1 /* 2 * atrun.c - run jobs queued by at; run with root privileges. 3 * Copyright (C) 1993, 1994 Thomas Koenig 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. The name of the author(s) may not be used to endorse or promote 11 * products derived from this software without specific prior written 12 * permission. 13 * 14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR(S) ``AS IS'' AND ANY EXPRESS OR 15 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 16 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 17 * IN NO EVENT SHALL THE AUTHOR(S) BE LIABLE FOR ANY DIRECT, INDIRECT, 18 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 19 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 20 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 21 * THEORY OF LIABILITY, WETHER IN CONTRACT, STRICT LIABILITY, OR TORT 22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 23 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 24 */ 25 26 #ifndef lint 27 static const char rcsid[] = 28 "$FreeBSD$"; 29 #endif /* not lint */ 30 31 /* System Headers */ 32 33 #include <sys/fcntl.h> 34 #include <sys/types.h> 35 #include <sys/stat.h> 36 #include <sys/wait.h> 37 #include <sys/param.h> 38 #include <ctype.h> 39 #include <dirent.h> 40 #include <err.h> 41 #include <grp.h> 42 #include <pwd.h> 43 #include <signal.h> 44 #include <stddef.h> 45 #include <stdio.h> 46 #include <stdlib.h> 47 #include <string.h> 48 #include <syslog.h> 49 #include <time.h> 50 #include <unistd.h> 51 #include <utmp.h> 52 #ifdef __FreeBSD__ 53 #include <paths.h> 54 #else 55 #include <getopt.h> 56 #endif 57 58 #if (MAXLOGNAME-1) > UT_NAMESIZE 59 #define LOGNAMESIZE UT_NAMESIZE 60 #else 61 #define LOGNAMESIZE (MAXLOGNAME-1) 62 #endif 63 64 /* Local headers */ 65 66 #include "gloadavg.h" 67 #define MAIN 68 #include "privs.h" 69 70 /* Macros */ 71 72 #ifndef ATJOB_DIR 73 #define ATJOB_DIR "/usr/spool/atjobs/" 74 #endif 75 76 #ifndef ATSPOOL_DIR 77 #define ATSPOOL_DIR "/usr/spool/atspool/" 78 #endif 79 80 #ifndef LOADAVG_MX 81 #define LOADAVG_MX 1.5 82 #endif 83 84 /* File scope variables */ 85 86 static debug = 0; 87 88 void perr(const char *a); 89 static void usage __P((void)); 90 91 /* Local functions */ 92 static int 93 write_string(int fd, const char* a) 94 { 95 return write(fd, a, strlen(a)); 96 } 97 98 #undef DEBUG_FORK 99 #ifdef DEBUG_FORK 100 static pid_t 101 myfork() 102 { 103 pid_t res; 104 res = fork(); 105 if (res == 0) 106 kill(getpid(),SIGSTOP); 107 return res; 108 } 109 110 #define fork myfork 111 #endif 112 113 static void 114 run_file(const char *filename, uid_t uid, gid_t gid) 115 { 116 /* Run a file by by spawning off a process which redirects I/O, 117 * spawns a subshell, then waits for it to complete and sends 118 * mail to the user. 119 */ 120 pid_t pid; 121 int fd_out, fd_in; 122 int queue; 123 char mailbuf[LOGNAMESIZE + 1], fmt[49]; 124 char *mailname = NULL; 125 FILE *stream; 126 int send_mail = 0; 127 struct stat buf, lbuf; 128 off_t size; 129 struct passwd *pentry; 130 int fflags; 131 long nuid; 132 long ngid; 133 134 135 PRIV_START 136 137 if (chmod(filename, S_IRUSR) != 0) 138 { 139 perr("cannot change file permissions"); 140 } 141 142 PRIV_END 143 144 pid = fork(); 145 if (pid == -1) 146 perr("cannot fork"); 147 148 else if (pid != 0) 149 return; 150 151 /* Let's see who we mail to. Hopefully, we can read it from 152 * the command file; if not, send it to the owner, or, failing that, 153 * to root. 154 */ 155 156 pentry = getpwuid(uid); 157 if (pentry == NULL) 158 { 159 syslog(LOG_ERR,"Userid %lu not found - aborting job %s", 160 (unsigned long) uid, filename); 161 exit(EXIT_FAILURE); 162 } 163 PRIV_START 164 165 stream=fopen(filename, "r"); 166 167 PRIV_END 168 169 #ifdef __FreeBSD__ 170 if (pentry->pw_expire && time(NULL) >= pentry->pw_expire) 171 { 172 syslog(LOG_ERR, "Userid %lu is expired - aborting job %s", 173 (unsigned long) uid, filename); 174 exit(EXIT_FAILURE); 175 } 176 #endif 177 178 if (stream == NULL) 179 perr("cannot open input file"); 180 181 if ((fd_in = dup(fileno(stream))) <0) 182 perr("error duplicating input file descriptor"); 183 184 if (fstat(fd_in, &buf) == -1) 185 perr("error in fstat of input file descriptor"); 186 187 if (lstat(filename, &lbuf) == -1) 188 perr("error in fstat of input file"); 189 190 if (S_ISLNK(lbuf.st_mode)) { 191 syslog(LOG_ERR,"Symbolic link encountered in job %s - aborting", 192 filename); 193 exit(EXIT_FAILURE); 194 } 195 if ((lbuf.st_dev != buf.st_dev) || (lbuf.st_ino != buf.st_ino) || 196 (lbuf.st_uid != buf.st_uid) || (lbuf.st_gid != buf.st_gid) || 197 (lbuf.st_size!=buf.st_size)) { 198 syslog(LOG_ERR,"Somebody changed files from under us for job %s - " 199 "aborting",filename); 200 exit(EXIT_FAILURE); 201 } 202 if (buf.st_nlink > 1) { 203 syslog(LOG_ERR,"Someboy is trying to run a linked script for job %s", 204 filename); 205 exit(EXIT_FAILURE); 206 } 207 if ((fflags = fcntl(fd_in, F_GETFD)) <0) 208 perr("error in fcntl"); 209 210 fcntl(fd_in, F_SETFD, fflags & ~FD_CLOEXEC); 211 212 snprintf(fmt, 49, "#!/bin/sh\n# atrun uid=%%ld gid=%%ld\n# mail %%%ds %%d", 213 LOGNAMESIZE); 214 if (fscanf(stream, fmt, &nuid, &ngid, mailbuf, &send_mail) != 4) { 215 syslog(LOG_ERR,"File %s is in wrong format - aborting", filename); 216 exit(EXIT_FAILURE); 217 } 218 if (mailbuf[0] == '-') { 219 syslog(LOG_ERR,"illegal mail name %s in %s",mailbuf,filename); 220 exit(EXIT_FAILURE); 221 } 222 mailname = mailbuf; 223 if (nuid != uid) { 224 syslog(LOG_ERR,"Job %s - userid %ld does not match file uid %lu", 225 filename, nuid, (unsigned long)uid); 226 exit(EXIT_FAILURE); 227 } 228 if (ngid != gid) { 229 syslog(LOG_ERR,"Job %s - groupid %ld does not match file gid %lu", 230 filename, ngid, (unsigned long)gid); 231 exit(EXIT_FAILURE); 232 } 233 fclose(stream); 234 if (chdir(ATSPOOL_DIR) < 0) 235 perr("cannot chdir to " ATSPOOL_DIR); 236 237 /* Create a file to hold the output of the job we are about to run. 238 * Write the mail header. 239 */ 240 if((fd_out=open(filename, 241 O_WRONLY | O_CREAT | O_EXCL, S_IWUSR | S_IRUSR)) < 0) 242 perr("cannot create output file"); 243 244 write_string(fd_out, "Subject: Output from your job "); 245 write_string(fd_out, filename); 246 write_string(fd_out, "\n\n"); 247 fstat(fd_out, &buf); 248 size = buf.st_size; 249 250 close(STDIN_FILENO); 251 close(STDOUT_FILENO); 252 close(STDERR_FILENO); 253 254 pid = fork(); 255 if (pid < 0) 256 perr("error in fork"); 257 258 else if (pid == 0) 259 { 260 char *nul = NULL; 261 char **nenvp = &nul; 262 263 /* Set up things for the child; we want standard input from the input file, 264 * and standard output and error sent to our output file. 265 */ 266 267 if (lseek(fd_in, (off_t) 0, SEEK_SET) < 0) 268 perr("error in lseek"); 269 270 if (dup(fd_in) != STDIN_FILENO) 271 perr("error in I/O redirection"); 272 273 if (dup(fd_out) != STDOUT_FILENO) 274 perr("error in I/O redirection"); 275 276 if (dup(fd_out) != STDERR_FILENO) 277 perr("error in I/O redirection"); 278 279 close(fd_in); 280 close(fd_out); 281 if (chdir(ATJOB_DIR) < 0) 282 perr("cannot chdir to " ATJOB_DIR); 283 284 queue = *filename; 285 286 PRIV_START 287 288 nice(tolower(queue) - 'a'); 289 290 if (initgroups(pentry->pw_name,pentry->pw_gid)) 291 perr("cannot delete saved userids"); 292 293 if (setgid(gid) < 0 || setegid(pentry->pw_gid) < 0) 294 perr("cannot change group"); 295 296 if (setlogin(pentry->pw_name)) 297 perr("cannot set login name"); 298 299 if (setuid(uid) < 0 || seteuid(uid) < 0) 300 perr("cannot set user id"); 301 302 if (chdir(pentry->pw_dir)) 303 chdir("/"); 304 305 if(execle("/bin/sh","sh",(char *) NULL, nenvp) != 0) 306 perr("exec failed for /bin/sh"); 307 308 PRIV_END 309 } 310 /* We're the parent. Let's wait. 311 */ 312 close(fd_in); 313 close(fd_out); 314 waitpid(pid, (int *) NULL, 0); 315 316 /* Send mail. Unlink the output file first, so it is deleted after 317 * the run. 318 */ 319 stat(filename, &buf); 320 if (open(filename, O_RDONLY) != STDIN_FILENO) 321 perr("open of jobfile failed"); 322 323 unlink(filename); 324 if ((buf.st_size != size) || send_mail) 325 { 326 PRIV_START 327 328 if (initgroups(pentry->pw_name,pentry->pw_gid)) 329 perr("cannot delete saved userids"); 330 331 if (setgid(gid) < 0 || setegid(pentry->pw_gid) < 0) 332 perr("cannot change group"); 333 334 if (setlogin(pentry->pw_name)) 335 perr("cannot set login name"); 336 337 if (setuid(uid) < 0 || seteuid(uid) < 0) 338 perr("cannot set user id"); 339 340 if (chdir(pentry->pw_dir)) 341 chdir("/"); 342 343 #ifdef __FreeBSD__ 344 execl(_PATH_SENDMAIL, "sendmail", "-F", "Atrun Service", 345 "-odi", "-oem", 346 mailname, (char *) NULL); 347 #else 348 execl(MAIL_CMD, MAIL_CMD, mailname, (char *) NULL); 349 #endif 350 perr("exec failed for mail command"); 351 352 PRIV_END 353 } 354 exit(EXIT_SUCCESS); 355 } 356 357 /* Global functions */ 358 359 /* Needed in gloadavg.c */ 360 void 361 perr(const char *a) 362 { 363 if (debug) 364 { 365 warn("%s", a); 366 } 367 else 368 syslog(LOG_ERR, "%s: %m", a); 369 370 exit(EXIT_FAILURE); 371 } 372 373 int 374 main(int argc, char *argv[]) 375 { 376 /* Browse through ATJOB_DIR, checking all the jobfiles wether they should 377 * be executed and or deleted. The queue is coded into the first byte of 378 * the job filename, the date (in minutes since Eon) as a hex number in the 379 * following eight bytes, followed by a dot and a serial number. A file 380 * which has not been executed yet is denoted by its execute - bit set. 381 * For those files which are to be executed, run_file() is called, which forks 382 * off a child which takes care of I/O redirection, forks off another child 383 * for execution and yet another one, optionally, for sending mail. 384 * Files which already have run are removed during the next invocation. 385 */ 386 DIR *spool; 387 struct dirent *dirent; 388 struct stat buf; 389 unsigned long ctm; 390 unsigned long 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 load_avg = LOADAVG_MX; 399 400 /* We don't need root privileges all the time; running under uid and gid daemon 401 * is fine. 402 */ 403 404 RELINQUISH_PRIVS_ROOT(DAEMON_UID, DAEMON_GID) 405 406 openlog("atrun", LOG_PID, LOG_CRON); 407 408 opterr = 0; 409 while((c=getopt(argc, argv, "dl:"))!= -1) 410 { 411 switch (c) 412 { 413 case 'l': 414 if (sscanf(optarg, "%lf", &load_avg) != 1) 415 perr("garbled option -l"); 416 if (load_avg <= 0.) 417 load_avg = LOADAVG_MX; 418 break; 419 420 case 'd': 421 debug ++; 422 break; 423 424 case '?': 425 default: 426 usage(); 427 } 428 } 429 430 if (chdir(ATJOB_DIR) != 0) 431 perr("cannot change to " ATJOB_DIR); 432 433 /* Main loop. Open spool directory for reading and look over all the 434 * files in there. If the filename indicates that the job should be run 435 * and the x bit is set, fork off a child which sets its user and group 436 * id to that of the files and exec a /bin/sh which executes the shell 437 * script. Unlink older files if they should no longer be run. For 438 * deletion, their r bit has to be turned on. 439 * 440 * Also, pick the oldest batch job to run, at most one per invocation of 441 * atrun. 442 */ 443 if ((spool = opendir(".")) == NULL) 444 perr("cannot read " ATJOB_DIR); 445 446 now = time(NULL); 447 run_batch = 0; 448 batch_uid = (uid_t) -1; 449 batch_gid = (gid_t) -1; 450 451 while ((dirent = readdir(spool)) != NULL) { 452 if (stat(dirent->d_name,&buf) != 0) 453 perr("cannot stat in " ATJOB_DIR); 454 455 /* We don't want directories 456 */ 457 if (!S_ISREG(buf.st_mode)) 458 continue; 459 460 if (sscanf(dirent->d_name,"%c%5lx%8lx",&queue,&jobno,&ctm) != 3) 461 continue; 462 463 run_time = (time_t) ctm*60; 464 465 if ((S_IXUSR & buf.st_mode) && (run_time <=now)) { 466 if (isupper(queue) && (strcmp(batch_name,dirent->d_name) > 0)) { 467 run_batch = 1; 468 strncpy(batch_name, dirent->d_name, sizeof(batch_name)); 469 batch_uid = buf.st_uid; 470 batch_gid = buf.st_gid; 471 } 472 473 /* The file is executable and old enough 474 */ 475 if (islower(queue)) 476 run_file(dirent->d_name, buf.st_uid, buf.st_gid); 477 } 478 /* Delete older files 479 */ 480 if ((run_time < now) && !(S_IXUSR & buf.st_mode) && (S_IRUSR & buf.st_mode)) 481 unlink(dirent->d_name); 482 } 483 /* run the single batch file, if any 484 */ 485 if (run_batch && (gloadavg() < load_avg)) 486 run_file(batch_name, batch_uid, batch_gid); 487 488 closelog(); 489 exit(EXIT_SUCCESS); 490 } 491 492 static void 493 usage() 494 { 495 if (debug) 496 fprintf(stderr, "usage: atrun [-l load_avg] [-d]\n"); 497 else 498 syslog(LOG_ERR, "usage: atrun [-l load_avg] [-d]"); 499 500 exit(EXIT_FAILURE); 501 } 502