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 "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 bool _atexit_registered;
72
73 // reads a request from the given connected socket
74 static BsdAttachOperation* read_request(int s);
75
76 public:
77 enum {
78 ATTACH_PROTOCOL_VER = 1 // protocol version
79 };
80 enum {
81 ATTACH_ERROR_BADVERSION = 101 // error codes
82 };
83
84 static void set_path(char* path) {
85 if (path == NULL) {
86 _path[0] = '\0';
87 _has_path = false;
88 } else {
89 strncpy(_path, path, UNIX_PATH_MAX);
90 _path[UNIX_PATH_MAX-1] = '\0';
91 _has_path = true;
92 }
93 }
94
95 static void set_listener(int s) { _listener = s; }
96
97 // initialize the listener, returns 0 if okay
98 static int init();
99
100 static char* path() { return _path; }
101 static bool has_path() { return _has_path; }
102 static int listener() { return _listener; }
103
104 // write the given buffer to a socket
105 static int write_fully(int s, char* buf, int len);
106
107 static BsdAttachOperation* dequeue();
108 };
109
110 class BsdAttachOperation: public AttachOperation {
111 private:
112 // the connection to the client
113 int _socket;
114
115 public:
116 void complete(jint res, bufferedStream* st);
117
118 void set_socket(int s) { _socket = s; }
119 int socket() const { return _socket; }
120
121 BsdAttachOperation(char* name) : AttachOperation(name) {
122 set_socket(-1);
123 }
124 };
125
126 // statics
127 char BsdAttachListener::_path[UNIX_PATH_MAX];
128 bool BsdAttachListener::_has_path;
129 int BsdAttachListener::_listener = -1;
130 bool BsdAttachListener::_atexit_registered = false;
131
132 // Supporting class to help split a buffer into individual components
133 class ArgumentIterator : public StackObj {
134 private:
135 char* _pos;
136 char* _end;
137 public:
138 ArgumentIterator(char* arg_buffer, size_t arg_size) {
139 _pos = arg_buffer;
140 _end = _pos + arg_size - 1;
141 }
142 char* next() {
143 if (*_pos == '\0') {
144 // advance the iterator if possible (null arguments)
145 if (_pos < _end) {
146 _pos += 1;
147 }
148 return NULL;
149 }
150 char* res = _pos;
151 char* next_pos = strchr(_pos, '\0');
152 if (next_pos < _end) {
153 next_pos++;
154 }
155 _pos = next_pos;
156 return res;
157 }
158 };
159
160
161 // atexit hook to stop listener and unlink the file that it is
162 // bound too.
163 extern "C" {
164 static void listener_cleanup() {
165 int s = BsdAttachListener::listener();
166 if (s != -1) {
167 BsdAttachListener::set_listener(-1);
168 ::shutdown(s, SHUT_RDWR);
169 ::close(s);
170 }
171 if (BsdAttachListener::has_path()) {
172 ::unlink(BsdAttachListener::path());
173 BsdAttachListener::set_path(NULL);
174 }
175 }
176 }
177
178 // Initialization - create a listener socket and bind it to a file
179
180 int BsdAttachListener::init() {
181 char path[UNIX_PATH_MAX]; // socket file
182 char initial_path[UNIX_PATH_MAX]; // socket file during setup
183 int listener; // listener socket (file descriptor)
184
185 // register function to cleanup
186 if (!_atexit_registered) {
187 _atexit_registered = true;
188 ::atexit(listener_cleanup);
189 }
190
191 int n = snprintf(path, UNIX_PATH_MAX, "%s/.java_pid%d",
192 os::get_temp_directory(), os::current_process_id());
193 if (n < (int)UNIX_PATH_MAX) {
194 n = snprintf(initial_path, UNIX_PATH_MAX, "%s.tmp", path);
195 }
196 if (n >= (int)UNIX_PATH_MAX) {
197 return -1;
198 }
199
200 // create the listener socket
201 listener = ::socket(PF_UNIX, SOCK_STREAM, 0);
202 if (listener == -1) {
203 return -1;
204 }
205
206 // bind socket
207 struct sockaddr_un addr;
208 memset((void *)&addr, 0, sizeof(addr));
209 addr.sun_family = AF_UNIX;
210 strcpy(addr.sun_path, initial_path);
211 ::unlink(initial_path);
212 int res = ::bind(listener, (struct sockaddr*)&addr, sizeof(addr));
213 if (res == -1) {
214 ::close(listener);
215 return -1;
216 }
217
218 // put in listen mode, set permissions, and rename into place
219 res = ::listen(listener, 5);
220 if (res == 0) {
221 RESTARTABLE(::chmod(initial_path, S_IREAD|S_IWRITE), res);
222 if (res == 0) {
223 // make sure the file is owned by the effective user and effective group
224 // e.g. default behavior on mac is that new files inherit the group of
225 // the directory that they are created in
226 RESTARTABLE(::chown(initial_path, geteuid(), getegid()), res);
227 if (res == 0) {
228 res = ::rename(initial_path, path);
229 }
230 }
231 }
232 if (res == -1) {
233 ::close(listener);
234 ::unlink(initial_path);
235 return -1;
236 }
237 set_path(path);
238 set_listener(listener);
239
240 return 0;
241 }
242
243 // Given a socket that is connected to a peer we read the request and
244 // create an AttachOperation. As the socket is blocking there is potential
245 // for a denial-of-service if the peer does not response. However this happens
246 // after the peer credentials have been checked and in the worst case it just
247 // means that the attach listener thread is blocked.
248 //
249 BsdAttachOperation* BsdAttachListener::read_request(int s) {
250 char ver_str[8];
251 sprintf(ver_str, "%d", ATTACH_PROTOCOL_VER);
252
253 // The request is a sequence of strings so we first figure out the
254 // expected count and the maximum possible length of the request.
255 // The request is:
256 // <ver>0<cmd>0<arg>0<arg>0<arg>0
257 // where <ver> is the protocol version (1), <cmd> is the command
258 // name ("load", "datadump", ...), and <arg> is an argument
259 int expected_str_count = 2 + AttachOperation::arg_count_max;
260 const int max_len = (sizeof(ver_str) + 1) + (AttachOperation::name_length_max + 1) +
261 AttachOperation::arg_count_max*(AttachOperation::arg_length_max + 1);
262
263 char buf[max_len];
264 int str_count = 0;
265
266 // Read until all (expected) strings have been read, the buffer is
267 // full, or EOF.
268
269 int off = 0;
270 int left = max_len;
271
272 do {
273 int n;
274 RESTARTABLE(read(s, buf+off, left), n);
275 assert(n <= left, "buffer was too small, impossible!");
276 buf[max_len - 1] = '\0';
277 if (n == -1) {
278 return NULL; // reset by peer or other error
279 }
280 if (n == 0) {
281 break;
282 }
283 for (int i=0; i<n; i++) {
284 if (buf[off+i] == 0) {
285 // EOS found
286 str_count++;
287
288 // The first string is <ver> so check it now to
289 // check for protocol mis-match
290 if (str_count == 1) {
291 if ((strlen(buf) != strlen(ver_str)) ||
292 (atoi(buf) != ATTACH_PROTOCOL_VER)) {
293 char msg[32];
294 sprintf(msg, "%d\n", ATTACH_ERROR_BADVERSION);
295 write_fully(s, msg, strlen(msg));
296 return NULL;
297 }
298 }
299 }
300 }
301 off += n;
302 left -= n;
303 } while (left > 0 && str_count < expected_str_count);
304
305 if (str_count != expected_str_count) {
306 return NULL; // incomplete request
307 }
308
309 // parse request
310
311 ArgumentIterator args(buf, (max_len)-left);
312
313 // version already checked
314 char* v = args.next();
315
316 char* name = args.next();
317 if (name == NULL || strlen(name) > AttachOperation::name_length_max) {
318 return NULL;
319 }
320
321 BsdAttachOperation* op = new BsdAttachOperation(name);
322
323 for (int i=0; i<AttachOperation::arg_count_max; i++) {
324 char* arg = args.next();
325 if (arg == NULL) {
326 op->set_arg(i, NULL);
327 } else {
328 if (strlen(arg) > AttachOperation::arg_length_max) {
329 delete op;
330 return NULL;
331 }
332 op->set_arg(i, arg);
333 }
334 }
335
336 op->set_socket(s);
337 return op;
338 }
339
340
341 // Dequeue an operation
342 //
343 // In the Bsd implementation there is only a single operation and clients
344 // cannot queue commands (except at the socket level).
345 //
346 BsdAttachOperation* BsdAttachListener::dequeue() {
347 for (;;) {
348 int s;
349
350 // wait for client to connect
351 struct sockaddr addr;
352 socklen_t len = sizeof(addr);
353 RESTARTABLE(::accept(listener(), &addr, &len), s);
354 if (s == -1) {
355 return NULL; // log a warning?
356 }
357
358 // get the credentials of the peer and check the effective uid/guid
359 uid_t puid;
360 gid_t pgid;
361 if (::getpeereid(s, &puid, &pgid) != 0) {
362 log_debug(attach)("Failed to get peer id");
363 ::close(s);
364 continue;
365 }
366
367 if (!os::Posix::matches_effective_uid_and_gid_or_root(puid, pgid)) {
368 log_debug(attach)("euid/egid check failed (%d/%d vs %d/%d)", puid, pgid,
369 geteuid(), getegid());
370 ::close(s);
371 continue;
372 }
373
374 // peer credential look okay so we read the request
375 BsdAttachOperation* op = read_request(s);
376 if (op == NULL) {
377 ::close(s);
378 continue;
379 } else {
380 return op;
381 }
382 }
383 }
384
385 // write the given buffer to the socket
386 int BsdAttachListener::write_fully(int s, char* buf, int len) {
387 do {
388 int n = ::write(s, buf, len);
389 if (n == -1) {
390 if (errno != EINTR) return -1;
391 } else {
392 buf += n;
393 len -= n;
394 }
395 }
396 while (len > 0);
397 return 0;
398 }
399
400 // Complete an operation by sending the operation result and any result
401 // output to the client. At this time the socket is in blocking mode so
402 // potentially we can block if there is a lot of data and the client is
403 // non-responsive. For most operations this is a non-issue because the
404 // default send buffer is sufficient to buffer everything. In the future
405 // if there are operations that involves a very big reply then it the
406 // socket could be made non-blocking and a timeout could be used.
407
408 void BsdAttachOperation::complete(jint result, bufferedStream* st) {
409 JavaThread* thread = JavaThread::current();
410 ThreadBlockInVM tbivm(thread);
411
412 thread->set_suspend_equivalent();
413 // cleared by handle_special_suspend_equivalent_condition() or
414 // java_suspend_self() via check_and_wait_while_suspended()
415
416 // write operation result
417 char msg[32];
418 sprintf(msg, "%d\n", result);
419 int rc = BsdAttachListener::write_fully(this->socket(), msg, strlen(msg));
420
421 // write any result data
422 if (rc == 0) {
423 BsdAttachListener::write_fully(this->socket(), (char*) st->base(), st->size());
424 ::shutdown(this->socket(), 2);
425 }
426
427 // done
428 ::close(this->socket());
429
430 // were we externally suspended while we were waiting?
431 thread->check_and_wait_while_suspended();
432
433 delete this;
434 }
435
436
437 // AttachListener functions
438
439 AttachOperation* AttachListener::dequeue() {
440 JavaThread* thread = JavaThread::current();
441 ThreadBlockInVM tbivm(thread);
442
443 thread->set_suspend_equivalent();
444 // cleared by handle_special_suspend_equivalent_condition() or
445 // java_suspend_self() via check_and_wait_while_suspended()
446
447 AttachOperation* op = BsdAttachListener::dequeue();
448
449 // were we externally suspended while we were waiting?
450 thread->check_and_wait_while_suspended();
451
452 return op;
453 }
454
455 // Performs initialization at vm startup
456 // For BSD we remove any stale .java_pid file which could cause
457 // an attaching process to think we are ready to receive on the
458 // domain socket before we are properly initialized
459
460 void AttachListener::vm_start() {
461 char fn[UNIX_PATH_MAX];
462 struct stat st;
463 int ret;
464
465 int n = snprintf(fn, UNIX_PATH_MAX, "%s/.java_pid%d",
466 os::get_temp_directory(), os::current_process_id());
467 assert(n < (int)UNIX_PATH_MAX, "java_pid file name buffer overflow");
468
469 RESTARTABLE(::stat(fn, &st), ret);
470 if (ret == 0) {
471 ret = ::unlink(fn);
472 if (ret == -1) {
473 log_debug(attach)("Failed to remove stale attach pid file at %s", fn);
474 }
475 }
476 }
477
478 int AttachListener::pd_init() {
479 JavaThread* thread = JavaThread::current();
480 ThreadBlockInVM tbivm(thread);
481
482 thread->set_suspend_equivalent();
483 // cleared by handle_special_suspend_equivalent_condition() or
484 // java_suspend_self() via check_and_wait_while_suspended()
485
486 int ret_code = BsdAttachListener::init();
487
488 // were we externally suspended while we were waiting?
489 thread->check_and_wait_while_suspended();
490
491 return ret_code;
492 }
493
494 bool AttachListener::check_socket_file() {
495 int ret;
496 struct stat st;
497 ret = stat(BsdAttachListener::path(), &st);
498 if (ret == -1) { // need to restart attach listener.
499 log_debug(attach)("Socket file %s does not exist - Restart Attach Listener",
500 BsdAttachListener::path());
501
502 listener_cleanup();
503
504 // wait to terminate current attach listener instance...
505
506 while (AttachListener::transit_state(AL_INITIALIZING,
507
508 AL_NOT_INITIALIZED) != AL_NOT_INITIALIZED) {
509 os::naked_yield();
510 }
511 is_init_trigger();
512 return true;
513 }
514 return false;
515 }
516
517 // Attach Listener is started lazily except in the case when
518 // +ReduseSignalUsage is used
519 bool AttachListener::init_at_startup() {
520 if (ReduceSignalUsage) {
521 return true;
522 } else {
523 return false;
524 }
525 }
526
527 // If the file .attach_pid<pid> exists in the working directory
528 // or /tmp then this is the trigger to start the attach mechanism
529 bool AttachListener::is_init_trigger() {
530 if (init_at_startup() || is_initialized()) {
531 return false; // initialized at startup or already initialized
532 }
533 char fn[PATH_MAX + 1];
534 int ret;
535 struct stat st;
536 snprintf(fn, PATH_MAX + 1, "%s/.attach_pid%d",
537 os::get_temp_directory(), os::current_process_id());
538 RESTARTABLE(::stat(fn, &st), ret);
539 if (ret == -1) {
540 log_debug(attach)("Failed to find attach file: %s", fn);
541 }
542 if (ret == 0) {
543 // simple check to avoid starting the attach mechanism when
544 // a bogus non-root user creates the file
545 if (os::Posix::matches_effective_uid_or_root(st.st_uid)) {
546 init();
547 log_trace(attach)("Attach triggered by %s", fn);
548 return true;
549 } else {
550 log_debug(attach)("File %s has wrong user id %d (vs %d). Attach is not triggered", fn, st.st_uid, geteuid());
551 }
552 }
553 return false;
554 }
555
556 // if VM aborts then remove listener
557 void AttachListener::abort() {
558 listener_cleanup();
559 }
560
561 void AttachListener::pd_data_dump() {
562 os::signal_notify(SIGQUIT);
563 }
564
565 AttachOperationFunctionInfo* AttachListener::pd_find_operation(const char* n) {
566 return NULL;
567 }
568
569 jint AttachListener::pd_set_flag(AttachOperation* op, outputStream* out) {
570 out->print_cr("flag '%s' cannot be changed", op->arg(0));
571 return JNI_ERR;
572 }
573
574 void AttachListener::pd_detachall() {
575 // do nothing for now
576 }