xref: /openbsd-src/usr.sbin/cron/atrun.c (revision 3a50f0a93a2072911d0ba6ababa815fb04bf9a71)

/*	$OpenBSD: atrun.c,v 1.54 2022/12/28 21:30:16 jmc Exp $	*/

/*
 * Copyright (c) 2002-2003 Todd C. Miller <millert@openbsd.org>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 *
 * Sponsored in part by the Defense Advanced Research Projects
 * Agency (DARPA) and Air Force Research Laboratory, Air Force
 * Materiel Command, USAF, under agreement number F39502-99-1-0512.
 */

#include <sys/types.h>
#include <sys/resource.h>
#include <sys/stat.h>
#include <sys/time.h>
#include <sys/wait.h>

#include <bitstring.h>		/* for structs.h */
#include <bsd_auth.h>
#include <ctype.h>
#include <dirent.h>
#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#include <login_cap.h>
#include <pwd.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <syslog.h>
#include <time.h>
#include <unistd.h>

#include "config.h"
#include "pathnames.h"
#include "macros.h"
#include "structs.h"
#include "funcs.h"
#include "globals.h"

static void run_job(const atjob *, int, const char *);

/*
 * Scan the at jobs dir and build up a list of jobs found.
 */
int
scan_atjobs(at_db **db, struct timespec *ts)
{
	DIR *atdir = NULL;
	int dfd, pending;
	const char *errstr;
	time_t run_time;
	char *queue;
	at_db *new_db, *old_db = *db;
	atjob *job;
	struct dirent *file;
	struct stat sb;

	dfd = open(_PATH_AT_SPOOL, O_RDONLY|O_DIRECTORY|O_CLOEXEC);
	if (dfd == -1) {
		syslog(LOG_ERR, "(CRON) OPEN FAILED (%s)", _PATH_AT_SPOOL);
		return (0);
	}
	if (fstat(dfd, &sb) != 0) {
		syslog(LOG_ERR, "(CRON) FSTAT FAILED (%s)", _PATH_AT_SPOOL);
		close(dfd);
		return (0);
	}
	if (old_db != NULL && timespeccmp(&old_db->mtime, &sb.st_mtim, ==)) {
		close(dfd);
		return (0);
	}

	if ((atdir = fdopendir(dfd)) == NULL) {
		syslog(LOG_ERR, "(CRON) OPENDIR FAILED (%s)", _PATH_AT_SPOOL);
		close(dfd);
		return (0);
	}

	if ((new_db = malloc(sizeof(*new_db))) == NULL) {
		closedir(atdir);
		return (0);
	}
	new_db->mtime = sb.st_mtim;	/* stash at dir mtime */
	TAILQ_INIT(&new_db->jobs);

	pending = 0;
	while ((file = readdir(atdir)) != NULL) {
		if (fstatat(dfd, file->d_name, &sb, AT_SYMLINK_NOFOLLOW) != 0 ||
		    !S_ISREG(sb.st_mode))
			continue;

		/*
		 * at jobs are named as RUNTIME.QUEUE
		 * RUNTIME is the time to run in seconds since the epoch
		 * QUEUE is a letter that designates the job's queue
		 */
		if ((queue = strchr(file->d_name, '.')) == NULL)
			continue;
		*queue++ = '\0';
		run_time = strtonum(file->d_name, 0, LLONG_MAX, &errstr);
		if (errstr != NULL)
			continue;
		if (!isalpha((unsigned char)*queue))
			continue;

		job = malloc(sizeof(*job));
		if (job == NULL) {
			while ((job = TAILQ_FIRST(&new_db->jobs))) {
				TAILQ_REMOVE(&new_db->jobs, job, entries);
				free(job);
			}
			free(new_db);
			closedir(atdir);
			return (0);
		}
		job->uid = sb.st_uid;
		job->gid = sb.st_gid;
		job->queue = *queue;
		job->run_time = run_time;
		TAILQ_INSERT_TAIL(&new_db->jobs, job, entries);
		if (ts != NULL && run_time <= ts->tv_sec)
			pending = 1;
	}
	closedir(atdir);

	/* Free up old at db and install new one */
	if (old_db != NULL) {
		while ((job = TAILQ_FIRST(&old_db->jobs))) {
			TAILQ_REMOVE(&old_db->jobs, job, entries);
			free(job);
		}
		free(old_db);
	}
	*db = new_db;

	return (pending);
}

/*
 * Loop through the at job database and run jobs whose time have come.
 */
void
atrun(at_db *db, double batch_maxload, time_t now)
{
	char atfile[PATH_MAX];
	struct stat sb;
	double la;
	int dfd, len;
	atjob *job, *tjob, *batch = NULL;

	if (db == NULL)
		return;

	dfd = open(_PATH_AT_SPOOL, O_RDONLY|O_DIRECTORY|O_CLOEXEC);
	if (dfd == -1) {
		syslog(LOG_ERR, "(CRON) OPEN FAILED (%s)", _PATH_AT_SPOOL);
		return;
	}

	TAILQ_FOREACH_SAFE(job, &db->jobs, entries, tjob) {
		/* Skip jobs in the future */
		if (job->run_time > now)
			continue;

		len = snprintf(atfile, sizeof(atfile), "%lld.%c",
		    (long long)job->run_time, job->queue);
		if (len < 0 || len >= sizeof(atfile)) {
			TAILQ_REMOVE(&db->jobs, job, entries);
			free(job);
			continue;
		}

		if (fstatat(dfd, atfile, &sb, AT_SYMLINK_NOFOLLOW) != 0) {
			TAILQ_REMOVE(&db->jobs, job, entries);
			free(job);
			continue;		/* disappeared from queue */
		}
		if (!S_ISREG(sb.st_mode)) {
			syslog(LOG_WARNING, "(CRON) NOT REGULAR (%s)",
			    atfile);
			TAILQ_REMOVE(&db->jobs, job, entries);
			free(job);
			continue;		/* was a file, no longer is */
		}

		/*
		 * Pending jobs have the user execute bit set.
		 */
		if (sb.st_mode & S_IXUSR) {
			/* new job to run */
			if (isupper(job->queue)) {
				/* we run one batch job per atrun() call */
				if (batch == NULL ||
				    job->run_time < batch->run_time)
					batch = job;
			} else {
				/* normal at job */
				run_job(job, dfd, atfile);
				TAILQ_REMOVE(&db->jobs, job, entries);
				free(job);
			}
		}
	}

	/* Run a single batch job if there is one pending. */
	if (batch != NULL
	    && (batch_maxload == 0.0 ||
	    ((getloadavg(&la, 1) == 1) && la <= batch_maxload))
	    ) {
		len = snprintf(atfile, sizeof(atfile), "%lld.%c",
		    (long long)batch->run_time, batch->queue);
		if (len < 0 || len >= sizeof(atfile))
			;
		else
			run_job(batch, dfd, atfile);
		TAILQ_REMOVE(&db->jobs, batch, entries);
		free(job);
	}

	close(dfd);
}

/*
 * Check the at job header for sanity and extract the
 * uid, gid, mailto user and always_mail flag.
 *
 * The header should look like this:
 * #!/bin/sh
 * # atrun uid=123 gid=123
 * # mail                         joeuser 0
 */
static int
parse_header(FILE *fp, uid_t *nuid, gid_t *ngid, char *mailto, int *always_mail)
{
	char *cp, *ep, *line = NULL;
	const char *errstr;
	size_t size = 0;
	int lineno = 0;
	ssize_t len;
	int ret = -1;

	for (lineno = 1; (len = getline(&line, &size, fp)) != -1; lineno++) {
		if (line[--len] != '\n')
			break;
		line[len] = '\0';

		switch (lineno) {
		case 1:
			if (strcmp(line, "#!/bin/sh") != 0)
			    goto done;
			break;
		case 2:
			if (strncmp(line, "# atrun uid=", 12) != 0)
			    goto done;

			/* Pull out uid */
			cp = line + 12;
			if ((ep = strchr(cp, ' ')) == NULL)
				goto done;
			*ep++ = '\0';
			*nuid = strtonum(cp, 0, UID_MAX - 1, &errstr);
			if (errstr != NULL)
				goto done;

			/* Pull out gid */
			if (strncmp(ep, "gid=", 4) != 0)
				goto done;
			cp = ep + 4;
			*ngid = strtonum(cp, 0, GID_MAX - 1, &errstr);
			if (errstr != NULL)
				goto done;
			break;
		case 3:
			/* Pull out mailto user (and always_mail flag) */
			if (strncmp(line, "# mail ", 7) != 0)
				goto done;
			for (cp = line + 7; *cp == ' '; cp++)
				continue;
			if (*cp == '\0')
				goto done;
			for (ep = cp; *ep != ' ' && *ep != '\0'; ep++)
				continue;
			if (*ep != ' ')
				goto done;
			*ep++ = '\0';
			if (strlcpy(mailto, cp, MAX_UNAME) >= MAX_UNAME)
				goto done;
			*always_mail = *ep == '1';

			/* success */
			ret = 0;
			goto done;
		default:
			/* can't happen */
			goto done;
		}
	}
done:
	free(line);
	return ret;
}

/*
 * Run the specified job contained in atfile.
 */
static void
run_job(const atjob *job, int dfd, const char *atfile)
{
	struct stat sb;
	struct passwd *pw;
	login_cap_t *lc;
	auth_session_t *as;
	pid_t pid;
	uid_t nuid;
	gid_t ngid;
	FILE *fp;
	int waiter;
	size_t nread;
	char mailto[MAX_UNAME], buf[BUFSIZ];
	int fd, always_mail;
	int output_pipe[2];
	char *nargv[2], *nenvp[1];

	/* Open the file and unlink it so we don't try running it again. */
	if ((fd = openat(dfd, atfile, O_RDONLY|O_NONBLOCK|O_NOFOLLOW)) == -1) {
		syslog(LOG_ERR, "(CRON) CAN'T OPEN (%s)", atfile);
		return;
	}
	unlinkat(dfd, atfile, 0);

	/* Fork so other pending jobs don't have to wait for us to finish. */
	switch (fork()) {
	case 0:
		/* child */
		break;
	case -1:
		/* error */
		syslog(LOG_ERR, "(CRON) CAN'T FORK (%m)");
		/* FALLTHROUGH */
	default:
		/* parent */
		close(fd);
		return;
	}

	/* Close fds opened by the parent. */
	close(cronSock);
	close(dfd);

	/*
	 * We don't want the main cron daemon to wait for our children--
	 * we will do it ourselves via waitpid().
	 */
	(void) signal(SIGCHLD, SIG_DFL);

	/*
	 * Verify the user still exists and their account has not expired.
	 */
	pw = getpwuid(job->uid);
	if (pw == NULL) {
		syslog(LOG_WARNING, "(CRON) ORPHANED JOB (%s)", atfile);
		_exit(EXIT_FAILURE);
	}
	if (pw->pw_expire && time(NULL) >= pw->pw_expire) {
		syslog(LOG_NOTICE, "(%s) ACCOUNT EXPIRED, JOB ABORTED (%s)",
		    pw->pw_name, atfile);
		_exit(EXIT_FAILURE);
	}

	/* Sanity checks */
	if (fstat(fd, &sb) == -1) {
		syslog(LOG_ERR, "(%s) FSTAT FAILED (%s)", pw->pw_name, atfile);
		_exit(EXIT_FAILURE);
	}
	if (!S_ISREG(sb.st_mode)) {
		syslog(LOG_WARNING, "(%s) NOT REGULAR (%s)", pw->pw_name,
		    atfile);
		_exit(EXIT_FAILURE);
	}
	if ((sb.st_mode & ALLPERMS) != (S_IRUSR | S_IWUSR | S_IXUSR)) {
		syslog(LOG_WARNING, "(%s) BAD FILE MODE (%s)", pw->pw_name,
		    atfile);
		_exit(EXIT_FAILURE);
	}
	if (sb.st_uid != 0 && sb.st_uid != job->uid) {
		syslog(LOG_WARNING, "(%s) WRONG FILE OWNER (%s)", pw->pw_name,
		    atfile);
		_exit(EXIT_FAILURE);
	}
	if (sb.st_gid != cron_gid) {
		syslog(LOG_WARNING, "(%s) WRONG FILE GROUP (%s)", pw->pw_name,
		    atfile);
		_exit(EXIT_FAILURE);
	}
	if (sb.st_nlink > 1) {
		syslog(LOG_WARNING, "(%s) BAD LINK COUNT (%s)", pw->pw_name,
		    atfile);
		_exit(EXIT_FAILURE);
	}
	if ((fp = fdopen(dup(fd), "r")) == NULL) {
		syslog(LOG_ERR, "(CRON) DUP FAILED (%m)");
		_exit(EXIT_FAILURE);
	}
	if (parse_header(fp, &nuid, &ngid, mailto, &always_mail) == -1) {
		syslog(LOG_ERR, "(%s) BAD FILE FORMAT (%s)", pw->pw_name,
		    atfile);
		_exit(EXIT_FAILURE);
	}
	(void)fclose(fp);
	if (!safe_p(pw->pw_name, mailto))
		_exit(EXIT_FAILURE);
	if ((uid_t)nuid != job->uid) {
		syslog(LOG_WARNING, "(%s) UID MISMATCH (%s)", pw->pw_name,
		    atfile);
		_exit(EXIT_FAILURE);
	}
	if ((gid_t)ngid != job->gid) {
		syslog(LOG_WARNING, "(%s) GID MISMATCH (%s)", pw->pw_name,
		    atfile);
		_exit(EXIT_FAILURE);
	}

	/* mark ourselves as different to PS command watchers */
	setproctitle("atrun %s", atfile);

	if (pipe(output_pipe) != 0) {	/* child's stdout/stderr */
		syslog(LOG_ERR, "(CRON) PIPE (%m)");
		_exit(EXIT_FAILURE);
	}

	/* Fork again, child will run the job, parent will catch output. */
	switch ((pid = fork())) {
	case -1:
		syslog(LOG_ERR, "(CRON) CAN'T FORK (%m)");
		_exit(EXIT_FAILURE);
		/*NOTREACHED*/
	case 0:
		/* Write log message now that we have our real pid. */
		syslog(LOG_INFO, "(%s) ATJOB (%s)", pw->pw_name, atfile);

		/* Connect grandchild's stdin to the at job file. */
		if (lseek(fd, 0, SEEK_SET) == -1) {
			syslog(LOG_ERR, "(CRON) LSEEK (%m)");
			_exit(EXIT_FAILURE);
		}
		if (fd != STDIN_FILENO) {
			dup2(fd, STDIN_FILENO);
			close(fd);
		}

		/* Connect stdout/stderr to the pipe from our parent. */
		if (output_pipe[WRITE_PIPE] != STDOUT_FILENO) {
			dup2(output_pipe[WRITE_PIPE], STDOUT_FILENO);
			close(output_pipe[WRITE_PIPE]);
		}
		dup2(STDOUT_FILENO, STDERR_FILENO);
		close(output_pipe[READ_PIPE]);

		(void) setsid();

		/*
		 * From this point on, anything written to stderr will be
		 * mailed to the user as output.
		 */

		/* Setup execution environment as per login.conf */
		if ((lc = login_getclass(pw->pw_class)) == NULL) {
			warnx("unable to get login class for %s",
			    pw->pw_name);
			syslog(LOG_ERR, "(CRON) CAN'T GET LOGIN CLASS (%s)",
			    pw->pw_name);
			_exit(EXIT_FAILURE);

		}
		if (setusercontext(lc, pw, pw->pw_uid, LOGIN_SETALL)) {
			warn("setusercontext failed for %s", pw->pw_name);
			syslog(LOG_ERR, "(%s) SETUSERCONTEXT FAILED (%m)",
			    pw->pw_name);
			_exit(EXIT_FAILURE);
		}

		/* Run any approval scripts. */
		as = auth_open();
		if (as == NULL || auth_setpwd(as, pw) != 0) {
			warn("auth_setpwd");
			syslog(LOG_ERR, "(%s) AUTH_SETPWD FAILED (%m)",
			    pw->pw_name);
			_exit(EXIT_FAILURE);
		}
		if (auth_approval(as, lc, pw->pw_name, "cron") <= 0) {
			warnx("approval failed for %s", pw->pw_name);
			syslog(LOG_ERR, "(%s) APPROVAL FAILED (cron)",
			    pw->pw_name);
			_exit(EXIT_FAILURE);
		}
		auth_close(as);
		login_close(lc);

		/* If this is a low priority job, nice ourself. */
		if (job->queue > 'b') {
			if (setpriority(PRIO_PROCESS, 0, job->queue - 'b') != 0)
				syslog(LOG_ERR, "(%s) CAN'T NICE (%m)",
				    pw->pw_name);
		}

		(void) signal(SIGPIPE, SIG_DFL);

		/*
		 * Exec /bin/sh with stdin connected to the at job file
		 * and stdout/stderr hooked up to our parent.
		 * The at file will set the environment up for us.
		 */
		nargv[0] = "sh";
		nargv[1] = NULL;
		nenvp[0] = NULL;
		if (execve(_PATH_BSHELL, nargv, nenvp) != 0) {
			warn("unable to execute %s", _PATH_BSHELL);
			syslog(LOG_ERR, "(%s) CAN'T EXEC (%s: %m)", pw->pw_name,
			    _PATH_BSHELL);
			_exit(EXIT_FAILURE);
		}
		break;
	default:
		/* parent */
		break;
	}

	/* Close the atfile's fd and the end of the pipe we don't use. */
	close(fd);
	close(output_pipe[WRITE_PIPE]);

	/* Read piped output (if any) from the at job. */
	if ((fp = fdopen(output_pipe[READ_PIPE], "r")) == NULL) {
		syslog(LOG_ERR, "(%s) FDOPEN (%m)", pw->pw_name);
		(void) _exit(EXIT_FAILURE);
	}
	nread = fread(buf, 1, sizeof(buf), fp);
	if (nread != 0 || always_mail) {
		FILE	*mail;
		pid_t	mailpid;
		size_t	bytes = 0;
		int	status = 0;
		char	mailcmd[MAX_COMMAND];
		char	hostname[HOST_NAME_MAX + 1];

		if (gethostname(hostname, sizeof(hostname)) != 0)
			strlcpy(hostname, "unknown", sizeof(hostname));
		if (snprintf(mailcmd, sizeof mailcmd, MAILFMT,
		    MAILARG) >= sizeof mailcmd) {
			syslog(LOG_ERR, "(%s) ERROR (mailcmd too long)",
			    pw->pw_name);
			(void) _exit(EXIT_FAILURE);
		}
		if (!(mail = cron_popen(mailcmd, "w", pw, &mailpid))) {
			syslog(LOG_ERR, "(%s) POPEN (%s)", pw->pw_name, mailcmd);
			(void) _exit(EXIT_FAILURE);
		}
		fprintf(mail, "From: %s (Atrun Service)\n", pw->pw_name);
		fprintf(mail, "To: %s\n", mailto);
		fprintf(mail, "Subject: Output from \"at\" job\n");
		fprintf(mail, "Auto-Submitted: auto-generated\n");
		fprintf(mail, "\nYour \"at\" job on %s\n\"%s/%s\"\n",
		    hostname, _PATH_AT_SPOOL, atfile);
		fprintf(mail, "\nproduced the following output:\n\n");

		/* Pipe the job's output to sendmail. */
		do {
			bytes += nread;
			fwrite(buf, nread, 1, mail);
		} while ((nread = fread(buf, 1, sizeof(buf), fp)) != 0);

		/*
		 * If the mailer exits with non-zero exit status, log
		 * this fact so the problem can (hopefully) be debugged.
		 */
		if ((status = cron_pclose(mail, mailpid)) != 0) {
			syslog(LOG_NOTICE, "(%s) MAIL (mailed %zu byte%s of "
			    "output but got status 0x%04x)", pw->pw_name,
			    bytes, (bytes == 1) ? "" : "s", status);
		}
	}

	fclose(fp);	/* also closes output_pipe[READ_PIPE] */

	/* Wait for grandchild to die.  */
	for (;;) {
		if (waitpid(pid, &waiter, 0) == -1) {
			if (errno == EINTR)
				continue;
			break;
		} else {
			/*
			if (WIFSIGNALED(waiter) && WCOREDUMP(waiter))
				Debug(DPROC, (", dumped core"))
			*/
			break;
		}
	}
	_exit(EXIT_SUCCESS);
}