bugtraq - RE: [HACKERS] Postgres: pg_hba.conf, md5, pg

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Date: Thu, 21 Apr 2005 15:31:42 -0600
From: "Mark Senior" <Mark.Senior@....ab.ca>
To: "Mike Fratto" <mfratto@....com>
Cc: <bugtraq@...urityfocus.com>
Subject: RE: [HACKERS] Postgres: pg_hba.conf, md5, pg_shadow, encrypted passwords

It also slows down cracking numerous passwords in parallel using a
dictionary/heuristic approach a la john the ripper - without a salt, you
can calculate the hash of each password guess once, and then scan
through an entire shadow file for the hash.  With salts, you have to
hash each guess once per user in the list, or at least per user you're
interested in attacking.

In the case of the postgres passwords, the user name seems to act as a
sort of "public" salt.  Knowing some user IDs, you might precompute a
set of hashes for each targetted user, in anticipation of getting your
hands on the password hashes later.

Mark

> -----Original Message-----
> From: Mike Fratto  

> I am pretty sure the intent the salt is to make 
> pre-computation of a dictionaries infeasable due to storage 
> requirements. It doesn't really add to the keyspace because 
> the salt is known and doesn't have to be guessed.

--- end of sensible content ---

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