CODEWITHSUNDEEP
shellautomationrsaexpecthost
ShAn PrIyAn
ShAn PrIyAn

Reputation: 285

How to ignore or Pass 'Yes' when The authenticity of host can't be established in Expect Shell script during Automation

I want to Provide 'Yes' automatically or Ignore it and proceed in a SECURE way, when the below statement comes during execution of my Expect Shell script?.

#!/usr/bin/expect
spawn ssh $user@$host

The authenticity of host 'abcdef (10.566.1.98)' can't be established. RSA key fingerprint is jk:94:ba:93:0b:eb:ff:df:ea:gh:hj:23:3c:hj:9c:be. Are you sure you want to continue connecting (yes/no)?

Upvotes: 28

Views: 38477

Answers (3)

Ben Harper
Ben Harper

Reputation: 2580

This works, and it's especially convenient for docker builds

ssh-keyscan hostname.example.com >> $HOME/.ssh/known_hosts

Upvotes: 13

GreyCat
GreyCat

Reputation: 17104

It's possible to avoid this question and accept all incoming keys automaticatilly by using ssh client option StrictHostKeyChecking set to no (default setting is ask, which results in that question):

ssh -o StrictHostKeyChecking=no "$user@$host"

However, note that it would be hardly any secure, as you're basically accepting connect with everyone who may act as a given host. The only secure way to avoid question is to pre-distribute host public keys to clients, i.e. in form of pre-generated known hosts file, which can be used in some way like that:

ssh \
    -o UserKnownHostsFile=PATH_TO_YOUR_KNOWN_HOSTS_FILE \
    -o StrictHostKeyChecking=yes "$user@$host"

This way you'll avoid the question if the check fails, and ssh will result in non-zero exit status.

Upvotes: 42

Dinesh
Dinesh

Reputation: 16428

Make use of exp_continue for this scenario.

#!/usr/bin/expect 
set prompt "#|>|\\\$"
spawn ssh dinesh@myhost
expect {
        #If 'expect' sees '(yes/no )', then it will send 'yes'
        #and continue the 'expect' loop
        "(yes/no)" { send "yes\r";exp_continue}
        #If 'password' seen first, then proceed as such.
        "password"
}
send "root\r"
expect -re $prompt

Reference : Expect

Upvotes: 7

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