Re: [TLS] Cached-info substitution

Wan-Teh Chang <wtc@google.com> Fri, 19 February 2010 21:47 UTC

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References: <4B7D8AAD.80204@briansmith.org> <C7A4666D.8663%stefan@aaa-sec.com>
Date: Fri, 19 Feb 2010 13:48:51 -0800
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From: Wan-Teh Chang <wtc@google.com>
To: Stefan Santesson <stefan@aaa-sec.com>
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Cc: tls@ietf.org
Subject: Re: [TLS] Cached-info substitution
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On Fri, Feb 19, 2010 at 7:01 AM, Stefan Santesson <stefan@aaa-sec.com>; wrote:
>
> As I see it we have two choices.
>
> 1) To define a format for the handshake message which include the hash
> substitution using a syntax that alters the defined syntax of the handshake
> message. (current draft approach)
>
> 2) To define a format which preserves the original handshake message syntax.
>
>
> In practice this would look something like this:
>
>
> Certificate handshake message:
>
> Original syntax:
>      opaque ASN.1Cert<1..2^24-1>;
>
>      struct {
>          ASN.1Cert certificate_list<0..2^24-1>;
>      } Certificate;
>
>
> Substitution syntax, choice 1 (current draft):
>      struct {
>          CachedInformationHash certificate_list<0..2^24-1>;
>      } Certificate;
>
>
> Substitution syntax, choice 2 (preserving original syntax):
>      CachedInformationHash CachedCertList<1..2^24-1>;
>
>      struct {
>          CachedCertList certificate_list<0..2^24-1>;
>      } Certificate;

In choice 2, did you mean CachedCertList or CachedCert?
With CachedCertList, the Certificate message would contain
a list of lists of certificates.

In choice 2, how does a decoder distinguish between 'opaque' and
CachedInformationHash?  Is it supposed to "sniff" the first few
bytes to see whether it looks like an ASN.1 DER encoded cert?

Wan-Teh