libexec/atrun/atrun.c

   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  * $FreeBSD: src/libexec/atrun/atrun.c,v 1.26 2007/06/15 12:02:16 yar Exp $
  26  * $DragonFly: src/libexec/atrun/atrun.c,v 1.5 2004/09/20 19:32:19 joerg Exp $
  27  */
  28
  29 /* System Headers */
  30
  31 #include <sys/fcntl.h>
  32 #include <sys/types.h>
  33 #include <sys/stat.h>
  34 #include <sys/wait.h>
  35 #include <sys/param.h>
  36 #include <ctype.h>
  37 #include <dirent.h>
  38 #include <err.h>
  39 #include <grp.h>
  40 #include <pwd.h>
  41 #include <signal.h>
  42 #include <stdarg.h>
  43 #include <stddef.h>
  44 #include <stdio.h>
  45 #include <stdlib.h>
  46 #include <string.h>
  47 #include <syslog.h>
  48 #include <time.h>
  49 #include <unistd.h>
  50 #include <utmp.h>
  51 #include <paths.h>
  52 #ifdef LOGIN_CAP
  53 #include <login_cap.h>
  54 #endif
  55 #ifdef PAM
  56 #include <security/pam_appl.h>
  57 #include <security/openpam.h>
  58 #endif
  59
  60 #if (MAXLOGNAME-1) > UT_NAMESIZE
  61 #define LOGNAMESIZE UT_NAMESIZE
  62 #else
  63 #define LOGNAMESIZE (MAXLOGNAME-1)
  64 #endif
  65
  66 /* Local headers */
  67
  68 #include "gloadavg.h"
  69 #include "privs.h"
  70
  71 /* Macros */
  72
  73 #ifndef ATJOB_DIR
  74 #define ATJOB_DIR "/usr/spool/atjobs/"
  75 #endif
  76
  77 #ifndef ATSPOOL_DIR
  78 #define ATSPOOL_DIR "/usr/spool/atspool/"
  79 #endif
  80
  81 #ifndef LOADAVG_MX
  82 #define LOADAVG_MX 1.5
  83 #endif
  84
  85 uid_t real_uid, effective_uid;
  86 gid_t real_gid, effective_gid;
  87
  88 /* File scope variables */
  89
  90 static const char * const atrun = "atrun"; /* service name for syslog etc. */
  91 static int debug = 0;
  92
  93 void            perr(const char *fmt, ...);
  94 void            perrx(const char *fmt, ...);
  95 static void     usage(void);
  96
  97 /* Local functions */
  98 static int
  99 write_string(int fd, const char* a)
 100 {
 101     return write(fd, a, strlen(a));
 102 }
 103
 104 #undef DEBUG_FORK
 105 #ifdef DEBUG_FORK
 106 static pid_t
 107 myfork(void)
 108 {
 109         pid_t res;
 110         res = fork();
 111         if (res == 0)
 112             kill(getpid(),SIGSTOP);
 113         return res;
 114 }
 115
 116 #define fork myfork
 117 #endif
 118
 119 static void
 120 run_file(const char *filename, uid_t uid, gid_t gid)
 121 {
 122 /* Run a file by spawning off a process which redirects I/O,
 123  * spawns a subshell, then waits for it to complete and sends
 124  * mail to the user.
 125  */
 126     pid_t pid;
 127     int fd_out, fd_in;
 128     int queue;
 129     char mailbuf[LOGNAMESIZE + 1], fmt[49];
 130     char *mailname = NULL;
 131     FILE *stream;
 132     int send_mail = 0;
 133     struct stat buf, lbuf;
 134     off_t size;
 135     struct passwd *pentry;
 136     int fflags;
 137     uid_t nuid;
 138     gid_t ngid;
 139 #ifdef PAM
 140     pam_handle_t *pamh = NULL;
 141     int pam_err;
 142     struct pam_conv pamc = {
 143         .conv = openpam_nullconv,
 144         .appdata_ptr = NULL
 145     };
 146 #endif
 147
 148     PRIV_START
 149
 150     if (chmod(filename, S_IRUSR) != 0)
 151     {
 152         perr("cannot change file permissions");
 153     }
 154
 155     PRIV_END
 156
 157     pid = fork();
 158     if (pid == -1)
 159         perr("cannot fork");
 160
 161     else if (pid != 0)
 162         return;
 163
 164     /* Let's see who we mail to.  Hopefully, we can read it from
 165      * the command file; if not, send it to the owner, or, failing that,
 166      * to root.
 167      */
 168
 169     pentry = getpwuid(uid);
 170     if (pentry == NULL)
 171         perrx("Userid %lu not found - aborting job %s",
 172                 (unsigned long) uid, filename);
 173
 174 #ifdef PAM
 175     PRIV_START
 176
 177     pam_err = pam_start(atrun, pentry->pw_name, &pamc, &pamh);
 178     if (pam_err != PAM_SUCCESS)
 179         perrx("cannot start PAM: %s", pam_strerror(pamh, pam_err));
 180
 181     pam_err = pam_acct_mgmt(pamh, PAM_SILENT);
 182     /* Expired password shouldn't prevent the job from running. */
 183     if (pam_err != PAM_SUCCESS && pam_err != PAM_NEW_AUTHTOK_REQD)
 184         perrx("Account %s (userid %lu) unavailable for job %s: %s",
 185             pentry->pw_name, (unsigned long)uid,
 186             filename, pam_strerror(pamh, pam_err));
 187
 188     pam_end(pamh, pam_err);
 189
 190     PRIV_END
 191 #endif /* PAM */
 192
 193     PRIV_START
 194
 195     stream=fopen(filename, "r");
 196
 197     PRIV_END
 198
 199     if (stream == NULL)
 200         perr("cannot open input file");
 201
 202     if ((fd_in = dup(fileno(stream))) <0)
 203         perr("error duplicating input file descriptor");
 204
 205     if (fstat(fd_in, &buf) == -1)
 206         perr("error in fstat of input file descriptor");
 207
 208     if (lstat(filename, &lbuf) == -1)
 209         perr("error in fstat of input file");
 210
 211     if (S_ISLNK(lbuf.st_mode))
 212         perrx("Symbolic link encountered in job %s - aborting", filename);
 213
 214     if ((lbuf.st_dev != buf.st_dev) || (lbuf.st_ino != buf.st_ino) ||
 215         (lbuf.st_uid != buf.st_uid) || (lbuf.st_gid != buf.st_gid) ||
 216         (lbuf.st_size!=buf.st_size))
 217         perrx("Somebody changed files from under us for job %s - aborting",
 218                 filename);
 219
 220     if (buf.st_nlink > 1)
 221         perrx("Somebody is trying to run a linked script for job %s", filename);
 222
 223     if ((fflags = fcntl(fd_in, F_GETFD)) <0)
 224         perr("error in fcntl");
 225
 226     fcntl(fd_in, F_SETFD, fflags & ~FD_CLOEXEC);
 227
 228     snprintf(fmt, sizeof(fmt),
 229         "#!/bin/sh\n# atrun uid=%%ld gid=%%ld\n# mail %%%ds %%d",
 230                           LOGNAMESIZE);
 231
 232     if (fscanf(stream, fmt, &nuid, &ngid, mailbuf, &send_mail) != 4)
 233         perrx("File %s is in wrong format - aborting", filename);
 234
 235     if (mailbuf[0] == '-')
 236         perrx("Illegal mail name %s in %s", mailbuf, filename);
 237
 238     mailname = mailbuf;
 239
 240     if (nuid != uid)
 241         perrx("Job %s - userid %ld does not match file uid %lu",
 242                 filename, nuid, (unsigned long)uid);
 243
 244     if (ngid != gid)
 245         perrx("Job %s - groupid %ld does not match file gid %lu",
 246                 filename, ngid, (unsigned long)gid);
 247
 248     fclose(stream);
 249
 250     if (chdir(ATSPOOL_DIR) < 0)
 251         perr("cannot chdir to %s", ATSPOOL_DIR);
 252
 253     /* Create a file to hold the output of the job we are about to run.
 254      * Write the mail header.
 255      */
 256     if((fd_out=open(filename,
 257                 O_WRONLY | O_CREAT | O_EXCL, S_IWUSR | S_IRUSR)) < 0)
 258         perr("cannot create output file");
 259
 260     write_string(fd_out, "Subject: Output from your job ");
 261     write_string(fd_out, filename);
 262     write_string(fd_out, "\n\n");
 263     fstat(fd_out, &buf);
 264     size = buf.st_size;
 265
 266     close(STDIN_FILENO);
 267     close(STDOUT_FILENO);
 268     close(STDERR_FILENO);
 269
 270     pid = fork();
 271     if (pid < 0)
 272         perr("error in fork");
 273
 274     else if (pid == 0)
 275     {
 276         char *nul = NULL;
 277         char **nenvp = &nul;
 278
 279         /* Set up things for the child; we want standard input from the input file,
 280          * and standard output and error sent to our output file.
 281          */
 282
 283         if (lseek(fd_in, (off_t) 0, SEEK_SET) < 0)
 284             perr("error in lseek");
 285
 286         if (dup(fd_in) != STDIN_FILENO)
 287             perr("error in I/O redirection");
 288
 289         if (dup(fd_out) != STDOUT_FILENO)
 290             perr("error in I/O redirection");
 291
 292         if (dup(fd_out) != STDERR_FILENO)
 293             perr("error in I/O redirection");
 294
 295         close(fd_in);
 296         close(fd_out);
 297         if (chdir(ATJOB_DIR) < 0)
 298             perr("cannot chdir to %s", ATJOB_DIR);
 299
 300         queue = *filename;
 301
 302         PRIV_START
 303
 304         nice(tolower(queue) - 'a');
 305
 306 #ifdef LOGIN_CAP
 307         /*
 308          * For simplicity and safety, set all aspects of the user context
 309          * except for a selected subset:  Don't set priority, which was
 310          * set based on the queue file name according to the tradition.
 311          * Don't bother to set environment, including path vars, either
 312          * because it will be discarded anyway.  Although the job file
 313          * should set umask, preset it here just in case.
 314          */
 315         if (setusercontext(NULL, pentry, uid, LOGIN_SETALL &
 316                 ~(LOGIN_SETPRIORITY | LOGIN_SETPATH | LOGIN_SETENV)) != 0)
 317             exit(EXIT_FAILURE); /* setusercontext() logged the error */
 318 #else /* LOGIN_CAP */
 319         if (initgroups(pentry->pw_name,pentry->pw_gid))
 320             perr("cannot init group access list");
 321
 322         if (setgid(gid) < 0 || setegid(pentry->pw_gid) < 0)
 323             perr("cannot change group");
 324
 325         if (setlogin(pentry->pw_name))
 326             perr("cannot set login name");
 327
 328         if (setuid(uid) < 0 || seteuid(uid) < 0)
 329             perr("cannot set user id");
 330 #endif /* LOGIN_CAP */
 331
 332         if (chdir(pentry->pw_dir))
 333                 chdir("/");
 334
 335         if(execle("/bin/sh","sh",NULL, nenvp) != 0)
 336             perr("exec failed for /bin/sh");
 337
 338         PRIV_END
 339     }
 340     /* We're the parent.  Let's wait.
 341      */
 342     close(fd_in);
 343     close(fd_out);
 344     waitpid(pid, NULL, 0);
 345
 346     /* Send mail.  Unlink the output file first, so it is deleted after
 347      * the run.
 348      */
 349     stat(filename, &buf);
 350     if (open(filename, O_RDONLY) != STDIN_FILENO)
 351         perr("open of jobfile failed");
 352
 353     unlink(filename);
 354     if ((buf.st_size != size) || send_mail)
 355     {
 356         PRIV_START
 357
 358 #ifdef LOGIN_CAP
 359         /*
 360          * This time set full context to run the mailer.
 361          */
 362         if (setusercontext(NULL, pentry, uid, LOGIN_SETALL) != 0)
 363             exit(EXIT_FAILURE); /* setusercontext() logged the error */
 364 #else /* LOGIN_CAP */
 365         if (initgroups(pentry->pw_name,pentry->pw_gid))
 366             perr("cannot init group access list");
 367
 368         if (setgid(gid) < 0 || setegid(pentry->pw_gid) < 0)
 369             perr("cannot change group");
 370
 371         if (setlogin(pentry->pw_name))
 372             perr("cannot set login name");
 373
 374         if (setuid(uid) < 0 || seteuid(uid) < 0)
 375             perr("cannot set user id");
 376 #endif /* LOGIN_CAP */
 377
 378         if (chdir(pentry->pw_dir))
 379                 chdir("/");
 380
 381         execl(_PATH_SENDMAIL, "sendmail", "-F", "Atrun Service",
 382                         "-odi", "-oem",
 383                         mailname, NULL);
 384             perr("exec failed for mail command");
 385
 386         PRIV_END
 387     }
 388     exit(EXIT_SUCCESS);
 389 }
 390
 391 /* Global functions */
 392
 393 /* Needed in gloadavg.c */
 394 void
 395 perr(const char *fmt, ...)
 396 {
 397     const char * const fmtadd = ": %m";
 398     char nfmt[strlen(fmt) + strlen(fmtadd) + 1];
 399     va_list ap;
 400
 401     va_start(ap, fmt);
 402     if (debug)
 403     {
 404         vwarn(fmt, ap);
 405     }
 406     else
 407     {
 408         snprintf(nfmt, sizeof(nfmt), "%s%s", fmt, fmtadd);
 409         vsyslog(LOG_ERR, nfmt, ap);
 410     }
 411     va_end(ap);
 412
 413     exit(EXIT_FAILURE);
 414 }
 415
 416 void
 417 perrx(const char *fmt, ...)
 418 {
 419     va_list ap;
 420
 421     va_start(ap, fmt);
 422     if (debug)
 423         vwarnx(fmt, ap);
 424     else
 425         vsyslog(LOG_ERR, fmt, ap);
 426     va_end(ap);
 427
 428     exit(EXIT_FAILURE);
 429 }
 430
 431 int
 432 main(int argc, char *argv[])
 433 {
 434 /* Browse through  ATJOB_DIR, checking all the jobfiles wether they should
 435  * be executed and or deleted. The queue is coded into the first byte of
 436  * the job filename, the date (in minutes since Eon) as a hex number in the
 437  * following eight bytes, followed by a dot and a serial number.  A file
 438  * which has not been executed yet is denoted by its execute - bit set.
 439  * For those files which are to be executed, run_file() is called, which forks
 440  * off a child which takes care of I/O redirection, forks off another child
 441  * for execution and yet another one, optionally, for sending mail.
 442  * Files which already have run are removed during the next invocation.
 443  */
 444     DIR *spool;
 445     struct dirent *dirent;
 446     struct stat buf;
 447     unsigned long ctm;
 448     unsigned long jobno;
 449     char queue;
 450     time_t now, run_time;
 451     char batch_name[] = "Z2345678901234";
 452     uid_t batch_uid;
 453     gid_t batch_gid;
 454     int c;
 455     int run_batch;
 456     double load_avg = LOADAVG_MX;
 457
 458 /* We don't need root privileges all the time; running under uid and gid daemon
 459  * is fine.
 460  */
 461
 462     RELINQUISH_PRIVS_ROOT(DAEMON_UID, DAEMON_GID)
 463
 464     openlog(atrun, LOG_PID, LOG_CRON);
 465
 466     opterr = 0;
 467     while((c=getopt(argc, argv, "dl:"))!= -1)
 468     {
 469         switch (c)
 470         {
 471         case 'l':
 472             if (sscanf(optarg, "%lf", &load_avg) != 1)
 473                 perr("garbled option -l");
 474             if (load_avg <= 0.)
 475                 load_avg = LOADAVG_MX;
 476             break;
 477
 478         case 'd':
 479             debug ++;
 480             break;
 481
 482         case '?':
 483         default:
 484             usage();
 485         }
 486     }
 487
 488     if (chdir(ATJOB_DIR) != 0)
 489         perr("cannot change to %s", ATJOB_DIR);
 490
 491     /* Main loop. Open spool directory for reading and look over all the
 492      * files in there. If the filename indicates that the job should be run
 493      * and the x bit is set, fork off a child which sets its user and group
 494      * id to that of the files and exec a /bin/sh which executes the shell
 495      * script. Unlink older files if they should no longer be run.  For
 496      * deletion, their r bit has to be turned on.
 497      *
 498      * Also, pick the oldest batch job to run, at most one per invocation of
 499      * atrun.
 500      */
 501     if ((spool = opendir(".")) == NULL)
 502         perr("cannot read %s", ATJOB_DIR);
 503
 504     now = time(NULL);
 505     run_batch = 0;
 506     batch_uid = (uid_t) -1;
 507     batch_gid = (gid_t) -1;
 508
 509     while ((dirent = readdir(spool)) != NULL) {
 510         if (stat(dirent->d_name,&buf) != 0)
 511             perr("cannot stat in %s", ATJOB_DIR);
 512
 513         /* We don't want directories
 514          */
 515         if (!S_ISREG(buf.st_mode))
 516             continue;
 517
 518         if (sscanf(dirent->d_name,"%c%5lx%8lx",&queue,&jobno,&ctm) != 3)
 519             continue;
 520
 521         run_time = (time_t) ctm*60;
 522
 523         if ((S_IXUSR & buf.st_mode) && (run_time <=now)) {
 524             if (isupper(queue) && (strcmp(batch_name,dirent->d_name) > 0)) {
 525                 run_batch = 1;
 526                 strlcpy(batch_name, dirent->d_name, sizeof(batch_name));
 527                 batch_uid = buf.st_uid;
 528                 batch_gid = buf.st_gid;
 529             }
 530
 531         /* The file is executable and old enough
 532          */
 533             if (islower(queue))
 534                 run_file(dirent->d_name, buf.st_uid, buf.st_gid);
 535         }
 536         /*  Delete older files
 537          */
 538         if ((run_time < now) && !(S_IXUSR & buf.st_mode) && (S_IRUSR & buf.st_mode))
 539             unlink(dirent->d_name);
 540     }
 541     /* run the single batch file, if any
 542     */
 543     if (run_batch && (gloadavg() < load_avg))
 544         run_file(batch_name, batch_uid, batch_gid);
 545
 546     closelog();
 547     exit(EXIT_SUCCESS);
 548 }
 549
 550 static void
 551 usage(void)
 552 {
 553     if (debug)
 554         fprintf(stderr, "usage: atrun [-l load_avg] [-d]\n");
 555     else
 556         syslog(LOG_ERR, "usage: atrun [-l load_avg] [-d]");
 557
 558     exit(EXIT_FAILURE);
 559 }