Posts tagged openvpn

openvpn and GNU expect

posted on 2016-04-31 20:56

Since I often need openvpn connections and I like to start them from within terminals to see what actually happens, but dislike having to enter AD credentials everytime, here is a solution with expect to this.

Security-wise that's questionable, but I don't need a lection on that.

Replace <CONFIGFILE>, <USERNAME>, <PASSWORD>, of course.

#!/usr/bin/expect -f



## SETUP

# handle ctrl-c
proc sigint_handler {} {
  # send ctrl-c to openvpn process
  send \x03
  # wait for it to die
  sleep 1
  # quit expect session
  exit
}

# catch ctrl-c
trap sigint_handler SIGINT



## RUN

# start shell...
set timeout -1
spawn $env(SHELL)
match_max 100000

# ... and openvpn within there
send -- "sudo openvpn --config <CONFIGNAME>\r"

# username prompt
expect -exact "^[\[0;1;39mEnter Auth Username: ^[\[0m"
send -- "<USERNAME>\r"

# password prompt
expect -exact "^[\[0;1;39mEnter Auth Password: ^[\[0m"
send -- "<PASSWORD>\r"

# make expect wait so it doesn not exit immediately
expect eof

Replace the ^['s above (four times in the code above) with literal escapes. You can insert these in vim by pressing ctrl-v + Esc in linux.

I always set up openvpn to also push DNS settings (resolvconf package and stuff), so there is some CTRL-c-handling necessary so it works and everything closes cleanly.

The escape codes for the expect lines I could discern by using autoexpect.

openvpn: dns pushed on linux

posted on 2016-02-14 22:45:53

To have openvpn push its DNS server successfully through the tunnel, you have to have these settings in your <filename>.ovpn file:

script-security 2
up /etc/openvpn/update-resolv-conf
down /etc/openvpn/update-resolv-conf

and have the package resolvconf installed:

apt install resolvconf

That way your dns servers get exhanged in /etc/resolv.conf everytime the tunnel get established or disconnected.

This was only tested on debian.

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