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Re: [TLS] Certificate validation can of worms

mrex@sap.com (Martin Rex) Mon, 07 April 2014 20:31 UTC

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To: Nico Williams <nico@cryptonector.com>
Date: Mon, 07 Apr 2014 22:31:31 +0200
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From: mrex@sap.com
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Subject: Re: [TLS] Certificate validation can of worms
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Nico Williams wrote:
>>
>> The research you linked didn't deal with naming.  That doesn't mean
>> naming isn't a problem for PKI.  You asked, I answered :)
> 
> Er, no, it did deal with naming.  Search for "name constraint"; it's
> mentioned quite a few times.  Several TLS libraries don't implement PKIX
> name constraints at all.  Embarrassing.

This is not embarrassing at all.
Name constraints are *OPTIONAL* to implement.

What is embarrassing is an implementation of PKI & CA software that will
happily created cert chains with bogus name constraints in them.

A while ago I had been given a certificate chain with a huge amounts
of name constraints in them.  Some of the name constraints were bogus
(syntactically invalid), and there was a set of name constraints included
for which no public specification of the subjectAltName (otherName),
let alone the definition of name constraints format and processing for
that proprietary nametype.  


-Martin

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