1 /*- 2 * atrun.c - run jobs queued by at; run with root privileges. 3 * 4 * SPDX-License-Identifier: BSD-2-Clause 5 * 6 * Copyright (C) 1993, 1994 Thomas Koenig 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. The name of the author(s) may not be used to endorse or promote 14 * products derived from this software without specific prior written 15 * permission. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR(S) ``AS IS'' AND ANY EXPRESS OR 18 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 19 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 20 * IN NO EVENT SHALL THE AUTHOR(S) BE LIABLE FOR ANY DIRECT, INDIRECT, 21 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 22 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 23 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 24 * THEORY OF LIABILITY, WETHER IN CONTRACT, STRICT LIABILITY, OR TORT 25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 26 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 27 */ 28 29 /* System Headers */ 30 31 #include <sys/fcntl.h> 32 #include <sys/file.h> 33 #include <sys/types.h> 34 #include <sys/stat.h> 35 #ifdef __FreeBSD__ 36 #include <sys/sysctl.h> 37 #endif 38 #include <sys/wait.h> 39 #include <sys/param.h> 40 #include <ctype.h> 41 #include <dirent.h> 42 #include <err.h> 43 #include <grp.h> 44 #include <pwd.h> 45 #include <signal.h> 46 #include <stdarg.h> 47 #include <stddef.h> 48 #include <stdio.h> 49 #include <stdlib.h> 50 #include <string.h> 51 #include <syslog.h> 52 #include <time.h> 53 #include <unistd.h> 54 #ifdef __FreeBSD__ 55 #include <paths.h> 56 #else 57 #include <getopt.h> 58 #endif 59 #ifdef LOGIN_CAP 60 #include <login_cap.h> 61 #endif 62 #ifdef PAM 63 #include <security/pam_appl.h> 64 #include <security/openpam.h> 65 #endif 66 67 /* Local headers */ 68 69 #include "gloadavg.h" 70 #define MAIN 71 #include "privs.h" 72 73 /* Macros */ 74 75 #ifndef ATJOB_DIR 76 #define ATJOB_DIR "/usr/spool/atjobs/" 77 #endif 78 79 #ifndef ATSPOOL_DIR 80 #define ATSPOOL_DIR "/usr/spool/atspool/" 81 #endif 82 83 #ifndef LOADAVG_MX 84 #define LOADAVG_MX 1.5 85 #endif 86 87 /* File scope variables */ 88 89 static const char * const atrun = "atrun"; /* service name for syslog etc. */ 90 static int debug = 0; 91 92 void perr(const char *fmt, ...); 93 void perrx(const char *fmt, ...); 94 static void usage(void) __dead2; 95 96 /* Local functions */ 97 static int 98 write_string(int fd, const char* a) 99 { 100 return write(fd, a, strlen(a)); 101 } 102 103 #undef DEBUG_FORK 104 #ifdef DEBUG_FORK 105 static pid_t 106 myfork(void) 107 { 108 pid_t res; 109 res = fork(); 110 if (res == 0) 111 kill(getpid(),SIGSTOP); 112 return res; 113 } 114 115 #define fork myfork 116 #endif 117 118 static void 119 run_file(const char *filename, uid_t uid, gid_t gid) 120 { 121 /* Run a file by spawning off a process which redirects I/O, 122 * spawns a subshell, then waits for it to complete and sends 123 * mail to the user. 124 */ 125 pid_t pid; 126 int fd_out, fd_in; 127 int queue; 128 char mailbuf[MAXLOGNAME], fmt[64]; 129 char *mailname = NULL; 130 FILE *stream; 131 int send_mail = 0; 132 struct stat buf, lbuf; 133 off_t size; 134 struct passwd *pentry; 135 int fflags; 136 long nuid; 137 long ngid; 138 #ifdef PAM 139 pam_handle_t *pamh = NULL; 140 int pam_err; 141 struct pam_conv pamc = { 142 .conv = openpam_nullconv, 143 .appdata_ptr = NULL 144 }; 145 #endif 146 147 PRIV_START 148 149 if (chmod(filename, S_IRUSR) != 0) 150 { 151 perr("cannot change file permissions"); 152 } 153 154 PRIV_END 155 156 pid = fork(); 157 if (pid == -1) 158 perr("cannot fork"); 159 160 else if (pid != 0) 161 return; 162 163 /* Let's see who we mail to. Hopefully, we can read it from 164 * the command file; if not, send it to the owner, or, failing that, 165 * to root. 166 */ 167 168 pentry = getpwuid(uid); 169 if (pentry == NULL) 170 perrx("Userid %lu not found - aborting job %s", 171 (unsigned long) uid, filename); 172 173 #ifdef PAM 174 PRIV_START 175 176 pam_err = pam_start(atrun, pentry->pw_name, &pamc, &pamh); 177 if (pam_err != PAM_SUCCESS) 178 perrx("cannot start PAM: %s", pam_strerror(pamh, pam_err)); 179 180 pam_err = pam_acct_mgmt(pamh, PAM_SILENT); 181 /* Expired password shouldn't prevent the job from running. */ 182 if (pam_err != PAM_SUCCESS && pam_err != PAM_NEW_AUTHTOK_REQD) 183 perrx("Account %s (userid %lu) unavailable for job %s: %s", 184 pentry->pw_name, (unsigned long)uid, 185 filename, pam_strerror(pamh, pam_err)); 186 187 pam_end(pamh, pam_err); 188 189 PRIV_END 190 #endif /* PAM */ 191 192 PRIV_START 193 194 stream=fopen(filename, "r"); 195 196 PRIV_END 197 198 if (stream == NULL) 199 perr("cannot open input file %s", filename); 200 201 if ((fd_in = dup(fileno(stream))) <0) 202 perr("error duplicating input file descriptor"); 203 204 if (fstat(fd_in, &buf) == -1) 205 perr("error in fstat of input file descriptor"); 206 207 if (lstat(filename, &lbuf) == -1) 208 perr("error in fstat of input file"); 209 210 if (S_ISLNK(lbuf.st_mode)) 211 perrx("Symbolic link encountered in job %s - aborting", filename); 212 213 if ((lbuf.st_dev != buf.st_dev) || (lbuf.st_ino != buf.st_ino) || 214 (lbuf.st_uid != buf.st_uid) || (lbuf.st_gid != buf.st_gid) || 215 (lbuf.st_size!=buf.st_size)) 216 perrx("Somebody changed files from under us for job %s - aborting", 217 filename); 218 219 if (buf.st_nlink > 1) 220 perrx("Somebody is trying to run a linked script for job %s", filename); 221 222 if ((fflags = fcntl(fd_in, F_GETFD)) <0) 223 perr("error in fcntl"); 224 225 fcntl(fd_in, F_SETFD, fflags & ~FD_CLOEXEC); 226 227 snprintf(fmt, sizeof(fmt), 228 "#!/bin/sh\n# atrun uid=%%ld gid=%%ld\n# mail %%%ds %%d", 229 MAXLOGNAME - 1); 230 231 if (fscanf(stream, fmt, &nuid, &ngid, mailbuf, &send_mail) != 4) 232 perrx("File %s is in wrong format - aborting", filename); 233 234 if (mailbuf[0] == '-') 235 perrx("Illegal mail name %s in %s", mailbuf, filename); 236 237 mailname = mailbuf; 238 239 if (nuid != uid) 240 perrx("Job %s - userid %ld does not match file uid %lu", 241 filename, nuid, (unsigned long)uid); 242 243 if (ngid != gid) 244 perrx("Job %s - groupid %ld does not match file gid %lu", 245 filename, ngid, (unsigned long)gid); 246 247 fclose(stream); 248 249 if (chdir(ATSPOOL_DIR) < 0) 250 perr("cannot chdir to %s", ATSPOOL_DIR); 251 252 /* Create a file to hold the output of the job we are about to run. 253 * Write the mail header. 254 */ 255 if((fd_out=open(filename, 256 O_WRONLY | O_CREAT | O_EXCL, S_IWUSR | S_IRUSR)) < 0) 257 perr("cannot create output file"); 258 259 write_string(fd_out, "Subject: Output from your job "); 260 write_string(fd_out, filename); 261 write_string(fd_out, "\n\n"); 262 fstat(fd_out, &buf); 263 size = buf.st_size; 264 265 close(STDIN_FILENO); 266 close(STDOUT_FILENO); 267 close(STDERR_FILENO); 268 269 pid = fork(); 270 if (pid < 0) 271 perr("error in fork"); 272 273 else if (pid == 0) 274 { 275 char *nul = NULL; 276 char **nenvp = &nul; 277 278 /* Set up things for the child; we want standard input from the input file, 279 * and standard output and error sent to our output file. 280 */ 281 282 if (lseek(fd_in, (off_t) 0, SEEK_SET) < 0) 283 perr("error in lseek"); 284 285 if (dup(fd_in) != STDIN_FILENO) 286 perr("error in I/O redirection"); 287 288 if (dup(fd_out) != STDOUT_FILENO) 289 perr("error in I/O redirection"); 290 291 if (dup(fd_out) != STDERR_FILENO) 292 perr("error in I/O redirection"); 293 294 close(fd_in); 295 close(fd_out); 296 if (chdir(ATJOB_DIR) < 0) 297 perr("cannot chdir to %s", ATJOB_DIR); 298 299 queue = *filename; 300 301 PRIV_START 302 303 nice(tolower(queue) - 'a'); 304 305 #ifdef LOGIN_CAP 306 /* 307 * For simplicity and safety, set all aspects of the user context 308 * except for a selected subset: Don't set priority, which was 309 * set based on the queue file name according to the tradition. 310 * Don't bother to set environment, including path vars, either 311 * because it will be discarded anyway. Although the job file 312 * should set umask, preset it here just in case. 313 */ 314 if (setusercontext(NULL, pentry, uid, LOGIN_SETALL & 315 ~(LOGIN_SETPRIORITY | LOGIN_SETPATH | LOGIN_SETENV)) != 0) 316 exit(EXIT_FAILURE); /* setusercontext() logged the error */ 317 #else /* LOGIN_CAP */ 318 if (initgroups(pentry->pw_name,pentry->pw_gid)) 319 perr("cannot init group access list"); 320 321 if (setgid(gid) < 0 || setegid(pentry->pw_gid) < 0) 322 perr("cannot change group"); 323 324 if (setlogin(pentry->pw_name)) 325 perr("cannot set login name"); 326 327 if (setuid(uid) < 0 || seteuid(uid) < 0) 328 perr("cannot set user id"); 329 #endif /* LOGIN_CAP */ 330 331 if (chdir(pentry->pw_dir)) 332 chdir("/"); 333 334 if(execle("/bin/sh","sh",(char *) NULL, nenvp) != 0) 335 perr("exec failed for /bin/sh"); 336 337 PRIV_END 338 } 339 /* We're the parent. Let's wait. 340 */ 341 close(fd_in); 342 close(fd_out); 343 waitpid(pid, (int *) NULL, 0); 344 345 /* Send mail. Unlink the output file first, so it is deleted after 346 * the run. 347 */ 348 stat(filename, &buf); 349 if (open(filename, O_RDONLY) != STDIN_FILENO) 350 perr("open of jobfile failed"); 351 352 unlink(filename); 353 if ((buf.st_size != size) || send_mail) 354 { 355 PRIV_START 356 357 #ifdef LOGIN_CAP 358 /* 359 * This time set full context to run the mailer. 360 */ 361 if (setusercontext(NULL, pentry, uid, LOGIN_SETALL) != 0) 362 exit(EXIT_FAILURE); /* setusercontext() logged the error */ 363 #else /* LOGIN_CAP */ 364 if (initgroups(pentry->pw_name,pentry->pw_gid)) 365 perr("cannot init group access list"); 366 367 if (setgid(gid) < 0 || setegid(pentry->pw_gid) < 0) 368 perr("cannot change group"); 369 370 if (setlogin(pentry->pw_name)) 371 perr("cannot set login name"); 372 373 if (setuid(uid) < 0 || seteuid(uid) < 0) 374 perr("cannot set user id"); 375 #endif /* LOGIN_CAP */ 376 377 if (chdir(pentry->pw_dir)) 378 chdir("/"); 379 380 #ifdef __FreeBSD__ 381 execl(_PATH_SENDMAIL, "sendmail", "-F", "Atrun Service", 382 "-odi", "-oem", 383 mailname, (char *) NULL); 384 #else 385 execl(MAIL_CMD, MAIL_CMD, mailname, (char *) NULL); 386 #endif 387 perr("exec failed for mail command"); 388 389 PRIV_END 390 } 391 exit(EXIT_SUCCESS); 392 } 393 394 /* Global functions */ 395 396 /* Needed in gloadavg.c */ 397 void 398 perr(const char *fmt, ...) 399 { 400 const char * const fmtadd = ": %m"; 401 char nfmt[strlen(fmt) + strlen(fmtadd) + 1]; 402 va_list ap; 403 404 va_start(ap, fmt); 405 if (debug) 406 { 407 vwarn(fmt, ap); 408 } 409 else 410 { 411 snprintf(nfmt, sizeof(nfmt), "%s%s", fmt, fmtadd); 412 vsyslog(LOG_ERR, nfmt, ap); 413 } 414 va_end(ap); 415 416 exit(EXIT_FAILURE); 417 } 418 419 void 420 perrx(const char *fmt, ...) 421 { 422 va_list ap; 423 424 va_start(ap, fmt); 425 if (debug) 426 vwarnx(fmt, ap); 427 else 428 vsyslog(LOG_ERR, fmt, ap); 429 va_end(ap); 430 431 exit(EXIT_FAILURE); 432 } 433 434 int 435 main(int argc, char *argv[]) 436 { 437 /* Browse through ATJOB_DIR, checking all the jobfiles wether they should 438 * be executed and or deleted. The queue is coded into the first byte of 439 * the job filename, the date (in minutes since Eon) as a hex number in the 440 * following eight bytes, followed by a dot and a serial number. A file 441 * which has not been executed yet is denoted by its execute - bit set. 442 * For those files which are to be executed, run_file() is called, which forks 443 * off a child which takes care of I/O redirection, forks off another child 444 * for execution and yet another one, optionally, for sending mail. 445 * Files which already have run are removed during the next invocation. 446 */ 447 DIR *spool; 448 struct dirent *dirent; 449 struct stat buf; 450 unsigned long ctm; 451 unsigned long jobno; 452 char queue; 453 time_t now, run_time; 454 char batch_name[] = "Z2345678901234"; 455 uid_t batch_uid; 456 gid_t batch_gid; 457 int c; 458 int run_batch; 459 #ifdef __FreeBSD__ 460 size_t ncpusz; 461 double load_avg = -1; 462 int ncpu; 463 #else 464 double load_avg = LOADAVG_MX; 465 #endif 466 467 /* We don't need root privileges all the time; running under uid and gid daemon 468 * is fine. 469 */ 470 471 RELINQUISH_PRIVS_ROOT(DAEMON_UID, DAEMON_GID) 472 473 openlog(atrun, LOG_PID, LOG_CRON); 474 475 opterr = 0; 476 while((c=getopt(argc, argv, "dl:"))!= -1) 477 { 478 switch (c) 479 { 480 case 'l': 481 if (sscanf(optarg, "%lf", &load_avg) != 1) 482 perr("garbled option -l"); 483 #ifndef __FreeBSD__ 484 if (load_avg <= 0.) 485 load_avg = LOADAVG_MX; 486 #endif 487 break; 488 489 case 'd': 490 debug ++; 491 break; 492 493 case '?': 494 default: 495 usage(); 496 } 497 } 498 499 if (chdir(ATJOB_DIR) != 0) 500 perr("cannot change to %s", ATJOB_DIR); 501 502 #ifdef __FreeBSD__ 503 if (load_avg <= 0.) { 504 ncpusz = sizeof(size_t); 505 if (sysctlbyname("hw.ncpu", &ncpu, &ncpusz, NULL, 0) < 0) 506 ncpu = 1; 507 load_avg = LOADAVG_MX * ncpu; 508 } 509 #endif 510 511 /* Main loop. Open spool directory for reading and look over all the 512 * files in there. If the filename indicates that the job should be run 513 * and the x bit is set, fork off a child which sets its user and group 514 * id to that of the files and exec a /bin/sh which executes the shell 515 * script. Unlink older files if they should no longer be run. For 516 * deletion, their r bit has to be turned on. 517 * 518 * Also, pick the oldest batch job to run, at most one per invocation of 519 * atrun. 520 */ 521 if ((spool = opendir(".")) == NULL) 522 perr("cannot read %s", ATJOB_DIR); 523 524 if (flock(dirfd(spool), LOCK_EX) == -1) 525 perr("cannot lock %s", ATJOB_DIR); 526 527 now = time(NULL); 528 run_batch = 0; 529 batch_uid = (uid_t) -1; 530 batch_gid = (gid_t) -1; 531 532 while ((dirent = readdir(spool)) != NULL) { 533 if (stat(dirent->d_name,&buf) != 0) 534 perr("cannot stat in %s", ATJOB_DIR); 535 536 /* We don't want directories 537 */ 538 if (!S_ISREG(buf.st_mode)) 539 continue; 540 541 if (sscanf(dirent->d_name,"%c%5lx%8lx",&queue,&jobno,&ctm) != 3) 542 continue; 543 544 run_time = (time_t) ctm*60; 545 546 if ((S_IXUSR & buf.st_mode) && (run_time <=now)) { 547 if (isupper(queue) && (strcmp(batch_name,dirent->d_name) > 0)) { 548 run_batch = 1; 549 strlcpy(batch_name, dirent->d_name, sizeof(batch_name)); 550 batch_uid = buf.st_uid; 551 batch_gid = buf.st_gid; 552 } 553 554 /* The file is executable and old enough 555 */ 556 if (islower(queue)) 557 run_file(dirent->d_name, buf.st_uid, buf.st_gid); 558 } 559 /* Delete older files 560 */ 561 if ((run_time < now) && !(S_IXUSR & buf.st_mode) && (S_IRUSR & buf.st_mode)) 562 unlink(dirent->d_name); 563 } 564 /* run the single batch file, if any 565 */ 566 if (run_batch && (gloadavg() < load_avg)) 567 run_file(batch_name, batch_uid, batch_gid); 568 569 if (flock(dirfd(spool), LOCK_UN) == -1) 570 perr("cannot unlock %s", ATJOB_DIR); 571 572 if (closedir(spool) == -1) 573 perr("cannot closedir %s", ATJOB_DIR); 574 575 closelog(); 576 exit(EXIT_SUCCESS); 577 } 578 579 static void 580 usage(void) 581 { 582 if (debug) 583 fprintf(stderr, "usage: atrun [-l load_avg] [-d]\n"); 584 else 585 syslog(LOG_ERR, "usage: atrun [-l load_avg] [-d]"); 586 587 exit(EXIT_FAILURE); 588 } 589