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
  26 #ifndef lint
  27 static const char rcsid[] =
  28   "$FreeBSD$";
  29 #endif /* not lint */
  30
  31 /* System Headers */
  32
  33 #include <sys/fcntl.h>
  34 #include <sys/file.h>
  35 #include <sys/types.h>
  36 #include <sys/stat.h>
  37 #ifdef __FreeBSD__
  38 #include <sys/sysctl.h>
  39 #endif
  40 #include <sys/wait.h>
  41 #include <sys/param.h>
  42 #include <ctype.h>
  43 #include <dirent.h>
  44 #include <err.h>
  45 #include <grp.h>
  46 #include <pwd.h>
  47 #include <signal.h>
  48 #include <stdarg.h>
  49 #include <stddef.h>
  50 #include <stdio.h>
  51 #include <stdlib.h>
  52 #include <string.h>
  53 #include <syslog.h>
  54 #include <time.h>
  55 #include <unistd.h>
  56 #ifdef __FreeBSD__
  57 #include <paths.h>
  58 #else
  59 #include <getopt.h>
  60 #endif
  61 #ifdef LOGIN_CAP
  62 #include <login_cap.h>
  63 #endif
  64 #ifdef PAM
  65 #include <security/pam_appl.h>
  66 #include <security/openpam.h>
  67 #endif
  68
  69 /* Local headers */
  70
  71 #include "gloadavg.h"
  72 #define MAIN
  73 #include "privs.h"
  74
  75 /* Macros */
  76
  77 #ifndef ATJOB_DIR
  78 #define ATJOB_DIR "/usr/spool/atjobs/"
  79 #endif
  80
  81 #ifndef ATSPOOL_DIR
  82 #define ATSPOOL_DIR "/usr/spool/atspool/"
  83 #endif
  84
  85 #ifndef LOADAVG_MX
  86 #define LOADAVG_MX 1.5
  87 #endif
  88
  89 /* File scope variables */
  90
  91 static const char * const atrun = "atrun"; /* service name for syslog etc. */
  92 static int debug = 0;
  93
  94 void perr(const char *fmt, ...);
  95 void perrx(const char *fmt, ...);
  96 static void usage(void);
  97
  98 /* Local functions */
  99 static int
 100 write_string(int fd, const char* a)
 101 {
 102     return write(fd, a, strlen(a));
 103 }
 104
 105 #undef DEBUG_FORK
 106 #ifdef DEBUG_FORK
 107 static pid_t
 108 myfork(void)
 109 {
 110         pid_t res;
 111         res = fork();
 112         if (res == 0)
 113             kill(getpid(),SIGSTOP);
 114         return res;
 115 }
 116
 117 #define fork myfork
 118 #endif
 119
 120 static void
 121 run_file(const char *filename, uid_t uid, gid_t gid)
 122 {
 123 /* Run a file by spawning off a process which redirects I/O,
 124  * spawns a subshell, then waits for it to complete and sends
 125  * mail to the user.
 126  */
 127     pid_t pid;
 128     int fd_out, fd_in;
 129     int queue;
 130     char mailbuf[MAXLOGNAME], fmt[64];
 131     char *mailname = NULL;
 132     FILE *stream;
 133     int send_mail = 0;
 134     struct stat buf, lbuf;
 135     off_t size;
 136     struct passwd *pentry;
 137     int fflags;
 138     long nuid;
 139     long ngid;
 140 #ifdef PAM
 141     pam_handle_t *pamh = NULL;
 142     int pam_err;
 143     struct pam_conv pamc = {
 144         .conv = openpam_nullconv,
 145         .appdata_ptr = NULL
 146     };
 147 #endif
 148
 149     PRIV_START
 150
 151     if (chmod(filename, S_IRUSR) != 0)
 152     {
 153         perr("cannot change file permissions");
 154     }
 155
 156     PRIV_END
 157
 158     pid = fork();
 159     if (pid == -1)
 160         perr("cannot fork");
 161
 162     else if (pid != 0)
 163         return;
 164
 165     /* Let's see who we mail to.  Hopefully, we can read it from
 166      * the command file; if not, send it to the owner, or, failing that,
 167      * to root.
 168      */
 169
 170     pentry = getpwuid(uid);
 171     if (pentry == NULL)
 172         perrx("Userid %lu not found - aborting job %s",
 173                 (unsigned long) uid, filename);
 174
 175 #ifdef PAM
 176     PRIV_START
 177
 178     pam_err = pam_start(atrun, pentry->pw_name, &pamc, &pamh);
 179     if (pam_err != PAM_SUCCESS)
 180         perrx("cannot start PAM: %s", pam_strerror(pamh, pam_err));
 181
 182     pam_err = pam_acct_mgmt(pamh, PAM_SILENT);
 183     /* Expired password shouldn't prevent the job from running. */
 184     if (pam_err != PAM_SUCCESS && pam_err != PAM_NEW_AUTHTOK_REQD)
 185         perrx("Account %s (userid %lu) unavailable for job %s: %s",
 186             pentry->pw_name, (unsigned long)uid,
 187             filename, pam_strerror(pamh, pam_err));
 188
 189     pam_end(pamh, pam_err);
 190
 191     PRIV_END
 192 #endif /* PAM */
 193
 194     PRIV_START
 195
 196     stream=fopen(filename, "r");
 197
 198     PRIV_END
 199
 200     if (stream == NULL)
 201         perr("cannot open input file %s", filename);
 202
 203     if ((fd_in = dup(fileno(stream))) <0)
 204         perr("error duplicating input file descriptor");
 205
 206     if (fstat(fd_in, &buf) == -1)
 207         perr("error in fstat of input file descriptor");
 208
 209     if (lstat(filename, &lbuf) == -1)
 210         perr("error in fstat of input file");
 211
 212     if (S_ISLNK(lbuf.st_mode))
 213         perrx("Symbolic link encountered in job %s - aborting", filename);
 214
 215     if ((lbuf.st_dev != buf.st_dev) || (lbuf.st_ino != buf.st_ino) ||
 216         (lbuf.st_uid != buf.st_uid) || (lbuf.st_gid != buf.st_gid) ||
 217         (lbuf.st_size!=buf.st_size))
 218         perrx("Somebody changed files from under us for job %s - aborting",
 219                 filename);
 220
 221     if (buf.st_nlink > 1)
 222         perrx("Somebody is trying to run a linked script for job %s", filename);
 223
 224     if ((fflags = fcntl(fd_in, F_GETFD)) <0)
 225         perr("error in fcntl");
 226
 227     fcntl(fd_in, F_SETFD, fflags & ~FD_CLOEXEC);
 228
 229     snprintf(fmt, sizeof(fmt),
 230         "#!/bin/sh\n# atrun uid=%%ld gid=%%ld\n# mail %%%ds %%d",
 231                           MAXLOGNAME - 1);
 232
 233     if (fscanf(stream, fmt, &nuid, &ngid, mailbuf, &send_mail) != 4)
 234         perrx("File %s is in wrong format - aborting", filename);
 235
 236     if (mailbuf[0] == '-')
 237         perrx("Illegal mail name %s in %s", mailbuf, filename);
 238
 239     mailname = mailbuf;
 240
 241     if (nuid != uid)
 242         perrx("Job %s - userid %ld does not match file uid %lu",
 243                 filename, nuid, (unsigned long)uid);
 244
 245     if (ngid != gid)
 246         perrx("Job %s - groupid %ld does not match file gid %lu",
 247                 filename, ngid, (unsigned long)gid);
 248
 249     fclose(stream);
 250
 251     if (chdir(ATSPOOL_DIR) < 0)
 252         perr("cannot chdir to %s", ATSPOOL_DIR);
 253
 254     /* Create a file to hold the output of the job we are about to run.
 255      * Write the mail header.
 256      */
 257     if((fd_out=open(filename,
 258                 O_WRONLY | O_CREAT | O_EXCL, S_IWUSR | S_IRUSR)) < 0)
 259         perr("cannot create output file");
 260
 261     write_string(fd_out, "Subject: Output from your job ");
 262     write_string(fd_out, filename);
 263     write_string(fd_out, "\n\n");
 264     fstat(fd_out, &buf);
 265     size = buf.st_size;
 266
 267     close(STDIN_FILENO);
 268     close(STDOUT_FILENO);
 269     close(STDERR_FILENO);
 270
 271     pid = fork();
 272     if (pid < 0)
 273         perr("error in fork");
 274
 275     else if (pid == 0)
 276     {
 277         char *nul = NULL;
 278         char **nenvp = &nul;
 279
 280         /* Set up things for the child; we want standard input from the input file,
 281          * and standard output and error sent to our output file.
 282          */
 283
 284         if (lseek(fd_in, (off_t) 0, SEEK_SET) < 0)
 285             perr("error in lseek");
 286
 287         if (dup(fd_in) != STDIN_FILENO)
 288             perr("error in I/O redirection");
 289
 290         if (dup(fd_out) != STDOUT_FILENO)
 291             perr("error in I/O redirection");
 292
 293         if (dup(fd_out) != STDERR_FILENO)
 294             perr("error in I/O redirection");
 295
 296         close(fd_in);
 297         close(fd_out);
 298         if (chdir(ATJOB_DIR) < 0)
 299             perr("cannot chdir to %s", ATJOB_DIR);
 300
 301         queue = *filename;
 302
 303         PRIV_START
 304
 305         nice(tolower(queue) - 'a');
 306
 307 #ifdef LOGIN_CAP
 308         /*
 309          * For simplicity and safety, set all aspects of the user context
 310          * except for a selected subset:  Don't set priority, which was
 311          * set based on the queue file name according to the tradition.
 312          * Don't bother to set environment, including path vars, either
 313          * because it will be discarded anyway.  Although the job file
 314          * should set umask, preset it here just in case.
 315          */
 316         if (setusercontext(NULL, pentry, uid, LOGIN_SETALL &
 317                 ~(LOGIN_SETPRIORITY | LOGIN_SETPATH | LOGIN_SETENV)) != 0)
 318             exit(EXIT_FAILURE); /* setusercontext() logged the error */
 319 #else /* LOGIN_CAP */
 320         if (initgroups(pentry->pw_name,pentry->pw_gid))
 321             perr("cannot init group access list");
 322
 323         if (setgid(gid) < 0 || setegid(pentry->pw_gid) < 0)
 324             perr("cannot change group");
 325
 326         if (setlogin(pentry->pw_name))
 327             perr("cannot set login name");
 328
 329         if (setuid(uid) < 0 || seteuid(uid) < 0)
 330             perr("cannot set user id");
 331 #endif /* LOGIN_CAP */
 332
 333         if (chdir(pentry->pw_dir))
 334                 chdir("/");
 335
 336         if(execle("/bin/sh","sh",(char *) NULL, nenvp) != 0)
 337             perr("exec failed for /bin/sh");
 338
 339         PRIV_END
 340     }
 341     /* We're the parent.  Let's wait.
 342      */
 343     close(fd_in);
 344     close(fd_out);
 345     waitpid(pid, (int *) NULL, 0);
 346
 347     /* Send mail.  Unlink the output file first, so it is deleted after
 348      * the run.
 349      */
 350     stat(filename, &buf);
 351     if (open(filename, O_RDONLY) != STDIN_FILENO)
 352         perr("open of jobfile failed");
 353
 354     unlink(filename);
 355     if ((buf.st_size != size) || send_mail)
 356     {
 357         PRIV_START
 358
 359 #ifdef LOGIN_CAP
 360         /*
 361          * This time set full context to run the mailer.
 362          */
 363         if (setusercontext(NULL, pentry, uid, LOGIN_SETALL) != 0)
 364             exit(EXIT_FAILURE); /* setusercontext() logged the error */
 365 #else /* LOGIN_CAP */
 366         if (initgroups(pentry->pw_name,pentry->pw_gid))
 367             perr("cannot init group access list");
 368
 369         if (setgid(gid) < 0 || setegid(pentry->pw_gid) < 0)
 370             perr("cannot change group");
 371
 372         if (setlogin(pentry->pw_name))
 373             perr("cannot set login name");
 374
 375         if (setuid(uid) < 0 || seteuid(uid) < 0)
 376             perr("cannot set user id");
 377 #endif /* LOGIN_CAP */
 378
 379         if (chdir(pentry->pw_dir))
 380                 chdir("/");
 381
 382 #ifdef __FreeBSD__
 383         execl(_PATH_SENDMAIL, "sendmail", "-F", "Atrun Service",
 384                         "-odi", "-oem",
 385                         mailname, (char *) NULL);
 386 #else
 387         execl(MAIL_CMD, MAIL_CMD, mailname, (char *) NULL);
 388 #endif
 389             perr("exec failed for mail command");
 390
 391         PRIV_END
 392     }
 393     exit(EXIT_SUCCESS);
 394 }
 395
 396 /* Global functions */
 397
 398 /* Needed in gloadavg.c */
 399 void
 400 perr(const char *fmt, ...)
 401 {
 402     const char * const fmtadd = ": %m";
 403     char nfmt[strlen(fmt) + strlen(fmtadd) + 1];
 404     va_list ap;
 405
 406     va_start(ap, fmt);
 407     if (debug)
 408     {
 409         vwarn(fmt, ap);
 410     }
 411     else
 412     {
 413         snprintf(nfmt, sizeof(nfmt), "%s%s", fmt, fmtadd);
 414         vsyslog(LOG_ERR, nfmt, ap);
 415     }
 416     va_end(ap);
 417
 418     exit(EXIT_FAILURE);
 419 }
 420
 421 void
 422 perrx(const char *fmt, ...)
 423 {
 424     va_list ap;
 425
 426     va_start(ap, fmt);
 427     if (debug)
 428         vwarnx(fmt, ap);
 429     else
 430         vsyslog(LOG_ERR, fmt, ap);
 431     va_end(ap);
 432
 433     exit(EXIT_FAILURE);
 434 }
 435
 436 int
 437 main(int argc, char *argv[])
 438 {
 439 /* Browse through  ATJOB_DIR, checking all the jobfiles wether they should
 440  * be executed and or deleted. The queue is coded into the first byte of
 441  * the job filename, the date (in minutes since Eon) as a hex number in the
 442  * following eight bytes, followed by a dot and a serial number.  A file
 443  * which has not been executed yet is denoted by its execute - bit set.
 444  * For those files which are to be executed, run_file() is called, which forks
 445  * off a child which takes care of I/O redirection, forks off another child
 446  * for execution and yet another one, optionally, for sending mail.
 447  * Files which already have run are removed during the next invocation.
 448  */
 449     DIR *spool;
 450     struct dirent *dirent;
 451     struct stat buf;
 452     unsigned long ctm;
 453     unsigned long jobno;
 454     char queue;
 455     time_t now, run_time;
 456     char batch_name[] = "Z2345678901234";
 457     uid_t batch_uid;
 458     gid_t batch_gid;
 459     int c;
 460     int run_batch;
 461 #ifdef __FreeBSD__
 462     size_t ncpusz;
 463     double load_avg = -1;
 464     int ncpu;
 465 #else
 466     double load_avg = LOADAVG_MX;
 467 #endif
 468
 469 /* We don't need root privileges all the time; running under uid and gid daemon
 470  * is fine.
 471  */
 472
 473     RELINQUISH_PRIVS_ROOT(DAEMON_UID, DAEMON_GID)
 474
 475     openlog(atrun, LOG_PID, LOG_CRON);
 476
 477     opterr = 0;
 478     while((c=getopt(argc, argv, "dl:"))!= -1)
 479     {
 480         switch (c)
 481         {
 482         case 'l':
 483             if (sscanf(optarg, "%lf", &load_avg) != 1)
 484                 perr("garbled option -l");
 485 #ifndef __FreeBSD__
 486             if (load_avg <= 0.)
 487                 load_avg = LOADAVG_MX;
 488 #endif
 489             break;
 490
 491         case 'd':
 492             debug ++;
 493             break;
 494
 495         case '?':
 496         default:
 497             usage();
 498         }
 499     }
 500
 501     if (chdir(ATJOB_DIR) != 0)
 502         perr("cannot change to %s", ATJOB_DIR);
 503
 504 #ifdef __FreeBSD__
 505     if (load_avg <= 0.) {
 506         ncpusz = sizeof(size_t);
 507         if (sysctlbyname("hw.ncpu", &ncpu, &ncpusz, NULL, 0) < 0)
 508                 ncpu = 1;
 509         load_avg = LOADAVG_MX * ncpu;
 510     }
 511 #endif
 512
 513     /* Main loop. Open spool directory for reading and look over all the
 514      * files in there. If the filename indicates that the job should be run
 515      * and the x bit is set, fork off a child which sets its user and group
 516      * id to that of the files and exec a /bin/sh which executes the shell
 517      * script. Unlink older files if they should no longer be run.  For
 518      * deletion, their r bit has to be turned on.
 519      *
 520      * Also, pick the oldest batch job to run, at most one per invocation of
 521      * atrun.
 522      */
 523     if ((spool = opendir(".")) == NULL)
 524         perr("cannot read %s", ATJOB_DIR);
 525
 526     if (flock(dirfd(spool), LOCK_EX) == -1)
 527         perr("cannot lock %s", ATJOB_DIR);
 528
 529     now = time(NULL);
 530     run_batch = 0;
 531     batch_uid = (uid_t) -1;
 532     batch_gid = (gid_t) -1;
 533
 534     while ((dirent = readdir(spool)) != NULL) {
 535         if (stat(dirent->d_name,&buf) != 0)
 536             perr("cannot stat in %s", ATJOB_DIR);
 537
 538         /* We don't want directories
 539          */
 540         if (!S_ISREG(buf.st_mode))
 541             continue;
 542
 543         if (sscanf(dirent->d_name,"%c%5lx%8lx",&queue,&jobno,&ctm) != 3)
 544             continue;
 545
 546         run_time = (time_t) ctm*60;
 547
 548         if ((S_IXUSR & buf.st_mode) && (run_time <=now)) {
 549             if (isupper(queue) && (strcmp(batch_name,dirent->d_name) > 0)) {
 550                 run_batch = 1;
 551                 strlcpy(batch_name, dirent->d_name, sizeof(batch_name));
 552                 batch_uid = buf.st_uid;
 553                 batch_gid = buf.st_gid;
 554             }
 555
 556         /* The file is executable and old enough
 557          */
 558             if (islower(queue))
 559                 run_file(dirent->d_name, buf.st_uid, buf.st_gid);
 560         }
 561         /*  Delete older files
 562          */
 563         if ((run_time < now) && !(S_IXUSR & buf.st_mode) && (S_IRUSR & buf.st_mode))
 564             unlink(dirent->d_name);
 565     }
 566     /* run the single batch file, if any
 567     */
 568     if (run_batch && (gloadavg() < load_avg))
 569         run_file(batch_name, batch_uid, batch_gid);
 570
 571     if (flock(dirfd(spool), LOCK_UN) == -1)
 572         perr("cannot unlock %s", ATJOB_DIR);
 573
 574     if (closedir(spool) == -1)
 575         perr("cannot closedir %s", ATJOB_DIR);
 576
 577     closelog();
 578     exit(EXIT_SUCCESS);
 579 }
 580
 581 static void
 582 usage(void)
 583 {
 584     if (debug)
 585         fprintf(stderr, "usage: atrun [-l load_avg] [-d]\n");
 586     else
 587         syslog(LOG_ERR, "usage: atrun [-l load_avg] [-d]");
 588
 589     exit(EXIT_FAILURE);
 590 }