| 1 | /* $Cambridge: exim/src/src/child.c,v 1.6 2005/09/16 14:44:11 ph10 Exp $ */ |
| 2 | |
| 3 | /************************************************* |
| 4 | * Exim - an Internet mail transport agent * |
| 5 | *************************************************/ |
| 6 | |
| 7 | /* Copyright (c) University of Cambridge 1995 - 2005 */ |
| 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; |
| 35 | (void)close(newfd); |
| 36 | (void)dup2(oldfd, newfd); |
| 37 | (void)close(oldfd); |
| 38 | } |
| 39 | |
| 40 | |
| 41 | #ifndef STAND_ALONE |
| 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); |
| 204 | (void)close(pfd[pipe_write]); |
| 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; |
| 220 | (void)close(pfd[pipe_read]); |
| 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 | |
| 232 | (void)close(pfd[pipe_write]); |
| 233 | errno = save_errno; |
| 234 | return (pid_t)(-1); |
| 235 | } |
| 236 | #endif |
| 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. |
| 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. |
| 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 |
| 266 | |
| 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 | { |
| 283 | (void)close(inpfd[pipe_read]); |
| 284 | (void)close(inpfd[pipe_write]); |
| 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 | |
| 304 | (void)close(inpfd[pipe_write]); |
| 305 | force_fd(inpfd[pipe_read], 0); |
| 306 | |
| 307 | (void)close(outpfd[pipe_read]); |
| 308 | force_fd(outpfd[pipe_write], 1); |
| 309 | |
| 310 | (void)close(2); |
| 311 | (void)dup2(1, 2); |
| 312 | |
| 313 | /* Set the required environment. */ |
| 314 | |
| 315 | signal(SIGUSR1, SIG_IGN); |
| 316 | if (newgid != NULL && setgid(*newgid) < 0) goto CHILD_FAILED; |
| 317 | if (newuid != NULL && setuid(*newuid) < 0) goto CHILD_FAILED; |
| 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; |
| 341 | (void)close(inpfd[pipe_read]); |
| 342 | (void)close(outpfd[pipe_write]); |
| 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 | |
| 355 | (void)close(inpfd[pipe_write]); |
| 356 | (void)close(outpfd[pipe_read]); |
| 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, |
| 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(). |
| 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 */ |