mdw@git.distorted.org.uk Git - firewall/blob - functions.m4

   1 ### -*-m4-*-
   2 ###
   3 ### Utility functions for firewall scripts
   4 ###
   5 ### (c) 2008 Mark Wooding
   6 ###
   7
   8 ###----- Licensing notice ---------------------------------------------------
   9 ###
  10 ### This program is free software; you can redistribute it and/or modify
  11 ### it under the terms of the GNU General Public License as published by
  12 ### the Free Software Foundation; either version 2 of the License, or
  13 ### (at your option) any later version.
  14 ###
  15 ### This program is distributed in the hope that it will be useful,
  16 ### but WITHOUT ANY WARRANTY; without even the implied warranty of
  17 ### MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18 ### GNU General Public License for more details.
  19 ###
  20 ### You should have received a copy of the GNU General Public License
  21 ### along with this program; if not, write to the Free Software Foundation,
  22 ### Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  23
  24 m4_divert(20)m4_dnl
  25 ###--------------------------------------------------------------------------
  26 ### Utility functions.
  27
  28 ## doit COMMAND ARGS...
  29 ##
  30 ## If debugging, print the COMMAND and ARGS.  If serious, execute them.
  31 run () {
  32   set -e
  33   if [ "$FW_DEBUG" ]; then echo "* $*"; fi
  34   if ! [ "$FW_NOACT" ]; then "$@"; fi
  35 }
  36
  37 ## trace MESSAGE...
  38 ##
  39 ## If debugging, print the MESSAGE.
  40 trace () {
  41   set -e
  42   if [ "$FW_DEBUG" ]; then echo "$*"; fi
  43 }
  44
  45 ## defport NAME NUMBER
  46 ##
  47 ## Define $port_NAME to be NUMBER.
  48 defport () {
  49   name=$1 number=$2
  50   eval port_$name=$number
  51 }
  52
  53 m4_divert(22)m4_dnl
  54 ###--------------------------------------------------------------------------
  55 ### Basic chain constructions.
  56
  57 ## clearchain CHAIN CHAIN ...
  58 ##
  59 ## Ensure that the named chains exist and are empty.
  60 clearchain () {
  61   set -e
  62   for chain; do
  63     case $chain in
  64       *:*) table=${chain%:*} chain=${chain#*:} ;;
  65       *) table=filter ;;
  66     esac
  67     run iptables -t $table -N $chain
  68   done
  69 }
  70
  71 ## errorchain CHAIN ACTION ARGS ...
  72 ##
  73 ## Make a chain which logs a message and then invokes some other action,
  74 ## typically REJECT.  Log messages are prefixed by `fw: CHAIN'.
  75 errorchain () {
  76   set -e
  77   chain=$1; shift
  78   case $chain in
  79     *:*) table=${chain%:*} chain=${chain#*:} ;;
  80     *) table=filter ;;
  81   esac
  82   clearchain $table:$chain
  83   run iptables -t $table -A $chain -j LOG \
  84           -m limit --limit 3/minute --limit-burst 10 \
  85           --log-prefix "new fw: $chain " --log-level notice
  86   run iptables -t $table -A $chain -j "$@"
  87 }
  88
  89 m4_divert(24)m4_dnl
  90 ###--------------------------------------------------------------------------
  91 ### Basic option setting.
  92
  93 ## setopt OPTION VALUE
  94 ##
  95 ## Set an IP sysctl.
  96 setopt () {
  97   set -e
  98   opt=$1; shift; val=$*
  99   run sysctl -q net/ipv4/$opt="$val"
 100 }
 101
 102 ## setdevopt OPTION VALUE
 103 ##
 104 ## Set an IP interface-level sysctl.
 105 setdevopt () {
 106   set -e
 107   opt=$1; shift; val=$*
 108   for i in /proc/sys/net/ipv4/conf/*; do
 109     [ -f $i/$opt ] &&
 110       run sysctl -q net/ipv4/conf/${i#/proc/sys/net/ipv4/conf/}/$opt="$val"
 111   done
 112 }
 113
 114 m4_divert(26)m4_dnl
 115 ###--------------------------------------------------------------------------
 116 ### Packet filter construction.
 117
 118 ## conntrack CHAIN
 119 ##
 120 ## Add connection tracking to CHAIN, and allow obvious stuff.
 121 conntrack () {
 122   set -e
 123   chain=$1
 124   run iptables -A $chain -p tcp -m state \
 125           --state ESTABLISHED,RELATED -j ACCEPT
 126   run iptables -A $chain -p tcp ! --syn -g bad-tcp
 127 }
 128
 129 ## allowservices CHAIN PROTO SERVICE ...
 130 ##
 131 ## Add rules to allow the SERVICES on the CHAIN.
 132 allowservices () {
 133   set -e
 134   chain=$1 proto=$2; shift 2
 135   count=0
 136   list=
 137   for svc; do
 138     case $svc in
 139       *:*)
 140         n=2
 141         left=${svc%:*} right=${svc#*:}
 142         case $left in *[!0-9]*) eval left=\$port_$left ;; esac
 143         case $right in *[!0-9]*) eval right=\$port_$right ;; esac
 144         svc=$left:$right
 145         ;;
 146       *)
 147         n=1
 148         case $svc in *[!0-9]*) eval svc=\$port_$svc ;; esac
 149         ;;
 150     esac
 151     case $svc in
 152       *: | :* | "" | *[!0-9:]*)
 153         echo >&2 "Bad service name"
 154         exit 1
 155         ;;
 156     esac
 157     count=$(( $count + $n ))
 158     if [ $count -gt 15 ]; then
 159       run iptables -A $chain -p $proto -m multiport -j ACCEPT \
 160              --destination-ports ${list#,}
 161       list= count=$n
 162     fi
 163     list=$list,$svc
 164   done
 165   case $list in
 166     "")
 167       ;;
 168     ,*,*)
 169       run iptables -A $chain -p $proto -m multiport -j ACCEPT \
 170               --destination-ports ${list#,}
 171       ;;
 172     *)
 173       run iptables -A $chain -p $proto -j ACCEPT \
 174               --destination-port ${list#,}
 175       ;;
 176   esac
 177 }
 178
 179 ## ntpclient CHAIN NTPSERVER ...
 180 ##
 181 ## Add rules to CHAIN to allow NTP with NTPSERVERs.
 182 ntpclient () {
 183   set -e
 184   chain=$1; shift
 185   for ntp; do
 186     run iptables -A $chain -s $ntp -j ACCEPT \
 187             -p udp --source-port 123 --destination-port 123
 188   done
 189 }
 190
 191 ## dnsresolver CHAIN
 192 ##
 193 ## Add rules to allow CHAIN to be a DNS resolver.
 194 dnsresolver () {
 195   set -e
 196   chain=$1
 197   for p in tcp udp; do
 198     run iptables -A $chain -j ACCEPT \
 199              -m state --state ESTABLISHED \
 200              -p $p --source-port 53
 201   done
 202 }
 203
 204 ## openports CHAIN [MIN MAX]
 205 ##
 206 ## Add rules to CHAIN to allow the open ports.
 207 openports () {
 208   set -e
 209   chain=$1; shift
 210   [ $# -eq 0 ] && set -- $open_port_min $open_port_max
 211   run iptables -A $chain -p tcp -g interesting --destination-port $1:$2
 212   run iptables -A $chain -p udp -g interesting --destination-port $1:$2
 213 }
 214
 215 m4_divert(28)m4_dnl
 216 ###--------------------------------------------------------------------------
 217 ### Packet classification.
 218
 219 ## defbitfield NAME WIDTH
 220 ##
 221 ## Defines MASK_NAME and BIT_NAME symbolic constants for dealing with
 222 ## bitfields: x << BIT_NAME yields the value x in the correct position, and
 223 ## ff & MASK_NAME extracts the corresponding value.
 224 defbitfield () {
 225   set -e
 226   name=$1 width=$2
 227   eval MASK_$name=$(( (1 << $width) - 1 << $bitindex ))
 228   eval BIT_$name=$bitindex
 229   bitindex=$(( $bitindex + $width ))
 230 }
 231
 232 ## Define the layout of the bitfield.
 233 bitindex=0
 234 defbitfield MASK 16
 235 defbitfield FROM 4
 236 defbitfield TO 4
 237
 238 ## defnetclass NAME FORWARD-TO...
 239 ##
 240 ## Defines a netclass called NAME, which is allowed to forward to the
 241 ## FORWARD-TO netclasses.
 242 ##
 243 ## For each netclass, constants from_NAME and to_NAME are defined as the
 244 ## appropriate values in the FROM and TO fields (i.e., not including any mask
 245 ## bits).
 246 ##
 247 ## This function also establishes mangle chains mark-from-NAME and
 248 ## mark-to-NAME for applying the appropriate mark bits to the packet.
 249 ##
 250 ## Because it needs to resolve forward references, netclasses must be defined
 251 ## in a two-pass manner, using a loop of the form
 252 ##
 253 ##   for pass in 1 2; do netclassindex=0; ...; done
 254 netclassess=
 255 defnetclass () {
 256   set -e
 257   name=$1; shift
 258   case $pass in
 259     1)
 260
 261       ## Pass 1.  Establish the from_NAME and to_NAME constants, and the
 262       ## netclass's mask bit.
 263       eval from_$name=$(( $netclassindex << $BIT_FROM ))
 264       eval to_$name=$(( $netclassindex << $BIT_TO ))
 265       eval _mask_$name=$(( 1 << ($netclassindex + $BIT_MASK) ))
 266       nets="$nets $name"
 267       ;;
 268     2)
 269
 270       ## Pass 2.  Compute the actual from and to values.  We're a little bit
 271       ## clever during source classification, and set the TO field to
 272       ## all-bits-one, so that destination classification needs only a single
 273       ## AND operation.
 274       from=$(( ($netclassindex << $BIT_FROM) + (0xf << $BIT_TO) ))
 275       for net; do
 276         eval bit=\$_mask_$net
 277         from=$(( $from + $bit ))
 278       done
 279       to=$(( ($netclassindex << $BIT_TO) + \
 280              (0xf << $BIT_FROM) + \
 281              (1 << ($netclassindex + $BIT_MASK)) ))
 282       trace "from $name --> set $(printf %x $from)"
 283       trace "  to $name --> and $(printf %x $from)"
 284
 285       ## Now establish the mark-from-NAME and mark-to-NAME chains.
 286       clearchain mangle:mark-from-$name mangle:mark-to-$name
 287       run iptables -t mangle -A mark-from-$name -j MARK --set-mark $from
 288       run iptables -t mangle -A mark-to-$name -j MARK --and-mark $to
 289       ;;
 290   esac
 291   netclassindex=$(( $netclassindex + 1 ))
 292 }
 293
 294 ## defiface NAME NETCLASS:NETWORK/MASK...
 295 ##
 296 ## Declares a network interface NAME and associates with it a number of
 297 ## reachable networks.  During source classification, a packet arriving on
 298 ## interface NAME from an address in NETWORK/MASK is classified as coming
 299 ## from to NETCLASS.  During destination classification, all packets going to
 300 ## NETWORK/MASK are classified as going to NETCLASS, regardless of interface
 301 ## (which is good, because the outgoing interface hasn't been determined
 302 ## yet).
 303 ##
 304 ## As a special case, the NETWORK/MASK can be the string `default', which
 305 ## indicates that all addresses not matched elsewhere should be considered.
 306 ifaces=:
 307 defaultiface=none
 308 allnets=
 309 defiface () {
 310   set -e
 311   name=$1; shift
 312   case $ifaces in
 313     *:"$name":*) ;;
 314     *)
 315       clearchain mangle:in-$name
 316       run iptables -t mangle -A in-classify -i $name -g in-$name
 317       ;;
 318   esac
 319   ifaces=$ifaces$name:
 320   for item; do
 321     netclass=${item%:*} addr=${item#*:}
 322     case $addr in
 323       default)
 324         defaultiface=$name
 325         defaultclass=$netclass
 326         run iptables -t mangle -A out-classify -g mark-to-$netclass
 327         ;;
 328       *)
 329         run iptables -t mangle -A in-$name -s $addr -g mark-from-$netclass
 330         run iptables -t mangle -A out-classify -d $addr -g mark-to-$netclass
 331         allnets="$allnets $name:$addr"
 332         ;;
 333     esac
 334   done
 335 }
 336
 337 ## defvpn IFACE CLASS NET HOST:ADDR ...
 338 ##
 339 ## Defines a VPN interface.  If the interface has the form `ROOT+' (i.e., a
 340 ## netfilter wildcard) then define a separate interface ROOTHOST routing to
 341 ## ADDR; otherwise just write a blanket rule allowing the whole NET.  All
 342 ## addresses concerned are put in the named CLASS.
 343 defvpn () {
 344   set -e
 345   iface=$1 class=$2 net=$3; shift 3
 346   case $iface in
 347     *-+)
 348       root=${iface%+}
 349       for host; do
 350         name=${host%:*} addr=${host#*:}
 351         defiface $root$name $class:$addr
 352       done
 353       ;;
 354     *)
 355       defiface $iface $class:$net
 356       ;;
 357   esac
 358 }
 359
 360 m4_divert(-1)
 361 ###----- That's all, folks --------------------------------------------------