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 "logging/log.hpp" 27 #include "runtime/interfaceSupport.inline.hpp" 28 #include "runtime/os.inline.hpp" 29 #include "services/attachListener.hpp" 30 #include "services/dtraceAttacher.hpp" 31 32 #include <unistd.h> 33 #include <signal.h> 34 #include <sys/types.h> 35 #include <sys/socket.h> 36 #include <sys/un.h> 37 #include <sys/stat.h> 38 39 #ifndef UNIX_PATH_MAX 40 #define UNIX_PATH_MAX sizeof(((struct sockaddr_un *)0)->sun_path) 41 #endif 42 43 // The attach mechanism on Bsd uses a UNIX domain socket. An attach listener 44 // thread is created at startup or is created on-demand via a signal from 45 // the client tool. The attach listener creates a socket and binds it to a file 46 // in the filesystem. The attach listener then acts as a simple (single- 47 // threaded) server - it waits for a client to connect, reads the request, 48 // executes it, and returns the response to the client via the socket 49 // connection. 50 // 51 // As the socket is a UNIX domain socket it means that only clients on the 52 // local machine can connect. In addition there are two other aspects to 53 // the security: 54 // 1. The well known file that the socket is bound to has permission 400 55 // 2. When a client connect, the SO_PEERCRED socket option is used to 56 // obtain the credentials of client. We check that the effective uid 57 // of the client matches this process. 58 59 // forward reference 60 class BsdAttachOperation; 61 62 class BsdAttachListener: AllStatic { 63 private: 64 // the path to which we bind the UNIX domain socket 65 static char _path[UNIX_PATH_MAX]; 66 static bool _has_path; 67 68 // the file descriptor for the listening socket 69 static int _listener; 70 71 static void set_path(char* path) { 72 if (path == NULL) { 73 _has_path = false; 74 } else { 75 strncpy(_path, path, UNIX_PATH_MAX); 76 _path[UNIX_PATH_MAX-1] = '\0'; 77 _has_path = true; 78 } 79 } 80 81 static void set_listener(int s) { _listener = s; } 82 83 // reads a request from the given connected socket 84 static BsdAttachOperation* read_request(int s); 85 86 public: 87 enum { 88 ATTACH_PROTOCOL_VER = 1 // protocol version 89 }; 90 enum { 91 ATTACH_ERROR_BADVERSION = 101 // error codes 92 }; 93 94 // initialize the listener, returns 0 if okay 95 static int init(); 96 97 static char* path() { return _path; } 98 static bool has_path() { return _has_path; } 99 static int listener() { return _listener; } 100 101 // write the given buffer to a socket 102 static int write_fully(int s, char* buf, int len); 103 104 static BsdAttachOperation* dequeue(); 105 }; 106 107 class BsdAttachOperation: public AttachOperation { 108 private: 109 // the connection to the client 110 int _socket; 111 112 public: 113 void complete(jint res, bufferedStream* st); 114 115 void set_socket(int s) { _socket = s; } 116 int socket() const { return _socket; } 117 118 BsdAttachOperation(char* name) : AttachOperation(name) { 119 set_socket(-1); 120 } 121 }; 122 123 // statics 124 char BsdAttachListener::_path[UNIX_PATH_MAX]; 125 bool BsdAttachListener::_has_path; 126 int BsdAttachListener::_listener = -1; 127 128 // Supporting class to help split a buffer into individual components 129 class ArgumentIterator : public StackObj { 130 private: 131 char* _pos; 132 char* _end; 133 public: 134 ArgumentIterator(char* arg_buffer, size_t arg_size) { 135 _pos = arg_buffer; 136 _end = _pos + arg_size - 1; 137 } 138 char* next() { 139 if (*_pos == '\0') { 140 return NULL; 141 } 142 char* res = _pos; 143 char* next_pos = strchr(_pos, '\0'); 144 if (next_pos < _end) { 145 next_pos++; 146 } 147 _pos = next_pos; 148 return res; 149 } 150 }; 151 152 153 // atexit hook to stop listener and unlink the file that it is 154 // bound too. 155 extern "C" { 156 static void listener_cleanup() { 157 static int cleanup_done; 158 if (!cleanup_done) { 159 cleanup_done = 1; 160 int s = BsdAttachListener::listener(); 161 if (s != -1) { 162 ::close(s); 163 } 164 if (BsdAttachListener::has_path()) { 165 ::unlink(BsdAttachListener::path()); 166 } 167 } 168 } 169 } 170 171 // Initialization - create a listener socket and bind it to a file 172 173 int BsdAttachListener::init() { 174 char path[UNIX_PATH_MAX]; // socket file 175 char initial_path[UNIX_PATH_MAX]; // socket file during setup 176 int listener; // listener socket (file descriptor) 177 178 // register function to cleanup 179 ::atexit(listener_cleanup); 180 181 int n = snprintf(path, UNIX_PATH_MAX, "%s/.java_pid%d", 182 os::get_temp_directory(), os::current_process_id()); 183 if (n < (int)UNIX_PATH_MAX) { 184 n = snprintf(initial_path, UNIX_PATH_MAX, "%s.tmp", path); 185 } 186 if (n >= (int)UNIX_PATH_MAX) { 187 return -1; 188 } 189 190 // create the listener socket 191 listener = ::socket(PF_UNIX, SOCK_STREAM, 0); 192 if (listener == -1) { 193 return -1; 194 } 195 196 // bind socket 197 struct sockaddr_un addr; 198 addr.sun_family = AF_UNIX; 199 strcpy(addr.sun_path, initial_path); 200 ::unlink(initial_path); 201 int res = ::bind(listener, (struct sockaddr*)&addr, sizeof(addr)); 202 if (res == -1) { 203 ::close(listener); 204 return -1; 205 } 206 207 // put in listen mode, set permissions, and rename into place 208 res = ::listen(listener, 5); 209 if (res == 0) { 210 RESTARTABLE(::chmod(initial_path, S_IREAD|S_IWRITE), res); 211 if (res == 0) { 212 // make sure the file is owned by the effective user and effective group 213 // (this is the default on linux, but not on mac os) 214 RESTARTABLE(::chown(initial_path, geteuid(), getegid()), res); 215 if (res == 0) { 216 res = ::rename(initial_path, path); 217 } 218 } 219 } 220 if (res == -1) { 221 ::close(listener); 222 ::unlink(initial_path); 223 return -1; 224 } 225 set_path(path); 226 set_listener(listener); 227 228 return 0; 229 } 230 231 // Given a socket that is connected to a peer we read the request and 232 // create an AttachOperation. As the socket is blocking there is potential 233 // for a denial-of-service if the peer does not response. However this happens 234 // after the peer credentials have been checked and in the worst case it just 235 // means that the attach listener thread is blocked. 236 // 237 BsdAttachOperation* BsdAttachListener::read_request(int s) { 238 char ver_str[8]; 239 sprintf(ver_str, "%d", ATTACH_PROTOCOL_VER); 240 241 // The request is a sequence of strings so we first figure out the 242 // expected count and the maximum possible length of the request. 243 // The request is: 244 // <ver>0<cmd>0<arg>0<arg>0<arg>0 245 // where <ver> is the protocol version (1), <cmd> is the command 246 // name ("load", "datadump", ...), and <arg> is an argument 247 int expected_str_count = 2 + AttachOperation::arg_count_max; 248 const int max_len = (sizeof(ver_str) + 1) + (AttachOperation::name_length_max + 1) + 249 AttachOperation::arg_count_max*(AttachOperation::arg_length_max + 1); 250 251 char buf[max_len]; 252 int str_count = 0; 253 254 // Read until all (expected) strings have been read, the buffer is 255 // full, or EOF. 256 257 int off = 0; 258 int left = max_len; 259 260 do { 261 int n; 262 RESTARTABLE(read(s, buf+off, left), n); 263 if (n == -1) { 264 return NULL; // reset by peer or other error 265 } 266 if (n == 0) { 267 break; 268 } 269 for (int i=0; i<n; i++) { 270 if (buf[off+i] == 0) { 271 // EOS found 272 str_count++; 273 274 // The first string is <ver> so check it now to 275 // check for protocol mis-match 276 if (str_count == 1) { 277 if ((strlen(buf) != strlen(ver_str)) || 278 (atoi(buf) != ATTACH_PROTOCOL_VER)) { 279 char msg[32]; 280 sprintf(msg, "%d\n", ATTACH_ERROR_BADVERSION); 281 write_fully(s, msg, strlen(msg)); 282 return NULL; 283 } 284 } 285 } 286 } 287 off += n; 288 left -= n; 289 } while (left > 0 && str_count < expected_str_count); 290 291 if (str_count != expected_str_count) { 292 return NULL; // incomplete request 293 } 294 295 // parse request 296 297 ArgumentIterator args(buf, (max_len)-left); 298 299 // version already checked 300 char* v = args.next(); 301 302 char* name = args.next(); 303 if (name == NULL || strlen(name) > AttachOperation::name_length_max) { 304 return NULL; 305 } 306 307 BsdAttachOperation* op = new BsdAttachOperation(name); 308 309 for (int i=0; i<AttachOperation::arg_count_max; i++) { 310 char* arg = args.next(); 311 if (arg == NULL) { 312 op->set_arg(i, NULL); 313 } else { 314 if (strlen(arg) > AttachOperation::arg_length_max) { 315 delete op; 316 return NULL; 317 } 318 op->set_arg(i, arg); 319 } 320 } 321 322 op->set_socket(s); 323 return op; 324 } 325 326 327 // Dequeue an operation 328 // 329 // In the Bsd implementation there is only a single operation and clients 330 // cannot queue commands (except at the socket level). 331 // 332 BsdAttachOperation* BsdAttachListener::dequeue() { 333 for (;;) { 334 int s; 335 336 // wait for client to connect 337 struct sockaddr addr; 338 socklen_t len = sizeof(addr); 339 RESTARTABLE(::accept(listener(), &addr, &len), s); 340 if (s == -1) { 341 return NULL; // log a warning? 342 } 343 344 // get the credentials of the peer and check the effective uid/guid 345 // - check with jeff on this. 346 uid_t puid; 347 gid_t pgid; 348 if (::getpeereid(s, &puid, &pgid) != 0) { 349 ::close(s); 350 continue; 351 } 352 uid_t euid = geteuid(); 353 gid_t egid = getegid(); 354 355 if (puid != euid || pgid != egid) { 356 ::close(s); 357 continue; 358 } 359 360 // peer credential look okay so we read the request 361 BsdAttachOperation* op = read_request(s); 362 if (op == NULL) { 363 ::close(s); 364 continue; 365 } else { 366 return op; 367 } 368 } 369 } 370 371 // write the given buffer to the socket 372 int BsdAttachListener::write_fully(int s, char* buf, int len) { 373 do { 374 int n = ::write(s, buf, len); 375 if (n == -1) { 376 if (errno != EINTR) return -1; 377 } else { 378 buf += n; 379 len -= n; 380 } 381 } 382 while (len > 0); 383 return 0; 384 } 385 386 // Complete an operation by sending the operation result and any result 387 // output to the client. At this time the socket is in blocking mode so 388 // potentially we can block if there is a lot of data and the client is 389 // non-responsive. For most operations this is a non-issue because the 390 // default send buffer is sufficient to buffer everything. In the future 391 // if there are operations that involves a very big reply then it the 392 // socket could be made non-blocking and a timeout could be used. 393 394 void BsdAttachOperation::complete(jint result, bufferedStream* st) { 395 JavaThread* thread = JavaThread::current(); 396 ThreadBlockInVM tbivm(thread); 397 398 thread->set_suspend_equivalent(); 399 // cleared by handle_special_suspend_equivalent_condition() or 400 // java_suspend_self() via check_and_wait_while_suspended() 401 402 // write operation result 403 char msg[32]; 404 sprintf(msg, "%d\n", result); 405 int rc = BsdAttachListener::write_fully(this->socket(), msg, strlen(msg)); 406 407 // write any result data 408 if (rc == 0) { 409 BsdAttachListener::write_fully(this->socket(), (char*) st->base(), st->size()); 410 ::shutdown(this->socket(), 2); 411 } 412 413 // done 414 ::close(this->socket()); 415 416 // were we externally suspended while we were waiting? 417 thread->check_and_wait_while_suspended(); 418 419 delete this; 420 } 421 422 423 // AttachListener functions 424 425 AttachOperation* AttachListener::dequeue() { 426 JavaThread* thread = JavaThread::current(); 427 ThreadBlockInVM tbivm(thread); 428 429 thread->set_suspend_equivalent(); 430 // cleared by handle_special_suspend_equivalent_condition() or 431 // java_suspend_self() via check_and_wait_while_suspended() 432 433 AttachOperation* op = BsdAttachListener::dequeue(); 434 435 // were we externally suspended while we were waiting? 436 thread->check_and_wait_while_suspended(); 437 438 return op; 439 } 440 441 442 // Performs initialization at vm startup 443 // For BSD we remove any stale .java_pid file which could cause 444 // an attaching process to think we are ready to receive on the 445 // domain socket before we are properly initialized 446 447 void AttachListener::vm_start() { 448 char fn[UNIX_PATH_MAX]; 449 struct stat st; 450 int ret; 451 452 int n = snprintf(fn, UNIX_PATH_MAX, "%s/.java_pid%d", 453 os::get_temp_directory(), os::current_process_id()); 454 assert(n < (int)UNIX_PATH_MAX, "java_pid file name buffer overflow"); 455 456 RESTARTABLE(::stat(fn, &st), ret); 457 if (ret == 0) { 458 ret = ::unlink(fn); 459 if (ret == -1) { 460 log_debug(attach)("Failed to remove stale attach pid file at %s", fn); 461 } 462 } 463 } 464 465 int AttachListener::pd_init() { 466 JavaThread* thread = JavaThread::current(); 467 ThreadBlockInVM tbivm(thread); 468 469 thread->set_suspend_equivalent(); 470 // cleared by handle_special_suspend_equivalent_condition() or 471 // java_suspend_self() via check_and_wait_while_suspended() 472 473 int ret_code = BsdAttachListener::init(); 474 475 // were we externally suspended while we were waiting? 476 thread->check_and_wait_while_suspended(); 477 478 return ret_code; 479 } 480 481 // Attach Listener is started lazily except in the case when 482 // +ReduseSignalUsage is used 483 bool AttachListener::init_at_startup() { 484 if (ReduceSignalUsage) { 485 return true; 486 } else { 487 return false; 488 } 489 } 490 491 // If the file .attach_pid<pid> exists in the working directory 492 // or /tmp then this is the trigger to start the attach mechanism 493 bool AttachListener::is_init_trigger() { 494 if (init_at_startup() || is_initialized()) { 495 return false; // initialized at startup or already initialized 496 } 497 char fn[PATH_MAX + 1]; 498 int ret; 499 struct stat st; 500 501 snprintf(fn, PATH_MAX + 1, "%s/.attach_pid%d", 502 os::get_temp_directory(), os::current_process_id()); 503 RESTARTABLE(::stat(fn, &st), ret); 504 if (ret == -1) { 505 log_debug(attach)("Failed to find attach file: %s", fn); 506 } 507 if (ret == 0) { 508 // simple check to avoid starting the attach mechanism when 509 // a bogus user creates the file 510 if (st.st_uid == geteuid()) { 511 init(); 512 log_trace(attach)("Attach trigerred by %s", fn); 513 return true; 514 } else { 515 log_debug(attach)("File %s has wrong user id %d (vs %d). Attach is not triggered", fn, st.st_uid, geteuid()); 516 } 517 } 518 return false; 519 } 520 521 // if VM aborts then remove listener 522 void AttachListener::abort() { 523 listener_cleanup(); 524 } 525 526 void AttachListener::pd_data_dump() { 527 os::signal_notify(SIGQUIT); 528 } 529 530 AttachOperationFunctionInfo* AttachListener::pd_find_operation(const char* n) { 531 return NULL; 532 } 533 534 jint AttachListener::pd_set_flag(AttachOperation* op, outputStream* out) { 535 out->print_cr("flag '%s' cannot be changed", op->arg(0)); 536 return JNI_ERR; 537 } 538 539 void AttachListener::pd_detachall() { 540 // do nothing for now 541 }