A simple script to validate SSH keys.

ValidateSSH.py

#! /bin/bash/python
# Author : Piyush Bansal
# To check if a key is valid ssh key (rsa)
# REQUIREMENTS : give input a file , that has one ssh-key in it.
# RESULT : valid/not valid ssh-key
# NOTE : initial devel. phase, needs to to tweaked to make it suitable for our use here.



import base64,struct,sys,binascii
key=open('input.txt').read()
array=key.split();
# Each rsa-ssh key has 3 different strings in it, first one being
# typeofkey second one being keystring third one being username .
if len(array) != 3:
	print "not valid key"
	sys.exit()
typeofkey=array[0];string=array[1];username=array[2];
# must have only valid rsa-ssh key characters ie binascii characters 
try :
	data=base64.decodestring(string)
except binascii.Error:
	print "not valid key"
	sys.exit()
a=4
# unpack the contents of data, from data[:4] , it must be equal to 7 , property of ssh key .
try :
	str_len = struct.unpack('>I', data[:a])[0]
except struct.error :
	print "not valid key"
	sys.exit()
# data[4:11] must have string which matches with the typeofkey , another ssh key property.
if data[a:a+str_len] == typeofkey and int(str_len) == int(7): 
	print "valid key"
else:
	print "not valid key"