atrun.c revision 1.12
1 /* $NetBSD: atrun.c,v 1.12 2003/03/03 17:14:36 dsl 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 <err.h> 45 #include <paths.h> 46 47 /* Local headers */ 48 49 #define MAIN 50 #include "privs.h" 51 #include "pathnames.h" 52 #include "atrun.h" 53 54 /* File scope variables */ 55 56 static char *namep; 57 #if 0 58 static char rcsid[] = "$OpenBSD: atrun.c,v 1.7 1997/09/08 22:12:10 millert Exp $"; 59 #else 60 __RCSID("$NetBSD: atrun.c,v 1.12 2003/03/03 17:14:36 dsl Exp $"); 61 #endif 62 63 static int debug = 0; 64 65 /* Local functions */ 66 static void perr __P((const char *)); 67 static void perr2 __P((char *, char *)); 68 static int write_string __P((int, const char *)); 69 static void run_file __P((const char *, uid_t, gid_t)); 70 static void become_user __P((struct passwd *, uid_t)); 71 72 int main __P((int, char *[])); 73 74 static void 75 perr(a) 76 const char *a; 77 { 78 if (debug) 79 warn("%s", a); 80 else 81 syslog(LOG_ERR, "%s: %m", a); 82 83 exit(EXIT_FAILURE); 84 } 85 86 static void 87 perr2(a, b) 88 char *a, *b; 89 { 90 if (debug) { 91 warn("%s%s", a, b); 92 } else 93 syslog(LOG_ERR, "%s%s: %m", a, b); 94 95 exit(EXIT_FAILURE); 96 } 97 98 static int 99 write_string(fd, a) 100 int fd; 101 const char *a; 102 { 103 return(write(fd, a, strlen(a))); 104 } 105 106 static void 107 become_user(pentry, uid) 108 struct passwd *pentry; 109 uid_t uid; 110 { 111 if (initgroups(pentry->pw_name, pentry->pw_gid) < 0) 112 perr("Cannot init group list"); 113 114 if (setegid(pentry->pw_gid) < 0 || setgid(pentry->pw_gid) < 0) 115 perr("Cannot change primary group"); 116 117 if (setsid() < 0) 118 perr("Cannot create a session"); 119 120 if (setlogin(pentry->pw_name) < 0) 121 perr("Cannot set login name"); 122 123 if (setuid(uid) < 0 || seteuid(uid) < 0) 124 perr("Cannot set user id"); 125 126 if (chdir(pentry->pw_dir) < 0) 127 chdir("/"); 128 } 129 130 static void 131 run_file(filename, uid, gid) 132 const char *filename; 133 uid_t uid; 134 gid_t gid; 135 { 136 /* 137 * Run a file by by spawning off a process which redirects I/O, 138 * spawns a subshell, then waits for it to complete and spawns another 139 * process to send mail to the user. 140 */ 141 pid_t pid; 142 int fd_out, fd_in; 143 int queue; 144 char mailbuf[LOGIN_NAME_MAX], fmt[49]; 145 char *mailname = NULL; 146 FILE *stream; 147 int send_mail = 0; 148 struct stat buf, lbuf; 149 off_t size; 150 struct passwd *pentry; 151 int fflags; 152 uint nuid; 153 uint ngid; 154 155 PRIV_START 156 157 if (chmod(filename, S_IRUSR) != 0) 158 perr("Cannot change file permissions"); 159 160 PRIV_END 161 162 pid = fork(); 163 if (pid == -1) 164 perr("Cannot fork"); 165 else if (pid != 0) 166 return; 167 168 /* 169 * Let's see who we mail to. Hopefully, we can read it from the 170 * command file; if not, send it to the owner, or, failing that, to 171 * root. 172 */ 173 174 pentry = getpwuid(uid); 175 if (pentry == NULL) { 176 syslog(LOG_ERR,"Userid %u not found - aborting job %s", 177 uid, filename); 178 exit(EXIT_FAILURE); 179 } 180 PRIV_START 181 182 stream = fopen(filename, "r"); 183 184 PRIV_END 185 186 if (pentry->pw_expire && time(NULL) >= pentry->pw_expire) { 187 syslog(LOG_ERR, "Userid %u has expired - aborting job %s", 188 uid, filename); 189 exit(EXIT_FAILURE); 190 } 191 192 if (stream == NULL) 193 perr("Cannot open input file"); 194 195 if ((fd_in = dup(fileno(stream))) < 0) 196 perr("Error duplicating input file descriptor"); 197 198 if (fstat(fd_in, &buf) == -1) 199 perr("Error in fstat of input file descriptor"); 200 201 PRIV_START 202 203 if (lstat(filename, &lbuf) == -1) 204 perr("Error in lstat of input file"); 205 206 PRIV_END 207 208 if (S_ISLNK(lbuf.st_mode)) { 209 syslog(LOG_ERR, "Symbolic link encountered in job %s - aborting", 210 filename); 211 exit(EXIT_FAILURE); 212 } 213 if ((lbuf.st_dev != buf.st_dev) || (lbuf.st_ino != buf.st_ino) || 214 (lbuf.st_uid != buf.st_uid) || (lbuf.st_gid != buf.st_gid) || 215 (lbuf.st_size!=buf.st_size)) { 216 syslog(LOG_ERR, "Somebody changed files from under us for job %s - aborting", filename); 217 exit(EXIT_FAILURE); 218 } 219 if (buf.st_nlink > 1) { 220 syslog(LOG_ERR, "Somebody is trying to run a linked script for job %s", 221 filename); 222 exit(EXIT_FAILURE); 223 } 224 if ((fflags = fcntl(fd_in, F_GETFD)) < 0) 225 perr("Error in fcntl"); 226 227 (void)fcntl(fd_in, F_SETFD, fflags & ~FD_CLOEXEC); 228 229 (void)snprintf(fmt, sizeof(fmt), 230 "#!/bin/sh\n# atrun uid=%%u gid=%%u\n# mail %%%ds %%d", 231 LOGIN_NAME_MAX); 232 if (fscanf(stream, fmt, &nuid, &ngid, mailbuf, &send_mail) != 4) { 233 syslog(LOG_ERR, "File %s is in wrong format - aborting", 234 filename); 235 exit(EXIT_FAILURE); 236 } 237 if (mailbuf[0] == '-') { 238 syslog(LOG_ERR, "illegal mail name %s in %s", mailbuf, filename); 239 exit(EXIT_FAILURE); 240 } 241 mailname = mailbuf; 242 if (nuid != uid) { 243 syslog(LOG_ERR, "Job %s - userid %u does not match file uid %u", 244 filename, nuid, uid); 245 exit(EXIT_FAILURE); 246 } 247 if (ngid != gid) { 248 syslog(LOG_ERR, "Job %s - groupid %u does not match file gid %u", 249 filename, ngid, gid); 250 exit(EXIT_FAILURE); 251 } 252 (void)fclose(stream); 253 254 PRIV_START 255 256 if (chdir(_PATH_ATSPOOL) < 0) 257 perr2("Cannot chdir to ", _PATH_ATSPOOL); 258 259 /* 260 * Create a file to hold the output of the job we are about to 261 * run. Write the mail header. 262 */ 263 264 if ((fd_out = open(filename, 265 O_WRONLY | O_CREAT | O_EXCL, S_IWUSR | S_IRUSR)) < 0) 266 perr("Cannot create output file"); 267 268 PRIV_END 269 270 write_string(fd_out, "To: "); 271 write_string(fd_out, mailname); 272 write_string(fd_out, "\nSubject: Output from your job "); 273 write_string(fd_out, filename); 274 write_string(fd_out, "\n\n"); 275 if (fstat(fd_out, &buf) == -1) 276 perr("Error in fstat of output file descriptor"); 277 size = buf.st_size; 278 279 (void)close(STDIN_FILENO); 280 (void)close(STDOUT_FILENO); 281 (void)close(STDERR_FILENO); 282 283 pid = fork(); 284 if (pid < 0) 285 perr("Error in fork"); 286 else if (pid == 0) { 287 char *nul = NULL; 288 char **nenvp = &nul; 289 290 /* 291 * Set up things for the child; we want standard input from 292 * the input file, and standard output and error sent to 293 * our output file. 294 */ 295 if (lseek(fd_in, (off_t) 0, SEEK_SET) < 0) 296 perr("Error in lseek"); 297 298 if (dup(fd_in) != STDIN_FILENO) 299 perr("Error in I/O redirection"); 300 301 if (dup(fd_out) != STDOUT_FILENO) 302 perr("Error in I/O redirection"); 303 304 if (dup(fd_out) != STDERR_FILENO) 305 perr("Error in I/O redirection"); 306 307 (void)close(fd_in); 308 (void)close(fd_out); 309 310 PRIV_START 311 312 if (chdir(_PATH_ATJOBS) < 0) 313 perr2("Cannot chdir to ", _PATH_ATJOBS); 314 315 queue = *filename; 316 317 if (queue > 'b') 318 nice(queue - 'b'); 319 320 become_user(pentry, uid); 321 322 if (execle("/bin/sh", "sh", (char *)NULL, nenvp) != 0) 323 perr("Exec failed for /bin/sh"); 324 325 PRIV_END 326 } 327 /* We're the parent. Let's wait. */ 328 (void)close(fd_in); 329 (void)close(fd_out); 330 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"); 340 if (open(filename, O_RDONLY) != STDIN_FILENO) 341 perr("Open of jobfile failed"); 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"); 357 358 PRIV_END 359 } 360 exit(EXIT_SUCCESS); 361 } 362 363 /* Global functions */ 364 365 int 366 main(argc, argv) 367 int argc; 368 char *argv[]; 369 { 370 /* 371 * Browse through _PATH_ATJOBS, checking all the jobfiles wether 372 * they should be executed and or deleted. The queue is coded into 373 * the first byte of the job filename, the date (in minutes since 374 * Eon) as a hex number in the following eight bytes, followed by 375 * a dot and a serial number. A file which has not been executed 376 * yet is denoted by its execute - bit set. For those files which 377 * are to be executed, run_file() is called, which forks off a 378 * child which takes care of I/O redirection, forks off another 379 * child for execution and yet another one, optionally, for sending 380 * mail. Files which already have run are removed during the 381 * next invocation. 382 */ 383 DIR *spool; 384 struct dirent *dirent; 385 struct stat buf; 386 unsigned long ctm; 387 int jobno; 388 char queue; 389 time_t now, run_time; 390 char batch_name[] = "Z2345678901234"; 391 uid_t batch_uid; 392 gid_t batch_gid; 393 int c; 394 int run_batch; 395 double la, load_avg = ATRUN_MAXLOAD; 396 397 /* 398 * We don't need root privileges all the time; running under uid 399 * and gid nobody is fine except for privileged operations. 400 */ 401 RELINQUISH_PRIVS_ROOT(NOBODY_UID, NOBODY_GID) 402 403 openlog("atrun", LOG_PID, LOG_CRON); 404 405 opterr = 0; 406 errno = 0; 407 while ((c = getopt(argc, argv, "dl:")) != -1) { 408 switch (c) { 409 case 'l': 410 if (sscanf(optarg, "%lf", &load_avg) != 1) 411 perr("garbled option -l"); 412 if (load_avg <= 0.) 413 load_avg = ATRUN_MAXLOAD; 414 break; 415 416 case 'd': 417 debug++; 418 break; 419 420 case '?': 421 perr("unknown option"); 422 break; 423 424 default: 425 perr("idiotic option - aborted"); 426 break; 427 } 428 } 429 430 namep = argv[0]; 431 432 PRIV_START 433 434 if (chdir(_PATH_ATJOBS) != 0) 435 perr2("Cannot change to ", _PATH_ATJOBS); 436 437 438 /* 439 * Main loop. Open spool directory for reading and look over all 440 * the files in there. If the filename indicates that the job 441 * should be run and the x bit is set, fork off a child which sets 442 * its user and group id to that of the files and exec a /bin/sh 443 * which executes the shell script. Unlink older files if they 444 * should no longer be run. For deletion, their r bit has to be 445 * turned on. 446 * 447 * Also, pick the oldest batch job to run, at most one per 448 * invocation of atrun. 449 */ 450 if ((spool = opendir(".")) == NULL) 451 perr2("Cannot read ", _PATH_ATJOBS); 452 453 PRIV_END 454 455 now = time(NULL); 456 run_batch = 0; 457 batch_uid = (uid_t) -1; 458 batch_gid = (gid_t) -1; 459 460 while ((dirent = readdir(spool)) != NULL) { 461 PRIV_START 462 463 if (stat(dirent->d_name, &buf) != 0) 464 perr2("Cannot stat in ", _PATH_ATJOBS); 465 466 PRIV_END 467 468 /* We don't want directories */ 469 if (!S_ISREG(buf.st_mode)) 470 continue; 471 472 if (sscanf(dirent->d_name, "%c%5x%8lx", &queue, &jobno, &ctm) != 3) 473 continue; 474 475 run_time = (time_t) ctm * 60; 476 477 if ((S_IXUSR & buf.st_mode) && (run_time <= now)) { 478 if (isupper(queue) && 479 (strcmp(batch_name, dirent->d_name) > 0)) { 480 run_batch = 1; 481 (void)strncpy(batch_name, dirent->d_name, 482 sizeof(batch_name)); 483 batch_uid = buf.st_uid; 484 batch_gid = buf.st_gid; 485 } 486 487 /* The file is executable and old enough */ 488 if (islower(queue)) 489 run_file(dirent->d_name, buf.st_uid, buf.st_gid); 490 } 491 492 /* Delete older files */ 493 if ((run_time < now) && !(S_IXUSR & buf.st_mode) && 494 (S_IRUSR & buf.st_mode)) { 495 PRIV_START 496 497 (void)unlink(dirent->d_name); 498 499 PRIV_END 500 } 501 } 502 503 /* Run the single batch file, if any */ 504 if (run_batch && ((getloadavg(&la, 1) == 1) && la < load_avg)) 505 run_file(batch_name, batch_uid, batch_gid); 506 507 closelog(); 508 exit(EXIT_SUCCESS); 509 } 510
Indexes created Mon Oct 13 16:09:52 GMT 2025