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 1.14.2.1 2001/03/05 10:53:23 kris 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 <stddef.h>
  43 #include <stdio.h>
  44 #include <stdlib.h>
  45 #include <string.h>
  46 #include <syslog.h>
  47 #include <time.h>
  48 #include <unistd.h>
  49 #include <utmp.h>
  50 #include <paths.h>
  51
  52 #if (MAXLOGNAME-1) > UT_NAMESIZE
  53 #define LOGNAMESIZE UT_NAMESIZE
  54 #else
  55 #define LOGNAMESIZE (MAXLOGNAME-1)
  56 #endif
  57
  58 /* Local headers */
  59
  60 #include "gloadavg.h"
  61 #include "privs.h"
  62
  63 /* Macros */
  64
  65 #ifndef ATJOB_DIR
  66 #define ATJOB_DIR "/usr/spool/atjobs/"
  67 #endif
  68
  69 #ifndef ATSPOOL_DIR
  70 #define ATSPOOL_DIR "/usr/spool/atspool/"
  71 #endif
  72
  73 #ifndef LOADAVG_MX
  74 #define LOADAVG_MX 1.5
  75 #endif
  76
  77 uid_t real_uid, effective_uid;
  78 gid_t real_gid, effective_gid;
  79
  80 /* File scope variables */
  81
  82 static int debug = 0;
  83
  84 void            perr(const char *a);
  85 static void     usage(void);
  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(void)
  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     uid_t nuid;
 128     gid_t 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 __DragonFly__
 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, sizeof(fmt),
 209         "#!/bin/sh\n# atrun uid=%%ld gid=%%ld\n# mail %%%ds %%d",
 210                           LOGNAMESIZE);
 211     if (fscanf(stream, fmt, &nuid, &ngid, mailbuf, &send_mail) != 4) {
 212         syslog(LOG_ERR,"File %s is in wrong format - aborting", filename);
 213         exit(EXIT_FAILURE);
 214     }
 215     if (mailbuf[0] == '-') {
 216         syslog(LOG_ERR,"illegal mail name %s in %s",mailbuf,filename);
 217         exit(EXIT_FAILURE);
 218     }
 219     mailname = mailbuf;
 220     if (nuid != uid) {
 221         syslog(LOG_ERR,"Job %s - userid %u does not match file uid %lu",
 222                 filename, nuid, (unsigned long)uid);
 223         exit(EXIT_FAILURE);
 224     }
 225     if (ngid != gid) {
 226         syslog(LOG_ERR,"Job %s - groupid %u does not match file gid %lu",
 227                 filename, ngid, (unsigned long)gid);
 228         exit(EXIT_FAILURE);
 229     }
 230     fclose(stream);
 231     if (chdir(ATSPOOL_DIR) < 0)
 232         perr("cannot chdir to " ATSPOOL_DIR);
 233
 234     /* Create a file to hold the output of the job we are about to run.
 235      * Write the mail header.
 236      */
 237     if((fd_out=open(filename,
 238                 O_WRONLY | O_CREAT | O_EXCL, S_IWUSR | S_IRUSR)) < 0)
 239         perr("cannot create output file");
 240
 241     write_string(fd_out, "Subject: Output from your job ");
 242     write_string(fd_out, filename);
 243     write_string(fd_out, "\n\n");
 244     fstat(fd_out, &buf);
 245     size = buf.st_size;
 246
 247     close(STDIN_FILENO);
 248     close(STDOUT_FILENO);
 249     close(STDERR_FILENO);
 250
 251     pid = fork();
 252     if (pid < 0)
 253         perr("error in fork");
 254
 255     else if (pid == 0)
 256     {
 257         char *nul = NULL;
 258         char **nenvp = &nul;
 259
 260         /* Set up things for the child; we want standard input from the input file,
 261          * and standard output and error sent to our output file.
 262          */
 263
 264         if (lseek(fd_in, (off_t) 0, SEEK_SET) < 0)
 265             perr("error in lseek");
 266
 267         if (dup(fd_in) != STDIN_FILENO)
 268             perr("error in I/O redirection");
 269
 270         if (dup(fd_out) != STDOUT_FILENO)
 271             perr("error in I/O redirection");
 272
 273         if (dup(fd_out) != STDERR_FILENO)
 274             perr("error in I/O redirection");
 275
 276         close(fd_in);
 277         close(fd_out);
 278         if (chdir(ATJOB_DIR) < 0)
 279             perr("cannot chdir to " ATJOB_DIR);
 280
 281         queue = *filename;
 282
 283         PRIV_START
 284
 285         nice(tolower(queue) - 'a');
 286
 287         if (initgroups(pentry->pw_name,pentry->pw_gid))
 288             perr("cannot delete saved userids");
 289
 290         if (setgid(gid) < 0 || setegid(pentry->pw_gid) < 0)
 291             perr("cannot change group");
 292
 293         if (setlogin(pentry->pw_name))
 294             perr("cannot set login name");
 295
 296         if (setuid(uid) < 0 || seteuid(uid) < 0)
 297             perr("cannot set user id");
 298
 299         if (chdir(pentry->pw_dir))
 300                 chdir("/");
 301
 302         if(execle("/bin/sh","sh",(char *) NULL, nenvp) != 0)
 303             perr("exec failed for /bin/sh");
 304
 305         PRIV_END
 306     }
 307     /* We're the parent.  Let's wait.
 308      */
 309     close(fd_in);
 310     close(fd_out);
 311     waitpid(pid, (int *) NULL, 0);
 312
 313     /* Send mail.  Unlink the output file first, so it is deleted after
 314      * the run.
 315      */
 316     stat(filename, &buf);
 317     if (open(filename, O_RDONLY) != STDIN_FILENO)
 318         perr("open of jobfile failed");
 319
 320     unlink(filename);
 321     if ((buf.st_size != size) || send_mail)
 322     {
 323         PRIV_START
 324
 325         if (initgroups(pentry->pw_name,pentry->pw_gid))
 326             perr("cannot delete saved userids");
 327
 328         if (setgid(gid) < 0 || setegid(pentry->pw_gid) < 0)
 329             perr("cannot change group");
 330
 331         if (setlogin(pentry->pw_name))
 332             perr("cannot set login name");
 333
 334         if (setuid(uid) < 0 || seteuid(uid) < 0)
 335             perr("cannot set user id");
 336
 337         if (chdir(pentry->pw_dir))
 338                 chdir("/");
 339
 340         execl(_PATH_SENDMAIL, "sendmail", "-F", "Atrun Service",
 341                         "-odi", "-oem",
 342                         mailname, (char *) NULL);
 343             perr("exec failed for mail command");
 344
 345         PRIV_END
 346     }
 347     exit(EXIT_SUCCESS);
 348 }
 349
 350 /* Global functions */
 351
 352 /* Needed in gloadavg.c */
 353 void
 354 perr(const char *a)
 355 {
 356     if (debug)
 357     {
 358         warn("%s", a);
 359     }
 360     else
 361         syslog(LOG_ERR, "%s: %m", a);
 362
 363     exit(EXIT_FAILURE);
 364 }
 365
 366 int
 367 main(int argc, char *argv[])
 368 {
 369 /* Browse through  ATJOB_DIR, checking all the jobfiles wether they should
 370  * be executed and or deleted. The queue is coded into the first byte of
 371  * the job filename, the date (in minutes since Eon) as a hex number in the
 372  * following eight bytes, followed by a dot and a serial number.  A file
 373  * which has not been executed yet is denoted by its execute - bit set.
 374  * For those files which are to be executed, run_file() is called, which forks
 375  * off a child which takes care of I/O redirection, forks off another child
 376  * for execution and yet another one, optionally, for sending mail.
 377  * Files which already have run are removed during the next invocation.
 378  */
 379     DIR *spool;
 380     struct dirent *dirent;
 381     struct stat buf;
 382     unsigned long ctm;
 383     unsigned long jobno;
 384     char queue;
 385     time_t now, run_time;
 386     char batch_name[] = "Z2345678901234";
 387     uid_t batch_uid;
 388     gid_t batch_gid;
 389     int c;
 390     int run_batch;
 391     double load_avg = LOADAVG_MX;
 392
 393 /* We don't need root privileges all the time; running under uid and gid daemon
 394  * is fine.
 395  */
 396
 397     RELINQUISH_PRIVS_ROOT(DAEMON_UID, DAEMON_GID)
 398
 399     openlog("atrun", LOG_PID, LOG_CRON);
 400
 401     opterr = 0;
 402     while((c=getopt(argc, argv, "dl:"))!= -1)
 403     {
 404         switch (c)
 405         {
 406         case 'l':
 407             if (sscanf(optarg, "%lf", &load_avg) != 1)
 408                 perr("garbled option -l");
 409             if (load_avg <= 0.)
 410                 load_avg = LOADAVG_MX;
 411             break;
 412
 413         case 'd':
 414             debug ++;
 415             break;
 416
 417         case '?':
 418         default:
 419             usage();
 420         }
 421     }
 422
 423     if (chdir(ATJOB_DIR) != 0)
 424         perr("cannot change to " ATJOB_DIR);
 425
 426     /* Main loop. Open spool directory for reading and look over all the
 427      * files in there. If the filename indicates that the job should be run
 428      * and the x bit is set, fork off a child which sets its user and group
 429      * id to that of the files and exec a /bin/sh which executes the shell
 430      * script. Unlink older files if they should no longer be run.  For
 431      * deletion, their r bit has to be turned on.
 432      *
 433      * Also, pick the oldest batch job to run, at most one per invocation of
 434      * atrun.
 435      */
 436     if ((spool = opendir(".")) == NULL)
 437         perr("cannot read " ATJOB_DIR);
 438
 439     now = time(NULL);
 440     run_batch = 0;
 441     batch_uid = (uid_t) -1;
 442     batch_gid = (gid_t) -1;
 443
 444     while ((dirent = readdir(spool)) != NULL) {
 445         if (stat(dirent->d_name,&buf) != 0)
 446             perr("cannot stat in " ATJOB_DIR);
 447
 448         /* We don't want directories
 449          */
 450         if (!S_ISREG(buf.st_mode))
 451             continue;
 452
 453         if (sscanf(dirent->d_name,"%c%5lx%8lx",&queue,&jobno,&ctm) != 3)
 454             continue;
 455
 456         run_time = (time_t) ctm*60;
 457
 458         if ((S_IXUSR & buf.st_mode) && (run_time <=now)) {
 459             if (isupper(queue) && (strcmp(batch_name,dirent->d_name) > 0)) {
 460                 run_batch = 1;
 461                 strncpy(batch_name, dirent->d_name, sizeof(batch_name));
 462                 batch_uid = buf.st_uid;
 463                 batch_gid = buf.st_gid;
 464             }
 465
 466         /* The file is executable and old enough
 467          */
 468             if (islower(queue))
 469                 run_file(dirent->d_name, buf.st_uid, buf.st_gid);
 470         }
 471         /*  Delete older files
 472          */
 473         if ((run_time < now) && !(S_IXUSR & buf.st_mode) && (S_IRUSR & buf.st_mode))
 474             unlink(dirent->d_name);
 475     }
 476     /* run the single batch file, if any
 477     */
 478     if (run_batch && (gloadavg() < load_avg))
 479         run_file(batch_name, batch_uid, batch_gid);
 480
 481     closelog();
 482     exit(EXIT_SUCCESS);
 483 }
 484
 485 static void
 486 usage()
 487 {
 488     if (debug)
 489         fprintf(stderr, "usage: atrun [-l load_avg] [-d]\n");
 490     else
 491         syslog(LOG_ERR, "usage: atrun [-l load_avg] [-d]");
 492
 493     exit(EXIT_FAILURE);
 494 }