Date: Wed, 30 Jan 2013 11:59:59 +0100 From: Florian Weimer <fweimer@...hat.com> To: oss-security@...ts.openwall.com CC: Salvatore Bonaccorso <carnil@...ian.org> Subject: Re: CVE request: hs-tls: Basic constraints vulnerability On 01/20/2013 01:32 PM, Salvatore Bonaccorso wrote: > For hs-tls (TLS/SSL implementation in haskell) it was announced the following > advisory: > > ----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 Söylemez for the > findings . > >  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-) -- Florian Weimer / Red Hat Product Security Team
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