Re: [HACKERS] Postgres: pg_hba.conf, md5, pg_shadow, encrypted passwords

From: Jim Knoble (jmknoble_at_pobox.com)
Date: 04/21/05

  • Next message: Mandriva Security Team: "MDKSA-2005:073 - Updated cvs packages fix vulnerability" 
    Date: Wed, 20 Apr 2005 22:58:34 -0400
To: bugtraq@securityfocus.com

    Circa 2005-04-20 dixit Jim C. Nasby:

    : Actually, it's not as silly as you think. You can download rainbow
    : tables for Windows/LanMan passwords up to 14 or 15 characters in length.
    : Given the password hash and some code, you can determine the user's
    : password in a matter of minutes.

    I thought the idea of the salt was to aid in expanding the keyspace.
    Even though the salt is known (in traditional Unix
    passwd/shadow/master.passwd databases, it's stored at the beginning of
    the password field), appending the salt to the password expands the
    keyspace to length(password) + length(salt). With a (barely) reasonable
    8-byte password and an 8-byte salt, that gives you a 128-bit key (if you
    use password+salt as the key). Remember that the keyspace for a 16-byte
    password is (theoretically) 256 times as large as the keyspace for a
    15-byte password. If you require 10- or 12-byte passwords and add 12
    bytes of salt, you approach 192-bit keys and get a keyspace between
    10^14 and 10^21 times as large as 15-byte passwords (assuming your
    password hash algorithm can handle 192-bit keys). Even a 160-bit key
    (20 bytes = 10-byte password + 10-byte salt) has a formidable keyspace,
    for now, assuming high-quality keys: 10^48 keys * 20 bytes is a lot of
    storage space.

    : Simply put, MD5 is no longer strong enough for protecting secrets. It's
    : just too easy to brute-force. SHA1 is ok for now, but it's days are
    : numbered as well. I think it would be good to alter SHA1 (or something
    : stronger) as an alternative to MD5[...].

    "Something stronger" being bcrypt-2a, based on Blowfish. Solar
    Designer's public domain implementation is here:

        http://www.openwall.com/crypt/ 

    -- 
jim knoble  |  jmknoble@pobox.com  |  http://www.pobox.com/~jmknoble/
(GnuPG fingerprint: 809F:09B9:9686:D035:4AB0::9455:124B:0A62:DD6A:76D6)
 .....................................................................
 :"The methods now being used to merchandise the political candidate :
 : as though he were a deodorant positively guarantee the electorate :
 : against ever hearing the truth about anything."   --Aldous Huxley :
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