Python's safest method to store and retrieve passwords from a database.

Question

Looking to store usernames and passwords in a database, and am wondering what the safest way to do so is. I know I have to use a salt somewhere, but am not sure how to generate it securely or how to apply it to encrypt the password. Some sample Python code would be greatly appreciated. Thanks.

Answer 1

Store the password+salt as a hash and the salt. Take a look at how django does it: basic docs and source. In the db they store <type of hash>$<salt>$<hash> in a single char field. You can also store the three parts in separate fields.

The function to set the password:

def set_password(self, raw_password):
    import random
    algo = 'sha1'
    salt = get_hexdigest(algo, str(random.random()), str(random.random()))[:5]
    hsh = get_hexdigest(algo, salt, raw_password)
    self.password = '%s$%s$%s' % (algo, salt, hsh)

The get_hexdigest is just a thin wrapper around some hashing algorithms. You can use hashlib for that. Something like hashlib.sha1('%s%s' % (salt, hash)).hexdigest()

And the function to check the password:

def check_password(raw_password, enc_password):
    """
    Returns a boolean of whether the raw_password was correct. Handles
    encryption formats behind the scenes.
    """
    algo, salt, hsh = enc_password.split('$')
    return hsh == get_hexdigest(algo, salt, raw_password)

Answer 2

If you have enough control over both endpoints of the application, the absolute best way is using SRP.