cracklib-devel

[Cracklib-devel] Security baseline for cracklib (when passwords should be accepted or rejected?)

[Hubert K. <hk...@re...>]

Hi all!

I've done some integration testing with cracklib and discovered
that the passwords are rejected or accepted quite arbitrarily.
At least I don't see any pattern in it.

For example, using English word list, password "1winning1" will
be accepted as secure, but passwords ".):winning,!\" or
"*~[winning#>;" will be rejected as insecure.

The word "winning" has about 10 bits of guessing entropy[1,2,3],
so the above passwords have at most 16 (more realistically 12),
40 and 40 bits of guessing entropy respectively. That's a very
large gap between false positive (IMO) and false negative.

What was the security level to be achieved? What is the
acceptable error from this baseline?

NIST SP 800-63-1 allows for password based authentication with
passwords that have 14 or 20 bits of entropy (for systems
needing Level 1 or Level 2 security respectively). While making
it possible to check if a password has more entropy than that
would be nice, I think those two values would be a good starting
point. So, I think that adding a configuration file that allows
to set the desirable entropy of passwords would be a good new
feature. Adding a new API that allows the programmer to specify
the minimal amount of guessing entropy the password needs to
have would be a good addition to that.

 1: NIST SP 800-63-1, section A.2.2
 2: "Testing Metrics for Password Creation Policies by Attacking
    Large Sets of Revealed Passwords" by Weir et al. (2010)
 3: "The science of guessing: analyzing an anonymized corpus of 70
    million passwords" by Joseph Bonneau

-- 
Regards,
Hubert Kario
Quality Engineer, QE BaseOS Security team
http://wiki.brq.redhat.com/hkario
Email: hk...@re...
Web: www.cz.redhat.com
Red Hat Czech s.r.o., Purkyňova 99/71, 612 45, Brno, Czech Republic

Re: [Cracklib-devel] Security baseline for cracklib (when passwords should be accepted or rejected?)

[Hubert K. <hk...@re...>]

Anyone?

I want do perform thorough testing of cracklib, but for that
I need to know what is the expected behaviour.

Now I see complex passwords rejected and simple passwords
accepted. Am I doing something wrong or could this be a bug
in cracklib?

Regards,
Hubert

----- Original Message -----
> From: "Hubert Kario" <hk...@re...>
> To: cra...@li...
> Cc: "Tomas Mraz" <tm...@re...>
> Sent: Tuesday, 10 September, 2013 6:51:01 PM
> Subject: [Cracklib-devel] Security baseline for cracklib (when passwords should be accepted or rejected?)
> 
> Hi all!
> 
> I've done some integration testing with cracklib and discovered
> that the passwords are rejected or accepted quite arbitrarily.
> At least I don't see any pattern in it.
> 
> For example, using English word list, password "1winning1" will
> be accepted as secure, but passwords ".):winning,!\" or
> "*~[winning#>;" will be rejected as insecure.
> 
> The word "winning" has about 10 bits of guessing entropy[1,2,3],
> so the above passwords have at most 16 (more realistically 12),
> 40 and 40 bits of guessing entropy respectively. That's a very
> large gap between false positive (IMO) and false negative.
> 
> What was the security level to be achieved? What is the
> acceptable error from this baseline?
> 
> NIST SP 800-63-1 allows for password based authentication with
> passwords that have 14 or 20 bits of entropy (for systems
> needing Level 1 or Level 2 security respectively). While making
> it possible to check if a password has more entropy than that
> would be nice, I think those two values would be a good starting
> point. So, I think that adding a configuration file that allows
> to set the desirable entropy of passwords would be a good new
> feature. Adding a new API that allows the programmer to specify
> the minimal amount of guessing entropy the password needs to
> have would be a good addition to that.
> 
>  1: NIST SP 800-63-1, section A.2.2
>  2: "Testing Metrics for Password Creation Policies by Attacking
>     Large Sets of Revealed Passwords" by Weir et al. (2010)
>  3: "The science of guessing: analyzing an anonymized corpus of 70
>     million passwords" by Joseph Bonneau
> 
> --
> Regards,
> Hubert Kario
> Quality Engineer, QE BaseOS Security team
> http://wiki.brq.redhat.com/hkario
> Email: hk...@re...
> Web: www.cz.redhat.com
> Red Hat Czech s.r.o., Purkyňova 99/71, 612 45, Brno, Czech Republic
> 
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-- 
Regards,
Hubert Kario
Quality Engineer, QE BaseOS Security team
http://wiki.brq.redhat.com/hkario
Email: hk...@re...
Web: www.cz.redhat.com
Red Hat Czech s.r.o., Purkyňova 99/71, 612 45, Brno, Czech Republic