Bash script calls expect script with master SSH connection

Question

I'm trying to write a bash script that calls an expect script to establish a master SSH connection to be used for the remaining SSH commands in the bash script.

~/.ssh/config:

ControlMaster auto
ControlPath ~/.ssh/control-%r@%h:%p

upload.sh:

#!/usr/bin/bash

expect -f /home/Dave/bin/ssh.exp

scp /home/Dave/bin/test [email protected]:/root/test

ssh [email protected] "echo 'Test' >> /root/test"

ssh -O exit [email protected]

ssh.exp:

#!/usr/bin/expect -f

# Enable some diagnostic output
exp_internal 1

spawn /usr/bin/ssh -M -N [email protected]

expect {
    -re ".*yes.*no.*" {
        exp_send "yes\r"
        exp_continue
    }
    -re ".*password.*" {
        exp_send "OMGSECRET\r"
    }
}

$ bin/upload.sh
spawn /usr/bin/ssh -M -N [email protected]
parent: waiting for sync byte
parent: telling child to go ahead
parent: now unsynchronized from child
spawn: returns {5212}
Gate keeper glob pattern for '.*yes.*no.*' is ''. Not usable, disabling the performance booster.
Gate keeper glob pattern for '.*password.*' is '*password*'. Activating booster.

expect: does "" (spawn_id exp4) match regular expression ".*yes.*no.*"? (No Gate, RE only) gate=yes re=no
".*password.*"? Gate "*password*"? gate=no
[email protected]'s password:
expect: does "[email protected]'s password: " (spawn_id exp4) match regular expression ".*yes.*no.*"? (No Gate, RE only) gate=yes re=no
".*password.*"? Gate "*password*"? gate=yes re=yes
expect: set expect_out(0,string) "[email protected]'s password: "
expect: set expect_out(spawn_id) "exp4"
expect: set expect_out(buffer) "[email protected]'s password: "
send: sending "OMGSECRET\r" to { exp4 }
mux_client_request_session: read from master failed: Connection reset by peer
[email protected]'s password:
[email protected]'s password:

The SSH connection is being established, but it craps out when I try to reuse it for the SCP command. Why?

Possible final sad edit: Alas it appears cygwin doesn't support multiplexing.

Answer 1

Using an Expect script to send a hard-coded plaintext password is generally a Very Bad Idea. If you needs scriptable, passwordless SSH connections, it's far better to use key-pair authentication:

ssh-keygen # and then follow the prompts; don't set a passphrase
ssh-copy-id [email protected]

After doing so, you can ssh [email protected] without needing to key in your password.

You can still use the control connection muxing set up with the Control directives in ~/.ssh/config, and close the master connection with ssh -O exit [email protected].

You ought also to use ssh's utility of simply running commands remotely - once you have key-pair authentication set up, you can have:

ssh [email protected] /etc/init.d/dnsmasq restart

in your script and be all set to go.

Answer 2

if this is still your question:

"The SSH connection is being established, but it craps out when I try to reuse it for the SCP command. Why?"

This happens because you are starting a seperate shell with your expect script. Your ssh session is bound to this shell and if your script ends the shell also end and your ssh session dies.

Sorry but I don't have a solution in a nutshell for this problem.