atrun.c revision 170769
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 170769 2007-06-15 10:34:36Z 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 <stdarg.h> 45#include <stddef.h> 46#include <stdio.h> 47#include <stdlib.h> 48#include <string.h> 49#include <syslog.h> 50#include <time.h> 51#include <unistd.h> 52#include <utmp.h> 53#ifdef __FreeBSD__ 54#include <paths.h> 55#else 56#include <getopt.h> 57#endif 58#ifdef LOGIN_CAP 59#include <login_cap.h> 60#endif 61 62#if (MAXLOGNAME-1) > UT_NAMESIZE 63#define LOGNAMESIZE UT_NAMESIZE 64#else 65#define LOGNAMESIZE (MAXLOGNAME-1) 66#endif 67 68/* Local headers */ 69 70#include "gloadavg.h" 71#define MAIN 72#include "privs.h" 73 74/* Macros */ 75 76#ifndef ATJOB_DIR 77#define ATJOB_DIR "/usr/spool/atjobs/" 78#endif 79 80#ifndef ATSPOOL_DIR 81#define ATSPOOL_DIR "/usr/spool/atspool/" 82#endif 83 84#ifndef LOADAVG_MX 85#define LOADAVG_MX 1.5 86#endif 87 88/* File scope variables */ 89 90static int debug = 0; 91 92void perr(const char *fmt, ...); 93void perrx(const char *fmt, ...); 94static void usage(void); 95 96/* Local functions */ 97static int 98write_string(int fd, const char* a) 99{ 100 return write(fd, a, strlen(a)); 101} 102 103#undef DEBUG_FORK 104#ifdef DEBUG_FORK 105static pid_t 106myfork(void) 107{ 108 pid_t res; 109 res = fork(); 110 if (res == 0) 111 kill(getpid(),SIGSTOP); 112 return res; 113} 114 115#define fork myfork 116#endif 117 118static void 119run_file(const char *filename, uid_t uid, gid_t gid) 120{ 121/* Run a file by spawning off a process which redirects I/O, 122 * spawns a subshell, then waits for it to complete and sends 123 * mail to the user. 124 */ 125 pid_t pid; 126 int fd_out, fd_in; 127 int queue; 128 char mailbuf[LOGNAMESIZE + 1], fmt[49]; 129 char *mailname = NULL; 130 FILE *stream; 131 int send_mail = 0; 132 struct stat buf, lbuf; 133 off_t size; 134 struct passwd *pentry; 135 int fflags; 136 long nuid; 137 long ngid; 138 139 140 PRIV_START 141 142 if (chmod(filename, S_IRUSR) != 0) 143 { 144 perr("cannot change file permissions"); 145 } 146 147 PRIV_END 148 149 pid = fork(); 150 if (pid == -1) 151 perr("cannot fork"); 152 153 else if (pid != 0) 154 return; 155 156 /* Let's see who we mail to. Hopefully, we can read it from 157 * the command file; if not, send it to the owner, or, failing that, 158 * to root. 159 */ 160 161 pentry = getpwuid(uid); 162 if (pentry == NULL) 163 perrx("Userid %lu not found - aborting job %s", 164 (unsigned long) uid, filename); 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 perrx("Userid %lu is expired - aborting job %s", 175 (unsigned long) uid, filename); 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 perrx("Symbolic link encountered in job %s - aborting", filename); 192 193 if ((lbuf.st_dev != buf.st_dev) || (lbuf.st_ino != buf.st_ino) || 194 (lbuf.st_uid != buf.st_uid) || (lbuf.st_gid != buf.st_gid) || 195 (lbuf.st_size!=buf.st_size)) 196 perrx("Somebody changed files from under us for job %s - aborting", 197 filename); 198 199 if (buf.st_nlink > 1) 200 perrx("Somebody is trying to run a linked script for job %s", filename); 201 202 if ((fflags = fcntl(fd_in, F_GETFD)) <0) 203 perr("error in fcntl"); 204 205 fcntl(fd_in, F_SETFD, fflags & ~FD_CLOEXEC); 206 207 snprintf(fmt, sizeof(fmt), 208 "#!/bin/sh\n# atrun uid=%%ld gid=%%ld\n# mail %%%ds %%d", 209 LOGNAMESIZE); 210 211 if (fscanf(stream, fmt, &nuid, &ngid, mailbuf, &send_mail) != 4) 212 perrx("File %s is in wrong format - aborting", filename); 213 214 if (mailbuf[0] == '-') 215 perrx("Illegal mail name %s in %s", mailbuf, filename); 216 217 mailname = mailbuf; 218 219 if (nuid != uid) 220 perrx("Job %s - userid %ld does not match file uid %lu", 221 filename, nuid, (unsigned long)uid); 222 223 if (ngid != gid) 224 perrx("Job %s - groupid %ld does not match file gid %lu", 225 filename, ngid, (unsigned long)gid); 226 227 fclose(stream); 228 229 if (chdir(ATSPOOL_DIR) < 0) 230 perr("cannot chdir to %s", ATSPOOL_DIR); 231 232 /* Create a file to hold the output of the job we are about to run. 233 * Write the mail header. 234 */ 235 if((fd_out=open(filename, 236 O_WRONLY | O_CREAT | O_EXCL, S_IWUSR | S_IRUSR)) < 0) 237 perr("cannot create output file"); 238 239 write_string(fd_out, "Subject: Output from your job "); 240 write_string(fd_out, filename); 241 write_string(fd_out, "\n\n"); 242 fstat(fd_out, &buf); 243 size = buf.st_size; 244 245 close(STDIN_FILENO); 246 close(STDOUT_FILENO); 247 close(STDERR_FILENO); 248 249 pid = fork(); 250 if (pid < 0) 251 perr("error in fork"); 252 253 else if (pid == 0) 254 { 255 char *nul = NULL; 256 char **nenvp = &nul; 257 258 /* Set up things for the child; we want standard input from the input file, 259 * and standard output and error sent to our output file. 260 */ 261 262 if (lseek(fd_in, (off_t) 0, SEEK_SET) < 0) 263 perr("error in lseek"); 264 265 if (dup(fd_in) != STDIN_FILENO) 266 perr("error in I/O redirection"); 267 268 if (dup(fd_out) != STDOUT_FILENO) 269 perr("error in I/O redirection"); 270 271 if (dup(fd_out) != STDERR_FILENO) 272 perr("error in I/O redirection"); 273 274 close(fd_in); 275 close(fd_out); 276 if (chdir(ATJOB_DIR) < 0) 277 perr("cannot chdir to %s", ATJOB_DIR); 278 279 queue = *filename; 280 281 PRIV_START 282 283 nice(tolower(queue) - 'a'); 284 285#ifdef LOGIN_CAP 286 /* 287 * For simplicity and safety, set all aspects of the user context 288 * except for a selected subset: Don't set priority, which was 289 * set based on the queue file name according to the tradition. 290 * Don't bother to set environment, including path vars, either 291 * because it will be discarded anyway. Although the job file 292 * should set umask, preset it here just in case. 293 */ 294 if (setusercontext(NULL, pentry, uid, LOGIN_SETALL & 295 ~(LOGIN_SETPRIORITY | LOGIN_SETPATH | LOGIN_SETENV)) != 0) 296 exit(EXIT_FAILURE); /* setusercontext() logged the error */ 297#else /* LOGIN_CAP */ 298 if (initgroups(pentry->pw_name,pentry->pw_gid)) 299 perr("cannot init group access list"); 300 301 if (setgid(gid) < 0 || setegid(pentry->pw_gid) < 0) 302 perr("cannot change group"); 303 304 if (setlogin(pentry->pw_name)) 305 perr("cannot set login name"); 306 307 if (setuid(uid) < 0 || seteuid(uid) < 0) 308 perr("cannot set user id"); 309#endif /* LOGIN_CAP */ 310 311 if (chdir(pentry->pw_dir)) 312 chdir("/"); 313 314 if(execle("/bin/sh","sh",(char *) NULL, nenvp) != 0) 315 perr("exec failed for /bin/sh"); 316 317 PRIV_END 318 } 319 /* We're the parent. Let's wait. 320 */ 321 close(fd_in); 322 close(fd_out); 323 waitpid(pid, (int *) NULL, 0); 324 325 /* Send mail. Unlink the output file first, so it is deleted after 326 * the run. 327 */ 328 stat(filename, &buf); 329 if (open(filename, O_RDONLY) != STDIN_FILENO) 330 perr("open of jobfile failed"); 331 332 unlink(filename); 333 if ((buf.st_size != size) || send_mail) 334 { 335 PRIV_START 336 337#ifdef LOGIN_CAP 338 /* 339 * This time set full context to run the mailer. 340 */ 341 if (setusercontext(NULL, pentry, uid, LOGIN_SETALL) != 0) 342 exit(EXIT_FAILURE); /* setusercontext() logged the error */ 343#else /* LOGIN_CAP */ 344 if (initgroups(pentry->pw_name,pentry->pw_gid)) 345 perr("cannot init group access list"); 346 347 if (setgid(gid) < 0 || setegid(pentry->pw_gid) < 0) 348 perr("cannot change group"); 349 350 if (setlogin(pentry->pw_name)) 351 perr("cannot set login name"); 352 353 if (setuid(uid) < 0 || seteuid(uid) < 0) 354 perr("cannot set user id"); 355#endif /* LOGIN_CAP */ 356 357 if (chdir(pentry->pw_dir)) 358 chdir("/"); 359 360#ifdef __FreeBSD__ 361 execl(_PATH_SENDMAIL, "sendmail", "-F", "Atrun Service", 362 "-odi", "-oem", 363 mailname, (char *) NULL); 364#else 365 execl(MAIL_CMD, MAIL_CMD, mailname, (char *) NULL); 366#endif 367 perr("exec failed for mail command"); 368 369 PRIV_END 370 } 371 exit(EXIT_SUCCESS); 372} 373 374/* Global functions */ 375 376/* Needed in gloadavg.c */ 377void 378perr(const char *fmt, ...) 379{ 380 const char * const fmtadd = ": %m"; 381 char nfmt[strlen(fmt) + strlen(fmtadd) + 1]; 382 va_list ap; 383 384 va_start(ap, fmt); 385 if (debug) 386 { 387 vwarn(fmt, ap); 388 } 389 else 390 { 391 snprintf(nfmt, sizeof(nfmt), "%s%s", fmt, fmtadd); 392 vsyslog(LOG_ERR, nfmt, ap); 393 } 394 va_end(ap); 395 396 exit(EXIT_FAILURE); 397} 398 399void 400perrx(const char *fmt, ...) 401{ 402 va_list ap; 403 404 va_start(ap, fmt); 405 if (debug) 406 vwarnx(fmt, ap); 407 else 408 vsyslog(LOG_ERR, fmt, ap); 409 va_end(ap); 410 411 exit(EXIT_FAILURE); 412} 413 414int 415main(int argc, char *argv[]) 416{ 417/* Browse through ATJOB_DIR, checking all the jobfiles wether they should 418 * be executed and or deleted. The queue is coded into the first byte of 419 * the job filename, the date (in minutes since Eon) as a hex number in the 420 * following eight bytes, followed by a dot and a serial number. A file 421 * which has not been executed yet is denoted by its execute - bit set. 422 * For those files which are to be executed, run_file() is called, which forks 423 * off a child which takes care of I/O redirection, forks off another child 424 * for execution and yet another one, optionally, for sending mail. 425 * Files which already have run are removed during the next invocation. 426 */ 427 DIR *spool; 428 struct dirent *dirent; 429 struct stat buf; 430 unsigned long ctm; 431 unsigned long jobno; 432 char queue; 433 time_t now, run_time; 434 char batch_name[] = "Z2345678901234"; 435 uid_t batch_uid; 436 gid_t batch_gid; 437 int c; 438 int run_batch; 439 double load_avg = LOADAVG_MX; 440 441/* We don't need root privileges all the time; running under uid and gid daemon 442 * is fine. 443 */ 444 445 RELINQUISH_PRIVS_ROOT(DAEMON_UID, DAEMON_GID) 446 447 openlog("atrun", LOG_PID, LOG_CRON); 448 449 opterr = 0; 450 while((c=getopt(argc, argv, "dl:"))!= -1) 451 { 452 switch (c) 453 { 454 case 'l': 455 if (sscanf(optarg, "%lf", &load_avg) != 1) 456 perr("garbled option -l"); 457 if (load_avg <= 0.) 458 load_avg = LOADAVG_MX; 459 break; 460 461 case 'd': 462 debug ++; 463 break; 464 465 case '?': 466 default: 467 usage(); 468 } 469 } 470 471 if (chdir(ATJOB_DIR) != 0) 472 perr("cannot change to %s", ATJOB_DIR); 473 474 /* Main loop. Open spool directory for reading and look over all the 475 * files in there. If the filename indicates that the job should be run 476 * and the x bit is set, fork off a child which sets its user and group 477 * id to that of the files and exec a /bin/sh which executes the shell 478 * script. Unlink older files if they should no longer be run. For 479 * deletion, their r bit has to be turned on. 480 * 481 * Also, pick the oldest batch job to run, at most one per invocation of 482 * atrun. 483 */ 484 if ((spool = opendir(".")) == NULL) 485 perr("cannot read %s", ATJOB_DIR); 486 487 now = time(NULL); 488 run_batch = 0; 489 batch_uid = (uid_t) -1; 490 batch_gid = (gid_t) -1; 491 492 while ((dirent = readdir(spool)) != NULL) { 493 if (stat(dirent->d_name,&buf) != 0) 494 perr("cannot stat in %s", ATJOB_DIR); 495 496 /* We don't want directories 497 */ 498 if (!S_ISREG(buf.st_mode)) 499 continue; 500 501 if (sscanf(dirent->d_name,"%c%5lx%8lx",&queue,&jobno,&ctm) != 3) 502 continue; 503 504 run_time = (time_t) ctm*60; 505 506 if ((S_IXUSR & buf.st_mode) && (run_time <=now)) { 507 if (isupper(queue) && (strcmp(batch_name,dirent->d_name) > 0)) { 508 run_batch = 1; 509 strlcpy(batch_name, dirent->d_name, sizeof(batch_name)); 510 batch_uid = buf.st_uid; 511 batch_gid = buf.st_gid; 512 } 513 514 /* The file is executable and old enough 515 */ 516 if (islower(queue)) 517 run_file(dirent->d_name, buf.st_uid, buf.st_gid); 518 } 519 /* Delete older files 520 */ 521 if ((run_time < now) && !(S_IXUSR & buf.st_mode) && (S_IRUSR & buf.st_mode)) 522 unlink(dirent->d_name); 523 } 524 /* run the single batch file, if any 525 */ 526 if (run_batch && (gloadavg() < load_avg)) 527 run_file(batch_name, batch_uid, batch_gid); 528 529 closelog(); 530 exit(EXIT_SUCCESS); 531} 532 533static void 534usage(void) 535{ 536 if (debug) 537 fprintf(stderr, "usage: atrun [-l load_avg] [-d]\n"); 538 else 539 syslog(LOG_ERR, "usage: atrun [-l load_avg] [-d]"); 540 541 exit(EXIT_FAILURE); 542} 543