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. Is idempotent.
  29 EOF
  30     exit $1
  31 }
  32
  33 if (( $# != 1 )); then
  34     usage 1
  35 fi
  36
  37 start() {
  38     start=true
  39     stop=false
  40     iptables_op=-A
  41     ip_op=add
  42     # systemd around stretch release time, would wait until openvpn actually connected,
  43     # so this was unnecessary, but now it returns immediately.
  44     found=false
  45     for ((i=1; i<=30; i++)); do
  46         tun_dev=$(ip a show to 10.8.0.4/24 | sed -rn '1s/^\S+\s+([^:]+).*/\1/p')
  47         if [[ $tun_dev == tun* ]]; then
  48             found=true
  49             break
  50         fi
  51         sleep 1
  52     done
  53     if ! $found; then
  54         echo "$0: error: timeout waiting for valid tun_dev, currently:$tun_dev"
  55         exit 1
  56     fi
  57     e() { echo "$0: $*"; "$@"; }
  58     _errcatch_cleanup=stop
  59     modify
  60     # we leave it as is even when stopping, because we would like it to be default, but the only way
  61     # 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.
  62     e sysctl net.ipv4.conf.$tun_dev.rp_filter=2
  63 }
  64 stop() {
  65     start=false
  66     stop=true
  67     iptables_op=-D
  68     ip_op=del
  69     tun_dev=$(ip a show to 10.8.0.4/24 | sed -rn '1s/^\S+\s+([^:]+).*/\1/p')
  70     e() { echo "$0: $*"; "$@" || printf "maybe ok failure: %s\n" "$*"; }
  71     modify
  72 }
  73
  74 show() {
  75     e() { printf "${0##*/}: %s\n" "$*"; "$@"; }
  76     e iptables -t mangle -S
  77     e iptables -t nat -S
  78     e ip rule
  79     e ip route show table 1
  80
  81     tun_dev=$(ip a show to 10.8.0.4/24 | sed -rn '1s/^\S+\s+([^:]+).*/\1/p')
  82     if [[ $tun_dev == tun* ]]; then
  83         e sysctl net.ipv4.conf.$tun_dev.rp_filter
  84     else
  85         echo "$0: note, no tun device found"
  86     fi
  87     exit 0
  88 }
  89
  90 runtest() {
  91     # debugging:
  92     #echo start=$start stop=$stop exists=$exists
  93     { $start && ! $exists; } || { $stop && $exists; }
  94 }
  95
  96 iptmod() { #iptables modify
  97     local check cmd="$*" exists=true
  98     ${cmd/-[AD]/-C} &>/dev/null || exists=false
  99     if runtest; then e $cmd; fi
 100 }
 101
 102 # code common to start and stop.
 103 modify() {
 104     # match source or dest port. note, when we send to a port, it picks a random high port as
 105     # the source.
 106     for port in 25 143; do # smtp and imap.
 107         iptcommon="OUTPUT -m tcp -p tcp -m multiport --ports $port -j MARK --set-mark"
 108         iptmod iptables -t mangle $iptables_op $iptcommon 0x1
 109         iptmod iptables -t mangle $iptables_op $iptcommon 0x0 -d 10.0.0.0/8,172.16.0.0/12,192.168.0.0/16
 110         # note, we could have used a custom chain and returned instead of setting the mark again.
 111         # 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
 112     done
 113
 114     if [[ $tun_dev ]]; then
 115         # when $tun_dev goes away, so does this rul
 116     iptmod iptables -t nat $iptables_op POSTROUTING -o $tun_dev -m mark --mark 0x1 -j SNAT --to-source 10.8.0.4
 117     fi
 118
 119
 120     iprulecmd="fwmark 1 table 1"
 121     exists=true; ip rule show $iprulecmd | grep . &>/dev/null || exists=false
 122     if runtest; then e ip rule $ip_op $iprulecmd; fi
 123
 124     iproutecmd="default via 10.8.0.1 table 1"
 125     exists=true; ip route show $iproutecmd | grep . &>/dev/null || exists=false
 126     if runtest; then e ip route $ip_op $iproutecmd; fi
 127
 128     # on debian this is 0 (no filter), on ubuntu it\'s 1, which is no good. 0 or 2 both work fine.
 129     # 2 drops it if the packet is not routable, martian address, or my default route is screwed up,
 130     # so, eh, might as well. some rhel docs recommend using it.
 131
 132
 133     exit 0
 134 }
 135
 136 case $1 in
 137     start|stop|show) $1 ;;
 138     *) usage 1 ;;
 139 esac
 140
 141
 142 # background: something like this does not work for packets which
 143 # exim is replying to. I don't know why.
 144 #iptables -t mangle -A OUTPUT -m owner --uid-owner Debian-exim -j MARK --set-mark 0x1