atrun.c revision 1.15
1 /* $NetBSD: atrun.c,v 1.15 2005/10/31 15:46:50 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 48 /* Local headers */ 49 50 #define MAIN 51 #include "privs.h" 52 #include "pathnames.h" 53 #include "atrun.h" 54 55 /* File scope variables */ 56 57 static char *namep; 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 1.15 2005/10/31 15:46:50 christos Exp $"); 62 #endif 63 64 static int debug = 0; 65 66 /* Local functions */ 67 static void perr __P((const char *)); 68 static void perr2 __P((char *, char *)); 69 static int write_string __P((int, const char *)); 70 static void run_file __P((const char *, uid_t, gid_t)); 71 static void become_user __P((struct passwd *, uid_t)); 72 73 static const char nobody[] = "nobody"; 74 75 int main __P((int, char *[])); 76 77 static void 78 perr(a) 79 const char *a; 80 { 81 if (debug) 82 warn("%s", a); 83 else 84 syslog(LOG_ERR, "%s: %m", a); 85 86 exit(EXIT_FAILURE); 87 } 88 89 static void 90 perr2(a, b) 91 char *a, *b; 92 { 93 if (debug) { 94 warn("%s%s", a, b); 95 } else 96 syslog(LOG_ERR, "%s%s: %m", a, b); 97 98 exit(EXIT_FAILURE); 99 } 100 101 static int 102 write_string(fd, a) 103 int fd; 104 const char *a; 105 { 106 return(write(fd, a, strlen(a))); 107 } 108 109 static void 110 become_user(pentry, uid) 111 struct passwd *pentry; 112 uid_t uid; 113 { 114 if (initgroups(pentry->pw_name, pentry->pw_gid) < 0) 115 perr("Cannot init group list"); 116 117 if (setegid(pentry->pw_gid) < 0 || setgid(pentry->pw_gid) < 0) 118 perr("Cannot change primary group"); 119 120 if (setsid() < 0) 121 perr("Cannot create a session"); 122 123 if (setlogin(pentry->pw_name) < 0) 124 perr("Cannot set login name"); 125 126 if (setuid(uid) < 0 || seteuid(uid) < 0) 127 perr("Cannot set user id"); 128 129 if (chdir(pentry->pw_dir) < 0) 130 chdir("/"); 131 } 132 133 static void 134 run_file(filename, uid, gid) 135 const char *filename; 136 uid_t uid; 137 gid_t gid; 138 { 139 /* 140 * Run a file by by spawning off a process which redirects I/O, 141 * spawns a subshell, then waits for it to complete and spawns another 142 * process to send mail to the user. 143 */ 144 pid_t pid; 145 int fd_out, fd_in; 146 int queue; 147 char mailbuf[LOGIN_NAME_MAX], fmt[49]; 148 char *mailname = NULL; 149 FILE *stream; 150 int send_mail = 0; 151 struct stat buf, lbuf; 152 off_t size; 153 struct passwd *pentry; 154 int fflags; 155 uint nuid; 156 uint ngid; 157 158 PRIV_START 159 160 if (chmod(filename, S_IRUSR) != 0) 161 perr("Cannot change file permissions"); 162 163 PRIV_END 164 165 pid = fork(); 166 if (pid == -1) 167 perr("Cannot fork"); 168 else if (pid != 0) 169 return; 170 171 /* 172 * Let's see who we mail to. Hopefully, we can read it from the 173 * command file; if not, send it to the owner, or, failing that, to 174 * root. 175 */ 176 177 pentry = getpwuid(uid); 178 if (pentry == NULL) { 179 syslog(LOG_ERR,"Userid %u not found - aborting job %s", 180 uid, filename); 181 exit(EXIT_FAILURE); 182 } 183 PRIV_START 184 185 stream = fopen(filename, "r"); 186 187 PRIV_END 188 189 if (pentry->pw_expire && time(NULL) >= pentry->pw_expire) { 190 syslog(LOG_ERR, "Userid %u has expired - aborting job %s", 191 uid, filename); 192 exit(EXIT_FAILURE); 193 } 194 195 if (stream == NULL) 196 perr("Cannot open input file"); 197 198 if ((fd_in = dup(fileno(stream))) < 0) 199 perr("Error duplicating input file descriptor"); 200 201 if (fstat(fd_in, &buf) == -1) 202 perr("Error in fstat of input file descriptor"); 203 204 PRIV_START 205 206 if (lstat(filename, &lbuf) == -1) 207 perr("Error in lstat of input file"); 208 209 PRIV_END 210 211 if (S_ISLNK(lbuf.st_mode)) { 212 syslog(LOG_ERR, "Symbolic link encountered in job %s - aborting", 213 filename); 214 exit(EXIT_FAILURE); 215 } 216 if ((lbuf.st_dev != buf.st_dev) || (lbuf.st_ino != buf.st_ino) || 217 (lbuf.st_uid != buf.st_uid) || (lbuf.st_gid != buf.st_gid) || 218 (lbuf.st_size!=buf.st_size)) { 219 syslog(LOG_ERR, "Somebody changed files from under us for job %s - aborting", filename); 220 exit(EXIT_FAILURE); 221 } 222 if (buf.st_nlink > 1) { 223 syslog(LOG_ERR, "Somebody is trying to run a linked script for job %s", 224 filename); 225 exit(EXIT_FAILURE); 226 } 227 if ((fflags = fcntl(fd_in, F_GETFD)) < 0) 228 perr("Error in fcntl"); 229 230 (void)fcntl(fd_in, F_SETFD, fflags & ~FD_CLOEXEC); 231 232 (void)snprintf(fmt, sizeof(fmt), 233 "#!/bin/sh\n# atrun uid=%%u gid=%%u\n# mail %%%ds %%d", 234 LOGIN_NAME_MAX); 235 if (fscanf(stream, fmt, &nuid, &ngid, mailbuf, &send_mail) != 4) { 236 syslog(LOG_ERR, "File %s is in wrong format - aborting", 237 filename); 238 exit(EXIT_FAILURE); 239 } 240 if (mailbuf[0] == '-') { 241 syslog(LOG_ERR, "illegal mail name %s in %s", mailbuf, filename); 242 exit(EXIT_FAILURE); 243 } 244 mailname = mailbuf; 245 if (nuid != uid) { 246 syslog(LOG_ERR, "Job %s - userid %u does not match file uid %u", 247 filename, nuid, uid); 248 exit(EXIT_FAILURE); 249 } 250 if (ngid != gid) { 251 syslog(LOG_ERR, "Job %s - groupid %u does not match file gid %u", 252 filename, ngid, gid); 253 exit(EXIT_FAILURE); 254 } 255 (void)fclose(stream); 256 257 PRIV_START 258 259 if (chdir(_PATH_ATSPOOL) < 0) 260 perr2("Cannot chdir to ", _PATH_ATSPOOL); 261 262 /* 263 * Create a file to hold the output of the job we are about to 264 * run. Write the mail header. 265 */ 266 267 if ((fd_out = open(filename, 268 O_WRONLY | O_CREAT | O_EXCL, S_IWUSR | S_IRUSR)) < 0) 269 perr("Cannot create output file"); 270 271 PRIV_END 272 273 write_string(fd_out, "To: "); 274 write_string(fd_out, mailname); 275 write_string(fd_out, "\nSubject: Output from your job "); 276 write_string(fd_out, filename); 277 write_string(fd_out, "\n\n"); 278 if (fstat(fd_out, &buf) == -1) 279 perr("Error in fstat of output file descriptor"); 280 size = buf.st_size; 281 282 (void)close(STDIN_FILENO); 283 (void)close(STDOUT_FILENO); 284 (void)close(STDERR_FILENO); 285 286 pid = fork(); 287 if (pid < 0) 288 perr("Error in fork"); 289 else if (pid == 0) { 290 char *nul = NULL; 291 char **nenvp = &nul; 292 293 /* 294 * Set up things for the child; we want standard input from 295 * the input file, and standard output and error sent to 296 * our output file. 297 */ 298 if (lseek(fd_in, (off_t) 0, SEEK_SET) < 0) 299 perr("Error in lseek"); 300 301 if (dup(fd_in) != STDIN_FILENO) 302 perr("Error in I/O redirection"); 303 304 if (dup(fd_out) != STDOUT_FILENO) 305 perr("Error in I/O redirection"); 306 307 if (dup(fd_out) != STDERR_FILENO) 308 perr("Error in I/O redirection"); 309 310 (void)close(fd_in); 311 (void)close(fd_out); 312 313 PRIV_START 314 315 if (chdir(_PATH_ATJOBS) < 0) 316 perr2("Cannot chdir to ", _PATH_ATJOBS); 317 318 queue = *filename; 319 320 if (queue > 'b') 321 nice(queue - 'b'); 322 323 become_user(pentry, uid); 324 325 if (execle("/bin/sh", "sh", (char *)NULL, nenvp) != 0) 326 perr("Exec failed for /bin/sh"); 327 328 PRIV_END 329 } 330 /* We're the parent. Let's wait. */ 331 (void)close(fd_in); 332 (void)close(fd_out); 333 waitpid(pid, (int *)NULL, 0); 334 335 /* 336 * Send mail. Unlink the output file first, so it is deleted 337 * after the run. 338 */ 339 PRIV_START 340 341 if (stat(filename, &buf) == -1) 342 perr("Error in stat of output file"); 343 if (open(filename, O_RDONLY) != STDIN_FILENO) 344 perr("Open of jobfile failed"); 345 346 (void)unlink(filename); 347 348 PRIV_END 349 350 if ((buf.st_size != size) || send_mail) { 351 /* Fork off a child for sending mail */ 352 353 PRIV_START 354 355 become_user(pentry, uid); 356 357 execl(_PATH_SENDMAIL, "sendmail", "-F", "Atrun Service", 358 "-odi", "-oem", "-t", (char *) NULL); 359 perr("Exec failed for mail command"); 360 361 PRIV_END 362 } 363 exit(EXIT_SUCCESS); 364 } 365 366 /* Global functions */ 367 368 int 369 main(argc, argv) 370 int argc; 371 char *argv[]; 372 { 373 /* 374 * Browse through _PATH_ATJOBS, checking all the jobfiles wether 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 if ((grp = getgrnam(nobody)) == NULL) 403 errx(1, "Cannot get gid for `%s'", nobody); 404 405 if ((pwd = getpwnam(nobody)) == NULL) 406 errx(1, "Cannot get uid for `%s'", nobody); 407 408 openlog("atrun", LOG_PID, LOG_CRON); 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 RELINQUISH_PRIVS_ROOT(pwd->pw_uid, grp->gr_gid) 415 416 417 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 perr("garbled option -l"); 424 if (load_avg <= 0.) 425 load_avg = ATRUN_MAXLOAD; 426 break; 427 428 case 'd': 429 debug++; 430 break; 431 432 case '?': 433 perr("unknown option"); 434 break; 435 436 default: 437 perr("idiotic option - aborted"); 438 break; 439 } 440 } 441 442 namep = argv[0]; 443 444 PRIV_START 445 446 if (chdir(_PATH_ATJOBS) != 0) 447 perr2("Cannot change to ", _PATH_ATJOBS); 448 449 450 /* 451 * Main loop. Open spool directory for reading and look over all 452 * the files in there. If the filename indicates that the job 453 * should be run and the x bit is set, fork off a child which sets 454 * its user and group id to that of the files and exec a /bin/sh 455 * which executes the shell script. Unlink older files if they 456 * should no longer be run. For deletion, their r bit has to be 457 * turned on. 458 * 459 * Also, pick the oldest batch job to run, at most one per 460 * invocation of atrun. 461 */ 462 if ((spool = opendir(".")) == NULL) 463 perr2("Cannot read ", _PATH_ATJOBS); 464 465 PRIV_END 466 467 now = time(NULL); 468 run_batch = 0; 469 batch_uid = (uid_t) -1; 470 batch_gid = (gid_t) -1; 471 472 while ((dirent = readdir(spool)) != NULL) { 473 PRIV_START 474 475 if (stat(dirent->d_name, &buf) != 0) 476 perr2("Cannot stat in ", _PATH_ATJOBS); 477 478 PRIV_END 479 480 /* We don't want directories */ 481 if (!S_ISREG(buf.st_mode)) 482 continue; 483 484 if (sscanf(dirent->d_name, "%c%5x%8lx", &queue, &jobno, &ctm) != 3) 485 continue; 486 487 run_time = (time_t) ctm * 60; 488 489 if ((S_IXUSR & buf.st_mode) && (run_time <= now)) { 490 if (isupper((unsigned char)queue) && 491 (strcmp(batch_name, dirent->d_name) > 0)) { 492 run_batch = 1; 493 (void)strlcpy(batch_name, dirent->d_name, 494 sizeof(batch_name)); 495 batch_uid = buf.st_uid; 496 batch_gid = buf.st_gid; 497 } 498 499 /* The file is executable and old enough */ 500 if (islower((unsigned char)queue)) 501 run_file(dirent->d_name, buf.st_uid, 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 PRIV_START 508 509 (void)unlink(dirent->d_name); 510 511 PRIV_END 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 exit(EXIT_SUCCESS); 521 } 522
Indexes created Tue Oct 14 00:09:49 GMT 2025