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