atrun.c revision 1.16
1 /* $NetBSD: atrun.c,v 1.16 2005/10/31 16:15:42 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/types.h> 30 #include <sys/wait.h> 31 32 #include <ctype.h> 33 #include <errno.h> 34 #include <dirent.h> 35 #include <fcntl.h> 36 #include <stdio.h> 37 #include <stdlib.h> 38 #include <string.h> 39 #include <limits.h> 40 #include <time.h> 41 #include <unistd.h> 42 #include <syslog.h> 43 #include <pwd.h> 44 #include <grp.h> 45 #include <err.h> 46 #include <paths.h> 47 #include <stdarg.h> 48 49 /* Local headers */ 50 51 #define MAIN 52 #include "privs.h" 53 #include "pathnames.h" 54 #include "atrun.h" 55 56 /* File scope variables */ 57 58 #if 0 59 static char rcsid[] = "$OpenBSD: atrun.c,v 1.7 1997/09/08 22:12:10 millert Exp $"; 60 #else 61 __RCSID("$NetBSD: atrun.c,v 1.16 2005/10/31 16:15:42 christos Exp $"); 62 #endif 63 64 static int debug = 0; 65 66 /* Local functions */ 67 static void perr(const char *, ...) __attribute__((__noreturn__)); 68 static void perrx(const char *, ...) __attribute__((__noreturn__)); 69 static int write_string(int, const char *); 70 static void run_file(const char *, uid_t, gid_t); 71 static void become_user(struct passwd *, uid_t); 72 73 static const char nobody[] = "nobody"; 74 75 static void 76 perr(const char *fmt, ...) 77 { 78 char buf[2048]; 79 va_list ap; 80 81 va_start(ap, fmt); 82 (void)vsnprintf(buf, sizeof(buf), fmt, ap); 83 va_end(ap); 84 85 if (debug) 86 warn("%s", buf); 87 else 88 syslog(LOG_ERR, "%s: %m", buf); 89 90 exit(EXIT_FAILURE); 91 } 92 93 static void 94 perrx(const char *fmt, ...) 95 { 96 va_list ap; 97 98 va_start(ap, fmt); 99 100 if (debug) 101 vwarnx(fmt, ap); 102 else 103 vsyslog(LOG_ERR, fmt, ap); 104 105 va_end(ap); 106 107 exit(EXIT_FAILURE); 108 } 109 110 static int 111 write_string(int fd, const char *a) 112 { 113 return write(fd, a, strlen(a)); 114 } 115 116 static void 117 become_user(struct passwd *pentry, uid_t uid) 118 { 119 if (initgroups(pentry->pw_name, pentry->pw_gid) == -1) 120 perr("Cannot init group list for `%s'", pentry->pw_name); 121 122 if (setegid(pentry->pw_gid) == -1 || setgid(pentry->pw_gid) == -1) 123 perr("Cannot change primary group to %lu", 124 (unsigned long)pentry->pw_gid); 125 126 if (setsid() == -1) 127 perr("Cannot create a session"); 128 129 if (setlogin(pentry->pw_name) == -1) 130 perr("Cannot set login name to `%s'", pentry->pw_name); 131 132 if (setuid(uid) == -1 || seteuid(uid) == -1) 133 perr("Cannot set user id to %lu", (unsigned long)uid); 134 135 if (chdir(pentry->pw_dir) == -1) 136 (void)chdir("/"); 137 } 138 139 static void 140 run_file(const char *filename, uid_t uid, gid_t gid) 141 { 142 /* 143 * Run a file by by spawning off a process which redirects I/O, 144 * spawns a subshell, then waits for it to complete and spawns another 145 * process to send mail to the user. 146 */ 147 pid_t pid; 148 int fd_out, fd_in; 149 int queue; 150 char mailbuf[LOGIN_NAME_MAX], fmt[49]; 151 char *mailname = NULL; 152 FILE *stream; 153 int send_mail = 0; 154 struct stat buf, lbuf; 155 off_t size; 156 struct passwd *pentry; 157 int fflags; 158 uid_t nuid; 159 gid_t ngid; 160 int serrno; 161 162 PRIV_START 163 164 if (chmod(filename, S_IRUSR) == -1) 165 perr("Cannot change file permissions to `%s'", filename); 166 167 PRIV_END 168 169 pid = fork(); 170 if (pid == -1) 171 perr("Cannot fork"); 172 else if (pid != 0) 173 return; 174 175 /* 176 * Let's see who we mail to. Hopefully, we can read it from the 177 * command file; if not, send it to the owner, or, failing that, to 178 * root. 179 */ 180 181 pentry = getpwuid(uid); 182 if (pentry == NULL) 183 perrx("Userid %lu not found - aborting job `%s'", 184 (unsigned long)uid, filename); 185 186 PRIV_START 187 188 stream = fopen(filename, "r"); 189 serrno = errno; 190 191 PRIV_END 192 193 if (stream == NULL) { 194 errno = serrno; 195 perr("Cannot open input file"); 196 } 197 198 if (pentry->pw_expire && time(NULL) >= pentry->pw_expire) 199 perrx("Userid %lu has expired - aborting job `%s'", 200 (unsigned long)uid, filename); 201 202 if ((fd_in = dup(fileno(stream))) == -1) 203 perr("Error duplicating input file descriptor"); 204 205 if (fstat(fd_in, &buf) == -1) 206 perr("Error in fstat of input file descriptor"); 207 208 PRIV_START 209 210 if (lstat(filename, &lbuf) == -1) 211 perr("Error in lstat of `%s'", filename); 212 213 PRIV_END 214 215 if (S_ISLNK(lbuf.st_mode)) 216 perrx("Symbolic link encountered in job `%s' - aborting", 217 filename); 218 219 if ((lbuf.st_dev != buf.st_dev) || (lbuf.st_ino != buf.st_ino) || 220 (lbuf.st_uid != buf.st_uid) || (lbuf.st_gid != buf.st_gid) || 221 (lbuf.st_size!=buf.st_size)) 222 perrx("Somebody changed files from under us for job `%s' " 223 "- aborting", filename); 224 225 if (buf.st_nlink > 1) 226 perrx("Somebody is trying to run a linked script for job `%s'", 227 filename); 228 229 if ((fflags = fcntl(fd_in, F_GETFD)) < 0) 230 perr("Error in fcntl"); 231 232 (void)fcntl(fd_in, F_SETFD, fflags & ~FD_CLOEXEC); 233 234 (void)snprintf(fmt, sizeof(fmt), 235 "#!/bin/sh\n# atrun uid=%%u gid=%%u\n# mail %%%ds %%d", 236 LOGIN_NAME_MAX); 237 238 if (fscanf(stream, fmt, &nuid, &ngid, mailbuf, &send_mail) != 4) 239 perrx("File `%s' is in wrong format - aborting", filename); 240 241 if (mailbuf[0] == '-') 242 perrx("Illegal mail name `%s' in `%s'", mailbuf, filename); 243 244 mailname = mailbuf; 245 if (nuid != uid) 246 perrx("Job `%s' - userid %lu does not match file uid %lu", 247 filename, (unsigned long)nuid, (unsigned long)uid); 248 249 if (ngid != gid) 250 perrx("Job `%s' - groupid %lu does not match file gid %lu", 251 filename, (unsigned long)ngid, (unsigned long)gid); 252 253 (void)fclose(stream); 254 255 PRIV_START 256 257 if (chdir(_PATH_ATSPOOL) == -1) 258 perr("Cannot chdir to `%s'", _PATH_ATSPOOL); 259 260 /* 261 * Create a file to hold the output of the job we are about to 262 * run. Write the mail header. 263 */ 264 265 if ((fd_out = open(filename, 266 O_WRONLY | O_CREAT | O_EXCL, S_IWUSR | S_IRUSR)) == -1) 267 perr("Cannot create output file `%s'", filename); 268 269 PRIV_END 270 271 write_string(fd_out, "To: "); 272 write_string(fd_out, mailname); 273 write_string(fd_out, "\nSubject: Output from your job "); 274 write_string(fd_out, filename); 275 write_string(fd_out, "\n\n"); 276 if (fstat(fd_out, &buf) == -1) 277 perr("Error in fstat of output file descriptor"); 278 size = buf.st_size; 279 280 (void)close(STDIN_FILENO); 281 (void)close(STDOUT_FILENO); 282 (void)close(STDERR_FILENO); 283 284 pid = fork(); 285 if (pid < 0) 286 perr("Error in fork"); 287 else if (pid == 0) { 288 char *nul = NULL; 289 char **nenvp = &nul; 290 291 /* 292 * Set up things for the child; we want standard input from 293 * the input file, and standard output and error sent to 294 * our output file. 295 */ 296 if (lseek(fd_in, (off_t) 0, SEEK_SET) == (off_t)-1) 297 perr("Error in lseek"); 298 299 if (dup(fd_in) != STDIN_FILENO) 300 perr("Error in I/O redirection"); 301 302 if (dup(fd_out) != STDOUT_FILENO) 303 perr("Error in I/O redirection"); 304 305 if (dup(fd_out) != STDERR_FILENO) 306 perr("Error in I/O redirection"); 307 308 (void)close(fd_in); 309 (void)close(fd_out); 310 311 PRIV_START 312 313 if (chdir(_PATH_ATJOBS) == -1) 314 perr("Cannot chdir to `%s'", _PATH_ATJOBS); 315 316 queue = *filename; 317 318 if (queue > 'b') 319 nice(queue - 'b'); 320 321 become_user(pentry, uid); 322 323 (void)execle("/bin/sh", "sh", (char *)NULL, nenvp); 324 perr("Exec failed for /bin/sh"); 325 } 326 /* We're the parent. Let's wait. */ 327 (void)close(fd_in); 328 (void)close(fd_out); 329 (void)waitpid(pid, (int *)NULL, 0); 330 331 /* 332 * Send mail. Unlink the output file first, so it is deleted 333 * after the run. 334 */ 335 PRIV_START 336 337 if (stat(filename, &buf) == -1) 338 perr("Error in stat of output file `%s'", filename); 339 if (open(filename, O_RDONLY) != STDIN_FILENO) 340 perr("Open of jobfile `%s' failed", filename); 341 342 (void)unlink(filename); 343 344 PRIV_END 345 346 if ((buf.st_size != size) || send_mail) { 347 /* Fork off a child for sending mail */ 348 349 PRIV_START 350 351 become_user(pentry, uid); 352 353 execl(_PATH_SENDMAIL, "sendmail", "-F", "Atrun Service", 354 "-odi", "-oem", "-t", (char *) NULL); 355 perr("Exec failed for mail command `%s'", _PATH_SENDMAIL); 356 357 PRIV_END 358 } 359 exit(EXIT_SUCCESS); 360 } 361 362 /* Global functions */ 363 364 int 365 main(int argc, char *argv[]) 366 { 367 /* 368 * Browse through _PATH_ATJOBS, checking all the jobfiles wether 369 * they should be executed and or deleted. The queue is coded into 370 * the first byte of the job filename, the date (in minutes since 371 * Eon) as a hex number in the following eight bytes, followed by 372 * a dot and a serial number. A file which has not been executed 373 * yet is denoted by its execute - bit set. For those files which 374 * are to be executed, run_file() is called, which forks off a 375 * child which takes care of I/O redirection, forks off another 376 * child for execution and yet another one, optionally, for sending 377 * mail. Files which already have run are removed during the 378 * next invocation. 379 */ 380 DIR *spool; 381 struct dirent *dirent; 382 struct stat buf; 383 unsigned long ctm; 384 int jobno; 385 char queue; 386 time_t now, run_time; 387 char batch_name[] = "Z2345678901234"; 388 uid_t batch_uid; 389 gid_t batch_gid; 390 int c; 391 int run_batch; 392 double la, load_avg = ATRUN_MAXLOAD; 393 struct group *grp; 394 struct passwd *pwd; 395 396 openlog("atrun", LOG_PID, LOG_CRON); 397 398 if ((grp = getgrnam(nobody)) == NULL) 399 perrx("Cannot get gid for `%s'", nobody); 400 401 if ((pwd = getpwnam(nobody)) == NULL) 402 perrx("Cannot get uid for `%s'", nobody); 403 404 /* 405 * We don't need root privileges all the time; running under uid 406 * and gid nobody is fine except for privileged operations. 407 */ 408 RELINQUISH_PRIVS_ROOT(pwd->pw_uid, grp->gr_gid) 409 410 opterr = 0; 411 errno = 0; 412 while ((c = getopt(argc, argv, "dl:")) != -1) { 413 switch (c) { 414 case 'l': 415 if (sscanf(optarg, "%lf", &load_avg) != 1) 416 perrx("Bad argument to option -l: ", optarg); 417 if (load_avg <= 0) 418 load_avg = ATRUN_MAXLOAD; 419 break; 420 421 case 'd': 422 debug++; 423 break; 424 425 case '?': 426 perrx("Usage: %s [-l <loadav>] [-d]", getprogname()); 427 /*NOTREACHED*/ 428 429 default: 430 perrx("Invalid option: %c", c); 431 /*NOTREACHED*/ 432 } 433 } 434 435 PRIV_START 436 437 if (chdir(_PATH_ATJOBS) == -1) 438 perr("Cannot change directory to `%s'", _PATH_ATJOBS); 439 440 /* 441 * Main loop. Open spool directory for reading and look over all 442 * the files in there. If the filename indicates that the job 443 * should be run and the x bit is set, fork off a child which sets 444 * its user and group id to that of the files and exec a /bin/sh 445 * which executes the shell script. Unlink older files if they 446 * should no longer be run. For deletion, their r bit has to be 447 * turned on. 448 * 449 * Also, pick the oldest batch job to run, at most one per 450 * invocation of atrun. 451 */ 452 if ((spool = opendir(".")) == NULL) 453 perr("Cannot open `%s'", _PATH_ATJOBS); 454 455 PRIV_END 456 457 now = time(NULL); 458 run_batch = 0; 459 batch_uid = (uid_t) -1; 460 batch_gid = (gid_t) -1; 461 462 while ((dirent = readdir(spool)) != NULL) { 463 PRIV_START 464 465 if (stat(dirent->d_name, &buf) == -1) 466 perr("Cannot stat `%s' in `%s'", dirent->d_name, 467 _PATH_ATJOBS); 468 469 PRIV_END 470 471 /* We don't want directories */ 472 if (!S_ISREG(buf.st_mode)) 473 continue; 474 475 if (sscanf(dirent->d_name, "%c%5x%8lx", &queue, &jobno, 476 &ctm) != 3) 477 continue; 478 479 run_time = (time_t) ctm * 60; 480 481 if ((S_IXUSR & buf.st_mode) && (run_time <= now)) { 482 if (isupper((unsigned char)queue) && 483 (strcmp(batch_name, dirent->d_name) > 0)) { 484 run_batch = 1; 485 (void)strlcpy(batch_name, dirent->d_name, 486 sizeof(batch_name)); 487 batch_uid = buf.st_uid; 488 batch_gid = buf.st_gid; 489 } 490 491 /* The file is executable and old enough */ 492 if (islower((unsigned char)queue)) 493 run_file(dirent->d_name, buf.st_uid, 494 buf.st_gid); 495 } 496 497 /* Delete older files */ 498 if ((run_time < now) && !(S_IXUSR & buf.st_mode) && 499 (S_IRUSR & buf.st_mode)) { 500 PRIV_START 501 502 (void)unlink(dirent->d_name); 503 504 PRIV_END 505 } 506 } 507 508 /* Run the single batch file, if any */ 509 if (run_batch && ((getloadavg(&la, 1) == 1) && la < load_avg)) 510 run_file(batch_name, batch_uid, batch_gid); 511 512 closelog(); 513 return EXIT_SUCCESS; 514 } 515
Indexes created Wed Oct 15 03:09:54 GMT 2025