1 /* 2 * Copyright (c) 2005, 2018, 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 "memory/allocation.inline.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 <unistd.h> 34 #include <signal.h> 35 #include <sys/types.h> 36 #include <sys/socket.h> 37 #include <sys/un.h> 38 #include <sys/stat.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 Linux 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_PEERCRED 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 LinuxAttachOperation; 62 63 class LinuxAttachListener: 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 69 // the file descriptor for the listening socket 70 static int _listener; 71 72 static void set_path(char* path) { 73 if (path == NULL) { 74 _has_path = false; 75 } else { 76 strncpy(_path, path, UNIX_PATH_MAX); 77 _path[UNIX_PATH_MAX-1] = '\0'; 78 _has_path = true; 79 } 80 } 81 82 static void set_listener(int s) { _listener = s; } 83 84 // reads a request from the given connected socket 85 static LinuxAttachOperation* read_request(int s); 86 87 public: 88 enum { 89 ATTACH_PROTOCOL_VER = 1 // protocol version 90 }; 91 enum { 92 ATTACH_ERROR_BADVERSION = 101 // error codes 93 }; 94 95 // initialize the listener, returns 0 if okay 96 static int init(); 97 98 static char* path() { return _path; } 99 static bool has_path() { return _has_path; } 100 static int listener() { return _listener; } 101 102 // write the given buffer to a socket 103 static int write_fully(int s, char* buf, int len); 104 105 static LinuxAttachOperation* dequeue(); 106 }; 107 108 class LinuxAttachOperation: public AttachOperation { 109 private: 110 // the connection to the client 111 int _socket; 112 113 public: 114 void complete(jint res, bufferedStream* st); 115 116 void set_socket(int s) { _socket = s; } 117 int socket() const { return _socket; } 118 119 LinuxAttachOperation(char* name) : AttachOperation(name) { 120 set_socket(-1); 121 } 122 }; 123 124 // statics 125 char LinuxAttachListener::_path[UNIX_PATH_MAX]; 126 bool LinuxAttachListener::_has_path; 127 int LinuxAttachListener::_listener = -1; 128 129 // Supporting class to help split a buffer into individual components 130 class ArgumentIterator : public StackObj { 131 private: 132 char* _pos; 133 char* _end; 134 public: 135 ArgumentIterator(char* arg_buffer, size_t arg_size) { 136 _pos = arg_buffer; 137 _end = _pos + arg_size - 1; 138 } 139 char* next() { 140 if (*_pos == '\0') { 141 // advance the iterator if possible (null arguments) 142 if (_pos < _end) { 143 _pos += 1; 144 } 145 return NULL; 146 } 147 char* res = _pos; 148 char* next_pos = strchr(_pos, '\0'); 149 if (next_pos < _end) { 150 next_pos++; 151 } 152 _pos = next_pos; 153 return res; 154 } 155 }; 156 157 158 // atexit hook to stop listener and unlink the file that it is 159 // bound too. 160 extern "C" { 161 static void listener_cleanup() { 162 static int cleanup_done; 163 if (!cleanup_done) { 164 cleanup_done = 1; 165 int s = LinuxAttachListener::listener(); 166 if (s != -1) { 167 ::close(s); 168 } 169 if (LinuxAttachListener::has_path()) { 170 ::unlink(LinuxAttachListener::path()); 171 } 172 } 173 } 174 } 175 176 // Initialization - create a listener socket and bind it to a file 177 178 int LinuxAttachListener::init() { 179 char path[UNIX_PATH_MAX]; // socket file 180 char initial_path[UNIX_PATH_MAX]; // socket file during setup 181 int listener; // listener socket (file descriptor) 182 183 // register function to cleanup 184 ::atexit(listener_cleanup); 185 186 int n = snprintf(path, UNIX_PATH_MAX, "%s/.java_pid%d", 187 os::get_temp_directory(), os::current_process_id()); 188 if (n < (int)UNIX_PATH_MAX) { 189 n = snprintf(initial_path, UNIX_PATH_MAX, "%s.tmp", path); 190 } 191 if (n >= (int)UNIX_PATH_MAX) { 192 return -1; 193 } 194 195 // create the listener socket 196 listener = ::socket(PF_UNIX, SOCK_STREAM, 0); 197 if (listener == -1) { 198 return -1; 199 } 200 201 // bind socket 202 struct sockaddr_un addr; 203 memset((void *)&addr, 0, sizeof(addr)); 204 addr.sun_family = AF_UNIX; 205 strcpy(addr.sun_path, initial_path); 206 ::unlink(initial_path); 207 int res = ::bind(listener, (struct sockaddr*)&addr, sizeof(addr)); 208 if (res == -1) { 209 ::close(listener); 210 return -1; 211 } 212 213 // put in listen mode, set permissions, and rename into place 214 res = ::listen(listener, 5); 215 if (res == 0) { 216 RESTARTABLE(::chmod(initial_path, S_IREAD|S_IWRITE), res); 217 if (res == 0) { 218 // make sure the file is owned by the effective user and effective group 219 // e.g. the group could be inherited from the directory in case the s bit is set 220 RESTARTABLE(::chown(initial_path, geteuid(), getegid()), res); 221 if (res == 0) { 222 res = ::rename(initial_path, path); 223 } 224 } 225 } 226 if (res == -1) { 227 ::close(listener); 228 ::unlink(initial_path); 229 return -1; 230 } 231 set_path(path); 232 set_listener(listener); 233 234 return 0; 235 } 236 237 // Given a socket that is connected to a peer we read the request and 238 // create an AttachOperation. As the socket is blocking there is potential 239 // for a denial-of-service if the peer does not response. However this happens 240 // after the peer credentials have been checked and in the worst case it just 241 // means that the attach listener thread is blocked. 242 // 243 LinuxAttachOperation* LinuxAttachListener::read_request(int s) { 244 char ver_str[8]; 245 sprintf(ver_str, "%d", ATTACH_PROTOCOL_VER); 246 247 // The request is a sequence of strings so we first figure out the 248 // expected count and the maximum possible length of the request. 249 // The request is: 250 // <ver>0<cmd>0<arg>0<arg>0<arg>0 251 // where <ver> is the protocol version (1), <cmd> is the command 252 // name ("load", "datadump", ...), and <arg> is an argument 253 int expected_str_count = 2 + AttachOperation::arg_count_max; 254 const int max_len = (sizeof(ver_str) + 1) + (AttachOperation::name_length_max + 1) + 255 AttachOperation::arg_count_max*(AttachOperation::arg_length_max + 1); 256 257 char buf[max_len]; 258 int str_count = 0; 259 260 // Read until all (expected) strings have been read, the buffer is 261 // full, or EOF. 262 263 int off = 0; 264 int left = max_len; 265 266 do { 267 int n; 268 RESTARTABLE(read(s, buf+off, left), n); 269 assert(n <= left, "buffer was too small, impossible!"); 270 buf[max_len - 1] = '\0'; 271 if (n == -1) { 272 return NULL; // reset by peer or other error 273 } 274 if (n == 0) { 275 break; 276 } 277 for (int i=0; i<n; i++) { 278 if (buf[off+i] == 0) { 279 // EOS found 280 str_count++; 281 282 // The first string is <ver> so check it now to 283 // check for protocol mis-match 284 if (str_count == 1) { 285 if ((strlen(buf) != strlen(ver_str)) || 286 (atoi(buf) != ATTACH_PROTOCOL_VER)) { 287 char msg[32]; 288 sprintf(msg, "%d\n", ATTACH_ERROR_BADVERSION); 289 write_fully(s, msg, strlen(msg)); 290 return NULL; 291 } 292 } 293 } 294 } 295 off += n; 296 left -= n; 297 } while (left > 0 && str_count < expected_str_count); 298 299 if (str_count != expected_str_count) { 300 return NULL; // incomplete request 301 } 302 303 // parse request 304 305 ArgumentIterator args(buf, (max_len)-left); 306 307 // version already checked 308 char* v = args.next(); 309 310 char* name = args.next(); 311 if (name == NULL || strlen(name) > AttachOperation::name_length_max) { 312 return NULL; 313 } 314 315 LinuxAttachOperation* op = new LinuxAttachOperation(name); 316 317 for (int i=0; i<AttachOperation::arg_count_max; i++) { 318 char* arg = args.next(); 319 if (arg == NULL) { 320 op->set_arg(i, NULL); 321 } else { 322 if (strlen(arg) > AttachOperation::arg_length_max) { 323 delete op; 324 return NULL; 325 } 326 op->set_arg(i, arg); 327 } 328 } 329 330 op->set_socket(s); 331 return op; 332 } 333 334 335 // Dequeue an operation 336 // 337 // In the Linux implementation there is only a single operation and clients 338 // cannot queue commands (except at the socket level). 339 // 340 LinuxAttachOperation* LinuxAttachListener::dequeue() { 341 for (;;) { 342 int s; 343 344 // wait for client to connect 345 struct sockaddr addr; 346 socklen_t len = sizeof(addr); 347 RESTARTABLE(::accept(listener(), &addr, &len), s); 348 if (s == -1) { 349 return NULL; // log a warning? 350 } 351 352 // get the credentials of the peer and check the effective uid/guid 353 struct ucred cred_info; 354 socklen_t optlen = sizeof(cred_info); 355 if (::getsockopt(s, SOL_SOCKET, SO_PEERCRED, (void*)&cred_info, &optlen) == -1) { 356 log_debug(attach)("Failed to get socket option SO_PEERCRED"); 357 ::close(s); 358 continue; 359 } 360 361 if (!os::Posix::matches_effective_uid_and_gid_or_root(cred_info.uid, cred_info.gid)) { 362 log_debug(attach)("euid/egid check failed (%d/%d vs %d/%d)", 363 cred_info.uid, cred_info.gid, geteuid(), getegid()); 364 ::close(s); 365 continue; 366 } 367 368 // peer credential look okay so we read the request 369 LinuxAttachOperation* op = read_request(s); 370 if (op == NULL) { 371 ::close(s); 372 continue; 373 } else { 374 return op; 375 } 376 } 377 } 378 379 // write the given buffer to the socket 380 int LinuxAttachListener::write_fully(int s, char* buf, int len) { 381 do { 382 int n = ::write(s, buf, len); 383 if (n == -1) { 384 if (errno != EINTR) return -1; 385 } else { 386 buf += n; 387 len -= n; 388 } 389 } 390 while (len > 0); 391 return 0; 392 } 393 394 // Complete an operation by sending the operation result and any result 395 // output to the client. At this time the socket is in blocking mode so 396 // potentially we can block if there is a lot of data and the client is 397 // non-responsive. For most operations this is a non-issue because the 398 // default send buffer is sufficient to buffer everything. In the future 399 // if there are operations that involves a very big reply then it the 400 // socket could be made non-blocking and a timeout could be used. 401 402 void LinuxAttachOperation::complete(jint result, bufferedStream* st) { 403 JavaThread* thread = JavaThread::current(); 404 ThreadBlockInVM tbivm(thread); 405 406 thread->set_suspend_equivalent(); 407 // cleared by handle_special_suspend_equivalent_condition() or 408 // java_suspend_self() via check_and_wait_while_suspended() 409 410 // write operation result 411 char msg[32]; 412 sprintf(msg, "%d\n", result); 413 int rc = LinuxAttachListener::write_fully(this->socket(), msg, strlen(msg)); 414 415 // write any result data 416 if (rc == 0) { 417 LinuxAttachListener::write_fully(this->socket(), (char*) st->base(), st->size()); 418 ::shutdown(this->socket(), 2); 419 } 420 421 // done 422 ::close(this->socket()); 423 424 // were we externally suspended while we were waiting? 425 thread->check_and_wait_while_suspended(); 426 427 delete this; 428 } 429 430 431 // AttachListener functions 432 433 AttachOperation* AttachListener::dequeue() { 434 JavaThread* thread = JavaThread::current(); 435 ThreadBlockInVM tbivm(thread); 436 437 thread->set_suspend_equivalent(); 438 // cleared by handle_special_suspend_equivalent_condition() or 439 // java_suspend_self() via check_and_wait_while_suspended() 440 441 AttachOperation* op = LinuxAttachListener::dequeue(); 442 443 // were we externally suspended while we were waiting? 444 thread->check_and_wait_while_suspended(); 445 446 return op; 447 } 448 449 // Performs initialization at vm startup 450 // For Linux we remove any stale .java_pid file which could cause 451 // an attaching process to think we are ready to receive on the 452 // domain socket before we are properly initialized 453 454 void AttachListener::vm_start() { 455 char fn[UNIX_PATH_MAX]; 456 struct stat64 st; 457 int ret; 458 459 int n = snprintf(fn, UNIX_PATH_MAX, "%s/.java_pid%d", 460 os::get_temp_directory(), os::current_process_id()); 461 assert(n < (int)UNIX_PATH_MAX, "java_pid file name buffer overflow"); 462 463 RESTARTABLE(::stat64(fn, &st), ret); 464 if (ret == 0) { 465 ret = ::unlink(fn); 466 if (ret == -1) { 467 log_debug(attach)("Failed to remove stale attach pid file at %s", fn); 468 } 469 } 470 } 471 472 int AttachListener::pd_init() { 473 JavaThread* thread = JavaThread::current(); 474 ThreadBlockInVM tbivm(thread); 475 476 thread->set_suspend_equivalent(); 477 // cleared by handle_special_suspend_equivalent_condition() or 478 // java_suspend_self() via check_and_wait_while_suspended() 479 480 int ret_code = LinuxAttachListener::init(); 481 482 // were we externally suspended while we were waiting? 483 thread->check_and_wait_while_suspended(); 484 485 return ret_code; 486 } 487 488 // Attach Listener is started lazily except in the case when 489 // +ReduseSignalUsage is used 490 bool AttachListener::init_at_startup() { 491 if (ReduceSignalUsage) { 492 return true; 493 } else { 494 return false; 495 } 496 } 497 498 // If the file .attach_pid<pid> exists in the working directory 499 // or /tmp then this is the trigger to start the attach mechanism 500 bool AttachListener::is_init_trigger() { 501 if (init_at_startup() || is_initialized()) { 502 return false; // initialized at startup or already initialized 503 } 504 char fn[PATH_MAX + 1]; 505 int ret; 506 struct stat64 st; 507 sprintf(fn, ".attach_pid%d", os::current_process_id()); 508 RESTARTABLE(::stat64(fn, &st), ret); 509 if (ret == -1) { 510 log_trace(attach)("Failed to find attach file: %s, trying alternate", fn); 511 snprintf(fn, sizeof(fn), "%s/.attach_pid%d", 512 os::get_temp_directory(), os::current_process_id()); 513 RESTARTABLE(::stat64(fn, &st), ret); 514 if (ret == -1) { 515 log_debug(attach)("Failed to find attach file: %s", fn); 516 } 517 } 518 if (ret == 0) { 519 // simple check to avoid starting the attach mechanism when 520 // a bogus non-root user creates the file 521 if (os::Posix::matches_effective_uid_or_root(st.st_uid)) { 522 init(); 523 log_trace(attach)("Attach triggered by %s", fn); 524 return true; 525 } else { 526 log_debug(attach)("File %s has wrong user id %d (vs %d). Attach is not triggered", fn, st.st_uid, geteuid()); 527 } 528 } 529 return false; 530 } 531 532 // if VM aborts then remove listener 533 void AttachListener::abort() { 534 listener_cleanup(); 535 } 536 537 void AttachListener::pd_data_dump() { 538 os::signal_notify(SIGQUIT); 539 } 540 541 AttachOperationFunctionInfo* AttachListener::pd_find_operation(const char* n) { 542 return NULL; 543 } 544 545 jint AttachListener::pd_set_flag(AttachOperation* op, outputStream* out) { 546 out->print_cr("flag '%s' cannot be changed", op->arg(0)); 547 return JNI_ERR; 548 } 549 550 void AttachListener::pd_detachall() { 551 // do nothing for now 552 }