1 /* $NetBSD: atrun.c,v 1.23 2017/01/10 20:29:48 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/stat.h> 32 #include <sys/wait.h> 33 34 #include <ctype.h> 35 #include <errno.h> 36 #include <dirent.h> 37 #include <fcntl.h> 38 #include <stdio.h> 39 #include <stdlib.h> 40 #include <string.h> 41 #include <limits.h> 42 #include <time.h> 43 #include <unistd.h> 44 #include <syslog.h> 45 #include <pwd.h> 46 #include <grp.h> 47 #include <err.h> 48 #include <paths.h> 49 #include <stdarg.h> 50 51 /* Local headers */ 52 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 1.23 2017/01/10 20:29:48 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 __dead void 112 privs_fail(const char *msg) 113 { 114 perr("%s", msg); 115 } 116 117 static int 118 write_string(int fd, const char *a) 119 { 120 return write(fd, a, strlen(a)); 121 } 122 123 static void 124 become_user(struct passwd *pentry, uid_t uid) 125 { 126 if (initgroups(pentry->pw_name, pentry->pw_gid) == -1) 127 perr("Cannot init group list for `%s'", pentry->pw_name); 128 129 if (setegid(pentry->pw_gid) == -1 || setgid(pentry->pw_gid) == -1) 130 perr("Cannot change primary group to %lu", 131 (unsigned long)pentry->pw_gid); 132 133 if (setsid() == -1) 134 perr("Cannot create a session"); 135 136 if (setlogin(pentry->pw_name) == -1) 137 perr("Cannot set login name to `%s'", pentry->pw_name); 138 139 if (setuid(uid) == -1 || seteuid(uid) == -1) 140 perr("Cannot set user id to %lu", (unsigned long)uid); 141 142 if (chdir(pentry->pw_dir) == -1) 143 (void)chdir("/"); 144 } 145 146 static void 147 run_file(const char *filename, uid_t uid, gid_t gid) 148 { 149 /* 150 * Run a file by by spawning off a process which redirects I/O, 151 * spawns a subshell, then waits for it to complete and spawns another 152 * process to send mail to the user. 153 */ 154 pid_t pid; 155 int fd_out, fd_in; 156 int queue; 157 char mailbuf[LOGIN_NAME_MAX], fmt[49]; 158 char *mailname = NULL; 159 FILE *stream; 160 int send_mail = 0; 161 struct stat buf, lbuf; 162 off_t size; 163 struct passwd *pentry; 164 int fflags; 165 uid_t nuid; 166 gid_t ngid; 167 int serrno; 168 169 privs_enter(); 170 171 if (chmod(filename, S_IRUSR) == -1) 172 perr("Cannot change file permissions to `%s'", filename); 173 174 privs_exit(); 175 176 pid = fork(); 177 if (pid == -1) 178 perr("Cannot fork"); 179 else if (pid != 0) 180 return; 181 182 /* 183 * Let's see who we mail to. Hopefully, we can read it from the 184 * command file; if not, send it to the owner, or, failing that, to 185 * root. 186 */ 187 188 pentry = getpwuid(uid); 189 if (pentry == NULL) 190 perrx("Userid %lu not found - aborting job `%s'", 191 (unsigned long)uid, filename); 192 193 privs_enter(); 194 195 stream = fopen(filename, "r"); 196 serrno = errno; 197 198 privs_exit(); 199 200 if (stream == NULL) { 201 errno = serrno; 202 perr("Cannot open input file"); 203 } 204 205 if (pentry->pw_expire && time(NULL) >= pentry->pw_expire) 206 perrx("Userid %lu has expired - aborting job `%s'", 207 (unsigned long)uid, filename); 208 209 if ((fd_in = dup(fileno(stream))) == -1) 210 perr("Error duplicating input file descriptor"); 211 212 if (fstat(fd_in, &buf) == -1) 213 perr("Error in fstat of input file descriptor"); 214 215 privs_enter(); 216 217 if (lstat(filename, &lbuf) == -1) 218 perr("Error in lstat of `%s'", filename); 219 220 privs_exit(); 221 222 if (S_ISLNK(lbuf.st_mode)) 223 perrx("Symbolic link encountered in job `%s' - aborting", 224 filename); 225 226 if ((lbuf.st_dev != buf.st_dev) || (lbuf.st_ino != buf.st_ino) || 227 (lbuf.st_uid != buf.st_uid) || (lbuf.st_gid != buf.st_gid) || 228 (lbuf.st_size!=buf.st_size)) 229 perrx("Somebody changed files from under us for job `%s' " 230 "- aborting", filename); 231 232 if (buf.st_nlink > 1) 233 perrx("Somebody is trying to run a linked script for job `%s'", 234 filename); 235 236 if ((fflags = fcntl(fd_in, F_GETFD)) < 0) 237 perr("Error in fcntl"); 238 239 (void)fcntl(fd_in, F_SETFD, fflags & ~FD_CLOEXEC); 240 241 (void)snprintf(fmt, sizeof(fmt), 242 "#!/bin/sh\n# atrun uid=%%u gid=%%u\n# mail %%%ds %%d", 243 LOGIN_NAME_MAX); 244 245 if (fscanf(stream, fmt, &nuid, &ngid, mailbuf, &send_mail) != 4) 246 perrx("File `%s' is in wrong format - aborting", filename); 247 248 if (mailbuf[0] == '-') 249 perrx("Illegal mail name `%s' in `%s'", mailbuf, filename); 250 251 mailname = mailbuf; 252 if (nuid != uid) 253 perrx("Job `%s' - userid %lu does not match file uid %lu", 254 filename, (unsigned long)nuid, (unsigned long)uid); 255 256 if (ngid != gid) 257 perrx("Job `%s' - groupid %lu does not match file gid %lu", 258 filename, (unsigned long)ngid, (unsigned long)gid); 259 260 (void)fclose(stream); 261 262 privs_enter(); 263 264 if (chdir(_PATH_ATSPOOL) == -1) 265 perr("Cannot chdir to `%s'", _PATH_ATSPOOL); 266 267 /* 268 * Create a file to hold the output of the job we are about to 269 * run. Write the mail header. 270 */ 271 272 if ((fd_out = open(filename, 273 O_WRONLY | O_CREAT | O_EXCL, S_IWUSR | S_IRUSR)) == -1) 274 perr("Cannot create output file `%s'", filename); 275 276 privs_exit(); 277 278 write_string(fd_out, "To: "); 279 write_string(fd_out, mailname); 280 write_string(fd_out, "\nSubject: Output from your job "); 281 write_string(fd_out, filename); 282 write_string(fd_out, "\n\n"); 283 if (fstat(fd_out, &buf) == -1) 284 perr("Error in fstat of output file descriptor"); 285 size = buf.st_size; 286 287 (void)close(STDIN_FILENO); 288 (void)close(STDOUT_FILENO); 289 (void)close(STDERR_FILENO); 290 291 pid = fork(); 292 if (pid < 0) 293 perr("Error in fork"); 294 else if (pid == 0) { 295 char *nul = NULL; 296 char **nenvp = &nul; 297 298 /* 299 * Set up things for the child; we want standard input from 300 * the input file, and standard output and error sent to 301 * our output file. 302 */ 303 if (lseek(fd_in, (off_t) 0, SEEK_SET) == (off_t)-1) 304 perr("Error in lseek"); 305 306 if (dup(fd_in) != STDIN_FILENO) 307 perr("Error in I/O redirection"); 308 309 if (dup(fd_out) != STDOUT_FILENO) 310 perr("Error in I/O redirection"); 311 312 if (dup(fd_out) != STDERR_FILENO) 313 perr("Error in I/O redirection"); 314 315 (void)close(fd_in); 316 (void)close(fd_out); 317 318 privs_enter(); 319 320 if (chdir(_PATH_ATJOBS) == -1) 321 perr("Cannot chdir to `%s'", _PATH_ATJOBS); 322 323 queue = *filename; 324 325 if (queue > 'b') 326 nice(queue - 'b'); 327 328 become_user(pentry, uid); 329 330 (void)execle("/bin/sh", "sh", (char *)NULL, nenvp); 331 perr("Exec failed for /bin/sh"); 332 } 333 /* We're the parent. Let's wait. */ 334 (void)close(fd_in); 335 (void)close(fd_out); 336 (void)waitpid(pid, NULL, 0); 337 338 /* 339 * Send mail. Unlink the output file first, so it is deleted 340 * after the run. 341 */ 342 privs_enter(); 343 344 if (stat(filename, &buf) == -1) 345 perr("Error in stat of output file `%s'", filename); 346 if (open(filename, O_RDONLY) != STDIN_FILENO) 347 perr("Open of jobfile `%s' failed", filename); 348 349 (void)unlink(filename); 350 351 privs_exit(); 352 353 if ((buf.st_size != size) || send_mail) { 354 /* Fork off a child for sending mail */ 355 356 privs_enter(); 357 358 become_user(pentry, uid); 359 360 execl(_PATH_SENDMAIL, "sendmail", "-F", "Atrun Service", 361 "-odi", "-oem", "-t", (char *) NULL); 362 perr("Exec failed for mail command `%s'", _PATH_SENDMAIL); 363 364 privs_exit(); 365 } 366 exit(EXIT_SUCCESS); 367 } 368 369 /* Global functions */ 370 371 int 372 main(int argc, char *argv[]) 373 { 374 /* 375 * Browse through _PATH_ATJOBS, checking all the jobfiles whether 376 * they should be executed and or deleted. The queue is coded into 377 * the first byte of the job filename, the date (in minutes since 378 * Eon) as a hex number in the following eight bytes, followed by 379 * a dot and a serial number. A file which has not been executed 380 * yet is denoted by its execute - bit set. For those files which 381 * are to be executed, run_file() is called, which forks off a 382 * child which takes care of I/O redirection, forks off another 383 * child for execution and yet another one, optionally, for sending 384 * mail. Files which already have run are removed during the 385 * next invocation. 386 */ 387 DIR *spool; 388 struct dirent *dirent; 389 struct stat buf; 390 unsigned long ctm; 391 int jobno; 392 char queue; 393 time_t now, run_time; 394 char batch_name[] = "Z2345678901234"; 395 uid_t batch_uid; 396 gid_t batch_gid; 397 int c; 398 int run_batch; 399 double la, load_avg = ATRUN_MAXLOAD; 400 struct group *grp; 401 struct passwd *pwd; 402 403 openlog("atrun", LOG_PID, LOG_CRON); 404 405 if ((grp = getgrnam(nobody)) == NULL) 406 perrx("Cannot get gid for `%s'", nobody); 407 408 if ((pwd = getpwnam(nobody)) == NULL) 409 perrx("Cannot get uid for `%s'", nobody); 410 411 /* 412 * We don't need root privileges all the time; running under uid 413 * and gid nobody is fine except for privileged operations. 414 */ 415 privs_relinquish_root(pwd->pw_uid, grp->gr_gid); 416 417 opterr = 0; 418 errno = 0; 419 while ((c = getopt(argc, argv, "dl:")) != -1) { 420 switch (c) { 421 case 'l': 422 if (sscanf(optarg, "%lf", &load_avg) != 1) 423 perrx("Bad argument to option -l: ", optarg); 424 if (load_avg <= 0) 425 load_avg = ATRUN_MAXLOAD; 426 break; 427 428 case 'd': 429 debug++; 430 break; 431 432 case '?': 433 perrx("Usage: %s [-l <loadav>] [-d]", getprogname()); 434 /*NOTREACHED*/ 435 436 default: 437 perrx("Invalid option: %c", c); 438 /*NOTREACHED*/ 439 } 440 } 441 442 privs_enter(); 443 444 if (chdir(_PATH_ATJOBS) == -1) 445 perr("Cannot change directory to `%s'", _PATH_ATJOBS); 446 447 /* 448 * Main loop. Open spool directory for reading and look over all 449 * the files in there. If the filename indicates that the job 450 * should be run and the x bit is set, fork off a child which sets 451 * its user and group id to that of the files and exec a /bin/sh 452 * which executes the shell script. Unlink older files if they 453 * should no longer be run. For deletion, their r bit has to be 454 * turned on. 455 * 456 * Also, pick the oldest batch job to run, at most one per 457 * invocation of atrun. 458 */ 459 if ((spool = opendir(".")) == NULL) 460 perr("Cannot open `%s'", _PATH_ATJOBS); 461 462 privs_exit(); 463 464 now = time(NULL); 465 run_batch = 0; 466 batch_uid = (uid_t) -1; 467 batch_gid = (gid_t) -1; 468 469 while ((dirent = readdir(spool)) != NULL) { 470 privs_enter(); 471 472 if (stat(dirent->d_name, &buf) == -1) 473 perr("Cannot stat `%s' in `%s'", dirent->d_name, 474 _PATH_ATJOBS); 475 476 privs_exit(); 477 478 /* We don't want directories */ 479 if (!S_ISREG(buf.st_mode)) 480 continue; 481 482 if (sscanf(dirent->d_name, "%c%5x%8lx", &queue, &jobno, 483 &ctm) != 3) 484 continue; 485 486 run_time = (time_t) ctm * 60; 487 488 if ((S_IXUSR & buf.st_mode) && (run_time <= now)) { 489 if (isupper((unsigned char)queue) && 490 (strcmp(batch_name, dirent->d_name) > 0)) { 491 run_batch = 1; 492 (void)strlcpy(batch_name, dirent->d_name, 493 sizeof(batch_name)); 494 batch_uid = buf.st_uid; 495 batch_gid = buf.st_gid; 496 } 497 498 /* The file is executable and old enough */ 499 if (islower((unsigned char)queue)) 500 run_file(dirent->d_name, buf.st_uid, 501 buf.st_gid); 502 } 503 504 /* Delete older files */ 505 if ((run_time < now) && !(S_IXUSR & buf.st_mode) && 506 (S_IRUSR & buf.st_mode)) { 507 privs_enter(); 508 509 (void)unlink(dirent->d_name); 510 511 privs_exit(); 512 } 513 } 514 515 /* Run the single batch file, if any */ 516 if (run_batch && ((getloadavg(&la, 1) == 1) && la < load_avg)) 517 run_file(batch_name, batch_uid, batch_gid); 518 519 closelog(); 520 return EXIT_SUCCESS; 521 } 522
Indexes created Sat Sep 20 22:09:52 GMT 2025