1 /*-
2 * atrun.c - run jobs queued by at; run with root privileges.
3 *
4 * SPDX-License-Identifier: BSD-2-Clause
5 *
6 * Copyright (C) 1993, 1994 Thomas Koenig
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. The name of the author(s) may not be used to endorse or promote
14 * products derived from this software without specific prior written
15 * permission.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR(S) ``AS IS'' AND ANY EXPRESS OR
18 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
19 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
20 * IN NO EVENT SHALL THE AUTHOR(S) BE LIABLE FOR ANY DIRECT, INDIRECT,
21 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
22 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24 * THEORY OF LIABILITY, WETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
26 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27 */
28
29 /* System Headers */
30
31 #include <sys/fcntl.h>
32 #include <sys/file.h>
33 #include <sys/types.h>
34 #include <sys/stat.h>
35 #ifdef __FreeBSD__
36 #include <sys/sysctl.h>
37 #endif
38 #include <sys/wait.h>
39 #include <sys/param.h>
40 #include <ctype.h>
41 #include <dirent.h>
42 #include <err.h>
43 #include <grp.h>
44 #include <pwd.h>
45 #include <signal.h>
46 #include <stdarg.h>
47 #include <stddef.h>
48 #include <stdio.h>
49 #include <stdlib.h>
50 #include <string.h>
51 #include <syslog.h>
52 #include <time.h>
53 #include <unistd.h>
54 #ifdef __FreeBSD__
55 #include <paths.h>
56 #else
57 #include <getopt.h>
58 #endif
59 #ifdef LOGIN_CAP
60 #include <login_cap.h>
61 #endif
62 #ifdef PAM
63 #include <security/pam_appl.h>
64 #include <security/openpam.h>
65 #endif
66
67 /* Local headers */
68
69 #include "gloadavg.h"
70 #define MAIN
71 #include "privs.h"
72
73 /* Macros */
74
75 #ifndef ATJOB_DIR
76 #define ATJOB_DIR "/usr/spool/atjobs/"
77 #endif
78
79 #ifndef ATSPOOL_DIR
80 #define ATSPOOL_DIR "/usr/spool/atspool/"
81 #endif
82
83 #ifndef LOADAVG_MX
84 #define LOADAVG_MX 1.5
85 #endif
86
87 /* File scope variables */
88
89 static const char * const atrun = "atrun"; /* service name for syslog etc. */
90 static int debug = 0;
91
92 void perr(const char *fmt, ...);
93 void perrx(const char *fmt, ...);
94 static void usage(void) __dead2;
95
96 /* Local functions */
97 static int
write_string(int fd,const char * a)98 write_string(int fd, const char* a)
99 {
100 return write(fd, a, strlen(a));
101 }
102
103 #undef DEBUG_FORK
104 #ifdef DEBUG_FORK
105 static pid_t
myfork(void)106 myfork(void)
107 {
108 pid_t res;
109 res = fork();
110 if (res == 0)
111 kill(getpid(),SIGSTOP);
112 return res;
113 }
114
115 #define fork myfork
116 #endif
117
118 static void
run_file(const char * filename,uid_t uid,gid_t gid)119 run_file(const char *filename, uid_t uid, gid_t gid)
120 {
121 /* Run a file by spawning off a process which redirects I/O,
122 * spawns a subshell, then waits for it to complete and sends
123 * mail to the user.
124 */
125 pid_t pid;
126 int fd_out, fd_in;
127 int queue;
128 char mailbuf[MAXLOGNAME], fmt[64];
129 char *mailname = NULL;
130 FILE *stream;
131 int send_mail = 0;
132 struct stat buf, lbuf;
133 off_t size;
134 struct passwd *pentry;
135 int fflags;
136 long nuid;
137 long ngid;
138 #ifdef PAM
139 pam_handle_t *pamh = NULL;
140 int pam_err;
141 struct pam_conv pamc = {
142 .conv = openpam_nullconv,
143 .appdata_ptr = NULL
144 };
145 #endif
146
147 PRIV_START
148
149 if (chmod(filename, S_IRUSR) != 0)
150 {
151 perr("cannot change file permissions");
152 }
153
154 PRIV_END
155
156 pid = fork();
157 if (pid == -1)
158 perr("cannot fork");
159
160 else if (pid != 0)
161 return;
162
163 /* Let's see who we mail to. Hopefully, we can read it from
164 * the command file; if not, send it to the owner, or, failing that,
165 * to root.
166 */
167
168 pentry = getpwuid(uid);
169 if (pentry == NULL)
170 perrx("Userid %lu not found - aborting job %s",
171 (unsigned long) uid, filename);
172
173 #ifdef PAM
174 PRIV_START
175
176 pam_err = pam_start(atrun, pentry->pw_name, &pamc, &pamh);
177 if (pam_err != PAM_SUCCESS)
178 perrx("cannot start PAM: %s", pam_strerror(pamh, pam_err));
179
180 pam_err = pam_acct_mgmt(pamh, PAM_SILENT);
181 /* Expired password shouldn't prevent the job from running. */
182 if (pam_err != PAM_SUCCESS && pam_err != PAM_NEW_AUTHTOK_REQD)
183 perrx("Account %s (userid %lu) unavailable for job %s: %s",
184 pentry->pw_name, (unsigned long)uid,
185 filename, pam_strerror(pamh, pam_err));
186
187 pam_end(pamh, pam_err);
188
189 PRIV_END
190 #endif /* PAM */
191
192 PRIV_START
193
194 stream=fopen(filename, "r");
195
196 PRIV_END
197
198 if (stream == NULL)
199 perr("cannot open input file %s", filename);
200
201 if ((fd_in = dup(fileno(stream))) <0)
202 perr("error duplicating input file descriptor");
203
204 if (fstat(fd_in, &buf) == -1)
205 perr("error in fstat of input file descriptor");
206
207 if (lstat(filename, &lbuf) == -1)
208 perr("error in fstat of input file");
209
210 if (S_ISLNK(lbuf.st_mode))
211 perrx("Symbolic link encountered in job %s - aborting", filename);
212
213 if ((lbuf.st_dev != buf.st_dev) || (lbuf.st_ino != buf.st_ino) ||
214 (lbuf.st_uid != buf.st_uid) || (lbuf.st_gid != buf.st_gid) ||
215 (lbuf.st_size!=buf.st_size))
216 perrx("Somebody changed files from under us for job %s - aborting",
217 filename);
218
219 if (buf.st_nlink > 1)
220 perrx("Somebody is trying to run a linked script for job %s", filename);
221
222 if ((fflags = fcntl(fd_in, F_GETFD)) <0)
223 perr("error in fcntl");
224
225 fcntl(fd_in, F_SETFD, fflags & ~FD_CLOEXEC);
226
227 snprintf(fmt, sizeof(fmt),
228 "#!/bin/sh\n# atrun uid=%%ld gid=%%ld\n# mail %%%ds %%d",
229 MAXLOGNAME - 1);
230
231 if (fscanf(stream, fmt, &nuid, &ngid, mailbuf, &send_mail) != 4)
232 perrx("File %s is in wrong format - aborting", filename);
233
234 if (mailbuf[0] == '-')
235 perrx("Illegal mail name %s in %s", mailbuf, filename);
236
237 mailname = mailbuf;
238
239 if (nuid != uid)
240 perrx("Job %s - userid %ld does not match file uid %lu",
241 filename, nuid, (unsigned long)uid);
242
243 if (ngid != gid)
244 perrx("Job %s - groupid %ld does not match file gid %lu",
245 filename, ngid, (unsigned long)gid);
246
247 fclose(stream);
248
249 if (chdir(ATSPOOL_DIR) < 0)
250 perr("cannot chdir to %s", ATSPOOL_DIR);
251
252 /* Create a file to hold the output of the job we are about to run.
253 * Write the mail header.
254 */
255 if((fd_out=open(filename,
256 O_WRONLY | O_CREAT | O_EXCL, S_IWUSR | S_IRUSR)) < 0)
257 perr("cannot create output file");
258
259 write_string(fd_out, "Subject: Output from your job ");
260 write_string(fd_out, filename);
261 write_string(fd_out, "\n\n");
262 fstat(fd_out, &buf);
263 size = buf.st_size;
264
265 close(STDIN_FILENO);
266 close(STDOUT_FILENO);
267 close(STDERR_FILENO);
268
269 pid = fork();
270 if (pid < 0)
271 perr("error in fork");
272
273 else if (pid == 0)
274 {
275 char *nul = NULL;
276 char **nenvp = &nul;
277
278 /* Set up things for the child; we want standard input from the input file,
279 * and standard output and error sent to our output file.
280 */
281
282 if (lseek(fd_in, (off_t) 0, SEEK_SET) < 0)
283 perr("error in lseek");
284
285 if (dup(fd_in) != STDIN_FILENO)
286 perr("error in I/O redirection");
287
288 if (dup(fd_out) != STDOUT_FILENO)
289 perr("error in I/O redirection");
290
291 if (dup(fd_out) != STDERR_FILENO)
292 perr("error in I/O redirection");
293
294 close(fd_in);
295 close(fd_out);
296 if (chdir(ATJOB_DIR) < 0)
297 perr("cannot chdir to %s", ATJOB_DIR);
298
299 queue = *filename;
300
301 PRIV_START
302
303 nice(tolower(queue) - 'a');
304
305 #ifdef LOGIN_CAP
306 /*
307 * For simplicity and safety, set all aspects of the user context
308 * except for a selected subset: Don't set priority, which was
309 * set based on the queue file name according to the tradition.
310 * Don't bother to set environment, including path vars, either
311 * because it will be discarded anyway. Although the job file
312 * should set umask, preset it here just in case.
313 */
314 if (setusercontext(NULL, pentry, uid, LOGIN_SETALL &
315 ~(LOGIN_SETPRIORITY | LOGIN_SETPATH | LOGIN_SETENV)) != 0)
316 exit(EXIT_FAILURE); /* setusercontext() logged the error */
317 #else /* LOGIN_CAP */
318 if (initgroups(pentry->pw_name,pentry->pw_gid))
319 perr("cannot init group access list");
320
321 if (setgid(gid) < 0 || setegid(pentry->pw_gid) < 0)
322 perr("cannot change group");
323
324 if (setlogin(pentry->pw_name))
325 perr("cannot set login name");
326
327 if (setuid(uid) < 0 || seteuid(uid) < 0)
328 perr("cannot set user id");
329 #endif /* LOGIN_CAP */
330
331 if (chdir(pentry->pw_dir))
332 chdir("/");
333
334 if(execle("/bin/sh","sh",(char *) NULL, nenvp) != 0)
335 perr("exec failed for /bin/sh");
336
337 PRIV_END
338 }
339 /* We're the parent. Let's wait.
340 */
341 close(fd_in);
342 close(fd_out);
343 waitpid(pid, (int *) NULL, 0);
344
345 /* Send mail. Unlink the output file first, so it is deleted after
346 * the run.
347 */
348 stat(filename, &buf);
349 if (open(filename, O_RDONLY) != STDIN_FILENO)
350 perr("open of jobfile failed");
351
352 unlink(filename);
353 if ((buf.st_size != size) || send_mail)
354 {
355 PRIV_START
356
357 #ifdef LOGIN_CAP
358 /*
359 * This time set full context to run the mailer.
360 */
361 if (setusercontext(NULL, pentry, uid, LOGIN_SETALL) != 0)
362 exit(EXIT_FAILURE); /* setusercontext() logged the error */
363 #else /* LOGIN_CAP */
364 if (initgroups(pentry->pw_name,pentry->pw_gid))
365 perr("cannot init group access list");
366
367 if (setgid(gid) < 0 || setegid(pentry->pw_gid) < 0)
368 perr("cannot change group");
369
370 if (setlogin(pentry->pw_name))
371 perr("cannot set login name");
372
373 if (setuid(uid) < 0 || seteuid(uid) < 0)
374 perr("cannot set user id");
375 #endif /* LOGIN_CAP */
376
377 if (chdir(pentry->pw_dir))
378 chdir("/");
379
380 #ifdef __FreeBSD__
381 execl(_PATH_SENDMAIL, "sendmail", "-F", "Atrun Service",
382 "-odi", "-oem",
383 mailname, (char *) NULL);
384 #else
385 execl(MAIL_CMD, MAIL_CMD, mailname, (char *) NULL);
386 #endif
387 perr("exec failed for mail command");
388
389 PRIV_END
390 }
391 exit(EXIT_SUCCESS);
392 }
393
394 /* Global functions */
395
396 /* Needed in gloadavg.c */
397 void
perr(const char * fmt,...)398 perr(const char *fmt, ...)
399 {
400 const char * const fmtadd = ": %m";
401 char nfmt[strlen(fmt) + strlen(fmtadd) + 1];
402 va_list ap;
403
404 va_start(ap, fmt);
405 if (debug)
406 {
407 vwarn(fmt, ap);
408 }
409 else
410 {
411 snprintf(nfmt, sizeof(nfmt), "%s%s", fmt, fmtadd);
412 vsyslog(LOG_ERR, nfmt, ap);
413 }
414 va_end(ap);
415
416 exit(EXIT_FAILURE);
417 }
418
419 void
perrx(const char * fmt,...)420 perrx(const char *fmt, ...)
421 {
422 va_list ap;
423
424 va_start(ap, fmt);
425 if (debug)
426 vwarnx(fmt, ap);
427 else
428 vsyslog(LOG_ERR, fmt, ap);
429 va_end(ap);
430
431 exit(EXIT_FAILURE);
432 }
433
434 int
main(int argc,char * argv[])435 main(int argc, char *argv[])
436 {
437 /* Browse through ATJOB_DIR, checking all the jobfiles wether they should
438 * be executed and or deleted. The queue is coded into the first byte of
439 * the job filename, the date (in minutes since Eon) as a hex number in the
440 * following eight bytes, followed by a dot and a serial number. A file
441 * which has not been executed yet is denoted by its execute - bit set.
442 * For those files which are to be executed, run_file() is called, which forks
443 * off a child which takes care of I/O redirection, forks off another child
444 * for execution and yet another one, optionally, for sending mail.
445 * Files which already have run are removed during the next invocation.
446 */
447 DIR *spool;
448 struct dirent *dirent;
449 struct stat buf;
450 unsigned long ctm;
451 unsigned long jobno;
452 char queue;
453 time_t now, run_time;
454 char batch_name[] = "Z2345678901234";
455 uid_t batch_uid;
456 gid_t batch_gid;
457 int c;
458 int run_batch;
459 #ifdef __FreeBSD__
460 size_t ncpusz;
461 double load_avg = -1;
462 int ncpu;
463 #else
464 double load_avg = LOADAVG_MX;
465 #endif
466
467 /* We don't need root privileges all the time; running under uid and gid daemon
468 * is fine.
469 */
470
471 RELINQUISH_PRIVS_ROOT(DAEMON_UID, DAEMON_GID)
472
473 openlog(atrun, LOG_PID, LOG_CRON);
474
475 opterr = 0;
476 while((c=getopt(argc, argv, "dl:"))!= -1)
477 {
478 switch (c)
479 {
480 case 'l':
481 if (sscanf(optarg, "%lf", &load_avg) != 1)
482 perr("garbled option -l");
483 #ifndef __FreeBSD__
484 if (load_avg <= 0.)
485 load_avg = LOADAVG_MX;
486 #endif
487 break;
488
489 case 'd':
490 debug ++;
491 break;
492
493 case '?':
494 default:
495 usage();
496 }
497 }
498
499 if (chdir(ATJOB_DIR) != 0)
500 perr("cannot change to %s", ATJOB_DIR);
501
502 #ifdef __FreeBSD__
503 if (load_avg <= 0.) {
504 ncpusz = sizeof(size_t);
505 if (sysctlbyname("hw.ncpu", &ncpu, &ncpusz, NULL, 0) < 0)
506 ncpu = 1;
507 load_avg = LOADAVG_MX * ncpu;
508 }
509 #endif
510
511 /* Main loop. Open spool directory for reading and look over all the
512 * files in there. If the filename indicates that the job should be run
513 * and the x bit is set, fork off a child which sets its user and group
514 * id to that of the files and exec a /bin/sh which executes the shell
515 * script. Unlink older files if they should no longer be run. For
516 * deletion, their r bit has to be turned on.
517 *
518 * Also, pick the oldest batch job to run, at most one per invocation of
519 * atrun.
520 */
521 if ((spool = opendir(".")) == NULL)
522 perr("cannot read %s", ATJOB_DIR);
523
524 if (flock(dirfd(spool), LOCK_EX) == -1)
525 perr("cannot lock %s", ATJOB_DIR);
526
527 now = time(NULL);
528 run_batch = 0;
529 batch_uid = (uid_t) -1;
530 batch_gid = (gid_t) -1;
531
532 while ((dirent = readdir(spool)) != NULL) {
533 if (stat(dirent->d_name,&buf) != 0)
534 perr("cannot stat in %s", ATJOB_DIR);
535
536 /* We don't want directories
537 */
538 if (!S_ISREG(buf.st_mode))
539 continue;
540
541 if (sscanf(dirent->d_name,"%c%5lx%8lx",&queue,&jobno,&ctm) != 3)
542 continue;
543
544 run_time = (time_t) ctm*60;
545
546 if ((S_IXUSR & buf.st_mode) && (run_time <=now)) {
547 if (isupper(queue) && (strcmp(batch_name,dirent->d_name) > 0)) {
548 run_batch = 1;
549 strlcpy(batch_name, dirent->d_name, sizeof(batch_name));
550 batch_uid = buf.st_uid;
551 batch_gid = buf.st_gid;
552 }
553
554 /* The file is executable and old enough
555 */
556 if (islower(queue))
557 run_file(dirent->d_name, buf.st_uid, buf.st_gid);
558 }
559 /* Delete older files
560 */
561 if ((run_time < now) && !(S_IXUSR & buf.st_mode) && (S_IRUSR & buf.st_mode))
562 unlink(dirent->d_name);
563 }
564 /* run the single batch file, if any
565 */
566 if (run_batch && (gloadavg() < load_avg))
567 run_file(batch_name, batch_uid, batch_gid);
568
569 if (flock(dirfd(spool), LOCK_UN) == -1)
570 perr("cannot unlock %s", ATJOB_DIR);
571
572 if (closedir(spool) == -1)
573 perr("cannot closedir %s", ATJOB_DIR);
574
575 closelog();
576 exit(EXIT_SUCCESS);
577 }
578
579 static void
usage(void)580 usage(void)
581 {
582 if (debug)
583 fprintf(stderr, "usage: atrun [-l load_avg] [-d]\n");
584 else
585 syslog(LOG_ERR, "usage: atrun [-l load_avg] [-d]");
586
587 exit(EXIT_FAILURE);
588 }
589