NetBSD/usr.sbin/cron/crontab.c

/*	$NetBSD: crontab.c,v 1.27 2006/04/25 18:02:02 christos Exp $	*/

/* Copyright 1988,1990,1993,1994 by Paul Vixie
 * All rights reserved
 *
 * Distribute freely, except: don't remove my name from the source or
 * documentation (don't take credit for my work), mark your changes (don't
 * get me blamed for your possible bugs), don't alter or remove this
 * notice.  May be sold if buildable source is provided to buyer.  No
 * warrantee of any kind, express or implied, is included with this
 * software; use at your own risk, responsibility for damages (if any) to
 * anyone resulting from the use of this software rests entirely with the
 * user.
 *
 * Send bug reports, bug fixes, enhancements, requests, flames, etc., and
 * I'll try to keep a version up to date.  I can be reached as follows:
 * Paul Vixie          <paul@vix.com>          uunet!decwrl!vixie!paul
 */

#include <sys/cdefs.h>
#if !defined(lint) && !defined(LINT)
#if 0
static char rcsid[] = "Id: crontab.c,v 2.13 1994/01/17 03:20:37 vixie Exp";
#else
__RCSID("$NetBSD: crontab.c,v 1.27 2006/04/25 18:02:02 christos Exp $");
#endif
#endif

/* crontab - install and manage per-user crontab files
 * vix 02may87 [RCS has the rest of the log]
 * vix 26jan87 [original]
 */


#define MAXCRONTABSIZE	(1024*256)	/* max crontab size == 256 KB */


#define	MAIN_PROGRAM


#include "cron.h"
#include <errno.h>
#include <fcntl.h>
#include <sys/file.h>
#include <sys/stat.h>
#ifdef USE_UTIMES
# include <sys/time.h>
#else
# include <utime.h>
#endif
#if defined(POSIX)
# include <locale.h>
#endif
#include <time.h>
#include <signal.h>


#define NHEADER_LINES 3


enum opt_t	{ opt_unknown, opt_list, opt_delete, opt_edit, opt_replace };

#if DEBUGGING
static char	*Options[] = { "???", "list", "delete", "edit", "replace" };
#endif


static	PID_T		Pid;
static	char		User[MAX_UNAME], RealUser[MAX_UNAME];
static	char		Filename[MAX_FNAME];
static	FILE		*NewCrontab;
static	int		CheckErrorCount;
static	enum opt_t	Option;
static	struct passwd	*pw;
static	void		list_cmd(void),
			delete_cmd(void),
			edit_cmd(void),
			poke_daemon(void),
			check_error(const char *),
			parse_args(int c, char *v[]),
			skip_header(int *, FILE *),
			usage(char *);
static	int		replace_cmd(void);


static void
usage(char *msg)
{
	fprintf(stderr, "%s: usage error: %s\n", ProgramName, msg);
	fprintf(stderr, "usage:\t%s [-u user] file\n", ProgramName);
	fprintf(stderr, "\t%s [-u user] [ -e | -l | -r ]\n", ProgramName);
	fprintf(stderr, "\t\t(default operation is replace, per 1003.2)\n");
	fprintf(stderr, "\t-e\t(edit user's crontab)\n");
	fprintf(stderr, "\t-l\t(list user's crontab)\n");
	fprintf(stderr, "\t-r\t(delete user's crontab)\n");
	exit(ERROR_EXIT);
}


int
main(int argc, char **argv)
{
	int	exitstatus;

	Pid = getpid();
	ProgramName = argv[0];

#if defined(POSIX)
	setlocale(LC_ALL, "");
#endif

#if defined(BSD)
	setlinebuf(stderr);
#endif
	parse_args(argc, argv);		/* sets many globals, opens a file */
	set_cron_uid();
	set_cron_cwd();
	if (!allowed(User)) {
		fprintf(stderr,
			"You (%s) are not allowed to use this program (%s)\n",
			User, ProgramName);
		fprintf(stderr, "See crontab(1) for more information\n");
		log_it(RealUser, Pid, "AUTH", "crontab command not allowed");
		exit(ERROR_EXIT);
	}
	exitstatus = OK_EXIT;
	switch (Option) {
	case opt_list:		list_cmd();
				break;
	case opt_delete:	delete_cmd();
				break;
	case opt_edit:		edit_cmd();
				break;
	case opt_replace:	if (replace_cmd() < 0)
					exitstatus = ERROR_EXIT;
				break;
	case opt_unknown:
				usage("unrecognized option");
				break;
	}
	exit(0);
	/*NOTREACHED*/
}
	

static void
parse_args(int argc, char **argv)
{
	int		argch;

	if (!(pw = getpwuid(getuid()))) {
		fprintf(stderr, "%s: your UID isn't in the passwd file.\n",
			ProgramName);
		fprintf(stderr, "bailing out.\n");
		exit(ERROR_EXIT);
	}
	strlcpy(User, pw->pw_name, sizeof(User));
	strlcpy(RealUser, User, sizeof(RealUser));
	Filename[0] = '\0';
	Option = opt_unknown;
	while (-1 != (argch = getopt(argc, argv, "u:lerx:"))) {
		switch (argch) {
		case 'x':
			if (!set_debug_flags(optarg))
				usage("bad debug option");
			break;
		case 'u':
			if (getuid() != ROOT_UID)
			{
				fprintf(stderr,
					"must be privileged to use -u\n");
				exit(ERROR_EXIT);
			}
			if (!(pw = getpwnam(optarg)))
			{
				fprintf(stderr, "%s:  user `%s' unknown\n",
					ProgramName, optarg);
				exit(ERROR_EXIT);
			}
			(void) strlcpy(User, optarg, sizeof(User));
			break;
		case 'l':
			if (Option != opt_unknown)
				usage("only one operation permitted");
			Option = opt_list;
			break;
		case 'r':
			if (Option != opt_unknown)
				usage("only one operation permitted");
			Option = opt_delete;
			break;
		case 'e':
			if (Option != opt_unknown)
				usage("only one operation permitted");
			Option = opt_edit;
			break;
		default:
			usage("unrecognized option");
		}
	}

	endpwent();

	if (Option != opt_unknown) {
		if (argv[optind] != NULL) {
			usage("no arguments permitted after this option");
		}
	} else {
		if (argv[optind] != NULL) {
			Option = opt_replace;
			(void) strlcpy(Filename, argv[optind],
			    sizeof(Filename));
		} else {
			usage("file name must be specified for replace");
		}
	}

	if (Option == opt_replace) {
		/* we have to open the file here because we're going to
		 * chdir(2) into /var/cron before we get around to
		 * reading the file.
		 */
		if (!strcmp(Filename, "-")) {
			NewCrontab = stdin;
		} else {
			/* relinquish the setuid status of the binary during
			 * the open, lest nonroot users read files they should
			 * not be able to read.  we can't use access() here
			 * since there's a race condition.  thanks go out to
			 * Arnt Gulbrandsen <agulbra@pvv.unit.no> for spotting
			 * the race.
			 */

			if (swap_uids() < OK) {
				perror("swapping uids");
				exit(ERROR_EXIT);
			}
			if (!(NewCrontab = fopen(Filename, "r"))) {
				perror(Filename);
				exit(ERROR_EXIT);
			}
			if (swap_uids() < OK) {
				perror("swapping uids back");
				exit(ERROR_EXIT);
			}
		}
	}

	Debug(DMISC, ("user=%s, file=%s, option=%s\n",
		      User, Filename, Options[(int)Option]))
}

static void
skip_header(int *pch, FILE *f)
{
	int ch;
	int x;
	
	/* ignore the top few comments since we probably put them there.
	 */
	for (x = 0;  x < NHEADER_LINES;  x++) {
		ch = get_char(f);
		if (EOF == ch)
			break;
		if ('#' != ch)
			break;
		while (EOF != (ch = get_char(f)))
			if (ch == '\n')
				break;
		if (EOF == ch)
			break;
	}
	if (ch == '\n')
		ch = get_char(f);

	*pch = ch;
}


static void
list_cmd(void) {
	char	n[MAX_FNAME];
	FILE	*f;
	int	ch;

	log_it(RealUser, Pid, "LIST", User);
	(void) snprintf(n, sizeof(n), CRON_TAB(User));
	if (!(f = fopen(n, "r"))) {
		if (errno == ENOENT)
			fprintf(stderr, "no crontab for %s\n", User);
		else
			perror(n);
		exit(ERROR_EXIT);
	}

	/* file is open. copy to stdout, close.
	 */
	Set_LineNum(1)
	skip_header(&ch, f);
	for (; EOF != ch;  ch = get_char(f))
		putchar(ch);
	fclose(f);
}


static void
delete_cmd(void) {
	char	n[MAX_FNAME];

	log_it(RealUser, Pid, "DELETE", User);
	(void) snprintf(n, sizeof(n), CRON_TAB(User));
	if (unlink(n)) {
		if (errno == ENOENT)
			fprintf(stderr, "no crontab for %s\n", User);
		else
			perror(n);
		exit(ERROR_EXIT);
	}
	poke_daemon();
}


static void
check_error(const char *msg)
{
	CheckErrorCount++;
	fprintf(stderr, "\"%s\":%d: %s\n", Filename, LineNumber-1, msg);
}

static void
edit_cmd(void) {
	char		n[MAX_FNAME], q[MAX_TEMPSTR];
	const char	*editor;
	FILE		*f;
	int		ch, t;
	struct stat	statbuf;
	time_t		mtime;
	long		mtimensec;
	WAIT_T		waiter;
	PID_T		pid, xpid;
	sig_t		oint, oabrt;
	char		*edit;

	log_it(RealUser, Pid, "BEGIN EDIT", User);
	(void) snprintf(n, sizeof(n), CRON_TAB(User));
	if (!(f = fopen(n, "r"))) {
		if (errno != ENOENT) {
			perror(n);
			exit(ERROR_EXIT);
		}
		fprintf(stderr, "no crontab for %s - using an empty one\n",
			User);
		if (!(f = fopen("/dev/null", "r"))) {
			perror("/dev/null");
			exit(ERROR_EXIT);
		}
	}

	(void) snprintf(Filename, sizeof(Filename), "/tmp/crontab.%d", Pid);
	if (-1 == (t = open(Filename, O_CREAT|O_EXCL|O_RDWR, 0600))) {
		perror(Filename);
		goto fatal;
	}
#ifdef HAS_FCHOWN
	if (fchown(t, getuid(), getgid()) < 0) {
#else
	if (chown(Filename, getuid(), getgid()) < 0) {
#endif
		perror("fchown");
		goto fatal;
	}
	if (fcntl(t, F_SETFD, FD_CLOEXEC) == -1) {
		perror("fcntl");
		goto fatal;
	}
	if (!(NewCrontab = fdopen(t, "r+"))) {
		perror("fdopen");
		goto fatal;
	}

	Set_LineNum(1)
        skip_header(&ch, f);
	  
	/* copy the rest of the crontab (if any) to the temp file.
	 */
	for (; EOF != ch; ch = get_char(f))
		putc(ch, NewCrontab);
	fclose(f);
	if (fflush(NewCrontab) < OK) {
		perror(Filename);
		exit(ERROR_EXIT);
	}
 again:
	rewind(NewCrontab);
	if (ferror(NewCrontab)) {
		fprintf(stderr, "%s: error while writing new crontab to %s\n",
			ProgramName, Filename);
 fatal:		unlink(Filename);
		exit(ERROR_EXIT);
	}
	if (fstat(t, &statbuf) < 0) {
		perror("fstat");
		goto fatal;
	}
	mtime = statbuf.st_mtime;
	mtimensec = statbuf.st_mtimensec;

	if ((!(editor = getenv("VISUAL")))
	 && (!(editor = getenv("EDITOR")))
	    ) {
		editor = EDITOR;
	}

	/* we still have the file open.  editors will generally rewrite the
	 * original file rather than renaming/unlinking it and starting a
	 * new one; even backup files are supposed to be made by copying
	 * rather than by renaming.  if some editor does not support this,
	 * then don't use it.  the security problems are more severe if we
	 * close and reopen the file around the edit.
	 */
	oint = signal(SIGINT, SIG_IGN);
	oabrt = signal(SIGABRT, SIG_IGN);

	switch (pid = fork()) {
	case -1:
		perror("fork");
		goto fatal;
	case 0:
		/* child */
		if (setuid(getuid()) < 0) {
			perror("setuid(getuid())");
			exit(ERROR_EXIT);
		}
		if (chdir("/tmp") < 0) {
			perror("chdir(/tmp)");
			exit(ERROR_EXIT);
		}
		asprintf(&edit, "%s %s", editor, Filename);
		if (system(edit) == -1) {
			perror(editor);
			exit(ERROR_EXIT);
		} else
			exit(OK_EXIT);
		/*NOTREACHED*/
	default:
		/* parent */
		break;
	}
	/* parent */
	xpid = wait(&waiter);
	if (xpid != pid) {
		fprintf(stderr, "%s: wrong PID (%d != %d) from \"%s\"\n",
			ProgramName, xpid, pid, editor);
		goto fatal;
	}
	(void)signal(SIGINT, oint);
	(void)signal(SIGABRT, oabrt);

	if (WIFEXITED(waiter) && WEXITSTATUS(waiter)) {
		fprintf(stderr, "%s: \"%s\" exited with status %d\n",
			ProgramName, editor, WEXITSTATUS(waiter));
		goto fatal;
	}
	if (WIFSIGNALED(waiter)) {
		fprintf(stderr,
			"%s: \"%s\" killed; signal %d (%score dumped)\n",
			ProgramName, editor, WTERMSIG(waiter),
			WCOREDUMP(waiter) ?"" :"no ");
		goto fatal;
	}
	if (fstat(t, &statbuf) < 0) {
		perror("fstat");
		goto fatal;
	}
	if (mtime == statbuf.st_mtime && mtimensec == statbuf.st_mtimensec) {
		fprintf(stderr, "%s: no changes made to crontab\n",
			ProgramName);
		goto remove;
	}
	fprintf(stderr, "%s: installing new crontab\n", ProgramName);
	switch (replace_cmd()) {
	case 0:
		break;
	case -1:
		for (;;) {
			fpurge(stdin);
			printf("Do you want to retry the same edit? ");
			fflush(stdout);
			q[0] = '\0';
			(void) fgets(q, sizeof q, stdin);
			switch (tolower((unsigned char)q[0])) {
			case 'y':
				goto again;
			case 'n':
				goto abandon;
			default:
				fprintf(stderr, "Enter Y or N\n");
			}
		}
		/*NOTREACHED*/
	case -2:
	abandon:
		fprintf(stderr, "%s: edits left in %s\n",
			ProgramName, Filename);
		goto done;
	default:
		fprintf(stderr, "%s: panic: bad switch() in replace_cmd()\n",
		    ProgramName);
		goto fatal;
	}
 remove:
	unlink(Filename);
 done:
	log_it(RealUser, Pid, "END EDIT", User);
}
	

/* returns	0	on success
 *		-1	on syntax error
 *		-2	on install error
 */
static int
replace_cmd(void) {
	char	n[MAX_FNAME], n2[MAX_FNAME], envstr[MAX_ENVSTR], tn[MAX_FNAME];
	FILE	*tmp, *fmaxtabsize;
	int	ch, eof, lastch;
	entry	*e;
	time_t	now = time(NULL);
	char	**envp = env_init();
	size_t	maxtabsize;
	struct	stat statbuf;

	(void) snprintf(n, sizeof(n), "tmp.%d", Pid);
	(void) snprintf(tn, sizeof(tn), CRON_TAB(n));
	if (!(tmp = fopen(tn, "w+"))) {
		perror(tn);
		return (-2);
	}

	/* Make sure that the crontab is not an unreasonable size.
	 *
	 * XXX This is subject to a race condition--the user could
	 * add stuff to the file after we've checked the size but
	 * before we slurp it in and write it out. We can't just move
	 * the test to test the temp file we later create, because by
	 * that time we've already filled up the crontab disk. Probably
	 * the right thing to do is to do a bytecount in the copy loop
	 * rather than stating the file we're about to read.
	 */
	(void) snprintf(n2, sizeof(n), "%s/%s", CRONDIR, MAXTABSIZE_FILE);
	if ((fmaxtabsize = fopen(n2, "r")))  {
	    if (fgets(n2, sizeof(n2), fmaxtabsize) == NULL)  {
		maxtabsize = 0;
	    } else {
		maxtabsize = atoi(n2);
	    }
	    fclose(fmaxtabsize);
	} else {
	    maxtabsize = MAXTABSIZE_DEFAULT;
	}

	if (fstat(fileno(NewCrontab), &statbuf))  {
	    fprintf(stderr, "%s: error stat'ing crontab input: %s\n",
		ProgramName, strerror(errno));
	    fclose(tmp);  unlink(tn);
	    return(-2);
	}
	if (statbuf.st_size > maxtabsize)  {
	    fprintf(stderr,
		"%s: %ld bytes is larger than the maximum size of %ld bytes\n",
		ProgramName, (long) statbuf.st_size, (long) maxtabsize);
	    fclose(tmp);  unlink(tn);
	    return(-1);
	}

	/* write a signature at the top of the file.
	 *
	 * VERY IMPORTANT: make sure NHEADER_LINES agrees with this code.
	 */
	fprintf(tmp, "# DO NOT EDIT THIS FILE - edit the master and reinstall.\n");
	fprintf(tmp, "# (%s installed on %-24.24s)\n", Filename, ctime(&now));
	fprintf(tmp, "# (Cron version -- %s)\n",
	    "$NetBSD: crontab.c,v 1.27 2006/04/25 18:02:02 christos Exp $");

	/* copy the crontab to the tmp
	 */
	rewind(NewCrontab);
	Set_LineNum(1)
	lastch = EOF;
	while (EOF != (ch = get_char(NewCrontab))) {
		putc(ch, tmp);
		lastch = ch;
	}
	if (lastch != EOF && lastch != '\n') {
		fprintf(stderr, "%s: missing trailing newline in %s\n",
			ProgramName, Filename);
		fclose(tmp);  unlink(tn);
		return(-1);
	}

	if (ferror(NewCrontab)) {
		fprintf(stderr, "%s: error while reading %s: %s\n",
			ProgramName, Filename, strerror(errno));
		fclose(tmp);  unlink(tn);
		return (-2);
	}

	ftruncate(fileno(tmp), ftell(tmp)); /* XXX this should be a NOOP - is */
	fflush(tmp);

	if (ferror(tmp)) {
		fprintf(stderr, "%s: error while writing new crontab to %s\n",
			ProgramName, tn);
		fclose(tmp);  unlink(tn);
		return (-2);
	}
	rewind(tmp);

	/* check the syntax of the file being installed.
	 */

	/* BUG: was reporting errors after the EOF if there were any errors
	 * in the file proper -- kludged it by stopping after first error.
	 *		vix 31mar87
	 */
	Set_LineNum(1 - NHEADER_LINES)
	CheckErrorCount = 0;  eof = FALSE;
	while (!CheckErrorCount && !eof) {
		switch (load_env(envstr, tmp)) {
		case ERR:
			eof = TRUE;
			break;
		case FALSE:
			e = load_entry(tmp, check_error, pw, envp);
			if (e)
				free(e);
			break;
		case TRUE:
			break;
		}
	}

	if (CheckErrorCount != 0) {
		fprintf(stderr, "errors in crontab file, can't install.\n");
		fclose(tmp);  unlink(tn);
		return (-1);
	}

#ifdef HAS_FCHOWN
	if (fchown(fileno(tmp), ROOT_UID, -1) < OK)
#else
	if (chown(tn, ROOT_UID, -1) < OK)
#endif
	{
		perror("chown");
		fclose(tmp);  unlink(tn);
		return (-2);
	}

#ifdef HAS_FCHMOD
	if (fchmod(fileno(tmp), 0600) < OK)
#else
	if (chmod(tn, 0600) < OK)
#endif
	{
		perror("chown");
		fclose(tmp);  unlink(tn);
		return (-2);
	}

	if (fclose(tmp) == EOF) {
		perror("fclose");
		unlink(tn);
		return (-2);
	}

	(void) snprintf(n, sizeof(n), CRON_TAB(User));
	if (rename(tn, n)) {
		fprintf(stderr, "%s: error renaming %s to %s\n",
			ProgramName, tn, n);
		perror("rename");
		unlink(tn);
		return (-2);
	}
	log_it(RealUser, Pid, "REPLACE", User);

	poke_daemon();

	return (0);
}


static void
poke_daemon(void) {
#ifdef USE_UTIMES
	struct timeval tvs[2];
	struct timezone tz;

	(void) gettimeofday(&tvs[0], &tz);
	tvs[1] = tvs[0];
	if (utimes(SPOOL_DIR, tvs) < OK) {
		fprintf(stderr, "crontab: can't update mtime on spooldir\n");
		perror(SPOOL_DIR);
		return;
	}
#else
	if (utime(SPOOL_DIR, NULL) < OK) {
		fprintf(stderr, "crontab: can't update mtime on spooldir\n");
		perror(SPOOL_DIR);
		return;
	}
#endif /*USE_UTIMES*/
}