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Calculating a SSH host key with paramiko

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  • Post category:Python

I needed to compare a host key from something other than a known_hosts file with what paramiko reports as part of the SSH connection today. If you must know, the host keys for these machines are retrieved a XMLRPC API… It turned out to be a lot easier than I thought. Here’s how I produced the host key entry as it appears in that API (as well as in the known_hosts file):

    #!/usr/bin/python

# A host key calculation example for Paramiko.
# Args:
#   1: hostname

import base64
import os
import paramiko
import socket
import sys

# Socket connection to remote host
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sock.connect((sys.argv[1], 22))

# Build a SSH transport
t = paramiko.Transport(sock)
t.start_client()
key = t.get_remote_server_key()

print '%s %s' %(key.get_name(),
                base64.encodestring(key.__str__()).replace('\n', ''))

t.close()
sock.close()

Note that I could also have constructed a paramiko key object based on the output of the XMLRPC API and then compared those two objects, but I prefer the human readable strings.

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