Bugtraq mailing list archives
Re: [HACKERS] Postgres: pg_hba.conf, md5, pg_shadow, encrypted
From: Antoine Martin <antoine () nagafix co uk>
Date: Sat, 23 Apr 2005 15:53:25 +0100
On Sat, 2005-04-23 at 09:02 -0400, Stephen Frost wrote:
* Antoine Martin (antoine () nagafix co uk) wrote:Basically, multiple input data that have the same output hash, which is of no use when what you are trying to find is the input. Finding collisions quicker for a known input is one thing, but that is not going to reduce the search space, not even your storage space (it is unlikely that the colliding results would all be valid input).Erm, you aren't necessairly trying to find the input... It may be the case that you're trying to find what you need to authenticate to this server, or any other PostgreSQL server where the same userid & input are used. In that case you just need something that hashes to the same thing.
Agreed, what I said was that it is highly unlikely you will find colliding inputs that are valid, so the "SHA weakness" does not really help you here as it does not reduce the search space: You are much better off pre-calculating hashes for possible usernames & passwords than working backwards and generating all possible hashes hoping that one would happen to be matching a real entry... Usernames are not exactly random, passwords are less predictable, the chance of a useful collision on the username+password is remote at best.
Using a random salt would mean that it's different per server so breaking it on one doesn't help you against another server unless you happened to find the actual original input.
Absolutely.
Is adding the non-guessable salt that hard anyway?It is if you want to continue to support the 'md5' method in pg_hba.conf because the wireline protocol will probably need to change. A less intrusive alternative would be to add an 'with encrypted password 'xyz' with random salt' or some such which would only be supported with the 'password' method in pg_hba.conf. One problem with this is that you then can't just switch from password to md5 or back again. Perhaps that's ok though? Comments?
Just add another authentication method - call it 'md5-salt' (sharing most of the 'md5' code), you get backwards compatibility and you advise users to migrate to the new salt hash. Shouldn't be too hard... Might as well do a 'sha512-salt' too. Antoine
Current thread:
- Re: [HACKERS] Postgres: pg_hba.conf, md5, pg_shadow, encrypted passwords, (continued)
- Re: [HACKERS] Postgres: pg_hba.conf, md5, pg_shadow, encrypted passwords Tom Lane (Apr 20)
- Re: [HACKERS] Postgres: pg_hba.conf, md5, pg_shadow, encrypted passwords Bruce Momjian (Apr 20)
- Re: [HACKERS] Postgres: pg_hba.conf, md5, pg_shadow, encrypted passwords Tom Lane (Apr 20)
- Re: [HACKERS] Postgres: pg_hba.conf, md5, pg_shadow, encrypted passwords David F. Skoll (Apr 21)
- Re: [HACKERS] Postgres: pg_hba.conf, md5, pg_shadow, encrypted passwords Jim C. Nasby (Apr 20)
- Re: [HACKERS] Postgres: pg_hba.conf, md5, pg_shadow, encrypted passwords Stephen Frost (Apr 21)
- Re: [HACKERS] Postgres: pg_hba.conf, md5, pg_shadow, encrypted passwords Bruno Wolff III (Apr 22)
- Re: [HACKERS] Postgres: pg_hba.conf, md5, pg_shadow, encrypted passwords Stephen Frost (Apr 22)
- Re: [HACKERS] Postgres: pg_hba.conf, md5, pg_shadow, encrypted passwords Antoine Martin (Apr 22)
- Re: [HACKERS] Postgres: pg_hba.conf, md5, pg_shadow, encrypted Stephen Frost (Apr 23)
- Re: [HACKERS] Postgres: pg_hba.conf, md5, pg_shadow, encrypted Antoine Martin (Apr 23)
- Re: [HACKERS] Postgres: pg_hba.conf, md5, pg_shadow, encrypted passwords Joshua D. Drake (Apr 21)
- Re: [HACKERS] Postgres: pg_hba.conf, md5, pg_shadow, encrypted passwords Stephen Frost (Apr 21)
- Re: [HACKERS] Postgres: pg_hba.conf, md5, pg_shadow, encrypted passwords Lance James (Apr 21)
- Re: [HACKERS] Postgres: pg_hba.conf, md5, pg_shadow, encrypted passwords Tino Wildenhain (Apr 21)
- Re: [HACKERS] Postgres: pg_hba.conf, md5, pg_shadow, encrypted Rod Taylor (Apr 21)
- Re: [HACKERS] Postgres: pg_hba.conf, md5, pg_shadow, encrypted Tino Wildenhain (Apr 21)
- Re: [HACKERS] Postgres: pg_hba.conf, md5, pg_shadow, encrypted Michael Samuel (Apr 22)
- Re: [HACKERS] Postgres: pg_hba.conf, md5, pg_shadow, encrypted passwords Jim Knoble (Apr 21)
- RE: [HACKERS] Postgres: pg_hba.conf, md5, pg_shadow, encrypted passwords Mike Fratto (Apr 21)
- Re: [HACKERS] Postgres: pg_hba.conf, md5, pg_shadow, encrypted passwords Stephen Frost (Apr 21)