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f1e894f3 | 1 | /* $Cambridge: exim/src/src/child.c,v 1.5 2005/06/27 14:29:43 ph10 Exp $ */ |
059ec3d9 PH |
2 | |
3 | /************************************************* | |
4 | * Exim - an Internet mail transport agent * | |
5 | *************************************************/ | |
6 | ||
c988f1f4 | 7 | /* Copyright (c) University of Cambridge 1995 - 2005 */ |
059ec3d9 PH |
8 | /* See the file NOTICE for conditions of use and distribution. */ |
9 | ||
10 | ||
11 | #include "exim.h" | |
12 | ||
13 | static void (*oldsignal)(int); | |
14 | ||
15 | ||
16 | /************************************************* | |
17 | * Ensure an fd has a given value * | |
18 | *************************************************/ | |
19 | ||
20 | /* This function is called when we want to ensure that a certain fd has a | |
21 | specific value (one of 0, 1, 2). If it hasn't got it already, close the value | |
22 | we want, duplicate the fd, then close the old one. | |
23 | ||
24 | Arguments: | |
25 | oldfd original fd | |
26 | newfd the fd we want | |
27 | ||
28 | Returns: nothing | |
29 | */ | |
30 | ||
31 | static void | |
32 | force_fd(int oldfd, int newfd) | |
33 | { | |
34 | if (oldfd == newfd) return; | |
f1e894f3 PH |
35 | (void)close(newfd); |
36 | (void)dup2(oldfd, newfd); | |
37 | (void)close(oldfd); | |
059ec3d9 PH |
38 | } |
39 | ||
40 | ||
41 | ||
42 | /************************************************* | |
43 | * Build argv list and optionally re-exec Exim * | |
44 | *************************************************/ | |
45 | ||
46 | /* This function is called when Exim wants to re-exec (overlay) itself in the | |
47 | current process. This is different to child_open_exim(), which runs another | |
48 | Exim process in parallel (but it then calls this function). The function's | |
49 | basic job is to build the argv list according to the values of current options | |
50 | settings. There is a basic list that all calls require, and an additional list | |
51 | that some do not require. Further additions can be given as additional | |
52 | arguments. An option specifies whether the exec() is actually to happen, and if | |
53 | so, what is to be done if it fails. | |
54 | ||
55 | Arguments: | |
56 | exec_type CEE_RETURN_ARGV => don't exec; return the argv list | |
57 | CEE_EXEC_EXIT => just exit() on exec failure | |
58 | CEE_EXEC_PANIC => panic-die on exec failure | |
59 | kill_v if TRUE, don't pass on the D_v flag | |
60 | pcount if not NULL, points to extra size of argv required, and if | |
61 | CEE_RETURN_ARGV is specified, it is updated to give the | |
62 | number of slots used | |
63 | minimal TRUE if only minimal argv is required | |
64 | acount number of additional arguments | |
65 | ... further values to add to argv | |
66 | ||
67 | Returns: if CEE_RETURN_ARGV is given, returns a pointer to argv; | |
68 | otherwise, does not return | |
69 | */ | |
70 | ||
71 | uschar ** | |
72 | child_exec_exim(int exec_type, BOOL kill_v, int *pcount, BOOL minimal, | |
73 | int acount, ...) | |
74 | { | |
75 | int first_special = -1; | |
76 | int n = 0; | |
77 | int extra = (pcount != NULL)? *pcount : 0; | |
78 | uschar **argv = | |
79 | store_get((extra + acount + MAX_CLMACROS + 16) * sizeof(char *)); | |
80 | ||
81 | /* In all case, the list starts out with the path, any macros, and a changed | |
82 | config file. */ | |
83 | ||
84 | argv[n++] = exim_path; | |
85 | if (clmacro_count > 0) | |
86 | { | |
87 | memcpy(argv + n, clmacros, clmacro_count * sizeof(uschar *)); | |
88 | n += clmacro_count; | |
89 | } | |
90 | if (config_changed) | |
91 | { | |
92 | argv[n++] = US"-C"; | |
93 | argv[n++] = config_main_filename; | |
94 | } | |
95 | ||
96 | /* These values are added only for non-minimal cases. If debug_selector is | |
97 | precisely D_v, we have to assume this was started by a non-admin user, and | |
98 | we suppress the flag when requested. (This happens when passing on an SMTP | |
99 | connection, and after ETRN.) If there's more debugging going on, an admin user | |
100 | was involved, so we do pass it on. */ | |
101 | ||
102 | if (!minimal) | |
103 | { | |
104 | if (debug_selector == D_v) | |
105 | { | |
106 | if (!kill_v) argv[n++] = US"-v"; | |
107 | } | |
108 | else | |
109 | { | |
110 | if (debug_selector != 0) | |
111 | argv[n++] = string_sprintf("-d=0x%x", debug_selector); | |
112 | } | |
113 | if (dont_deliver) argv[n++] = US"-N"; | |
114 | if (queue_smtp) argv[n++] = US"-odqs"; | |
115 | if (synchronous_delivery) argv[n++] = US"-odi"; | |
116 | if (connection_max_messages >= 0) | |
117 | argv[n++] = string_sprintf("-oB%d", connection_max_messages); | |
118 | } | |
119 | ||
120 | /* Now add in any others that are in the call. Remember which they were, | |
121 | for more helpful diagnosis on failure. */ | |
122 | ||
123 | if (acount > 0) | |
124 | { | |
125 | va_list ap; | |
126 | va_start(ap, acount); | |
127 | first_special = n; | |
128 | while (acount-- > 0) | |
129 | argv[n++] = va_arg(ap, uschar *); | |
130 | va_end(ap); | |
131 | } | |
132 | ||
133 | /* Terminate the list, and return it, if that is what is wanted. */ | |
134 | ||
135 | argv[n] = NULL; | |
136 | if (exec_type == CEE_RETURN_ARGV) | |
137 | { | |
138 | if (pcount != NULL) *pcount = n; | |
139 | return argv; | |
140 | } | |
141 | ||
142 | /* Otherwise, do the exec() here, and handle the consequences of an unexpected | |
143 | failure. We know that there will always be at least one extra option in the | |
144 | call when exec() is done here, so it can be used to add to the panic data. */ | |
145 | ||
146 | DEBUG(D_exec) debug_print_argv(argv); | |
147 | exim_nullstd(); /* Make sure std{in,out,err} exist */ | |
148 | execv(CS argv[0], (char *const *)argv); | |
149 | ||
150 | log_write(0, | |
151 | LOG_MAIN | ((exec_type == CEE_EXEC_EXIT)? LOG_PANIC : LOG_PANIC_DIE), | |
152 | "re-exec of exim (%s) with %s failed: %s", exim_path, argv[first_special], | |
153 | strerror(errno)); | |
154 | ||
155 | /* Get here if exec_type == CEE_EXEC_EXIT. | |
156 | Note: this must be _exit(), not exit(). */ | |
157 | ||
158 | _exit(EX_EXECFAILED); | |
159 | ||
160 | return NULL; /* To keep compilers happy */ | |
161 | } | |
162 | ||
163 | ||
164 | ||
165 | ||
166 | /************************************************* | |
167 | * Create a child Exim process * | |
168 | *************************************************/ | |
169 | ||
170 | /* This function is called when Exim wants to run a parallel instance of itself | |
171 | in order to inject a message via the standard input. The function creates a | |
172 | child process and runs Exim in it. It sets up a pipe to the standard input of | |
173 | the new process, and returns that to the caller via fdptr. The function returns | |
174 | the pid of the new process, or -1 if things go wrong. If debug_fd is | |
175 | non-negative, it is passed as stderr. | |
176 | ||
177 | Argument: fdptr pointer to int for the stdin fd | |
178 | Returns: pid of the created process or -1 if anything has gone wrong | |
179 | */ | |
180 | ||
181 | pid_t | |
182 | child_open_exim(int *fdptr) | |
183 | { | |
184 | int pfd[2]; | |
185 | int save_errno; | |
186 | pid_t pid; | |
187 | ||
188 | /* Create the pipe and fork the process. Ensure that SIGCHLD is set to | |
189 | SIG_DFL before forking, so that the child process can be waited for. We | |
190 | sometimes get here with it set otherwise. Save the old state for resetting | |
191 | on the wait. */ | |
192 | ||
193 | if (pipe(pfd) != 0) return (pid_t)(-1); | |
194 | oldsignal = signal(SIGCHLD, SIG_DFL); | |
195 | pid = fork(); | |
196 | ||
197 | /* Child process: make the reading end of the pipe into the standard input and | |
198 | close the writing end. If debugging, pass debug_fd as stderr. Then re-exec | |
199 | Exim. Failure is signalled with EX_EXECFAILED, but this shouldn't occur! */ | |
200 | ||
201 | if (pid == 0) | |
202 | { | |
203 | force_fd(pfd[pipe_read], 0); | |
f1e894f3 | 204 | (void)close(pfd[pipe_write]); |
059ec3d9 PH |
205 | if (debug_fd > 0) force_fd(debug_fd, 2); |
206 | if (bounce_sender_authentication != NULL) | |
207 | child_exec_exim(CEE_EXEC_EXIT, FALSE, NULL, FALSE, 8, | |
208 | US"-t", US"-oem", US"-oi", US"-f", US"<>", US"-oMas", | |
209 | bounce_sender_authentication, message_id_option); | |
210 | else | |
211 | child_exec_exim(CEE_EXEC_EXIT, FALSE, NULL, FALSE, 6, | |
212 | US"-t", US"-oem", US"-oi", US"-f", US"<>", message_id_option); | |
213 | /* Control does not return here. */ | |
214 | } | |
215 | ||
216 | /* Parent process. Save fork() errno and close the reading end of the stdin | |
217 | pipe. */ | |
218 | ||
219 | save_errno = errno; | |
f1e894f3 | 220 | (void)close(pfd[pipe_read]); |
059ec3d9 PH |
221 | |
222 | /* Fork succeeded */ | |
223 | ||
224 | if (pid > 0) | |
225 | { | |
226 | *fdptr = pfd[pipe_write]; /* return writing end of stdin pipe */ | |
227 | return pid; /* and pid of new process */ | |
228 | } | |
229 | ||
230 | /* Fork failed */ | |
231 | ||
f1e894f3 | 232 | (void)close(pfd[pipe_write]); |
059ec3d9 PH |
233 | errno = save_errno; |
234 | return (pid_t)(-1); | |
235 | } | |
236 | ||
237 | ||
238 | ||
239 | ||
240 | /************************************************* | |
241 | * Create a non-Exim child process * | |
242 | *************************************************/ | |
243 | ||
244 | /* This function creates a child process and runs the given command in it. It | |
245 | sets up pipes to the standard input and output of the new process, and returns | |
246 | them to the caller. The standard error is cloned to the output. If there are | |
247 | any file descriptors "in the way" in the new process, they are closed. A new | |
248 | umask is supplied for the process, and an optional new uid and gid are also | |
249 | available. These are used by the queryprogram router to set an unprivileged id. | |
b668c215 PH |
250 | SIGUSR1 is always disabled in the new process, as it is not going to be running |
251 | Exim (the function child_open_exim() is provided for that). This function | |
252 | returns the pid of the new process, or -1 if things go wrong. | |
059ec3d9 PH |
253 | |
254 | Arguments: | |
255 | argv the argv for exec in the new process | |
256 | envp the envp for exec in the new process | |
257 | newumask umask to set in the new process | |
258 | newuid point to uid for the new process or NULL for no change | |
259 | newgid point to gid for the new process or NULL for no change | |
260 | infdptr pointer to int into which the fd of the stdin of the new process | |
261 | is placed | |
262 | outfdptr pointer to int into which the fd of the stdout/stderr of the new | |
263 | process is placed | |
264 | wd if not NULL, a path to be handed to chdir() in the new process | |
265 | make_leader if TRUE, make the new process a process group leader | |
8e669ac1 | 266 | |
059ec3d9 PH |
267 | Returns: the pid of the created process or -1 if anything has gone wrong |
268 | */ | |
269 | ||
270 | pid_t | |
271 | child_open_uid(uschar **argv, uschar **envp, int newumask, uid_t *newuid, | |
272 | gid_t *newgid, int *infdptr, int *outfdptr, uschar *wd, BOOL make_leader) | |
273 | { | |
274 | int save_errno; | |
275 | int inpfd[2], outpfd[2]; | |
276 | pid_t pid; | |
277 | ||
278 | /* Create the pipes. */ | |
279 | ||
280 | if (pipe(inpfd) != 0) return (pid_t)(-1); | |
281 | if (pipe(outpfd) != 0) | |
282 | { | |
f1e894f3 PH |
283 | (void)close(inpfd[pipe_read]); |
284 | (void)close(inpfd[pipe_write]); | |
059ec3d9 PH |
285 | return (pid_t)(-1); |
286 | } | |
287 | ||
288 | /* Fork the process. Ensure that SIGCHLD is set to SIG_DFL before forking, so | |
289 | that the child process can be waited for. We sometimes get here with it set | |
290 | otherwise. Save the old state for resetting on the wait. */ | |
291 | ||
292 | oldsignal = signal(SIGCHLD, SIG_DFL); | |
293 | pid = fork(); | |
294 | ||
295 | /* The child process becomes a process group leader if requested, and then | |
296 | organizes the pipes. Any unexpected failure is signalled with EX_EXECFAILED; | |
297 | these are all "should never occur" failures, except perhaps for exec failing | |
298 | because the command doesn't exist. */ | |
299 | ||
300 | if (pid == 0) | |
301 | { | |
302 | if (make_leader && setpgid(0,0) < 0) goto CHILD_FAILED; | |
303 | ||
f1e894f3 | 304 | (void)close(inpfd[pipe_write]); |
059ec3d9 PH |
305 | force_fd(inpfd[pipe_read], 0); |
306 | ||
f1e894f3 | 307 | (void)close(outpfd[pipe_read]); |
059ec3d9 PH |
308 | force_fd(outpfd[pipe_write], 1); |
309 | ||
f1e894f3 PH |
310 | (void)close(2); |
311 | (void)dup2(1, 2); | |
059ec3d9 | 312 | |
b668c215 | 313 | /* Set the required environment. */ |
059ec3d9 | 314 | |
b668c215 | 315 | signal(SIGUSR1, SIG_IGN); |
059ec3d9 | 316 | if (newgid != NULL && setgid(*newgid) < 0) goto CHILD_FAILED; |
b668c215 | 317 | if (newuid != NULL && setuid(*newuid) < 0) goto CHILD_FAILED; |
059ec3d9 PH |
318 | (void)umask(newumask); |
319 | ||
320 | /* Set the working directory if required */ | |
321 | ||
322 | if (wd != NULL && Uchdir(wd) < 0) goto CHILD_FAILED; | |
323 | ||
324 | /* Now do the exec */ | |
325 | ||
326 | if (envp == NULL) execv(CS argv[0], (char *const *)argv); | |
327 | else execve(CS argv[0], (char *const *)argv, (char *const *)envp); | |
328 | ||
329 | /* Failed to execv. Signal this failure using EX_EXECFAILED. We are | |
330 | losing the actual errno we got back, because there is no way to return | |
331 | this. */ | |
332 | ||
333 | CHILD_FAILED: | |
334 | _exit(EX_EXECFAILED); /* Note: must be _exit(), NOT exit() */ | |
335 | } | |
336 | ||
337 | /* Parent process. Save any fork failure code, and close the reading end of the | |
338 | stdin pipe, and the writing end of the stdout pipe. */ | |
339 | ||
340 | save_errno = errno; | |
f1e894f3 PH |
341 | (void)close(inpfd[pipe_read]); |
342 | (void)close(outpfd[pipe_write]); | |
059ec3d9 PH |
343 | |
344 | /* Fork succeeded; return the input/output pipes and the pid */ | |
345 | ||
346 | if (pid > 0) | |
347 | { | |
348 | *infdptr = inpfd[pipe_write]; | |
349 | *outfdptr = outpfd[pipe_read]; | |
350 | return pid; | |
351 | } | |
352 | ||
353 | /* Fork failed; reset fork errno before returning */ | |
354 | ||
f1e894f3 PH |
355 | (void)close(inpfd[pipe_write]); |
356 | (void)close(outpfd[pipe_read]); | |
059ec3d9 PH |
357 | errno = save_errno; |
358 | return (pid_t)(-1); | |
359 | } | |
360 | ||
361 | ||
362 | ||
363 | ||
364 | /************************************************* | |
365 | * Create child process without uid change * | |
366 | *************************************************/ | |
367 | ||
368 | /* This function is a wrapper for child_open_uid() that doesn't have the uid, | |
b668c215 PH |
369 | gid and working directory changing arguments. The function is provided so as to |
370 | have a clean interface for use from local_scan(), but also saves writing NULL | |
371 | arguments several calls that would otherwise use child_open_uid(). | |
059ec3d9 PH |
372 | |
373 | Arguments: | |
374 | argv the argv for exec in the new process | |
375 | envp the envp for exec in the new process | |
376 | newumask umask to set in the new process | |
377 | infdptr pointer to int into which the fd of the stdin of the new process | |
378 | is placed | |
379 | outfdptr pointer to int into which the fd of the stdout/stderr of the new | |
380 | process is placed | |
381 | make_leader if TRUE, make the new process a process group leader | |
382 | ||
383 | Returns: the pid of the created process or -1 if anything has gone wrong | |
384 | */ | |
385 | ||
386 | pid_t | |
387 | child_open(uschar **argv, uschar **envp, int newumask, int *infdptr, | |
388 | int *outfdptr, BOOL make_leader) | |
389 | { | |
390 | return child_open_uid(argv, envp, newumask, NULL, NULL, infdptr, outfdptr, | |
391 | NULL, make_leader); | |
392 | } | |
393 | ||
394 | ||
395 | ||
396 | ||
397 | /************************************************* | |
398 | * Close down child process * | |
399 | *************************************************/ | |
400 | ||
401 | /* Wait for the given process to finish, with optional timeout. | |
402 | ||
403 | Arguments | |
404 | pid: the pid to wait for | |
405 | timeout: maximum time to wait; 0 means for as long as it takes | |
406 | ||
407 | Returns: >= 0 process terminated by exiting; value is process | |
408 | ending status; if an execve() failed, the value | |
409 | is typically 127 (defined as EX_EXECFAILED) | |
410 | < 0 & > -256 process was terminated by a signal; value is the | |
411 | negation of the signal number | |
412 | -256 timed out | |
413 | -257 other error in wait(); errno still set | |
414 | */ | |
415 | ||
416 | int | |
417 | child_close(pid_t pid, int timeout) | |
418 | { | |
419 | int yield; | |
420 | ||
421 | if (timeout > 0) | |
422 | { | |
423 | sigalrm_seen = FALSE; | |
424 | alarm(timeout); | |
425 | } | |
426 | ||
427 | for(;;) | |
428 | { | |
429 | int status; | |
430 | pid_t rc = waitpid(pid, &status, 0); | |
431 | if (rc == pid) | |
432 | { | |
433 | int lowbyte = status & 255; | |
434 | if (lowbyte == 0) yield = (status >> 8) & 255; | |
435 | else yield = -lowbyte; | |
436 | break; | |
437 | } | |
438 | if (rc < 0) | |
439 | { | |
440 | yield = (errno == EINTR && sigalrm_seen)? -256 : -257; | |
441 | break; | |
442 | } | |
443 | } | |
444 | ||
445 | if (timeout > 0) alarm(0); | |
446 | ||
447 | signal(SIGCHLD, oldsignal); /* restore */ | |
448 | return yield; | |
449 | } | |
450 | ||
451 | /* End of child.c */ |