atrun.tproj/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: src/libexec/atrun/atrun.c,v 1.18 2004/07/11 17:37:32 stefanf Exp $";
  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 #if 1
  53 #include <paths.h>
  54 #else
  55 #include <getopt.h>
  56 #endif
  57
  58 #define LOGNAMESIZE (MAXLOGNAME-1)
  59
  60 /* Local headers */
  61
  62 #define MAIN
  63 #include "privs.h"
  64 #include "pathnames.h"
  65 /* Macros */
  66
  67 #ifndef ATJOB_DIR
  68 #define ATJOB_DIR _PATH_ATJOBS
  69 #endif
  70
  71 #ifndef ATSPOOL_DIR
  72 #define ATSPOOL_DIR _PATH_ATSPOOL
  73 #endif
  74
  75 #ifndef LOADAVG_MX
  76 #define LOADAVG_MX 1.5
  77 #endif
  78
  79 /* File scope variables */
  80
  81 static int debug = 0;
  82
  83 void perr(const char *a);
  84 static void usage(void);
  85
  86 /* Local functions */
  87 static int
  88 write_string(int fd, const char* a)
  89 {
  90     return write(fd, a, strlen(a));
  91 }
  92
  93 #undef DEBUG_FORK
  94 #ifdef DEBUG_FORK
  95 static pid_t
  96 myfork(void)
  97 {
  98         pid_t res;
  99         res = fork();
 100         if (res == 0)
 101             kill(getpid(),SIGSTOP);
 102         return res;
 103 }
 104
 105 #define fork myfork
 106 #endif
 107
 108 static void
 109 run_file(const char *filename, uid_t uid, gid_t gid)
 110 {
 111 /* Run a file by spawning off a process which redirects I/O,
 112  * spawns a subshell, then waits for it to complete and sends
 113  * mail to the user.
 114  */
 115     pid_t pid;
 116     int fd_out, fd_in;
 117     int queue;
 118     char mailbuf[LOGNAMESIZE + 1];
 119     char *fmt = NULL;
 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     long nuid;
 128     long 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 __FreeBSD__
 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     asprintf(&fmt, "%s%d%s",
 209              "#!/bin/sh\n# atrun uid=%ld gid=%ld\n# mail %",
 210              LOGNAMESIZE,
 211              "s %d");
 212     if (fscanf(stream, fmt, &nuid, &ngid, mailbuf, &send_mail) != 4) {
 213         syslog(LOG_ERR,"File %s is in wrong format - aborting", filename);
 214         exit(EXIT_FAILURE);
 215     }
 216     free(fmt);
 217     if (mailbuf[0] == '-') {
 218         syslog(LOG_ERR,"illegal mail name %s in %s",mailbuf,filename);
 219         exit(EXIT_FAILURE);
 220     }
 221     mailname = mailbuf;
 222     if (nuid != uid) {
 223         syslog(LOG_ERR,"Job %s - userid %ld does not match file uid %lu",
 224                 filename, nuid, (unsigned long)uid);
 225         exit(EXIT_FAILURE);
 226     }
 227     if (ngid != gid) {
 228         syslog(LOG_ERR,"Job %s - groupid %ld does not match file gid %lu",
 229                 filename, ngid, (unsigned long)gid);
 230         exit(EXIT_FAILURE);
 231     }
 232     fclose(stream);
 233     if (chdir(ATSPOOL_DIR) < 0)
 234         perr("cannot chdir to " ATSPOOL_DIR);
 235
 236     /* Create a file to hold the output of the job we are about to run.
 237      * Write the mail header.
 238      */
 239     if((fd_out=open(filename,
 240                 O_WRONLY | O_CREAT | O_EXCL, S_IWUSR | S_IRUSR)) < 0)
 241         perr("cannot create output file");
 242
 243     write_string(fd_out, "Subject: Output from your job ");
 244     write_string(fd_out, filename);
 245     write_string(fd_out, "\n\n");
 246     fstat(fd_out, &buf);
 247     size = buf.st_size;
 248
 249     close(STDIN_FILENO);
 250     close(STDOUT_FILENO);
 251     close(STDERR_FILENO);
 252
 253     pid = fork();
 254     if (pid < 0)
 255         perr("error in fork");
 256
 257     else if (pid == 0)
 258     {
 259         char *nul = NULL;
 260         char **nenvp = &nul;
 261
 262         /* Set up things for the child; we want standard input from the input file,
 263          * and standard output and error sent to our output file.
 264          */
 265
 266         if (lseek(fd_in, (off_t) 0, SEEK_SET) < 0)
 267             perr("error in lseek");
 268
 269         if (dup(fd_in) != STDIN_FILENO)
 270             perr("error in I/O redirection");
 271
 272         if (dup(fd_out) != STDOUT_FILENO)
 273             perr("error in I/O redirection");
 274
 275         if (dup(fd_out) != STDERR_FILENO)
 276             perr("error in I/O redirection");
 277
 278         close(fd_in);
 279         close(fd_out);
 280         if (chdir(ATJOB_DIR) < 0)
 281             perr("cannot chdir to " ATJOB_DIR);
 282
 283         queue = *filename;
 284
 285         PRIV_START
 286
 287         nice(tolower(queue) - 'a');
 288
 289         if (initgroups(pentry->pw_name,pentry->pw_gid))
 290             perr("cannot delete saved userids");
 291
 292         if (setgid(gid) < 0 || setegid(pentry->pw_gid) < 0)
 293             perr("cannot change group");
 294
 295         if (setlogin(pentry->pw_name))
 296             perr("cannot set login name");
 297
 298         if (setuid(uid) < 0 || seteuid(uid) < 0)
 299             perr("cannot set user id");
 300
 301         if (chdir(pentry->pw_dir))
 302                 chdir("/");
 303
 304         if(execle("/bin/sh","sh",(char *) NULL, nenvp) != 0)
 305             perr("exec failed for /bin/sh");
 306
 307         PRIV_END
 308     }
 309     /* We're the parent.  Let's wait.
 310      */
 311     close(fd_in);
 312     close(fd_out);
 313     waitpid(pid, (int *) NULL, 0);
 314
 315     /* Send mail.  Unlink the output file first, so it is deleted after
 316      * the run.
 317      */
 318     stat(filename, &buf);
 319     if (open(filename, O_RDONLY) != STDIN_FILENO)
 320         perr("open of jobfile failed");
 321
 322     unlink(filename);
 323     if ((buf.st_size != size) || send_mail)
 324     {
 325         PRIV_START
 326
 327         if (initgroups(pentry->pw_name,pentry->pw_gid))
 328             perr("cannot delete saved userids");
 329
 330         if (setgid(gid) < 0 || setegid(pentry->pw_gid) < 0)
 331             perr("cannot change group");
 332
 333         if (setlogin(pentry->pw_name))
 334             perr("cannot set login name");
 335
 336         if (setuid(uid) < 0 || seteuid(uid) < 0)
 337             perr("cannot set user id");
 338
 339         if (chdir(pentry->pw_dir))
 340                 chdir("/");
 341
 342 #if 1
 343         execl(_PATH_SENDMAIL, "sendmail", "-F", "Atrun Service",
 344                         "-odi", "-oem",
 345                         mailname, (char *) NULL);
 346 #else
 347         execl(MAIL_CMD, MAIL_CMD, mailname, (char *) NULL);
 348 #endif
 349             perr("exec failed for mail command");
 350
 351         PRIV_END
 352     }
 353     exit(EXIT_SUCCESS);
 354 }
 355
 356 /* Global functions */
 357
 358 /* Needed in gloadavg.c */
 359 void
 360 perr(const char *a)
 361 {
 362     if (debug)
 363     {
 364         warn("%s", a);
 365     }
 366     else
 367         syslog(LOG_ERR, "%s: %m", a);
 368
 369     exit(EXIT_FAILURE);
 370 }
 371
 372 int
 373 main(int argc, char *argv[])
 374 {
 375 /* Browse through  ATJOB_DIR, checking all the jobfiles wether they should
 376  * be executed and or deleted. The queue is coded into the first byte of
 377  * the job filename, the date (in minutes since Eon) as a hex number in the
 378  * following eight bytes, followed by a dot and a serial number.  A file
 379  * which has not been executed yet is denoted by its execute - bit set.
 380  * For those files which are to be executed, run_file() is called, which forks
 381  * off a child which takes care of I/O redirection, forks off another child
 382  * for execution and yet another one, optionally, for sending mail.
 383  * Files which already have run are removed during the next invocation.
 384  */
 385     DIR *spool;
 386     struct dirent *dirent;
 387     struct stat buf;
 388     unsigned long ctm;
 389     unsigned long jobno;
 390     char queue;
 391     time_t now, run_time;
 392     char batch_name[] = "Z2345678901234";
 393     uid_t batch_uid;
 394     gid_t batch_gid;
 395     int c;
 396     int run_batch;
 397     double load_avg = LOADAVG_MX, la;
 398
 399 /* We don't need root privileges all the time; running under uid and gid daemon
 400  * is fine.
 401  */
 402
 403     RELINQUISH_PRIVS_ROOT(DAEMON_UID, DAEMON_GID)
 404
 405     openlog("atrun", LOG_PID, LOG_CRON);
 406
 407     opterr = 0;
 408     while((c=getopt(argc, argv, "dl:"))!= -1)
 409     {
 410         switch (c)
 411         {
 412         case 'l':
 413             if (sscanf(optarg, "%lf", &load_avg) != 1)
 414                 perr("garbled option -l");
 415             if (load_avg <= 0.)
 416                 load_avg = LOADAVG_MX;
 417             break;
 418
 419         case 'd':
 420             debug ++;
 421             break;
 422
 423         case '?':
 424         default:
 425             usage();
 426         }
 427     }
 428
 429     if (chdir(ATJOB_DIR) != 0)
 430         perr("cannot change to " ATJOB_DIR);
 431
 432     /* Main loop. Open spool directory for reading and look over all the
 433      * files in there. If the filename indicates that the job should be run
 434      * and the x bit is set, fork off a child which sets its user and group
 435      * id to that of the files and exec a /bin/sh which executes the shell
 436      * script. Unlink older files if they should no longer be run.  For
 437      * deletion, their r bit has to be turned on.
 438      *
 439      * Also, pick the oldest batch job to run, at most one per invocation of
 440      * atrun.
 441      */
 442     if ((spool = opendir(".")) == NULL)
 443         perr("cannot read " ATJOB_DIR);
 444
 445     now = time(NULL);
 446     run_batch = 0;
 447     batch_uid = (uid_t) -1;
 448     batch_gid = (gid_t) -1;
 449
 450     while ((dirent = readdir(spool)) != NULL) {
 451         if (stat(dirent->d_name,&buf) != 0)
 452             perr("cannot stat in " ATJOB_DIR);
 453
 454         /* We don't want directories
 455          */
 456         if (!S_ISREG(buf.st_mode))
 457             continue;
 458
 459         if (sscanf(dirent->d_name,"%c%5lx%8lx",&queue,&jobno,&ctm) != 3)
 460             continue;
 461
 462         run_time = (time_t) ctm*60;
 463
 464         if ((S_IXUSR & buf.st_mode) && (run_time <=now)) {
 465             if (isupper(queue) && (strcmp(batch_name,dirent->d_name) > 0)) {
 466                 run_batch = 1;
 467                 strncpy(batch_name, dirent->d_name, sizeof(batch_name));
 468                 batch_uid = buf.st_uid;
 469                 batch_gid = buf.st_gid;
 470             }
 471
 472         /* The file is executable and old enough
 473          */
 474             if (islower(queue))
 475                 run_file(dirent->d_name, buf.st_uid, buf.st_gid);
 476         }
 477         /*  Delete older files
 478          */
 479         if ((run_time < now) && !(S_IXUSR & buf.st_mode) && (S_IRUSR & buf.st_mode))
 480             unlink(dirent->d_name);
 481     }
 482     /* run the single batch file, if any
 483     */
 484     if (run_batch && (getloadavg(&la, 1) == 1) && la < load_avg)
 485         run_file(batch_name, batch_uid, batch_gid);
 486
 487     closelog();
 488     exit(EXIT_SUCCESS);
 489 }
 490
 491 static void
 492 usage(void)
 493 {
 494     if (debug)
 495         fprintf(stderr, "usage: atrun [-l load_avg] [-d]\n");
 496     else
 497         syslog(LOG_ERR, "usage: atrun [-l load_avg] [-d]");
 498
 499     exit(EXIT_FAILURE);
 500 }