using Jenkins I can't connect to a Debian Jessie box via ssh

Question

Using Jenkin CI's 'SSH plugin' I can not make a connection to a Debian Jessie box using password auth. I am able to ssh to the box directly with my local terminal no problem. I don't have the same issue with Debian Wheezy or Ubuntu LTS. Any ideas? Not an iptables issue, the firewall is wide open.

Answer 1

openssh-server 6.7 changes are at fault:

http://www.openssh.com/txt/release-6.7

Changes since OpenSSH 6.6
=========================

Potentially-incompatible changes

 * sshd(8): The default set of ciphers and MACs has been altered to
   remove unsafe algorithms. In particular, CBC ciphers and arcfour*
   are disabled by default.

   The full set of algorithms remains available if configured
   explicitly via the Ciphers and MACs sshd_config options.

I think Jenkins needs to update the ssh clients to a supported and secure cipher. I added the below to my sshd_config and it did the trick:

KexAlgorithms curve25519-sha256@libssh.org,ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group14-sha1,diffie-hellman-group-exchange-sha1,diffie-hellman-group1-sha1

Anyone happen to know which of these ciphers is the one Jenkins uses?