1 /* 2 * Copyright (c) 2005, 2014, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #include "precompiled.hpp" 26 #include "runtime/interfaceSupport.hpp" 27 #include "runtime/os.inline.hpp" 28 #include "services/attachListener.hpp" 29 #include "services/dtraceAttacher.hpp" 30 31 #include <unistd.h> 32 #include <signal.h> 33 #include <sys/types.h> 34 #include <sys/socket.h> 35 #include <sys/un.h> 36 #include <sys/stat.h> 37 38 #ifndef UNIX_PATH_MAX 39 #define UNIX_PATH_MAX sizeof(((struct sockaddr_un *)0)->sun_path) 40 #endif 41 42 // The attach mechanism on Bsd uses a UNIX domain socket. An attach listener 43 // thread is created at startup or is created on-demand via a signal from 44 // the client tool. The attach listener creates a socket and binds it to a file 45 // in the filesystem. The attach listener then acts as a simple (single- 46 // threaded) server - it waits for a client to connect, reads the request, 47 // executes it, and returns the response to the client via the socket 48 // connection. 49 // 50 // As the socket is a UNIX domain socket it means that only clients on the 51 // local machine can connect. In addition there are two other aspects to 52 // the security: 53 // 1. The well known file that the socket is bound to has permission 400 54 // 2. When a client connect, the SO_PEERCRED socket option is used to 55 // obtain the credentials of client. We check that the effective uid 56 // of the client matches this process. 57 58 // forward reference 59 class BsdAttachOperation; 60 61 class BsdAttachListener: AllStatic { 62 private: 63 // the path to which we bind the UNIX domain socket 64 static char _path[UNIX_PATH_MAX]; 65 static bool _has_path; 66 67 // the file descriptor for the listening socket 68 static int _listener; 69 70 static void set_path(char* path) { 71 if (path == NULL) { 72 _has_path = false; 73 } else { 74 strncpy(_path, path, UNIX_PATH_MAX); 75 _path[UNIX_PATH_MAX-1] = '\0'; 76 _has_path = true; 77 } 78 } 79 80 static void set_listener(int s) { _listener = s; } 81 82 // reads a request from the given connected socket 83 static BsdAttachOperation* read_request(int s); 84 85 public: 86 enum { 87 ATTACH_PROTOCOL_VER = 1 // protocol version 88 }; 89 enum { 90 ATTACH_ERROR_BADVERSION = 101 // error codes 91 }; 92 93 // initialize the listener, returns 0 if okay 94 static int init(); 95 96 static char* path() { return _path; } 97 static bool has_path() { return _has_path; } 98 static int listener() { return _listener; } 99 100 // write the given buffer to a socket 101 static int write_fully(int s, char* buf, int len); 102 103 static BsdAttachOperation* dequeue(); 104 }; 105 106 class BsdAttachOperation: public AttachOperation { 107 private: 108 // the connection to the client 109 int _socket; 110 111 public: 112 void complete(jint res, bufferedStream* st); 113 114 void set_socket(int s) { _socket = s; } 115 int socket() const { return _socket; } 116 117 BsdAttachOperation(char* name) : AttachOperation(name) { 118 set_socket(-1); 119 } 120 }; 121 122 // statics 123 char BsdAttachListener::_path[UNIX_PATH_MAX]; 124 bool BsdAttachListener::_has_path; 125 int BsdAttachListener::_listener = -1; 126 127 // Supporting class to help split a buffer into individual components 128 class ArgumentIterator : public StackObj { 129 private: 130 char* _pos; 131 char* _end; 132 public: 133 ArgumentIterator(char* arg_buffer, size_t arg_size) { 134 _pos = arg_buffer; 135 _end = _pos + arg_size - 1; 136 } 137 char* next() { 138 if (*_pos == '\0') { 139 return NULL; 140 } 141 char* res = _pos; 142 char* next_pos = strchr(_pos, '\0'); 143 if (next_pos < _end) { 144 next_pos++; 145 } 146 _pos = next_pos; 147 return res; 148 } 149 }; 150 151 152 // atexit hook to stop listener and unlink the file that it is 153 // bound too. 154 extern "C" { 155 static void listener_cleanup() { 156 static int cleanup_done; 157 if (!cleanup_done) { 158 cleanup_done = 1; 159 int s = BsdAttachListener::listener(); 160 if (s != -1) { 161 ::close(s); 162 } 163 if (BsdAttachListener::has_path()) { 164 ::unlink(BsdAttachListener::path()); 165 } 166 } 167 } 168 } 169 170 // Initialization - create a listener socket and bind it to a file 171 172 int BsdAttachListener::init() { 173 char path[UNIX_PATH_MAX]; // socket file 174 char initial_path[UNIX_PATH_MAX]; // socket file during setup 175 int listener; // listener socket (file descriptor) 176 177 // register function to cleanup 178 ::atexit(listener_cleanup); 179 180 int n = snprintf(path, UNIX_PATH_MAX, "%s/.java_pid%d", 181 os::get_temp_directory(), os::current_process_id()); 182 if (n < (int)UNIX_PATH_MAX) { 183 n = snprintf(initial_path, UNIX_PATH_MAX, "%s.tmp", path); 184 } 185 if (n >= (int)UNIX_PATH_MAX) { 186 return -1; 187 } 188 189 // create the listener socket 190 listener = ::socket(PF_UNIX, SOCK_STREAM, 0); 191 if (listener == -1) { 192 return -1; 193 } 194 195 // bind socket 196 struct sockaddr_un addr; 197 addr.sun_family = AF_UNIX; 198 strcpy(addr.sun_path, initial_path); 199 ::unlink(initial_path); 200 int res = ::bind(listener, (struct sockaddr*)&addr, sizeof(addr)); 201 if (res == -1) { 202 ::close(listener); 203 return -1; 204 } 205 206 // put in listen mode, set permissions, and rename into place 207 res = ::listen(listener, 5); 208 if (res == 0) { 209 RESTARTABLE(::chmod(initial_path, S_IREAD|S_IWRITE), res); 210 if (res == 0) { 211 // make sure the file is owned by the effective user and effective group 212 // (this is the default on linux, but not on mac os) 213 RESTARTABLE(::chown(initial_path, geteuid(), getegid()), res); 214 if (res == 0) { 215 res = ::rename(initial_path, path); 216 } 217 } 218 } 219 if (res == -1) { 220 ::close(listener); 221 ::unlink(initial_path); 222 return -1; 223 } 224 set_path(path); 225 set_listener(listener); 226 227 return 0; 228 } 229 230 // Given a socket that is connected to a peer we read the request and 231 // create an AttachOperation. As the socket is blocking there is potential 232 // for a denial-of-service if the peer does not response. However this happens 233 // after the peer credentials have been checked and in the worst case it just 234 // means that the attach listener thread is blocked. 235 // 236 BsdAttachOperation* BsdAttachListener::read_request(int s) { 237 char ver_str[8]; 238 sprintf(ver_str, "%d", ATTACH_PROTOCOL_VER); 239 240 // The request is a sequence of strings so we first figure out the 241 // expected count and the maximum possible length of the request. 242 // The request is: 243 // <ver>0<cmd>0<arg>0<arg>0<arg>0 244 // where <ver> is the protocol version (1), <cmd> is the command 245 // name ("load", "datadump", ...), and <arg> is an argument 246 int expected_str_count = 2 + AttachOperation::arg_count_max; 247 const int max_len = (sizeof(ver_str) + 1) + (AttachOperation::name_length_max + 1) + 248 AttachOperation::arg_count_max*(AttachOperation::arg_length_max + 1); 249 250 char buf[max_len]; 251 int str_count = 0; 252 253 // Read until all (expected) strings have been read, the buffer is 254 // full, or EOF. 255 256 int off = 0; 257 int left = max_len; 258 259 do { 260 int n; 261 RESTARTABLE(read(s, buf+off, left), n); 262 if (n == -1) { 263 return NULL; // reset by peer or other error 264 } 265 if (n == 0) { 266 break; 267 } 268 for (int i=0; i<n; i++) { 269 if (buf[off+i] == 0) { 270 // EOS found 271 str_count++; 272 273 // The first string is <ver> so check it now to 274 // check for protocol mis-match 275 if (str_count == 1) { 276 if ((strlen(buf) != strlen(ver_str)) || 277 (atoi(buf) != ATTACH_PROTOCOL_VER)) { 278 char msg[32]; 279 sprintf(msg, "%d\n", ATTACH_ERROR_BADVERSION); 280 write_fully(s, msg, strlen(msg)); 281 return NULL; 282 } 283 } 284 } 285 } 286 off += n; 287 left -= n; 288 } while (left > 0 && str_count < expected_str_count); 289 290 if (str_count != expected_str_count) { 291 return NULL; // incomplete request 292 } 293 294 // parse request 295 296 ArgumentIterator args(buf, (max_len)-left); 297 298 // version already checked 299 char* v = args.next(); 300 301 char* name = args.next(); 302 if (name == NULL || strlen(name) > AttachOperation::name_length_max) { 303 return NULL; 304 } 305 306 BsdAttachOperation* op = new BsdAttachOperation(name); 307 308 for (int i=0; i<AttachOperation::arg_count_max; i++) { 309 char* arg = args.next(); 310 if (arg == NULL) { 311 op->set_arg(i, NULL); 312 } else { 313 if (strlen(arg) > AttachOperation::arg_length_max) { 314 delete op; 315 return NULL; 316 } 317 op->set_arg(i, arg); 318 } 319 } 320 321 op->set_socket(s); 322 return op; 323 } 324 325 326 // Dequeue an operation 327 // 328 // In the Bsd implementation there is only a single operation and clients 329 // cannot queue commands (except at the socket level). 330 // 331 BsdAttachOperation* BsdAttachListener::dequeue() { 332 for (;;) { 333 int s; 334 335 // wait for client to connect 336 struct sockaddr addr; 337 socklen_t len = sizeof(addr); 338 RESTARTABLE(::accept(listener(), &addr, &len), s); 339 if (s == -1) { 340 return NULL; // log a warning? 341 } 342 343 // get the credentials of the peer and check the effective uid/guid 344 // - check with jeff on this. 345 uid_t puid; 346 gid_t pgid; 347 if (::getpeereid(s, &puid, &pgid) != 0) { 348 ::close(s); 349 continue; 350 } 351 uid_t euid = geteuid(); 352 gid_t egid = getegid(); 353 354 if (puid != euid || pgid != egid) { 355 ::close(s); 356 continue; 357 } 358 359 // peer credential look okay so we read the request 360 BsdAttachOperation* op = read_request(s); 361 if (op == NULL) { 362 ::close(s); 363 continue; 364 } else { 365 return op; 366 } 367 } 368 } 369 370 // write the given buffer to the socket 371 int BsdAttachListener::write_fully(int s, char* buf, int len) { 372 do { 373 int n = ::write(s, buf, len); 374 if (n == -1) { 375 if (errno != EINTR) return -1; 376 } else { 377 buf += n; 378 len -= n; 379 } 380 } 381 while (len > 0); 382 return 0; 383 } 384 385 // Complete an operation by sending the operation result and any result 386 // output to the client. At this time the socket is in blocking mode so 387 // potentially we can block if there is a lot of data and the client is 388 // non-responsive. For most operations this is a non-issue because the 389 // default send buffer is sufficient to buffer everything. In the future 390 // if there are operations that involves a very big reply then it the 391 // socket could be made non-blocking and a timeout could be used. 392 393 void BsdAttachOperation::complete(jint result, bufferedStream* st) { 394 JavaThread* thread = JavaThread::current(); 395 ThreadBlockInVM tbivm(thread); 396 397 thread->set_suspend_equivalent(); 398 // cleared by handle_special_suspend_equivalent_condition() or 399 // java_suspend_self() via check_and_wait_while_suspended() 400 401 // write operation result 402 char msg[32]; 403 sprintf(msg, "%d\n", result); 404 int rc = BsdAttachListener::write_fully(this->socket(), msg, strlen(msg)); 405 406 // write any result data 407 if (rc == 0) { 408 BsdAttachListener::write_fully(this->socket(), (char*) st->base(), st->size()); 409 ::shutdown(this->socket(), 2); 410 } 411 412 // done 413 ::close(this->socket()); 414 415 // were we externally suspended while we were waiting? 416 thread->check_and_wait_while_suspended(); 417 418 delete this; 419 } 420 421 422 // AttachListener functions 423 424 AttachOperation* AttachListener::dequeue() { 425 JavaThread* thread = JavaThread::current(); 426 ThreadBlockInVM tbivm(thread); 427 428 thread->set_suspend_equivalent(); 429 // cleared by handle_special_suspend_equivalent_condition() or 430 // java_suspend_self() via check_and_wait_while_suspended() 431 432 AttachOperation* op = BsdAttachListener::dequeue(); 433 434 // were we externally suspended while we were waiting? 435 thread->check_and_wait_while_suspended(); 436 437 return op; 438 } 439 440 441 // Performs initialization at vm startup 442 // For BSD we remove any stale .java_pid file which could cause 443 // an attaching process to think we are ready to receive on the 444 // domain socket before we are properly initialized 445 446 void AttachListener::vm_start() { 447 char fn[UNIX_PATH_MAX]; 448 struct stat st; 449 int ret; 450 451 int n = snprintf(fn, UNIX_PATH_MAX, "%s/.java_pid%d", 452 os::get_temp_directory(), os::current_process_id()); 453 assert(n < (int)UNIX_PATH_MAX, "java_pid file name buffer overflow"); 454 455 RESTARTABLE(::stat(fn, &st), ret); 456 if (ret == 0) { 457 ret = ::unlink(fn); 458 if (ret == -1) { 459 log_debug(attach)("Failed to remove stale attach pid file at %s", fn); 460 } 461 } 462 } 463 464 int AttachListener::pd_init() { 465 JavaThread* thread = JavaThread::current(); 466 ThreadBlockInVM tbivm(thread); 467 468 thread->set_suspend_equivalent(); 469 // cleared by handle_special_suspend_equivalent_condition() or 470 // java_suspend_self() via check_and_wait_while_suspended() 471 472 int ret_code = BsdAttachListener::init(); 473 474 // were we externally suspended while we were waiting? 475 thread->check_and_wait_while_suspended(); 476 477 return ret_code; 478 } 479 480 // Attach Listener is started lazily except in the case when 481 // +ReduseSignalUsage is used 482 bool AttachListener::init_at_startup() { 483 if (ReduceSignalUsage) { 484 return true; 485 } else { 486 return false; 487 } 488 } 489 490 // If the file .attach_pid<pid> exists in the working directory 491 // or /tmp then this is the trigger to start the attach mechanism 492 bool AttachListener::is_init_trigger() { 493 if (init_at_startup() || is_initialized()) { 494 return false; // initialized at startup or already initialized 495 } 496 char fn[PATH_MAX + 1]; 497 int ret; 498 struct stat st; 499 500 snprintf(fn, PATH_MAX + 1, "%s/.attach_pid%d", 501 os::get_temp_directory(), os::current_process_id()); 502 RESTARTABLE(::stat(fn, &st), ret); 503 if (ret == -1) { 504 log_debug(attach)("Failed to find attach file: %s", fn); 505 } 506 if (ret == 0) { 507 // simple check to avoid starting the attach mechanism when 508 // a bogus user creates the file 509 if (st.st_uid == geteuid()) { 510 init(); 511 log_trace(attach)("Attach trigerred by %s", fn); 512 return true; 513 } else { 514 log_debug(attach)("File %s has wrong user id %d (vs %d). Attach is not triggered", fn, st.st_uid, geteuid()); 515 } 516 } 517 return false; 518 } 519 520 // if VM aborts then remove listener 521 void AttachListener::abort() { 522 listener_cleanup(); 523 } 524 525 void AttachListener::pd_data_dump() { 526 os::signal_notify(SIGQUIT); 527 } 528 529 AttachOperationFunctionInfo* AttachListener::pd_find_operation(const char* n) { 530 return NULL; 531 } 532 533 jint AttachListener::pd_set_flag(AttachOperation* op, outputStream* out) { 534 out->print_cr("flag '%s' cannot be changed", op->arg(0)); 535 return JNI_ERR; 536 } 537 538 void AttachListener::pd_detachall() { 539 // do nothing for now 540 }