Custom Login Module that should check only userId with out passwd

Hi All,

Can we write a custom login module which should check user name in the HTTPHeader and let the user login if the user id exists in the userstore(Active Directory Server).

It should not validate with the passwd, as the requesting server sends only the user id in the HTtp Header.

Is it possible to do this ?if so can anyone give me some inouts. I know how to configure cutom login module. But i am not sure with out validating th epasswd we can let the user log in through custom login module.

can anyone send me sample code.

Thanks a lot

Lakshmi