Re: [TLS] New Cached info draft

Stefan Santesson <stefan@aaa-sec.com> Fri, 26 March 2010 14:49 UTC

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Date: Fri, 26 Mar 2010 07:36:07 -0700
From: Stefan Santesson <stefan@aaa-sec.com>
To: Stefan Santesson <stefan@aaa-sec.com>, Adam Langley <agl@imperialviolet.org>
Message-ID: <C7D21467.99E0%stefan@aaa-sec.com>
Thread-Topic: [TLS] New Cached info draft
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Subject: Re: [TLS] New Cached info draft
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I have submitted a 05 version of cached info draft that fixes the recorded
errors and problems.

http://tools.ietf.org/rfcdiff?url2=draft-ietf-tls-cached-info-05.txt

/Stefan

On 10-03-25 5:36 PM, "Stefan Santesson" <stefan@aaa-sec.com>; wrote:

> Thanks for the review Adam,
> 
> Comments in line;
> 
> 
> On 10-03-25 4:21 PM, "Adam Langley" <agl@imperialviolet.org>; wrote:
> 
>> On Thu, Mar 25, 2010 at 10:55 AM, Stefan Santesson <stefan@aaa-sec.com>;
>> wrote:
>>> Major changes:
>>> - The 64 bit FNV-1 non-cryptographic hash is used to provide a digest over
>>> cached data. All use of hash algorithms has been removed, so also all
>>> elements of hash algorithm agility. The FNV-1 digest algorithm used in this
>>> specification is defined in Annex A.
>>> 
>>> - It is now possible to query a server with an empty cached info extension
>>> to find out if, and to what extent the server supports caching before the
>>> client starts to cache data for that server.
>>> 
>>> - The data substitution syntax has been explicitly defined for both defined
>>> object types
>> 
>> I knocked up patches for NSS (client and server) and for OpenSSL
>> (server only) for this. (Available on request if anyone cares although
>> the quality is currently "quick-hack").
>> 
>> One issue that I ran into: the representation of the FNV64 hash on the
>> wire is unspecified. I assumed big-endian but it should be in the
>> spec.
>> 
> 
> Agree, It is big-endian and text is added.
> 
>> I think there's a typo in the first line of section 5.1 (it mentioned
>> trusted_cas when I think it should be certificate_chain)
>> 
> 
> Fixed.
> 
>> There are two section 5s.
>> 
> 
> Fixed.
> 
>> Also, does a "digest calculated over the certificate_list element of a
>> server side Certificate message" contain the three length bytes? I
>> assumed not. To be clear, a certificate_list is prefixed with three
>> length bytes and contains a series of certificate, each of which has
>> its own three length bytes. It seems clear the the length bytes of the
>> certificates should be included, but I omitted the initial three.
>> 
> 
> Good question. This makes me realize that I have made an error in version 04
> since I have removed the inner 3 byte length for the substitution syntax.
> 
> 
> The correct syntax should be:
> 
> DigestInfo ASN.1Cert<1..2^24-1>;
> 
> struct {
>     opaque digest_value<0..8>;
> } DigestInfo;
> 
> struct {
>     ASN.1Cert certificate_list<0..2^24-1>;
> } Certificate;
> 
> 
> The spec intended to specify that the whole certificate_list vector was
> hashed, including the length bytes, but it makes absolutely sense to exclude
> hashing the length bytes of the certificate_list vector.
> 
> I can clarify this if the list approves.
> 
> /Stefan
> 
>  
> 
> 
>> 
>> Cheers
>> 
>> AGL
> 
> 
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