paramiko Incompatible ssh peer (no acceptable kex algorithm)

Question

I\'m getting the following error when trying to ssh to a Cisco ACS device using the paramiko library. I\'ve used paramiko in python without issue, and I can ssh to this box

Answer 1

That error is in a situation where your version of paramiko does not support the key exchange algorithms that is using the device you want to connect.

ssh.connect('10.119.94.8', 22, username="user",password='passwor')
t = ssh.get_transport()
so = t.get_security_options()
so.kex
('diffie-hellman-group1-sha1', 'diffie-hellman-group-exchange-sha1')
so.ciphers
('aes128-ctr', 'aes256-ctr', 'aes128-cbc', 'blowfish-cbc', 'aes256-cbc', '3des-cbc', 'arcfour128', 'arcfour256')
paramiko.__version__
'1.10.1'

In the paramiko logs you can see the key exchange algos of your connection.

DEB paramiko.transport: starting thread (client mode): 0x11897150L
INF paramiko.transport: Connected (version 2.0, client OpenSSH_7.2)
DEB paramiko.transport: kex algos:['diffie-hellman-group14-sha1', 'ecdh-sha2-nistp256', 'ecdh-sha2-nistp384'] server key:['ssh-rsa'] client encrypt:['aes128-ctr', 'aes256-ctr'] server encrypt:['aes128-ctr', 'aes256-ctr'] client mac:['hmac-sha1'] server mac:['hmac-sha1'] client compress:['none', 'zlib@openssh.com'] server compress:['none', 'zlib@openssh.com'] client lang:[''] server lang:[''] kex follows?False
ERR paramiko.transport: Exception: Incompatible ssh peer (no acceptable kex algorithm)
ERR paramiko.transport: Traceback (most recent call last):
ERR paramiko.transport:     raise SSHException('Incompatible ssh peer (no acceptable kex algorithm)')
ERR paramiko.transport: SSHException: Incompatible ssh peer (no acceptable kex algorithm)

So I recommend to upgrade to a recent paramiko version, for example 2.4.2 for 2018. In this version is supported sha1 and sha2 for key exchange algorithms.

>>> ssh.connect("hostdev",22,username="user",password="pass")
>>> transport1=ssh.get_transport()
>>> so=transport1.get_security_options()
>>> so.kex
('ecdh-sha2-nistp256', 'ecdh-sha2-nistp384', 'ecdh-sha2-nistp521', 'diffie-hellman-group-exchange-sha256', 'diffie-hellman-group-exchange-sha1', 'diffie-hellman-group14-sha1', 'diffie-hellman-group1-sha1')
>>> 
>>> so.ciphers
('aes128-ctr', 'aes192-ctr', 'aes256-ctr', 'aes128-cbc', 'aes192-cbc', 'aes256-cbc', 'blowfish-cbc', '3des-cbc')
>>> 
>>> print paramiko.__version__
2.4.2