1 /* $NetBSD: atrun.c,v 1.11 2002/07/29 00:36:44 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 <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 1.11 2002/07/29 00:36:44 christos 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 (setlogin(pentry->pw_name) < 0) 118 perr("Cannot set login name"); 119 120 if (setuid(uid) < 0 || seteuid(uid) < 0) 121 perr("Cannot set user id"); 122 123 if (chdir(pentry->pw_dir) < 0) 124 chdir("/"); 125 } 126 127 static void 128 run_file(filename, uid, gid) 129 const char *filename; 130 uid_t uid; 131 gid_t gid; 132 { 133 /* 134 * Run a file by by spawning off a process which redirects I/O, 135 * spawns a subshell, then waits for it to complete and spawns another 136 * process to send mail to the user. 137 */ 138 pid_t pid; 139 int fd_out, fd_in; 140 int queue; 141 char mailbuf[LOGIN_NAME_MAX], fmt[49]; 142 char *mailname = NULL; 143 FILE *stream; 144 int send_mail = 0; 145 struct stat buf, lbuf; 146 off_t size; 147 struct passwd *pentry; 148 int fflags; 149 uint nuid; 150 uint ngid; 151 152 PRIV_START 153 154 if (chmod(filename, S_IRUSR) != 0) 155 perr("Cannot change file permissions"); 156 157 PRIV_END 158 159 pid = fork(); 160 if (pid == -1) 161 perr("Cannot fork"); 162 else if (pid != 0) 163 return; 164 165 /* 166 * Let's see who we mail to. Hopefully, we can read it from the 167 * command file; if not, send it to the owner, or, failing that, to 168 * root. 169 */ 170 171 pentry = getpwuid(uid); 172 if (pentry == NULL) { 173 syslog(LOG_ERR,"Userid %u not found - aborting job %s", 174 uid, filename); 175 exit(EXIT_FAILURE); 176 } 177 PRIV_START 178 179 stream = fopen(filename, "r"); 180 181 PRIV_END 182 183 if (pentry->pw_expire && time(NULL) >= pentry->pw_expire) { 184 syslog(LOG_ERR, "Userid %u has expired - aborting job %s", 185 uid, filename); 186 exit(EXIT_FAILURE); 187 } 188 189 if (stream == NULL) 190 perr("Cannot open input file"); 191 192 if ((fd_in = dup(fileno(stream))) < 0) 193 perr("Error duplicating input file descriptor"); 194 195 if (fstat(fd_in, &buf) == -1) 196 perr("Error in fstat of input file descriptor"); 197 198 PRIV_START 199 200 if (lstat(filename, &lbuf) == -1) 201 perr("Error in lstat of input file"); 202 203 PRIV_END 204 205 if (S_ISLNK(lbuf.st_mode)) { 206 syslog(LOG_ERR, "Symbolic link encountered in job %s - aborting", 207 filename); 208 exit(EXIT_FAILURE); 209 } 210 if ((lbuf.st_dev != buf.st_dev) || (lbuf.st_ino != buf.st_ino) || 211 (lbuf.st_uid != buf.st_uid) || (lbuf.st_gid != buf.st_gid) || 212 (lbuf.st_size!=buf.st_size)) { 213 syslog(LOG_ERR, "Somebody changed files from under us for job %s - aborting", filename); 214 exit(EXIT_FAILURE); 215 } 216 if (buf.st_nlink > 1) { 217 syslog(LOG_ERR, "Somebody is trying to run a linked script for job %s", 218 filename); 219 exit(EXIT_FAILURE); 220 } 221 if ((fflags = fcntl(fd_in, F_GETFD)) < 0) 222 perr("Error in fcntl"); 223 224 (void)fcntl(fd_in, F_SETFD, fflags & ~FD_CLOEXEC); 225 226 (void)snprintf(fmt, sizeof(fmt), 227 "#!/bin/sh\n# atrun uid=%%u gid=%%u\n# mail %%%ds %%d", 228 LOGIN_NAME_MAX); 229 if (fscanf(stream, fmt, &nuid, &ngid, mailbuf, &send_mail) != 4) { 230 syslog(LOG_ERR, "File %s is in wrong format - aborting", 231 filename); 232 exit(EXIT_FAILURE); 233 } 234 if (mailbuf[0] == '-') { 235 syslog(LOG_ERR, "illegal mail name %s in %s", mailbuf, filename); 236 exit(EXIT_FAILURE); 237 } 238 mailname = mailbuf; 239 if (nuid != uid) { 240 syslog(LOG_ERR, "Job %s - userid %u does not match file uid %u", 241 filename, nuid, uid); 242 exit(EXIT_FAILURE); 243 } 244 if (ngid != gid) { 245 syslog(LOG_ERR, "Job %s - groupid %u does not match file gid %u", 246 filename, ngid, gid); 247 exit(EXIT_FAILURE); 248 } 249 (void)fclose(stream); 250 251 PRIV_START 252 253 if (chdir(_PATH_ATSPOOL) < 0) 254 perr2("Cannot chdir to ", _PATH_ATSPOOL); 255 256 /* 257 * Create a file to hold the output of the job we are about to 258 * run. Write the mail header. 259 */ 260 261 if ((fd_out = open(filename, 262 O_WRONLY | O_CREAT | O_EXCL, S_IWUSR | S_IRUSR)) < 0) 263 perr("Cannot create output file"); 264 265 PRIV_END 266 267 write_string(fd_out, "To: "); 268 write_string(fd_out, mailname); 269 write_string(fd_out, "\nSubject: Output from your job "); 270 write_string(fd_out, filename); 271 write_string(fd_out, "\n\n"); 272 if (fstat(fd_out, &buf) == -1) 273 perr("Error in fstat of output file descriptor"); 274 size = buf.st_size; 275 276 (void)close(STDIN_FILENO); 277 (void)close(STDOUT_FILENO); 278 (void)close(STDERR_FILENO); 279 280 pid = fork(); 281 if (pid < 0) 282 perr("Error in fork"); 283 else if (pid == 0) { 284 char *nul = NULL; 285 char **nenvp = &nul; 286 287 /* 288 * Set up things for the child; we want standard input from 289 * the input file, and standard output and error sent to 290 * our output file. 291 */ 292 if (lseek(fd_in, (off_t) 0, SEEK_SET) < 0) 293 perr("Error in lseek"); 294 295 if (dup(fd_in) != STDIN_FILENO) 296 perr("Error in I/O redirection"); 297 298 if (dup(fd_out) != STDOUT_FILENO) 299 perr("Error in I/O redirection"); 300 301 if (dup(fd_out) != STDERR_FILENO) 302 perr("Error in I/O redirection"); 303 304 (void)close(fd_in); 305 (void)close(fd_out); 306 307 PRIV_START 308 309 if (chdir(_PATH_ATJOBS) < 0) 310 perr2("Cannot chdir to ", _PATH_ATJOBS); 311 312 queue = *filename; 313 314 if (queue > 'b') 315 nice(queue - 'b'); 316 317 become_user(pentry, uid); 318 319 if (execle("/bin/sh", "sh", (char *)NULL, nenvp) != 0) 320 perr("Exec failed for /bin/sh"); 321 322 PRIV_END 323 } 324 /* We're the parent. Let's wait. */ 325 (void)close(fd_in); 326 (void)close(fd_out); 327 waitpid(pid, (int *)NULL, 0); 328 329 /* 330 * Send mail. Unlink the output file first, so it is deleted 331 * after the run. 332 */ 333 PRIV_START 334 335 if (stat(filename, &buf) == -1) 336 perr("Error in stat of output file"); 337 if (open(filename, O_RDONLY) != STDIN_FILENO) 338 perr("Open of jobfile failed"); 339 340 (void)unlink(filename); 341 342 PRIV_END 343 344 if ((buf.st_size != size) || send_mail) { 345 /* Fork off a child for sending mail */ 346 347 PRIV_START 348 349 become_user(pentry, uid); 350 351 execl(_PATH_SENDMAIL, "sendmail", "-F", "Atrun Service", 352 "-odi", "-oem", "-t", (char *) NULL); 353 perr("Exec failed for mail command"); 354 355 PRIV_END 356 } 357 exit(EXIT_SUCCESS); 358 } 359 360 /* Global functions */ 361 362 int 363 main(argc, argv) 364 int argc; 365 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; 393 394 /* 395 * We don't need root privileges all the time; running under uid 396 * and gid nobody is fine except for privileged operations. 397 */ 398 RELINQUISH_PRIVS_ROOT(NOBODY_UID, NOBODY_GID) 399 400 openlog("atrun", LOG_PID, LOG_CRON); 401 402 opterr = 0; 403 errno = 0; 404 while ((c = getopt(argc, argv, "dl:")) != -1) { 405 switch (c) { 406 case 'l': 407 if (sscanf(optarg, "%lf", &load_avg) != 1) 408 perr("garbled option -l"); 409 if (load_avg <= 0.) 410 load_avg = ATRUN_MAXLOAD; 411 break; 412 413 case 'd': 414 debug++; 415 break; 416 417 case '?': 418 perr("unknown option"); 419 break; 420 421 default: 422 perr("idiotic option - aborted"); 423 break; 424 } 425 } 426 427 namep = argv[0]; 428 429 PRIV_START 430 431 if (chdir(_PATH_ATJOBS) != 0) 432 perr2("Cannot change to ", _PATH_ATJOBS); 433 434 435 /* 436 * Main loop. Open spool directory for reading and look over all 437 * the files in there. If the filename indicates that the job 438 * should be run and the x bit is set, fork off a child which sets 439 * its user and group id to that of the files and exec a /bin/sh 440 * which executes the shell script. Unlink older files if they 441 * should no longer be run. For deletion, their r bit has to be 442 * turned on. 443 * 444 * Also, pick the oldest batch job to run, at most one per 445 * invocation of atrun. 446 */ 447 if ((spool = opendir(".")) == NULL) 448 perr2("Cannot read ", _PATH_ATJOBS); 449 450 PRIV_END 451 452 now = time(NULL); 453 run_batch = 0; 454 batch_uid = (uid_t) -1; 455 batch_gid = (gid_t) -1; 456 457 while ((dirent = readdir(spool)) != NULL) { 458 PRIV_START 459 460 if (stat(dirent->d_name, &buf) != 0) 461 perr2("Cannot stat in ", _PATH_ATJOBS); 462 463 PRIV_END 464 465 /* We don't want directories */ 466 if (!S_ISREG(buf.st_mode)) 467 continue; 468 469 if (sscanf(dirent->d_name, "%c%5x%8lx", &queue, &jobno, &ctm) != 3) 470 continue; 471 472 run_time = (time_t) ctm * 60; 473 474 if ((S_IXUSR & buf.st_mode) && (run_time <= now)) { 475 if (isupper(queue) && 476 (strcmp(batch_name, dirent->d_name) > 0)) { 477 run_batch = 1; 478 (void)strncpy(batch_name, dirent->d_name, 479 sizeof(batch_name)); 480 batch_uid = buf.st_uid; 481 batch_gid = buf.st_gid; 482 } 483 484 /* The file is executable and old enough */ 485 if (islower(queue)) 486 run_file(dirent->d_name, buf.st_uid, buf.st_gid); 487 } 488 489 /* Delete older files */ 490 if ((run_time < now) && !(S_IXUSR & buf.st_mode) && 491 (S_IRUSR & buf.st_mode)) { 492 PRIV_START 493 494 (void)unlink(dirent->d_name); 495 496 PRIV_END 497 } 498 } 499 500 /* Run the single batch file, if any */ 501 if (run_batch && ((getloadavg(&la, 1) == 1) && la < load_avg)) 502 run_file(batch_name, batch_uid, batch_gid); 503 504 closelog(); 505 exit(EXIT_SUCCESS); 506 } 507