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freebsd-dev/libexec/atrun/atrun.c

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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.
* 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.
*/
#ifndef lint
static const char rcsid[] =
"$FreeBSD$";
#endif /* not lint */
/* System Headers */
#include <sys/fcntl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/wait.h>
#include <sys/param.h>
#include <ctype.h>
#include <dirent.h>
#include <err.h>
#include <grp.h>
#include <pwd.h>
#include <signal.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <syslog.h>
#include <time.h>
#include <unistd.h>
#include <utmp.h>
#ifdef __FreeBSD__
#include <paths.h>
#else
#include <getopt.h>
#endif
#if (MAXLOGNAME-1) > UT_NAMESIZE
#define LOGNAMESIZE UT_NAMESIZE
#else
#define LOGNAMESIZE (MAXLOGNAME-1)
#endif
/* Local headers */
#include "gloadavg.h"
#define MAIN
#include "privs.h"
/* Macros */
#ifndef ATJOB_DIR
#define ATJOB_DIR "/usr/spool/atjobs/"
#endif
#ifndef ATSPOOL_DIR
#define ATSPOOL_DIR "/usr/spool/atspool/"
#endif
#ifndef LOADAVG_MX
#define LOADAVG_MX 1.5
#endif
/* File scope variables */
static int debug = 0;
void perr(const char *a);
static void usage(void);
/* Local functions */
static int
write_string(int fd, const char* a)
{
return write(fd, a, strlen(a));
}
#undef DEBUG_FORK
#ifdef DEBUG_FORK
static pid_t
myfork(void)
{
pid_t res;
res = fork();
if (res == 0)
kill(getpid(),SIGSTOP);
return res;
}
#define fork myfork
#endif
static void
run_file(const char *filename, uid_t uid, gid_t gid)
{
/* Run a file by spawning off a process which redirects I/O,
* spawns a subshell, then waits for it to complete and sends
* mail to the user.
*/
pid_t pid;
int fd_out, fd_in;
int queue;
char mailbuf[LOGNAMESIZE + 1], fmt[49];
char *mailname = NULL;
FILE *stream;
int send_mail = 0;
struct stat buf, lbuf;
off_t size;
struct passwd *pentry;
int fflags;
long nuid;
long ngid;
PRIV_START
if (chmod(filename, S_IRUSR) != 0)
{
perr("cannot change file permissions");
}
PRIV_END
pid = fork();
if (pid == -1)
perr("cannot fork");
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.
*/
pentry = getpwuid(uid);
if (pentry == NULL)
{
syslog(LOG_ERR,"Userid %lu not found - aborting job %s",
(unsigned long) uid, filename);
exit(EXIT_FAILURE);
}
PRIV_START
stream=fopen(filename, "r");
PRIV_END
#ifdef __FreeBSD__
if (pentry->pw_expire && time(NULL) >= pentry->pw_expire)
{
syslog(LOG_ERR, "Userid %lu is expired - aborting job %s",
(unsigned long) uid, filename);
exit(EXIT_FAILURE);
}
#endif
if (stream == NULL)
perr("cannot open input file");
if ((fd_in = dup(fileno(stream))) <0)
perr("error duplicating input file descriptor");
if (fstat(fd_in, &buf) == -1)
perr("error in fstat of input file descriptor");
if (lstat(filename, &lbuf) == -1)
perr("error in fstat of input file");
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,"Someboy 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");
fcntl(fd_in, F_SETFD, fflags & ~FD_CLOEXEC);
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 %ld does not match file uid %lu",
filename, nuid, (unsigned long)uid);
exit(EXIT_FAILURE);
}
if (ngid != gid) {
syslog(LOG_ERR,"Job %s - groupid %ld does not match file gid %lu",
filename, ngid, (unsigned long)gid);
exit(EXIT_FAILURE);
}
fclose(stream);
if (chdir(ATSPOOL_DIR) < 0)
perr("cannot chdir to " ATSPOOL_DIR);
/* Create a file to hold the output of the job we are about to run.
* Write the mail header.
*/
if((fd_out=open(filename,
O_WRONLY | O_CREAT | O_EXCL, S_IWUSR | S_IRUSR)) < 0)
perr("cannot create output file");
write_string(fd_out, "Subject: Output from your job ");
write_string(fd_out, filename);
write_string(fd_out, "\n\n");
fstat(fd_out, &buf);
size = buf.st_size;
close(STDIN_FILENO);
close(STDOUT_FILENO);
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");
close(fd_in);
close(fd_out);
if (chdir(ATJOB_DIR) < 0)
perr("cannot chdir to " ATJOB_DIR);
queue = *filename;
PRIV_START
nice(tolower(queue) - 'a');
if (initgroups(pentry->pw_name,pentry->pw_gid))
perr("cannot delete saved userids");
if (setgid(gid) < 0 || setegid(pentry->pw_gid) < 0)
perr("cannot change group");
if (setlogin(pentry->pw_name))
perr("cannot set login name");
if (setuid(uid) < 0 || seteuid(uid) < 0)
perr("cannot set user id");
if (chdir(pentry->pw_dir))
chdir("/");
if(execle("/bin/sh","sh",(char *) NULL, nenvp) != 0)
perr("exec failed for /bin/sh");
PRIV_END
}
/* We're the parent. Let's wait.
*/
close(fd_in);
close(fd_out);
waitpid(pid, (int *) NULL, 0);
/* Send mail. Unlink the output file first, so it is deleted after
* the run.
*/
stat(filename, &buf);
if (open(filename, O_RDONLY) != STDIN_FILENO)
perr("open of jobfile failed");
unlink(filename);
if ((buf.st_size != size) || send_mail)
{
PRIV_START
if (initgroups(pentry->pw_name,pentry->pw_gid))
perr("cannot delete saved userids");
if (setgid(gid) < 0 || setegid(pentry->pw_gid) < 0)
perr("cannot change group");
if (setlogin(pentry->pw_name))
perr("cannot set login name");
if (setuid(uid) < 0 || seteuid(uid) < 0)
perr("cannot set user id");
if (chdir(pentry->pw_dir))
chdir("/");
#ifdef __FreeBSD__
execl(_PATH_SENDMAIL, "sendmail", "-F", "Atrun Service",
"-odi", "-oem",
mailname, (char *) NULL);
#else
execl(MAIL_CMD, MAIL_CMD, mailname, (char *) NULL);
#endif
perr("exec failed for mail command");
PRIV_END
}
exit(EXIT_SUCCESS);
}
/* Global functions */
/* Needed in gloadavg.c */
void
perr(const char *a)
{
if (debug)
{
warn("%s", a);
}
else
syslog(LOG_ERR, "%s: %m", a);
exit(EXIT_FAILURE);
}
int
main(int argc, char *argv[])
{
/* Browse through ATJOB_DIR, 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;
unsigned long jobno;
char queue;
time_t now, run_time;
char batch_name[] = "Z2345678901234";
uid_t batch_uid;
gid_t batch_gid;
int c;
int run_batch;
double load_avg = LOADAVG_MX;
/* We don't need root privileges all the time; running under uid and gid daemon
* is fine.
*/
RELINQUISH_PRIVS_ROOT(DAEMON_UID, DAEMON_GID)
openlog("atrun", LOG_PID, LOG_CRON);
opterr = 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 = LOADAVG_MX;
break;
case 'd':
debug ++;
break;
case '?':
default:
usage();
}
}
if (chdir(ATJOB_DIR) != 0)
perr("cannot change to " ATJOB_DIR);
/* 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.
*
* Also, pick the oldest batch job to run, at most one per invocation of
* atrun.
*/
if ((spool = opendir(".")) == NULL)
perr("cannot read " ATJOB_DIR);
now = time(NULL);
run_batch = 0;
batch_uid = (uid_t) -1;
batch_gid = (gid_t) -1;
while ((dirent = readdir(spool)) != NULL) {
if (stat(dirent->d_name,&buf) != 0)
perr("cannot stat in " ATJOB_DIR);
/* We don't want directories
*/
if (!S_ISREG(buf.st_mode))
continue;
if (sscanf(dirent->d_name,"%c%5lx%8lx",&queue,&jobno,&ctm) != 3)
continue;
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;
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);
}
/* Delete older files
*/
if ((run_time < now) && !(S_IXUSR & buf.st_mode) && (S_IRUSR & buf.st_mode))
unlink(dirent->d_name);
}
/* run the single batch file, if any
*/
if (run_batch && (gloadavg() < load_avg))
run_file(batch_name, batch_uid, batch_gid);
closelog();
exit(EXIT_SUCCESS);
}
static void
usage(void)
{
if (debug)
fprintf(stderr, "usage: atrun [-l load_avg] [-d]\n");
else
syslog(LOG_ERR, "usage: atrun [-l load_avg] [-d]");
exit(EXIT_FAILURE);
}
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