Well today I spent a bit of time looking up how /etc/shadow created their shadow passwords.
I found a good source for the method at http://www.akkadia.org/drepper/SHA-crypt.txt , and if you take some time to review it you will notice the steps are a bit involved
Lucky for us Python has a Crypt module that works nicely.
First off I started by creating a dummy user with the password of test on one of my Linux computers:
# cat /etc/shadow | grep dummy dummy:$6$JJ1sbaL/$2P4ZcZ10VjIa9f5.8N/GJukYCg.RJVBTP2h30v2mnh0Q5izqc2rtKZ6qtI0Ewiyji 0hX9zIVfftOVuJTIsBSKQ/:15310:0:99999:7:::
And like that we have a password we can attempt to validate.
Next I will need to define our salt in Python. A good article explaining the format of /etc/shadow can be found on cyberciti.biz. Like the article says the salt is found between the $ after the username and before the password hash. For comparison I will also extract the hash:
>>> salt = 'JJ1sbaL/' >>> hash = '2P4ZcZ10VjIa9f5.8N/GJukYCg.RJVBTP2h30v2mnh0Q5izqc2rtKZ6qtI0Ewiyj0hX9zIVfftOVuJTIsBSKQ/'
Now that we have our salt we can create a hash of our password using that salt and verify it matches the hash shown in /etc/shadow :
>>> import crypt >>> output = crypt.crypt('test', '$6$%s$' % salt) >>> print output $6$JJ1sbaL/$2P4ZcZ10VjIa9f5.8N/GJukYCg.RJVBTP2h30v2mnh0Q5izqc2rtKZ6qtI0Ewiyj0hX9zIVfftOVuJTIsBSKQ/
And lastly lets compare the new hash with the one found in /etc/shadow :
>>> newhash = output.split('$')[-1] >>> print newhash '2P4ZcZ10VjIa9f5.8N/GJukYCg.RJVBTP2h30v2mnh0Q5izqc2rtKZ6qtI0Ewiyj0hX9zIVfftOVuJTIsBSKQ/' >>> >>> newhash == hash True