Re: [TLS] New Cached info draft

Stefan Santesson <stefan@aaa-sec.com> Fri, 26 March 2010 00:36 UTC

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Date: Thu, 25 Mar 2010 17:36:42 -0700
From: Stefan Santesson <stefan@aaa-sec.com>
To: Adam Langley <agl@imperialviolet.org>
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Thread-Topic: [TLS] New Cached info draft
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Subject: Re: [TLS] New Cached info draft
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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