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 Bsd 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 BsdAttachOperation;
60
61 class BsdAttachListener: 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 BsdAttachOperation* 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 BsdAttachOperation* dequeue();
107 };
108
109 class BsdAttachOperation: 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 BsdAttachOperation(char* name) : AttachOperation(name) {
121 set_socket(-1);
122 }
123 };
124
125 // statics
126 char BsdAttachListener::_path[UNIX_PATH_MAX];
127 bool BsdAttachListener::_has_path;
128 int BsdAttachListener::_listener = -1;
129 bool BsdAttachListener::_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 = BsdAttachListener::listener();
161 if (s != -1) {
162 BsdAttachListener::set_listener(-1);
163 ::shutdown(s, SHUT_RDWR);
164 ::close(s);
165 }
166 if (BsdAttachListener::has_path()) {
167 ::unlink(BsdAttachListener::path());
168 BsdAttachListener::set_path(NULL);
169 }
170 }
171 }
172
173 // Initialization - create a listener socket and bind it to a file
174
175 int BsdAttachListener::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 // make sure the file is owned by the effective user and effective group
218 // (this is the default on linux, but not on mac os)
219 RESTARTABLE(::chown(initial_path, geteuid(), getegid()), res);
220 if (res == 0) {
221 res = ::rename(initial_path, path);
222 }
223 }
224 }
225 if (res == -1) {
226 ::close(listener);
227 ::unlink(initial_path);
228 return -1;
229 }
230 set_path(path);
231 set_listener(listener);
232
233 return 0;
234 }
235
236 // Given a socket that is connected to a peer we read the request and
237 // create an AttachOperation. As the socket is blocking there is potential
238 // for a denial-of-service if the peer does not response. However this happens
239 // after the peer credentials have been checked and in the worst case it just
240 // means that the attach listener thread is blocked.
241 //
242 BsdAttachOperation* BsdAttachListener::read_request(int s) {
243 char ver_str[8];
244 sprintf(ver_str, "%d", ATTACH_PROTOCOL_VER);
245
246 // The request is a sequence of strings so we first figure out the
247 // expected count and the maximum possible length of the request.
248 // The request is:
249 // <ver>0<cmd>0<arg>0<arg>0<arg>0
250 // where <ver> is the protocol version (1), <cmd> is the command
251 // name ("load", "datadump", ...), and <arg> is an argument
252 int expected_str_count = 2 + AttachOperation::arg_count_max;
253 const int max_len = (sizeof(ver_str) + 1) + (AttachOperation::name_length_max + 1) +
254 AttachOperation::arg_count_max*(AttachOperation::arg_length_max + 1);
255
256 char buf[max_len];
257 int str_count = 0;
258
259 // Read until all (expected) strings have been read, the buffer is
260 // full, or EOF.
261
262 int off = 0;
263 int left = max_len;
264
265 do {
266 int n;
267 RESTARTABLE(read(s, buf+off, left), n);
268 if (n == -1) {
269 return NULL; // reset by peer or other error
270 }
271 if (n == 0) {
272 break;
273 }
274 for (int i=0; i<n; i++) {
275 if (buf[off+i] == 0) {
276 // EOS found
277 str_count++;
278
279 // The first string is <ver> so check it now to
280 // check for protocol mis-match
281 if (str_count == 1) {
282 if ((strlen(buf) != strlen(ver_str)) ||
283 (atoi(buf) != ATTACH_PROTOCOL_VER)) {
284 char msg[32];
285 sprintf(msg, "%d\n", ATTACH_ERROR_BADVERSION);
286 write_fully(s, msg, strlen(msg));
287 return NULL;
288 }
289 }
290 }
291 }
292 off += n;
293 left -= n;
294 } while (left > 0 && str_count < expected_str_count);
295
296 if (str_count != expected_str_count) {
297 return NULL; // incomplete request
298 }
299
300 // parse request
301
302 ArgumentIterator args(buf, (max_len)-left);
303
304 // version already checked
305 char* v = args.next();
306
307 char* name = args.next();
308 if (name == NULL || strlen(name) > AttachOperation::name_length_max) {
309 return NULL;
310 }
311
312 BsdAttachOperation* op = new BsdAttachOperation(name);
313
314 for (int i=0; i<AttachOperation::arg_count_max; i++) {
315 char* arg = args.next();
316 if (arg == NULL) {
317 op->set_arg(i, NULL);
318 } else {
319 if (strlen(arg) > AttachOperation::arg_length_max) {
320 delete op;
321 return NULL;
322 }
323 op->set_arg(i, arg);
324 }
325 }
326
327 op->set_socket(s);
328 return op;
329 }
330
331
332 // Dequeue an operation
333 //
334 // In the Bsd implementation there is only a single operation and clients
335 // cannot queue commands (except at the socket level).
336 //
337 BsdAttachOperation* BsdAttachListener::dequeue() {
338 for (;;) {
339 int s;
340
341 // wait for client to connect
342 struct sockaddr addr;
343 socklen_t len = sizeof(addr);
344 RESTARTABLE(::accept(listener(), &addr, &len), s);
345 if (s == -1) {
346 return NULL; // log a warning?
347 }
348
349 // get the credentials of the peer and check the effective uid/guid
350 // - check with jeff on this.
351 uid_t puid;
352 gid_t pgid;
353 if (::getpeereid(s, &puid, &pgid) != 0) {
354 ::close(s);
355 continue;
356 }
357 uid_t euid = geteuid();
358 gid_t egid = getegid();
359
360 if (puid != euid || pgid != egid) {
361 ::close(s);
362 continue;
363 }
364
365 // peer credential look okay so we read the request
366 BsdAttachOperation* op = read_request(s);
367 if (op == NULL) {
368 ::close(s);
369 continue;
370 } else {
371 return op;
372 }
373 }
374 }
375
376 // write the given buffer to the socket
377 int BsdAttachListener::write_fully(int s, char* buf, int len) {
378 do {
379 int n = ::write(s, buf, len);
380 if (n == -1) {
381 if (errno != EINTR) return -1;
382 } else {
383 buf += n;
384 len -= n;
385 }
386 }
387 while (len > 0);
388 return 0;
389 }
390
391 // Complete an operation by sending the operation result and any result
392 // output to the client. At this time the socket is in blocking mode so
393 // potentially we can block if there is a lot of data and the client is
394 // non-responsive. For most operations this is a non-issue because the
395 // default send buffer is sufficient to buffer everything. In the future
396 // if there are operations that involves a very big reply then it the
397 // socket could be made non-blocking and a timeout could be used.
398
399 void BsdAttachOperation::complete(jint result, bufferedStream* st) {
400 JavaThread* thread = JavaThread::current();
401 ThreadBlockInVM tbivm(thread);
402
403 thread->set_suspend_equivalent();
404 // cleared by handle_special_suspend_equivalent_condition() or
405 // java_suspend_self() via check_and_wait_while_suspended()
406
407 // write operation result
408 char msg[32];
409 sprintf(msg, "%d\n", result);
410 int rc = BsdAttachListener::write_fully(this->socket(), msg, strlen(msg));
411
412 // write any result data
413 if (rc == 0) {
414 BsdAttachListener::write_fully(this->socket(), (char*) st->base(), st->size());
415 ::shutdown(this->socket(), 2);
416 }
417
418 // done
419 ::close(this->socket());
420
421 // were we externally suspended while we were waiting?
422 thread->check_and_wait_while_suspended();
423
424 delete this;
425 }
426
427
428 // AttachListener functions
429
430 AttachOperation* AttachListener::dequeue() {
431 JavaThread* thread = JavaThread::current();
432 ThreadBlockInVM tbivm(thread);
433
434 thread->set_suspend_equivalent();
435 // cleared by handle_special_suspend_equivalent_condition() or
436 // java_suspend_self() via check_and_wait_while_suspended()
437
438 AttachOperation* op = BsdAttachListener::dequeue();
439
440 // were we externally suspended while we were waiting?
441 thread->check_and_wait_while_suspended();
442
443 return op;
444 }
445
446
447 // Performs initialization at vm startup
448 // For BSD we remove any stale .java_pid file which could cause
449 // an attaching process to think we are ready to receive on the
450 // domain socket before we are properly initialized
451
452 void AttachListener::vm_start() {
453 char fn[UNIX_PATH_MAX];
454 struct stat st;
455 int ret;
456
457 int n = snprintf(fn, UNIX_PATH_MAX, "%s/.java_pid%d",
458 os::get_temp_directory(), os::current_process_id());
459 assert(n < (int)UNIX_PATH_MAX, "java_pid file name buffer overflow");
460
461 RESTARTABLE(::stat(fn, &st), ret);
462 if (ret == 0) {
463 ret = ::unlink(fn);
464 if (ret == -1) {
465 debug_only(warning("failed to remove stale attach pid file at %s", fn));
466 }
467 }
468 }
469
470 int AttachListener::pd_init() {
471 JavaThread* thread = JavaThread::current();
472 ThreadBlockInVM tbivm(thread);
473
474 thread->set_suspend_equivalent();
475 // cleared by handle_special_suspend_equivalent_condition() or
476 // java_suspend_self() via check_and_wait_while_suspended()
477
478 int ret_code = BsdAttachListener::init();
479
480 // were we externally suspended while we were waiting?
481 thread->check_and_wait_while_suspended();
482
483 return ret_code;
484 }
485
486 bool AttachListener::check_socket_file() {
487 int ret;
488 struct stat st;
489 ret = stat(BsdAttachListener::path(), &st);
490 if (ret == -1) { // need to restart attach listener.
491 debug_only(warning("Socket file %s does not exist - Restart Attach Listener",
492 BsdAttachListener::path()));
493
494 listener_cleanup();
495
496 // wait to terminate current attach listener instance...
497
498 while (AttachListener::transit_state(AL_INITIALIZING,
499
500 AL_NOT_INITIALIZED) != AL_NOT_INITIALIZED) {
501 os::yield();
502 }
503 return is_init_trigger();
504 }
505 return false;
506 }
507
508 // Attach Listener is started lazily except in the case when
509 // +ReduseSignalUsage is used
510 bool AttachListener::init_at_startup() {
511 if (ReduceSignalUsage) {
512 return true;
513 } else {
514 return false;
515 }
516 }
517
518 // If the file .attach_pid<pid> exists in the working directory
519 // or /tmp then this is the trigger to start the attach mechanism
520 bool AttachListener::is_init_trigger() {
521 if (init_at_startup() || is_initialized()) {
522 return false; // initialized at startup or already initialized
523 }
524 char path[PATH_MAX + 1];
525 int ret;
526 struct stat st;
527
528 snprintf(path, PATH_MAX + 1, "%s/.attach_pid%d",
529 os::get_temp_directory(), os::current_process_id());
530 RESTARTABLE(::stat(path, &st), ret);
531 if (ret == 0) {
532 // simple check to avoid starting the attach mechanism when
533 // a bogus user creates the file
534 if (st.st_uid == geteuid()) {
535 init();
536 return true;
537 }
538 }
539 return false;
540 }
541
542 // if VM aborts then remove listener
543 void AttachListener::abort() {
544 listener_cleanup();
545 }
546
547 void AttachListener::pd_data_dump() {
548 os::signal_notify(SIGQUIT);
549 }
550
551 AttachOperationFunctionInfo* AttachListener::pd_find_operation(const char* n) {
552 return NULL;
553 }
554
555 jint AttachListener::pd_set_flag(AttachOperation* op, outputStream* out) {
556 out->print_cr("flag '%s' cannot be changed", op->arg(0));
557 return JNI_ERR;
558 }
559
560 void AttachListener::pd_detachall() {
561 // do nothing for now
562 }