Jenkins controller unable to connect to agents after ssh reconfiguration

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Hello,

I have added some lines to the /etc/ssh/sshd_config file to fix two low level vilnerabilities reported by Nessus as:

  • SSH Weak Key Exchange Algorithms Enabled
  • SSH Server CBC Mode Ciphers Enabled

The lines I added were:

KexAlgorithms curve25519-sha256@libssh.org,ecdh-sha2-nistp256,ecdh-sha2-ni,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256

Ciphers aes128-ctr,aes192-ctr,aes256-ctr

MACs hmac-sha1,umac-64@openssh.com,hmac-ripemd160

After restarting the SSH server, it was observed that Jenkins master was unable to communicate with the agent servers.

Is there any specific reason and what are the recommended workarounds? Please advise.

Regards,

Indunil12

2

What does your node log in Jenkins say? What does your sshd log in the server say?

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