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I've implemented my mail server as dictated here.

It works perfectly fine. My curiousity revolves around entering users into the database and authenticating them

Running:

INSERT INTO users (email, password) VALUES ('sales@example.com', ENCRYPT('password'));

Multiple times will give a different hash for the encrypted password as its utilizing a random salt. I.e. If I enter sales@example.com three times with the same password each hash is different...

My question to this is, how is it that the Postfix server can actually authenticate the password when a user logs in via a mail client?

There isn't any problem per say as it works fine, more just to satisfy my curiosity so I can fully understand whats going on behind the scenes to properly authenticate the encrypted password.

Raptor
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CogitoErgoSum
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3 Answers3

4

Postfix compares the password from the database to a new encrypt done with the salt(password from db).

to encrypt:

update user set password = ENCRYPT('1234') where id = 1

to check password:

SELECT u.* FROM user u where u.email ='admin@dominio.com' 
and ENCRYPT('1234', u.password) = u.password
Eduardo Nobre
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Read man crypt: it returns the salt in the first two chars of the return value.

So the salt is not lost, you can compare the encrypted string to the result of crypt( 'pass', $first_two_chars_of_encrypted_value ).

Frank N
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man
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You must use ENCRYPT('pass','salt') to force a salt, otherwise the salt is lost forever and you have no way of recovering it. Fairly pointless function without it. It's a terrible function to use, though, because the security is so minimal; use PASSWORD() or OLD_PASSWORD() instead.

ENCRYPT() uses the system crypt(), which may use all or only the first 8 characters, must be printable 7-bit ascii, generally uses 1 round of a DES-based hash, and is completely unportable. Avoid it.

SilverbackNet
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    If the salt is lost forever, then his configuration wouldn't actually work. I agree that encrypt doesn't sound like a good solution, but is there a way to get postfix to accept something else? – EricP Jun 13 '11 at 03:29