Use expect in bash script to provide password to S

Question

To those who want to reply that I should use SSH keys please abstain

I'm trying to use expect in an bash script to provide the SSH password. Providing the password works but I don't end up in the SSH session as I should, it goes back strait to bash.

My script:

#!/bin/bash

read -s PWD

/usr/bin/expect <<EOD
spawn ssh -oStrictHostKeyChecking=no -oCheckHostIP=no usr@$myhost.example.com'
expect "password"
send "$PWD\n" 
EOD
echo "you're out"

The output of my script:

spawn ssh -oStrictHostKeyChecking=no -oCheckHostIP=no usr@$myhost.example.com
usr@$myhost.example.com's password: you're out

I would like to have my SSH session and only when I exit it to go back to my bash script. The reason why I am using bash before expect is because I have use a menu I can choose which unit to connect to.

Thanks

Answer 1

Mixing bash and expect is not a good way to achieve the desired effect. I'd try to use only Expect:

#!/usr/bin/expect
eval spawn ssh -oStrictHostKeyChecking=no -oCheckHostIP=no usr@$myhost.example.com
#use correct prompt
set prompt ":|#|\\\$"
interact -o -nobuffer -re $prompt return
send "my_password\r"
interact -o -nobuffer -re $prompt return
send "my_command1\r"
interact -o -nobuffer -re $prompt return
send "my_command2\r"
interact

Sample solution for bash could be:

#!/bin/bash
/usr/bin/expect -c 'expect "\n" { eval spawn ssh -oStrictHostKeyChecking=no -oCheckHostIP=no usr@$myhost.example.com; interact }'

This will wait for enter and than return (for a moment) interactive session.

Answer 2

A simple expect script

Remotelogin.exp

    #!/usr/bin/expect
    set user [lindex $argv 1]
    set ip [lindex $argv 0]
    set password [lindex $argv 2]
    spawn ssh $user@$ip
    expect "password"
    send "$password\r"
    interact

Example:

    ./Remotelogin.exp <ip> <user name> <password>

Answer 3

Also make sure to use

send -- "$PWD\r" 

instead, as passwords starting with a dash (-) will fail otherwise.

The above wont interpret a string starting with a dash as an option to the send command.

Answer 4

The easiest way is to use sshpass. This is available in Ubuntu/Debian repos and you don't have to deal with integrating expect with bash.

An example:

sshpass -p<password> ssh <arguments>
sshpass -ptest1324 ssh user@192.168.1.200 ls -l /tmp

The above command can be easily integrated with a bash script.

Note: Please read Security Considerations section in man sshpass for full understanding of security implications.

Answer 5

Another way that I found useful to use a small expect script from a bash script is as follows.

...
bash-script start
bash-commands
...
expect - <<EOF 
spawn your-command-here
expect "some-pattern"
send "some-command"
...
...
EOF
...
more bash commands
...

This works because ...If the string "-" is supplied as a filename, standard input is read instead...

Answer 6

Add the 'interact' expect command just before your EOD:

#!/bin/bash

read -s PWD

/usr/bin/expect <<EOD
spawn ssh -oStrictHostKeyChecking=no -oCheckHostIP=no usr@$myhost.example.com'
expect "password"
send "$PWD\n" 
interact
EOD
echo "you're out"

This should let you interact with the remote machine until you logout. Then you'll be back in bash.