1 /* $NetBSD: atrun.c,v 1.19 2008/04/05 20:17:37 christos Exp $ */ 2 3 /* 4 * atrun.c - run jobs queued by at; run with root privileges. 5 * Copyright (C) 1993, 1994 Thomas Koenig 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. The name of the author(s) may not be used to endorse or promote 13 * products derived from this software without specific prior written 14 * permission. 15 * 16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR(S) ``AS IS'' AND ANY EXPRESS OR 17 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 18 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 19 * IN NO EVENT SHALL THE AUTHOR(S) BE LIABLE FOR ANY DIRECT, INDIRECT, 20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 21 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 22 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 23 * THEORY OF LIABILITY, WETHER IN CONTRACT, STRICT LIABILITY, OR TORT 24 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 25 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 26 */ 27 28 /* System Headers */ 29 #include <sys/cdefs.h> 30 #include <sys/types.h> 31 #include <sys/wait.h> 32 33 #include <ctype.h> 34 #include <errno.h> 35 #include <dirent.h> 36 #include <fcntl.h> 37 #include <stdio.h> 38 #include <stdlib.h> 39 #include <string.h> 40 #include <limits.h> 41 #include <time.h> 42 #include <unistd.h> 43 #include <syslog.h> 44 #include <pwd.h> 45 #include <grp.h> 46 #include <err.h> 47 #include <paths.h> 48 #include <stdarg.h> 49 50 /* Local headers */ 51 52 #define MAIN 53 #include "privs.h" 54 #include "pathnames.h" 55 #include "atrun.h" 56 57 /* File scope variables */ 58 59 #if 0 60 static char rcsid[] = "$OpenBSD: atrun.c,v 1.7 1997/09/08 22:12:10 millert Exp $"; 61 #else 62 __RCSID("$NetBSD: atrun.c,v 1.19 2008/04/05 20:17:37 christos Exp $"); 63 #endif 64 65 static int debug = 0; 66 67 /* Local functions */ 68 static void perr(const char *, ...) __dead; 69 static void perrx(const char *, ...) __dead; 70 static int write_string(int, const char *); 71 static void run_file(const char *, uid_t, gid_t); 72 static void become_user(struct passwd *, uid_t); 73 74 static const char nobody[] = "nobody"; 75 76 static void 77 perr(const char *fmt, ...) 78 { 79 char buf[2048]; 80 va_list ap; 81 82 va_start(ap, fmt); 83 (void)vsnprintf(buf, sizeof(buf), fmt, ap); 84 va_end(ap); 85 86 if (debug) 87 warn("%s", buf); 88 else 89 syslog(LOG_ERR, "%s: %m", buf); 90 91 exit(EXIT_FAILURE); 92 } 93 94 static void 95 perrx(const char *fmt, ...) 96 { 97 va_list ap; 98 99 va_start(ap, fmt); 100 101 if (debug) 102 vwarnx(fmt, ap); 103 else 104 vsyslog(LOG_ERR, fmt, ap); 105 106 va_end(ap); 107 108 exit(EXIT_FAILURE); 109 } 110 111 static int 112 write_string(int fd, const char *a) 113 { 114 return write(fd, a, strlen(a)); 115 } 116 117 static void 118 become_user(struct passwd *pentry, uid_t uid) 119 { 120 if (initgroups(pentry->pw_name, pentry->pw_gid) == -1) 121 perr("Cannot init group list for `%s'", pentry->pw_name); 122 123 if (setegid(pentry->pw_gid) == -1 || setgid(pentry->pw_gid) == -1) 124 perr("Cannot change primary group to %lu", 125 (unsigned long)pentry->pw_gid); 126 127 if (setsid() == -1) 128 perr("Cannot create a session"); 129 130 if (setlogin(pentry->pw_name) == -1) 131 perr("Cannot set login name to `%s'", pentry->pw_name); 132 133 if (setuid(uid) == -1 || seteuid(uid) == -1) 134 perr("Cannot set user id to %lu", (unsigned long)uid); 135 136 if (chdir(pentry->pw_dir) == -1) 137 (void)chdir("/"); 138 } 139 140 static void 141 run_file(const char *filename, uid_t uid, gid_t gid) 142 { 143 /* 144 * Run a file by by spawning off a process which redirects I/O, 145 * spawns a subshell, then waits for it to complete and spawns another 146 * process to send mail to the user. 147 */ 148 pid_t pid; 149 int fd_out, fd_in; 150 int queue; 151 char mailbuf[LOGIN_NAME_MAX], fmt[49]; 152 char *mailname = NULL; 153 FILE *stream; 154 int send_mail = 0; 155 struct stat buf, lbuf; 156 off_t size; 157 struct passwd *pentry; 158 int fflags; 159 uid_t nuid; 160 gid_t ngid; 161 int serrno; 162 163 PRIV_START; 164 165 if (chmod(filename, S_IRUSR) == -1) 166 perr("Cannot change file permissions to `%s'", filename); 167 168 PRIV_END; 169 170 pid = fork(); 171 if (pid == -1) 172 perr("Cannot fork"); 173 else if (pid != 0) 174 return; 175 176 /* 177 * Let's see who we mail to. Hopefully, we can read it from the 178 * command file; if not, send it to the owner, or, failing that, to 179 * root. 180 */ 181 182 pentry = getpwuid(uid); 183 if (pentry == NULL) 184 perrx("Userid %lu not found - aborting job `%s'", 185 (unsigned long)uid, filename); 186 187 PRIV_START; 188 189 stream = fopen(filename, "r"); 190 serrno = errno; 191 192 PRIV_END; 193 194 if (stream == NULL) { 195 errno = serrno; 196 perr("Cannot open input file"); 197 } 198 199 if (pentry->pw_expire && time(NULL) >= pentry->pw_expire) 200 perrx("Userid %lu has expired - aborting job `%s'", 201 (unsigned long)uid, filename); 202 203 if ((fd_in = dup(fileno(stream))) == -1) 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 PRIV_START; 210 211 if (lstat(filename, &lbuf) == -1) 212 perr("Error in lstat of `%s'", filename); 213 214 PRIV_END; 215 216 if (S_ISLNK(lbuf.st_mode)) 217 perrx("Symbolic link encountered in job `%s' - aborting", 218 filename); 219 220 if ((lbuf.st_dev != buf.st_dev) || (lbuf.st_ino != buf.st_ino) || 221 (lbuf.st_uid != buf.st_uid) || (lbuf.st_gid != buf.st_gid) || 222 (lbuf.st_size!=buf.st_size)) 223 perrx("Somebody changed files from under us for job `%s' " 224 "- aborting", filename); 225 226 if (buf.st_nlink > 1) 227 perrx("Somebody is trying to run a linked script for job `%s'", 228 filename); 229 230 if ((fflags = fcntl(fd_in, F_GETFD)) < 0) 231 perr("Error in fcntl"); 232 233 (void)fcntl(fd_in, F_SETFD, fflags & ~FD_CLOEXEC); 234 235 (void)snprintf(fmt, sizeof(fmt), 236 "#!/bin/sh\n# atrun uid=%%u gid=%%u\n# mail %%%ds %%d", 237 LOGIN_NAME_MAX); 238 239 if (fscanf(stream, fmt, &nuid, &ngid, mailbuf, &send_mail) != 4) 240 perrx("File `%s' is in wrong format - aborting", filename); 241 242 if (mailbuf[0] == '-') 243 perrx("Illegal mail name `%s' in `%s'", mailbuf, filename); 244 245 mailname = mailbuf; 246 if (nuid != uid) 247 perrx("Job `%s' - userid %lu does not match file uid %lu", 248 filename, (unsigned long)nuid, (unsigned long)uid); 249 250 if (ngid != gid) 251 perrx("Job `%s' - groupid %lu does not match file gid %lu", 252 filename, (unsigned long)ngid, (unsigned long)gid); 253 254 (void)fclose(stream); 255 256 PRIV_START; 257 258 if (chdir(_PATH_ATSPOOL) == -1) 259 perr("Cannot chdir to `%s'", _PATH_ATSPOOL); 260 261 /* 262 * Create a file to hold the output of the job we are about to 263 * run. Write the mail header. 264 */ 265 266 if ((fd_out = open(filename, 267 O_WRONLY | O_CREAT | O_EXCL, S_IWUSR | S_IRUSR)) == -1) 268 perr("Cannot create output file `%s'", filename); 269 270 PRIV_END; 271 272 write_string(fd_out, "To: "); 273 write_string(fd_out, mailname); 274 write_string(fd_out, "\nSubject: Output from your job "); 275 write_string(fd_out, filename); 276 write_string(fd_out, "\n\n"); 277 if (fstat(fd_out, &buf) == -1) 278 perr("Error in fstat of output file descriptor"); 279 size = buf.st_size; 280 281 (void)close(STDIN_FILENO); 282 (void)close(STDOUT_FILENO); 283 (void)close(STDERR_FILENO); 284 285 pid = fork(); 286 if (pid < 0) 287 perr("Error in fork"); 288 else if (pid == 0) { 289 char *nul = NULL; 290 char **nenvp = &nul; 291 292 /* 293 * Set up things for the child; we want standard input from 294 * the input file, and standard output and error sent to 295 * our output file. 296 */ 297 if (lseek(fd_in, (off_t) 0, SEEK_SET) == (off_t)-1) 298 perr("Error in lseek"); 299 300 if (dup(fd_in) != STDIN_FILENO) 301 perr("Error in I/O redirection"); 302 303 if (dup(fd_out) != STDOUT_FILENO) 304 perr("Error in I/O redirection"); 305 306 if (dup(fd_out) != STDERR_FILENO) 307 perr("Error in I/O redirection"); 308 309 (void)close(fd_in); 310 (void)close(fd_out); 311 312 PRIV_START; 313 314 if (chdir(_PATH_ATJOBS) == -1) 315 perr("Cannot chdir to `%s'", _PATH_ATJOBS); 316 317 queue = *filename; 318 319 if (queue > 'b') 320 nice(queue - 'b'); 321 322 become_user(pentry, uid); 323 324 (void)execle("/bin/sh", "sh", (char *)NULL, nenvp); 325 perr("Exec failed for /bin/sh"); 326 } 327 /* We're the parent. Let's wait. */ 328 (void)close(fd_in); 329 (void)close(fd_out); 330 (void)waitpid(pid, (int *)NULL, 0); 331 332 /* 333 * Send mail. Unlink the output file first, so it is deleted 334 * after the run. 335 */ 336 PRIV_START; 337 338 if (stat(filename, &buf) == -1) 339 perr("Error in stat of output file `%s'", filename); 340 if (open(filename, O_RDONLY) != STDIN_FILENO) 341 perr("Open of jobfile `%s' failed", filename); 342 343 (void)unlink(filename); 344 345 PRIV_END; 346 347 if ((buf.st_size != size) || send_mail) { 348 /* Fork off a child for sending mail */ 349 350 PRIV_START; 351 352 become_user(pentry, uid); 353 354 execl(_PATH_SENDMAIL, "sendmail", "-F", "Atrun Service", 355 "-odi", "-oem", "-t", (char *) NULL); 356 perr("Exec failed for mail command `%s'", _PATH_SENDMAIL); 357 358 PRIV_END; 359 } 360 exit(EXIT_SUCCESS); 361 } 362 363 /* Global functions */ 364 365 int 366 main(int argc, char *argv[]) 367 { 368 /* 369 * Browse through _PATH_ATJOBS, checking all the jobfiles wether 370 * they should be executed and or deleted. The queue is coded into 371 * the first byte of the job filename, the date (in minutes since 372 * Eon) as a hex number in the following eight bytes, followed by 373 * a dot and a serial number. A file which has not been executed 374 * yet is denoted by its execute - bit set. For those files which 375 * are to be executed, run_file() is called, which forks off a 376 * child which takes care of I/O redirection, forks off another 377 * child for execution and yet another one, optionally, for sending 378 * mail. Files which already have run are removed during the 379 * next invocation. 380 */ 381 DIR *spool; 382 struct dirent *dirent; 383 struct stat buf; 384 unsigned long ctm; 385 int jobno; 386 char queue; 387 time_t now, run_time; 388 char batch_name[] = "Z2345678901234"; 389 uid_t batch_uid; 390 gid_t batch_gid; 391 int c; 392 int run_batch; 393 double la, load_avg = ATRUN_MAXLOAD; 394 struct group *grp; 395 struct passwd *pwd; 396 397 openlog("atrun", LOG_PID, LOG_CRON); 398 399 if ((grp = getgrnam(nobody)) == NULL) 400 perrx("Cannot get gid for `%s'", nobody); 401 402 if ((pwd = getpwnam(nobody)) == NULL) 403 perrx("Cannot get uid for `%s'", nobody); 404 405 /* 406 * We don't need root privileges all the time; running under uid 407 * and gid nobody is fine except for privileged operations. 408 */ 409 RELINQUISH_PRIVS_ROOT(pwd->pw_uid, grp->gr_gid); 410 411 opterr = 0; 412 errno = 0; 413 while ((c = getopt(argc, argv, "dl:")) != -1) { 414 switch (c) { 415 case 'l': 416 if (sscanf(optarg, "%lf", &load_avg) != 1) 417 perrx("Bad argument to option -l: ", optarg); 418 if (load_avg <= 0) 419 load_avg = ATRUN_MAXLOAD; 420 break; 421 422 case 'd': 423 debug++; 424 break; 425 426 case '?': 427 perrx("Usage: %s [-l <loadav>] [-d]", getprogname()); 428 /*NOTREACHED*/ 429 430 default: 431 perrx("Invalid option: %c", c); 432 /*NOTREACHED*/ 433 } 434 } 435 436 PRIV_START; 437 438 if (chdir(_PATH_ATJOBS) == -1) 439 perr("Cannot change directory to `%s'", _PATH_ATJOBS); 440 441 /* 442 * Main loop. Open spool directory for reading and look over all 443 * the files in there. If the filename indicates that the job 444 * should be run and the x bit is set, fork off a child which sets 445 * its user and group id to that of the files and exec a /bin/sh 446 * which executes the shell script. Unlink older files if they 447 * should no longer be run. For deletion, their r bit has to be 448 * turned on. 449 * 450 * Also, pick the oldest batch job to run, at most one per 451 * invocation of atrun. 452 */ 453 if ((spool = opendir(".")) == NULL) 454 perr("Cannot open `%s'", _PATH_ATJOBS); 455 456 PRIV_END; 457 458 now = time(NULL); 459 run_batch = 0; 460 batch_uid = (uid_t) -1; 461 batch_gid = (gid_t) -1; 462 463 while ((dirent = readdir(spool)) != NULL) { 464 PRIV_START; 465 466 if (stat(dirent->d_name, &buf) == -1) 467 perr("Cannot stat `%s' in `%s'", dirent->d_name, 468 _PATH_ATJOBS); 469 470 PRIV_END; 471 472 /* We don't want directories */ 473 if (!S_ISREG(buf.st_mode)) 474 continue; 475 476 if (sscanf(dirent->d_name, "%c%5x%8lx", &queue, &jobno, 477 &ctm) != 3) 478 continue; 479 480 run_time = (time_t) ctm * 60; 481 482 if ((S_IXUSR & buf.st_mode) && (run_time <= now)) { 483 if (isupper((unsigned char)queue) && 484 (strcmp(batch_name, dirent->d_name) > 0)) { 485 run_batch = 1; 486 (void)strlcpy(batch_name, dirent->d_name, 487 sizeof(batch_name)); 488 batch_uid = buf.st_uid; 489 batch_gid = buf.st_gid; 490 } 491 492 /* The file is executable and old enough */ 493 if (islower((unsigned char)queue)) 494 run_file(dirent->d_name, buf.st_uid, 495 buf.st_gid); 496 } 497 498 /* Delete older files */ 499 if ((run_time < now) && !(S_IXUSR & buf.st_mode) && 500 (S_IRUSR & buf.st_mode)) { 501 PRIV_START; 502 503 (void)unlink(dirent->d_name); 504 505 PRIV_END; 506 } 507 } 508 509 /* Run the single batch file, if any */ 510 if (run_batch && ((getloadavg(&la, 1) == 1) && la < load_avg)) 511 run_file(batch_name, batch_uid, batch_gid); 512 513 closelog(); 514 return EXIT_SUCCESS; 515 } 516