atrun.c revision 10154 
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/* System Headers */
27
28#include <sys/fcntl.h>
29#include <sys/types.h>
30#include <sys/stat.h>
31#include <sys/wait.h>
32#include <ctype.h>
33#include <dirent.h>
34#include <errno.h>
35#include <pwd.h>
36#include <grp.h>
37#include <signal.h>
38#include <stddef.h>
39#include <stdio.h>
40#include <stdlib.h>
41#include <string.h>
42#include <time.h>
43#include <unistd.h>
44#include <syslog.h>
45#ifdef __FreeBSD__
46#include <paths.h>
47#else
48#include <getopt.h>
49#endif
50
51/* Local headers */
52
53#include "gloadavg.h"
54#define MAIN
55#include "privs.h"
56
57/* Macros */
58
59#ifndef ATJOB_DIR
60#define ATJOB_DIR "/usr/spool/atjobs/"
61#endif
62
63#ifndef ATSPOOL_DIR
64#define ATSPOOL_DIR "/usr/spool/atspool/"
65#endif
66
67#ifndef LOADAVG_MX
68#define LOADAVG_MX 1.5
69#endif
70
71/* File scope variables */
72
73static char *namep;
74static char rcsid[] = "$Id: atrun.c,v 1.5 1995/08/10 04:06:53 ache Exp $";
75static debug = 0;
76
77void perr(const char *a);
78
79/* Local functions */
80static int
81write_string(int fd, const char* a)
82{
83    return write(fd, a, strlen(a));
84}
85
86#undef DEBUG_FORK
87#ifdef DEBUG_FORK
88static pid_t
89myfork()
90{
91	pid_t res;
92	res = fork();
93	if (res == 0)
94	    kill(getpid(),SIGSTOP);
95	return res;
96}
97
98#define fork myfork
99#endif
100
101static void
102run_file(const char *filename, uid_t uid, gid_t gid)
103{
104/* Run a file by by spawning off a process which redirects I/O,
105 * spawns a subshell, then waits for it to complete and sends
106 * mail to the user.
107 */
108    pid_t pid;
109    int fd_out, fd_in;
110    int queue;
111    char mailbuf[9];
112    char *mailname = NULL;
113    FILE *stream;
114    int send_mail = 0;
115    struct stat buf, lbuf;
116    off_t size;
117    struct passwd *pentry;
118    int fflags;
119    long nuid;
120    long ngid;
121
122
123    PRIV_START
124
125    if (chmod(filename, S_IRUSR) != 0)
126    {
127	perr("Cannot change file permissions");
128    }
129
130    PRIV_END
131
132    pid = fork();
133    if (pid == -1)
134	perr("Cannot fork");
135
136    else if (pid != 0)
137	return;
138
139    /* Let's see who we mail to.  Hopefully, we can read it from
140     * the command file; if not, send it to the owner, or, failing that,
141     * to root.
142     */
143
144    pentry = getpwuid(uid);
145    if (pentry == NULL)
146    {
147	syslog(LOG_ERR,"Userid %lu not found - aborting job %s",
148	       (unsigned long) uid, filename);
149        exit(EXIT_FAILURE);
150    }
151    PRIV_START
152
153    stream=fopen(filename, "r");
154
155    PRIV_END
156
157    if (stream == NULL)
158	perr("Cannot open input file");
159
160    if ((fd_in = dup(fileno(stream))) <0)
161	perr("Error duplicating input file descriptor");
162
163    if (fstat(fd_in, &buf) == -1)
164	perr("Error in fstat of input file descriptor");
165
166    if (lstat(filename, &lbuf) == -1)
167	perr("Error in fstat of input file");
168
169    if (S_ISLNK(lbuf.st_mode)) {
170	syslog(LOG_ERR,"Symbolic link encountered in job %s - aborting",
171		filename);
172	exit(EXIT_FAILURE);
173    }
174    if ((lbuf.st_dev != buf.st_dev) || (lbuf.st_ino != buf.st_ino) ||
175        (lbuf.st_uid != buf.st_uid) || (lbuf.st_gid != buf.st_gid) ||
176        (lbuf.st_size!=buf.st_size)) {
177	syslog(LOG_ERR,"Somebody changed files from under us for job %s - "
178	"aborting",filename);
179	exit(EXIT_FAILURE);
180    }
181    if (buf.st_nlink > 1) {
182	syslog(LOG_ERR,"Someboy is trying to run a linked script for job %s",
183		filename);
184	exit(EXIT_FAILURE);
185    }
186    if ((fflags = fcntl(fd_in, F_GETFD)) <0)
187	perr("Error in fcntl");
188
189    fcntl(fd_in, F_SETFD, fflags & ~FD_CLOEXEC);
190
191    if (fscanf(stream, "#!/bin/sh\n# atrun uid=%ld gid=%ld\n# mail %8s %d",
192         &nuid, &ngid, mailbuf, &send_mail) != 4)
193    {
194	syslog(LOG_ERR,"File %s is in wrong format - aborting",
195		filename);
196	exit(EXIT_FAILURE);
197    }
198    if (mailbuf[0] == '-') {
199	syslog(LOG_ERR,"illegal mail name %s in %s",mailbuf,filename);
200	exit(EXIT_FAILURE);
201    }
202    mailname = mailbuf;
203    if (nuid != uid) {
204	syslog(LOG_ERR,"Job %s - userid %d does not match file uid %d",
205		filename, nuid, uid);
206	exit(EXIT_FAILURE);
207    }
208    if (ngid != gid) {
209	syslog(LOG_ERR,"Job %s - groupid %d does not match file gid %d",
210		filename, ngid, gid);
211	exit(EXIT_FAILURE);
212    }
213    fclose(stream);
214    if (chdir(ATSPOOL_DIR) < 0)
215	perr("Cannot chdir to " ATSPOOL_DIR);
216
217    /* Create a file to hold the output of the job we are about to run.
218     * Write the mail header.
219     */
220    if((fd_out=open(filename,
221		O_WRONLY | O_CREAT | O_EXCL, S_IWUSR | S_IRUSR)) < 0)
222	perr("Cannot create output file");
223
224    write_string(fd_out, "Subject: Output from your job ");
225    write_string(fd_out, filename);
226    write_string(fd_out, "\n\n");
227    fstat(fd_out, &buf);
228    size = buf.st_size;
229
230    close(STDIN_FILENO);
231    close(STDOUT_FILENO);
232    close(STDERR_FILENO);
233
234    pid = fork();
235    if (pid < 0)
236	perr("Error in fork");
237
238    else if (pid == 0)
239    {
240	char *nul = NULL;
241	char **nenvp = &nul;
242
243	/* Set up things for the child; we want standard input from the input file,
244	 * and standard output and error sent to our output file.
245	 */
246
247	if (lseek(fd_in, (off_t) 0, SEEK_SET) < 0)
248	    perr("Error in lseek");
249
250	if (dup(fd_in) != STDIN_FILENO)
251	    perr("Error in I/O redirection");
252
253	if (dup(fd_out) != STDOUT_FILENO)
254	    perr("Error in I/O redirection");
255
256	if (dup(fd_out) != STDERR_FILENO)
257	    perr("Error in I/O redirection");
258
259	close(fd_in);
260	close(fd_out);
261	if (chdir(ATJOB_DIR) < 0)
262	    perr("Cannot chdir to " ATJOB_DIR);
263
264	queue = *filename;
265
266	PRIV_START
267
268        nice(tolower(queue) - 'a');
269
270	if (chdir(pentry->pw_dir))
271		chdir("/");
272
273	if (initgroups(pentry->pw_name,pentry->pw_gid))
274	    perr("Cannot delete saved userids");
275
276	if (setgid(gid) < 0)
277	    perr("Cannot change group");
278
279	if (setuid(uid) < 0)
280	    perr("Cannot set user id");
281
282	if(execle("/bin/sh","sh",(char *) NULL, nenvp) != 0)
283	    perr("Exec failed for /bin/sh");
284
285	PRIV_END
286    }
287    /* We're the parent.  Let's wait.
288     */
289    close(fd_in);
290    close(fd_out);
291    waitpid(pid, (int *) NULL, 0);
292
293    /* Send mail.  Unlink the output file first, so it is deleted after
294     * the run.
295     */
296    stat(filename, &buf);
297    if (open(filename, O_RDONLY) != STDIN_FILENO)
298        perr("Open of jobfile failed");
299
300    unlink(filename);
301    if ((buf.st_size != size) || send_mail)
302    {
303	PRIV_START
304
305	if (chdir(pentry->pw_dir))
306		chdir("/");
307
308	if (initgroups(pentry->pw_name,pentry->pw_gid))
309	    perr("Cannot delete saved userids");
310
311	if (setgid(gid) < 0)
312	    perr("Cannot change group");
313
314	if (setuid(uid) < 0)
315	    perr("Cannot set user id");
316
317#ifdef __FreeBSD__
318	execl(_PATH_SENDMAIL, "sendmail", "-F", "Atrun Service",
319			"-odi", "-oem",
320			mailname, (char *) NULL);
321#else
322        execl(MAIL_CMD, MAIL_CMD, mailname, (char *) NULL);
323#endif
324	    perr("Exec failed for mail command");
325
326	PRIV_END
327    }
328    exit(EXIT_SUCCESS);
329}
330
331/* Global functions */
332
333/* Needed in gloadavg.c */
334void
335perr(const char *a)
336{
337    if (debug)
338    {
339	perror(a);
340    }
341    else
342	syslog(LOG_ERR, "%s: %m", a);
343
344    exit(EXIT_FAILURE);
345}
346
347int
348main(int argc, char *argv[])
349{
350/* Browse through  ATJOB_DIR, checking all the jobfiles wether they should
351 * be executed and or deleted. The queue is coded into the first byte of
352 * the job filename, the date (in minutes since Eon) as a hex number in the
353 * following eight bytes, followed by a dot and a serial number.  A file
354 * which has not been executed yet is denoted by its execute - bit set.
355 * For those files which are to be executed, run_file() is called, which forks
356 * off a child which takes care of I/O redirection, forks off another child
357 * for execution and yet another one, optionally, for sending mail.
358 * Files which already have run are removed during the next invocation.
359 */
360    DIR *spool;
361    struct dirent *dirent;
362    struct stat buf;
363    unsigned long ctm;
364    unsigned long jobno;
365    char queue;
366    time_t now, run_time;
367    char batch_name[] = "Z2345678901234";
368    uid_t batch_uid;
369    gid_t batch_gid;
370    int c;
371    int run_batch;
372    double load_avg = LOADAVG_MX;
373
374/* We don't need root privileges all the time; running under uid and gid daemon
375 * is fine.
376 */
377
378    RELINQUISH_PRIVS_ROOT(DAEMON_UID, DAEMON_GID)
379
380    openlog("atrun", LOG_PID, LOG_CRON);
381
382    opterr = 0;
383    errno = 0;
384    while((c=getopt(argc, argv, "dl:"))!= EOF)
385    {
386	switch (c)
387	{
388	case 'l':
389	    if (sscanf(optarg, "%lf", &load_avg) != 1)
390		perr("garbled option -l");
391	    if (load_avg <= 0.)
392		load_avg = LOADAVG_MX;
393	    break;
394
395	case 'd':
396	    debug ++;
397	    break;
398
399	case '?':
400	    perr("unknown option");
401	    break;
402
403	default:
404	    perr("idiotic option - aborted");
405	    break;
406	}
407    }
408
409    namep = argv[0];
410    if (chdir(ATJOB_DIR) != 0)
411	perr("Cannot change to " ATJOB_DIR);
412
413    /* Main loop. Open spool directory for reading and look over all the
414     * files in there. If the filename indicates that the job should be run
415     * and the x bit is set, fork off a child which sets its user and group
416     * id to that of the files and exec a /bin/sh which executes the shell
417     * script. Unlink older files if they should no longer be run.  For
418     * deletion, their r bit has to be turned on.
419     *
420     * Also, pick the oldest batch job to run, at most one per invocation of
421     * atrun.
422     */
423    if ((spool = opendir(".")) == NULL)
424	perr("Cannot read " ATJOB_DIR);
425
426    now = time(NULL);
427    run_batch = 0;
428    batch_uid = (uid_t) -1;
429    batch_gid = (gid_t) -1;
430
431    while ((dirent = readdir(spool)) != NULL) {
432	if (stat(dirent->d_name,&buf) != 0)
433	    perr("Cannot stat in " ATJOB_DIR);
434
435	/* We don't want directories
436	 */
437	if (!S_ISREG(buf.st_mode))
438	    continue;
439
440	if (sscanf(dirent->d_name,"%c%5lx%8lx",&queue,&jobno,&ctm) != 3)
441	    continue;
442
443	run_time = (time_t) ctm*60;
444
445	if ((S_IXUSR & buf.st_mode) && (run_time <=now)) {
446	    if (isupper(queue) && (strcmp(batch_name,dirent->d_name) > 0)) {
447		run_batch = 1;
448		strncpy(batch_name, dirent->d_name, sizeof(batch_name));
449		batch_uid = buf.st_uid;
450		batch_gid = buf.st_gid;
451	    }
452
453	/* The file is executable and old enough
454	 */
455	    if (islower(queue))
456		run_file(dirent->d_name, buf.st_uid, buf.st_gid);
457	}
458	/*  Delete older files
459	 */
460	if ((run_time < now) && !(S_IXUSR & buf.st_mode) && (S_IRUSR & buf.st_mode))
461	    unlink(dirent->d_name);
462    }
463    /* run the single batch file, if any
464    */
465    if (run_batch && (gloadavg() < load_avg))
466	run_file(batch_name, batch_uid, batch_gid);
467
468    closelog();
469    exit(EXIT_SUCCESS);
470}
471