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#include <sys/cdefs.h>
27#ifndef lint
28__FBSDID("$FreeBSD: src/libexec/atrun/atrun.c,v 1.27 2009/12/25 10:30:54 ed 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 <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#if 1
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#define MAIN
68#include "privs.h"
69#include "pathnames.h"
70
71/* Macros */
72
73#ifndef ATJOB_DIR
74#define ATJOB_DIR _PATH_ATJOBS
75#endif
76
77#ifndef ATSPOOL_DIR
78#define ATSPOOL_DIR _PATH_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 ssize_t
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[64];
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#ifdef __APPLE__
162    {
163	pid_t pg = setsid();
164	if (pg == -1) syslog(LOG_ERR,"setsid() failed: %m");
165    }
166#endif
167
168    /* Let's see who we mail to.  Hopefully, we can read it from
169     * the command file; if not, send it to the owner, or, failing that,
170     * to root.
171     */
172
173    pentry = getpwuid(uid);
174    if (pentry == NULL)
175	perrx("Userid %lu not found - aborting job %s",
176		(unsigned long) uid, filename);
177
178#ifdef PAM
179    PRIV_START
180
181    pam_err = pam_start(atrun, pentry->pw_name, &pamc, &pamh);
182    if (pam_err != PAM_SUCCESS)
183	perrx("cannot start PAM: %s", pam_strerror(pamh, pam_err));
184
185    pam_err = pam_acct_mgmt(pamh, PAM_SILENT);
186    /* Expired password shouldn't prevent the job from running. */
187    if (pam_err != PAM_SUCCESS && pam_err != PAM_NEW_AUTHTOK_REQD)
188	perrx("Account %s (userid %lu) unavailable for job %s: %s",
189	    pentry->pw_name, (unsigned long)uid,
190	    filename, pam_strerror(pamh, pam_err));
191
192    pam_end(pamh, pam_err);
193
194    PRIV_END
195#endif /* PAM */
196
197    PRIV_START
198
199    stream=fopen(filename, "r");
200
201    PRIV_END
202
203    if (stream == NULL)
204	perr("cannot open input file");
205
206    if ((fd_in = dup(fileno(stream))) <0)
207	perr("error duplicating input file descriptor");
208
209    if (fstat(fd_in, &buf) == -1)
210	perr("error in fstat of input file descriptor");
211
212    if (lstat(filename, &lbuf) == -1)
213	perr("error in fstat of input file");
214
215    if (S_ISLNK(lbuf.st_mode))
216	perrx("Symbolic link encountered in job %s - aborting", filename);
217
218    if ((lbuf.st_dev != buf.st_dev) || (lbuf.st_ino != buf.st_ino) ||
219        (lbuf.st_uid != buf.st_uid) || (lbuf.st_gid != buf.st_gid) ||
220        (lbuf.st_size!=buf.st_size))
221	perrx("Somebody changed files from under us for job %s - aborting",
222		filename);
223
224    if (buf.st_nlink > 1)
225	perrx("Somebody is trying to run a linked script for job %s", filename);
226
227    if ((fflags = fcntl(fd_in, F_GETFD)) <0)
228	perr("error in fcntl");
229
230    fcntl(fd_in, F_SETFD, fflags & ~FD_CLOEXEC);
231
232    snprintf(fmt, sizeof(fmt),
233	"#!/bin/sh\n# atrun uid=%%ld gid=%%ld\n# mail %%%ds %%d",
234                          MAXLOGNAME - 1);
235
236    if (fscanf(stream, fmt, &nuid, &ngid, mailbuf, &send_mail) != 4)
237	perrx("File %s is in wrong format - aborting", filename);
238
239    if (mailbuf[0] == '-')
240	perrx("Illegal mail name %s in %s", mailbuf, filename);
241
242    mailname = mailbuf;
243
244    if (nuid != uid)
245	perrx("Job %s - userid %ld does not match file uid %lu",
246		filename, nuid, (unsigned long)uid);
247
248    if (ngid != gid)
249	perrx("Job %s - groupid %ld does not match file gid %lu",
250		filename, ngid, (unsigned long)gid);
251
252    fclose(stream);
253
254    if (chdir(ATSPOOL_DIR) < 0)
255	perr("cannot chdir to %s", ATSPOOL_DIR);
256
257    /* Create a file to hold the output of the job we are about to run.
258     * Write the mail header.
259     */
260    if((fd_out=open(filename,
261		O_WRONLY | O_CREAT | O_EXCL, S_IWUSR | S_IRUSR)) < 0)
262	perr("cannot create output file");
263
264    write_string(fd_out, "Subject: Output from your job ");
265    write_string(fd_out, filename);
266    write_string(fd_out, "\n\n");
267    fstat(fd_out, &buf);
268    size = buf.st_size;
269
270    close(STDIN_FILENO);
271    close(STDOUT_FILENO);
272    close(STDERR_FILENO);
273
274    pid = fork();
275    if (pid < 0)
276	perr("error in fork");
277
278    else if (pid == 0)
279    {
280	char *nul = NULL;
281	char **nenvp = &nul;
282
283	/* Set up things for the child; we want standard input from the input file,
284	 * and standard output and error sent to our output file.
285	 */
286
287	if (lseek(fd_in, (off_t) 0, SEEK_SET) < 0)
288	    perr("error in lseek");
289
290	if (dup(fd_in) != STDIN_FILENO)
291	    perr("error in I/O redirection");
292
293	if (dup(fd_out) != STDOUT_FILENO)
294	    perr("error in I/O redirection");
295
296	if (dup(fd_out) != STDERR_FILENO)
297	    perr("error in I/O redirection");
298
299	close(fd_in);
300	close(fd_out);
301	if (chdir(ATJOB_DIR) < 0)
302	    perr("cannot chdir to %s", ATJOB_DIR);
303
304	queue = *filename;
305
306	PRIV_START
307
308        nice(tolower(queue) - 'a');
309
310#ifdef LOGIN_CAP
311	/*
312	 * For simplicity and safety, set all aspects of the user context
313	 * except for a selected subset:  Don't set priority, which was
314	 * set based on the queue file name according to the tradition.
315	 * Don't bother to set environment, including path vars, either
316	 * because it will be discarded anyway.  Although the job file
317	 * should set umask, preset it here just in case.
318	 */
319	if (setusercontext(NULL, pentry, uid, LOGIN_SETALL &
320		~(LOGIN_SETPRIORITY | LOGIN_SETPATH | LOGIN_SETENV)) != 0)
321	    exit(EXIT_FAILURE);	/* setusercontext() logged the error */
322#else /* LOGIN_CAP */
323	if (setgid(gid) < 0 || setegid(pentry->pw_gid) < 0)
324	    perr("cannot change group");
325
326	if (initgroups(pentry->pw_name,pentry->pw_gid))
327	    perr("cannot init group access list");
328
329	if (setlogin(pentry->pw_name))
330	    perr("cannot set login name");
331
332	if (setuid(uid) < 0 || seteuid(uid) < 0)
333	    perr("cannot set user id");
334#endif /* LOGIN_CAP */
335
336	if (chdir(pentry->pw_dir))
337		chdir("/");
338
339	if(execle("/bin/sh","sh",(char *) NULL, nenvp) != 0)
340	    perr("exec failed for /bin/sh");
341
342	PRIV_END
343    }
344    /* We're the parent.  Let's wait.
345     */
346    close(fd_in);
347    close(fd_out);
348    waitpid(pid, (int *) NULL, 0);
349
350    /* Send mail.  Unlink the output file first, so it is deleted after
351     * the run.
352     */
353    stat(filename, &buf);
354    if (open(filename, O_RDONLY) != STDIN_FILENO)
355        perr("open of jobfile failed");
356
357    unlink(filename);
358    if ((buf.st_size != size) || send_mail)
359    {
360	PRIV_START
361
362#ifdef LOGIN_CAP
363	/*
364	 * This time set full context to run the mailer.
365	 */
366	if (setusercontext(NULL, pentry, uid, LOGIN_SETALL) != 0)
367	    exit(EXIT_FAILURE);	/* setusercontext() logged the error */
368#else /* LOGIN_CAP */
369	if (setgid(gid) < 0 || setegid(pentry->pw_gid) < 0)
370	    perr("cannot change group");
371
372	if (initgroups(pentry->pw_name,pentry->pw_gid))
373	    perr("cannot init group access list");
374
375	if (setlogin(pentry->pw_name))
376	    perr("cannot set login name");
377
378	if (setuid(uid) < 0 || seteuid(uid) < 0)
379	    perr("cannot set user id");
380#endif /* LOGIN_CAP */
381
382	if (chdir(pentry->pw_dir))
383		chdir("/");
384
385#if 1
386	execl(_PATH_SENDMAIL, "sendmail", "-F", "Atrun Service",
387			"-odi", "-oem",
388			mailname, (char *) NULL);
389#else
390        execl(MAIL_CMD, MAIL_CMD, mailname, (char *) NULL);
391#endif
392	    perr("exec failed for mail command");
393
394	PRIV_END
395    }
396    exit(EXIT_SUCCESS);
397}
398
399/* Global functions */
400
401/* Needed in gloadavg.c */
402void
403perr(const char *fmt, ...)
404{
405    const char * const fmtadd = ": %m";
406    char nfmt[strlen(fmt) + strlen(fmtadd) + 1];
407    va_list ap;
408
409    va_start(ap, fmt);
410    if (debug)
411    {
412	vwarn(fmt, ap);
413    }
414    else
415    {
416	snprintf(nfmt, sizeof(nfmt), "%s%s", fmt, fmtadd);
417	vsyslog(LOG_ERR, nfmt, ap);
418    }
419    va_end(ap);
420
421    exit(EXIT_FAILURE);
422}
423
424void
425perrx(const char *fmt, ...)
426{
427    va_list ap;
428
429    va_start(ap, fmt);
430    if (debug)
431	vwarnx(fmt, ap);
432    else
433	vsyslog(LOG_ERR, fmt, ap);
434    va_end(ap);
435
436    exit(EXIT_FAILURE);
437}
438
439int
440main(int argc, char *argv[])
441{
442/* Browse through  ATJOB_DIR, checking all the jobfiles wether they should
443 * be executed and or deleted. The queue is coded into the first byte of
444 * the job filename, the date (in minutes since Eon) as a hex number in the
445 * following eight bytes, followed by a dot and a serial number.  A file
446 * which has not been executed yet is denoted by its execute - bit set.
447 * For those files which are to be executed, run_file() is called, which forks
448 * off a child which takes care of I/O redirection, forks off another child
449 * for execution and yet another one, optionally, for sending mail.
450 * Files which already have run are removed during the next invocation.
451 */
452    DIR *spool;
453    struct dirent *dirent;
454    struct stat buf;
455    unsigned long ctm;
456    unsigned long jobno;
457    char queue;
458    time_t now, run_time;
459    char batch_name[] = "Z2345678901234";
460    uid_t batch_uid;
461    gid_t batch_gid;
462    int c;
463    int run_batch;
464    double load_avg = LOADAVG_MX, la;
465
466/* We don't need root privileges all the time; running under uid and gid daemon
467 * is fine.
468 */
469
470    RELINQUISH_PRIVS_ROOT(DAEMON_UID, DAEMON_GID)
471
472    openlog(atrun, LOG_PID, LOG_CRON);
473
474    opterr = 0;
475    while((c=getopt(argc, argv, "dl:"))!= -1)
476    {
477	switch (c)
478	{
479	case 'l':
480	    if (sscanf(optarg, "%lf", &load_avg) != 1)
481		perr("garbled option -l");
482	    if (load_avg <= 0.)
483		load_avg = LOADAVG_MX;
484	    break;
485
486	case 'd':
487	    debug ++;
488	    break;
489
490	case '?':
491	default:
492	    usage();
493	}
494    }
495
496    if (chdir(ATJOB_DIR) != 0)
497	perr("cannot change to %s", ATJOB_DIR);
498
499    /* Main loop. Open spool directory for reading and look over all the
500     * files in there. If the filename indicates that the job should be run
501     * and the x bit is set, fork off a child which sets its user and group
502     * id to that of the files and exec a /bin/sh which executes the shell
503     * script. Unlink older files if they should no longer be run.  For
504     * deletion, their r bit has to be turned on.
505     *
506     * Also, pick the oldest batch job to run, at most one per invocation of
507     * atrun.
508     */
509    if ((spool = opendir(".")) == NULL)
510	perr("cannot read %s", ATJOB_DIR);
511
512    now = time(NULL);
513    run_batch = 0;
514    batch_uid = (uid_t) -1;
515    batch_gid = (gid_t) -1;
516
517    while ((dirent = readdir(spool)) != NULL) {
518	if (stat(dirent->d_name,&buf) != 0)
519	    perr("cannot stat in %s", ATJOB_DIR);
520
521	/* We don't want directories
522	 */
523	if (!S_ISREG(buf.st_mode))
524	    continue;
525
526	if (sscanf(dirent->d_name,"%c%5lx%8lx",&queue,&jobno,&ctm) != 3)
527	    continue;
528
529	run_time = (time_t) ctm*60;
530
531	if ((S_IXUSR & buf.st_mode) && (run_time <=now)) {
532	    if ((isupper(queue) || queue == 'b') && (strcmp(batch_name,dirent->d_name) > 0)) {
533		run_batch = 1;
534		strlcpy(batch_name, dirent->d_name, sizeof(batch_name));
535		batch_uid = buf.st_uid;
536		batch_gid = buf.st_gid;
537	    }
538
539	/* The file is executable and old enough
540	 */
541	    if (islower(queue))
542		run_file(dirent->d_name, buf.st_uid, buf.st_gid);
543	}
544	/*  Delete older files
545	 */
546	if ((run_time < now) && !(S_IXUSR & buf.st_mode) && (S_IRUSR & buf.st_mode))
547	    unlink(dirent->d_name);
548    }
549    /* run the single batch file, if any
550    */
551    if (run_batch && (getloadavg(&la, 1) == 1) && la < load_avg)
552	run_file(batch_name, batch_uid, batch_gid);
553
554    closelog();
555#if __APPLE__
556    // allow enough time for child processes to call setsid(2)
557    sleep(1);
558#endif
559    exit(EXIT_SUCCESS);
560}
561
562static void
563usage(void)
564{
565    if (debug)
566	fprintf(stderr, "usage: atrun [-l load_avg] [-d]\n");
567    else
568	syslog(LOG_ERR, "usage: atrun [-l load_avg] [-d]");
569
570    exit(EXIT_FAILURE);
571}
572