NetBSD/libexec/atrun/atrun.c

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/* $NetBSD: atrun.c,v 1.7 1999/08/16 03:08:33 simonb Exp $ */
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/*
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* atrun.c - run jobs queued by at; run with root privileges.
* Copyright (C) 1993, 1994 Thomas Koenig
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. The name of the author(s) may not be used to endorse or promote
* products derived from this software without specific prior written
* permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR(S) ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL THE AUTHOR(S) BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
/* System Headers */
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#include <sys/types.h>
#include <sys/stat.h>
#include <sys/wait.h>
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#include <sys/param.h>
#include <ctype.h>
#include <dirent.h>
#include <errno.h>
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#include <fcntl.h>
#include <pwd.h>
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#include <grp.h>
#include <signal.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <unistd.h>
#include <syslog.h>
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#include <utmp.h>
#include <paths.h>
/* Local headers */
#define MAIN
#include "privs.h"
#include "pathnames.h"
#include "atrun.h"
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/* File scope defines */
#if (MAXLOGNAME-1) > UT_NAMESIZE
#define LOGNAMESIZE UT_NAMESIZE
#else
#define LOGNAMESIZE (MAXLOGNAME-1)
#endif
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/* File scope variables */
static char *namep;
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#if 0
static char rcsid[] = "$OpenBSD: atrun.c,v 1.7 1997/09/08 22:12:10 millert Exp $";
#else
__RCSID("$NetBSD: atrun.c,v 1.7 1999/08/16 03:08:33 simonb Exp $");
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#endif
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static int debug = 0;
/* Local functions */
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static void perr __P((const char *));
static void perr2 __P((char *, char *));
static int write_string __P((int, const char *));
static void run_file __P((const char *, uid_t, gid_t));
static void become_user __P((struct passwd *, uid_t));
int main __P((int, char *[]));
static void
perr(a)
const char *a;
{
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if (debug)
perror(a);
else
syslog(LOG_ERR, "%s: %m", a);
exit(EXIT_FAILURE);
}
static void
perr2(a, b)
char *a, *b;
{
if (debug) {
(void)fputs(a, stderr);
perror(b);
} else
syslog(LOG_ERR, "%s%s: %m", a, b);
exit(EXIT_FAILURE);
}
static int
write_string(fd, a)
int fd;
const char *a;
{
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return(write(fd, a, strlen(a)));
}
static void
become_user(pentry, uid)
struct passwd *pentry;
uid_t uid;
{
if (initgroups(pentry->pw_name, pentry->pw_gid) < 0)
perr("Cannot init group list");
if (setegid(pentry->pw_gid) < 0 || setgid(pentry->pw_gid) < 0)
perr("Cannot change primary group");
if (setlogin(pentry->pw_name) < 0)
perr("Cannot set login name");
if (setuid(uid) < 0 || seteuid(uid) < 0)
perr("Cannot set user id");
if (chdir(pentry->pw_dir) < 0)
chdir("/");
}
static void
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run_file(filename, uid, gid)
const char *filename;
uid_t uid;
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gid_t gid;
{
/*
* Run a file by by spawning off a process which redirects I/O,
* spawns a subshell, then waits for it to complete and spawns another
* process to send mail to the user.
*/
pid_t pid;
int fd_out, fd_in;
int queue;
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char mailbuf[LOGNAMESIZE + 1], fmt[49];
char *mailname = NULL;
FILE *stream;
int send_mail = 0;
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struct stat buf, lbuf;
off_t size;
struct passwd *pentry;
int fflags;
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uid_t nuid;
gid_t ngid;
PRIV_START
if (chmod(filename, S_IRUSR) != 0)
perr("Cannot change file permissions");
PRIV_END
pid = fork();
if (pid == -1)
perr("Cannot fork");
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else if (pid != 0)
return;
/*
* Let's see who we mail to. Hopefully, we can read it from the
* command file; if not, send it to the owner, or, failing that, to
* root.
*/
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pentry = getpwuid(uid);
if (pentry == NULL) {
syslog(LOG_ERR,"Userid %u not found - aborting job %s",
uid, filename);
exit(EXIT_FAILURE);
}
PRIV_START
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stream = fopen(filename, "r");
PRIV_END
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if (pentry->pw_expire && time(NULL) >= pentry->pw_expire) {
syslog(LOG_ERR, "Userid %u has expired - aborting job %s",
uid, filename);
exit(EXIT_FAILURE);
}
if (stream == NULL)
perr("Cannot open input file");
if ((fd_in = dup(fileno(stream))) < 0)
perr("Error duplicating input file descriptor");
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if (fstat(fd_in, &buf) == -1)
perr("Error in fstat of input file descriptor");
PRIV_START
if (lstat(filename, &lbuf) == -1)
perr("Error in lstat of input file");
PRIV_END
if (S_ISLNK(lbuf.st_mode)) {
syslog(LOG_ERR, "Symbolic link encountered in job %s - aborting",
filename);
exit(EXIT_FAILURE);
}
if ((lbuf.st_dev != buf.st_dev) || (lbuf.st_ino != buf.st_ino) ||
(lbuf.st_uid != buf.st_uid) || (lbuf.st_gid != buf.st_gid) ||
(lbuf.st_size!=buf.st_size)) {
syslog(LOG_ERR, "Somebody changed files from under us for job %s - aborting", filename);
exit(EXIT_FAILURE);
}
if (buf.st_nlink > 1) {
syslog(LOG_ERR, "Somebody is trying to run a linked script for job %s",
filename);
exit(EXIT_FAILURE);
}
if ((fflags = fcntl(fd_in, F_GETFD)) < 0)
perr("Error in fcntl");
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(void)fcntl(fd_in, F_SETFD, fflags & ~FD_CLOEXEC);
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(void)snprintf(fmt, sizeof(fmt),
"#!/bin/sh\n# atrun uid=%%ld gid=%%ld\n# mail %%%ds %%d",
LOGNAMESIZE);
if (fscanf(stream, fmt, &nuid, &ngid, mailbuf, &send_mail) != 4) {
syslog(LOG_ERR, "File %s is in wrong format - aborting",
filename);
exit(EXIT_FAILURE);
}
if (mailbuf[0] == '-') {
syslog(LOG_ERR, "illegal mail name %s in %s", mailbuf, filename);
exit(EXIT_FAILURE);
}
mailname = mailbuf;
if (nuid != uid) {
syslog(LOG_ERR, "Job %s - userid %u does not match file uid %u",
filename, nuid, uid);
exit(EXIT_FAILURE);
}
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if (ngid != gid) {
syslog(LOG_ERR, "Job %s - groupid %u does not match file gid %u",
filename, ngid, gid);
exit(EXIT_FAILURE);
}
(void)fclose(stream);
PRIV_START
if (chdir(_PATH_ATSPOOL) < 0)
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perr2("Cannot chdir to ", _PATH_ATSPOOL);
/*
* Create a file to hold the output of the job we are about to
* run. Write the mail header.
*/
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if ((fd_out = open(filename,
O_WRONLY | O_CREAT | O_EXCL, S_IWUSR | S_IRUSR)) < 0)
perr("Cannot create output file");
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PRIV_END
write_string(fd_out, "To: ");
write_string(fd_out, mailname);
write_string(fd_out, "\nSubject: Output from your job ");
write_string(fd_out, filename);
write_string(fd_out, "\n\n");
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if (fstat(fd_out, &buf) == -1)
perr("Error in fstat of output file descriptor");
size = buf.st_size;
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(void)close(STDIN_FILENO);
(void)close(STDOUT_FILENO);
(void)close(STDERR_FILENO);
pid = fork();
if (pid < 0)
perr("Error in fork");
else if (pid == 0) {
char *nul = NULL;
char **nenvp = &nul;
/*
* Set up things for the child; we want standard input from
* the input file, and standard output and error sent to
* our output file.
*/
if (lseek(fd_in, (off_t) 0, SEEK_SET) < 0)
perr("Error in lseek");
if (dup(fd_in) != STDIN_FILENO)
perr("Error in I/O redirection");
if (dup(fd_out) != STDOUT_FILENO)
perr("Error in I/O redirection");
if (dup(fd_out) != STDERR_FILENO)
perr("Error in I/O redirection");
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(void)close(fd_in);
(void)close(fd_out);
PRIV_START
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if (chdir(_PATH_ATJOBS) < 0)
perr2("Cannot chdir to ", _PATH_ATJOBS);
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queue = *filename;
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if (queue > 'b')
nice(queue - 'b');
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become_user(pentry, uid);
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if (execle("/bin/sh", "sh", (char *)NULL, nenvp) != 0)
perr("Exec failed for /bin/sh");
PRIV_END
}
/* We're the parent. Let's wait. */
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(void)close(fd_in);
(void)close(fd_out);
waitpid(pid, (int *)NULL, 0);
/*
* Send mail. Unlink the output file first, so it is deleted
* after the run.
*/
PRIV_START
if (stat(filename, &buf) == -1)
perr("Error in stat of output file");
if (open(filename, O_RDONLY) != STDIN_FILENO)
perr("Open of jobfile failed");
(void)unlink(filename);
PRIV_END
if ((buf.st_size != size) || send_mail) {
/* Fork off a child for sending mail */
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PRIV_START
become_user(pentry, uid);
execl(_PATH_SENDMAIL, "sendmail", "-F", "Atrun Service",
"-odi", "-oem", "-t", (char *) NULL);
perr("Exec failed for mail command");
PRIV_END
}
exit(EXIT_SUCCESS);
}
/* Global functions */
int
main(argc, argv)
int argc;
char *argv[];
{
/*
* Browse through _PATH_ATJOBS, checking all the jobfiles wether
* they should be executed and or deleted. The queue is coded into
* the first byte of the job filename, the date (in minutes since
* Eon) as a hex number in the following eight bytes, followed by
* a dot and a serial number. A file which has not been executed
* yet is denoted by its execute - bit set. For those files which
* are to be executed, run_file() is called, which forks off a
* child which takes care of I/O redirection, forks off another
* child for execution and yet another one, optionally, for sending
* mail. Files which already have run are removed during the
* next invocation.
*/
DIR *spool;
struct dirent *dirent;
struct stat buf;
unsigned long ctm;
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int jobno;
char queue;
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time_t now, run_time;
char batch_name[] = "Z2345678901234";
uid_t batch_uid;
gid_t batch_gid;
int c;
int run_batch;
double la, load_avg = ATRUN_MAXLOAD;
/*
* We don't need root privileges all the time; running under uid
* and gid nobody is fine except for privileged operations.
*/
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RELINQUISH_PRIVS_ROOT(NOBODY_UID, NOBODY_GID)
openlog("atrun", LOG_PID, LOG_CRON);
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opterr = 0;
errno = 0;
while ((c = getopt(argc, argv, "dl:")) != -1) {
switch (c) {
case 'l':
if (sscanf(optarg, "%lf", &load_avg) != 1)
perr("garbled option -l");
if (load_avg <= 0.)
load_avg = ATRUN_MAXLOAD;
break;
case 'd':
debug++;
break;
case '?':
perr("unknown option");
break;
default:
perr("idiotic option - aborted");
break;
}
}
namep = argv[0];
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PRIV_START
if (chdir(_PATH_ATJOBS) != 0)
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perr2("Cannot change to ", _PATH_ATJOBS);
/*
* Main loop. Open spool directory for reading and look over all
* the files in there. If the filename indicates that the job
* should be run and the x bit is set, fork off a child which sets
* its user and group id to that of the files and exec a /bin/sh
* which executes the shell script. Unlink older files if they
* should no longer be run. For deletion, their r bit has to be
* turned on.
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*
* Also, pick the oldest batch job to run, at most one per
* invocation of atrun.
*/
if ((spool = opendir(".")) == NULL)
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perr2("Cannot read ", _PATH_ATJOBS);
PRIV_END
now = time(NULL);
run_batch = 0;
batch_uid = (uid_t) -1;
batch_gid = (gid_t) -1;
while ((dirent = readdir(spool)) != NULL) {
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PRIV_START
if (stat(dirent->d_name, &buf) != 0)
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perr2("Cannot stat in ", _PATH_ATJOBS);
PRIV_END
/* We don't want directories */
if (!S_ISREG(buf.st_mode))
continue;
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if (sscanf(dirent->d_name, "%c%5x%8lx", &queue, &jobno, &ctm) != 3)
continue;
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run_time = (time_t) ctm * 60;
if ((S_IXUSR & buf.st_mode) && (run_time <= now)) {
if (isupper(queue) &&
(strcmp(batch_name, dirent->d_name) > 0)) {
run_batch = 1;
(void)strncpy(batch_name, dirent->d_name,
sizeof(batch_name));
batch_uid = buf.st_uid;
batch_gid = buf.st_gid;
}
/* The file is executable and old enough */
if (islower(queue))
run_file(dirent->d_name, buf.st_uid, buf.st_gid);
}
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/* Delete older files */
if ((run_time < now) && !(S_IXUSR & buf.st_mode) &&
(S_IRUSR & buf.st_mode)) {
PRIV_START
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(void)unlink(dirent->d_name);
PRIV_END
}
}
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/* Run the single batch file, if any */
if (run_batch && ((getloadavg(&la, 1) == 1) && la < load_avg))
run_file(batch_name, batch_uid, batch_gid);
closelog();
exit(EXIT_SUCCESS);
}