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[conkeror.git] / conkeror-spawn-helper.c
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1 /**
2 * (C) Copyright 2008 Jeremy Maitin-Shepard
4 * Use, modification, and distribution are subject to the terms specified in the
5 * COPYING file.
6 **/
8 #include <sys/types.h>
9 #include <sys/socket.h>
10 #include <unistd.h>
11 #include <stdio.h>
12 #include <errno.h>
13 #include <stdlib.h>
14 #include <signal.h>
15 #include <sys/wait.h>
16 #include <sys/stat.h>
17 #include <string.h>
18 #include <fcntl.h>
19 #include <netinet/in.h>
20 #include <dirent.h>
21 #include <sys/resource.h>
23 void fail(const char *msg) {
24 fprintf(stderr, "%s\n", msg);
25 exit(1);
28 void failerr(const char *msg) {
29 perror(msg);
30 exit(1);
33 #define TRY(var, foo) var = foo; while (var == -1) { if(errno != EINTR) failerr(#foo); }
35 void *Malloc(size_t count) { void *r = malloc(count); if (!r) fail("malloc"); return r; }
37 /**
38 * read_all: read from the specified file descriptor, returning a
39 * malloc-allocated buffer containing the data that was read; the
40 * number of bytes read is stored in *bytes_read. If max_bytes is
41 * non-negative, it specifies the maximum number of bytes to read.
42 * Otherwise, read_all reads from the file descriptor until the end of
43 * file is reached.
45 char *read_all(int fd, int max_bytes, int *bytes_read) {
46 int capacity = 256;
47 if (max_bytes > 0)
48 capacity = max_bytes;
49 char *buffer = Malloc(capacity);
50 int count = 0;
51 if (max_bytes < 0 || max_bytes > 0) {
52 while (1) {
53 int remain;
54 if (count == capacity) {
55 capacity *= 2;
56 buffer = realloc(buffer, capacity);
57 if (!buffer)
58 fail("realloc failed");
60 remain = capacity - count;
61 if (max_bytes > 0 && remain > max_bytes)
62 remain = max_bytes;
63 TRY(remain, read(fd, buffer + count, remain));
64 count += remain;
65 if (remain == 0 || count == max_bytes)
66 break;
69 *bytes_read = count;
70 return buffer;
73 /**
74 * next_term: return the next NUL terminated string from buffer, and
75 * adjust buffer and len accordingly.
77 char *next_term(char **buffer, int *len) {
78 char *p = *buffer;
79 int x = 0;
80 int max_len = *len;
81 while (x < max_len && p[x])
82 ++x;
83 if (x == max_len)
84 fail("error parsing");
85 *buffer += x + 1;
86 *len -= (x + 1);
87 return p;
90 struct fd_info {
91 int desired_fd;
92 int orig_fd;
93 char *path;
94 int open_mode;
95 int perms;
98 void write_all(int fd, const char *buf, int len) {
99 int result;
100 do {
101 TRY(result, write(fd, buf, len));
102 buf += result;
103 len -= result;
104 } while (len > 0);
108 * my_connect: Create a connection to the local Conkeror process on
109 * the specified TCP port. After connecting, the properly formatted
110 * header specifying the client_key and the "role" (file descriptor or
111 * -1 to indicate the control socket) are sent as well. The file
112 * descriptor for the socket is returned.
114 int my_connect(int port, char *client_key, int role) {
115 int sockfd;
116 int result;
117 struct sockaddr_in sa;
119 TRY(sockfd, socket(PF_INET, SOCK_STREAM, 0));
120 sa.sin_family = AF_INET;
121 sa.sin_port = htons(port);
122 sa.sin_addr.s_addr = inet_addr("127.0.0.1");
123 memset(sa.sin_zero, 0, sizeof(sa.sin_zero));
125 TRY(result, connect(sockfd, (struct sockaddr *)&sa, sizeof(sa)));
127 /* Send the client key */
128 write_all(sockfd, client_key, strlen(client_key));
130 /* Send the role */
131 if (role < 0) {
132 write_all(sockfd, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0", 15);
134 else {
135 char buf[16];
136 snprintf(buf, 16, "%15d", role);
137 write_all(sockfd, buf, 15);
140 return sockfd;
143 int child_pid = 0;
144 int control_fd;
147 * sigchld_handler: reap any waitable children. Once the child
148 * process exits, send the exit status back over the control socket,
149 * then exit. */
150 void sigchld_handler(int sig) {
151 int status;
152 int pid;
153 int err;
155 while (1) {
156 pid = waitpid(-1, &status, WNOHANG);
157 if (pid == 0)
158 return;
159 if (pid == -1) {
160 if (errno == ECHILD)
161 break;
162 failerr("waitpid");
165 /* Our child process exited */
166 if (pid == child_pid && (WIFEXITED(status) || WIFSIGNALED(status))) {
167 char buf[30];
168 snprintf(buf, 30, "%d", status);
169 write_all(control_fd, buf, strlen(buf) + 1);
170 exit(0);
175 void check_duplicate_fds(struct fd_info *fds, int fd_count) {
176 int i, j;
177 for (i = 0; i < fd_count; ++i) {
178 for (j = i + 1; j < fd_count; ++j) {
179 if (fds[i].desired_fd == fds[j].desired_fd)
180 fail("duplicate redirection requested");
186 * setup_fds: Make the requested redirections. For each entry in the
187 * fds array, rename orig_fd to desired_fd.
189 void setup_fds(struct fd_info *fds, int fd_count) {
190 int i, j, result;
191 for (i = 0; i < fd_count; ++i) {
192 int fd = fds[i].desired_fd;
193 /* Check if this file descriptor is still in use by any subsequent
194 redirection. */
195 for (j = i + 1; j < fd_count; ++j) {
196 if (fd == fds[j].orig_fd) {
197 /* It is in use. Pick a new file descriptor for fds[j]. */
198 int fd_new;
199 TRY(fd_new, dup(fds[j].orig_fd));
200 close(fds[j].orig_fd);
201 fds[j].orig_fd = fd_new;
202 break;
205 TRY(result, dup2(fds[i].orig_fd, fd));
206 close(fds[i].orig_fd);
210 int main(int argc, char **argv) {
212 int port;
213 char *client_key, *server_key, *executable, *workdir;
214 char **my_argv;
215 struct fd_info *fds;
216 int fd_count;
217 int i;
218 sigset_t my_mask, my_old_mask;
220 if (argc != 3 || (port = atoi(argv[2])) == 0)
221 fail("Invalid arguments");
223 sigemptyset(&my_mask);
224 sigaddset(&my_mask, SIGCHLD);
226 /* Block SIGPIPE to avoid a signal being generated while writing to a socket */
227 signal(SIGPIPE, SIG_IGN);
229 /* Close everything except STDERR. Mozilla leaves us with a bunch
230 of junk file descriptors. */
232 DIR *dir = opendir("/proc/self/fd");
233 if (!dir) {
234 /* No proc filesystem available, just loop through file descriptors */
235 struct rlimit file_lim;
236 int max_fileno = 1024;
237 if (getrlimit(RLIMIT_NOFILE, &file_lim) == 0)
238 max_fileno = file_lim.rlim_cur;
239 for (i = 0; i < max_fileno; ++i) {
240 if (i == STDERR_FILENO)
241 continue;
242 close(i);
244 } else {
245 struct dirent *dir_ent;
246 int dir_fd = dirfd(dir);
247 while ((dir_ent = readdir(dir)) != NULL) {
248 int file_desc = atoi(dir_ent->d_name);
249 if (file_desc == STDERR_FILENO || file_desc == dir_fd)
250 continue;
251 close(file_desc);
253 closedir(dir);
257 /* Parse key file */
259 char *buf;
260 int len;
261 int my_argc;
262 /* Read the entire file into buf. */
264 int file;
265 TRY(file, open(argv[1], O_RDONLY));
266 buf = read_all(file, -1, &len);
267 close(file);
269 /* Remove the temporary file */
270 remove(argv[1]);
272 client_key = next_term(&buf, &len);
273 server_key = next_term(&buf, &len);
274 executable = next_term(&buf, &len);
275 workdir = next_term(&buf, &len);
276 my_argc = atoi(next_term(&buf, &len));
277 my_argv = Malloc(sizeof(char *) * (my_argc + 1));
278 for (i = 0; i < my_argc; ++i)
279 my_argv[i] = next_term(&buf, &len);
280 my_argv[my_argc] = NULL;
281 fd_count = atoi(next_term(&buf, &len));
282 if (fd_count < 0) fail("invalid fd count");
283 fds = Malloc(sizeof(struct fd_info) * fd_count);
284 for (i = 0; i < fd_count; ++i) {
285 fds[i].desired_fd = atoi(next_term(&buf, &len));
286 fds[i].path = next_term(&buf, &len);
287 if (fds[i].path[0]) {
288 fds[i].open_mode = atoi(next_term(&buf, &len));
289 fds[i].perms = atoi(next_term(&buf, &len));
292 if (len != 0)
293 fail("invalid input file");
296 /* Validate the file descriptor redirection request. */
297 check_duplicate_fds(fds, fd_count);
299 /* Create the control socket connection. */
300 control_fd = my_connect(port, client_key, -1);
302 /* Create a socket connection or open a local file for each
303 requested file descriptor redirection. */
304 for (i = 0; i < fd_count; ++i) {
305 if (fds[i].path[0]) {
306 TRY(fds[i].orig_fd, open(fds[i].path, fds[i].open_mode, fds[i].perms));
307 } else {
308 fds[i].orig_fd = my_connect(port, client_key, fds[i].desired_fd);
312 /* Check server key */
314 int len = strlen(server_key);
315 int read_len;
316 char *buf = read_all(control_fd, len, &read_len);
317 if (len != read_len || memcmp(buf, server_key, len) != 0)
318 fail("server key mismatch");
319 free(buf);
322 /* Block SIGCHLD */
323 sigprocmask(SIG_BLOCK, &my_mask, &my_old_mask);
325 /* Create the child process */
326 child_pid = fork();
327 if (child_pid == 0) {
328 int result;
329 /* Unblock SIGCHLD */
330 sigprocmask(SIG_SETMASK, &my_old_mask, NULL);
332 /* Reset the SIGPIPE signal handler. */
333 signal(SIGPIPE, SIG_DFL);
335 /* Close the control socket, as it isn't needed from the child. */
336 close(control_fd);
338 /* Change to the specified working directory. */
339 if (workdir[0] != 0) {
340 if (chdir(workdir) == -1)
341 failerr(workdir);
344 /* Rearrange file descriptors according to the user specification */
345 setup_fds(fds, fd_count);
347 /* Exec */
348 TRY(result, execv(executable, my_argv));
350 } else if (child_pid == -1) {
351 failerr("fork");
352 } else {
353 /* We are in the parent process */
354 char msg;
355 int count;
357 /* Install SIGCHLD handler */
359 struct sigaction act;
360 act.sa_handler = sigchld_handler;
361 sigemptyset(&act.sa_mask);
362 act.sa_flags = SA_NOCLDSTOP;
363 sigaction(SIGCHLD, &act, NULL);
365 /* Unblock SIGCHLD */
366 sigprocmask(SIG_SETMASK, &my_old_mask, NULL);
368 /* Close all of the redirection file descriptors, as we don't need
369 them from the parent. */
370 for (i = 0; i < fd_count; ++i)
371 close(fds[i].orig_fd);
373 /* Wait for a message from the server telling us to exit early. */
374 TRY(count, read(control_fd, &msg, 1));
376 if (count == 0) {
377 /* End of file received: exit without killing child */
378 return 0;
381 /* Assume msg == 0 until we support more messages */
382 TRY(count, kill(child_pid, SIGTERM));
383 return 0;