1 /*************************************************
2 * Exim - an Internet mail transport agent *
3 *************************************************/
5 /* Copyright (c) University of Cambridge 1995 - 2015 */
6 /* Copyright (c) The Exim Maintainers 2020 - 2021 */
7 /* See the file NOTICE for conditions of use and distribution. */
12 static void (*oldsignal)(int);
15 /*************************************************
16 * Ensure an fd has a given value *
17 *************************************************/
19 /* This function is called when we want to ensure that a certain fd has a
20 specific value (one of 0, 1, 2). If it hasn't got it already, close the value
21 we want, duplicate the fd, then close the old one.
31 force_fd(int oldfd, int newfd)
33 if (oldfd == newfd) return;
35 (void)dup2(oldfd, newfd);
41 /*************************************************
42 * Build argv list and optionally re-exec Exim *
43 *************************************************/
45 /* This function is called when Exim wants to re-exec (overlay) itself in the
46 current process. This is different to child_open_exim(), which runs another
47 Exim process in parallel (but it then calls this function). The function's
48 basic job is to build the argv list according to the values of current options
49 settings. There is a basic list that all calls require, and an additional list
50 that some do not require. Further additions can be given as additional
51 arguments. An option specifies whether the exec() is actually to happen, and if
52 so, what is to be done if it fails.
55 exec_type CEE_RETURN_ARGV => don't exec; return the argv list
56 CEE_EXEC_EXIT => just exit() on exec failure
57 CEE_EXEC_PANIC => panic-die on exec failure
58 kill_v if TRUE, don't pass on the D_v flag
59 pcount if not NULL, points to extra size of argv required, and if
60 CEE_RETURN_ARGV is specified, it is updated to give the
62 minimal TRUE if only minimal argv is required
63 acount number of additional arguments
64 ... further values to add to argv
66 Returns: if CEE_RETURN_ARGV is given, returns a pointer to argv;
67 otherwise, does not return
71 child_exec_exim(int exec_type, BOOL kill_v, int *pcount, BOOL minimal,
74 int first_special = -1;
76 int extra = pcount ? *pcount : 0;
79 argv = store_get((extra + acount + MAX_CLMACROS + 21) * sizeof(char *), FALSE);
81 /* In all case, the list starts out with the path, any macros, and a changed
84 argv[n++] = exim_path;
85 if (clmacro_count > 0)
87 memcpy(argv + n, clmacros, clmacro_count * sizeof(uschar *));
93 argv[n++] = config_main_filename;
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. */
104 if (debug_selector == D_v)
106 if (!kill_v) argv[n++] = US"-v";
110 if (debug_selector != 0)
112 argv[n++] = string_sprintf("-d=0x%x", debug_selector);
115 int flags = fcntl(debug_fd, F_GETFD);
116 if (flags != -1) (void)fcntl(debug_fd, F_SETFD, flags & ~FD_CLOEXEC);
125 argv[n++] = US"-MCd";
126 argv[n++] = US process_purpose;
128 if (!f.testsuite_delays) argv[n++] = US"-odd";
129 if (f.dont_deliver) argv[n++] = US"-N";
130 if (f.queue_smtp) argv[n++] = US"-odqs";
131 if (f.synchronous_delivery) argv[n++] = US"-odi";
132 if (connection_max_messages >= 0)
133 argv[n++] = string_sprintf("-oB%d", connection_max_messages);
136 argv[n++] = US"-MCG";
137 argv[n++] = queue_name;
141 /* Now add in any others that are in the call. Remember which they were,
142 for more helpful diagnosis on failure. */
147 va_start(ap, acount);
150 argv[n++] = va_arg(ap, uschar *);
154 /* Terminate the list, and return it, if that is what is wanted. */
157 if (exec_type == CEE_RETURN_ARGV)
159 if (pcount) *pcount = n;
163 /* Otherwise, do the exec() here, and handle the consequences of an unexpected
164 failure. We know that there will always be at least one extra option in the
165 call when exec() is done here, so it can be used to add to the panic data. */
167 DEBUG(D_exec) debug_print_argv(CUSS argv);
168 exim_nullstd(); /* Make sure std{in,out,err} exist */
169 execv(CS argv[0], (char *const *)argv);
172 LOG_MAIN | ((exec_type == CEE_EXEC_EXIT)? LOG_PANIC : LOG_PANIC_DIE),
173 "re-exec of exim (%s) with %s failed: %s", exim_path, argv[first_special],
176 /* Get here if exec_type == CEE_EXEC_EXIT.
177 Note: this must be _exit(), not exit(). */
179 _exit(EX_EXECFAILED);
181 return NULL; /* To keep compilers happy */
187 /*************************************************
188 * Create a child Exim process *
189 *************************************************/
191 /* This function is called when Exim wants to run a parallel instance of itself
192 in order to inject a message via the standard input. The function creates a
193 child process and runs Exim in it. It sets up a pipe to the standard input of
194 the new process, and returns that to the caller via fdptr. The function returns
195 the pid of the new process, or -1 if things go wrong. If debug_fd is
196 non-negative, it is passed as stderr.
198 This interface is now a just wrapper for the more complicated function
199 child_open_exim2(), which has additional arguments. The wrapper must continue
200 to exist, even if all calls from within Exim are changed, because it is
201 documented for use from local_scan().
203 Argument: fdptr pointer to int for the stdin fd
204 purpose of the child process, for debug
205 Returns: pid of the created process or -1 if anything has gone wrong
209 child_open_exim_function(int * fdptr, const uschar * purpose)
211 return child_open_exim2_function(fdptr, US"<>", bounce_sender_authentication,
216 /* This is a more complicated function for creating a child Exim process, with
220 fdptr pointer to int for the stdin fd
221 sender for a sender address (data for -f)
222 sender_authentication authenticated sender address or NULL
223 purpose of the child process, for debug
225 Returns: pid of the created process or -1 if anything has gone wrong
229 child_open_exim2_function(int * fdptr, uschar * sender,
230 uschar * sender_authentication, const uschar * purpose)
236 /* Create the pipe and fork the process. Ensure that SIGCHLD is set to
237 SIG_DFL before forking, so that the child process can be waited for. We
238 sometimes get here with it set otherwise. Save the old state for resetting
241 if (pipe(pfd) != 0) return (pid_t)(-1);
242 oldsignal = signal(SIGCHLD, SIG_DFL);
243 pid = exim_fork(purpose);
245 /* Child process: make the reading end of the pipe into the standard input and
246 close the writing end. If debugging, pass debug_fd as stderr. Then re-exec
247 Exim with appropriate options. In the test harness, use -odi unless queue_only
248 is set, so that the bounce is fully delivered before returning. Failure is
249 signalled with EX_EXECFAILED (specified by CEE_EXEC_EXIT), but this shouldn't
254 force_fd(pfd[pipe_read], 0);
255 (void)close(pfd[pipe_write]);
256 if (debug_fd > 0) force_fd(debug_fd, 2);
257 if (f.running_in_test_harness && !queue_only)
259 if (sender_authentication)
260 child_exec_exim(CEE_EXEC_EXIT, FALSE, NULL, FALSE, 9,
261 US "-odi", US"-t", US"-oem", US"-oi", US"-f", sender, US"-oMas",
262 sender_authentication, message_id_option);
264 child_exec_exim(CEE_EXEC_EXIT, FALSE, NULL, FALSE, 7,
265 US "-odi", US"-t", US"-oem", US"-oi", US"-f", sender,
267 /* Control does not return here. */
269 else /* Not test harness */
271 if (sender_authentication)
272 child_exec_exim(CEE_EXEC_EXIT, FALSE, NULL, FALSE, 8,
273 US"-t", US"-oem", US"-oi", US"-f", sender, US"-oMas",
274 sender_authentication, message_id_option);
276 child_exec_exim(CEE_EXEC_EXIT, FALSE, NULL, FALSE, 6,
277 US"-t", US"-oem", US"-oi", US"-f", sender, message_id_option);
278 /* Control does not return here. */
282 testharness_pause_ms(100); /* let child work even longer, for exec */
284 /* Parent process. Save fork() errno and close the reading end of the stdin
288 (void)close(pfd[pipe_read]);
294 *fdptr = pfd[pipe_write]; /* return writing end of stdin pipe */
295 return pid; /* and pid of new process */
300 (void)close(pfd[pipe_write]);
304 #endif /* STAND_ALONE */
308 /*************************************************
309 * Create a non-Exim child process *
310 *************************************************/
312 /* This function creates a child process and runs the given command in it. It
313 sets up pipes to the standard input and output of the new process, and returns
314 them to the caller. The standard error is cloned to the output. If there are
315 any file descriptors "in the way" in the new process, they are closed. A new
316 umask is supplied for the process, and an optional new uid and gid are also
317 available. These are used by the queryprogram router to set an unprivileged id.
318 SIGUSR1 is always disabled in the new process, as it is not going to be running
319 Exim (the function child_open_exim() is provided for that). This function
320 returns the pid of the new process, or -1 if things go wrong.
323 argv the argv for exec in the new process
324 envp the envp for exec in the new process
325 newumask umask to set in the new process
326 newuid point to uid for the new process or NULL for no change
327 newgid point to gid for the new process or NULL for no change
328 infdptr pointer to int into which the fd of the stdin of the new process
330 outfdptr pointer to int into which the fd of the stdout/stderr of the new
332 wd if not NULL, a path to be handed to chdir() in the new process
333 make_leader if TRUE, make the new process a process group leader
334 purpose for debug: reason for running the task
336 Returns: the pid of the created process or -1 if anything has gone wrong
340 child_open_uid(const uschar **argv, const uschar **envp, int newumask,
341 uid_t *newuid, gid_t *newgid, int *infdptr, int *outfdptr, uschar *wd,
342 BOOL make_leader, const uschar * purpose)
345 int inpfd[2], outpfd[2];
348 /* Create the pipes. */
350 if (pipe(inpfd) != 0) return (pid_t)(-1);
351 if (pipe(outpfd) != 0)
353 (void)close(inpfd[pipe_read]);
354 (void)close(inpfd[pipe_write]);
358 /* Fork the process. Ensure that SIGCHLD is set to SIG_DFL before forking, so
359 that the child process can be waited for. We sometimes get here with it set
360 otherwise. Save the old state for resetting on the wait. */
362 oldsignal = signal(SIGCHLD, SIG_DFL);
363 pid = exim_fork(purpose);
365 /* Handle the child process. First, set the required environment. We must do
366 this before messing with the pipes, in order to be able to write debugging
367 output when things go wrong. */
371 signal(SIGUSR1, SIG_IGN);
372 signal(SIGPIPE, SIG_DFL);
374 if (newgid && setgid(*newgid) < 0)
376 DEBUG(D_any) debug_printf("failed to set gid=%ld in subprocess: %s\n",
377 (long int)(*newgid), strerror(errno));
381 if (newuid && setuid(*newuid) < 0)
383 DEBUG(D_any) debug_printf("failed to set uid=%ld in subprocess: %s\n",
384 (long int)(*newuid), strerror(errno));
388 (void)umask(newumask);
390 if (wd && Uchdir(wd) < 0)
392 DEBUG(D_any) debug_printf("failed to chdir to %s: %s\n", wd,
397 /* Becomes a process group leader if requested, and then organize the pipes.
398 Any unexpected failure is signalled with EX_EXECFAILED; these are all "should
399 never occur" failures, except for exec failing because the command doesn't
402 if (make_leader && setpgid(0,0) < 0)
404 DEBUG(D_any) debug_printf("failed to set group leader in subprocess: %s\n",
409 (void)close(inpfd[pipe_write]);
410 force_fd(inpfd[pipe_read], 0);
412 (void)close(outpfd[pipe_read]);
413 force_fd(outpfd[pipe_write], 1);
418 /* Now do the exec */
420 if (envp) execve(CS argv[0], (char *const *)argv, (char *const *)envp);
421 else execv(CS argv[0], (char *const *)argv);
423 /* Failed to execv. Signal this failure using EX_EXECFAILED. We are
424 losing the actual errno we got back, because there is no way to return
428 _exit(EX_EXECFAILED); /* Note: must be _exit(), NOT exit() */
431 /* Parent process. Save any fork failure code, and close the reading end of the
432 stdin pipe, and the writing end of the stdout pipe. */
435 (void)close(inpfd[pipe_read]);
436 (void)close(outpfd[pipe_write]);
438 /* Fork succeeded; return the input/output pipes and the pid */
442 *infdptr = inpfd[pipe_write];
443 *outfdptr = outpfd[pipe_read];
447 /* Fork failed; reset fork errno before returning */
449 (void)close(inpfd[pipe_write]);
450 (void)close(outpfd[pipe_read]);
458 /*************************************************
459 * Create child process without uid change *
460 *************************************************/
462 /* This function is a wrapper for child_open_uid() that doesn't have the uid,
463 gid and working directory changing arguments. The function is provided so as to
464 have a clean interface for use from local_scan(), but also saves writing NULL
465 arguments several calls that would otherwise use child_open_uid().
468 argv the argv for exec in the new process
469 envp the envp for exec in the new process
470 newumask umask to set in the new process
471 infdptr pointer to int into which the fd of the stdin of the new process
473 outfdptr pointer to int into which the fd of the stdout/stderr of the new
475 make_leader if TRUE, make the new process a process group leader
476 purpose for debug: reason for running the task
478 Returns: the pid of the created process or -1 if anything has gone wrong
482 child_open_function(uschar **argv, uschar **envp, int newumask, int *infdptr,
483 int *outfdptr, BOOL make_leader, const uschar * purpose)
485 return child_open_uid(CUSS argv, CUSS envp, newumask, NULL, NULL,
486 infdptr, outfdptr, NULL, make_leader, purpose);
492 /*************************************************
493 * Close down child process *
494 *************************************************/
496 /* Wait for the given process to finish, with optional timeout.
499 pid: the pid to wait for
500 timeout: maximum time to wait; 0 means for as long as it takes
502 Returns: >= 0 process terminated by exiting; value is process
503 ending status; if an execve() failed, the value
504 is typically 127 (defined as EX_EXECFAILED)
505 < 0 & > -256 process was terminated by a signal; value is the
506 negation of the signal number
508 -257 other error in wait(); errno still set
512 child_close(pid_t pid, int timeout)
518 sigalrm_seen = FALSE;
525 pid_t rc = waitpid(pid, &status, 0);
528 int lowbyte = status & 255;
529 yield = lowbyte == 0 ? (status >> 8) & 255 : -lowbyte;
534 /* This "shouldn't happen" test does happen on MacOS: for some reason
535 I do not understand we seems to get an alarm signal despite not having
536 an active alarm set. There seems to be only one, so just go round again. */
538 if (errno == EINTR && sigalrm_seen && timeout <= 0) continue;
540 yield = (errno == EINTR && sigalrm_seen) ? -256 : -257;
545 if (timeout > 0) ALARM_CLR(0);
547 signal(SIGCHLD, oldsignal); /* restore */