1 /* $NetBSD: do_command.c,v 1.2 2010/05/06 18:53:17 christos Exp $ */ 2 3 /* Copyright 1988,1990,1993,1994 by Paul Vixie 4 * All rights reserved 5 */ 6 7 /* 8 * Copyright (c) 2004 by Internet Systems Consortium, Inc. ("ISC") 9 * Copyright (c) 1997,2000 by Internet Software Consortium, Inc. 10 * 11 * Permission to use, copy, modify, and distribute this software for any 12 * purpose with or without fee is hereby granted, provided that the above 13 * copyright notice and this permission notice appear in all copies. 14 * 15 * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES 16 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF 17 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR 18 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES 19 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN 20 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT 21 * OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. 22 */ 23 #include <sys/cdefs.h> 24 #if !defined(lint) && !defined(LINT) 25 #if 0 26 static char rcsid[] = "Id: do_command.c,v 1.9 2004/01/23 18:56:42 vixie Exp"; 27 #else 28 __RCSID("$NetBSD: do_command.c,v 1.2 2010/05/06 18:53:17 christos Exp $"); 29 #endif 30 #endif 31 32 #include "cron.h" 33 #include <unistd.h> 34 35 static void child_process(entry *); 36 static int safe_p(const char *, const char *); 37 38 void 39 do_command(entry *e, user *u) { 40 Debug(DPROC, ("[%ld] do_command(%s, (%s,%ld,%ld))\n", 41 (long)getpid(), e->cmd, u->name, 42 (long)e->pwd->pw_uid, (long)e->pwd->pw_gid)); 43 44 /* fork to become asynchronous -- parent process is done immediately, 45 * and continues to run the normal cron code, which means return to 46 * tick(). the child and grandchild don't leave this function, alive. 47 * 48 * vfork() is unsuitable, since we have much to do, and the parent 49 * needs to be able to run off and fork other processes. 50 */ 51 switch (fork()) { 52 case -1: 53 log_it("CRON", getpid(), "error", "can't fork"); 54 break; 55 case 0: 56 /* child process */ 57 acquire_daemonlock(1); 58 child_process(e); 59 Debug(DPROC, ("[%ld] child process done, exiting\n", 60 (long)getpid())); 61 _exit(OK_EXIT); 62 break; 63 default: 64 /* parent process */ 65 break; 66 } 67 Debug(DPROC, ("[%ld] main process returning to work\n",(long)getpid())); 68 } 69 70 static void 71 child_process(entry *e) { 72 int stdin_pipe[2], stdout_pipe[2]; 73 char * volatile input_data; 74 char *usernm, * volatile mailto; 75 int children = 0; 76 77 Debug(DPROC, ("[%ld] child_process('%s')\n", (long)getpid(), e->cmd)); 78 79 setproctitle("running job"); 80 81 /* discover some useful and important environment settings 82 */ 83 usernm = e->pwd->pw_name; 84 mailto = env_get("MAILTO", e->envp); 85 86 /* our parent is watching for our death by catching SIGCHLD. we 87 * do not care to watch for our children's deaths this way -- we 88 * use wait() explicitly. so we have to reset the signal (which 89 * was inherited from the parent). 90 */ 91 (void) signal(SIGCHLD, SIG_DFL); 92 93 /* create some pipes to talk to our future child 94 */ 95 if (pipe(stdin_pipe) == -1) /* child's stdin */ 96 log_it("CRON", getpid(), "error", "create child stdin pipe"); 97 if (pipe(stdout_pipe) == -1) /* child's stdout */ 98 log_it("CRON", getpid(), "error", "create child stdout pipe"); 99 100 /* since we are a forked process, we can diddle the command string 101 * we were passed -- nobody else is going to use it again, right? 102 * 103 * if a % is present in the command, previous characters are the 104 * command, and subsequent characters are the additional input to 105 * the command. An escaped % will have the escape character stripped 106 * from it. Subsequent %'s will be transformed into newlines, 107 * but that happens later. 108 */ 109 /*local*/{ 110 int escaped = FALSE; 111 int ch; 112 char *p; 113 114 /* translation: 115 * \% -> % 116 * % -> end of command, following is command input. 117 * \x -> \x for all x != % 118 */ 119 input_data = p = e->cmd; 120 while ((ch = *input_data++) != '\0') { 121 if (escaped) { 122 if (ch != '%') 123 *p++ = '\\'; 124 } else { 125 if (ch == '%') { 126 break; 127 } 128 } 129 130 if (!(escaped = (ch == '\\'))) { 131 *p++ = ch; 132 } 133 } 134 if (ch == '\0') { 135 /* move pointer back, so that code below 136 * won't think we encountered % sequence */ 137 input_data--; 138 } 139 if (escaped) 140 *p++ = '\\'; 141 142 *p = '\0'; 143 } 144 145 /* fork again, this time so we can exec the user's command. 146 */ 147 switch (vfork()) { 148 case -1: 149 log_it("CRON", getpid(), "error", "can't vfork"); 150 exit(ERROR_EXIT); 151 /*NOTREACHED*/ 152 case 0: 153 Debug(DPROC, ("[%ld] grandchild process vfork()'ed\n", 154 (long)getpid())); 155 156 /* write a log message. we've waited this long to do it 157 * because it was not until now that we knew the PID that 158 * the actual user command shell was going to get and the 159 * PID is part of the log message. 160 */ 161 if ((e->flags & DONT_LOG) == 0) { 162 char *x = mkprints(e->cmd, strlen(e->cmd)); 163 164 log_it(usernm, getpid(), "CMD START", x); 165 free(x); 166 } 167 168 /* that's the last thing we'll log. close the log files. 169 */ 170 log_close(); 171 172 /* get new pgrp, void tty, etc. 173 */ 174 if (setsid() == -1) 175 syslog(LOG_ERR, "setsid() failure: %m"); 176 177 /* close the pipe ends that we won't use. this doesn't affect 178 * the parent, who has to read and write them; it keeps the 179 * kernel from recording us as a potential client TWICE -- 180 * which would keep it from sending SIGPIPE in otherwise 181 * appropriate circumstances. 182 */ 183 (void)close(stdin_pipe[WRITE_PIPE]); 184 (void)close(stdout_pipe[READ_PIPE]); 185 186 /* grandchild process. make std{in,out} be the ends of 187 * pipes opened by our daddy; make stderr go to stdout. 188 */ 189 if (stdin_pipe[READ_PIPE] != STDIN) { 190 (void)dup2(stdin_pipe[READ_PIPE], STDIN); 191 (void)close(stdin_pipe[READ_PIPE]); 192 } 193 if (stdout_pipe[WRITE_PIPE] != STDOUT) { 194 (void)dup2(stdout_pipe[WRITE_PIPE], STDOUT); 195 (void)close(stdout_pipe[WRITE_PIPE]); 196 } 197 (void)dup2(STDOUT, STDERR); 198 199 /* set our directory, uid and gid. Set gid first, since once 200 * we set uid, we've lost root privledges. 201 */ 202 #ifdef LOGIN_CAP 203 { 204 #ifdef BSD_AUTH 205 auth_session_t *as; 206 #endif 207 login_cap_t *lc; 208 char *p; 209 210 if ((lc = login_getclass(e->pwd->pw_class)) == NULL) { 211 warnx("unable to get login class for `%s'", 212 e->pwd->pw_name); 213 _exit(ERROR_EXIT); 214 } 215 if (setusercontext(lc, e->pwd, e->pwd->pw_uid, LOGIN_SETALL) < 0) { 216 warnx("setusercontext failed for `%s'", 217 e->pwd->pw_name); 218 _exit(ERROR_EXIT); 219 } 220 #ifdef BSD_AUTH 221 as = auth_open(); 222 if (as == NULL || auth_setpwd(as, e->pwd) != 0) { 223 warn("can't malloc"); 224 _exit(ERROR_EXIT); 225 } 226 if (auth_approval(as, lc, usernm, "cron") <= 0) { 227 warnx("approval failed for `%s'", 228 e->pwd->pw_name); 229 _exit(ERROR_EXIT); 230 } 231 auth_close(as); 232 #endif /* BSD_AUTH */ 233 login_close(lc); 234 235 /* If no PATH specified in crontab file but 236 * we just added one via login.conf, add it to 237 * the crontab environment. 238 */ 239 if (env_get("PATH", e->envp) == NULL) { 240 if ((p = getenv("PATH")) != NULL) 241 e->envp = env_set(e->envp, p); 242 } 243 } 244 #else 245 if (setgid(e->pwd->pw_gid) != 0) { 246 syslog(LOG_ERR, "setgid failed"); 247 _exit(ERROR_EXIT); 248 } 249 if (initgroups(usernm, e->pwd->pw_gid) != 0) { 250 syslog(LOG_ERR, "initgroups failed"); 251 _exit(ERROR_EXIT); 252 } 253 #if (defined(BSD)) && (BSD >= 199103) 254 if (setlogin(usernm) < 0) { 255 syslog(LOG_ERR, "setlogin() failure: %m"); 256 _exit(ERROR_EXIT); 257 } 258 259 setlogin(usernm); 260 #endif /* BSD */ 261 if (setuid(e->pwd->pw_uid) != 0) { 262 syslog(LOG_ERR, "setuid failed"); 263 _exit(ERROR_EXIT); 264 } 265 /* we aren't root after this... */ 266 #endif /* LOGIN_CAP */ 267 268 if (chdir(env_get("HOME", e->envp)) != 0) { 269 syslog(LOG_ERR, "chdir $HOME failed"); 270 _exit(ERROR_EXIT); 271 } 272 273 #ifdef USE_SIGCHLD 274 /* our grandparent is watching for our death by catching 275 * SIGCHLD. the parent is ignoring SIGCHLD's; we want 276 * to restore default behaviour. 277 */ 278 (void) signal(SIGCHLD, SIG_DFL); 279 #endif 280 (void) signal(SIGHUP, SIG_DFL); 281 282 /* 283 * Exec the command. 284 */ 285 { 286 char *shell = env_get("SHELL", e->envp); 287 288 # if DEBUGGING 289 if (DebugFlags & DTEST) { 290 (void)fprintf(stderr, 291 "debug DTEST is on, not exec'ing command.\n"); 292 (void)fprintf(stderr, 293 "\tcmd='%s' shell='%s'\n", e->cmd, shell); 294 _exit(OK_EXIT); 295 } 296 # endif /*DEBUGGING*/ 297 (void)execle(shell, shell, "-c", e->cmd, NULL, e->envp); 298 warn("execl: couldn't exec `%s'", shell); 299 _exit(ERROR_EXIT); 300 } 301 break; 302 default: 303 /* parent process */ 304 break; 305 } 306 307 children++; 308 309 /* middle process, child of original cron, parent of process running 310 * the user's command. 311 */ 312 313 Debug(DPROC, ("[%ld] child continues, closing pipes\n",(long)getpid())); 314 315 /* close the ends of the pipe that will only be referenced in the 316 * grandchild process... 317 */ 318 (void)close(stdin_pipe[READ_PIPE]); 319 (void)close(stdout_pipe[WRITE_PIPE]); 320 321 /* 322 * write, to the pipe connected to child's stdin, any input specified 323 * after a % in the crontab entry. while we copy, convert any 324 * additional %'s to newlines. when done, if some characters were 325 * written and the last one wasn't a newline, write a newline. 326 * 327 * Note that if the input data won't fit into one pipe buffer (2K 328 * or 4K on most BSD systems), and the child doesn't read its stdin, 329 * we would block here. thus we must fork again. 330 */ 331 332 if (*input_data && fork() == 0) { 333 FILE *out = fdopen(stdin_pipe[WRITE_PIPE], "w"); 334 int need_newline = FALSE; 335 int escaped = FALSE; 336 int ch; 337 338 Debug(DPROC, ("[%ld] child2 sending data to grandchild\n", 339 (long)getpid())); 340 341 /* close the pipe we don't use, since we inherited it and 342 * are part of its reference count now. 343 */ 344 (void)close(stdout_pipe[READ_PIPE]); 345 346 /* translation: 347 * \% -> % 348 * % -> \n 349 * \x -> \x for all x != % 350 */ 351 while ((ch = *input_data++) != '\0') { 352 if (escaped) { 353 if (ch != '%') 354 (void)putc('\\', out); 355 } else { 356 if (ch == '%') 357 ch = '\n'; 358 } 359 360 if (!(escaped = (ch == '\\'))) { 361 (void)putc(ch, out); 362 need_newline = (ch != '\n'); 363 } 364 } 365 if (escaped) 366 (void)putc('\\', out); 367 if (need_newline) 368 (void)putc('\n', out); 369 370 /* close the pipe, causing an EOF condition. fclose causes 371 * stdin_pipe[WRITE_PIPE] to be closed, too. 372 */ 373 (void)fclose(out); 374 375 Debug(DPROC, ("[%ld] child2 done sending to grandchild\n", 376 (long)getpid())); 377 exit(0); 378 } 379 380 /* close the pipe to the grandkiddie's stdin, since its wicked uncle 381 * ernie back there has it open and will close it when he's done. 382 */ 383 (void)close(stdin_pipe[WRITE_PIPE]); 384 385 children++; 386 387 /* 388 * read output from the grandchild. it's stderr has been redirected to 389 * it's stdout, which has been redirected to our pipe. if there is any 390 * output, we'll be mailing it to the user whose crontab this is... 391 * when the grandchild exits, we'll get EOF. 392 */ 393 394 Debug(DPROC, ("[%ld] child reading output from grandchild\n", 395 (long)getpid())); 396 397 /*local*/{ 398 FILE *in = fdopen(stdout_pipe[READ_PIPE], "r"); 399 int ch = getc(in); 400 401 if (ch != EOF) { 402 FILE *mail = NULL; 403 int bytes = 1; 404 int status = 0; 405 406 Debug(DPROC|DEXT, 407 ("[%ld] got data (%x:%c) from grandchild\n", 408 (long)getpid(), ch, ch)); 409 410 /* get name of recipient. this is MAILTO if set to a 411 * valid local username; USER otherwise. 412 */ 413 if (mailto) { 414 /* MAILTO was present in the environment 415 */ 416 if (!*mailto) { 417 /* ... but it's empty. set to NULL 418 */ 419 mailto = NULL; 420 } 421 } else { 422 /* MAILTO not present, set to USER. 423 */ 424 mailto = usernm; 425 } 426 427 /* if we are supposed to be mailing, MAILTO will 428 * be non-NULL. only in this case should we set 429 * up the mail command and subjects and stuff... 430 */ 431 432 if (mailto && safe_p(usernm, mailto)) { 433 char **env; 434 char mailcmd[MAX_COMMAND]; 435 char hostname[MAXHOSTNAMELEN + 1]; 436 437 (void)gethostname(hostname, MAXHOSTNAMELEN); 438 if (strlens(MAILFMT, MAILARG, NULL) + 1 439 >= sizeof mailcmd) { 440 warnx("mailcmd too long"); 441 (void) _exit(ERROR_EXIT); 442 } 443 (void)snprintf(mailcmd, sizeof(mailcmd), 444 MAILFMT, MAILARG); 445 if (!(mail = cron_popen(mailcmd, "w", e->pwd))) { 446 warn("cannot run `%s'", mailcmd); 447 (void) _exit(ERROR_EXIT); 448 } 449 (void)fprintf(mail, 450 "From: root (Cron Daemon)\n"); 451 (void)fprintf(mail, "To: %s\n", mailto); 452 (void)fprintf(mail, 453 "Subject: Cron <%s@%s> %s\n", 454 usernm, first_word(hostname, "."), e->cmd); 455 (void)fprintf(mail, 456 "Auto-Submitted: auto-generated\n"); 457 #ifdef MAIL_DATE 458 (void)fprintf(mail, "Date: %s\n", 459 arpadate(&StartTime)); 460 #endif /*MAIL_DATE*/ 461 for (env = e->envp; *env; env++) 462 (void)fprintf(mail, 463 "X-Cron-Env: <%s>\n", *env); 464 (void)fprintf(mail, "\n"); 465 466 /* this was the first char from the pipe 467 */ 468 (void)putc(ch, mail); 469 } 470 471 /* we have to read the input pipe no matter whether 472 * we mail or not, but obviously we only write to 473 * mail pipe if we ARE mailing. 474 */ 475 476 while (EOF != (ch = getc(in))) { 477 bytes++; 478 if (mailto) 479 (void)putc(ch, mail); 480 } 481 482 /* only close pipe if we opened it -- i.e., we're 483 * mailing... 484 */ 485 486 if (mailto) { 487 Debug(DPROC, ("[%ld] closing pipe to mail\n", 488 (long)getpid())); 489 /* Note: the pclose will probably see 490 * the termination of the grandchild 491 * in addition to the mail process, since 492 * it (the grandchild) is likely to exit 493 * after closing its stdout. 494 */ 495 status = cron_pclose(mail); 496 } 497 498 /* if there was output and we could not mail it, 499 * log the facts so the poor user can figure out 500 * what's going on. 501 */ 502 if (mailto && status) { 503 char buf[MAX_TEMPSTR]; 504 505 (void)snprintf(buf, sizeof(buf), 506 "mailed %d byte%s of output but got status 0x%04x\n", 507 bytes, (bytes==1)?"":"s", 508 status); 509 log_it(usernm, getpid(), "MAIL", buf); 510 } 511 512 } /*if data from grandchild*/ 513 514 Debug(DPROC, ("[%ld] got EOF from grandchild\n", 515 (long)getpid())); 516 517 (void)fclose(in); /* also closes stdout_pipe[READ_PIPE] */ 518 } 519 520 /* wait for children to die. 521 */ 522 for (; children > 0; children--) { 523 WAIT_T waiter; 524 PID_T pid; 525 526 Debug(DPROC, ("[%ld] waiting for grandchild #%d to finish\n", 527 (long)getpid(), children)); 528 while ((pid = wait(&waiter)) < OK && errno == EINTR) 529 ; 530 if (pid < OK) { 531 Debug(DPROC, 532 ("[%ld] no more grandchildren--mail written?\n", 533 (long)getpid())); 534 break; 535 } 536 Debug(DPROC, ("[%ld] grandchild #%ld finished, status=%04x", 537 (long)getpid(), (long)pid, WEXITSTATUS(waiter))); 538 if (WIFSIGNALED(waiter) && WCOREDUMP(waiter)) 539 Debug(DPROC, (", dumped core")); 540 Debug(DPROC, ("\n")); 541 } 542 543 /* Log the time when we finished deadling with the job */ 544 /*local*/{ 545 char *x = mkprints(e->cmd, strlen(e->cmd)); 546 547 log_it(usernm, getpid(), "CMD FINISH", x); 548 free(x); 549 } 550 } 551 552 static int 553 safe_p(const char *usernm, const char *s) { 554 static const char safe_delim[] = "@!:%-.,"; /* conservative! */ 555 const char *t; 556 int ch, first; 557 558 for (t = s, first = 1; (ch = *t++) != '\0'; first = 0) { 559 if (isascii(ch) && isprint(ch) && 560 (isalnum(ch) || (!first && strchr(safe_delim, ch)))) 561 continue; 562 log_it(usernm, getpid(), "UNSAFE", s); 563 return (FALSE); 564 } 565 return (TRUE); 566 } 567