oss-security - Re: CVE request: hs-tls: Basic constraints vulnerability

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Date: Wed, 30 Jan 2013 11:33:53 -0700
From: Kurt Seifried <kseifried@...hat.com>
To: oss-security@...ts.openwall.com
CC: Florian Weimer <fweimer@...hat.com>,
        Salvatore Bonaccorso <carnil@...ian.org>
Subject: Re: CVE request: hs-tls: Basic constraints vulnerability

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On 01/30/2013 03:59 AM, Florian Weimer wrote:
> On 01/20/2013 01:32 PM, Salvatore Bonaccorso wrote:
> 
>> For hs-tls (TLS/SSL implementation in haskell) it was announced
>> the following advisory[0]:
>> 
>> ----cut---------cut---------cut---------cut---------cut---------cut-----
>>
>> 
Hi cafe,
>> 
>> this is a security advisory for tls-extra < 0.6.1 which are all 
>> vulnerable to bad certificate validation.
>> 
>> Some part of the certificate validation procedure were missing 
>> (relying on the work-in-progress x509 v3 extensions), and because
>> of this anyone with a correct end-entity certificate can issue
>> certificate for any arbitrary domain, i.e. acting as a CA.
>> 
>> This problem has been fixed in tls-extra 0.6.1, and I advise
>> everyone to upgrade as soon as possible.
>> 
>> Despite a very serious flaw in the certificate validation, I'm
>> happy that the code is seeing some audits, and would want to
>> thanks Ertugrul S￶ylemez for the findings [1].
>> 
>> [1] https://github.com/vincenthz/hs-tls/issues/29 
>> ----cut---------cut---------cut---------cut---------cut---------cut-----
>
>> 
> I believe an alternative description of the impact is:
> hs-tls-extras does not check the Basic Constraints attribute of a
> certificate in certificate chain procession, and any certificate is
> treated as a CA certificate, which means that anyone who has a
> valid certificate can use it to sign another one (with an arbitrary
> subject DN/domain name embedded into it) and have it accepted by
> hs-tls.  This eventually allows MITM attacks on TLS connections.
> 
> Kurt, is this more to your liking? 8-)

Yup!

Please use CVE-2013-0243 for this issue.

- -- 
Kurt Seifried Red Hat Security Response Team (SRT)
PGP: 0x5E267993 A90B F995 7350 148F 66BF 7554 160D 4553 5E26 7993

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