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 /* System Headers */ 27 28 #include <sys/fcntl.h> 29 #include <sys/types.h> 30 #include <sys/stat.h> 31 #include <sys/wait.h> 32 #include <ctype.h> 33 #include <dirent.h> 34 #include <errno.h> 35 #include <pwd.h> 36 #include <grp.h> 37 #include <signal.h> 38 #include <stddef.h> 39 #include <stdio.h> 40 #include <stdlib.h> 41 #include <string.h> 42 #include <time.h> 43 #include <unistd.h> 44 #include <syslog.h> 45 #ifdef __FreeBSD__ 46 #include <paths.h> 47 #else 48 #include <getopt.h> 49 #endif 50 51 /* Local headers */ 52 53 #include "gloadavg.h" 54 #define MAIN 55 #include "privs.h" 56 57 /* Macros */ 58 59 #ifndef ATJOB_DIR 60 #define ATJOB_DIR "/usr/spool/atjobs/" 61 #endif 62 63 #ifndef ATSPOOL_DIR 64 #define ATSPOOL_DIR "/usr/spool/atspool/" 65 #endif 66 67 #ifndef LOADAVG_MX 68 #define LOADAVG_MX 1.5 69 #endif 70 71 /* File scope variables */ 72 73 static char *namep; 74 static char rcsid[] = "$Id: atrun.c,v 1.5 1995/08/21 12:34:17 ache Exp $"; 75 static debug = 0; 76 77 void perr(const char *a); 78 79 /* Local functions */ 80 static int 81 write_string(int fd, const char* a) 82 { 83 return write(fd, a, strlen(a)); 84 } 85 86 #undef DEBUG_FORK 87 #ifdef DEBUG_FORK 88 static pid_t 89 myfork() 90 { 91 pid_t res; 92 res = fork(); 93 if (res == 0) 94 kill(getpid(),SIGSTOP); 95 return res; 96 } 97 98 #define fork myfork 99 #endif 100 101 static void 102 run_file(const char *filename, uid_t uid, gid_t gid) 103 { 104 /* Run a file by by spawning off a process which redirects I/O, 105 * spawns a subshell, then waits for it to complete and sends 106 * mail to the user. 107 */ 108 pid_t pid; 109 int fd_out, fd_in; 110 int queue; 111 char mailbuf[9]; 112 char *mailname = NULL; 113 FILE *stream; 114 int send_mail = 0; 115 struct stat buf, lbuf; 116 off_t size; 117 struct passwd *pentry; 118 int fflags; 119 long nuid; 120 long ngid; 121 122 123 PRIV_START 124 125 if (chmod(filename, S_IRUSR) != 0) 126 { 127 perr("Cannot change file permissions"); 128 } 129 130 PRIV_END 131 132 pid = fork(); 133 if (pid == -1) 134 perr("Cannot fork"); 135 136 else if (pid != 0) 137 return; 138 139 /* Let's see who we mail to. Hopefully, we can read it from 140 * the command file; if not, send it to the owner, or, failing that, 141 * to root. 142 */ 143 144 pentry = getpwuid(uid); 145 if (pentry == NULL) 146 { 147 syslog(LOG_ERR,"Userid %lu not found - aborting job %s", 148 (unsigned long) uid, filename); 149 exit(EXIT_FAILURE); 150 } 151 PRIV_START 152 153 stream=fopen(filename, "r"); 154 155 PRIV_END 156 157 #ifdef __FreeBSD__ 158 if (pentry->pw_expire && time(NULL) >= pentry->pw_expire) 159 { 160 syslog(LOG_ERR, "Userid %lu is expired - aborting job %s", 161 (unsigned long) uid, filename); 162 exit(EXIT_FAILURE); 163 } 164 #endif 165 166 if (stream == NULL) 167 perr("Cannot open input file"); 168 169 if ((fd_in = dup(fileno(stream))) <0) 170 perr("Error duplicating input file descriptor"); 171 172 if (fstat(fd_in, &buf) == -1) 173 perr("Error in fstat of input file descriptor"); 174 175 if (lstat(filename, &lbuf) == -1) 176 perr("Error in fstat of input file"); 177 178 if (S_ISLNK(lbuf.st_mode)) { 179 syslog(LOG_ERR,"Symbolic link encountered in job %s - aborting", 180 filename); 181 exit(EXIT_FAILURE); 182 } 183 if ((lbuf.st_dev != buf.st_dev) || (lbuf.st_ino != buf.st_ino) || 184 (lbuf.st_uid != buf.st_uid) || (lbuf.st_gid != buf.st_gid) || 185 (lbuf.st_size!=buf.st_size)) { 186 syslog(LOG_ERR,"Somebody changed files from under us for job %s - " 187 "aborting",filename); 188 exit(EXIT_FAILURE); 189 } 190 if (buf.st_nlink > 1) { 191 syslog(LOG_ERR,"Someboy is trying to run a linked script for job %s", 192 filename); 193 exit(EXIT_FAILURE); 194 } 195 if ((fflags = fcntl(fd_in, F_GETFD)) <0) 196 perr("Error in fcntl"); 197 198 fcntl(fd_in, F_SETFD, fflags & ~FD_CLOEXEC); 199 200 if (fscanf(stream, "#!/bin/sh\n# atrun uid=%ld gid=%ld\n# mail %8s %d", 201 &nuid, &ngid, mailbuf, &send_mail) != 4) 202 { 203 syslog(LOG_ERR,"File %s is in wrong format - aborting", 204 filename); 205 exit(EXIT_FAILURE); 206 } 207 if (mailbuf[0] == '-') { 208 syslog(LOG_ERR,"illegal mail name %s in %s",mailbuf,filename); 209 exit(EXIT_FAILURE); 210 } 211 mailname = mailbuf; 212 if (nuid != uid) { 213 syslog(LOG_ERR,"Job %s - userid %d does not match file uid %d", 214 filename, nuid, uid); 215 exit(EXIT_FAILURE); 216 } 217 if (ngid != gid) { 218 syslog(LOG_ERR,"Job %s - groupid %d does not match file gid %d", 219 filename, ngid, gid); 220 exit(EXIT_FAILURE); 221 } 222 fclose(stream); 223 if (chdir(ATSPOOL_DIR) < 0) 224 perr("Cannot chdir to " ATSPOOL_DIR); 225 226 /* Create a file to hold the output of the job we are about to run. 227 * Write the mail header. 228 */ 229 if((fd_out=open(filename, 230 O_WRONLY | O_CREAT | O_EXCL, S_IWUSR | S_IRUSR)) < 0) 231 perr("Cannot create output file"); 232 233 write_string(fd_out, "Subject: Output from your job "); 234 write_string(fd_out, filename); 235 write_string(fd_out, "\n\n"); 236 fstat(fd_out, &buf); 237 size = buf.st_size; 238 239 close(STDIN_FILENO); 240 close(STDOUT_FILENO); 241 close(STDERR_FILENO); 242 243 pid = fork(); 244 if (pid < 0) 245 perr("Error in fork"); 246 247 else if (pid == 0) 248 { 249 char *nul = NULL; 250 char **nenvp = &nul; 251 252 /* Set up things for the child; we want standard input from the input file, 253 * and standard output and error sent to our output file. 254 */ 255 256 if (lseek(fd_in, (off_t) 0, SEEK_SET) < 0) 257 perr("Error in lseek"); 258 259 if (dup(fd_in) != STDIN_FILENO) 260 perr("Error in I/O redirection"); 261 262 if (dup(fd_out) != STDOUT_FILENO) 263 perr("Error in I/O redirection"); 264 265 if (dup(fd_out) != STDERR_FILENO) 266 perr("Error in I/O redirection"); 267 268 close(fd_in); 269 close(fd_out); 270 if (chdir(ATJOB_DIR) < 0) 271 perr("Cannot chdir to " ATJOB_DIR); 272 273 queue = *filename; 274 275 PRIV_START 276 277 nice(tolower(queue) - 'a'); 278 279 if (chdir(pentry->pw_dir)) 280 chdir("/"); 281 282 if (initgroups(pentry->pw_name,pentry->pw_gid)) 283 perr("Cannot delete saved userids"); 284 285 if (setgid(gid) < 0) 286 perr("Cannot change group"); 287 288 if (setuid(uid) < 0) 289 perr("Cannot set user id"); 290 291 if(execle("/bin/sh","sh",(char *) NULL, nenvp) != 0) 292 perr("Exec failed for /bin/sh"); 293 294 PRIV_END 295 } 296 /* We're the parent. Let's wait. 297 */ 298 close(fd_in); 299 close(fd_out); 300 waitpid(pid, (int *) NULL, 0); 301 302 /* Send mail. Unlink the output file first, so it is deleted after 303 * the run. 304 */ 305 stat(filename, &buf); 306 if (open(filename, O_RDONLY) != STDIN_FILENO) 307 perr("Open of jobfile failed"); 308 309 unlink(filename); 310 if ((buf.st_size != size) || send_mail) 311 { 312 PRIV_START 313 314 if (chdir(pentry->pw_dir)) 315 chdir("/"); 316 317 if (initgroups(pentry->pw_name,pentry->pw_gid)) 318 perr("Cannot delete saved userids"); 319 320 if (setgid(gid) < 0) 321 perr("Cannot change group"); 322 323 if (setuid(uid) < 0) 324 perr("Cannot set user id"); 325 326 #ifdef __FreeBSD__ 327 execl(_PATH_SENDMAIL, "sendmail", "-F", "Atrun Service", 328 "-odi", "-oem", 329 mailname, (char *) NULL); 330 #else 331 execl(MAIL_CMD, MAIL_CMD, mailname, (char *) NULL); 332 #endif 333 perr("Exec failed for mail command"); 334 335 PRIV_END 336 } 337 exit(EXIT_SUCCESS); 338 } 339 340 /* Global functions */ 341 342 /* Needed in gloadavg.c */ 343 void 344 perr(const char *a) 345 { 346 if (debug) 347 { 348 perror(a); 349 } 350 else 351 syslog(LOG_ERR, "%s: %m", a); 352 353 exit(EXIT_FAILURE); 354 } 355 356 int 357 main(int argc, char *argv[]) 358 { 359 /* Browse through ATJOB_DIR, checking all the jobfiles wether they should 360 * be executed and or deleted. The queue is coded into the first byte of 361 * the job filename, the date (in minutes since Eon) as a hex number in the 362 * following eight bytes, followed by a dot and a serial number. A file 363 * which has not been executed yet is denoted by its execute - bit set. 364 * For those files which are to be executed, run_file() is called, which forks 365 * off a child which takes care of I/O redirection, forks off another child 366 * for execution and yet another one, optionally, for sending mail. 367 * Files which already have run are removed during the next invocation. 368 */ 369 DIR *spool; 370 struct dirent *dirent; 371 struct stat buf; 372 unsigned long ctm; 373 unsigned long jobno; 374 char queue; 375 time_t now, run_time; 376 char batch_name[] = "Z2345678901234"; 377 uid_t batch_uid; 378 gid_t batch_gid; 379 int c; 380 int run_batch; 381 double load_avg = LOADAVG_MX; 382 383 /* We don't need root privileges all the time; running under uid and gid daemon 384 * is fine. 385 */ 386 387 RELINQUISH_PRIVS_ROOT(DAEMON_UID, DAEMON_GID) 388 389 openlog("atrun", LOG_PID, LOG_CRON); 390 391 opterr = 0; 392 errno = 0; 393 while((c=getopt(argc, argv, "dl:"))!= EOF) 394 { 395 switch (c) 396 { 397 case 'l': 398 if (sscanf(optarg, "%lf", &load_avg) != 1) 399 perr("garbled option -l"); 400 if (load_avg <= 0.) 401 load_avg = LOADAVG_MX; 402 break; 403 404 case 'd': 405 debug ++; 406 break; 407 408 case '?': 409 perr("unknown option"); 410 break; 411 412 default: 413 perr("idiotic option - aborted"); 414 break; 415 } 416 } 417 418 namep = argv[0]; 419 if (chdir(ATJOB_DIR) != 0) 420 perr("Cannot change to " ATJOB_DIR); 421 422 /* Main loop. Open spool directory for reading and look over all the 423 * files in there. If the filename indicates that the job should be run 424 * and the x bit is set, fork off a child which sets its user and group 425 * id to that of the files and exec a /bin/sh which executes the shell 426 * script. Unlink older files if they should no longer be run. For 427 * deletion, their r bit has to be turned on. 428 * 429 * Also, pick the oldest batch job to run, at most one per invocation of 430 * atrun. 431 */ 432 if ((spool = opendir(".")) == NULL) 433 perr("Cannot read " ATJOB_DIR); 434 435 now = time(NULL); 436 run_batch = 0; 437 batch_uid = (uid_t) -1; 438 batch_gid = (gid_t) -1; 439 440 while ((dirent = readdir(spool)) != NULL) { 441 if (stat(dirent->d_name,&buf) != 0) 442 perr("Cannot stat in " ATJOB_DIR); 443 444 /* We don't want directories 445 */ 446 if (!S_ISREG(buf.st_mode)) 447 continue; 448 449 if (sscanf(dirent->d_name,"%c%5lx%8lx",&queue,&jobno,&ctm) != 3) 450 continue; 451 452 run_time = (time_t) ctm*60; 453 454 if ((S_IXUSR & buf.st_mode) && (run_time <=now)) { 455 if (isupper(queue) && (strcmp(batch_name,dirent->d_name) > 0)) { 456 run_batch = 1; 457 strncpy(batch_name, dirent->d_name, sizeof(batch_name)); 458 batch_uid = buf.st_uid; 459 batch_gid = buf.st_gid; 460 } 461 462 /* The file is executable and old enough 463 */ 464 if (islower(queue)) 465 run_file(dirent->d_name, buf.st_uid, buf.st_gid); 466 } 467 /* Delete older files 468 */ 469 if ((run_time < now) && !(S_IXUSR & buf.st_mode) && (S_IRUSR & buf.st_mode)) 470 unlink(dirent->d_name); 471 } 472 /* run the single batch file, if any 473 */ 474 if (run_batch && (gloadavg() < load_avg)) 475 run_file(batch_name, batch_uid, batch_gid); 476 477 closelog(); 478 exit(EXIT_SUCCESS); 479 } 480