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/$opt ]; then
186 run sysctl -q net/$ver/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 clearchain ntp-servers
295 for ntp; do run iptables -A ntp-servers -j ACCEPT -s $ntp; done
296 run iptables -A $ntpchain -j ntp-servers \
297 -p udp --source-port 123 --destination-port 123
302 ## Add rules to allow CHAIN to be a DNS resolver.
307 run ip46tables -A $chain -j ACCEPT \
308 -m state --state ESTABLISHED \
309 -p $p --source-port 53
315 ## Add rules to allow CHAIN to be a DNS server.
320 ## Allow TCP access. Hitting us with SYNs will make us deploy SYN cookies,
321 ## but that's tolerable.
322 run ip46tables -A $chain -j ACCEPT -p tcp --destination-port 53
324 ## Avoid being a DDoS amplifier by rate-limiting incoming DNS queries.
325 clearchain $chain-udp-dns
326 run ip46tables -A $chain-udp-dns -j ACCEPT \
327 -m limit --limit 20/second --limit-burst 300
328 run ip46tables -A $chain-udp-dns -g dns-rate-limit
329 run ip46tables -A $chain -j $chain-udp-dns \
330 -p udp --destination-port 53
333 ## openports CHAIN [MIN MAX]
335 ## Add rules to CHAIN to allow the open ports.
339 [ $# -eq 0 ] && set -- $open_port_min $open_port_max
340 run ip46tables -A $chain -p tcp -g interesting --destination-port $1:$2
341 run ip46tables -A $chain -p udp -g interesting --destination-port $1:$2
345 ###--------------------------------------------------------------------------
346 ### Packet classification.
348 ### See `classify.m4' for an explanation of how the firewall machinery for
349 ### packet classification works.
351 ### A list of all network names is kept in `allnets'. For each network NET,
352 ### shell variables are defined describing their properties.
354 ### net_class_NET The class of the network, as defined by
356 ### net_inet_NET List of IPv4 address ranges in the network.
357 ### net_inet6_NET List of IPv6 address ranges in the network.
358 ### net_fwd_NET List of other networks that this one forwards to.
359 ### net_hosts_NET List of hosts known to be in the network.
360 ### host_inet_HOST IPv4 address of the named HOST.
361 ### host_inet6_HOST IPv6 address of the named HOST.
363 ### Similarly, a list of hosts is kept in `allhosts', and for each host HOST,
364 ### a shell variables are defined:
366 ### host_ifaces_HOST List of interfaces for this host and the networks
367 ### they attach to, in the form IFACE=NET.
369 ## defbitfield NAME WIDTH
371 ## Defines MASK_NAME and BIT_NAME symbolic constants for dealing with
372 ## bitfields: x << BIT_NAME yields the value x in the correct position, and
373 ## ff & MASK_NAME extracts the corresponding value.
377 eval MASK_$name=$(( (1 << $width) - 1 << $bitindex ))
378 eval BIT_$name=$bitindex
379 bitindex=$(( $bitindex + $width ))
382 ## Define the layout of the bitfield.
388 ## defnetclass NAME FORWARD-TO...
390 ## Defines a netclass called NAME, which is allowed to forward to the
391 ## FORWARD-TO netclasses.
393 ## For each netclass, constants from_NAME and to_NAME are defined as the
394 ## appropriate values in the FROM and TO fields (i.e., not including any mask
397 ## This function also establishes mangle chains mark-from-NAME and
398 ## mark-to-NAME for applying the appropriate mark bits to the packet.
400 ## Because it needs to resolve forward references, netclasses must be defined
401 ## in a two-pass manner, using a loop of the form
403 ## for pass in 1 2; do netclassindex=0; ...; done
411 ## Pass 1. Establish the from_NAME and to_NAME constants, and the
412 ## netclass's mask bit.
413 trace "netclass $name = $netclassindex"
414 eval from_$name=$(( $netclassindex << $BIT_FROM ))
415 eval to_$name=$(( $netclassindex << $BIT_TO ))
416 eval fwd_$name=$(( 1 << ($netclassindex + $BIT_MASK) ))
421 ## Pass 2. Compute the actual from and to values. This is fiddly:
422 ## we want to preserve the other flags.
423 from=$(( ($netclassindex << $BIT_FROM) ))
424 frommask=$(( $MASK_FROM | $MASK_MASK ))
427 from=$(( $from + $bit ))
429 to=$(( ($netclassindex << $BIT_TO) ))
430 tomask=$(( $MASK_MASK ^ (1 << ($netclassindex + $BIT_MASK)) ))
431 trace "from $name --> set $(printf %08x/%08x $from $frommask)"
432 trace " to $name --> and $(printf %08x/%08x $to $tomask)"
434 ## Now establish the mark-from-NAME and mark-to-NAME chains.
435 clearchain mangle:mark-from-$name mangle:mark-to-$name
436 run ip46tables -t mangle -A mark-from-$name -j MARK \
437 --set-xmark $from/$frommask
438 run ip46tables -t mangle -A mark-to-$name -j MARK \
439 --set-xmark $to/$tomask
442 netclassindex=$(( $netclassindex + 1 ))
447 ## Define a network. Follow by calls to `addr', `forwards', etc. to define
448 ## properties of the network. Networks are processed in order, so if their
449 ## addresses overlap then the more specific addresses should be defined
454 eval net_class_$1=\$class
457 ## addr ADDRESS/LEN ...
459 ## Define addresses for the network being defined. ADDRESSes are in
460 ## colon-separated IPv6 or dotted-quad IPv4 form.
464 *:*) addword net_inet6_$net $i ;;
465 *) addword net_inet_$net $i ;;
472 ## Declare that packets from this network are forwarded to the other NETs.
474 eval "net_fwd_$net=\"$*\""
479 ## Declare that packets from this network must not be forwarded to the other
482 eval "net_noxit_$net=\"$*\""
485 ## host HOST ADDR ...
487 ## Define the address of an individual host on the current network. The
488 ## ADDRs may be full IPv4 or IPv6 addresses, or offsets from the containing
489 ## network address, which is a simple number for IPv4, or a suffix beginning
490 ## with `::' for IPv6. If an IPv6 base address is provided for the network
491 ## but not for the host then the host's IPv4 address is used as a suffix.
495 ## Work out which addresses we've actually been given.
498 case "$i" in ::*) a6=$i ;; *) a=$i ;; esac
502 *) echo >&2 "$0: no address for $name"; exit 1 ;;
504 case "${a6+t}" in t) ;; *) a6=::$a ;; esac
506 ## Work out the IPv4 address.
507 eval nn=\$net_inet_$net
512 case $a in *.*) aa=$a ;; *) aa=$base.$(( $offset + $a )) ;; esac
513 eval host_inet_$name=$aa
516 ## Work out the IPv6 address.
517 eval nn=\$net_inet6_$net
521 case $a6 in ::*) aa=$base$a6 ;; *) aa=$a6 ;; esac
522 eval host_inet6_$name=$aa
525 ## Remember the host in the list.
526 addword net_hosts_$net $name
531 ## Define a new host. Follow by calls to `iface' to define the host's
535 addword allhosts $host
536 eval host_type_$host=server
541 ## Declare the host to have the given type.
545 router | server | client) ;;
546 *) echo >&2 "$0: bad host type \`$type'"; exit 1 ;;
548 eval host_type_$host=$type
551 ## iface IFACE NET ...
553 ## Define a host's interfaces. Specifically, declares that the host has an
554 ## interface IFACE attached to the listed NETs.
558 addword host_ifaces_$host $name=$net
562 ## Build rules which match a particular collection of networks.
563 ## Specifically, use the address-comparison operator OPT (typically `-s' or
564 ## `-d') to match the addresses of NOT, writing the rules to the chain
565 ## BASESUFFIX. If we find a match, dispatch to WIN-CLASS, where CLASS is
566 ## the class of the matching network. In order to deal with networks
567 ## containing negative address ranges, more chains may need to be
568 ## constructed; they will be named BASE#Q for sequence numbers Q starting
569 ## with NEXT. All of this happens on the `mangle' table, and there isn't
570 ## (currently) a way to tweak this.
572 ## The FLAGS gather additional interesting information about the job,
573 ## separated by colons. The only flag currently is :default: which means
574 ## that the default network was listed.
576 ## Finally, there is a hook PREPARE which is called just in advance of
577 ## processing the final network, passing it the argument FLAGS. (The PREPARE
578 ## string will be subjected to shell word-splitting, so it can provide some
579 ## arguments of its own if it wants.) It should set `mode' to indicate how
580 ## the chain should be finished.
582 ## goto If no networks matched, then issue a final `goto' to the
583 ## chain named by the variable `fail'.
585 ## call Run `$finish CHAIN' to write final rules to the named CHAIN
586 ## (which may be suffixed from the original BASE argument if
587 ## this was necessary). This function will arrange to call
588 ## these rules if no networks match.
590 ## ret If no network matches then return (maybe by falling off the
591 ## end of the chain).
593 local opt win flags prepare base suffix next net lose splitp
594 opt=$1 win=$2 flags=$3 prepare=$4 base=$5 suffix=$6 next=$7 net=$8
597 ## If this is the default network, then set the flag.
598 case "$net" in default) flags=${flags}default: ;; esac
600 ## Do an initial pass over the addresses to see whether there are any
601 ## negative ranges. If so, we'll need to split. See also the standard
604 eval "addrs=\"\$net_inet_$net \$net_inet6_$net\""
605 for a in $addrs; do case $a in !*) splitp=t; break ;; esac; done
607 trace "MATCHNETS [splitp $splitp] $opt $win $flags [$prepare] $base $suffix $next : $net $*"
609 ## Work out how to handle matches against negative address ranges. If this
610 ## is the last network, invoke the PREPARE hook to find out. Otherwise, if
611 ## we have to split the chain, recursively build the target here.
615 case $splitp,$mode in
623 clearchain mangle:$base#$next
624 lose="-g $base#$next"
631 clearchain mangle:$base#$next
632 matchnets $opt $win $flags "$prepare" \
633 $base \#$next $(( $next + 1 )) "$@"
634 lose="-g $base#$next" mode=goto
641 ## Populate the chain with rules to match the necessary networks.
642 eval addr=\$net_inet_$net addr6=\$net_inet6_$net class=\$net_class_$net
645 !*) run iptables -t mangle -A $base$suffix $lose $opt ${a#!} ;;
646 *) run iptables -t mangle -A $base$suffix -g $win-$class $opt $a ;;
651 !*) run ip6tables -t mangle -A $base$suffix $lose $opt ${a#!} ;;
652 *) run ip6tables -t mangle -A $base$suffix -g $win-$class $opt $a ;;
656 ## Wrap up the chain appropriately. If we didn't split and there are more
657 ## networks to handle then append the necessary rules now. (If we did
658 ## split, then we already wrote the rules for them above.) If there are no
659 ## more networks then consult the `mode' setting to find out what to do.
660 case $splitp,$#,$mode in
662 *,*,goto) run ip46tables -t mangle -A $base$suffix $lose ;;
663 t,0,call) $finish $base#$next ;;
664 nil,0,call) $finish $base$suffix ;;
666 matchnets $opt $win $flags "$prepare" $base "$suffix" $next "$@"
671 ## net_interfaces HOST NET
673 ## Determine the interfaces on which packets may plausibly arrive from the
674 ## named NET. Returns `-' if no such interface exists.
676 ## This algorithm is not very clever. It's just about barely good enough to
677 ## deduce transitivity through a simple routed network; with complicated
678 ## networks, it will undoubtedly give wrong answers. Check the results
679 ## carefully, and, if necessary, list the connectivity explicitly; use the
680 ## special interface `-' for networks you know shouldn't send packets to a
685 ## Determine the locally attached networks.
687 eval ii=\$host_ifaces_$host
688 for i in $ii; do targets=$targets$i:; done
690 ## Determine the transitivity.
695 ## First pass. Determine whether any of the networks we're considering
696 ## are in the target set. If they are, then return the corresponding
705 n=${tg%=$net:*}; tg=${n%:*}:; n=${n##*:}
710 case $any in nil) break ;; esac
713 case "$found" in ?*) echo $found; return ;; esac
715 ## No joy. Determine the set of networks which (a) these ones can
716 ## forward to, and (b) that we've not considered already. These are the
717 ## nets we'll consider next time around.
721 eval fwd=\$net_fwd_$net
723 case $seen in *":$n:"*) continue ;; esac
725 eval noxit=\$net_noxit_$n
726 case " $noxit " in *" $startnet "*) continue ;; esac
727 case " $nextnets " in
729 *) addword nextnets $n; any=t ;;
734 ## If we've run out of networks then there's no reachability. Return a
736 case $any in nil) echo -; return ;; esac
742 ###----- That's all, folks --------------------------------------------------