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