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 <sys/param.h> 33 #include <ctype.h> 34 #include <dirent.h> 35 #include <errno.h> 36 #include <pwd.h> 37 #include <grp.h> 38 #include <signal.h> 39 #include <stddef.h> 40 #include <stdio.h> 41 #include <stdlib.h> 42 #include <string.h> 43 #include <time.h> 44 #include <unistd.h> 45 #include <syslog.h> 46 #include <utmp.h> 47 #ifdef __FreeBSD__ 48 #include <paths.h> 49 #else 50 #include <getopt.h> 51 #endif 52 53 #if (MAXLOGNAME-1) > UT_NAMESIZE 54 #define LOGNAMESIZE UT_NAMESIZE 55 #else 56 #define LOGNAMESIZE (MAXLOGNAME-1) 57 #endif 58 59 /* Local headers */ 60 61 #include "gloadavg.h" 62 #define MAIN 63 #include "privs.h" 64 65 /* Macros */ 66 67 #ifndef ATJOB_DIR 68 #define ATJOB_DIR "/usr/spool/atjobs/" 69 #endif 70 71 #ifndef ATSPOOL_DIR 72 #define ATSPOOL_DIR "/usr/spool/atspool/" 73 #endif 74 75 #ifndef LOADAVG_MX 76 #define LOADAVG_MX 1.5 77 #endif 78 79 /* File scope variables */ 80 81 static char *namep; 82 static char rcsid[] = "$Id: atrun.c,v 1.9 1997/03/28 15:48:03 imp Exp $"; 83 static debug = 0; 84 85 void perr(const char *a); 86 87 /* Local functions */ 88 static int 89 write_string(int fd, const char* a) 90 { 91 return write(fd, a, strlen(a)); 92 } 93 94 #undef DEBUG_FORK 95 #ifdef DEBUG_FORK 96 static pid_t 97 myfork() 98 { 99 pid_t res; 100 res = fork(); 101 if (res == 0) 102 kill(getpid(),SIGSTOP); 103 return res; 104 } 105 106 #define fork myfork 107 #endif 108 109 static void 110 run_file(const char *filename, uid_t uid, gid_t gid) 111 { 112 /* Run a file by by spawning off a process which redirects I/O, 113 * spawns a subshell, then waits for it to complete and sends 114 * mail to the user. 115 */ 116 pid_t pid; 117 int fd_out, fd_in; 118 int queue; 119 char mailbuf[LOGNAMESIZE + 1], fmt[49]; 120 char *mailname = NULL; 121 FILE *stream; 122 int send_mail = 0; 123 struct stat buf, lbuf; 124 off_t size; 125 struct passwd *pentry; 126 int fflags; 127 long nuid; 128 long ngid; 129 130 131 PRIV_START 132 133 if (chmod(filename, S_IRUSR) != 0) 134 { 135 perr("Cannot change file permissions"); 136 } 137 138 PRIV_END 139 140 pid = fork(); 141 if (pid == -1) 142 perr("Cannot fork"); 143 144 else if (pid != 0) 145 return; 146 147 /* Let's see who we mail to. Hopefully, we can read it from 148 * the command file; if not, send it to the owner, or, failing that, 149 * to root. 150 */ 151 152 pentry = getpwuid(uid); 153 if (pentry == NULL) 154 { 155 syslog(LOG_ERR,"Userid %lu not found - aborting job %s", 156 (unsigned long) uid, filename); 157 exit(EXIT_FAILURE); 158 } 159 PRIV_START 160 161 stream=fopen(filename, "r"); 162 163 PRIV_END 164 165 #ifdef __FreeBSD__ 166 if (pentry->pw_expire && time(NULL) >= pentry->pw_expire) 167 { 168 syslog(LOG_ERR, "Userid %lu is expired - aborting job %s", 169 (unsigned long) uid, filename); 170 exit(EXIT_FAILURE); 171 } 172 #endif 173 174 if (stream == NULL) 175 perr("Cannot open input file"); 176 177 if ((fd_in = dup(fileno(stream))) <0) 178 perr("Error duplicating input file descriptor"); 179 180 if (fstat(fd_in, &buf) == -1) 181 perr("Error in fstat of input file descriptor"); 182 183 if (lstat(filename, &lbuf) == -1) 184 perr("Error in fstat of input file"); 185 186 if (S_ISLNK(lbuf.st_mode)) { 187 syslog(LOG_ERR,"Symbolic link encountered in job %s - aborting", 188 filename); 189 exit(EXIT_FAILURE); 190 } 191 if ((lbuf.st_dev != buf.st_dev) || (lbuf.st_ino != buf.st_ino) || 192 (lbuf.st_uid != buf.st_uid) || (lbuf.st_gid != buf.st_gid) || 193 (lbuf.st_size!=buf.st_size)) { 194 syslog(LOG_ERR,"Somebody changed files from under us for job %s - " 195 "aborting",filename); 196 exit(EXIT_FAILURE); 197 } 198 if (buf.st_nlink > 1) { 199 syslog(LOG_ERR,"Someboy is trying to run a linked script for job %s", 200 filename); 201 exit(EXIT_FAILURE); 202 } 203 if ((fflags = fcntl(fd_in, F_GETFD)) <0) 204 perr("Error in fcntl"); 205 206 fcntl(fd_in, F_SETFD, fflags & ~FD_CLOEXEC); 207 208 snprintf(fmt, 49, "#!/bin/sh\n# atrun uid=%%ld gid=%%ld\n# mail %%%ds %%d", 209 LOGNAMESIZE); 210 if (fscanf(stream, fmt, &nuid, &ngid, mailbuf, &send_mail) != 4) { 211 syslog(LOG_ERR,"File %s is in wrong format - aborting", filename); 212 exit(EXIT_FAILURE); 213 } 214 if (mailbuf[0] == '-') { 215 syslog(LOG_ERR,"illegal mail name %s in %s",mailbuf,filename); 216 exit(EXIT_FAILURE); 217 } 218 mailname = mailbuf; 219 if (nuid != uid) { 220 syslog(LOG_ERR,"Job %s - userid %d does not match file uid %d", 221 filename, nuid, uid); 222 exit(EXIT_FAILURE); 223 } 224 if (ngid != gid) { 225 syslog(LOG_ERR,"Job %s - groupid %d does not match file gid %d", 226 filename, ngid, gid); 227 exit(EXIT_FAILURE); 228 } 229 fclose(stream); 230 if (chdir(ATSPOOL_DIR) < 0) 231 perr("Cannot chdir to " ATSPOOL_DIR); 232 233 /* Create a file to hold the output of the job we are about to run. 234 * Write the mail header. 235 */ 236 if((fd_out=open(filename, 237 O_WRONLY | O_CREAT | O_EXCL, S_IWUSR | S_IRUSR)) < 0) 238 perr("Cannot create output file"); 239 240 write_string(fd_out, "Subject: Output from your job "); 241 write_string(fd_out, filename); 242 write_string(fd_out, "\n\n"); 243 fstat(fd_out, &buf); 244 size = buf.st_size; 245 246 close(STDIN_FILENO); 247 close(STDOUT_FILENO); 248 close(STDERR_FILENO); 249 250 pid = fork(); 251 if (pid < 0) 252 perr("Error in fork"); 253 254 else if (pid == 0) 255 { 256 char *nul = NULL; 257 char **nenvp = &nul; 258 259 /* Set up things for the child; we want standard input from the input file, 260 * and standard output and error sent to our output file. 261 */ 262 263 if (lseek(fd_in, (off_t) 0, SEEK_SET) < 0) 264 perr("Error in lseek"); 265 266 if (dup(fd_in) != STDIN_FILENO) 267 perr("Error in I/O redirection"); 268 269 if (dup(fd_out) != STDOUT_FILENO) 270 perr("Error in I/O redirection"); 271 272 if (dup(fd_out) != STDERR_FILENO) 273 perr("Error in I/O redirection"); 274 275 close(fd_in); 276 close(fd_out); 277 if (chdir(ATJOB_DIR) < 0) 278 perr("Cannot chdir to " ATJOB_DIR); 279 280 queue = *filename; 281 282 PRIV_START 283 284 nice(tolower(queue) - 'a'); 285 286 if (chdir(pentry->pw_dir)) 287 chdir("/"); 288 289 if (initgroups(pentry->pw_name,pentry->pw_gid)) 290 perr("Cannot delete saved userids"); 291 292 if (setgid(gid) < 0) 293 perr("Cannot change group"); 294 295 if (setuid(uid) < 0) 296 perr("Cannot set user id"); 297 298 if(execle("/bin/sh","sh",(char *) NULL, nenvp) != 0) 299 perr("Exec failed for /bin/sh"); 300 301 PRIV_END 302 } 303 /* We're the parent. Let's wait. 304 */ 305 close(fd_in); 306 close(fd_out); 307 waitpid(pid, (int *) NULL, 0); 308 309 /* Send mail. Unlink the output file first, so it is deleted after 310 * the run. 311 */ 312 stat(filename, &buf); 313 if (open(filename, O_RDONLY) != STDIN_FILENO) 314 perr("Open of jobfile failed"); 315 316 unlink(filename); 317 if ((buf.st_size != size) || send_mail) 318 { 319 PRIV_START 320 321 if (chdir(pentry->pw_dir)) 322 chdir("/"); 323 324 if (initgroups(pentry->pw_name,pentry->pw_gid)) 325 perr("Cannot delete saved userids"); 326 327 if (setgid(gid) < 0) 328 perr("Cannot change group"); 329 330 if (setuid(uid) < 0) 331 perr("Cannot set user id"); 332 333 #ifdef __FreeBSD__ 334 execl(_PATH_SENDMAIL, "sendmail", "-F", "Atrun Service", 335 "-odi", "-oem", 336 mailname, (char *) NULL); 337 #else 338 execl(MAIL_CMD, MAIL_CMD, mailname, (char *) NULL); 339 #endif 340 perr("Exec failed for mail command"); 341 342 PRIV_END 343 } 344 exit(EXIT_SUCCESS); 345 } 346 347 /* Global functions */ 348 349 /* Needed in gloadavg.c */ 350 void 351 perr(const char *a) 352 { 353 if (debug) 354 { 355 perror(a); 356 } 357 else 358 syslog(LOG_ERR, "%s: %m", a); 359 360 exit(EXIT_FAILURE); 361 } 362 363 int 364 main(int argc, char *argv[]) 365 { 366 /* Browse through ATJOB_DIR, checking all the jobfiles wether they should 367 * be executed and or deleted. The queue is coded into the first byte of 368 * the job filename, the date (in minutes since Eon) as a hex number in the 369 * following eight bytes, followed by a dot and a serial number. A file 370 * which has not been executed yet is denoted by its execute - bit set. 371 * For those files which are to be executed, run_file() is called, which forks 372 * off a child which takes care of I/O redirection, forks off another child 373 * for execution and yet another one, optionally, for sending mail. 374 * Files which already have run are removed during the next invocation. 375 */ 376 DIR *spool; 377 struct dirent *dirent; 378 struct stat buf; 379 unsigned long ctm; 380 unsigned long jobno; 381 char queue; 382 time_t now, run_time; 383 char batch_name[] = "Z2345678901234"; 384 uid_t batch_uid; 385 gid_t batch_gid; 386 int c; 387 int run_batch; 388 double load_avg = LOADAVG_MX; 389 390 /* We don't need root privileges all the time; running under uid and gid daemon 391 * is fine. 392 */ 393 394 RELINQUISH_PRIVS_ROOT(DAEMON_UID, DAEMON_GID) 395 396 openlog("atrun", LOG_PID, LOG_CRON); 397 398 opterr = 0; 399 errno = 0; 400 while((c=getopt(argc, argv, "dl:"))!= -1) 401 { 402 switch (c) 403 { 404 case 'l': 405 if (sscanf(optarg, "%lf", &load_avg) != 1) 406 perr("garbled option -l"); 407 if (load_avg <= 0.) 408 load_avg = LOADAVG_MX; 409 break; 410 411 case 'd': 412 debug ++; 413 break; 414 415 case '?': 416 perr("unknown option"); 417 break; 418 419 default: 420 perr("idiotic option - aborted"); 421 break; 422 } 423 } 424 425 namep = argv[0]; 426 if (chdir(ATJOB_DIR) != 0) 427 perr("Cannot change to " ATJOB_DIR); 428 429 /* Main loop. Open spool directory for reading and look over all the 430 * files in there. If the filename indicates that the job should be run 431 * and the x bit is set, fork off a child which sets its user and group 432 * id to that of the files and exec a /bin/sh which executes the shell 433 * script. Unlink older files if they should no longer be run. For 434 * deletion, their r bit has to be turned on. 435 * 436 * Also, pick the oldest batch job to run, at most one per invocation of 437 * atrun. 438 */ 439 if ((spool = opendir(".")) == NULL) 440 perr("Cannot read " ATJOB_DIR); 441 442 now = time(NULL); 443 run_batch = 0; 444 batch_uid = (uid_t) -1; 445 batch_gid = (gid_t) -1; 446 447 while ((dirent = readdir(spool)) != NULL) { 448 if (stat(dirent->d_name,&buf) != 0) 449 perr("Cannot stat in " ATJOB_DIR); 450 451 /* We don't want directories 452 */ 453 if (!S_ISREG(buf.st_mode)) 454 continue; 455 456 if (sscanf(dirent->d_name,"%c%5lx%8lx",&queue,&jobno,&ctm) != 3) 457 continue; 458 459 run_time = (time_t) ctm*60; 460 461 if ((S_IXUSR & buf.st_mode) && (run_time <=now)) { 462 if (isupper(queue) && (strcmp(batch_name,dirent->d_name) > 0)) { 463 run_batch = 1; 464 strncpy(batch_name, dirent->d_name, sizeof(batch_name)); 465 batch_uid = buf.st_uid; 466 batch_gid = buf.st_gid; 467 } 468 469 /* The file is executable and old enough 470 */ 471 if (islower(queue)) 472 run_file(dirent->d_name, buf.st_uid, buf.st_gid); 473 } 474 /* Delete older files 475 */ 476 if ((run_time < now) && !(S_IXUSR & buf.st_mode) && (S_IRUSR & buf.st_mode)) 477 unlink(dirent->d_name); 478 } 479 /* run the single batch file, if any 480 */ 481 if (run_batch && (gloadavg() < load_avg)) 482 run_file(batch_name, batch_uid, batch_gid); 483 484 closelog(); 485 exit(EXIT_SUCCESS); 486 } 487