Hello,

I've got an application where I'm sharing a database with a second (non 
web2py) framework. I want my web2py application to handle user registration 
and would like to avoid users having two passwords (partly so that only 
web2py ever writes to the auth_user table).

Inevitably, the hashed password storage formats differ, but I can match the 
hash algorithm between the two frameworks:

db.auth_user.password.requires = CRYPT(digest_alg='sha512')

Then I can just calculate the value of a second hashed password field in 
the foreign format - it involves recoding the string as base64, not hex, 
but that can be achieved using a computed field.

def alt_password(r):
    passwd = r.password.split('$')
    alt = base64.b64encode(passwd[1].decode('hex')) + \
                '*' + base64.b64encode(passwd[2].decode('hex'))
    return alt


auth.settings.extra_fields['auth_user']= [
    Field('alt_password', compute=lambda r: alt_password(r))
    ]



*Except...* the simple_hash function in web2py uses (password + salt) as an 
input and the second framework uses (salt + password), which means there is 
no way to reproduce the second format from the stored hashed password. I 
can hack the web2py utils.py file on my installation to reverse this but I 
wanted to check if there was a more elegant way of overloading the 
simple_hash function without having to change the codebase, which makes my 
application unstable to upgrade.

I did wonder about extending the settings to include a salt order, but I 
think that would mean you'd have to extend the password string to record 
the order: alg$order$salt$hash. That seems like a bit of a big change for a 
fairly fringe use case!



-- 
Resources:
- http://web2py.com
- http://web2py.com/book (Documentation)
- http://github.com/web2py/web2py (Source code)
- https://code.google.com/p/web2py/issues/list (Report Issues)
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