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, ...) __dead2 __printflike(1, 2);
86 void perrx(const char *fmt, ...) __dead2 __printflike(1, 2);
87 static void usage(void) __dead2;
88
89 /* Local functions */
90 static int
write_string(int fd,const char * a)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
myfork(void)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
run_file(const char * filename,uid_t uid,gid_t gid)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
perr(const char * fmt,...)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
perrx(const char * fmt,...)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
main(int argc,char * argv[])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
usage(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 }
552