atrun.c revision 200982 
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
27static const char rcsid[] =
28  "$FreeBSD: head/libexec/atrun/atrun.c 200982 2009-12-25 10:30:54Z ed $";
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 <stdarg.h>
45#include <stddef.h>
46#include <stdio.h>
47#include <stdlib.h>
48#include <string.h>
49#include <syslog.h>
50#include <time.h>
51#include <unistd.h>
52#ifdef __FreeBSD__
53#include <paths.h>
54#else
55#include <getopt.h>
56#endif
57#ifdef LOGIN_CAP
58#include <login_cap.h>
59#endif
60#ifdef PAM
61#include <security/pam_appl.h>
62#include <security/openpam.h>
63#endif
64
65/* Local headers */
66
67#include "gloadavg.h"
68#define MAIN
69#include "privs.h"
70
71/* Macros */
72
73#ifndef ATJOB_DIR
74#define ATJOB_DIR "/usr/spool/atjobs/"
75#endif
76
77#ifndef ATSPOOL_DIR
78#define ATSPOOL_DIR "/usr/spool/atspool/"
79#endif
80
81#ifndef LOADAVG_MX
82#define LOADAVG_MX 1.5
83#endif
84
85/* File scope variables */
86
87static const char * const atrun = "atrun"; /* service name for syslog etc. */
88static int debug = 0;
89
90void perr(const char *fmt, ...);
91void perrx(const char *fmt, ...);
92static void usage(void);
93
94/* Local functions */
95static int
96write_string(int fd, const char* a)
97{
98    return write(fd, a, strlen(a));
99}
100
101#undef DEBUG_FORK
102#ifdef DEBUG_FORK
103static pid_t
104myfork(void)
105{
106	pid_t res;
107	res = fork();
108	if (res == 0)
109	    kill(getpid(),SIGSTOP);
110	return res;
111}
112
113#define fork myfork
114#endif
115
116static void
117run_file(const char *filename, uid_t uid, gid_t gid)
118{
119/* Run a file by spawning off a process which redirects I/O,
120 * spawns a subshell, then waits for it to complete and sends
121 * mail to the user.
122 */
123    pid_t pid;
124    int fd_out, fd_in;
125    int queue;
126    char mailbuf[MAXLOGNAME], fmt[49];
127    char *mailname = NULL;
128    FILE *stream;
129    int send_mail = 0;
130    struct stat buf, lbuf;
131    off_t size;
132    struct passwd *pentry;
133    int fflags;
134    long nuid;
135    long ngid;
136#ifdef PAM
137    pam_handle_t *pamh = NULL;
138    int pam_err;
139    struct pam_conv pamc = {
140	.conv = openpam_nullconv,
141	.appdata_ptr = NULL
142    };
143#endif
144
145    PRIV_START
146
147    if (chmod(filename, S_IRUSR) != 0)
148    {
149	perr("cannot change file permissions");
150    }
151
152    PRIV_END
153
154    pid = fork();
155    if (pid == -1)
156	perr("cannot fork");
157
158    else if (pid != 0)
159	return;
160
161    /* Let's see who we mail to.  Hopefully, we can read it from
162     * the command file; if not, send it to the owner, or, failing that,
163     * to root.
164     */
165
166    pentry = getpwuid(uid);
167    if (pentry == NULL)
168	perrx("Userid %lu not found - aborting job %s",
169		(unsigned long) uid, filename);
170
171#ifdef PAM
172    PRIV_START
173
174    pam_err = pam_start(atrun, pentry->pw_name, &pamc, &pamh);
175    if (pam_err != PAM_SUCCESS)
176	perrx("cannot start PAM: %s", pam_strerror(pamh, pam_err));
177
178    pam_err = pam_acct_mgmt(pamh, PAM_SILENT);
179    /* Expired password shouldn't prevent the job from running. */
180    if (pam_err != PAM_SUCCESS && pam_err != PAM_NEW_AUTHTOK_REQD)
181	perrx("Account %s (userid %lu) unavailable for job %s: %s",
182	    pentry->pw_name, (unsigned long)uid,
183	    filename, pam_strerror(pamh, pam_err));
184
185    pam_end(pamh, pam_err);
186
187    PRIV_END
188#endif /* PAM */
189
190    PRIV_START
191
192    stream=fopen(filename, "r");
193
194    PRIV_END
195
196    if (stream == NULL)
197	perr("cannot open input file");
198
199    if ((fd_in = dup(fileno(stream))) <0)
200	perr("error duplicating input file descriptor");
201
202    if (fstat(fd_in, &buf) == -1)
203	perr("error in fstat of input file descriptor");
204
205    if (lstat(filename, &lbuf) == -1)
206	perr("error in fstat of input file");
207
208    if (S_ISLNK(lbuf.st_mode))
209	perrx("Symbolic link encountered in job %s - aborting", filename);
210
211    if ((lbuf.st_dev != buf.st_dev) || (lbuf.st_ino != buf.st_ino) ||
212        (lbuf.st_uid != buf.st_uid) || (lbuf.st_gid != buf.st_gid) ||
213        (lbuf.st_size!=buf.st_size))
214	perrx("Somebody changed files from under us for job %s - aborting",
215		filename);
216
217    if (buf.st_nlink > 1)
218	perrx("Somebody is trying to run a linked script for job %s", filename);
219
220    if ((fflags = fcntl(fd_in, F_GETFD)) <0)
221	perr("error in fcntl");
222
223    fcntl(fd_in, F_SETFD, fflags & ~FD_CLOEXEC);
224
225    snprintf(fmt, sizeof(fmt),
226	"#!/bin/sh\n# atrun uid=%%ld gid=%%ld\n# mail %%%ds %%d",
227                          MAXLOGNAME - 1);
228
229    if (fscanf(stream, fmt, &nuid, &ngid, mailbuf, &send_mail) != 4)
230	perrx("File %s is in wrong format - aborting", filename);
231
232    if (mailbuf[0] == '-')
233	perrx("Illegal mail name %s in %s", mailbuf, filename);
234
235    mailname = mailbuf;
236
237    if (nuid != uid)
238	perrx("Job %s - userid %ld does not match file uid %lu",
239		filename, nuid, (unsigned long)uid);
240
241    if (ngid != gid)
242	perrx("Job %s - groupid %ld does not match file gid %lu",
243		filename, ngid, (unsigned long)gid);
244
245    fclose(stream);
246
247    if (chdir(ATSPOOL_DIR) < 0)
248	perr("cannot chdir to %s", ATSPOOL_DIR);
249
250    /* Create a file to hold the output of the job we are about to run.
251     * Write the mail header.
252     */
253    if((fd_out=open(filename,
254		O_WRONLY | O_CREAT | O_EXCL, S_IWUSR | S_IRUSR)) < 0)
255	perr("cannot create output file");
256
257    write_string(fd_out, "Subject: Output from your job ");
258    write_string(fd_out, filename);
259    write_string(fd_out, "\n\n");
260    fstat(fd_out, &buf);
261    size = buf.st_size;
262
263    close(STDIN_FILENO);
264    close(STDOUT_FILENO);
265    close(STDERR_FILENO);
266
267    pid = fork();
268    if (pid < 0)
269	perr("error in fork");
270
271    else if (pid == 0)
272    {
273	char *nul = NULL;
274	char **nenvp = &nul;
275
276	/* Set up things for the child; we want standard input from the input file,
277	 * and standard output and error sent to our output file.
278	 */
279
280	if (lseek(fd_in, (off_t) 0, SEEK_SET) < 0)
281	    perr("error in lseek");
282
283	if (dup(fd_in) != STDIN_FILENO)
284	    perr("error in I/O redirection");
285
286	if (dup(fd_out) != STDOUT_FILENO)
287	    perr("error in I/O redirection");
288
289	if (dup(fd_out) != STDERR_FILENO)
290	    perr("error in I/O redirection");
291
292	close(fd_in);
293	close(fd_out);
294	if (chdir(ATJOB_DIR) < 0)
295	    perr("cannot chdir to %s", ATJOB_DIR);
296
297	queue = *filename;
298
299	PRIV_START
300
301        nice(tolower(queue) - 'a');
302
303#ifdef LOGIN_CAP
304	/*
305	 * For simplicity and safety, set all aspects of the user context
306	 * except for a selected subset:  Don't set priority, which was
307	 * set based on the queue file name according to the tradition.
308	 * Don't bother to set environment, including path vars, either
309	 * because it will be discarded anyway.  Although the job file
310	 * should set umask, preset it here just in case.
311	 */
312	if (setusercontext(NULL, pentry, uid, LOGIN_SETALL &
313		~(LOGIN_SETPRIORITY | LOGIN_SETPATH | LOGIN_SETENV)) != 0)
314	    exit(EXIT_FAILURE);	/* setusercontext() logged the error */
315#else /* LOGIN_CAP */
316	if (initgroups(pentry->pw_name,pentry->pw_gid))
317	    perr("cannot init group access list");
318
319	if (setgid(gid) < 0 || setegid(pentry->pw_gid) < 0)
320	    perr("cannot change group");
321
322	if (setlogin(pentry->pw_name))
323	    perr("cannot set login name");
324
325	if (setuid(uid) < 0 || seteuid(uid) < 0)
326	    perr("cannot set user id");
327#endif /* LOGIN_CAP */
328
329	if (chdir(pentry->pw_dir))
330		chdir("/");
331
332	if(execle("/bin/sh","sh",(char *) NULL, nenvp) != 0)
333	    perr("exec failed for /bin/sh");
334
335	PRIV_END
336    }
337    /* We're the parent.  Let's wait.
338     */
339    close(fd_in);
340    close(fd_out);
341    waitpid(pid, (int *) NULL, 0);
342
343    /* Send mail.  Unlink the output file first, so it is deleted after
344     * the run.
345     */
346    stat(filename, &buf);
347    if (open(filename, O_RDONLY) != STDIN_FILENO)
348        perr("open of jobfile failed");
349
350    unlink(filename);
351    if ((buf.st_size != size) || send_mail)
352    {
353	PRIV_START
354
355#ifdef LOGIN_CAP
356	/*
357	 * This time set full context to run the mailer.
358	 */
359	if (setusercontext(NULL, pentry, uid, LOGIN_SETALL) != 0)
360	    exit(EXIT_FAILURE);	/* setusercontext() logged the error */
361#else /* LOGIN_CAP */
362	if (initgroups(pentry->pw_name,pentry->pw_gid))
363	    perr("cannot init group access list");
364
365	if (setgid(gid) < 0 || setegid(pentry->pw_gid) < 0)
366	    perr("cannot change group");
367
368	if (setlogin(pentry->pw_name))
369	    perr("cannot set login name");
370
371	if (setuid(uid) < 0 || seteuid(uid) < 0)
372	    perr("cannot set user id");
373#endif /* LOGIN_CAP */
374
375	if (chdir(pentry->pw_dir))
376		chdir("/");
377
378#ifdef __FreeBSD__
379	execl(_PATH_SENDMAIL, "sendmail", "-F", "Atrun Service",
380			"-odi", "-oem",
381			mailname, (char *) NULL);
382#else
383        execl(MAIL_CMD, MAIL_CMD, mailname, (char *) NULL);
384#endif
385	    perr("exec failed for mail command");
386
387	PRIV_END
388    }
389    exit(EXIT_SUCCESS);
390}
391
392/* Global functions */
393
394/* Needed in gloadavg.c */
395void
396perr(const char *fmt, ...)
397{
398    const char * const fmtadd = ": %m";
399    char nfmt[strlen(fmt) + strlen(fmtadd) + 1];
400    va_list ap;
401
402    va_start(ap, fmt);
403    if (debug)
404    {
405	vwarn(fmt, ap);
406    }
407    else
408    {
409	snprintf(nfmt, sizeof(nfmt), "%s%s", fmt, fmtadd);
410	vsyslog(LOG_ERR, nfmt, ap);
411    }
412    va_end(ap);
413
414    exit(EXIT_FAILURE);
415}
416
417void
418perrx(const char *fmt, ...)
419{
420    va_list ap;
421
422    va_start(ap, fmt);
423    if (debug)
424	vwarnx(fmt, ap);
425    else
426	vsyslog(LOG_ERR, fmt, ap);
427    va_end(ap);
428
429    exit(EXIT_FAILURE);
430}
431
432int
433main(int argc, char *argv[])
434{
435/* Browse through  ATJOB_DIR, checking all the jobfiles wether they should
436 * be executed and or deleted. The queue is coded into the first byte of
437 * the job filename, the date (in minutes since Eon) as a hex number in the
438 * following eight bytes, followed by a dot and a serial number.  A file
439 * which has not been executed yet is denoted by its execute - bit set.
440 * For those files which are to be executed, run_file() is called, which forks
441 * off a child which takes care of I/O redirection, forks off another child
442 * for execution and yet another one, optionally, for sending mail.
443 * Files which already have run are removed during the next invocation.
444 */
445    DIR *spool;
446    struct dirent *dirent;
447    struct stat buf;
448    unsigned long ctm;
449    unsigned long jobno;
450    char queue;
451    time_t now, run_time;
452    char batch_name[] = "Z2345678901234";
453    uid_t batch_uid;
454    gid_t batch_gid;
455    int c;
456    int run_batch;
457    double load_avg = LOADAVG_MX;
458
459/* We don't need root privileges all the time; running under uid and gid daemon
460 * is fine.
461 */
462
463    RELINQUISH_PRIVS_ROOT(DAEMON_UID, DAEMON_GID)
464
465    openlog(atrun, LOG_PID, LOG_CRON);
466
467    opterr = 0;
468    while((c=getopt(argc, argv, "dl:"))!= -1)
469    {
470	switch (c)
471	{
472	case 'l':
473	    if (sscanf(optarg, "%lf", &load_avg) != 1)
474		perr("garbled option -l");
475	    if (load_avg <= 0.)
476		load_avg = LOADAVG_MX;
477	    break;
478
479	case 'd':
480	    debug ++;
481	    break;
482
483	case '?':
484	default:
485	    usage();
486	}
487    }
488
489    if (chdir(ATJOB_DIR) != 0)
490	perr("cannot change to %s", ATJOB_DIR);
491
492    /* Main loop. Open spool directory for reading and look over all the
493     * files in there. If the filename indicates that the job should be run
494     * and the x bit is set, fork off a child which sets its user and group
495     * id to that of the files and exec a /bin/sh which executes the shell
496     * script. Unlink older files if they should no longer be run.  For
497     * deletion, their r bit has to be turned on.
498     *
499     * Also, pick the oldest batch job to run, at most one per invocation of
500     * atrun.
501     */
502    if ((spool = opendir(".")) == NULL)
503	perr("cannot read %s", ATJOB_DIR);
504
505    now = time(NULL);
506    run_batch = 0;
507    batch_uid = (uid_t) -1;
508    batch_gid = (gid_t) -1;
509
510    while ((dirent = readdir(spool)) != NULL) {
511	if (stat(dirent->d_name,&buf) != 0)
512	    perr("cannot stat in %s", ATJOB_DIR);
513
514	/* We don't want directories
515	 */
516	if (!S_ISREG(buf.st_mode))
517	    continue;
518
519	if (sscanf(dirent->d_name,"%c%5lx%8lx",&queue,&jobno,&ctm) != 3)
520	    continue;
521
522	run_time = (time_t) ctm*60;
523
524	if ((S_IXUSR & buf.st_mode) && (run_time <=now)) {
525	    if (isupper(queue) && (strcmp(batch_name,dirent->d_name) > 0)) {
526		run_batch = 1;
527		strlcpy(batch_name, dirent->d_name, sizeof(batch_name));
528		batch_uid = buf.st_uid;
529		batch_gid = buf.st_gid;
530	    }
531
532	/* The file is executable and old enough
533	 */
534	    if (islower(queue))
535		run_file(dirent->d_name, buf.st_uid, buf.st_gid);
536	}
537	/*  Delete older files
538	 */
539	if ((run_time < now) && !(S_IXUSR & buf.st_mode) && (S_IRUSR & buf.st_mode))
540	    unlink(dirent->d_name);
541    }
542    /* run the single batch file, if any
543    */
544    if (run_batch && (gloadavg() < load_avg))
545	run_file(batch_name, batch_uid, batch_gid);
546
547    closelog();
548    exit(EXIT_SUCCESS);
549}
550
551static void
552usage(void)
553{
554    if (debug)
555	fprintf(stderr, "usage: atrun [-l load_avg] [-d]\n");
556    else
557	syslog(LOG_ERR, "usage: atrun [-l load_avg] [-d]");
558
559    exit(EXIT_FAILURE);
560}
561