1 // Copyright (c) 2010 Google Inc.
2 // All rights reserved.
3 //
4 // Redistribution and use in source and binary forms, with or without
5 // modification, are permitted provided that the following conditions are
6 // met:
7 //
8 // * Redistributions of source code must retain the above copyright
9 // notice, this list of conditions and the following disclaimer.
10 // * Redistributions in binary form must reproduce the above
11 // copyright notice, this list of conditions and the following disclaimer
12 // in the documentation and/or other materials provided with the
13 // distribution.
14 // * Neither the name of Google Inc. nor the names of its
15 // contributors may be used to endorse or promote products derived from
16 // this software without specific prior written permission.
17 //
18 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
19 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
20 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
21 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
22 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
23 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
24 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
25 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
26 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
27 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
28 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
29
30 #include <assert.h>
31 #include <dirent.h>
32 #include <fcntl.h>
33 #include <limits.h>
34 #include <poll.h>
35 #include <stdio.h>
36 #include <string.h>
37 #include <sys/socket.h>
38 #include <sys/stat.h>
39 #include <sys/types.h>
40 #include <unistd.h>
41
42 #include <vector>
43
44 #include "client/linux/crash_generation/crash_generation_server.h"
45 #include "client/linux/crash_generation/client_info.h"
46 #include "client/linux/handler/exception_handler.h"
47 #include "client/linux/minidump_writer/minidump_writer.h"
48 #include "common/linux/eintr_wrapper.h"
49 #include "common/linux/guid_creator.h"
50 #include "common/linux/safe_readlink.h"
51
52 static const char kCommandQuit = 'x';
53
54 namespace google_breakpad {
55
CrashGenerationServer(const int listen_fd,OnClientDumpRequestCallback dump_callback,void * dump_context,OnClientExitingCallback exit_callback,void * exit_context,bool generate_dumps,const string * dump_path)56 CrashGenerationServer::CrashGenerationServer(
57 const int listen_fd,
58 OnClientDumpRequestCallback dump_callback,
59 void* dump_context,
60 OnClientExitingCallback exit_callback,
61 void* exit_context,
62 bool generate_dumps,
63 const string* dump_path) :
64 server_fd_(listen_fd),
65 dump_callback_(dump_callback),
66 dump_context_(dump_context),
67 exit_callback_(exit_callback),
68 exit_context_(exit_context),
69 generate_dumps_(generate_dumps),
70 started_(false)
71 {
72 if (dump_path)
73 dump_dir_ = *dump_path;
74 else
75 dump_dir_ = "/tmp";
76 }
77
~CrashGenerationServer()78 CrashGenerationServer::~CrashGenerationServer()
79 {
80 if (started_)
81 Stop();
82 }
83
84 bool
Start()85 CrashGenerationServer::Start()
86 {
87 if (started_ || 0 > server_fd_)
88 return false;
89
90 int control_pipe[2];
91 if (pipe(control_pipe))
92 return false;
93
94 if (fcntl(control_pipe[0], F_SETFD, FD_CLOEXEC))
95 return false;
96 if (fcntl(control_pipe[1], F_SETFD, FD_CLOEXEC))
97 return false;
98
99 if (fcntl(control_pipe[0], F_SETFL, O_NONBLOCK))
100 return false;
101
102 control_pipe_in_ = control_pipe[0];
103 control_pipe_out_ = control_pipe[1];
104
105 if (pthread_create(&thread_, NULL,
106 ThreadMain, reinterpret_cast<void*>(this)))
107 return false;
108
109 started_ = true;
110 return true;
111 }
112
113 void
Stop()114 CrashGenerationServer::Stop()
115 {
116 assert(pthread_self() != thread_);
117
118 if (!started_)
119 return;
120
121 HANDLE_EINTR(write(control_pipe_out_, &kCommandQuit, 1));
122
123 void* dummy;
124 pthread_join(thread_, &dummy);
125
126 started_ = false;
127 }
128
129 //static
130 bool
CreateReportChannel(int * server_fd,int * client_fd)131 CrashGenerationServer::CreateReportChannel(int* server_fd, int* client_fd)
132 {
133 int fds[2];
134
135 if (socketpair(AF_UNIX, SOCK_SEQPACKET, 0, fds))
136 return false;
137
138 static const int on = 1;
139 // Enable passcred on the server end of the socket
140 if (setsockopt(fds[1], SOL_SOCKET, SO_PASSCRED, &on, sizeof(on)))
141 return false;
142
143 if (fcntl(fds[1], F_SETFL, O_NONBLOCK))
144 return false;
145 if (fcntl(fds[1], F_SETFD, FD_CLOEXEC))
146 return false;
147
148 *client_fd = fds[0];
149 *server_fd = fds[1];
150 return true;
151 }
152
153 // The following methods/functions execute on the server thread
154
155 void
Run()156 CrashGenerationServer::Run()
157 {
158 struct pollfd pollfds[2];
159 memset(&pollfds, 0, sizeof(pollfds));
160
161 pollfds[0].fd = server_fd_;
162 pollfds[0].events = POLLIN;
163
164 pollfds[1].fd = control_pipe_in_;
165 pollfds[1].events = POLLIN;
166
167 while (true) {
168 // infinite timeout
169 int nevents = poll(pollfds, sizeof(pollfds)/sizeof(pollfds[0]), -1);
170 if (-1 == nevents) {
171 if (EINTR == errno) {
172 continue;
173 } else {
174 return;
175 }
176 }
177
178 if (pollfds[0].revents && !ClientEvent(pollfds[0].revents))
179 return;
180
181 if (pollfds[1].revents && !ControlEvent(pollfds[1].revents))
182 return;
183 }
184 }
185
186 bool
ClientEvent(short revents)187 CrashGenerationServer::ClientEvent(short revents)
188 {
189 if (POLLHUP & revents)
190 return false;
191 assert(POLLIN & revents);
192
193 // A process has crashed and has signaled us by writing a datagram
194 // to the death signal socket. The datagram contains the crash context needed
195 // for writing the minidump as well as a file descriptor and a credentials
196 // block so that they can't lie about their pid.
197
198 // The length of the control message:
199 static const unsigned kControlMsgSize =
200 CMSG_SPACE(sizeof(int)) + CMSG_SPACE(sizeof(struct ucred));
201 // The length of the regular payload:
202 static const unsigned kCrashContextSize =
203 sizeof(google_breakpad::ExceptionHandler::CrashContext);
204
205 struct msghdr msg = {0};
206 struct iovec iov[1];
207 char crash_context[kCrashContextSize];
208 char control[kControlMsgSize];
209 const ssize_t expected_msg_size = sizeof(crash_context);
210
211 iov[0].iov_base = crash_context;
212 iov[0].iov_len = sizeof(crash_context);
213 msg.msg_iov = iov;
214 msg.msg_iovlen = sizeof(iov)/sizeof(iov[0]);
215 msg.msg_control = control;
216 msg.msg_controllen = kControlMsgSize;
217
218 const ssize_t msg_size = HANDLE_EINTR(recvmsg(server_fd_, &msg, 0));
219 if (msg_size != expected_msg_size)
220 return true;
221
222 if (msg.msg_controllen != kControlMsgSize ||
223 msg.msg_flags & ~MSG_TRUNC)
224 return true;
225
226 // Walk the control payload and extract the file descriptor and validated pid.
227 pid_t crashing_pid = -1;
228 int signal_fd = -1;
229 for (struct cmsghdr *hdr = CMSG_FIRSTHDR(&msg); hdr;
230 hdr = CMSG_NXTHDR(&msg, hdr)) {
231 if (hdr->cmsg_level != SOL_SOCKET)
232 continue;
233 if (hdr->cmsg_type == SCM_RIGHTS) {
234 const unsigned len = hdr->cmsg_len -
235 (((uint8_t*)CMSG_DATA(hdr)) - (uint8_t*)hdr);
236 assert(len % sizeof(int) == 0u);
237 const unsigned num_fds = len / sizeof(int);
238 if (num_fds > 1 || num_fds == 0) {
239 // A nasty process could try and send us too many descriptors and
240 // force a leak.
241 for (unsigned i = 0; i < num_fds; ++i)
242 close(reinterpret_cast<int*>(CMSG_DATA(hdr))[i]);
243 return true;
244 } else {
245 signal_fd = reinterpret_cast<int*>(CMSG_DATA(hdr))[0];
246 }
247 } else if (hdr->cmsg_type == SCM_CREDENTIALS) {
248 const struct ucred *cred =
249 reinterpret_cast<struct ucred*>(CMSG_DATA(hdr));
250 crashing_pid = cred->pid;
251 }
252 }
253
254 if (crashing_pid == -1 || signal_fd == -1) {
255 if (signal_fd)
256 close(signal_fd);
257 return true;
258 }
259
260 string minidump_filename;
261 if (!MakeMinidumpFilename(minidump_filename))
262 return true;
263
264 if (!google_breakpad::WriteMinidump(minidump_filename.c_str(),
265 crashing_pid, crash_context,
266 kCrashContextSize)) {
267 close(signal_fd);
268 return true;
269 }
270
271 if (dump_callback_) {
272 ClientInfo info(crashing_pid, this);
273
274 dump_callback_(dump_context_, &info, &minidump_filename);
275 }
276
277 // Send the done signal to the process: it can exit now.
278 // (Closing this will make the child's sys_read unblock and return 0.)
279 close(signal_fd);
280
281 return true;
282 }
283
284 bool
ControlEvent(short revents)285 CrashGenerationServer::ControlEvent(short revents)
286 {
287 if (POLLHUP & revents)
288 return false;
289 assert(POLLIN & revents);
290
291 char command;
292 if (read(control_pipe_in_, &command, 1))
293 return false;
294
295 switch (command) {
296 case kCommandQuit:
297 return false;
298 default:
299 assert(0);
300 }
301
302 return true;
303 }
304
305 bool
MakeMinidumpFilename(string & outFilename)306 CrashGenerationServer::MakeMinidumpFilename(string& outFilename)
307 {
308 GUID guid;
309 char guidString[kGUIDStringLength+1];
310
311 if (!(CreateGUID(&guid)
312 && GUIDToString(&guid, guidString, sizeof(guidString))))
313 return false;
314
315 char path[PATH_MAX];
316 snprintf(path, sizeof(path), "%s/%s.dmp", dump_dir_.c_str(), guidString);
317
318 outFilename = path;
319 return true;
320 }
321
322 // static
323 void*
ThreadMain(void * arg)324 CrashGenerationServer::ThreadMain(void *arg)
325 {
326 reinterpret_cast<CrashGenerationServer*>(arg)->Run();
327 return NULL;
328 }
329
330 } // namespace google_breakpad
331