data and the stream should have ended, however the
4310     * LZ end code may actually not have been processed.  In this case we must
4311     * read it otherwise stray unread IDAT data or, more likely, an IDAT chunk
4312     * may still remain to be consumed.
4313     */
4314    if ((png_ptr->flags & PNG_FLAG_ZSTREAM_ENDED) == 0)
4315    {
4316       /* The NULL causes png_read_IDAT_data to swallow any remaining bytes in
4317        * the compressed stream, but the stream may be damaged too, so even after
4318        * this call we may need to terminate the zstream ownership.
4319        */
4320       png_read_IDAT_data(png_ptr, NULL, 0);
4321       png_ptr->zstream.next_out = NULL; /* safety */
4322 
4323       /* Now clear everything out for safety; the following may not have been
4324        * done.
4325        */
4326       if ((png_ptr->flags & PNG_FLAG_ZSTREAM_ENDED) == 0)
4327       {
4328          png_ptr->mode |= PNG_AFTER_IDAT;
4329          png_ptr->flags |= PNG_FLAG_ZSTREAM_ENDED;
4330       }
4331    }
4332 
4333    /* If the zstream has not been released do it now *and* terminate the reading
4334     * of the final IDAT chunk.
4335     */
4336    if (png_ptr->zowner == png_IDAT)
4337    {
4338       /* Always do this; the pointers otherwise point into the read buffer. */
4339       png_ptr->zstream.next_in = NULL;
4340       png_ptr->zstream.avail_in = 0;
4341 
4342       /* Now we no longer own the zstream. */
4343       png_ptr->zowner = 0;
4344 
4345       /* The slightly weird semantics of the sequential IDAT reading is that we
4346        * are always in or at the end of an IDAT chunk, so we always need to do a
4347        * crc_finish here.  If idat_size is non-zero we also need to read the
4348        * spurious bytes at the end of the chunk now.
4349        */
4350       (void)png_crc_finish(png_ptr, png_ptr->idat_size);
4351    }
4352 }
4353 
4354 void /* PRIVATE */
4355 png_read_finish_row(png_structrp png_ptr)
4356 {
4357    /* Arrays to facilitate easy interlacing - use pass (0 - 6) as index */
4358 
4359    /* Start of interlace block */
4360    static PNG_CONST png_byte png_pass_start[7] = {0, 4, 0, 2, 0, 1, 0};
4361 
4362    /* Offset to next interlace block */
4363    static PNG_CONST png_byte png_pass_inc[7] = {8, 8, 4, 4, 2, 2, 1};
4364 
4365    /* Start of interlace block in the y direction */
4366    static PNG_CONST png_byte png_pass_ystart[7] = {0, 0, 4, 0, 2, 0, 1};
4367 
4368    /* Offset to next interlace block in the y direction */
4369    static PNG_CONST png_byte png_pass_yinc[7] = {8, 8, 8, 4, 4, 2, 2};
4370 
4371    png_debug(1, "in png_read_finish_row");
4372    png_ptr->row_number++;
4373    if (png_ptr->row_number < png_ptr->num_rows)
4374       return;
4375 
4376    if (png_ptr->interlaced != 0)
4377    {
4378       png_ptr->row_number = 0;
4379 
4380       /* TO DO: don't do this if prev_row isn't needed (requires
4381        * read-ahead of the next row's filter byte.
4382        */
4383       memset(png_ptr->prev_row, 0, png_ptr->rowbytes + 1);
4384 
4385       do
4386       {
4387          png_ptr->pass++;
4388 
4389          if (png_ptr->pass >= 7)
4390             break;
4391 
4392          png_ptr->iwidth = (png_ptr->width +
4393             png_pass_inc[png_ptr->pass] - 1 -
4394             png_pass_start[png_ptr->pass]) /
4395             png_pass_inc[png_ptr->pass];
4396 
4397          if ((png_ptr->transformations & PNG_INTERLACE) == 0)
4398          {
4399             png_ptr->num_rows = (png_ptr->height +
4400                 png_pass_yinc[png_ptr->pass] - 1 -
4401                 png_pass_ystart[png_ptr->pass]) /
4402                 png_pass_yinc[png_ptr->pass];
4403          }
4404 
4405          else  /* if (png_ptr->transformations & PNG_INTERLACE) */
4406             break; /* libpng deinterlacing sees every row */
4407 
4408       } while (png_ptr->num_rows == 0 || png_ptr->iwidth == 0);
4409 
4410       if (png_ptr->pass < 7)
4411          return;
4412    }
4413 
4414    /* Here after at the end of the last row of the last pass. */
4415    png_read_finish_IDAT(png_ptr);
4416 }
4417 #endif /* SEQUENTIAL_READ */
4418 
4419 void /* PRIVATE */
4420 png_read_start_row(png_structrp png_ptr)
4421 {
4422    /* Arrays to facilitate easy interlacing - use pass (0 - 6) as index */
4423 
4424    /* Start of interlace block */
4425    static PNG_CONST png_byte png_pass_start[7] = {0, 4, 0, 2, 0, 1, 0};
4426 
4427    /* Offset to next interlace block */
4428    static PNG_CONST png_byte png_pass_inc[7] = {8, 8, 4, 4, 2, 2, 1};
4429 
4430    /* Start of interlace block in the y direction */
4431    static PNG_CONST png_byte png_pass_ystart[7] = {0, 0, 4, 0, 2, 0, 1};
4432 
4433    /* Offset to next interlace block in the y direction */
4434    static PNG_CONST png_byte png_pass_yinc[7] = {8, 8, 8, 4, 4, 2, 2};
4435 
4436    unsigned int max_pixel_depth;
4437    size_t row_bytes;
4438 
4439    png_debug(1, "in png_read_start_row");
4440 
4441 #ifdef PNG_READ_TRANSFORMS_SUPPORTED
4442    png_init_read_transformations(png_ptr);
4443 #endif
4444    if (png_ptr->interlaced != 0)
4445    {
4446       if ((png_ptr->transformations & PNG_INTERLACE) == 0)
4447          png_ptr->num_rows = (png_ptr->height + png_pass_yinc[0] - 1 -
4448              png_pass_ystart[0]) / png_pass_yinc[0];
4449 
4450       else
4451          png_ptr->num_rows = png_ptr->height;
4452 
4453       png_ptr->iwidth = (png_ptr->width +
4454           png_pass_inc[png_ptr->pass] - 1 -
4455           png_pass_start[png_ptr->pass]) /
4456           png_pass_inc[png_ptr->pass];
4457    }
4458 
4459    else
4460    {
4461       png_ptr->num_rows = png_ptr->height;
4462       png_ptr->iwidth = png_ptr->width;
4463    }
4464 
4465    max_pixel_depth = (unsigned int)png_ptr->pixel_depth;
4466 
4467    /* WARNING: * png_read_transform_info (pngrtran.c) performs a simpler set of
4468     * calculations to calculate the final pixel depth, then
4469     * png_do_read_transforms actually does the transforms.  This means that the
4470     * code which effectively calculates this value is actually repeated in three
4471     * separate places.  They must all match.  Innocent changes to the order of
4472     * transformations can and will break libpng in a way that causes memory
4473     * overwrites.
4474     *
4475     * TODO: fix this.
4476     */
4477 #ifdef PNG_READ_PACK_SUPPORTED
4478    if ((png_ptr->transformations & PNG_PACK) != 0 && png_ptr->bit_depth < 8)
4479       max_pixel_depth = 8;
4480 #endif
4481 
4482 #ifdef PNG_READ_EXPAND_SUPPORTED
4483    if ((png_ptr->transformations & PNG_EXPAND) != 0)
4484    {
4485       if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
4486       {
4487          if (png_ptr->num_trans != 0)
4488             max_pixel_depth = 32;
4489 
4490          else
4491             max_pixel_depth = 24;
4492       }
4493 
4494       else if (png_ptr->color_type == PNG_COLOR_TYPE_GRAY)
4495       {
4496          if (max_pixel_depth < 8)
4497             max_pixel_depth = 8;
4498 
4499          if (png_ptr->num_trans != 0)
4500             max_pixel_depth *= 2;
4501       }
4502 
4503       else if (png_ptr->color_type == PNG_COLOR_TYPE_RGB)
4504       {
4505          if (png_ptr->num_trans != 0)
4506          {
4507             max_pixel_depth *= 4;
4508             max_pixel_depth /= 3;
4509          }
4510       }
4511    }
4512 #endif
4513 
4514 #ifdef PNG_READ_EXPAND_16_SUPPORTED
4515    if ((png_ptr->transformations & PNG_EXPAND_16) != 0)
4516    {
4517 #  ifdef PNG_READ_EXPAND_SUPPORTED
4518       /* In fact it is an error if it isn't supported, but checking is
4519        * the safe way.
4520        */
4521       if ((png_ptr->transformations & PNG_EXPAND) != 0)
4522       {
4523          if (png_ptr->bit_depth < 16)
4524             max_pixel_depth *= 2;
4525       }
4526       else
4527 #  endif
4528       png_ptr->transformations &= ~PNG_EXPAND_16;
4529    }
4530 #endif
4531 
4532 #ifdef PNG_READ_FILLER_SUPPORTED
4533    if ((png_ptr->transformations & (PNG_FILLER)) != 0)
4534    {
4535       if (png_ptr->color_type == PNG_COLOR_TYPE_GRAY)
4536       {
4537          if (max_pixel_depth <= 8)
4538             max_pixel_depth = 16;
4539 
4540          else
4541             max_pixel_depth = 32;
4542       }
4543 
4544       else if (png_ptr->color_type == PNG_COLOR_TYPE_RGB ||
4545          png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
4546       {
4547          if (max_pixel_depth <= 32)
4548             max_pixel_depth = 32;
4549 
4550          else
4551             max_pixel_depth = 64;
4552       }
4553    }
4554 #endif
4555 
4556 #ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
4557    if ((png_ptr->transformations & PNG_GRAY_TO_RGB) != 0)
4558    {
4559       if (
4560 #ifdef PNG_READ_EXPAND_SUPPORTED
4561           (png_ptr->num_trans != 0 &&
4562           (png_ptr->transformations & PNG_EXPAND) != 0) ||
4563 #endif
4564 #ifdef PNG_READ_FILLER_SUPPORTED
4565           (png_ptr->transformations & (PNG_FILLER)) != 0 ||
4566 #endif
4567           png_ptr->color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
4568       {
4569          if (max_pixel_depth <= 16)
4570             max_pixel_depth = 32;
4571 
4572          else
4573             max_pixel_depth = 64;
4574       }
4575 
4576       else
4577       {
4578          if (max_pixel_depth <= 8)
4579          {
4580             if (png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
4581                max_pixel_depth = 32;
4582 
4583             else
4584                max_pixel_depth = 24;
4585          }
4586 
4587          else if (png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
4588             max_pixel_depth = 64;
4589 
4590          else
4591             max_pixel_depth = 48;
4592       }
4593    }
4594 #endif
4595 
4596 #if defined(PNG_READ_USER_TRANSFORM_SUPPORTED) && \
4597 defined(PNG_USER_TRANSFORM_PTR_SUPPORTED)
4598    if ((png_ptr->transformations & PNG_USER_TRANSFORM) != 0)
4599    {
4600       unsigned int user_pixel_depth = png_ptr->user_transform_depth *
4601          png_ptr->user_transform_channels;
4602 
4603       if (user_pixel_depth > max_pixel_depth)
4604          max_pixel_depth = user_pixel_depth;
4605    }
4606 #endif
4607 
4608    /* This value is stored in png_struct and double checked in the row read
4609     * code.
4610     */
4611    png_ptr->maximum_pixel_depth = (png_byte)max_pixel_depth;
4612    png_ptr->transformed_pixel_depth = 0; /* calculated on demand */
4613 
4614    /* Align the width on the next larger 8 pixels.  Mainly used
4615     * for interlacing
4616     */
4617    row_bytes = ((png_ptr->width + 7) & ~((png_uint_32)7));
4618    /* Calculate the maximum bytes needed, adding a byte and a pixel
4619     * for safety's sake
4620     */
4621    row_bytes = PNG_ROWBYTES(max_pixel_depth, row_bytes) +
4622        1 + ((max_pixel_depth + 7) >> 3U);
4623 
4624 #ifdef PNG_MAX_MALLOC_64K
4625    if (row_bytes > (png_uint_32)65536L)
4626       png_error(png_ptr, "This image requires a row greater than 64KB");
4627 #endif
4628 
4629    if (row_bytes + 48 > png_ptr->old_big_row_buf_size)
4630    {
4631       png_free(png_ptr, png_ptr->big_row_buf);
4632       png_free(png_ptr, png_ptr->big_prev_row);
4633 
4634       if (png_ptr->interlaced != 0)
4635          png_ptr->big_row_buf = (png_bytep)png_calloc(png_ptr,
4636              row_bytes + 48);
4637 
4638       else
4639          png_ptr->big_row_buf = (png_bytep)png_malloc(png_ptr, row_bytes + 48);
4640 
4641       png_ptr->big_prev_row = (png_bytep)png_malloc(png_ptr, row_bytes + 48);
4642 
4643 #ifdef PNG_ALIGNED_MEMORY_SUPPORTED
4644       /* Use 16-byte aligned memory for row_buf with at least 16 bytes
4645        * of padding before and after row_buf; treat prev_row similarly.
4646        * NOTE: the alignment is to the start of the pixels, one beyond the start
4647        * of the buffer, because of the filter byte.  Prior to libpng 1.5.6 this
4648        * was incorrect; the filter byte was aligned, which had the exact
4649        * opposite effect of that intended.
4650        */
4651       {
4652          png_bytep temp = png_ptr->big_row_buf + 32;
4653          int extra = (int)((temp - (png_bytep)0) & 0x0f);
4654          png_ptr->row_buf = temp - extra - 1/*filter byte*/;
4655 
4656          temp = png_ptr->big_prev_row + 32;
4657          extra = (int)((temp - (png_bytep)0) & 0x0f);
4658          png_ptr->prev_row = temp - extra - 1/*filter byte*/;
4659       }
4660 
4661 #else
4662       /* Use 31 bytes of padding before and 17 bytes after row_buf. */
4663       png_ptr->row_buf = png_ptr->big_row_buf + 31;
4664       png_ptr->prev_row = png_ptr->big_prev_row + 31;
4665 #endif
4666       png_ptr->old_big_row_buf_size = row_bytes + 48;
4667    }
4668 
4669 #ifdef PNG_MAX_MALLOC_64K
4670    if (png_ptr->rowbytes > 65535)
4671       png_error(png_ptr, "This image requires a row greater than 64KB");
4672 
4673 #endif
4674    if (png_ptr->rowbytes > (PNG_SIZE_MAX - 1))
4675       png_error(png_ptr, "Row has too many bytes to allocate in memory");
4676 
4677    memset(png_ptr->prev_row, 0, png_ptr->rowbytes + 1);
4678 
4679    png_debug1(3, "width = %u,", png_ptr->width);
4680    png_debug1(3, "height = %u,", png_ptr->height);
4681    png_debug1(3, "iwidth = %u,", png_ptr->iwidth);
4682    png_debug1(3, "num_rows = %u,", png_ptr->num_rows);
4683    png_debug1(3, "rowbytes = %lu,", (unsigned long)png_ptr->rowbytes);
4684    png_debug1(3, "irowbytes = %lu",
4685        (unsigned long)PNG_ROWBYTES(png_ptr->pixel_depth, png_ptr->iwidth) + 1);
4686 
4687    /* The sequential reader needs a buffer for IDAT, but the progressive reader
4688     * does not, so free the read buffer now regardless; the sequential reader
4689     * reallocates it on demand.
4690     */
4691    if (png_ptr->read_buffer != NULL)
4692    {
4693       png_bytep buffer = png_ptr->read_buffer;
4694 
4695       png_ptr->read_buffer_size = 0;
4696       png_ptr->read_buffer = NULL;
4697       png_free(png_ptr, buffer);
4698    }
4699 
4700    /* Finally claim the zstream for the inflate of the IDAT data, use the bits
4701     * value from the stream (note that this will result in a fatal error if the
4702     * IDAT stream has a bogus deflate header window_bits value, but this should
4703     * not be happening any longer!)
4704     */
4705    if (png_inflate_claim(png_ptr, png_IDAT) != Z_OK)
4706       png_error(png_ptr, png_ptr->zstream.msg);
4707 
4708    png_ptr->flags |= PNG_FLAG_ROW_INIT;
4709 }
4710 #endif /* READ */