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/* $OpenBSD: pfutils.c,v 1.22 2021/07/12 15:09:20 beck Exp $ */
/*
* Copyright (c) 2006 Chris Kuethe <ckuethe@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.
*/
#include <sys/types.h>
#include <sys/ioctl.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <net/if.h>
#include <net/pfvar.h>
#include <errno.h>
#include <fcntl.h>
#include <paths.h>
#include <poll.h>
#include <pwd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include "dhcp.h"
#include "tree.h"
#include "dhcpd.h"
#include "log.h"
extern struct passwd *pw;
extern int pfpipe[2];
extern int gotpipe;
extern char *abandoned_tab;
extern char *changedmac_tab;
extern char *leased_tab;
__dead void
pftable_handler()
{
struct pf_cmd cmd;
struct pollfd pfd[1];
int l, r, fd, nfds;
if ((fd = open(_PATH_DEV_PF, O_RDWR|O_NOFOLLOW, 0660)) == -1)
fatal("can't open pf device");
if (setgroups(1, &pw->pw_gid) ||
setresgid(pw->pw_gid, pw->pw_gid, pw->pw_gid) ||
setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid))
fatal("can't drop privileges");
/* no filesystem visibility */
if (unveil("/", "") == -1)
fatal("unveil /");
if (unveil(NULL, NULL) == -1)
fatal("unveil");
setproctitle("pf table handler");
l = sizeof(struct pf_cmd);
for (;;) {
pfd[0].fd = pfpipe[0];
pfd[0].events = POLLIN;
if ((nfds = poll(pfd, 1, -1)) == -1)
if (errno != EINTR)
log_warn("poll");
if (nfds > 0 && (pfd[0].revents & POLLHUP))
fatalx("pf pipe closed");
if (nfds > 0 && (pfd[0].revents & POLLIN)) {
memset(&cmd, 0, l);
r = atomicio(read, pfpipe[0], &cmd, l);
if (r != l)
fatalx("pf pipe error");
switch (cmd.type) {
case 'A':
/*
* When we abandon an address, we add it to
* the table of abandoned addresses, and remove
* it from the table of active leases.
*/
pf_change_table(fd, 1, cmd.ip, abandoned_tab);
pf_change_table(fd, 0, cmd.ip, leased_tab);
pf_kill_state(fd, cmd.ip);
break;
case 'C':
/*
* When the hardware address for an IP changes,
* remove it from the table of abandoned
* addresses, and from the table of overloaded
* addresses.
*/
pf_change_table(fd, 0, cmd.ip, abandoned_tab);
pf_change_table(fd, 0, cmd.ip, changedmac_tab);
break;
case 'L':
/*
* When a lease is granted or renewed, remove
* it from the table of abandoned addresses,
* and ensure it is in the table of active
* leases.
*/
pf_change_table(fd, 0, cmd.ip, abandoned_tab);
pf_change_table(fd, 1, cmd.ip, leased_tab);
break;
case 'R':
/*
* When we release or expire a lease, remove
* it from the table of active leases. As long
* as dhcpd doesn't abandon the address, no
* further action is required.
*/
pf_change_table(fd, 0, cmd.ip, leased_tab);
break;
default:
break;
}
}
}
/* not reached */
exit(1);
}
/* inspired by ("stolen") from usr.sbin/authpf/authpf.c */
void
pf_change_table(int fd, int op, struct in_addr ip, char *table)
{
struct pfioc_table io;
struct pfr_addr addr;
if (table == NULL)
return;
memset(&io, 0, sizeof(io));
strlcpy(io.pfrio_table.pfrt_name, table,
sizeof(io.pfrio_table.pfrt_name));
io.pfrio_buffer = &addr;
io.pfrio_esize = sizeof(addr);
io.pfrio_size = 1;
memset(&addr, 0, sizeof(addr));
memcpy(&addr.pfra_ip4addr, &ip, 4);
addr.pfra_af = AF_INET;
addr.pfra_net = 32;
if (ioctl(fd, op ? DIOCRADDADDRS : DIOCRDELADDRS, &io) == -1 &&
errno != ESRCH) {
log_warn( "DIOCR%sADDRS on table %s", op ? "ADD" : "DEL",
table);
}
}
void
pf_kill_state(int fd, struct in_addr ip)
{
struct pfioc_state_kill psk;
struct pf_addr target;
memset(&psk, 0, sizeof(psk));
memset(&target, 0, sizeof(target));
memcpy(&target.v4, &ip.s_addr, 4);
psk.psk_af = AF_INET;
/* Kill all states from target */
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(fd, DIOCKILLSTATES, &psk) == -1) {
log_warn("DIOCKILLSTATES failed");
}
/* Kill all states to target */
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(fd, DIOCKILLSTATES, &psk) == -1) {
log_warn("DIOCKILLSTATES failed");
}
}
/* inspired by ("stolen") from usr.bin/ssh/atomicio.c */
size_t
atomicio(ssize_t (*f) (int, void *, size_t), int fd, void *_s, size_t n)
{
char *s = _s;
size_t pos = 0;
ssize_t res;
while (n > pos) {
res = (f) (fd, s + pos, n - pos);
switch (res) {
case -1:
if (errno == EINTR || errno == EAGAIN)
continue;
return 0;
case 0:
errno = EPIPE;
return pos;
default:
pos += (size_t)res;
}
}
return (pos);
}
/*
* This function sends commands to the pf table handler. It will safely and
* silently return if the handler is unconfigured, therefore it can be called
* on all interesting lease events, whether or not the user actually wants to
* use the pf table feature.
*/
void
pfmsg(char c, struct lease *lp)
{
struct pf_cmd cmd;
if (gotpipe == 0)
return;
cmd.type = c;
memcpy(&cmd.ip.s_addr, lp->ip_addr.iabuf, 4);
switch (c) {
case 'A': /* address is being abandoned */
/* FALLTHROUGH */
case 'C': /* IP moved to different ethernet address */
/* FALLTHROUGH */
case 'L': /* Address is being leased (unabandoned) */
/* FALLTHROUGH */
case 'R': /* Address is being released or lease has expired */
(void)atomicio(vwrite, pfpipe[1], &cmd,
sizeof(struct pf_cmd));
break;
default: /* silently ignore unknown commands */
break;
}
}
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