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 "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 void set_path(char* path) {
72 if (path == NULL) {
73 _has_path = false;
74 } else {
75 strncpy(_path, path, UNIX_PATH_MAX);
76 _path[UNIX_PATH_MAX-1] = '\0';
77 _has_path = true;
78 }
79 }
80
81 static void set_listener(int s) { _listener = s; }
82
83 // reads a request from the given connected socket
84 static BsdAttachOperation* read_request(int s);
85
86 public:
87 enum {
88 ATTACH_PROTOCOL_VER = 1 // protocol version
89 };
90 enum {
91 ATTACH_ERROR_BADVERSION = 101 // error codes
92 };
93
94 // initialize the listener, returns 0 if okay
95 static int init();
96
97 static char* path() { return _path; }
98 static bool has_path() { return _has_path; }
99 static int listener() { return _listener; }
100
101 // write the given buffer to a socket
102 static int write_fully(int s, char* buf, int len);
103
104 static BsdAttachOperation* dequeue();
105 };
106
107 class BsdAttachOperation: public AttachOperation {
108 private:
109 // the connection to the client
110 int _socket;
111
112 public:
113 void complete(jint res, bufferedStream* st);
114
115 void set_socket(int s) { _socket = s; }
116 int socket() const { return _socket; }
117
118 BsdAttachOperation(char* name) : AttachOperation(name) {
119 set_socket(-1);
120 }
121 };
122
123 // statics
124 char BsdAttachListener::_path[UNIX_PATH_MAX];
125 bool BsdAttachListener::_has_path;
126 int BsdAttachListener::_listener = -1;
127
128 // Supporting class to help split a buffer into individual components
129 class ArgumentIterator : public StackObj {
130 private:
131 char* _pos;
132 char* _end;
133 public:
134 ArgumentIterator(char* arg_buffer, size_t arg_size) {
135 _pos = arg_buffer;
136 _end = _pos + arg_size - 1;
137 }
138 char* next() {
139 if (*_pos == '\0') {
140 // advance the iterator if possible (null arguments)
141 if (_pos < _end) {
142 _pos += 1;
143 }
144 return NULL;
145 }
146 char* res = _pos;
147 char* next_pos = strchr(_pos, '\0');
148 if (next_pos < _end) {
149 next_pos++;
150 }
151 _pos = next_pos;
152 return res;
153 }
154 };
155
156
157 // atexit hook to stop listener and unlink the file that it is
158 // bound too.
159 extern "C" {
160 static void listener_cleanup() {
161 static int cleanup_done;
162 if (!cleanup_done) {
163 cleanup_done = 1;
164 int s = BsdAttachListener::listener();
165 if (s != -1) {
166 ::close(s);
167 }
168 if (BsdAttachListener::has_path()) {
169 ::unlink(BsdAttachListener::path());
170 }
171 }
172 }
173 }
174
175 // Initialization - create a listener socket and bind it to a file
176
177 int BsdAttachListener::init() {
178 char path[UNIX_PATH_MAX]; // socket file
179 char initial_path[UNIX_PATH_MAX]; // socket file during setup
180 int listener; // listener socket (file descriptor)
181
182 // register function to cleanup
183 ::atexit(listener_cleanup);
184
185 int n = snprintf(path, UNIX_PATH_MAX, "%s/.java_pid%d",
186 os::get_temp_directory(), os::current_process_id());
187 if (n < (int)UNIX_PATH_MAX) {
188 n = snprintf(initial_path, UNIX_PATH_MAX, "%s.tmp", path);
189 }
190 if (n >= (int)UNIX_PATH_MAX) {
191 return -1;
192 }
193
194 // create the listener socket
195 listener = ::socket(PF_UNIX, SOCK_STREAM, 0);
196 if (listener == -1) {
197 return -1;
198 }
199
200 // bind socket
201 struct sockaddr_un addr;
202 memset((void *)&addr, 0, sizeof(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 // e.g. default behavior on mac is that new files inherit the group of
219 // the directory that they are created in
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 BsdAttachOperation* BsdAttachListener::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 BsdAttachOperation* op = new BsdAttachOperation(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 Bsd implementation there is only a single operation and clients
338 // cannot queue commands (except at the socket level).
339 //
340 BsdAttachOperation* BsdAttachListener::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 uid_t puid;
354 gid_t pgid;
355 if (::getpeereid(s, &puid, &pgid) != 0) {
356 log_debug(attach)("Failed to get peer id");
357 ::close(s);
358 continue;
359 }
360
361 if (!os::Posix::matches_effective_uid_and_gid_or_root(puid, pgid)) {
362 log_debug(attach)("euid/egid check failed (%d/%d vs %d/%d)", puid, pgid,
363 geteuid(), getegid());
364 ::close(s);
365 continue;
366 }
367
368 // peer credential look okay so we read the request
369 BsdAttachOperation* 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 BsdAttachListener::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 BsdAttachOperation::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 = BsdAttachListener::write_fully(this->socket(), msg, strlen(msg));
414
415 // write any result data
416 if (rc == 0) {
417 BsdAttachListener::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 = BsdAttachListener::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 BSD 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 stat 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(::stat(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 = BsdAttachListener::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 stat st;
507 snprintf(fn, PATH_MAX + 1, "%s/.attach_pid%d",
508 os::get_temp_directory(), os::current_process_id());
509 RESTARTABLE(::stat(fn, &st), ret);
510 if (ret == -1) {
511 log_debug(attach)("Failed to find attach file: %s", fn);
512 }
513 if (ret == 0) {
514 // simple check to avoid starting the attach mechanism when
515 // a bogus non-root user creates the file
516 if (os::Posix::matches_effective_uid_or_root(st.st_uid)) {
517 init();
518 log_trace(attach)("Attach triggered by %s", fn);
519 return true;
520 } else {
521 log_debug(attach)("File %s has wrong user id %d (vs %d). Attach is not triggered", fn, st.st_uid, geteuid());
522 }
523 }
524 return false;
525 }
526
527 // if VM aborts then remove listener
528 void AttachListener::abort() {
529 listener_cleanup();
530 }
531
532 void AttachListener::pd_data_dump() {
533 os::signal_notify(SIGQUIT);
534 }
535
536 AttachOperationFunctionInfo* AttachListener::pd_find_operation(const char* n) {
537 return NULL;
538 }
539
540 jint AttachListener::pd_set_flag(AttachOperation* op, outputStream* out) {
541 out->print_cr("flag '%s' cannot be changed", op->arg(0));
542 return JNI_ERR;
543 }
544
545 void AttachListener::pd_detachall() {
546 // do nothing for now
547 }