iankelling.org Git - distro-setup/blob - mail-route

   1 #!/bin/bash
   2 # Copyright (C) 2016 Ian Kelling
   3 set -x
   4 # Licensed under the Apache License, Version 2.0 (the "License");
   5 # you may not use this file except in compliance with the License.
   6 # You may obtain a copy of the License at
   7
   8 #     http://www.apache.org/licenses/LICENSE-2.0
   9
  10 # Unless required by applicable law or agreed to in writing, software
  11 # distributed under the License is distributed on an "AS IS" BASIS,
  12 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  13 # See the License for the specific language governing permissions and
  14 # limitations under the License.
  15
  16 [[ $EUID == 0 ]] || exec sudo "$BASH_SOURCE" "$@"
  17
  18 source /a/bin/errhandle/err
  19
  20 usage() {
  21   cat <<'EOF'
  22 Usage: mail-route up|down|show
  23
  24 Marks tcp packets on port 25, 143 and 587 to be routed through
  25 a vpn ip. If called from --up/--down in openvpn, (we have multiple args) $1 is the
  26 tun_dev, and action is from $script_type.
  27
  28 Is idempotent.
  29 EOF
  30   exit $1
  31 }
  32
  33 if (( $# < 1 )); then
  34   usage 1
  35 fi
  36
  37 up() {
  38   start=true
  39   stop=false
  40   iptables_op=-A
  41   ip_op=add
  42   timeout_secs=20
  43   if [[ ! $tun_dev ]]; then
  44     # delays because I was running this outside of openvpn before
  45     found=false
  46     for ((i=1; i<=timeout_secs; i++)); do
  47       tun_dev=$(ip a show to 10.8.0.4/24 | sed -rn '1s/^\S+\s+([^:]+).*/\1/p')
  48       if [[ $tun_dev == tun* ]]; then
  49         found=true
  50         break
  51       fi
  52       sleep 1
  53     done
  54     if ! $found; then
  55       echo "$0: error: timeout after $timeout_secs waiting for valid tun_dev, currently:$tun_dev"
  56       exit 1
  57     fi
  58   fi
  59   e() { echo "$0: $*"; "$@"; }
  60   _errcatch_cleanup=stop
  61   modify
  62   # we leave it as is even when stopping, because we would like it to be default, but the only way
  63   # to change the default is for every device, and I want to avoid that, even though I wouldn't mind, others users of this script might.
  64   val=$(sysctl -n net.ipv4.conf.$tun_dev.rp_filter)
  65   if [[ $val != 2 ]]; then
  66     echo "net.ipv4.conf.$tun_dev.rp_filter = $val"
  67     e sysctl net.ipv4.conf.$tun_dev.rp_filter=2
  68   fi
  69
  70 }
  71 down() {
  72   start=false
  73   stop=true
  74   iptables_op=-D
  75   ip_op=del
  76   # note, this is not going to work if the interface has been deleted.
  77   # we could also check for an iptable rule that on some tun interface like the one
  78   # we use, but meh, the way I'm using the script now, tun_dev is supplied by openvpn
  79   if [[ ! tun_dev ]]; then
  80     tun_dev=$(ip a show to 10.8.0.4/24 | sed -rn '1s/^\S+\s+([^:]+).*/\1/p')
  81   fi
  82   e() { echo "$0: $*"; "$@" || printf "maybe ok failure: %s\n" "$*"; }
  83   modify
  84 }
  85
  86 show() {
  87   e() { printf "${0##*/}: %s\n" "$*"; "$@"; }
  88   e iptables -t mangle -S
  89   e iptables -t nat -S
  90   e ip rule
  91   e ip route show table 1
  92
  93   tun_dev=$(ip a show to 10.8.0.4/24 | sed -rn '1s/^\S+\s+([^:]+).*/\1/p')
  94   if [[ $tun_dev == tun* ]]; then
  95     e sysctl net.ipv4.conf.$tun_dev.rp_filter
  96   else
  97     echo "$0: note, no tun device found"
  98   fi
  99   exit 0
 100 }
 101
 102 runtest() {
 103   # debugging:
 104   #echo start=$start stop=$stop exists=$exists
 105   { $start && ! $exists; } || { $stop && $exists; }
 106 }
 107
 108 iptmod() { #iptables modify
 109   local check cmd="$*" exists=true
 110   ${cmd/-[AD]/-C} &>/dev/null || exists=false
 111   if runtest; then e $cmd; fi
 112 }
 113
 114 # code common to start and stop.
 115 modify() {
 116   # match source or dest port. note, when we send to a port, it picks a random high port as
 117   # the source.
 118   for port in 25 143 587; do # smtp and imap.
 119     iptcommon="OUTPUT -m tcp -p tcp -m multiport --ports $port -j MARK --set-mark"
 120     iptmod iptables -t mangle $iptables_op $iptcommon 0x1
 121     iptmod iptables -t mangle $iptables_op $iptcommon 0x0 -d 10.0.0.0/8,172.16.0.0/12,192.168.0.0/16,127.0.0.0/8
 122     # note, we could have used a custom chain and returned instead of setting the mark again.
 123     # in case anyone was ever curious, the inverse of private ips is:   #0.0.0.0/5,8.0.0.0/7,11.0.0.0/8,12.0.0.0/6,16.0.0.0/4,32.0.0.0/3,64.0.0.0/2,128.0.0.0/3,160.0.0.0/5,168.0.0.0/6,172.0.0.0/12,172.32.0.0/11,172.64.0.0/10,172.128.0.0/9,173.0.0.0/8,174.0.0.0/7,176.0.0.0/4,192.0.0.0/9,192.128.0.0/11,192.160.0.0/13,192.169.0.0/16,192.170.0.0/15,192.172.0.0/14,192.176.0.0/12,192.192.0.0/10,193.0.0.0/8,194.0.0.0/7,196.0.0.0/6,200.0.0.0/5,208.0.0.0/4,224.0.0.0/3
 124   done
 125
 126   if [[ $tun_dev ]]; then
 127     # when $tun_dev goes away, so does this rul
 128     iptmod iptables -t nat $iptables_op POSTROUTING -o $tun_dev -m mark --mark 0x1 -j SNAT --to-source 10.8.0.4
 129   fi
 130
 131
 132   iprulecmd="fwmark 1 table 1"
 133   exists=true; ip rule show $iprulecmd | grep . &>/dev/null || exists=false
 134   if runtest; then e ip rule $ip_op $iprulecmd; fi
 135
 136   iproutecmd="default via 10.8.0.1 table 1"
 137   exists=true; ip route show $iproutecmd | grep . &>/dev/null || exists=false
 138   if runtest; then e ip route $ip_op $iproutecmd; fi
 139
 140   # on debian this is 0 (no filter), on ubuntu it\'s 1, which is no good. 0 or 2 both work fine.
 141   # 2 drops it if the packet is not routable, martian address, or my default route is screwed up,
 142   # so, eh, might as well. some rhel docs recommend using it.
 143
 144
 145 }
 146
 147 if (( $# > 1 )); then
 148   tun_dev=$1
 149   $script_type
 150 else
 151   case $1 in
 152     up|down|show) $1 ;;
 153     *) usage 1 ;;
 154   esac
 155 fi
 156
 157
 158
 159 exit 0
 160
 161
 162 # background: something like this does not work for packets which
 163 # exim is replying to. I don't know why.
 164 #iptables -t mangle -A OUTPUT -m owner --uid-owner Debian-exim -j MARK --set-mark 0x1