1 /* $NetBSD: atrun.c,v 1.22 2016/03/13 00:32:09 dholland 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 #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 1.22 2016/03/13 00:32:09 dholland Exp $"); 62 #endif 63 64 static int debug = 0; 65 66 /* Local functions */ 67 static void perr(const char *, ...) __dead; 68 static void perrx(const char *, ...) __dead; 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 __dead void 111 privs_fail(const char *msg) 112 { 113 perr("%s", msg); 114 } 115 116 static int 117 write_string(int fd, const char *a) 118 { 119 return write(fd, a, strlen(a)); 120 } 121 122 static void 123 become_user(struct passwd *pentry, uid_t uid) 124 { 125 if (initgroups(pentry->pw_name, pentry->pw_gid) == -1) 126 perr("Cannot init group list for `%s'", pentry->pw_name); 127 128 if (setegid(pentry->pw_gid) == -1 || setgid(pentry->pw_gid) == -1) 129 perr("Cannot change primary group to %lu", 130 (unsigned long)pentry->pw_gid); 131 132 if (setsid() == -1) 133 perr("Cannot create a session"); 134 135 if (setlogin(pentry->pw_name) == -1) 136 perr("Cannot set login name to `%s'", pentry->pw_name); 137 138 if (setuid(uid) == -1 || seteuid(uid) == -1) 139 perr("Cannot set user id to %lu", (unsigned long)uid); 140 141 if (chdir(pentry->pw_dir) == -1) 142 (void)chdir("/"); 143 } 144 145 static void 146 run_file(const char *filename, uid_t uid, gid_t gid) 147 { 148 /* 149 * Run a file by by spawning off a process which redirects I/O, 150 * spawns a subshell, then waits for it to complete and spawns another 151 * process to send mail to the user. 152 */ 153 pid_t pid; 154 int fd_out, fd_in; 155 int queue; 156 char mailbuf[LOGIN_NAME_MAX], fmt[49]; 157 char *mailname = NULL; 158 FILE *stream; 159 int send_mail = 0; 160 struct stat buf, lbuf; 161 off_t size; 162 struct passwd *pentry; 163 int fflags; 164 uid_t nuid; 165 gid_t ngid; 166 int serrno; 167 168 privs_enter(); 169 170 if (chmod(filename, S_IRUSR) == -1) 171 perr("Cannot change file permissions to `%s'", filename); 172 173 privs_exit(); 174 175 pid = fork(); 176 if (pid == -1) 177 perr("Cannot fork"); 178 else if (pid != 0) 179 return; 180 181 /* 182 * Let's see who we mail to. Hopefully, we can read it from the 183 * command file; if not, send it to the owner, or, failing that, to 184 * root. 185 */ 186 187 pentry = getpwuid(uid); 188 if (pentry == NULL) 189 perrx("Userid %lu not found - aborting job `%s'", 190 (unsigned long)uid, filename); 191 192 privs_enter(); 193 194 stream = fopen(filename, "r"); 195 serrno = errno; 196 197 privs_exit(); 198 199 if (stream == NULL) { 200 errno = serrno; 201 perr("Cannot open input file"); 202 } 203 204 if (pentry->pw_expire && time(NULL) >= pentry->pw_expire) 205 perrx("Userid %lu has expired - aborting job `%s'", 206 (unsigned long)uid, filename); 207 208 if ((fd_in = dup(fileno(stream))) == -1) 209 perr("Error duplicating input file descriptor"); 210 211 if (fstat(fd_in, &buf) == -1) 212 perr("Error in fstat of input file descriptor"); 213 214 privs_enter(); 215 216 if (lstat(filename, &lbuf) == -1) 217 perr("Error in lstat of `%s'", filename); 218 219 privs_exit(); 220 221 if (S_ISLNK(lbuf.st_mode)) 222 perrx("Symbolic link encountered in job `%s' - aborting", 223 filename); 224 225 if ((lbuf.st_dev != buf.st_dev) || (lbuf.st_ino != buf.st_ino) || 226 (lbuf.st_uid != buf.st_uid) || (lbuf.st_gid != buf.st_gid) || 227 (lbuf.st_size!=buf.st_size)) 228 perrx("Somebody changed files from under us for job `%s' " 229 "- aborting", filename); 230 231 if (buf.st_nlink > 1) 232 perrx("Somebody is trying to run a linked script for job `%s'", 233 filename); 234 235 if ((fflags = fcntl(fd_in, F_GETFD)) < 0) 236 perr("Error in fcntl"); 237 238 (void)fcntl(fd_in, F_SETFD, fflags & ~FD_CLOEXEC); 239 240 (void)snprintf(fmt, sizeof(fmt), 241 "#!/bin/sh\n# atrun uid=%%u gid=%%u\n# mail %%%ds %%d", 242 LOGIN_NAME_MAX); 243 244 if (fscanf(stream, fmt, &nuid, &ngid, mailbuf, &send_mail) != 4) 245 perrx("File `%s' is in wrong format - aborting", filename); 246 247 if (mailbuf[0] == '-') 248 perrx("Illegal mail name `%s' in `%s'", mailbuf, filename); 249 250 mailname = mailbuf; 251 if (nuid != uid) 252 perrx("Job `%s' - userid %lu does not match file uid %lu", 253 filename, (unsigned long)nuid, (unsigned long)uid); 254 255 if (ngid != gid) 256 perrx("Job `%s' - groupid %lu does not match file gid %lu", 257 filename, (unsigned long)ngid, (unsigned long)gid); 258 259 (void)fclose(stream); 260 261 privs_enter(); 262 263 if (chdir(_PATH_ATSPOOL) == -1) 264 perr("Cannot chdir to `%s'", _PATH_ATSPOOL); 265 266 /* 267 * Create a file to hold the output of the job we are about to 268 * run. Write the mail header. 269 */ 270 271 if ((fd_out = open(filename, 272 O_WRONLY | O_CREAT | O_EXCL, S_IWUSR | S_IRUSR)) == -1) 273 perr("Cannot create output file `%s'", filename); 274 275 privs_exit(); 276 277 write_string(fd_out, "To: "); 278 write_string(fd_out, mailname); 279 write_string(fd_out, "\nSubject: Output from your job "); 280 write_string(fd_out, filename); 281 write_string(fd_out, "\n\n"); 282 if (fstat(fd_out, &buf) == -1) 283 perr("Error in fstat of output file descriptor"); 284 size = buf.st_size; 285 286 (void)close(STDIN_FILENO); 287 (void)close(STDOUT_FILENO); 288 (void)close(STDERR_FILENO); 289 290 pid = fork(); 291 if (pid < 0) 292 perr("Error in fork"); 293 else if (pid == 0) { 294 char *nul = NULL; 295 char **nenvp = &nul; 296 297 /* 298 * Set up things for the child; we want standard input from 299 * the input file, and standard output and error sent to 300 * our output file. 301 */ 302 if (lseek(fd_in, (off_t) 0, SEEK_SET) == (off_t)-1) 303 perr("Error in lseek"); 304 305 if (dup(fd_in) != STDIN_FILENO) 306 perr("Error in I/O redirection"); 307 308 if (dup(fd_out) != STDOUT_FILENO) 309 perr("Error in I/O redirection"); 310 311 if (dup(fd_out) != STDERR_FILENO) 312 perr("Error in I/O redirection"); 313 314 (void)close(fd_in); 315 (void)close(fd_out); 316 317 privs_enter(); 318 319 if (chdir(_PATH_ATJOBS) == -1) 320 perr("Cannot chdir to `%s'", _PATH_ATJOBS); 321 322 queue = *filename; 323 324 if (queue > 'b') 325 nice(queue - 'b'); 326 327 become_user(pentry, uid); 328 329 (void)execle("/bin/sh", "sh", (char *)NULL, nenvp); 330 perr("Exec failed for /bin/sh"); 331 } 332 /* We're the parent. Let's wait. */ 333 (void)close(fd_in); 334 (void)close(fd_out); 335 (void)waitpid(pid, NULL, 0); 336 337 /* 338 * Send mail. Unlink the output file first, so it is deleted 339 * after the run. 340 */ 341 privs_enter(); 342 343 if (stat(filename, &buf) == -1) 344 perr("Error in stat of output file `%s'", filename); 345 if (open(filename, O_RDONLY) != STDIN_FILENO) 346 perr("Open of jobfile `%s' failed", filename); 347 348 (void)unlink(filename); 349 350 privs_exit(); 351 352 if ((buf.st_size != size) || send_mail) { 353 /* Fork off a child for sending mail */ 354 355 privs_enter(); 356 357 become_user(pentry, uid); 358 359 execl(_PATH_SENDMAIL, "sendmail", "-F", "Atrun Service", 360 "-odi", "-oem", "-t", (char *) NULL); 361 perr("Exec failed for mail command `%s'", _PATH_SENDMAIL); 362 363 privs_exit(); 364 } 365 exit(EXIT_SUCCESS); 366 } 367 368 /* Global functions */ 369 370 int 371 main(int argc, char *argv[]) 372 { 373 /* 374 * Browse through _PATH_ATJOBS, checking all the jobfiles whether 375 * they should be executed and or deleted. The queue is coded into 376 * the first byte of the job filename, the date (in minutes since 377 * Eon) as a hex number in the following eight bytes, followed by 378 * a dot and a serial number. A file which has not been executed 379 * yet is denoted by its execute - bit set. For those files which 380 * are to be executed, run_file() is called, which forks off a 381 * child which takes care of I/O redirection, forks off another 382 * child for execution and yet another one, optionally, for sending 383 * mail. Files which already have run are removed during the 384 * next invocation. 385 */ 386 DIR *spool; 387 struct dirent *dirent; 388 struct stat buf; 389 unsigned long ctm; 390 int jobno; 391 char queue; 392 time_t now, run_time; 393 char batch_name[] = "Z2345678901234"; 394 uid_t batch_uid; 395 gid_t batch_gid; 396 int c; 397 int run_batch; 398 double la, load_avg = ATRUN_MAXLOAD; 399 struct group *grp; 400 struct passwd *pwd; 401 402 openlog("atrun", LOG_PID, LOG_CRON); 403 404 if ((grp = getgrnam(nobody)) == NULL) 405 perrx("Cannot get gid for `%s'", nobody); 406 407 if ((pwd = getpwnam(nobody)) == NULL) 408 perrx("Cannot get uid for `%s'", nobody); 409 410 /* 411 * We don't need root privileges all the time; running under uid 412 * and gid nobody is fine except for privileged operations. 413 */ 414 privs_relinquish_root(pwd->pw_uid, grp->gr_gid); 415 416 opterr = 0; 417 errno = 0; 418 while ((c = getopt(argc, argv, "dl:")) != -1) { 419 switch (c) { 420 case 'l': 421 if (sscanf(optarg, "%lf", &load_avg) != 1) 422 perrx("Bad argument to option -l: ", optarg); 423 if (load_avg <= 0) 424 load_avg = ATRUN_MAXLOAD; 425 break; 426 427 case 'd': 428 debug++; 429 break; 430 431 case '?': 432 perrx("Usage: %s [-l <loadav>] [-d]", getprogname()); 433 /*NOTREACHED*/ 434 435 default: 436 perrx("Invalid option: %c", c); 437 /*NOTREACHED*/ 438 } 439 } 440 441 privs_enter(); 442 443 if (chdir(_PATH_ATJOBS) == -1) 444 perr("Cannot change directory to `%s'", _PATH_ATJOBS); 445 446 /* 447 * Main loop. Open spool directory for reading and look over all 448 * the files in there. If the filename indicates that the job 449 * should be run and the x bit is set, fork off a child which sets 450 * its user and group id to that of the files and exec a /bin/sh 451 * which executes the shell script. Unlink older files if they 452 * should no longer be run. For deletion, their r bit has to be 453 * turned on. 454 * 455 * Also, pick the oldest batch job to run, at most one per 456 * invocation of atrun. 457 */ 458 if ((spool = opendir(".")) == NULL) 459 perr("Cannot open `%s'", _PATH_ATJOBS); 460 461 privs_exit(); 462 463 now = time(NULL); 464 run_batch = 0; 465 batch_uid = (uid_t) -1; 466 batch_gid = (gid_t) -1; 467 468 while ((dirent = readdir(spool)) != NULL) { 469 privs_enter(); 470 471 if (stat(dirent->d_name, &buf) == -1) 472 perr("Cannot stat `%s' in `%s'", dirent->d_name, 473 _PATH_ATJOBS); 474 475 privs_exit(); 476 477 /* We don't want directories */ 478 if (!S_ISREG(buf.st_mode)) 479 continue; 480 481 if (sscanf(dirent->d_name, "%c%5x%8lx", &queue, &jobno, 482 &ctm) != 3) 483 continue; 484 485 run_time = (time_t) ctm * 60; 486 487 if ((S_IXUSR & buf.st_mode) && (run_time <= now)) { 488 if (isupper((unsigned char)queue) && 489 (strcmp(batch_name, dirent->d_name) > 0)) { 490 run_batch = 1; 491 (void)strlcpy(batch_name, dirent->d_name, 492 sizeof(batch_name)); 493 batch_uid = buf.st_uid; 494 batch_gid = buf.st_gid; 495 } 496 497 /* The file is executable and old enough */ 498 if (islower((unsigned char)queue)) 499 run_file(dirent->d_name, buf.st_uid, 500 buf.st_gid); 501 } 502 503 /* Delete older files */ 504 if ((run_time < now) && !(S_IXUSR & buf.st_mode) && 505 (S_IRUSR & buf.st_mode)) { 506 privs_enter(); 507 508 (void)unlink(dirent->d_name); 509 510 privs_exit(); 511 } 512 } 513 514 /* Run the single batch file, if any */ 515 if (run_batch && ((getloadavg(&la, 1) == 1) && la < load_avg)) 516 run_file(batch_name, batch_uid, batch_gid); 517 518 closelog(); 519 return EXIT_SUCCESS; 520 } 521