shadow/libmisc/failure.c

/*
 * Copyright 1989 - 1994, Julianne Frances Haugh
 * All rights reserved.
 *
 * 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. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of Julianne F. Haugh nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY JULIE HAUGH AND CONTRIBUTORS ``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 JULIE HAUGH OR CONTRIBUTORS 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, WHETHER 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.
 */

#include <config.h>

#include "rcsid.h"
RCSID ("$Id: failure.c,v 1.15 2005/06/20 10:02:02 kloczek Exp $")
#include <fcntl.h>
#include <stdio.h>
#include "defines.h"
#include "faillog.h"
#include "getdef.h"
#include "failure.h"
#define	YEAR	(365L*DAY)
/*
 * failure - make failure entry
 *
 *	failure() creates a new (struct faillog) entry or updates an
 *	existing one with the current failed login information.
 */
void failure (uid_t uid, const char *tty, struct faillog *fl)
{
	int fd;

	/*
	 * Don't do anything if failure logging isn't set up.
	 */

	if ((fd = open (FAILLOG_FILE, O_RDWR)) < 0)
		return;

	/*
	 * The file is indexed by UID value meaning that shared UID's
	 * share failure log records.  That's OK since they really
	 * share just about everything else ...
	 */

	lseek (fd, (off_t) (sizeof *fl) * uid, SEEK_SET);
	if (read (fd, (char *) fl, sizeof *fl) != sizeof *fl)
		memzero (fl, sizeof *fl);

	/*
	 * Update the record.  We increment the failure count to log the
	 * latest failure.  The only concern here is overflow, and we'll
	 * check for that.  The line name and time of day are both
	 * updated as well.
	 */

	if (fl->fail_cnt + 1 > 0)
		fl->fail_cnt++;

	strncpy (fl->fail_line, tty, sizeof fl->fail_line);
	time (&fl->fail_time);

	/*
	 * Seek back to the correct position in the file and write the
	 * record out.  Ideally we should lock the file in case the same
	 * account is being logged simultaneously.  But the risk doesn't
	 * seem that great.
	 */

	lseek (fd, (off_t) (sizeof *fl) * uid, SEEK_SET);
	write (fd, (char *) fl, sizeof *fl);
	close (fd);
}

static int too_many_failures (const struct faillog *fl)
{
	time_t now;

	if (fl->fail_max == 0 || fl->fail_cnt < fl->fail_max)
		return 0;

	if (fl->fail_locktime == 0)
		return 1;	/* locked until reset manually */

	time (&now);
	if (fl->fail_time + fl->fail_locktime < now)
		return 0;	/* enough time since last failure */

	return 1;
}

/*
 * failcheck - check for failures > allowable
 *
 *	failcheck() is called AFTER the password has been validated.  If the
 *	account has been "attacked" with too many login failures, failcheck()
 *	returns FALSE to indicate that the login should be denied even though
 *	the password is valid.
 */

int failcheck (uid_t uid, struct faillog *fl, int failed)
{
	int fd;
	struct faillog fail;

	/*
	 * Suppress the check if the log file isn't there.
	 */

	if ((fd = open (FAILLOG_FILE, O_RDWR)) < 0)
		return 1;

	/*
	 * Get the record from the file and determine if the user has
	 * exceeded the failure limit.  If "max" is zero, any number
	 * of failures are permitted.  Only when "max" is non-zero and
	 * "cnt" is greater than or equal to "max" is the account
	 * considered to be locked.
	 *
	 * If read fails, there is no record for this user yet (the
	 * file is initially zero length and extended by writes), so
	 * no need to reset the count.
	 */

	lseek (fd, (off_t) (sizeof *fl) * uid, SEEK_SET);
	if (read (fd, (char *) fl, sizeof *fl) != sizeof *fl) {
		close (fd);
		return 1;
	}

	if (too_many_failures (fl)) {
		close (fd);
		return 0;
	}

	/*
	 * The record is updated if this is not a failure.  The count will
	 * be reset to zero, but the rest of the information will be left
	 * in the record in case someone wants to see where the failed
	 * login originated.
	 */

	if (!failed) {
		fail = *fl;
		fail.fail_cnt = 0;

		lseek (fd, (off_t) sizeof fail * uid, SEEK_SET);
		write (fd, (char *) &fail, sizeof fail);
	}
	close (fd);
	return 1;
}

/*
 * failprint - print line of failure information
 *
 *	failprint takes a (struct faillog) entry and formats it into a
 *	message which is displayed at login time.
 */

void failprint (const struct faillog *fail)
{
	struct tm *tp;

#if HAVE_STRFTIME
	char lasttimeb[256];
	char *lasttime = lasttimeb;
	const char *fmt;
#else
	char *lasttime;
#endif
	time_t NOW;

	if (fail->fail_cnt == 0)
		return;

	tp = localtime (&(fail->fail_time));
	time (&NOW);

#if HAVE_STRFTIME
	/*
	 * Only print as much date and time info as it needed to
	 * know when the failure was.
	 */

	if (NOW - fail->fail_time >= YEAR)
		fmt = "%Y";
	else if (NOW - fail->fail_time >= DAY)
		fmt = "%A %T";
	else
		fmt = "%T";
	strftime (lasttimeb, sizeof lasttimeb, fmt, tp);
#else

	/*
	 * Do the same thing, but don't use strftime since it
	 * probably doesn't exist on this system
	 */

	lasttime = asctime (tp);
	lasttime[24] = '\0';

	if (NOW - fail->fail_time < YEAR)
		lasttime[19] = '\0';
	if (NOW - fail->fail_time < DAY)
		lasttime = lasttime + 11;

	if (*lasttime == ' ')
		lasttime++;
#endif
	printf (ngettext ("%d failure since last login.\n"
			  "Last was %s on %s.\n",
			  "%d failures since last login.\n"
			  "Last was %s on %s.\n",
			  fail->fail_cnt),
		fail->fail_cnt, lasttime, fail->fail_line);
}

/*
 * failtmp - update the cummulative failure log
 *
 *	failtmp updates the (struct utmp) formatted failure log which
 *	maintains a record of all login failures.
 */

void failtmp (
#ifdef HAVE_UTMPX_H
		     const struct utmpx *failent
#else
		     const struct utmp *failent
#endif
    )
{
	char *ftmp;
	int fd;

	/*
	 * Get the name of the failure file.  If no file has been defined
	 * in login.defs, don't do this.
	 */

	if (!(ftmp = getdef_str ("FTMP_FILE")))
		return;

	/*
	 * Open the file for append.  It must already exist for this
	 * feature to be used.
	 */

	if ((fd = open (ftmp, O_WRONLY | O_APPEND)) == -1)
		return;

	/*
	 * Output the new failure record and close the log file.
	 */

	write (fd, (const char *) failent, sizeof *failent);
	close (fd);
}