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