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 * $FreeBSD: src/libexec/atrun/atrun.c,v 1.26 2007/06/15 12:02:16 yar Exp $ 26 */ 27 28 /* System Headers */ 29 30 #include <sys/fcntl.h> 31 #include <sys/types.h> 32 #include <sys/stat.h> 33 #include <sys/wait.h> 34 #include <sys/param.h> 35 #include <ctype.h> 36 #include <dirent.h> 37 #include <err.h> 38 #include <grp.h> 39 #include <pwd.h> 40 #include <signal.h> 41 #include <stdarg.h> 42 #include <stddef.h> 43 #include <stdio.h> 44 #include <stdlib.h> 45 #include <string.h> 46 #include <syslog.h> 47 #include <time.h> 48 #include <unistd.h> 49 #include <paths.h> 50 #ifdef LOGIN_CAP 51 #include <login_cap.h> 52 #endif 53 #ifdef PAM 54 #include <security/pam_appl.h> 55 #include <security/openpam.h> 56 #endif 57 58 /* Local headers */ 59 60 #include "gloadavg.h" 61 #include "privs.h" 62 63 /* Macros */ 64 65 #ifndef ATJOB_DIR 66 #define ATJOB_DIR "/usr/spool/atjobs/" 67 #endif 68 69 #ifndef ATSPOOL_DIR 70 #define ATSPOOL_DIR "/usr/spool/atspool/" 71 #endif 72 73 #ifndef LOADAVG_MX 74 #define LOADAVG_MX 1.5 75 #endif 76 77 uid_t real_uid, effective_uid; 78 gid_t real_gid, effective_gid; 79 80 /* File scope variables */ 81 82 static const char * const atrun = "atrun"; /* service name for syslog etc. */ 83 static int debug = 0; 84 85 void perr(const char *fmt, ...) __dead2 __printflike(1, 2); 86 void perrx(const char *fmt, ...) __dead2 __printflike(1, 2); 87 static void usage(void) __dead2; 88 89 /* Local functions */ 90 static int 91 write_string(int fd, const char* a) 92 { 93 return write(fd, a, strlen(a)); 94 } 95 96 #undef DEBUG_FORK 97 #ifdef DEBUG_FORK 98 static pid_t 99 myfork(void) 100 { 101 pid_t res; 102 res = fork(); 103 if (res == 0) 104 kill(getpid(),SIGSTOP); 105 return res; 106 } 107 108 #define fork myfork 109 #endif 110 111 static void 112 run_file(const char *filename, uid_t uid, gid_t gid) 113 { 114 /* Run a file by spawning off a process which redirects I/O, 115 * spawns a subshell, then waits for it to complete and sends 116 * mail to the user. 117 */ 118 pid_t pid; 119 int fd_out, fd_in; 120 int queue; 121 char mailbuf[MAXLOGNAME], fmt[49]; 122 char *mailname = NULL; 123 FILE *stream; 124 int send_mail = 0; 125 struct stat buf, lbuf; 126 off_t size; 127 struct passwd *pentry; 128 int fflags; 129 uid_t nuid; 130 gid_t ngid; 131 #ifdef PAM 132 pam_handle_t *pamh = NULL; 133 int pam_err; 134 struct pam_conv pamc = { 135 .conv = openpam_nullconv, 136 .appdata_ptr = NULL 137 }; 138 #endif 139 140 PRIV_START 141 142 if (chmod(filename, S_IRUSR) != 0) 143 { 144 perr("cannot change file permissions"); 145 } 146 147 PRIV_END 148 149 pid = fork(); 150 if (pid == -1) 151 perr("cannot fork"); 152 153 else if (pid != 0) 154 return; 155 156 /* Let's see who we mail to. Hopefully, we can read it from 157 * the command file; if not, send it to the owner, or, failing that, 158 * to root. 159 */ 160 161 pentry = getpwuid(uid); 162 if (pentry == NULL) 163 perrx("Userid %lu not found - aborting job %s", 164 (unsigned long) uid, filename); 165 166 #ifdef PAM 167 PRIV_START 168 169 pam_err = pam_start(atrun, pentry->pw_name, &pamc, &pamh); 170 if (pam_err != PAM_SUCCESS) 171 perrx("cannot start PAM: %s", pam_strerror(pamh, pam_err)); 172 173 pam_err = pam_acct_mgmt(pamh, PAM_SILENT); 174 /* Expired password shouldn't prevent the job from running. */ 175 if (pam_err != PAM_SUCCESS && pam_err != PAM_NEW_AUTHTOK_REQD) 176 perrx("Account %s (userid %lu) unavailable for job %s: %s", 177 pentry->pw_name, (unsigned long)uid, 178 filename, pam_strerror(pamh, pam_err)); 179 180 pam_end(pamh, pam_err); 181 182 PRIV_END 183 #endif /* PAM */ 184 185 PRIV_START 186 187 stream=fopen(filename, "r"); 188 189 PRIV_END 190 191 if (stream == NULL) 192 perr("cannot open input file"); 193 194 if ((fd_in = dup(fileno(stream))) <0) 195 perr("error duplicating input file descriptor"); 196 197 if (fstat(fd_in, &buf) == -1) 198 perr("error in fstat of input file descriptor"); 199 200 if (lstat(filename, &lbuf) == -1) 201 perr("error in fstat of input file"); 202 203 if (S_ISLNK(lbuf.st_mode)) 204 perrx("Symbolic link encountered in job %s - aborting", filename); 205 206 if ((lbuf.st_dev != buf.st_dev) || (lbuf.st_ino != buf.st_ino) || 207 (lbuf.st_uid != buf.st_uid) || (lbuf.st_gid != buf.st_gid) || 208 (lbuf.st_size!=buf.st_size)) 209 perrx("Somebody changed files from under us for job %s - aborting", 210 filename); 211 212 if (buf.st_nlink > 1) 213 perrx("Somebody is trying to run a linked script for job %s", filename); 214 215 if ((fflags = fcntl(fd_in, F_GETFD)) <0) 216 perr("error in fcntl"); 217 218 fcntl(fd_in, F_SETFD, fflags & ~FD_CLOEXEC); 219 220 snprintf(fmt, sizeof(fmt), 221 "#!/bin/sh\n# atrun uid=%%u gid=%%u\n# mail %%%ds %%d", 222 MAXLOGNAME - 1); 223 224 if (fscanf(stream, fmt, &nuid, &ngid, mailbuf, &send_mail) != 4) 225 perrx("File %s is in wrong format - aborting", filename); 226 227 if (mailbuf[0] == '-') 228 perrx("Illegal mail name %s in %s", mailbuf, filename); 229 230 mailname = mailbuf; 231 232 if (nuid != uid) 233 perrx("Job %s - userid %u does not match file uid %u", 234 filename, nuid, uid); 235 236 if (ngid != gid) 237 perrx("Job %s - groupid %u does not match file gid %u", 238 filename, ngid, gid); 239 240 fclose(stream); 241 242 if (chdir(ATSPOOL_DIR) < 0) 243 perr("cannot chdir to %s", ATSPOOL_DIR); 244 245 /* Create a file to hold the output of the job we are about to run. 246 * Write the mail header. 247 */ 248 if((fd_out=open(filename, 249 O_WRONLY | O_CREAT | O_EXCL, S_IWUSR | S_IRUSR)) < 0) 250 perr("cannot create output file"); 251 252 write_string(fd_out, "Subject: Output from your job "); 253 write_string(fd_out, filename); 254 write_string(fd_out, "\n\n"); 255 fstat(fd_out, &buf); 256 size = buf.st_size; 257 258 close(STDIN_FILENO); 259 close(STDOUT_FILENO); 260 close(STDERR_FILENO); 261 262 pid = fork(); 263 if (pid < 0) 264 perr("error in fork"); 265 266 else if (pid == 0) 267 { 268 char *nul = NULL; 269 char **nenvp = &nul; 270 271 /* Set up things for the child; we want standard input from the input file, 272 * and standard output and error sent to our output file. 273 */ 274 275 if (lseek(fd_in, (off_t) 0, SEEK_SET) < 0) 276 perr("error in lseek"); 277 278 if (dup(fd_in) != STDIN_FILENO) 279 perr("error in I/O redirection"); 280 281 if (dup(fd_out) != STDOUT_FILENO) 282 perr("error in I/O redirection"); 283 284 if (dup(fd_out) != STDERR_FILENO) 285 perr("error in I/O redirection"); 286 287 close(fd_in); 288 close(fd_out); 289 if (chdir(ATJOB_DIR) < 0) 290 perr("cannot chdir to %s", ATJOB_DIR); 291 292 queue = *filename; 293 294 PRIV_START 295 296 nice(tolower(queue) - 'a'); 297 298 #ifdef LOGIN_CAP 299 /* 300 * For simplicity and safety, set all aspects of the user context 301 * except for a selected subset: Don't set priority, which was 302 * set based on the queue file name according to the tradition. 303 * Don't bother to set environment, including path vars, either 304 * because it will be discarded anyway. Although the job file 305 * should set umask, preset it here just in case. 306 */ 307 if (setusercontext(NULL, pentry, uid, LOGIN_SETALL & 308 ~(LOGIN_SETPRIORITY | LOGIN_SETPATH | LOGIN_SETENV)) != 0) 309 exit(EXIT_FAILURE); /* setusercontext() logged the error */ 310 #else /* LOGIN_CAP */ 311 if (initgroups(pentry->pw_name,pentry->pw_gid)) 312 perr("cannot init group access list"); 313 314 if (setgid(gid) < 0 || setegid(pentry->pw_gid) < 0) 315 perr("cannot change group"); 316 317 if (setlogin(pentry->pw_name)) 318 perr("cannot set login name"); 319 320 if (setuid(uid) < 0 || seteuid(uid) < 0) 321 perr("cannot set user id"); 322 #endif /* LOGIN_CAP */ 323 324 if (chdir(pentry->pw_dir)) 325 chdir("/"); 326 327 if(execle("/bin/sh","sh",NULL, nenvp) != 0) 328 perr("exec failed for /bin/sh"); 329 330 PRIV_END 331 } 332 /* We're the parent. Let's wait. 333 */ 334 close(fd_in); 335 close(fd_out); 336 waitpid(pid, NULL, 0); 337 338 /* Send mail. Unlink the output file first, so it is deleted after 339 * the run. 340 */ 341 stat(filename, &buf); 342 if (open(filename, O_RDONLY) != STDIN_FILENO) 343 perr("open of jobfile failed"); 344 345 unlink(filename); 346 if ((buf.st_size != size) || send_mail) 347 { 348 PRIV_START 349 350 #ifdef LOGIN_CAP 351 /* 352 * This time set full context to run the mailer. 353 */ 354 if (setusercontext(NULL, pentry, uid, LOGIN_SETALL) != 0) 355 exit(EXIT_FAILURE); /* setusercontext() logged the error */ 356 #else /* LOGIN_CAP */ 357 if (initgroups(pentry->pw_name,pentry->pw_gid)) 358 perr("cannot init group access list"); 359 360 if (setgid(gid) < 0 || setegid(pentry->pw_gid) < 0) 361 perr("cannot change group"); 362 363 if (setlogin(pentry->pw_name)) 364 perr("cannot set login name"); 365 366 if (setuid(uid) < 0 || seteuid(uid) < 0) 367 perr("cannot set user id"); 368 #endif /* LOGIN_CAP */ 369 370 if (chdir(pentry->pw_dir)) 371 chdir("/"); 372 373 execl(_PATH_SENDMAIL, "sendmail", "-F", "Atrun Service", 374 "-odi", "-oem", 375 mailname, NULL); 376 perr("exec failed for mail command"); 377 378 PRIV_END 379 } 380 exit(EXIT_SUCCESS); 381 } 382 383 /* Global functions */ 384 385 /* Needed in gloadavg.c */ 386 void 387 perr(const char *fmt, ...) 388 { 389 const char * const fmtadd = ": %m"; 390 char nfmt[strlen(fmt) + strlen(fmtadd) + 1]; 391 va_list ap; 392 393 va_start(ap, fmt); 394 if (debug) 395 { 396 vwarn(fmt, ap); 397 } 398 else 399 { 400 snprintf(nfmt, sizeof(nfmt), "%s%s", fmt, fmtadd); 401 vsyslog(LOG_ERR, nfmt, ap); 402 } 403 va_end(ap); 404 405 exit(EXIT_FAILURE); 406 } 407 408 void 409 perrx(const char *fmt, ...) 410 { 411 va_list ap; 412 413 va_start(ap, fmt); 414 if (debug) 415 vwarnx(fmt, ap); 416 else 417 vsyslog(LOG_ERR, fmt, ap); 418 va_end(ap); 419 420 exit(EXIT_FAILURE); 421 } 422 423 int 424 main(int argc, char *argv[]) 425 { 426 /* Browse through ATJOB_DIR, checking all the jobfiles wether they should 427 * be executed and or deleted. The queue is coded into the first byte of 428 * the job filename, the date (in minutes since Eon) as a hex number in the 429 * following eight bytes, followed by a dot and a serial number. A file 430 * which has not been executed yet is denoted by its execute - bit set. 431 * For those files which are to be executed, run_file() is called, which forks 432 * off a child which takes care of I/O redirection, forks off another child 433 * for execution and yet another one, optionally, for sending mail. 434 * Files which already have run are removed during the next invocation. 435 */ 436 DIR *spool; 437 struct dirent *dirent; 438 struct stat buf; 439 unsigned long ctm; 440 unsigned long jobno; 441 char queue; 442 time_t now, run_time; 443 char batch_name[] = "Z2345678901234"; 444 uid_t batch_uid; 445 gid_t batch_gid; 446 int c; 447 int run_batch; 448 double load_avg = LOADAVG_MX; 449 450 /* We don't need root privileges all the time; running under uid and gid daemon 451 * is fine. 452 */ 453 454 RELINQUISH_PRIVS_ROOT(DAEMON_UID, DAEMON_GID) 455 456 openlog(atrun, LOG_PID, LOG_CRON); 457 458 opterr = 0; 459 while((c=getopt(argc, argv, "dl:"))!= -1) 460 { 461 switch (c) 462 { 463 case 'l': 464 if (sscanf(optarg, "%lf", &load_avg) != 1) 465 perr("garbled option -l"); 466 if (load_avg <= 0.) 467 load_avg = LOADAVG_MX; 468 break; 469 470 case 'd': 471 debug ++; 472 break; 473 474 case '?': 475 default: 476 usage(); 477 } 478 } 479 480 if (chdir(ATJOB_DIR) != 0) 481 perr("cannot change to %s", ATJOB_DIR); 482 483 /* Main loop. Open spool directory for reading and look over all the 484 * files in there. If the filename indicates that the job should be run 485 * and the x bit is set, fork off a child which sets its user and group 486 * id to that of the files and exec a /bin/sh which executes the shell 487 * script. Unlink older files if they should no longer be run. For 488 * deletion, their r bit has to be turned on. 489 * 490 * Also, pick the oldest batch job to run, at most one per invocation of 491 * atrun. 492 */ 493 if ((spool = opendir(".")) == NULL) 494 perr("cannot read %s", ATJOB_DIR); 495 496 now = time(NULL); 497 run_batch = 0; 498 batch_uid = (uid_t) -1; 499 batch_gid = (gid_t) -1; 500 501 while ((dirent = readdir(spool)) != NULL) { 502 if (stat(dirent->d_name,&buf) != 0) 503 perr("cannot stat in %s", ATJOB_DIR); 504 505 /* We don't want directories 506 */ 507 if (!S_ISREG(buf.st_mode)) 508 continue; 509 510 if (sscanf(dirent->d_name,"%c%5lx%8lx",&queue,&jobno,&ctm) != 3) 511 continue; 512 513 run_time = (time_t) ctm*60; 514 515 if ((S_IXUSR & buf.st_mode) && (run_time <=now)) { 516 if (isupper(queue) && (strcmp(batch_name,dirent->d_name) > 0)) { 517 run_batch = 1; 518 strlcpy(batch_name, dirent->d_name, sizeof(batch_name)); 519 batch_uid = buf.st_uid; 520 batch_gid = buf.st_gid; 521 } 522 523 /* The file is executable and old enough 524 */ 525 if (islower(queue)) 526 run_file(dirent->d_name, buf.st_uid, buf.st_gid); 527 } 528 /* Delete older files 529 */ 530 if ((run_time < now) && !(S_IXUSR & buf.st_mode) && (S_IRUSR & buf.st_mode)) 531 unlink(dirent->d_name); 532 } 533 /* run the single batch file, if any 534 */ 535 if (run_batch && (gloadavg() < load_avg)) 536 run_file(batch_name, batch_uid, batch_gid); 537 538 closelog(); 539 exit(EXIT_SUCCESS); 540 } 541 542 static void 543 usage(void) 544 { 545 if (debug) 546 fprintf(stderr, "usage: atrun [-l load_avg] [-d]\n"); 547 else 548 syslog(LOG_ERR, "usage: atrun [-l load_avg] [-d]"); 549 550 exit(EXIT_FAILURE); 551 } 552