1 /* $NetBSD: do_command.c,v 1.11 2017/09/28 02:32:51 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 1.11 2017/09/28 02:32:51 christos Exp $"); 29 #endif 30 #endif 31 32 #include "cron.h" 33 #include <unistd.h> 34 35 static int child_process(entry *); 36 static int safe_p(const char *, const char *); 37 38 void 39 do_command(entry *e, user *u) { 40 int retval; 41 42 Debug(DPROC, ("[%ld] do_command(%s, (%s,%ld,%ld))\n", 43 (long)getpid(), e->cmd, u->name, 44 (long)e->pwd->pw_uid, (long)e->pwd->pw_gid)); 45 46 /* fork to become asynchronous -- parent process is done immediately, 47 * and continues to run the normal cron code, which means return to 48 * tick(). the child and grandchild don't leave this function, alive. 49 * 50 * vfork() is unsuitable, since we have much to do, and the parent 51 * needs to be able to run off and fork other processes. 52 */ 53 switch (fork()) { 54 case -1: 55 log_it("CRON", getpid(), "error", "can't fork"); 56 break; 57 case 0: 58 /* child process */ 59 acquire_daemonlock(1); 60 retval = child_process(e); 61 Debug(DPROC, ("[%ld] child process done (rc=%d), exiting\n", 62 (long)getpid(), retval)); 63 _exit(retval); 64 break; 65 default: 66 /* parent process */ 67 break; 68 } 69 Debug(DPROC, ("[%ld] main process returning to work\n",(long)getpid())); 70 } 71 72 static void 73 sigchld_handler(int signo) { 74 for (;;) { 75 WAIT_T waiter; 76 PID_T pid = waitpid(-1, &waiter, WNOHANG); 77 78 switch (pid) { 79 case -1: 80 if (errno == EINTR) 81 continue; 82 case 0: 83 return; 84 default: 85 break; 86 } 87 } 88 } 89 90 static void 91 write_data(char *volatile input_data, int *stdin_pipe, int *stdout_pipe) 92 { 93 FILE *out = fdopen(stdin_pipe[WRITE_PIPE], "w"); 94 int need_newline = FALSE; 95 int escaped = FALSE; 96 int ch; 97 98 Debug(DPROC, ("[%ld] child2 sending data to grandchild\n", 99 (long)getpid())); 100 101 #ifdef USE_PAM 102 cron_pam_child_close(); 103 #else 104 log_close(); 105 #endif 106 107 /* close the pipe we don't use, since we inherited it and 108 * are part of its reference count now. 109 */ 110 (void)close(stdout_pipe[READ_PIPE]); 111 112 /* translation: 113 * \% -> % 114 * % -> \n 115 * \x -> \x for all x != % 116 */ 117 while ((ch = *input_data++) != '\0') { 118 if (escaped) { 119 if (ch != '%') 120 (void)putc('\\', out); 121 } else { 122 if (ch == '%') 123 ch = '\n'; 124 } 125 126 if (!(escaped = (ch == '\\'))) { 127 (void)putc(ch, out); 128 need_newline = (ch != '\n'); 129 } 130 } 131 if (escaped) 132 (void)putc('\\', out); 133 if (need_newline) 134 (void)putc('\n', out); 135 136 /* close the pipe, causing an EOF condition. fclose causes 137 * stdin_pipe[WRITE_PIPE] to be closed, too. 138 */ 139 (void)fclose(out); 140 141 Debug(DPROC, ("[%ld] child2 done sending to grandchild\n", 142 (long)getpid())); 143 } 144 145 static int 146 read_data(entry *e, const char *mailto, const char *usernm, char **envp, 147 int *stdout_pipe) 148 { 149 FILE *in = fdopen(stdout_pipe[READ_PIPE], "r"); 150 FILE *mail = NULL; 151 int bytes = 1; 152 int status = 0; 153 int ch = getc(in); 154 int retval = 0; 155 sig_t oldchld = NULL; 156 157 if (ch == EOF) 158 goto out; 159 160 Debug(DPROC|DEXT, ("[%ld] got data (%x:%c) from grandchild\n", 161 (long)getpid(), ch, ch)); 162 163 /* get name of recipient. this is MAILTO if set to a 164 * valid local username; USER otherwise. 165 */ 166 if (mailto) { 167 /* MAILTO was present in the environment 168 */ 169 if (!*mailto) { 170 /* ... but it's empty. set to NULL 171 */ 172 mailto = NULL; 173 } 174 } else { 175 /* MAILTO not present, set to USER. 176 */ 177 mailto = usernm; 178 } 179 180 /* 181 * Unsafe, disable mailing. 182 */ 183 if (!safe_p(usernm, mailto)) 184 mailto = NULL; 185 186 /* if we are supposed to be mailing, MAILTO will 187 * be non-NULL. only in this case should we set 188 * up the mail command and subjects and stuff... 189 */ 190 191 if (mailto) { 192 char **env; 193 char mailcmd[MAX_COMMAND]; 194 char hostname[MAXHOSTNAMELEN + 1]; 195 196 (void)gethostname(hostname, MAXHOSTNAMELEN); 197 if (strlens(MAILFMT, MAILARG, NULL) + 1 >= sizeof mailcmd) { 198 log_it(usernm, getpid(), "MAIL", "mailcmd too long"); 199 retval = ERROR_EXIT; 200 goto out; 201 } 202 (void)snprintf(mailcmd, sizeof(mailcmd), MAILFMT, MAILARG); 203 oldchld = signal(SIGCHLD, SIG_DFL); 204 if (!(mail = cron_popen(mailcmd, "w", e->pwd))) { 205 log_itx(usernm, getpid(), "MAIL", 206 "cannot run `%s'", mailcmd); 207 (void) signal(SIGCHLD, oldchld); 208 retval = ERROR_EXIT; 209 goto out; 210 } 211 (void)fprintf(mail, "From: root (Cron Daemon)\n"); 212 (void)fprintf(mail, "To: %s\n", mailto); 213 (void)fprintf(mail, "Subject: Cron <%s@%s> %s\n", 214 usernm, hostname, e->cmd); 215 (void)fprintf(mail, "Auto-Submitted: auto-generated\n"); 216 #ifdef MAIL_DATE 217 (void)fprintf(mail, "Date: %s\n", arpadate(&StartTime)); 218 #endif /*MAIL_DATE*/ 219 for (env = envp; *env; env++) 220 (void)fprintf(mail, "X-Cron-Env: <%s>\n", *env); 221 (void)fprintf(mail, "\n"); 222 223 /* this was the first char from the pipe 224 */ 225 (void)putc(ch, mail); 226 } 227 228 /* we have to read the input pipe no matter whether 229 * we mail or not, but obviously we only write to 230 * mail pipe if we ARE mailing. 231 */ 232 233 while (EOF != (ch = getc(in))) { 234 bytes++; 235 if (mailto) 236 (void)putc(ch, mail); 237 } 238 239 /* only close pipe if we opened it -- i.e., we're 240 * mailing... 241 */ 242 243 if (mailto) { 244 Debug(DPROC, ("[%ld] closing pipe to mail\n", (long)getpid())); 245 /* Note: the pclose will probably see 246 * the termination of the grandchild 247 * in addition to the mail process, since 248 * it (the grandchild) is likely to exit 249 * after closing its stdout. 250 */ 251 status = cron_pclose(mail); 252 (void) signal(SIGCHLD, oldchld); 253 } 254 255 /* if there was output and we could not mail it, 256 * log the facts so the poor user can figure out 257 * what's going on. 258 */ 259 if (mailto && status) { 260 log_itx(usernm, getpid(), "MAIL", 261 "mailed %d byte%s of output to `%s' but" 262 " got status %#04x", bytes, 263 bytes == 1 ? "" : "s", mailto, status); 264 } 265 266 out: 267 Debug(DPROC, ("[%ld] got EOF from grandchild\n", (long)getpid())); 268 269 (void)fclose(in); /* also closes stdout_pipe[READ_PIPE] */ 270 return retval; 271 } 272 273 extern char **environ; 274 static int 275 child_process(entry *e) { 276 int stdin_pipe[2], stdout_pipe[2]; 277 char * volatile input_data; 278 char *homedir, *usernm, * volatile mailto; 279 struct sigaction sact; 280 char **envp = e->envp; 281 int retval = OK_EXIT; 282 283 Debug(DPROC, ("[%ld] child_process('%s')\n", (long)getpid(), e->cmd)); 284 285 setproctitle("running job"); 286 287 /* discover some useful and important environment settings 288 */ 289 usernm = e->pwd->pw_name; 290 mailto = env_get("MAILTO", envp); 291 292 memset(&sact, 0, sizeof(sact)); 293 sigemptyset(&sact.sa_mask); 294 sact.sa_flags = 0; 295 #ifdef SA_RESTART 296 sact.sa_flags |= SA_RESTART; 297 #endif 298 sact.sa_handler = sigchld_handler; 299 (void) sigaction(SIGCHLD, &sact, NULL); 300 301 /* create some pipes to talk to our future child 302 */ 303 if (pipe(stdin_pipe) == -1) /* child's stdin */ 304 log_it("CRON", getpid(), "error", "create child stdin pipe"); 305 if (pipe(stdout_pipe) == -1) /* child's stdout */ 306 log_it("CRON", getpid(), "error", "create child stdout pipe"); 307 308 /* since we are a forked process, we can diddle the command string 309 * we were passed -- nobody else is going to use it again, right? 310 * 311 * if a % is present in the command, previous characters are the 312 * command, and subsequent characters are the additional input to 313 * the command. An escaped % will have the escape character stripped 314 * from it. Subsequent %'s will be transformed into newlines, 315 * but that happens later. 316 */ 317 /*local*/{ 318 int escaped = FALSE; 319 int ch; 320 char *p; 321 322 /* translation: 323 * \% -> % 324 * % -> end of command, following is command input. 325 * \x -> \x for all x != % 326 */ 327 input_data = p = e->cmd; 328 while ((ch = *input_data++) != '\0') { 329 if (escaped) { 330 if (ch != '%') 331 *p++ = '\\'; 332 } else { 333 if (ch == '%') { 334 break; 335 } 336 } 337 338 if (!(escaped = (ch == '\\'))) { 339 *p++ = (char)ch; 340 } 341 } 342 if (ch == '\0') { 343 /* move pointer back, so that code below 344 * won't think we encountered % sequence */ 345 input_data--; 346 } 347 if (escaped) 348 *p++ = '\\'; 349 350 *p = '\0'; 351 } 352 353 #ifdef USE_PAM 354 if (!cron_pam_start(usernm)) 355 return ERROR_EXIT; 356 357 if (!(envp = cron_pam_getenvlist(envp))) { 358 retval = ERROR_EXIT; 359 goto child_process_end; 360 } 361 #endif 362 363 /* fork again, this time so we can exec the user's command. 364 */ 365 switch (vfork()) { 366 case -1: 367 retval = ERROR_EXIT; 368 goto child_process_end; 369 /*NOTREACHED*/ 370 case 0: 371 Debug(DPROC, ("[%ld] grandchild process vfork()'ed\n", 372 (long)getpid())); 373 374 /* write a log message. we've waited this long to do it 375 * because it was not until now that we knew the PID that 376 * the actual user command shell was going to get and the 377 * PID is part of the log message. 378 */ 379 if ((e->flags & DONT_LOG) == 0) { 380 char *x = mkprints(e->cmd, strlen(e->cmd)); 381 382 log_it(usernm, getpid(), "CMD START", x); 383 free(x); 384 } 385 386 /* that's the last thing we'll log. close the log files. 387 */ 388 log_close(); 389 390 /* get new pgrp, void tty, etc. 391 */ 392 if (setsid() == -1) 393 syslog(LOG_ERR, "setsid() failure: %m"); 394 395 /* close the pipe ends that we won't use. this doesn't affect 396 * the parent, who has to read and write them; it keeps the 397 * kernel from recording us as a potential client TWICE -- 398 * which would keep it from sending SIGPIPE in otherwise 399 * appropriate circumstances. 400 */ 401 (void)close(stdin_pipe[WRITE_PIPE]); 402 (void)close(stdout_pipe[READ_PIPE]); 403 404 /* grandchild process. make std{in,out} be the ends of 405 * pipes opened by our daddy; make stderr go to stdout. 406 */ 407 if (stdin_pipe[READ_PIPE] != STDIN) { 408 (void)dup2(stdin_pipe[READ_PIPE], STDIN); 409 (void)close(stdin_pipe[READ_PIPE]); 410 } 411 if (stdout_pipe[WRITE_PIPE] != STDOUT) { 412 (void)dup2(stdout_pipe[WRITE_PIPE], STDOUT); 413 (void)close(stdout_pipe[WRITE_PIPE]); 414 } 415 (void)dup2(STDOUT, STDERR); 416 417 /* set our directory, uid and gid. Set gid first, since once 418 * we set uid, we've lost root privledges. 419 */ 420 #ifdef LOGIN_CAP 421 { 422 #ifdef BSD_AUTH 423 auth_session_t *as; 424 #endif 425 login_cap_t *lc; 426 char *p; 427 428 if ((lc = login_getclass(e->pwd->pw_class)) == NULL) { 429 warnx("unable to get login class for `%s'", 430 e->pwd->pw_name); 431 _exit(ERROR_EXIT); 432 } 433 if (setusercontext(lc, e->pwd, e->pwd->pw_uid, LOGIN_SETALL) < 0) { 434 warnx("setusercontext failed for `%s'", 435 e->pwd->pw_name); 436 _exit(ERROR_EXIT); 437 } 438 #ifdef BSD_AUTH 439 as = auth_open(); 440 if (as == NULL || auth_setpwd(as, e->pwd) != 0) { 441 warn("can't malloc"); 442 _exit(ERROR_EXIT); 443 } 444 if (auth_approval(as, lc, usernm, "cron") <= 0) { 445 warnx("approval failed for `%s'", 446 e->pwd->pw_name); 447 _exit(ERROR_EXIT); 448 } 449 auth_close(as); 450 #endif /* BSD_AUTH */ 451 login_close(lc); 452 453 /* If no PATH specified in crontab file but 454 * we just added one via login.conf, add it to 455 * the crontab environment. 456 */ 457 if (env_get("PATH", envp) == NULL && environ != NULL) { 458 if ((p = getenv("PATH")) != NULL) 459 envp = env_set(envp, p); 460 } 461 } 462 #else 463 if (setgid(e->pwd->pw_gid) != 0) { 464 syslog(LOG_ERR, "setgid(%d) failed for %s: %m", 465 e->pwd->pw_gid, e->pwd->pw_name); 466 _exit(ERROR_EXIT); 467 } 468 if (initgroups(usernm, e->pwd->pw_gid) != 0) { 469 syslog(LOG_ERR, "initgroups(%s, %d) failed for %s: %m", 470 usernm, e->pwd->pw_gid, e->pwd->pw_name); 471 _exit(ERROR_EXIT); 472 } 473 #if (defined(BSD)) && (BSD >= 199103) 474 if (setlogin(usernm) < 0) { 475 syslog(LOG_ERR, "setlogin(%s) failure for %s: %m", 476 usernm, e->pwd->pw_name); 477 _exit(ERROR_EXIT); 478 } 479 #endif /* BSD */ 480 #ifdef USE_PAM 481 if (!cron_pam_setcred()) 482 _exit(ERROR_EXIT); 483 cron_pam_child_close(); 484 #endif 485 if (setuid(e->pwd->pw_uid) != 0) { 486 syslog(LOG_ERR, "setuid(%d) failed for %s: %m", 487 e->pwd->pw_uid, e->pwd->pw_name); 488 _exit(ERROR_EXIT); 489 } 490 /* we aren't root after this... */ 491 #endif /* LOGIN_CAP */ 492 homedir = env_get("HOME", envp); 493 if (chdir(homedir) != 0) { 494 syslog(LOG_ERR, "chdir(%s) $HOME failed for %s: %m", 495 homedir, e->pwd->pw_name); 496 _exit(ERROR_EXIT); 497 } 498 499 #ifdef USE_SIGCHLD 500 /* our grandparent is watching for our death by catching 501 * SIGCHLD. the parent is ignoring SIGCHLD's; we want 502 * to restore default behaviour. 503 */ 504 (void) signal(SIGCHLD, SIG_DFL); 505 #endif 506 (void) signal(SIGPIPE, SIG_DFL); 507 (void) signal(SIGUSR1, SIG_DFL); 508 (void) signal(SIGHUP, SIG_DFL); 509 510 /* 511 * Exec the command. 512 */ 513 { 514 char *shell = env_get("SHELL", envp); 515 516 # if DEBUGGING 517 if (DebugFlags & DTEST) { 518 (void)fprintf(stderr, 519 "debug DTEST is on, not exec'ing command.\n"); 520 (void)fprintf(stderr, 521 "\tcmd='%s' shell='%s'\n", e->cmd, shell); 522 _exit(OK_EXIT); 523 } 524 # endif /*DEBUGGING*/ 525 (void)execle(shell, shell, "-c", e->cmd, NULL, envp); 526 warn("execl: couldn't exec `%s'", shell); 527 _exit(ERROR_EXIT); 528 } 529 break; 530 default: 531 /* parent process */ 532 break; 533 } 534 535 /* middle process, child of original cron, parent of process running 536 * the user's command. 537 */ 538 539 Debug(DPROC, ("[%ld] child continues, closing pipes\n",(long)getpid())); 540 541 /* close the ends of the pipe that will only be referenced in the 542 * grandchild process... 543 */ 544 (void)close(stdin_pipe[READ_PIPE]); 545 (void)close(stdout_pipe[WRITE_PIPE]); 546 547 /* 548 * write, to the pipe connected to child's stdin, any input specified 549 * after a % in the crontab entry. while we copy, convert any 550 * additional %'s to newlines. when done, if some characters were 551 * written and the last one wasn't a newline, write a newline. 552 * 553 * Note that if the input data won't fit into one pipe buffer (2K 554 * or 4K on most BSD systems), and the child doesn't read its stdin, 555 * we would block here. thus we must fork again. 556 */ 557 558 if (*input_data) { 559 switch (fork()) { 560 case 0: 561 write_data(input_data, stdin_pipe, stdout_pipe); 562 exit(EXIT_SUCCESS); 563 case -1: 564 retval = ERROR_EXIT; 565 goto child_process_end; 566 default: 567 break; 568 } 569 } 570 571 /* close the pipe to the grandkiddie's stdin, since its wicked uncle 572 * ernie back there has it open and will close it when he's done. 573 */ 574 (void)close(stdin_pipe[WRITE_PIPE]); 575 576 /* 577 * read output from the grandchild. it's stderr has been redirected to 578 * it's stdout, which has been redirected to our pipe. if there is any 579 * output, we'll be mailing it to the user whose crontab this is... 580 * when the grandchild exits, we'll get EOF. 581 */ 582 583 Debug(DPROC, ("[%ld] child reading output from grandchild\n", 584 (long)getpid())); 585 586 retval = read_data(e, mailto, usernm, envp, stdout_pipe); 587 if (retval) 588 goto child_process_end; 589 590 591 /* wait for children to die. 592 */ 593 sigchld_handler(0); 594 595 /* Log the time when we finished deadling with the job */ 596 /*local*/{ 597 char *x = mkprints(e->cmd, strlen(e->cmd)); 598 599 log_it(usernm, getpid(), "CMD FINISH", x); 600 free(x); 601 } 602 603 child_process_end: 604 #ifdef USE_PAM 605 cron_pam_finish(); 606 #endif 607 return retval; 608 } 609 610 static int 611 safe_p(const char *usernm, const char *s) { 612 static const char safe_delim[] = "@!:%-.,"; /* conservative! */ 613 const char *t; 614 int ch, first; 615 616 for (t = s, first = 1; (ch = *t++) != '\0'; first = 0) { 617 if (isascii(ch) && isprint(ch) && 618 (isalnum(ch) || (!first && strchr(safe_delim, ch)))) 619 continue; 620 log_it(usernm, getpid(), "UNSAFE", s); 621 return (FALSE); 622 } 623 return (TRUE); 624 } 625