atrun.c revision 170741
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 27static const char rcsid[] = 28 "$FreeBSD: head/libexec/atrun/atrun.c 170741 2007-06-14 22:16:21Z yar $"; 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#ifdef LOGIN_CAP 58#include <login_cap.h> 59#endif 60 61#if (MAXLOGNAME-1) > UT_NAMESIZE 62#define LOGNAMESIZE UT_NAMESIZE 63#else 64#define LOGNAMESIZE (MAXLOGNAME-1) 65#endif 66 67/* Local headers */ 68 69#include "gloadavg.h" 70#define MAIN 71#include "privs.h" 72 73/* Macros */ 74 75#ifndef ATJOB_DIR 76#define ATJOB_DIR "/usr/spool/atjobs/" 77#endif 78 79#ifndef ATSPOOL_DIR 80#define ATSPOOL_DIR "/usr/spool/atspool/" 81#endif 82 83#ifndef LOADAVG_MX 84#define LOADAVG_MX 1.5 85#endif 86 87/* File scope variables */ 88 89static int debug = 0; 90 91void perr(const char *a); 92static void usage(void); 93 94/* Local functions */ 95static int 96write_string(int fd, const char* a) 97{ 98 return write(fd, a, strlen(a)); 99} 100 101#undef DEBUG_FORK 102#ifdef DEBUG_FORK 103static pid_t 104myfork(void) 105{ 106 pid_t res; 107 res = fork(); 108 if (res == 0) 109 kill(getpid(),SIGSTOP); 110 return res; 111} 112 113#define fork myfork 114#endif 115 116static void 117run_file(const char *filename, uid_t uid, gid_t gid) 118{ 119/* Run a file by spawning off a process which redirects I/O, 120 * spawns a subshell, then waits for it to complete and sends 121 * mail to the user. 122 */ 123 pid_t pid; 124 int fd_out, fd_in; 125 int queue; 126 char mailbuf[LOGNAMESIZE + 1], fmt[49]; 127 char *mailname = NULL; 128 FILE *stream; 129 int send_mail = 0; 130 struct stat buf, lbuf; 131 off_t size; 132 struct passwd *pentry; 133 int fflags; 134 long nuid; 135 long ngid; 136 137 138 PRIV_START 139 140 if (chmod(filename, S_IRUSR) != 0) 141 { 142 perr("cannot change file permissions"); 143 } 144 145 PRIV_END 146 147 pid = fork(); 148 if (pid == -1) 149 perr("cannot fork"); 150 151 else if (pid != 0) 152 return; 153 154 /* Let's see who we mail to. Hopefully, we can read it from 155 * the command file; if not, send it to the owner, or, failing that, 156 * to root. 157 */ 158 159 pentry = getpwuid(uid); 160 if (pentry == NULL) 161 { 162 syslog(LOG_ERR,"Userid %lu not found - aborting job %s", 163 (unsigned long) uid, filename); 164 exit(EXIT_FAILURE); 165 } 166 PRIV_START 167 168 stream=fopen(filename, "r"); 169 170 PRIV_END 171 172#ifdef __FreeBSD__ 173 if (pentry->pw_expire && time(NULL) >= pentry->pw_expire) 174 { 175 syslog(LOG_ERR, "Userid %lu is expired - aborting job %s", 176 (unsigned long) uid, filename); 177 exit(EXIT_FAILURE); 178 } 179#endif 180 181 if (stream == NULL) 182 perr("cannot open input file"); 183 184 if ((fd_in = dup(fileno(stream))) <0) 185 perr("error duplicating input file descriptor"); 186 187 if (fstat(fd_in, &buf) == -1) 188 perr("error in fstat of input file descriptor"); 189 190 if (lstat(filename, &lbuf) == -1) 191 perr("error in fstat of input file"); 192 193 if (S_ISLNK(lbuf.st_mode)) { 194 syslog(LOG_ERR,"Symbolic link encountered in job %s - aborting", 195 filename); 196 exit(EXIT_FAILURE); 197 } 198 if ((lbuf.st_dev != buf.st_dev) || (lbuf.st_ino != buf.st_ino) || 199 (lbuf.st_uid != buf.st_uid) || (lbuf.st_gid != buf.st_gid) || 200 (lbuf.st_size!=buf.st_size)) { 201 syslog(LOG_ERR,"Somebody changed files from under us for job %s - " 202 "aborting",filename); 203 exit(EXIT_FAILURE); 204 } 205 if (buf.st_nlink > 1) { 206 syslog(LOG_ERR,"Somebody is trying to run a linked script for job %s", 207 filename); 208 exit(EXIT_FAILURE); 209 } 210 if ((fflags = fcntl(fd_in, F_GETFD)) <0) 211 perr("error in fcntl"); 212 213 fcntl(fd_in, F_SETFD, fflags & ~FD_CLOEXEC); 214 215 snprintf(fmt, sizeof(fmt), 216 "#!/bin/sh\n# atrun uid=%%ld gid=%%ld\n# mail %%%ds %%d", 217 LOGNAMESIZE); 218 if (fscanf(stream, fmt, &nuid, &ngid, mailbuf, &send_mail) != 4) { 219 syslog(LOG_ERR,"File %s is in wrong format - aborting", filename); 220 exit(EXIT_FAILURE); 221 } 222 if (mailbuf[0] == '-') { 223 syslog(LOG_ERR,"illegal mail name %s in %s",mailbuf,filename); 224 exit(EXIT_FAILURE); 225 } 226 mailname = mailbuf; 227 if (nuid != uid) { 228 syslog(LOG_ERR,"Job %s - userid %ld does not match file uid %lu", 229 filename, nuid, (unsigned long)uid); 230 exit(EXIT_FAILURE); 231 } 232 if (ngid != gid) { 233 syslog(LOG_ERR,"Job %s - groupid %ld does not match file gid %lu", 234 filename, ngid, (unsigned long)gid); 235 exit(EXIT_FAILURE); 236 } 237 fclose(stream); 238 if (chdir(ATSPOOL_DIR) < 0) 239 perr("cannot chdir to " ATSPOOL_DIR); 240 241 /* Create a file to hold the output of the job we are about to run. 242 * Write the mail header. 243 */ 244 if((fd_out=open(filename, 245 O_WRONLY | O_CREAT | O_EXCL, S_IWUSR | S_IRUSR)) < 0) 246 perr("cannot create output file"); 247 248 write_string(fd_out, "Subject: Output from your job "); 249 write_string(fd_out, filename); 250 write_string(fd_out, "\n\n"); 251 fstat(fd_out, &buf); 252 size = buf.st_size; 253 254 close(STDIN_FILENO); 255 close(STDOUT_FILENO); 256 close(STDERR_FILENO); 257 258 pid = fork(); 259 if (pid < 0) 260 perr("error in fork"); 261 262 else if (pid == 0) 263 { 264 char *nul = NULL; 265 char **nenvp = &nul; 266 267 /* Set up things for the child; we want standard input from the input file, 268 * and standard output and error sent to our output file. 269 */ 270 271 if (lseek(fd_in, (off_t) 0, SEEK_SET) < 0) 272 perr("error in lseek"); 273 274 if (dup(fd_in) != STDIN_FILENO) 275 perr("error in I/O redirection"); 276 277 if (dup(fd_out) != STDOUT_FILENO) 278 perr("error in I/O redirection"); 279 280 if (dup(fd_out) != STDERR_FILENO) 281 perr("error in I/O redirection"); 282 283 close(fd_in); 284 close(fd_out); 285 if (chdir(ATJOB_DIR) < 0) 286 perr("cannot chdir to " ATJOB_DIR); 287 288 queue = *filename; 289 290 PRIV_START 291 292 nice(tolower(queue) - 'a'); 293 294#ifdef LOGIN_CAP 295 /* 296 * For simplicity and safety, set all aspects of the user context 297 * except for a selected subset: Don't set priority, which was 298 * set based on the queue file name according to the tradition. 299 * Don't bother to set environment, including path vars, either 300 * because it will be discarded anyway. Although the job file 301 * should set umask, preset it here just in case. 302 */ 303 if (setusercontext(NULL, pentry, uid, LOGIN_SETALL & 304 ~(LOGIN_SETPRIORITY | LOGIN_SETPATH | LOGIN_SETENV)) != 0) 305 exit(EXIT_FAILURE); /* setusercontext() logged the error */ 306#else /* LOGIN_CAP */ 307 if (initgroups(pentry->pw_name,pentry->pw_gid)) 308 perr("cannot init group access list"); 309 310 if (setgid(gid) < 0 || setegid(pentry->pw_gid) < 0) 311 perr("cannot change group"); 312 313 if (setlogin(pentry->pw_name)) 314 perr("cannot set login name"); 315 316 if (setuid(uid) < 0 || seteuid(uid) < 0) 317 perr("cannot set user id"); 318#endif /* LOGIN_CAP */ 319 320 if (chdir(pentry->pw_dir)) 321 chdir("/"); 322 323 if(execle("/bin/sh","sh",(char *) NULL, nenvp) != 0) 324 perr("exec failed for /bin/sh"); 325 326 PRIV_END 327 } 328 /* We're the parent. Let's wait. 329 */ 330 close(fd_in); 331 close(fd_out); 332 waitpid(pid, (int *) NULL, 0); 333 334 /* Send mail. Unlink the output file first, so it is deleted after 335 * the run. 336 */ 337 stat(filename, &buf); 338 if (open(filename, O_RDONLY) != STDIN_FILENO) 339 perr("open of jobfile failed"); 340 341 unlink(filename); 342 if ((buf.st_size != size) || send_mail) 343 { 344 PRIV_START 345 346#ifdef LOGIN_CAP 347 /* 348 * This time set full context to run the mailer. 349 */ 350 if (setusercontext(NULL, pentry, uid, LOGIN_SETALL) != 0) 351 exit(EXIT_FAILURE); /* setusercontext() logged the error */ 352#else /* LOGIN_CAP */ 353 if (initgroups(pentry->pw_name,pentry->pw_gid)) 354 perr("cannot init group access list"); 355 356 if (setgid(gid) < 0 || setegid(pentry->pw_gid) < 0) 357 perr("cannot change group"); 358 359 if (setlogin(pentry->pw_name)) 360 perr("cannot set login name"); 361 362 if (setuid(uid) < 0 || seteuid(uid) < 0) 363 perr("cannot set user id"); 364#endif /* LOGIN_CAP */ 365 366 if (chdir(pentry->pw_dir)) 367 chdir("/"); 368 369#ifdef __FreeBSD__ 370 execl(_PATH_SENDMAIL, "sendmail", "-F", "Atrun Service", 371 "-odi", "-oem", 372 mailname, (char *) NULL); 373#else 374 execl(MAIL_CMD, MAIL_CMD, mailname, (char *) NULL); 375#endif 376 perr("exec failed for mail command"); 377 378 PRIV_END 379 } 380 exit(EXIT_SUCCESS); 381} 382 383/* Global functions */ 384 385/* Needed in gloadavg.c */ 386void 387perr(const char *a) 388{ 389 if (debug) 390 { 391 warn("%s", a); 392 } 393 else 394 syslog(LOG_ERR, "%s: %m", a); 395 396 exit(EXIT_FAILURE); 397} 398 399int 400main(int argc, char *argv[]) 401{ 402/* Browse through ATJOB_DIR, checking all the jobfiles wether they should 403 * be executed and or deleted. The queue is coded into the first byte of 404 * the job filename, the date (in minutes since Eon) as a hex number in the 405 * following eight bytes, followed by a dot and a serial number. A file 406 * which has not been executed yet is denoted by its execute - bit set. 407 * For those files which are to be executed, run_file() is called, which forks 408 * off a child which takes care of I/O redirection, forks off another child 409 * for execution and yet another one, optionally, for sending mail. 410 * Files which already have run are removed during the next invocation. 411 */ 412 DIR *spool; 413 struct dirent *dirent; 414 struct stat buf; 415 unsigned long ctm; 416 unsigned long jobno; 417 char queue; 418 time_t now, run_time; 419 char batch_name[] = "Z2345678901234"; 420 uid_t batch_uid; 421 gid_t batch_gid; 422 int c; 423 int run_batch; 424 double load_avg = LOADAVG_MX; 425 426/* We don't need root privileges all the time; running under uid and gid daemon 427 * is fine. 428 */ 429 430 RELINQUISH_PRIVS_ROOT(DAEMON_UID, DAEMON_GID) 431 432 openlog("atrun", LOG_PID, LOG_CRON); 433 434 opterr = 0; 435 while((c=getopt(argc, argv, "dl:"))!= -1) 436 { 437 switch (c) 438 { 439 case 'l': 440 if (sscanf(optarg, "%lf", &load_avg) != 1) 441 perr("garbled option -l"); 442 if (load_avg <= 0.) 443 load_avg = LOADAVG_MX; 444 break; 445 446 case 'd': 447 debug ++; 448 break; 449 450 case '?': 451 default: 452 usage(); 453 } 454 } 455 456 if (chdir(ATJOB_DIR) != 0) 457 perr("cannot change to " ATJOB_DIR); 458 459 /* Main loop. Open spool directory for reading and look over all the 460 * files in there. If the filename indicates that the job should be run 461 * and the x bit is set, fork off a child which sets its user and group 462 * id to that of the files and exec a /bin/sh which executes the shell 463 * script. Unlink older files if they should no longer be run. For 464 * deletion, their r bit has to be turned on. 465 * 466 * Also, pick the oldest batch job to run, at most one per invocation of 467 * atrun. 468 */ 469 if ((spool = opendir(".")) == NULL) 470 perr("cannot read " ATJOB_DIR); 471 472 now = time(NULL); 473 run_batch = 0; 474 batch_uid = (uid_t) -1; 475 batch_gid = (gid_t) -1; 476 477 while ((dirent = readdir(spool)) != NULL) { 478 if (stat(dirent->d_name,&buf) != 0) 479 perr("cannot stat in " ATJOB_DIR); 480 481 /* We don't want directories 482 */ 483 if (!S_ISREG(buf.st_mode)) 484 continue; 485 486 if (sscanf(dirent->d_name,"%c%5lx%8lx",&queue,&jobno,&ctm) != 3) 487 continue; 488 489 run_time = (time_t) ctm*60; 490 491 if ((S_IXUSR & buf.st_mode) && (run_time <=now)) { 492 if (isupper(queue) && (strcmp(batch_name,dirent->d_name) > 0)) { 493 run_batch = 1; 494 strlcpy(batch_name, dirent->d_name, sizeof(batch_name)); 495 batch_uid = buf.st_uid; 496 batch_gid = buf.st_gid; 497 } 498 499 /* The file is executable and old enough 500 */ 501 if (islower(queue)) 502 run_file(dirent->d_name, buf.st_uid, buf.st_gid); 503 } 504 /* Delete older files 505 */ 506 if ((run_time < now) && !(S_IXUSR & buf.st_mode) && (S_IRUSR & buf.st_mode)) 507 unlink(dirent->d_name); 508 } 509 /* run the single batch file, if any 510 */ 511 if (run_batch && (gloadavg() < load_avg)) 512 run_file(batch_name, batch_uid, batch_gid); 513 514 closelog(); 515 exit(EXIT_SUCCESS); 516} 517 518static void 519usage(void) 520{ 521 if (debug) 522 fprintf(stderr, "usage: atrun [-l load_avg] [-d]\n"); 523 else 524 syslog(LOG_ERR, "usage: atrun [-l load_avg] [-d]"); 525 526 exit(EXIT_FAILURE); 527} 528