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, sizeof(fmt), 213 "#!/bin/sh\n# atrun uid=%%ld gid=%%ld\n# mail %%%ds %%d", 214 LOGNAMESIZE); 215 if (fscanf(stream, fmt, &nuid, &ngid, mailbuf, &send_mail) != 4) { 216 syslog(LOG_ERR,"File %s is in wrong format - aborting", filename); 217 exit(EXIT_FAILURE); 218 } 219 if (mailbuf[0] == '-') { 220 syslog(LOG_ERR,"illegal mail name %s in %s",mailbuf,filename); 221 exit(EXIT_FAILURE); 222 } 223 mailname = mailbuf; 224 if (nuid != uid) { 225 syslog(LOG_ERR,"Job %s - userid %ld does not match file uid %lu", 226 filename, nuid, (unsigned long)uid); 227 exit(EXIT_FAILURE); 228 } 229 if (ngid != gid) { 230 syslog(LOG_ERR,"Job %s - groupid %ld does not match file gid %lu", 231 filename, ngid, (unsigned long)gid); 232 exit(EXIT_FAILURE); 233 } 234 fclose(stream); 235 if (chdir(ATSPOOL_DIR) < 0) 236 perr("cannot chdir to " ATSPOOL_DIR); 237 238 /* Create a file to hold the output of the job we are about to run. 239 * Write the mail header. 240 */ 241 if((fd_out=open(filename, 242 O_WRONLY | O_CREAT | O_EXCL, S_IWUSR | S_IRUSR)) < 0) 243 perr("cannot create output file"); 244 245 write_string(fd_out, "Subject: Output from your job "); 246 write_string(fd_out, filename); 247 write_string(fd_out, "\n\n"); 248 fstat(fd_out, &buf); 249 size = buf.st_size; 250 251 close(STDIN_FILENO); 252 close(STDOUT_FILENO); 253 close(STDERR_FILENO); 254 255 pid = fork(); 256 if (pid < 0) 257 perr("error in fork"); 258 259 else if (pid == 0) 260 { 261 char *nul = NULL; 262 char **nenvp = &nul; 263 264 /* Set up things for the child; we want standard input from the input file, 265 * and standard output and error sent to our output file. 266 */ 267 268 if (lseek(fd_in, (off_t) 0, SEEK_SET) < 0) 269 perr("error in lseek"); 270 271 if (dup(fd_in) != STDIN_FILENO) 272 perr("error in I/O redirection"); 273 274 if (dup(fd_out) != STDOUT_FILENO) 275 perr("error in I/O redirection"); 276 277 if (dup(fd_out) != STDERR_FILENO) 278 perr("error in I/O redirection"); 279 280 close(fd_in); 281 close(fd_out); 282 if (chdir(ATJOB_DIR) < 0) 283 perr("cannot chdir to " ATJOB_DIR); 284 285 queue = *filename; 286 287 PRIV_START 288 289 nice(tolower(queue) - 'a'); 290 291 if (initgroups(pentry->pw_name,pentry->pw_gid)) 292 perr("cannot delete saved userids"); 293 294 if (setgid(gid) < 0 || setegid(pentry->pw_gid) < 0) 295 perr("cannot change group"); 296 297 if (setlogin(pentry->pw_name)) 298 perr("cannot set login name"); 299 300 if (setuid(uid) < 0 || seteuid(uid) < 0) 301 perr("cannot set user id"); 302 303 if (chdir(pentry->pw_dir)) 304 chdir("/"); 305 306 if(execle("/bin/sh","sh",(char *) NULL, nenvp) != 0) 307 perr("exec failed for /bin/sh"); 308 309 PRIV_END 310 } 311 /* We're the parent. Let's wait. 312 */ 313 close(fd_in); 314 close(fd_out); 315 waitpid(pid, (int *) NULL, 0); 316 317 /* Send mail. Unlink the output file first, so it is deleted after 318 * the run. 319 */ 320 stat(filename, &buf); 321 if (open(filename, O_RDONLY) != STDIN_FILENO) 322 perr("open of jobfile failed"); 323 324 unlink(filename); 325 if ((buf.st_size != size) || send_mail) 326 { 327 PRIV_START 328 329 if (initgroups(pentry->pw_name,pentry->pw_gid)) 330 perr("cannot delete saved userids"); 331 332 if (setgid(gid) < 0 || setegid(pentry->pw_gid) < 0) 333 perr("cannot change group"); 334 335 if (setlogin(pentry->pw_name)) 336 perr("cannot set login name"); 337 338 if (setuid(uid) < 0 || seteuid(uid) < 0) 339 perr("cannot set user id"); 340 341 if (chdir(pentry->pw_dir)) 342 chdir("/"); 343 344 #ifdef __FreeBSD__ 345 execl(_PATH_SENDMAIL, "sendmail", "-F", "Atrun Service", 346 "-odi", "-oem", 347 mailname, (char *) NULL); 348 #else 349 execl(MAIL_CMD, MAIL_CMD, mailname, (char *) NULL); 350 #endif 351 perr("exec failed for mail command"); 352 353 PRIV_END 354 } 355 exit(EXIT_SUCCESS); 356 } 357 358 /* Global functions */ 359 360 /* Needed in gloadavg.c */ 361 void 362 perr(const char *a) 363 { 364 if (debug) 365 { 366 warn("%s", a); 367 } 368 else 369 syslog(LOG_ERR, "%s: %m", a); 370 371 exit(EXIT_FAILURE); 372 } 373 374 int 375 main(int argc, char *argv[]) 376 { 377 /* Browse through ATJOB_DIR, checking all the jobfiles wether they should 378 * be executed and or deleted. The queue is coded into the first byte of 379 * the job filename, the date (in minutes since Eon) as a hex number in the 380 * following eight bytes, followed by a dot and a serial number. A file 381 * which has not been executed yet is denoted by its execute - bit set. 382 * For those files which are to be executed, run_file() is called, which forks 383 * off a child which takes care of I/O redirection, forks off another child 384 * for execution and yet another one, optionally, for sending mail. 385 * Files which already have run are removed during the next invocation. 386 */ 387 DIR *spool; 388 struct dirent *dirent; 389 struct stat buf; 390 unsigned long ctm; 391 unsigned long jobno; 392 char queue; 393 time_t now, run_time; 394 char batch_name[] = "Z2345678901234"; 395 uid_t batch_uid; 396 gid_t batch_gid; 397 int c; 398 int run_batch; 399 double load_avg = LOADAVG_MX; 400 401 /* We don't need root privileges all the time; running under uid and gid daemon 402 * is fine. 403 */ 404 405 RELINQUISH_PRIVS_ROOT(DAEMON_UID, DAEMON_GID) 406 407 openlog("atrun", LOG_PID, LOG_CRON); 408 409 opterr = 0; 410 while((c=getopt(argc, argv, "dl:"))!= -1) 411 { 412 switch (c) 413 { 414 case 'l': 415 if (sscanf(optarg, "%lf", &load_avg) != 1) 416 perr("garbled option -l"); 417 if (load_avg <= 0.) 418 load_avg = LOADAVG_MX; 419 break; 420 421 case 'd': 422 debug ++; 423 break; 424 425 case '?': 426 default: 427 usage(); 428 } 429 } 430 431 if (chdir(ATJOB_DIR) != 0) 432 perr("cannot change to " ATJOB_DIR); 433 434 /* Main loop. Open spool directory for reading and look over all the 435 * files in there. If the filename indicates that the job should be run 436 * and the x bit is set, fork off a child which sets its user and group 437 * id to that of the files and exec a /bin/sh which executes the shell 438 * script. Unlink older files if they should no longer be run. For 439 * deletion, their r bit has to be turned on. 440 * 441 * Also, pick the oldest batch job to run, at most one per invocation of 442 * atrun. 443 */ 444 if ((spool = opendir(".")) == NULL) 445 perr("cannot read " ATJOB_DIR); 446 447 now = time(NULL); 448 run_batch = 0; 449 batch_uid = (uid_t) -1; 450 batch_gid = (gid_t) -1; 451 452 while ((dirent = readdir(spool)) != NULL) { 453 if (stat(dirent->d_name,&buf) != 0) 454 perr("cannot stat in " ATJOB_DIR); 455 456 /* We don't want directories 457 */ 458 if (!S_ISREG(buf.st_mode)) 459 continue; 460 461 if (sscanf(dirent->d_name,"%c%5lx%8lx",&queue,&jobno,&ctm) != 3) 462 continue; 463 464 run_time = (time_t) ctm*60; 465 466 if ((S_IXUSR & buf.st_mode) && (run_time <=now)) { 467 if (isupper(queue) && (strcmp(batch_name,dirent->d_name) > 0)) { 468 run_batch = 1; 469 strncpy(batch_name, dirent->d_name, sizeof(batch_name)); 470 batch_uid = buf.st_uid; 471 batch_gid = buf.st_gid; 472 } 473 474 /* The file is executable and old enough 475 */ 476 if (islower(queue)) 477 run_file(dirent->d_name, buf.st_uid, buf.st_gid); 478 } 479 /* Delete older files 480 */ 481 if ((run_time < now) && !(S_IXUSR & buf.st_mode) && (S_IRUSR & buf.st_mode)) 482 unlink(dirent->d_name); 483 } 484 /* run the single batch file, if any 485 */ 486 if (run_batch && (gloadavg() < load_avg)) 487 run_file(batch_name, batch_uid, batch_gid); 488 489 closelog(); 490 exit(EXIT_SUCCESS); 491 } 492 493 static void 494 usage() 495 { 496 if (debug) 497 fprintf(stderr, "usage: atrun [-l load_avg] [-d]\n"); 498 else 499 syslog(LOG_ERR, "usage: atrun [-l load_avg] [-d]"); 500 501 exit(EXIT_FAILURE); 502 } 503