Library to work with SSH public keys

[Darren Spruell]

On Sat, Apr 6, 2013 at 5:49 AM, Roy Smith <roy at panix.com> wrote:
> In article <mailman.187.1365227369.3114.python-list at python.org>,
>  Darren Spruell <phatbuckett at gmail.com> wrote:
>
>> I'd like to work with user submitted/uploaded SSH public keys from
>> Python. I'm trying to solve what I'd thought might be a simple need:
>> given a user's OpenSSH formatted _public_ key (RSA, or DSA, or
>> whatever), how do you obtain information about it such as: key type
>> (e.g. ssh-rsa, etc.); bit length (e.g. 2048); key comment (e.g.
>> user at hostname); key fingerprint? I've been fiddling with the Paramiko
>> API and looked at PyCrypto (supports OpenSSH keys) and Twisted Conch
>> but didn't see anything that looked like it did this.
>>
>> I'm looking for the equivalent to this:
>>
>> $ ssh-keygen -l -f tmp.key.pub
>> 2048 9b:31:06:6a:a4:79:97:33:d7:20:15:1f:cd:b4:86:4d dspruell at Sydney.local
>> (RSA)
>>
>> ...to get the attributes of the public key: key type, bit length,
>> fingerprint and comment.
>>
>> Is there an SSH library capable of doing this from Python? Can break
>> out to shell commands to parse them but I'd prefer not to.
>
> The first hit on googling "paramiko fingerprint" got me this:
>
> http://www.lag.net/paramiko/docs/paramiko.PKey-class.html

Indeed, and I seem to find it's not suited for the need. Many of the
methods appear to assume deriving information about public key parts
from private key input or for handling public keys sent by server when
connecting from client. I can't manage to wrangle desired or accurate
data out of passing in OpenSSH format public keys from a user keypair
(authentication key, not host key).

-- 
Darren Spruell
phatbuckett at gmail.com