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  */
  27
  28 /* System Headers */
  29
  30 #include <sys/fcntl.h>
  31 #include <sys/types.h>
  32 #include <sys/stat.h>
  33 #include <sys/wait.h>
  34 #include <sys/param.h>
  35 #include <ctype.h>
  36 #include <dirent.h>
  37 #include <err.h>
  38 #include <grp.h>
  39 #include <pwd.h>
  40 #include <signal.h>
  41 #include <stdarg.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 <paths.h>
  50 #ifdef LOGIN_CAP
  51 #include <login_cap.h>
  52 #endif
  53 #ifdef PAM
  54 #include <security/pam_appl.h>
  55 #include <security/openpam.h>
  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 const char * const atrun = "atrun"; /* service name for syslog etc. */
  83 static int debug = 0;
  84
  85 void            perr(const char *fmt, ...) __printflike(1, 2);
  86 void            perrx(const char *fmt, ...) __printflike(1, 2);
  87 static void     usage(void);
  88
  89 /* Local functions */
  90 static int
  91 write_string(int fd, const char* a)
  92 {
  93     return write(fd, a, strlen(a));
  94 }
  95
  96 #undef DEBUG_FORK
  97 #ifdef DEBUG_FORK
  98 static pid_t
  99 myfork(void)
 100 {
 101         pid_t res;
 102         res = fork();
 103         if (res == 0)
 104             kill(getpid(),SIGSTOP);
 105         return res;
 106 }
 107
 108 #define fork myfork
 109 #endif
 110
 111 static void
 112 run_file(const char *filename, uid_t uid, gid_t gid)
 113 {
 114 /* Run a file by spawning off a process which redirects I/O,
 115  * spawns a subshell, then waits for it to complete and sends
 116  * mail to the user.
 117  */
 118     pid_t pid;
 119     int fd_out, fd_in;
 120     int queue;
 121     char mailbuf[MAXLOGNAME], fmt[49];
 122     char *mailname = NULL;
 123     FILE *stream;
 124     int send_mail = 0;
 125     struct stat buf, lbuf;
 126     off_t size;
 127     struct passwd *pentry;
 128     int fflags;
 129     uid_t nuid;
 130     gid_t ngid;
 131 #ifdef PAM
 132     pam_handle_t *pamh = NULL;
 133     int pam_err;
 134     struct pam_conv pamc = {
 135         .conv = openpam_nullconv,
 136         .appdata_ptr = NULL
 137     };
 138 #endif
 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 #ifdef PAM
 167     PRIV_START
 168
 169     pam_err = pam_start(atrun, pentry->pw_name, &pamc, &pamh);
 170     if (pam_err != PAM_SUCCESS)
 171         perrx("cannot start PAM: %s", pam_strerror(pamh, pam_err));
 172
 173     pam_err = pam_acct_mgmt(pamh, PAM_SILENT);
 174     /* Expired password shouldn't prevent the job from running. */
 175     if (pam_err != PAM_SUCCESS && pam_err != PAM_NEW_AUTHTOK_REQD)
 176         perrx("Account %s (userid %lu) unavailable for job %s: %s",
 177             pentry->pw_name, (unsigned long)uid,
 178             filename, pam_strerror(pamh, pam_err));
 179
 180     pam_end(pamh, pam_err);
 181
 182     PRIV_END
 183 #endif /* PAM */
 184
 185     PRIV_START
 186
 187     stream=fopen(filename, "r");
 188
 189     PRIV_END
 190
 191     if (stream == NULL)
 192         perr("cannot open input file");
 193
 194     if ((fd_in = dup(fileno(stream))) <0)
 195         perr("error duplicating input file descriptor");
 196
 197     if (fstat(fd_in, &buf) == -1)
 198         perr("error in fstat of input file descriptor");
 199
 200     if (lstat(filename, &lbuf) == -1)
 201         perr("error in fstat of input file");
 202
 203     if (S_ISLNK(lbuf.st_mode))
 204         perrx("Symbolic link encountered in job %s - aborting", filename);
 205
 206     if ((lbuf.st_dev != buf.st_dev) || (lbuf.st_ino != buf.st_ino) ||
 207         (lbuf.st_uid != buf.st_uid) || (lbuf.st_gid != buf.st_gid) ||
 208         (lbuf.st_size!=buf.st_size))
 209         perrx("Somebody changed files from under us for job %s - aborting",
 210                 filename);
 211
 212     if (buf.st_nlink > 1)
 213         perrx("Somebody is trying to run a linked script for job %s", filename);
 214
 215     if ((fflags = fcntl(fd_in, F_GETFD)) <0)
 216         perr("error in fcntl");
 217
 218     fcntl(fd_in, F_SETFD, fflags & ~FD_CLOEXEC);
 219
 220     snprintf(fmt, sizeof(fmt),
 221         "#!/bin/sh\n# atrun uid=%%u gid=%%u\n# mail %%%ds %%d",
 222                           MAXLOGNAME - 1);
 223
 224     if (fscanf(stream, fmt, &nuid, &ngid, mailbuf, &send_mail) != 4)
 225         perrx("File %s is in wrong format - aborting", filename);
 226
 227     if (mailbuf[0] == '-')
 228         perrx("Illegal mail name %s in %s", mailbuf, filename);
 229
 230     mailname = mailbuf;
 231
 232     if (nuid != uid)
 233         perrx("Job %s - userid %u does not match file uid %u",
 234                 filename, nuid, uid);
 235
 236     if (ngid != gid)
 237         perrx("Job %s - groupid %u does not match file gid %u",
 238                 filename, ngid, gid);
 239
 240     fclose(stream);
 241
 242     if (chdir(ATSPOOL_DIR) < 0)
 243         perr("cannot chdir to %s", ATSPOOL_DIR);
 244
 245     /* Create a file to hold the output of the job we are about to run.
 246      * Write the mail header.
 247      */
 248     if((fd_out=open(filename,
 249                 O_WRONLY | O_CREAT | O_EXCL, S_IWUSR | S_IRUSR)) < 0)
 250         perr("cannot create output file");
 251
 252     write_string(fd_out, "Subject: Output from your job ");
 253     write_string(fd_out, filename);
 254     write_string(fd_out, "\n\n");
 255     fstat(fd_out, &buf);
 256     size = buf.st_size;
 257
 258     close(STDIN_FILENO);
 259     close(STDOUT_FILENO);
 260     close(STDERR_FILENO);
 261
 262     pid = fork();
 263     if (pid < 0)
 264         perr("error in fork");
 265
 266     else if (pid == 0)
 267     {
 268         char *nul = NULL;
 269         char **nenvp = &nul;
 270
 271         /* Set up things for the child; we want standard input from the input file,
 272          * and standard output and error sent to our output file.
 273          */
 274
 275         if (lseek(fd_in, (off_t) 0, SEEK_SET) < 0)
 276             perr("error in lseek");
 277
 278         if (dup(fd_in) != STDIN_FILENO)
 279             perr("error in I/O redirection");
 280
 281         if (dup(fd_out) != STDOUT_FILENO)
 282             perr("error in I/O redirection");
 283
 284         if (dup(fd_out) != STDERR_FILENO)
 285             perr("error in I/O redirection");
 286
 287         close(fd_in);
 288         close(fd_out);
 289         if (chdir(ATJOB_DIR) < 0)
 290             perr("cannot chdir to %s", ATJOB_DIR);
 291
 292         queue = *filename;
 293
 294         PRIV_START
 295
 296         nice(tolower(queue) - 'a');
 297
 298 #ifdef LOGIN_CAP
 299         /*
 300          * For simplicity and safety, set all aspects of the user context
 301          * except for a selected subset:  Don't set priority, which was
 302          * set based on the queue file name according to the tradition.
 303          * Don't bother to set environment, including path vars, either
 304          * because it will be discarded anyway.  Although the job file
 305          * should set umask, preset it here just in case.
 306          */
 307         if (setusercontext(NULL, pentry, uid, LOGIN_SETALL &
 308                 ~(LOGIN_SETPRIORITY | LOGIN_SETPATH | LOGIN_SETENV)) != 0)
 309             exit(EXIT_FAILURE); /* setusercontext() logged the error */
 310 #else /* LOGIN_CAP */
 311         if (initgroups(pentry->pw_name,pentry->pw_gid))
 312             perr("cannot init group access list");
 313
 314         if (setgid(gid) < 0 || setegid(pentry->pw_gid) < 0)
 315             perr("cannot change group");
 316
 317         if (setlogin(pentry->pw_name))
 318             perr("cannot set login name");
 319
 320         if (setuid(uid) < 0 || seteuid(uid) < 0)
 321             perr("cannot set user id");
 322 #endif /* LOGIN_CAP */
 323
 324         if (chdir(pentry->pw_dir))
 325                 chdir("/");
 326
 327         if(execle("/bin/sh","sh",NULL, nenvp) != 0)
 328             perr("exec failed for /bin/sh");
 329
 330         PRIV_END
 331     }
 332     /* We're the parent.  Let's wait.
 333      */
 334     close(fd_in);
 335     close(fd_out);
 336     waitpid(pid, NULL, 0);
 337
 338     /* Send mail.  Unlink the output file first, so it is deleted after
 339      * the run.
 340      */
 341     stat(filename, &buf);
 342     if (open(filename, O_RDONLY) != STDIN_FILENO)
 343         perr("open of jobfile failed");
 344
 345     unlink(filename);
 346     if ((buf.st_size != size) || send_mail)
 347     {
 348         PRIV_START
 349
 350 #ifdef LOGIN_CAP
 351         /*
 352          * This time set full context to run the mailer.
 353          */
 354         if (setusercontext(NULL, pentry, uid, LOGIN_SETALL) != 0)
 355             exit(EXIT_FAILURE); /* setusercontext() logged the error */
 356 #else /* LOGIN_CAP */
 357         if (initgroups(pentry->pw_name,pentry->pw_gid))
 358             perr("cannot init group access list");
 359
 360         if (setgid(gid) < 0 || setegid(pentry->pw_gid) < 0)
 361             perr("cannot change group");
 362
 363         if (setlogin(pentry->pw_name))
 364             perr("cannot set login name");
 365
 366         if (setuid(uid) < 0 || seteuid(uid) < 0)
 367             perr("cannot set user id");
 368 #endif /* LOGIN_CAP */
 369
 370         if (chdir(pentry->pw_dir))
 371                 chdir("/");
 372
 373         execl(_PATH_SENDMAIL, "sendmail", "-F", "Atrun Service",
 374                         "-odi", "-oem",
 375                         mailname, NULL);
 376             perr("exec failed for mail command");
 377
 378         PRIV_END
 379     }
 380     exit(EXIT_SUCCESS);
 381 }
 382
 383 /* Global functions */
 384
 385 /* Needed in gloadavg.c */
 386 void
 387 perr(const char *fmt, ...)
 388 {
 389     const char * const fmtadd = ": %m";
 390     char nfmt[strlen(fmt) + strlen(fmtadd) + 1];
 391     va_list ap;
 392
 393     va_start(ap, fmt);
 394     if (debug)
 395     {
 396         vwarn(fmt, ap);
 397     }
 398     else
 399     {
 400         snprintf(nfmt, sizeof(nfmt), "%s%s", fmt, fmtadd);
 401         vsyslog(LOG_ERR, nfmt, ap);
 402     }
 403     va_end(ap);
 404
 405     exit(EXIT_FAILURE);
 406 }
 407
 408 void
 409 perrx(const char *fmt, ...)
 410 {
 411     va_list ap;
 412
 413     va_start(ap, fmt);
 414     if (debug)
 415         vwarnx(fmt, ap);
 416     else
 417         vsyslog(LOG_ERR, fmt, ap);
 418     va_end(ap);
 419
 420     exit(EXIT_FAILURE);
 421 }
 422
 423 int
 424 main(int argc, char *argv[])
 425 {
 426 /* Browse through  ATJOB_DIR, checking all the jobfiles wether they should
 427  * be executed and or deleted. The queue is coded into the first byte of
 428  * the job filename, the date (in minutes since Eon) as a hex number in the
 429  * following eight bytes, followed by a dot and a serial number.  A file
 430  * which has not been executed yet is denoted by its execute - bit set.
 431  * For those files which are to be executed, run_file() is called, which forks
 432  * off a child which takes care of I/O redirection, forks off another child
 433  * for execution and yet another one, optionally, for sending mail.
 434  * Files which already have run are removed during the next invocation.
 435  */
 436     DIR *spool;
 437     struct dirent *dirent;
 438     struct stat buf;
 439     unsigned long ctm;
 440     unsigned long jobno;
 441     char queue;
 442     time_t now, run_time;
 443     char batch_name[] = "Z2345678901234";
 444     uid_t batch_uid;
 445     gid_t batch_gid;
 446     int c;
 447     int run_batch;
 448     double load_avg = LOADAVG_MX;
 449
 450 /* We don't need root privileges all the time; running under uid and gid daemon
 451  * is fine.
 452  */
 453
 454     RELINQUISH_PRIVS_ROOT(DAEMON_UID, DAEMON_GID)
 455
 456     openlog(atrun, LOG_PID, LOG_CRON);
 457
 458     opterr = 0;
 459     while((c=getopt(argc, argv, "dl:"))!= -1)
 460     {
 461         switch (c)
 462         {
 463         case 'l':
 464             if (sscanf(optarg, "%lf", &load_avg) != 1)
 465                 perr("garbled option -l");
 466             if (load_avg <= 0.)
 467                 load_avg = LOADAVG_MX;
 468             break;
 469
 470         case 'd':
 471             debug ++;
 472             break;
 473
 474         case '?':
 475         default:
 476             usage();
 477         }
 478     }
 479
 480     if (chdir(ATJOB_DIR) != 0)
 481         perr("cannot change to %s", ATJOB_DIR);
 482
 483     /* Main loop. Open spool directory for reading and look over all the
 484      * files in there. If the filename indicates that the job should be run
 485      * and the x bit is set, fork off a child which sets its user and group
 486      * id to that of the files and exec a /bin/sh which executes the shell
 487      * script. Unlink older files if they should no longer be run.  For
 488      * deletion, their r bit has to be turned on.
 489      *
 490      * Also, pick the oldest batch job to run, at most one per invocation of
 491      * atrun.
 492      */
 493     if ((spool = opendir(".")) == NULL)
 494         perr("cannot read %s", ATJOB_DIR);
 495
 496     now = time(NULL);
 497     run_batch = 0;
 498     batch_uid = (uid_t) -1;
 499     batch_gid = (gid_t) -1;
 500
 501     while ((dirent = readdir(spool)) != NULL) {
 502         if (stat(dirent->d_name,&buf) != 0)
 503             perr("cannot stat in %s", ATJOB_DIR);
 504
 505         /* We don't want directories
 506          */
 507         if (!S_ISREG(buf.st_mode))
 508             continue;
 509
 510         if (sscanf(dirent->d_name,"%c%5lx%8lx",&queue,&jobno,&ctm) != 3)
 511             continue;
 512
 513         run_time = (time_t) ctm*60;
 514
 515         if ((S_IXUSR & buf.st_mode) && (run_time <=now)) {
 516             if (isupper(queue) && (strcmp(batch_name,dirent->d_name) > 0)) {
 517                 run_batch = 1;
 518                 strlcpy(batch_name, dirent->d_name, sizeof(batch_name));
 519                 batch_uid = buf.st_uid;
 520                 batch_gid = buf.st_gid;
 521             }
 522
 523         /* The file is executable and old enough
 524          */
 525             if (islower(queue))
 526                 run_file(dirent->d_name, buf.st_uid, buf.st_gid);
 527         }
 528         /*  Delete older files
 529          */
 530         if ((run_time < now) && !(S_IXUSR & buf.st_mode) && (S_IRUSR & buf.st_mode))
 531             unlink(dirent->d_name);
 532     }
 533     /* run the single batch file, if any
 534     */
 535     if (run_batch && (gloadavg() < load_avg))
 536         run_file(batch_name, batch_uid, batch_gid);
 537
 538     closelog();
 539     exit(EXIT_SUCCESS);
 540 }
 541
 542 static void
 543 usage(void)
 544 {
 545     if (debug)
 546         fprintf(stderr, "usage: atrun [-l load_avg] [-d]\n");
 547     else
 548         syslog(LOG_ERR, "usage: atrun [-l load_avg] [-d]");
 549
 550     exit(EXIT_FAILURE);
 551 }