xref: /src/dist/pf/usr.sbin/authpf/authpf.c

/*	$NetBSD: authpf.c,v 1.4 2005/07/01 12:43:50 peter Exp $	*/
/*	$OpenBSD: authpf.c,v 1.89 2005/02/10 04:24:15 joel Exp $	*/

/*
 * Copyright (C) 1998 - 2002 Bob Beck (beck (at) openbsd.org).
 *
 * 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 THE AUTHOR 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 <sys/types.h>
#include <sys/file.h>
#include <sys/ioctl.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/time.h>
#include <sys/wait.h>

#include <net/if.h>
#include <netinet/in.h>
#include <net/pfvar.h>
#include <arpa/inet.h>

#include <err.h>
#include <errno.h>
#include <login_cap.h>
#include <pwd.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <syslog.h>
#include <unistd.h>

#include "pathnames.h"

extern int	symset(const char *, const char *, int);

static int	read_config(FILE *);
static void	print_message(char *);
static int	allowed_luser(char *);
static int	check_luser(char *, char *);
static int	remove_stale_rulesets(void);
static int	change_filter(int, const char *, const char *);
static int	change_table(int, const char *, const char *);
static void	authpf_kill_states(void);

int	dev;			/* pf device */
char	anchorname[PF_ANCHOR_NAME_SIZE] = "authpf";
char	rulesetname[MAXPATHLEN - PF_ANCHOR_NAME_SIZE - 2];
char	tablename[PF_TABLE_NAME_SIZE] = "authpf_users";

FILE	*pidfp;
char	*infile;		/* file name printed by yyerror() in parse.y */
char	 luser[MAXLOGNAME];	/* username */
char	 ipsrc[256];		/* ip as a string */
char	 pidfile[MAXPATHLEN];	/* we save pid in this file. */

struct timeval	Tstart, Tend;	/* start and end times of session */

volatile sig_atomic_t	want_death;
static void		need_death(int signo);
static __dead void	do_death(int);

/*
 * User shell for authenticating gateways. Sole purpose is to allow
 * a user to ssh to a gateway, and have the gateway modify packet
 * filters to allow access, then remove access when the user finishes
 * up. Meant to be used only from ssh(1) connections.
 */
int
main(int argc, char *argv[])
{
	int		 lockcnt = 0, n, pidfd;
	FILE		*config;
	struct in6_addr	 ina;
	struct passwd	*pw;
	char		*cp;
	uid_t		 uid;
	char		*shell;
	login_cap_t	*lc;

	config = fopen(PATH_CONFFILE, "r");

	if ((cp = getenv("SSH_TTY")) == NULL) {
		syslog(LOG_ERR, "non-interactive session connection for authpf");
		exit(1);
	}

	if ((cp = getenv("SSH_CLIENT")) == NULL) {
		syslog(LOG_ERR, "cannot determine connection source");
		exit(1);
	}

	if (strlcpy(ipsrc, cp, sizeof(ipsrc)) >= sizeof(ipsrc)) {
		syslog(LOG_ERR, "SSH_CLIENT variable too long");
		exit(1);
	}
	cp = strchr(ipsrc, ' ');
	if (!cp) {
		syslog(LOG_ERR, "corrupt SSH_CLIENT variable %s", ipsrc);
		exit(1);
	}
	*cp = '\0';
	if (inet_pton(AF_INET, ipsrc, &ina) != 1 &&
	    inet_pton(AF_INET6, ipsrc, &ina) != 1) {
		syslog(LOG_ERR,
		    "cannot determine IP from SSH_CLIENT %s", ipsrc);
		exit(1);
	}
	/* open the pf device */
	dev = open(PATH_DEVFILE, O_RDWR);
	if (dev == -1) {
		syslog(LOG_ERR, "cannot open packet filter device (%m)");
		goto die;
	}

	uid = getuid();
	pw = getpwuid(uid);
	endpwent();
	if (pw == NULL) {
		syslog(LOG_ERR, "cannot find user for uid %u", uid);
		goto die;
	}

	if ((lc = login_getclass(pw->pw_class)) != NULL)
		shell = login_getcapstr(lc, "shell", pw->pw_shell,
		    pw->pw_shell);
	else
		shell = pw->pw_shell;

	login_close(lc);

	if (strcmp(shell, PATH_AUTHPF_SHELL)) {
		syslog(LOG_ERR, "wrong shell for user %s, uid %u",
		    pw->pw_name, pw->pw_uid);
		if (shell != pw->pw_shell)
			free(shell);
		goto die;
	}

	if (shell != pw->pw_shell)
		free(shell);

	/*
	 * Paranoia, but this data _does_ come from outside authpf, and
	 * truncation would be bad.
	 */
	if (strlcpy(luser, pw->pw_name, sizeof(luser)) >= sizeof(luser)) {
		syslog(LOG_ERR, "username too long: %s", pw->pw_name);
		goto die;
	}

	if ((n = snprintf(rulesetname, sizeof(rulesetname), "%s(%ld)",
	    luser, (long)getpid())) < 0 || (u_int)n >= sizeof(rulesetname)) {
		syslog(LOG_INFO, "%s(%ld) too large, ruleset name will be %ld",
		    luser, (long)getpid(), (long)getpid());
		if ((n = snprintf(rulesetname, sizeof(rulesetname), "%ld",
		    (long)getpid())) < 0 || (u_int)n >= sizeof(rulesetname)) {
			syslog(LOG_ERR, "pid too large for ruleset name");
			goto die;
		}
	}


	/* Make our entry in /var/authpf as /var/authpf/ipaddr */
	n = snprintf(pidfile, sizeof(pidfile), "%s/%s", PATH_PIDFILE, ipsrc);
	if (n < 0 || (u_int)n >= sizeof(pidfile)) {
		syslog(LOG_ERR, "path to pidfile too long");
		goto die;
	}

	/*
	 * If someone else is already using this ip, then this person
	 * wants to switch users - so kill the old process and exit
	 * as well.
	 *
	 * Note, we could print a message and tell them to log out, but the
	 * usual case of this is that someone has left themselves logged in,
	 * with the authenticated connection iconized and someone else walks
	 * up to use and automatically logs in before using. If this just
	 * gets rid of the old one silently, the new user never knows they
	 * could have used someone else's old authentication. If we
	 * tell them to log out before switching users it is an invitation
	 * for abuse.
	 */

	do {
		int	save_errno, otherpid = -1;
		char	otherluser[MAXLOGNAME];

		if ((pidfd = open(pidfile, O_RDWR|O_CREAT, 0644)) == -1 ||
		    (pidfp = fdopen(pidfd, "r+")) == NULL) {
			if (pidfd != -1)
				close(pidfd);
			syslog(LOG_ERR, "cannot open or create %s: %s", pidfile,
			    strerror(errno));
			goto die;
		}

		if (flock(fileno(pidfp), LOCK_EX|LOCK_NB) == 0)
			break;
		save_errno = errno;

		/* Mark our pid, and username to our file. */

		rewind(pidfp);
		/* 31 == MAXLOGNAME - 1 */
		if (fscanf(pidfp, "%d\n%31s\n", &otherpid, otherluser) != 2)
			otherpid = -1;
		syslog(LOG_DEBUG, "tried to lock %s, in use by pid %d: %s",
		    pidfile, otherpid, strerror(save_errno));

		if (otherpid > 0) {
			syslog(LOG_INFO,
			    "killing prior auth (pid %d) of %s by user %s",
			    otherpid, ipsrc, otherluser);
			if (kill((pid_t) otherpid, SIGTERM) == -1) {
				syslog(LOG_INFO,
				    "could not kill process %d: (%m)",
				    otherpid);
			}
		}

		/*
		 * we try to kill the previous process and acquire the lock
		 * for 10 seconds, trying once a second. if we can't after
		 * 10 attempts we log an error and give up
		 */
		if (++lockcnt > 10) {
			syslog(LOG_ERR, "cannot kill previous authpf (pid %d)",
			    otherpid);
			goto dogdeath;
		}
		sleep(1);

		/* re-open, and try again. The previous authpf process
		 * we killed above should unlink the file and release
		 * it's lock, giving us a chance to get it now
		 */
		fclose(pidfp);
	} while (1);

	/* revoke privs */
	seteuid(getuid());
	setuid(getuid());

	openlog("authpf", LOG_PID | LOG_NDELAY, LOG_DAEMON);

	if (!check_luser(PATH_BAN_DIR, luser) || !allowed_luser(luser)) {
		syslog(LOG_INFO, "user %s prohibited", luser);
		do_death(0);
	}

	if (config == NULL || read_config(config)) {
		syslog(LOG_INFO, "bad or nonexistent %s", PATH_CONFFILE);
		do_death(0);
	}

	if (remove_stale_rulesets()) {
		syslog(LOG_INFO, "error removing stale rulesets");
		do_death(0);
	}

	/* We appear to be making headway, so actually mark our pid */
	rewind(pidfp);
	fprintf(pidfp, "%ld\n%s\n", (long)getpid(), luser);
	fflush(pidfp);
	(void) ftruncate(fileno(pidfp), ftello(pidfp));

	if (change_filter(1, luser, ipsrc) == -1) {
		printf("Unable to modify filters\r\n");
		do_death(0);
	}
	if (change_table(1, luser, ipsrc) == -1) {
		printf("Unable to modify table\r\n");
		change_filter(0, luser, ipsrc);
		do_death(0);
	}

	signal(SIGTERM, need_death);
	signal(SIGINT, need_death);
	signal(SIGALRM, need_death);
	signal(SIGPIPE, need_death);
	signal(SIGHUP, need_death);
	signal(SIGSTOP, need_death);
	signal(SIGTSTP, need_death);
	while (1) {
		printf("\r\nHello %s. ", luser);
		printf("You are authenticated from host \"%s\"\r\n", ipsrc);
		setproctitle("%s@%s", luser, ipsrc);
		print_message(PATH_MESSAGE);
		while (1) {
			sleep(10);
			if (want_death)
				do_death(1);
		}
	}

	/* NOTREACHED */
dogdeath:
	printf("\r\n\r\nSorry, this service is currently unavailable due to ");
	printf("technical difficulties\r\n\r\n");
	print_message(PATH_PROBLEM);
	printf("\r\nYour authentication process (pid %ld) was unable to run\n",
	    (long)getpid());
	sleep(180); /* them lusers read reaaaaal slow */
die:
	do_death(0);
	return (0);
}

/*
 * reads config file in PATH_CONFFILE to set optional behaviours up
 */
static int
read_config(FILE *f)
{
	char	buf[1024];
	int	i = 0;

	do {
		char	**ap;
		char	 *pair[4], *cp, *tp;
		int	  len;

		if (fgets(buf, sizeof(buf), f) == NULL) {
			fclose(f);
			return (0);
		}
		i++;
		len = strlen(buf);
		if (buf[len - 1] != '\n' && !feof(f)) {
			syslog(LOG_ERR, "line %d too long in %s", i,
			    PATH_CONFFILE);
			return (1);
		}
		buf[len - 1] = '\0';

		for (cp = buf; *cp == ' ' || *cp == '\t'; cp++)
			; /* nothing */

		if (!*cp || *cp == '#' || *cp == '\n')
			continue;

		for (ap = pair; ap < &pair[3] &&
		    (*ap = strsep(&cp, "=")) != NULL; ) {
			if (**ap != '\0')
				ap++;
		}
		if (ap != &pair[2])
			goto parse_error;

		tp = pair[1] + strlen(pair[1]);
		while ((*tp == ' ' || *tp == '\t') && tp >= pair[1])
			*tp-- = '\0';

		if (strcasecmp(pair[0], "anchor") == 0) {
			if (!pair[1][0] || strlcpy(anchorname, pair[1],
			    sizeof(anchorname)) >= sizeof(anchorname))
				goto parse_error;
		}
		if (strcasecmp(pair[0], "table") == 0) {
			if (!pair[1][0] || strlcpy(tablename, pair[1],
			    sizeof(tablename)) >= sizeof(tablename))
				goto parse_error;
		}
	} while (!feof(f) && !ferror(f));
	fclose(f);
	return (0);

parse_error:
	fclose(f);
	syslog(LOG_ERR, "parse error, line %d of %s", i, PATH_CONFFILE);
	return (1);
}


/*
 * splatter a file to stdout - max line length of 1024,
 * used for spitting message files at users to tell them
 * they've been bad or we're unavailable.
 */
static void
print_message(char *filename)
{
	char	 buf[1024];
	FILE	*f;

	if ((f = fopen(filename, "r")) == NULL)
		return; /* fail silently, we don't care if it isn't there */

	do {
		if (fgets(buf, sizeof(buf), f) == NULL) {
			fflush(stdout);
			fclose(f);
			return;
		}
	} while (fputs(buf, stdout) != EOF && !feof(f));
	fflush(stdout);
	fclose(f);
}

/*
 * allowed_luser checks to see if user "luser" is allowed to
 * use this gateway by virtue of being listed in an allowed
 * users file, namely /etc/authpf/authpf.allow .
 *
 * If /etc/authpf/authpf.allow does not exist, then we assume that
 * all users who are allowed in by sshd(8) are permitted to
 * use this gateway. If /etc/authpf/authpf.allow does exist, then a
 * user must be listed if the connection is to continue, else
 * the session terminates in the same manner as being banned.
 */
static int
allowed_luser(char *luser)
{
	char	*buf, *lbuf;
	int	 matched;
	size_t	 len;
	FILE	*f;

	if ((f = fopen(PATH_ALLOWFILE, "r")) == NULL) {
		if (errno == ENOENT) {
			/*
			 * allowfile doesn't exist, thus this gateway
			 * isn't restricted to certain users...
			 */
			return (1);
		}

		/*
		 * luser may in fact be allowed, but we can't open
		 * the file even though it's there. probably a config
		 * problem.
		 */
		syslog(LOG_ERR, "cannot open allowed users file %s (%s)",
		    PATH_ALLOWFILE, strerror(errno));
		return (0);
	} else {
		/*
		 * /etc/authpf/authpf.allow exists, thus we do a linear
		 * search to see if they are allowed.
		 * also, if username "*" exists, then this is a
		 * "public" gateway, such as it is, so let
		 * everyone use it.
		 */
		lbuf = NULL;
		while ((buf = fgetln(f, &len))) {
			if (buf[len - 1] == '\n')
				buf[len - 1] = '\0';
			else {
				if ((lbuf = (char *)malloc(len + 1)) == NULL)
					err(1, NULL);
				memcpy(lbuf, buf, len);
				lbuf[len] = '\0';
				buf = lbuf;
			}

			matched = strcmp(luser, buf) == 0 || strcmp("*", buf) == 0;

			if (lbuf != NULL) {
				free(lbuf);
				lbuf = NULL;
			}

			if (matched)
				return (1); /* matched an allowed username */
		}
		syslog(LOG_INFO, "denied access to %s: not listed in %s",
		    luser, PATH_ALLOWFILE);

		/* reuse buf */
		buf = "\n\nSorry, you are not allowed to use this facility!\n";
		fputs(buf, stdout);
	}
	fflush(stdout);
	return (0);
}

/*
 * check_luser checks to see if user "luser" has been banned
 * from using us by virtue of having an file of the same name
 * in the "luserdir" directory.
 *
 * If the user has been banned, we copy the contents of the file
 * to the user's screen. (useful for telling the user what to
 * do to get un-banned, or just to tell them they aren't
 * going to be un-banned.)
 */
static int
check_luser(char *luserdir, char *luser)
{
	FILE	*f;
	int	 n;
	char	 tmp[MAXPATHLEN];

	n = snprintf(tmp, sizeof(tmp), "%s/%s", luserdir, luser);
	if (n < 0 || (u_int)n >= sizeof(tmp)) {
		syslog(LOG_ERR, "provided banned directory line too long (%s)",
		    luserdir);
		return (0);
	}
	if ((f = fopen(tmp, "r")) == NULL) {
		if (errno == ENOENT) {
			/*
			 * file or dir doesn't exist, so therefore
			 * this luser isn't banned..  all is well
			 */
			return (1);
		} else {
			/*
			 * luser may in fact be banned, but we can't open the
			 * file even though it's there. probably a config
			 * problem.
			 */
			syslog(LOG_ERR, "cannot open banned file %s (%s)",
			    tmp, strerror(errno));
			return (0);
		}
	} else {
		/*
		 * luser is banned - spit the file at them to
		 * tell what they can do and where they can go.
		 */
		syslog(LOG_INFO, "denied access to %s: %s exists",
		    luser, tmp);

		/* reuse tmp */
		strlcpy(tmp, "\n\n-**- Sorry, you have been banned! -**-\n\n",
		    sizeof(tmp));
		while (fputs(tmp, stdout) != EOF && !feof(f)) {
			if (fgets(tmp, sizeof(tmp), f) == NULL) {
				fflush(stdout);
				return (0);
			}
		}
	}
	fflush(stdout);
	return (0);
}

/*
 * Search for rulesets left by other authpf processes (either because they
 * died ungracefully or were terminated) and remove them.
 */
static int
remove_stale_rulesets(void)
{
	struct pfioc_ruleset	 prs;
	u_int32_t		 nr, mnr;

	memset(&prs, 0, sizeof(prs));
	strlcpy(prs.path, anchorname, sizeof(prs.path));
	if (ioctl(dev, DIOCGETRULESETS, &prs)) {
		if (errno == EINVAL)
			return (0);
		else
			return (1);
	}

	mnr = prs.nr;
	nr = 0;
	while (nr < mnr) {
		char	*s, *t;
		pid_t	 pid;

		prs.nr = nr;
		if (ioctl(dev, DIOCGETRULESET, &prs))
			return (1);
		errno = 0;
		if ((t = strchr(prs.name, '(')) == NULL)
			t = prs.name;
		else
			t++;
		pid = strtoul(t, &s, 10);
		if (!prs.name[0] || errno ||
		    (*s && (t == prs.name || *s != ')')))
			return (1);
		if (kill(pid, 0) && errno != EPERM) {
			int			i;
			struct pfioc_trans_e	t_e[PF_RULESET_MAX+1];
			struct pfioc_trans	t;

			bzero(&t, sizeof(t));
			bzero(t_e, sizeof(t_e));
			t.size = PF_RULESET_MAX+1;
			t.esize = sizeof(t_e[0]);
			t.array = t_e;
			for (i = 0; i < PF_RULESET_MAX+1; ++i) {
				t_e[i].rs_num = i;
				snprintf(t_e[i].anchor, sizeof(t_e[i].anchor),
				    "%s/%s", anchorname, prs.name);
			}
			t_e[PF_RULESET_MAX].rs_num = PF_RULESET_TABLE;
			if ((ioctl(dev, DIOCXBEGIN, &t) ||
			    ioctl(dev, DIOCXCOMMIT, &t)) &&
			    errno != EINVAL)
				return (1);
			mnr--;
		} else
			nr++;
	}
	return (0);
}

/*
 * Add/remove filter entries for user "luser" from ip "ipsrc"
 */
static int
change_filter(int add, const char *luser, const char *ipsrc)
{
	char	*pargv[13] = {
		"pfctl", "-p", "/dev/pf", "-q", "-a", "anchor/ruleset",
		"-D", "user_ip=X", "-D", "user_id=X", "-f",
		"file", NULL
	};
	char	*fdpath = NULL, *userstr = NULL, *ipstr = NULL;
	char	*rsn = NULL, *fn = NULL;
	pid_t	pid;
	int	s;

	if (luser == NULL || !luser[0] || ipsrc == NULL || !ipsrc[0]) {
		syslog(LOG_ERR, "invalid luser/ipsrc");
		goto error;
	}

	if (asprintf(&rsn, "%s/%s", anchorname, rulesetname) == -1)
		goto no_mem;
	if (asprintf(&fdpath, "/dev/fd/%d", dev) == -1)
		goto no_mem;
	if (asprintf(&ipstr, "user_ip=%s", ipsrc) == -1)
		goto no_mem;
	if (asprintf(&userstr, "user_id=%s", luser) == -1)
		goto no_mem;

	if (add) {
		struct stat sb;

		if (asprintf(&fn, "%s/%s/authpf.rules", PATH_USER_DIR, luser)
		    == -1)
			goto no_mem;
		if (stat(fn, &sb) == -1) {
			free(fn);
			if ((fn = strdup(PATH_PFRULES)) == NULL)
				goto no_mem;
		}
	}
	pargv[2] = fdpath;
	pargv[5] = rsn;
	pargv[7] = userstr;
	pargv[9] = ipstr;
	if (!add)
		pargv[11] = "/dev/null";
	else
		pargv[11] = fn;

	switch (pid = fork()) {
	case -1:
		err(1, "fork failed");
	case 0:
		execvp(PATH_PFCTL, pargv);
		warn("exec of %s failed", PATH_PFCTL);
		_exit(1);
	}

	/* parent */
	waitpid(pid, &s, 0);
	if (s != 0) {
		if (WIFEXITED(s)) {
			syslog(LOG_ERR, "pfctl exited abnormally");
			goto error;
		}
	}

	if (add) {
		gettimeofday(&Tstart, NULL);
		syslog(LOG_INFO, "allowing %s, user %s", ipsrc, luser);
	} else {
		gettimeofday(&Tend, NULL);
		syslog(LOG_INFO, "removed %s, user %s - duration %ld seconds",
		    ipsrc, luser, Tend.tv_sec - Tstart.tv_sec);
	}
	return (0);
no_mem:
	syslog(LOG_ERR, "malloc failed");
error:
	free(fdpath);
	fdpath = NULL;
	free(rsn);
	rsn = NULL;
	free(userstr);
	userstr = NULL;
	free(ipstr);
	ipstr = NULL;
	free(fn);
	fn = NULL;
	infile = NULL;
	return (-1);
}

/*
 * Add/remove this IP from the "authpf_users" table.
 */
static int
change_table(int add, const char *luser, const char *ipsrc)
{
	struct pfioc_table	io;
	struct pfr_addr		addr;

	bzero(&io, sizeof(io));
	strlcpy(io.pfrio_table.pfrt_name, tablename, sizeof(io.pfrio_table));
	io.pfrio_buffer = &addr;
	io.pfrio_esize = sizeof(addr);
	io.pfrio_size = 1;

	bzero(&addr, sizeof(addr));
	if (ipsrc == NULL || !ipsrc[0])
		return (-1);
	if (inet_pton(AF_INET, ipsrc, &addr.pfra_ip4addr) == 1) {
		addr.pfra_af = AF_INET;
		addr.pfra_net = 32;
	} else if (inet_pton(AF_INET6, ipsrc, &addr.pfra_ip6addr) == 1) {
		addr.pfra_af = AF_INET6;
		addr.pfra_net = 128;
	} else {
		syslog(LOG_ERR, "invalid ipsrc");
		return (-1);
	}

	if (ioctl(dev, add ? DIOCRADDADDRS : DIOCRDELADDRS, &io) &&
	    errno != ESRCH) {
		syslog(LOG_ERR, "cannot %s %s from table %s: %s",
		    add ? "add" : "remove", ipsrc, tablename,
		    strerror(errno));
		return (-1);
	}
	return (0);
}

/*
 * This is to kill off states that would otherwise be left behind stateful
 * rules. This means we don't need to allow in more traffic than we really
 * want to, since we don't have to worry about any luser sessions lasting
 * longer than their ssh session. This function is based on
 * pfctl_kill_states from pfctl.
 */
static void
authpf_kill_states(void)
{
	struct pfioc_state_kill	psk;
	struct pf_addr target;

	memset(&psk, 0, sizeof(psk));
	memset(&target, 0, sizeof(target));

	if (inet_pton(AF_INET, ipsrc, &target.v4) == 1)
		psk.psk_af = AF_INET;
	else if (inet_pton(AF_INET6, ipsrc, &target.v6) == 1)
		psk.psk_af = AF_INET6;
	else {
		syslog(LOG_ERR, "inet_pton(%s) failed", ipsrc);
		return;
	}

	/* Kill all states from ipsrc */
	memcpy(&psk.psk_src.addr.v.a.addr, &target,
	    sizeof(psk.psk_src.addr.v.a.addr));
	memset(&psk.psk_src.addr.v.a.mask, 0xff,
	    sizeof(psk.psk_src.addr.v.a.mask));
	if (ioctl(dev, DIOCKILLSTATES, &psk))
		syslog(LOG_ERR, "DIOCKILLSTATES failed (%m)");

	/* Kill all states to ipsrc */
	memset(&psk.psk_src, 0, sizeof(psk.psk_src));
	memcpy(&psk.psk_dst.addr.v.a.addr, &target,
	    sizeof(psk.psk_dst.addr.v.a.addr));
	memset(&psk.psk_dst.addr.v.a.mask, 0xff,
	    sizeof(psk.psk_dst.addr.v.a.mask));
	if (ioctl(dev, DIOCKILLSTATES, &psk))
		syslog(LOG_ERR, "DIOCKILLSTATES failed (%m)");
}

/* signal handler that makes us go away properly */
static void
need_death(int signo)
{
	want_death = 1;
}

/*
 * function that removes our stuff when we go away.
 */
static __dead void
do_death(int active)
{
	int	ret = 0;

	if (active) {
		change_filter(0, luser, ipsrc);
		change_table(0, luser, ipsrc);
		authpf_kill_states();
		remove_stale_rulesets();
	}
	if (pidfp)
		ftruncate(fileno(pidfp), 0);
	if (pidfile[0])
		if (unlink(pidfile) == -1)
			syslog(LOG_ERR, "cannot unlink %s (%m)", pidfile);
	exit(ret);
}