3 ### Utility functions for firewall scripts
5 ### (c) 2008 Mark Wooding
8 ###----- Licensing notice ---------------------------------------------------
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18 ### GNU General Public License for more details.
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22 ### Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
25 ###--------------------------------------------------------------------------
26 ### Utility functions.
28 ## doit COMMAND ARGS...
30 ## If debugging, print the COMMAND and ARGS. If serious, execute them.
33 if [ "$FW_DEBUG" ]; then echo "* $*"; fi
34 if ! [ "$FW_NOACT" ]; then "$@"; fi
39 ## If debugging, print the MESSAGE.
42 if [ "$FW_DEBUG" ]; then echo "$*"; fi
45 ## defport NAME NUMBER
47 ## Define $port_NAME to be NUMBER.
50 eval port_$name=$number
53 ## defproto NAME NUMBER
55 ## Define $proto_NAME to be NUMBER.
58 eval proto_$name=$number
63 ## Adds WORD to the value of the shell variable VAR, if it's not there
64 ## already. Words are separated by a single space; no leading or trailing
65 ## spaces are introduced.
71 *) eval "$var=\${$var:+\$val }\$word" ;;
76 ###--------------------------------------------------------------------------
77 ### Utility chains (used by function definitions).
80 ###--------------------------------------------------------------------------
81 ### Basic chain constructions.
83 ## ip46tables ARGS ...
85 ## Do the same thing for `iptables' and `ip6tables'.
92 ## clearchain CHAIN CHAIN ...
94 ## Ensure that the named chains exist and are empty.
99 *:*) table=${chain%:*} chain=${chain#*:} ;;
102 run ip46tables -t $table -N $chain 2>/dev/null || :
106 ## makeset SET TYPE [PARAMS]
108 ## Ensure that the named ipset exists. Don't clear it.
112 if ipset -nL | grep -q "^Name: $name$"; then
115 ipset -N "$name" "$@"
119 ## errorchain CHAIN ACTION ARGS ...
121 ## Make a chain which logs a message and then invokes some other action,
122 ## typically REJECT. Log messages are prefixed by `fw: CHAIN'.
127 *:*) table=${chain%:*} chain=${chain#*:} ;;
130 clearchain $table:$chain
131 run ip46tables -t $table -A $chain -j LOG \
132 -m limit --limit 3/minute --limit-burst 10 \
133 --log-prefix "fw: $chain " --log-level notice
134 run ip46tables -t $table -A $chain -j "$@" \
135 -m limit --limit 20/second --limit-burst 100
136 run ip46tables -t $table -A $chain -j DROP
140 ###--------------------------------------------------------------------------
141 ### Basic option setting.
143 ## setopt OPTION VALUE
150 for ver in ipv4 ipv6; do
151 if [ -f /proc/sys/net/$ver/$opt ]; then
152 run sysctl -q net/$ver/$opt="$val"
157 nil) echo >&2 "$0: unknown IP option $opt"; exit 1 ;;
161 ## setdevopt OPTION VALUE [INTERFACES ...]
163 ## Set an IP interface-level sysctl.
166 opt=$1 val=$2; shift 2
171 for ver in ipv4 ipv6; do
172 cd /proc/sys/net/$ver/conf
174 [ -f $i/$opt ] || continue
175 case "$seen" in (*:$i:*) continue ;; esac
183 for ver in ipv4 ipv6; do
184 if [ -f /proc/sys/net/$ver/conf/$i/$opt ]; then
186 run sysctl -q net/ipv4/conf/$i/$opt="$val"
190 nil) echo >&2 "$0: unknown device option $opt"; exit 1 ;;
196 ###--------------------------------------------------------------------------
197 ### Packet filter construction.
201 ## Add connection tracking to CHAIN, and allow obvious stuff.
205 run ip46tables -A $chain -p tcp -m state \
206 --state ESTABLISHED,RELATED -j ACCEPT
207 run ip46tables -A $chain -p tcp ! --syn -g bad-tcp
212 ## Add standard IP filtering rules to the CHAIN.
217 ## Pass fragments through, assuming that the eventual destination will sort
218 ## things out properly. Except for TCP, that is, which should never be
219 ## fragmented. This is an extra pain for ip6tables, which doesn't provide
220 ## a pleasant way to detect non-initial fragments.
221 run iptables -A $chain -p tcp -f -g tcp-fragment
222 run iptables -A $chain -f -j ACCEPT
223 run ip6tables -A $chain -p tcp -g tcp-fragment \
224 -m ipv6header --soft --header frag
225 run ip6tables -A $chain -j accept-non-init-frag
229 ## Accept a non-initial fragment. This is only needed by IPv6, to work
230 ## around a deficiency in the option parser.
231 run ip6tables -N accept-non-init-frag
232 run ip6tables -A accept-non-init-frag -j RETURN \
234 run ip6tables -A accept-non-init-frag -j ACCEPT
237 ## allowservices CHAIN PROTO SERVICE ...
239 ## Add rules to allow the SERVICES on the CHAIN.
242 chain=$1 proto=$2; shift 2
249 left=${svc%:*} right=${svc#*:}
250 case $left in *[!0-9]*) eval left=\$port_$left ;; esac
251 case $right in *[!0-9]*) eval right=\$port_$right ;; esac
256 case $svc in *[!0-9]*) eval svc=\$port_$svc ;; esac
260 *: | :* | "" | *[!0-9:]*)
261 echo >&2 "Bad service name"
265 count=$(( $count + $n ))
266 if [ $count -gt 15 ]; then
267 run ip46tables -A $chain -p $proto -m multiport -j ACCEPT \
268 --destination-ports ${list#,}
277 run ip46tables -A $chain -p $proto -m multiport -j ACCEPT \
278 --destination-ports ${list#,}
281 run ip46tables -A $chain -p $proto -j ACCEPT \
282 --destination-port ${list#,}
287 ## ntpclient CHAIN NTPSERVER ...
289 ## Add rules to CHAIN to allow NTP with NTPSERVERs.
294 run iptables -A $chain -s $ntp -j ACCEPT \
295 -p udp --source-port 123 --destination-port 123
301 ## Add rules to allow CHAIN to be a DNS resolver.
306 run ip46tables -A $chain -j ACCEPT \
307 -m state --state ESTABLISHED \
308 -p $p --source-port 53
312 ## openports CHAIN [MIN MAX]
314 ## Add rules to CHAIN to allow the open ports.
318 [ $# -eq 0 ] && set -- $open_port_min $open_port_max
319 run ip46tables -A $chain -p tcp -g interesting --destination-port $1:$2
320 run ip46tables -A $chain -p udp -g interesting --destination-port $1:$2
324 ###--------------------------------------------------------------------------
325 ### Packet classification.
327 ### See `classify.m4' for an explanation of how the firewall machinery for
328 ### packet classification works.
330 ### A list of all network names is kept in `allnets'. For each network NET,
331 ### shell variables are defined describing their properties.
333 ### net_class_NET The class of the network, as defined by
335 ### net_inet_NET List of IPv4 address ranges in the network.
336 ### net_inet6_NET List of IPv6 address ranges in the network.
337 ### net_fwd_NET List of other networks that this one forwards to.
338 ### net_hosts_NET List of hosts known to be in the network.
339 ### host_inet_HOST IPv4 address of the named HOST.
340 ### host_inet6_HOST IPv6 address of the named HOST.
342 ### Similarly, a list of hosts is kept in `allhosts', and for each host HOST,
343 ### a shell variables are defined:
345 ### host_ifaces_HOST List of interfaces for this host and the networks
346 ### they attach to, in the form IFACE=NET.
348 ## defbitfield NAME WIDTH
350 ## Defines MASK_NAME and BIT_NAME symbolic constants for dealing with
351 ## bitfields: x << BIT_NAME yields the value x in the correct position, and
352 ## ff & MASK_NAME extracts the corresponding value.
356 eval MASK_$name=$(( (1 << $width) - 1 << $bitindex ))
357 eval BIT_$name=$bitindex
358 bitindex=$(( $bitindex + $width ))
361 ## Define the layout of the bitfield.
367 ## defnetclass NAME FORWARD-TO...
369 ## Defines a netclass called NAME, which is allowed to forward to the
370 ## FORWARD-TO netclasses.
372 ## For each netclass, constants from_NAME and to_NAME are defined as the
373 ## appropriate values in the FROM and TO fields (i.e., not including any mask
376 ## This function also establishes mangle chains mark-from-NAME and
377 ## mark-to-NAME for applying the appropriate mark bits to the packet.
379 ## Because it needs to resolve forward references, netclasses must be defined
380 ## in a two-pass manner, using a loop of the form
382 ## for pass in 1 2; do netclassindex=0; ...; done
390 ## Pass 1. Establish the from_NAME and to_NAME constants, and the
391 ## netclass's mask bit.
392 trace "netclass $name = $netclassindex"
393 eval from_$name=$(( $netclassindex << $BIT_FROM ))
394 eval to_$name=$(( $netclassindex << $BIT_TO ))
395 eval _mask_$name=$(( 1 << ($netclassindex + $BIT_MASK) ))
400 ## Pass 2. Compute the actual from and to values. We're a little bit
401 ## clever during source classification, and set the TO field to
402 ## all-bits-one, so that destination classification needs only a single
404 from=$(( ($netclassindex << $BIT_FROM) + (0xf << $BIT_TO) ))
406 eval bit=\$_mask_$net
407 from=$(( $from + $bit ))
409 to=$(( ($netclassindex << $BIT_TO) + \
410 (0xf << $BIT_FROM) + \
411 (1 << ($netclassindex + $BIT_MASK)) ))
412 trace "from $name --> set $(printf %x $from)"
413 trace " to $name --> and $(printf %x $from)"
415 ## Now establish the mark-from-NAME and mark-to-NAME chains.
416 clearchain mangle:mark-from-$name mangle:mark-to-$name
417 run ip46tables -t mangle -A mark-from-$name -j MARK --set-mark $from
418 run ip46tables -t mangle -A mark-to-$name -j MARK --and-mark $to
421 netclassindex=$(( $netclassindex + 1 ))
426 ## Define a network. Follow by calls to `addr', `forwards', etc. to define
427 ## properties of the network. Networks are processed in order, so if their
428 ## addresses overlap then the more specific addresses should be defined
433 eval net_class_$1=\$class
436 ## addr ADDRESS/LEN ...
438 ## Define addresses for the network being defined. ADDRESSes are in
439 ## colon-separated IPv6 or dotted-quad IPv4 form.
443 *:*) addword net_inet6_$net $i ;;
444 *) addword net_inet_$net $i ;;
451 ## Declare that packets from this network are forwarded to the other NETs.
453 eval "net_fwd_$net=\"$*\""
458 ## Declare that packets from this network must not be forwarded to the other
461 eval "net_noxit_$net=\"$*\""
464 ## host HOST ADDR ...
466 ## Define the address of an individual host on the current network. The
467 ## ADDRs may be full IPv4 or IPv6 addresses, or offsets from the containing
468 ## network address, which is a simple number for IPv4, or a suffix beginning
469 ## with `::' for IPv6. If an IPv6 base address is provided for the network
470 ## but not for the host then the host's IPv4 address is used as a suffix.
474 ## Work out which addresses we've actually been given.
477 case "$i" in ::*) a6=$i ;; *) a=$i ;; esac
481 *) echo >&2 "$0: no address for $name"; exit 1 ;;
483 case "${a6+t}" in t) ;; *) a6=::$a ;; esac
485 ## Work out the IPv4 address.
486 eval nn=\$net_inet_$net
491 case $a in *.*) aa=$a ;; *) aa=$base.$(( $offset + $a )) ;; esac
492 eval host_inet_$name=$aa
495 ## Work out the IPv6 address.
496 eval nn=\$net_inet6_$net
500 case $a in ::*) aa=$addr$a ;; *) aa=$a ;; esac
501 eval host_inet6_$name=$aa
504 ## Remember the host in the list.
505 addword net_hosts_$net $name
510 ## Define a new host. Follow by calls to `iface' to define the host's
514 addword allhosts $host
515 eval host_type_$host=endsys
520 ## Declare the host to be a router, so it should forward packets and so on.
522 eval host_type_$host=router
525 ## iface IFACE NET ...
527 ## Define a host's interfaces. Specifically, declares that the host has an
528 ## interface IFACE attached to the listed NETs.
532 addword host_ifaces_$host $name=$net
536 ## net_interfaces HOST NET
538 ## Determine the interfaces on which packets may plausibly arrive from the
539 ## named NET. Returns `-' if no such interface exists.
541 ## This algorithm is not very clever. It's just about barely good enough to
542 ## deduce transitivity through a simple routed network; with complicated
543 ## networks, it will undoubtedly give wrong answers. Check the results
544 ## carefully, and, if necessary, list the connectivity explicitly; use the
545 ## special interface `-' for networks you know shouldn't send packets to a
550 ## Determine the locally attached networks.
552 eval ii=\$host_ifaces_$host
553 for i in $ii; do targets=$targets$i:; done
555 ## Determine the transitivity.
560 ## First pass. Determine whether any of the networks we're considering
561 ## are in the target set. If they are, then return the corresponding
570 n=${tg%=$net:*}; tg=${n%:*}:; n=${n##*:}
575 case $any in nil) break ;; esac
578 case "$found" in ?*) echo $found; return ;; esac
580 ## No joy. Determine the set of networks which (a) these ones can
581 ## forward to, and (b) that we've not considered already. These are the
582 ## nets we'll consider next time around.
586 eval fwd=\$net_fwd_$net
588 case $seen in *":$n:"*) continue ;; esac
590 eval noxit=\$net_noxit_$n
591 case " $noxit " in *" $startnet "*) continue ;; esac
592 case " $nextnets " in
594 *) addword nextnets $n; any=t ;;
599 ## If we've run out of networks then there's no reachability. Return a
601 case $any in nil) echo -; return ;; esac
607 ###----- That's all, folks --------------------------------------------------