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