[Twisted-Python] smtp-server: issue with checkers.FilePasswordDB and hash

[aleuser at inwind.it]

Hi all,
   I use FilePasswordDB with a small smtp-server (a very small toy), but when 
I use the hash function the authentication doesn't work.

Here few lines of code:
"""
def _hash(name, clearpsw, hashedpsw):
    # a very simple hash function ?
    return md5.md5(clearpsw).hexdigest()
    # return 'aa'

# doesn't work; password file content is correctly "hashed"
smtpusers = checkers.FilePasswordDB('smtppasswords.txt', caseSensitive=True, 
hash=_hash, cache=True)

# work! in the file the passwords are in plain text
#smtpusers = checkers.FilePasswordDB('smtppasswords.txt', caseSensitive=True, 
cache=True)

mailservice = mail.MailService()
mailservice.setQueue(relaymanager.Queue(QUEUE_PATH))
mailservice.smtpPortal.registerChecker(smtpusers)
smtpserver = mailservice.getESMTPFactory()
application = service.Application("Console SMTP Server")
internet.TCPServer(SMTP_PORT, smtpserver).setServiceParent(application)
"""

The error is:
Failure: twisted.cred.error.UnhandledCredentials: No checker for twisted.cred.
credentials.IUsernameHashedPassword

Obviously FilePasswordDB doesn't provide that credential when there is the 
hash function; why smtp connection is hashed and not in plaintext? How can I 
get it works?

I found a similar question, with no answer:
http://twistedmatrix.com/pipermail/twisted-python/2006-November/014395.html


Thanks
Alessandro