1 /* 2 * Copyright (c) 2005, 2019, Oracle and/or its affiliates. All rights reserved. 3 * Copyright (c) 2012, 2018 SAP SE. All rights reserved. 4 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 5 * 6 * This code is free software; you can redistribute it and/or modify it 7 * under the terms of the GNU General Public License version 2 only, as 8 * published by the Free Software Foundation. 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 26 #include "precompiled.hpp" 27 #include "logging/log.hpp" 28 #include "runtime/interfaceSupport.inline.hpp" 29 #include "runtime/os.inline.hpp" 30 #include "services/attachListener.hpp" 31 #include "services/dtraceAttacher.hpp" 32 33 #include <signal.h> 34 #include <sys/socket.h> 35 #include <sys/stat.h> 36 #include <sys/types.h> 37 #include <sys/un.h> 38 #include <unistd.h> 39 40 #ifndef UNIX_PATH_MAX 41 #define UNIX_PATH_MAX sizeof(((struct sockaddr_un *)0)->sun_path) 42 #endif 43 44 // The attach mechanism on AIX uses a UNIX domain socket. An attach listener 45 // thread is created at startup or is created on-demand via a signal from 46 // the client tool. The attach listener creates a socket and binds it to a file 47 // in the filesystem. The attach listener then acts as a simple (single- 48 // threaded) server - it waits for a client to connect, reads the request, 49 // executes it, and returns the response to the client via the socket 50 // connection. 51 // 52 // As the socket is a UNIX domain socket it means that only clients on the 53 // local machine can connect. In addition there are two other aspects to 54 // the security: 55 // 1. The well known file that the socket is bound to has permission 400 56 // 2. When a client connect, the SO_PEERID socket option is used to 57 // obtain the credentials of client. We check that the effective uid 58 // of the client matches this process. 59 60 // forward reference 61 class AixAttachOperation; 62 63 class AixAttachListener: AllStatic { 64 private: 65 // the path to which we bind the UNIX domain socket 66 static char _path[UNIX_PATH_MAX]; 67 static bool _has_path; 68 // Shutdown marker to prevent accept blocking during clean-up. 69 static bool _shutdown; 70 71 // the file descriptor for the listening socket 72 static int _listener; 73 74 static bool _atexit_registered; 75 76 // reads a request from the given connected socket 77 static AixAttachOperation* read_request(int s); 78 79 public: 80 enum { 81 ATTACH_PROTOCOL_VER = 1 // protocol version 82 }; 83 enum { 84 ATTACH_ERROR_BADVERSION = 101 // error codes 85 }; 86 87 static void set_path(char* path) { 88 if (path == NULL) { 89 _path[0] = '\0'; 90 _has_path = false; 91 } else { 92 strncpy(_path, path, UNIX_PATH_MAX); 93 _path[UNIX_PATH_MAX-1] = '\0'; 94 _has_path = true; 95 } 96 } 97 98 static void set_listener(int s) { _listener = s; } 99 100 // initialize the listener, returns 0 if okay 101 static int init(); 102 103 static char* path() { return _path; } 104 static bool has_path() { return _has_path; } 105 static int listener() { return _listener; } 106 // Shutdown marker to prevent accept blocking during clean-up 107 static void set_shutdown(bool shutdown) { _shutdown = shutdown; } 108 static bool is_shutdown() { return _shutdown; } 109 110 // write the given buffer to a socket 111 static int write_fully(int s, char* buf, int len); 112 113 static AixAttachOperation* dequeue(); 114 }; 115 116 class AixAttachOperation: public AttachOperation { 117 private: 118 // the connection to the client 119 int _socket; 120 121 public: 122 void complete(jint res, bufferedStream* st); 123 124 void set_socket(int s) { _socket = s; } 125 int socket() const { return _socket; } 126 127 AixAttachOperation(char* name) : AttachOperation(name) { 128 set_socket(-1); 129 } 130 }; 131 132 // statics 133 char AixAttachListener::_path[UNIX_PATH_MAX]; 134 bool AixAttachListener::_has_path; 135 int AixAttachListener::_listener = -1; 136 bool AixAttachListener::_atexit_registered = false; 137 // Shutdown marker to prevent accept blocking during clean-up 138 bool AixAttachListener::_shutdown = false; 139 140 // Supporting class to help split a buffer into individual components 141 class ArgumentIterator : public StackObj { 142 private: 143 char* _pos; 144 char* _end; 145 public: 146 ArgumentIterator(char* arg_buffer, size_t arg_size) { 147 _pos = arg_buffer; 148 _end = _pos + arg_size - 1; 149 } 150 char* next() { 151 if (*_pos == '\0') { 152 // advance the iterator if possible (null arguments) 153 if (_pos < _end) { 154 _pos += 1; 155 } 156 return NULL; 157 } 158 char* res = _pos; 159 char* next_pos = strchr(_pos, '\0'); 160 if (next_pos < _end) { 161 next_pos++; 162 } 163 _pos = next_pos; 164 return res; 165 } 166 }; 167 168 // On AIX if sockets block until all data has been transmitted 169 // successfully in some communication domains a socket "close" may 170 // never complete. We have to take care that after the socket shutdown 171 // the listener never enters accept state. 172 173 // atexit hook to stop listener and unlink the file that it is 174 // bound too. 175 176 // Some modifications to the listener logic to prevent deadlocks on exit. 177 // 1. We Shutdown the socket here instead. AixAttachOperation::complete() is not the right place 178 // since more than one agent in a sequence in JPLIS live tests wouldn't work (Listener thread 179 // would be dead after the first operation completion). 180 // 2. close(s) may never return if the listener thread is in socket accept(). Unlinking the file 181 // should be sufficient for cleanup. 182 extern "C" { 183 static void listener_cleanup() { 184 AixAttachListener::set_shutdown(true); 185 int s = AixAttachListener::listener(); 186 if (s != -1) { 187 AixAttachListener::set_listener(-1); 188 ::shutdown(s, 2); 189 } 190 if (AixAttachListener::has_path()) { 191 ::unlink(AixAttachListener::path()); 192 AixAttachListener::set_path(NULL); 193 } 194 } 195 } 196 197 // Initialization - create a listener socket and bind it to a file 198 199 int AixAttachListener::init() { 200 char path[UNIX_PATH_MAX]; // socket file 201 char initial_path[UNIX_PATH_MAX]; // socket file during setup 202 int listener; // listener socket (file descriptor) 203 204 // register function to cleanup 205 if (!_atexit_registered) { 206 _atexit_registered = true; 207 ::atexit(listener_cleanup); 208 } 209 210 int n = snprintf(path, UNIX_PATH_MAX, "%s/.java_pid%d", 211 os::get_temp_directory(), os::current_process_id()); 212 if (n < (int)UNIX_PATH_MAX) { 213 n = snprintf(initial_path, UNIX_PATH_MAX, "%s.tmp", path); 214 } 215 if (n >= (int)UNIX_PATH_MAX) { 216 return -1; 217 } 218 219 // create the listener socket 220 listener = ::socket(PF_UNIX, SOCK_STREAM, 0); 221 if (listener == -1) { 222 return -1; 223 } 224 225 // bind socket 226 struct sockaddr_un addr; 227 memset((void *)&addr, 0, sizeof(addr)); 228 addr.sun_family = AF_UNIX; 229 strcpy(addr.sun_path, initial_path); 230 ::unlink(initial_path); 231 // We must call bind with the actual socketaddr length. This is obligatory for AS400. 232 int res = ::bind(listener, (struct sockaddr*)&addr, SUN_LEN(&addr)); 233 if (res == -1) { 234 ::close(listener); 235 return -1; 236 } 237 238 // put in listen mode, set permissions, and rename into place 239 res = ::listen(listener, 5); 240 if (res == 0) { 241 RESTARTABLE(::chmod(initial_path, S_IREAD|S_IWRITE), res); 242 if (res == 0) { 243 // make sure the file is owned by the effective user and effective group 244 // e.g. the group could be inherited from the directory in case the s bit is set 245 RESTARTABLE(::chown(initial_path, geteuid(), getegid()), res); 246 if (res == 0) { 247 res = ::rename(initial_path, path); 248 } 249 } 250 } 251 if (res == -1) { 252 ::close(listener); 253 ::unlink(initial_path); 254 return -1; 255 } 256 set_path(path); 257 set_listener(listener); 258 set_shutdown(false); 259 260 return 0; 261 } 262 263 // Given a socket that is connected to a peer we read the request and 264 // create an AttachOperation. As the socket is blocking there is potential 265 // for a denial-of-service if the peer does not response. However this happens 266 // after the peer credentials have been checked and in the worst case it just 267 // means that the attach listener thread is blocked. 268 // 269 AixAttachOperation* AixAttachListener::read_request(int s) { 270 char ver_str[8]; 271 sprintf(ver_str, "%d", ATTACH_PROTOCOL_VER); 272 273 // The request is a sequence of strings so we first figure out the 274 // expected count and the maximum possible length of the request. 275 // The request is: 276 // <ver>0<cmd>0<arg>0<arg>0<arg>0 277 // where <ver> is the protocol version (1), <cmd> is the command 278 // name ("load", "datadump", ...), and <arg> is an argument 279 int expected_str_count = 2 + AttachOperation::arg_count_max; 280 const int max_len = (sizeof(ver_str) + 1) + (AttachOperation::name_length_max + 1) + 281 AttachOperation::arg_count_max*(AttachOperation::arg_length_max + 1); 282 283 char buf[max_len]; 284 int str_count = 0; 285 286 // Read until all (expected) strings have been read, the buffer is 287 // full, or EOF. 288 289 int off = 0; 290 int left = max_len; 291 292 do { 293 int n; 294 // Don't block on interrupts because this will 295 // hang in the clean-up when shutting down. 296 n = read(s, buf+off, left); 297 assert(n <= left, "buffer was too small, impossible!"); 298 buf[max_len - 1] = '\0'; 299 if (n == -1) { 300 return NULL; // reset by peer or other error 301 } 302 if (n == 0) { 303 break; 304 } 305 for (int i=0; i<n; i++) { 306 if (buf[off+i] == 0) { 307 // EOS found 308 str_count++; 309 310 // The first string is <ver> so check it now to 311 // check for protocol mis-match 312 if (str_count == 1) { 313 if ((strlen(buf) != strlen(ver_str)) || 314 (atoi(buf) != ATTACH_PROTOCOL_VER)) { 315 char msg[32]; 316 sprintf(msg, "%d\n", ATTACH_ERROR_BADVERSION); 317 write_fully(s, msg, strlen(msg)); 318 return NULL; 319 } 320 } 321 } 322 } 323 off += n; 324 left -= n; 325 } while (left > 0 && str_count < expected_str_count); 326 327 if (str_count != expected_str_count) { 328 return NULL; // incomplete request 329 } 330 331 // parse request 332 333 ArgumentIterator args(buf, (max_len)-left); 334 335 // version already checked 336 char* v = args.next(); 337 338 char* name = args.next(); 339 if (name == NULL || strlen(name) > AttachOperation::name_length_max) { 340 return NULL; 341 } 342 343 AixAttachOperation* op = new AixAttachOperation(name); 344 345 for (int i=0; i<AttachOperation::arg_count_max; i++) { 346 char* arg = args.next(); 347 if (arg == NULL) { 348 op->set_arg(i, NULL); 349 } else { 350 if (strlen(arg) > AttachOperation::arg_length_max) { 351 delete op; 352 return NULL; 353 } 354 op->set_arg(i, arg); 355 } 356 } 357 358 op->set_socket(s); 359 return op; 360 } 361 362 363 // Dequeue an operation 364 // 365 // In the Aix implementation there is only a single operation and clients 366 // cannot queue commands (except at the socket level). 367 // 368 AixAttachOperation* AixAttachListener::dequeue() { 369 for (;;) { 370 int s; 371 372 // wait for client to connect 373 struct sockaddr addr; 374 socklen_t len = sizeof(addr); 375 memset(&addr, 0, len); 376 // We must prevent accept blocking on the socket if it has been shut down. 377 // Therefore we allow interrupts and check whether we have been shut down already. 378 if (AixAttachListener::is_shutdown()) { 379 return NULL; 380 } 381 s=::accept(listener(), &addr, &len); 382 if (s == -1) { 383 return NULL; // log a warning? 384 } 385 386 // get the credentials of the peer and check the effective uid/guid 387 struct peercred_struct cred_info; 388 socklen_t optlen = sizeof(cred_info); 389 if (::getsockopt(s, SOL_SOCKET, SO_PEERID, (void*)&cred_info, &optlen) == -1) { 390 log_debug(attach)("Failed to get socket option SO_PEERID"); 391 ::close(s); 392 continue; 393 } 394 395 if (!os::Posix::matches_effective_uid_and_gid_or_root(cred_info.euid, cred_info.egid)) { 396 log_debug(attach)("euid/egid check failed (%d/%d vs %d/%d)", 397 cred_info.euid, cred_info.egid, geteuid(), getegid()); 398 ::close(s); 399 continue; 400 } 401 402 // peer credential look okay so we read the request 403 AixAttachOperation* op = read_request(s); 404 if (op == NULL) { 405 ::close(s); 406 continue; 407 } else { 408 return op; 409 } 410 } 411 } 412 413 // write the given buffer to the socket 414 int AixAttachListener::write_fully(int s, char* buf, int len) { 415 do { 416 int n = ::write(s, buf, len); 417 if (n == -1) { 418 if (errno != EINTR) return -1; 419 } else { 420 buf += n; 421 len -= n; 422 } 423 } 424 while (len > 0); 425 return 0; 426 } 427 428 // Complete an operation by sending the operation result and any result 429 // output to the client. At this time the socket is in blocking mode so 430 // potentially we can block if there is a lot of data and the client is 431 // non-responsive. For most operations this is a non-issue because the 432 // default send buffer is sufficient to buffer everything. In the future 433 // if there are operations that involves a very big reply then it the 434 // socket could be made non-blocking and a timeout could be used. 435 436 void AixAttachOperation::complete(jint result, bufferedStream* st) { 437 JavaThread* thread = JavaThread::current(); 438 ThreadBlockInVM tbivm(thread); 439 440 thread->set_suspend_equivalent(); 441 // cleared by handle_special_suspend_equivalent_condition() or 442 // java_suspend_self() via check_and_wait_while_suspended() 443 444 // write operation result 445 char msg[32]; 446 sprintf(msg, "%d\n", result); 447 int rc = AixAttachListener::write_fully(this->socket(), msg, strlen(msg)); 448 449 // write any result data 450 if (rc == 0) { 451 // Shutdown the socket in the cleanup function to enable more than 452 // one agent attach in a sequence (see comments to listener_cleanup()). 453 AixAttachListener::write_fully(this->socket(), (char*) st->base(), st->size()); 454 } 455 456 // done 457 ::close(this->socket()); 458 459 // were we externally suspended while we were waiting? 460 thread->check_and_wait_while_suspended(); 461 462 delete this; 463 } 464 465 466 // AttachListener functions 467 468 AttachOperation* AttachListener::dequeue() { 469 JavaThread* thread = JavaThread::current(); 470 ThreadBlockInVM tbivm(thread); 471 472 thread->set_suspend_equivalent(); 473 // cleared by handle_special_suspend_equivalent_condition() or 474 // java_suspend_self() via check_and_wait_while_suspended() 475 476 AttachOperation* op = AixAttachListener::dequeue(); 477 478 // were we externally suspended while we were waiting? 479 thread->check_and_wait_while_suspended(); 480 481 return op; 482 } 483 484 // Performs initialization at vm startup 485 // For AIX we remove any stale .java_pid file which could cause 486 // an attaching process to think we are ready to receive on the 487 // domain socket before we are properly initialized 488 489 void AttachListener::vm_start() { 490 char fn[UNIX_PATH_MAX]; 491 struct stat64 st; 492 int ret; 493 494 int n = snprintf(fn, UNIX_PATH_MAX, "%s/.java_pid%d", 495 os::get_temp_directory(), os::current_process_id()); 496 assert(n < (int)UNIX_PATH_MAX, "java_pid file name buffer overflow"); 497 498 RESTARTABLE(::stat64(fn, &st), ret); 499 if (ret == 0) { 500 ret = ::unlink(fn); 501 if (ret == -1) { 502 log_debug(attach)("Failed to remove stale attach pid file at %s", fn); 503 } 504 } 505 } 506 507 int AttachListener::pd_init() { 508 JavaThread* thread = JavaThread::current(); 509 ThreadBlockInVM tbivm(thread); 510 511 thread->set_suspend_equivalent(); 512 // cleared by handle_special_suspend_equivalent_condition() or 513 // java_suspend_self() via check_and_wait_while_suspended() 514 515 int ret_code = AixAttachListener::init(); 516 517 // were we externally suspended while we were waiting? 518 thread->check_and_wait_while_suspended(); 519 520 return ret_code; 521 } 522 523 bool AttachListener::check_socket_file() { 524 int ret; 525 struct stat64 st; 526 ret = stat64(AixAttachListener::path(), &st); 527 if (ret == -1) { // need to restart attach listener. 528 log_debug(attach)("Socket file %s does not exist - Restart Attach Listener", 529 AixAttachListener::path()); 530 531 listener_cleanup(); 532 533 // wait to terminate current attach listener instance... 534 while (AttachListener::transit_state(AL_INITIALIZING, 535 AL_NOT_INITIALIZED) != AL_NOT_INITIALIZED) { 536 os::naked_yield(); 537 } 538 is_init_trigger(); 539 return true; 540 } 541 return false; 542 } 543 544 // Attach Listener is started lazily except in the case when 545 // +ReduseSignalUsage is used 546 bool AttachListener::init_at_startup() { 547 if (ReduceSignalUsage) { 548 return true; 549 } else { 550 return false; 551 } 552 } 553 554 // If the file .attach_pid<pid> exists in the working directory 555 // or /tmp then this is the trigger to start the attach mechanism 556 bool AttachListener::is_init_trigger() { 557 if (init_at_startup() || is_initialized()) { 558 return false; // initialized at startup or already initialized 559 } 560 char fn[PATH_MAX + 1]; 561 int ret; 562 struct stat64 st; 563 sprintf(fn, ".attach_pid%d", os::current_process_id()); 564 RESTARTABLE(::stat64(fn, &st), ret); 565 if (ret == -1) { 566 log_trace(attach)("Failed to find attach file: %s, trying alternate", fn); 567 snprintf(fn, sizeof(fn), "%s/.attach_pid%d", 568 os::get_temp_directory(), os::current_process_id()); 569 RESTARTABLE(::stat64(fn, &st), ret); 570 if (ret == -1) { 571 log_debug(attach)("Failed to find attach file: %s", fn); 572 } 573 } 574 if (ret == 0) { 575 // simple check to avoid starting the attach mechanism when 576 // a bogus non-root user creates the file 577 if (os::Posix::matches_effective_uid_or_root(st.st_uid)) { 578 init(); 579 log_trace(attach)("Attach triggered by %s", fn); 580 return true; 581 } else { 582 log_debug(attach)("File %s has wrong user id %d (vs %d). Attach is not triggered", fn, st.st_uid, geteuid()); 583 } 584 } 585 return false; 586 } 587 588 // if VM aborts then remove listener 589 void AttachListener::abort() { 590 listener_cleanup(); 591 } 592 593 void AttachListener::pd_data_dump() { 594 os::signal_notify(SIGQUIT); 595 } 596 597 AttachOperationFunctionInfo* AttachListener::pd_find_operation(const char* n) { 598 return NULL; 599 } 600 601 jint AttachListener::pd_set_flag(AttachOperation* op, outputStream* out) { 602 out->print_cr("flag '%s' cannot be changed", op->arg(0)); 603 return JNI_ERR; 604 } 605 606 void AttachListener::pd_detachall() { 607 // Cleanup server socket to detach clients. 608 listener_cleanup(); 609 }