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

   1 #!/bin/bash
   2 # Copyright (C) 2016 Ian Kelling
   3
   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/errcatch-function
  19 source /a/bin/errhandle/errallow-function
  20 source /a/bin/errhandle/bash-trace-function
  21 errcatch
  22
  23 usage() {
  24     cat <<'EOF'
  25 Usage: mail-route start|stop|show
  26
  27 Marks tcp packets on port 25 and 143 to be routed through
  28 a vpn ip.
  29 EOF
  30     exit $1
  31 }
  32
  33 if (( $# != 1 )); then
  34     usage 1
  35 fi
  36
  37 start() {
  38     iptables_op=-A
  39     ip_op=add
  40     # systemd around stretch release time, would wait until openvpn actually connected,
  41     # so this was unnecessary, but now it returns immediately.
  42     found=false
  43     for ((i=1; i<=30; i++)); do
  44         tun_dev=$(ip a show to 10.8.0.4/24 | sed -rn '1s/^\S+\s+([^:]+).*/\1/p')
  45         if [[ $tun_dev == tun* ]]; then
  46             found=true
  47             break
  48         fi
  49         sleep 1
  50     done
  51     if ! $found; then
  52         echo "$0: error: timeout waiting for valid tun_dev, currently:$tun_dev"
  53         exit 1
  54     fi
  55     e() { "$@"; }
  56     _errcatch_cleanup=stop
  57     modify
  58 }
  59 stop() {
  60     iptables_op=-D
  61     ip_op=del
  62     tun_dev=$(iptables -t nat -S | sed -rn "s/^-A POSTROUTING -o (tun[[:digit:]]+) -m mark --mark 0x1 -j SNAT --to-source 10.8.0.4$/\1/p"|head -n1) || printf "failed to find tun device.\n"
  63     e() { "$@" || printf "maybe ok failure: %s\n" "$*"; }
  64     modify
  65 }
  66
  67 show() {
  68     e() { printf "${0##*/}: %s\n" "$*"; "$@"; }
  69     e iptables -t mangle -S
  70     e iptables -t nat -S
  71     e ip rule
  72     e ip route show table 1
  73
  74     tun_dev=$(ip a show to 10.8.0.4/24 | sed -rn '1s/^\S+\s+([^:]+).*/\1/p')
  75     if [[ $tun_dev == tun* ]]; then
  76         e sysctl net.ipv4.conf.$tun_dev.rp_filter
  77     else
  78         echo "$0: note, no tun device found"
  79     fi
  80     exit 0
  81 }
  82
  83
  84 # code common to start and stop.
  85 modify() {
  86     # match source or dest port. note, when we send to a port, it picks a random high port as
  87     # the source.
  88     for port in 25 143; do # smtp and imap.
  89         e iptables -t mangle $iptables_op \
  90           OUTPUT -m tcp -p tcp -m multiport --ports $port -j MARK --set-mark 0x1
  91         e iptables -t mangle $iptables_op \
  92           OUTPUT -m tcp -p tcp -m multiport --ports $port -j MARK --set-mark 0x0 \
  93           -d 10.0.0.0/8,172.16.0.0/12,192.168.0.0/16
  94         # note, we could have used a custom chain and returned instead of setting the mark again.
  95         # 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
  96
  97     done
  98     e iptables -t nat $iptables_op POSTROUTING -o $tun_dev -m mark --mark 0x1 -j SNAT --to-source 10.8.0.4
  99     e ip rule $ip_op fwmark 1 table 1
 100     # note, this rule does not persist when the tun interface is deleted
 101     e ip route $ip_op default via 10.8.0.1 table 1
 102
 103     # on debian this is 0 (no filter), on ubuntu it\'s 1, which is no good. 0 or 2 both work fine.
 104     # 2 drops it if the packet is not routable, martian address, or my default route is screwed up,
 105     # so, eh, might as well. some rhel docs recommend using it.
 106     e sysctl net.ipv4.conf.$tun_dev.rp_filter=2
 107
 108     exit 0
 109 }
 110
 111 case $1 in
 112     start|stop|show) $1 ;;
 113     *) usage 1 ;;
 114 esac
 115
 116
 117 # background: something like this does not work for packets which
 118 # exim is replying to. I don't know why.
 119 #iptables -t mangle -A OUTPUT -m owner --uid-owner Debian-exim -j MARK --set-mark 0x1