[OpenAFS-devel] [FYI] Review of http://k5wiki.kerberos.org/wiki/Projects/Disable_DES ending February 13, 2009

[Sam Hartman]

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Folks, I wanted to draw the attention of the AFS development community to a proposal under review
within the MIT Kerberos development community.
Comments on this proposal should be sent to krbdev@mit.edu.

The basic goal is to remove single DES from MIT Kerberos.  That makes
sense for security reasons.  It also makes using AFS rather difficult.
There are a lot of different things it could mean to disable DES, some
of them requiring more twiddling to deal with AFS than others.  I
think it would be great to make sure AFS developers are involved in
the discussion to help balance the security vs usability tradeoff.


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Topics:
   Review of http://k5wiki.kerberos.org/wiki/Projects/Disable_DES ending  February 13, 2009
   Re: Review of http://k5wiki.kerberos.org/wiki/Projects/Disable_DES  ending February 13, 2009

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Date: Wed, 28 Jan 2009 21:16:18 -0500
From: Tom Yu <tlyu@MIT.EDU>
To: krbdev@MIT.EDU
Subject: Review of http://k5wiki.kerberos.org/wiki/Projects/Disable_DES ending  February 13, 2009
Message-ID: <ldvpri67t71.fsf@cathode-dark-space.mit.edu>
MIME-Version: 1.0

Please review the project
    http://k5wiki.kerberos.org/wiki/Projects/Disable_DES

The review period ends on February 13, 2009.

This project aims to disable single-DES cryptosystems by default.  The
"allow_weak_crypto" libdefaults setting (which is compatible with
Heimdal) will override this disabling.  Note that a more general means
of configuring enctypes, allowing for explicit inclusions and
exclusions, is out of scope for this project for time reasons but is
clearly a better way to accomplish this functionality.

An initial implementation is already committed to the trunk.

-- 
Tom Yu
Development Team Leader
MIT Kerberos Consortium
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Date: Thu, 29 Jan 2009 10:17:48 -0500
From: Sam Hartman <hartmans@MIT.EDU>
To: Tom Yu <tlyu@MIT.EDU>
Cc: krbdev@MIT.EDU
Subject: Re: Review of http://k5wiki.kerberos.org/wiki/Projects/Disable_DES  ending February 13, 2009
Message-ID: <tslzlhaw38j.fsf@live.mit.edu>
References: <ldvpri67t71.fsf@cathode-dark-space.mit.edu>
MIME-Version: 1.0

Tom, I have a couple of concerns here.

First, I don't understand what the use case is or functional
requirements are.

I mean we all know that we'd like to stop using DES.  However I'd like
to understand the drivers for this to understand what the right
functionality is?


The main questions I have that would be answered by functional
requirements surround  what the security/interoperability tradeoff is.

For example, much of the value of disabling DES could be accomplished
by disabling DES at the KDC.  If the KDC does not issue tickets keyed
with DES or using DES as a session key, then for the most part clients
and servers will not use DES.  ((Clients may still try to use DES for
string2key).


Also, the current project write up does not describe how the
krb5_c_weak_enctype will be used.  If we're planning on moving to
something like permitted_enctypes = default - des then shouldn't that
be krb5int_c_weak_enctype instead?


I suspect I'll have additional questions once these are answered.
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