1 /* 2 * Copyright (c) 2005, 2019, 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.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 Linux 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 LinuxAttachOperation; 60 61 class LinuxAttachListener: 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 bool _atexit_registered; 71 72 // reads a request from the given connected socket 73 static LinuxAttachOperation* read_request(int s); 74 75 public: 76 enum { 77 ATTACH_PROTOCOL_VER = 1 // protocol version 78 }; 79 enum { 80 ATTACH_ERROR_BADVERSION = 101 // error codes 81 }; 82 83 static void set_path(char* path) { 84 if (path == NULL) { 85 _path[0] = '\0'; 86 _has_path = false; 87 } else { 88 strncpy(_path, path, UNIX_PATH_MAX); 89 _path[UNIX_PATH_MAX-1] = '\0'; 90 _has_path = true; 91 } 92 } 93 94 static void set_listener(int s) { _listener = s; } 95 96 // initialize the listener, returns 0 if okay 97 static int init(); 98 99 static char* path() { return _path; } 100 static bool has_path() { return _has_path; } 101 static int listener() { return _listener; } 102 103 // write the given buffer to a socket 104 static int write_fully(int s, char* buf, int len); 105 106 static LinuxAttachOperation* dequeue(); 107 }; 108 109 class LinuxAttachOperation: public AttachOperation { 110 private: 111 // the connection to the client 112 int _socket; 113 114 public: 115 void complete(jint res, bufferedStream* st); 116 117 void set_socket(int s) { _socket = s; } 118 int socket() const { return _socket; } 119 120 LinuxAttachOperation(char* name) : AttachOperation(name) { 121 set_socket(-1); 122 } 123 }; 124 125 // statics 126 char LinuxAttachListener::_path[UNIX_PATH_MAX]; 127 bool LinuxAttachListener::_has_path; 128 int LinuxAttachListener::_listener = -1; 129 bool LinuxAttachListener::_atexit_registered = false; 130 131 // Supporting class to help split a buffer into individual components 132 class ArgumentIterator : public StackObj { 133 private: 134 char* _pos; 135 char* _end; 136 public: 137 ArgumentIterator(char* arg_buffer, size_t arg_size) { 138 _pos = arg_buffer; 139 _end = _pos + arg_size - 1; 140 } 141 char* next() { 142 if (*_pos == '\0') { 143 return NULL; 144 } 145 char* res = _pos; 146 char* next_pos = strchr(_pos, '\0'); 147 if (next_pos < _end) { 148 next_pos++; 149 } 150 _pos = next_pos; 151 return res; 152 } 153 }; 154 155 156 // atexit hook to stop listener and unlink the file that it is 157 // bound too. 158 extern "C" { 159 static void listener_cleanup() { 160 int s = LinuxAttachListener::listener(); 161 if (s != -1) { 162 LinuxAttachListener::set_listener(-1); 163 ::shutdown(s, SHUT_RDWR); 164 ::close(s); 165 } 166 if (LinuxAttachListener::has_path()) { 167 ::unlink(LinuxAttachListener::path()); 168 LinuxAttachListener::set_path(NULL); 169 } 170 } 171 } 172 173 // Initialization - create a listener socket and bind it to a file 174 175 int LinuxAttachListener::init() { 176 char path[UNIX_PATH_MAX]; // socket file 177 char initial_path[UNIX_PATH_MAX]; // socket file during setup 178 int listener; // listener socket (file descriptor) 179 180 // register function to cleanup 181 if (!_atexit_registered) { 182 _atexit_registered = true; 183 ::atexit(listener_cleanup); 184 } 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 addr.sun_family = AF_UNIX; 204 strcpy(addr.sun_path, initial_path); 205 ::unlink(initial_path); 206 int res = ::bind(listener, (struct sockaddr*)&addr, sizeof(addr)); 207 if (res == -1) { 208 ::close(listener); 209 return -1; 210 } 211 212 // put in listen mode, set permissions, and rename into place 213 res = ::listen(listener, 5); 214 if (res == 0) { 215 RESTARTABLE(::chmod(initial_path, S_IREAD|S_IWRITE), res); 216 if (res == 0) { 217 res = ::rename(initial_path, path); 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 LinuxAttachOperation* LinuxAttachListener::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 LinuxAttachOperation* op = new LinuxAttachOperation(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 Linux implementation there is only a single operation and clients 330 // cannot queue commands (except at the socket level). 331 // 332 LinuxAttachOperation* LinuxAttachListener::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 struct ucred cred_info; 347 socklen_t optlen = sizeof(cred_info); 348 if (::getsockopt(s, SOL_SOCKET, SO_PEERCRED, (void*)&cred_info, &optlen) == -1) { 349 ::close(s); 350 continue; 351 } 352 uid_t euid = geteuid(); 353 gid_t egid = getegid(); 354 355 if (cred_info.uid != euid || cred_info.gid != egid) { 356 ::close(s); 357 continue; 358 } 359 360 // peer credential look okay so we read the request 361 LinuxAttachOperation* 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 LinuxAttachListener::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 LinuxAttachOperation::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 = LinuxAttachListener::write_fully(this->socket(), msg, strlen(msg)); 406 407 // write any result data 408 if (rc == 0) { 409 LinuxAttachListener::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 = LinuxAttachListener::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 Linux 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 stat64 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(::stat64(fn, &st), ret); 457 if (ret == 0) { 458 ret = ::unlink(fn); 459 if (ret == -1) { 460 debug_only(warning("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 = LinuxAttachListener::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 bool AttachListener::check_socket_file() { 482 int ret; 483 struct stat64 st; 484 ret = stat64(LinuxAttachListener::path(), &st); 485 if (ret == -1) { // need to restart attach listener. 486 debug_only(warning("Socket file %s does not exist - Restart Attach Listener", 487 LinuxAttachListener::path())); 488 489 listener_cleanup(); 490 491 // wait to terminate current attach listener instance... 492 while (AttachListener::transit_state(AL_INITIALIZING, 493 AL_NOT_INITIALIZED) != AL_NOT_INITIALIZED) { 494 os::yield(); 495 } 496 return is_init_trigger(); 497 } 498 return false; 499 } 500 501 // Attach Listener is started lazily except in the case when 502 // +ReduseSignalUsage is used 503 bool AttachListener::init_at_startup() { 504 if (ReduceSignalUsage) { 505 return true; 506 } else { 507 return false; 508 } 509 } 510 511 // If the file .attach_pid<pid> exists in the working directory 512 // or /tmp then this is the trigger to start the attach mechanism 513 bool AttachListener::is_init_trigger() { 514 if (init_at_startup() || is_initialized()) { 515 return false; // initialized at startup or already initialized 516 } 517 char fn[PATH_MAX+1]; 518 sprintf(fn, ".attach_pid%d", os::current_process_id()); 519 int ret; 520 struct stat64 st; 521 RESTARTABLE(::stat64(fn, &st), ret); 522 if (ret == -1) { 523 snprintf(fn, sizeof(fn), "%s/.attach_pid%d", 524 os::get_temp_directory(), os::current_process_id()); 525 RESTARTABLE(::stat64(fn, &st), ret); 526 } 527 if (ret == 0) { 528 // simple check to avoid starting the attach mechanism when 529 // a bogus user creates the file 530 if (st.st_uid == geteuid()) { 531 init(); 532 return true; 533 } 534 } 535 return false; 536 } 537 538 // if VM aborts then remove listener 539 void AttachListener::abort() { 540 listener_cleanup(); 541 } 542 543 void AttachListener::pd_data_dump() { 544 os::signal_notify(SIGQUIT); 545 } 546 547 AttachOperationFunctionInfo* AttachListener::pd_find_operation(const char* n) { 548 return NULL; 549 } 550 551 jint AttachListener::pd_set_flag(AttachOperation* op, outputStream* out) { 552 out->print_cr("flag '%s' cannot be changed", op->arg(0)); 553 return JNI_ERR; 554 } 555 556 void AttachListener::pd_detachall() { 557 // do nothing for now 558 }