Re: [TLS] New Cached info draft

Marsh Ray <marsh@extendedsubset.com> Wed, 31 March 2010 20:13 UTC

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Date: Wed, 31 Mar 2010 15:14:27 -0500
From: Marsh Ray <marsh@extendedsubset.com>
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Subject: Re: [TLS] New Cached info draft
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On 3/31/2010 2:47 PM, Martin Rex wrote:
> Brian Smith wrote:
>>
>> Marsh Ray wrote:
>>>
>>> I think in this case it's saying there can be a maximum of 1024
>>> entries in the list, each of which can take up to 9 bytes
>>> (with a one byte length). So the receiver of this structure
>>> is only obligated to store (or ignore) (2 + (1 + 8)*1024)
>>> bytes of data.
>>
>> No, Mike is right and I was wrong; <1024> means "1024 bytes",
>> not "1024 entries".
> 
> While Marsh explanation sounded quite reasonable to me,
> the implementors have a technical advantage of being more
> accustomed to the TLS spec syntax for defining a vector size:
> 
> http://tools.ietf.org/html/rfc5246#section-4.3

It says:
>    The length of
>    an encoded vector must be an even multiple of the length of a single
>    element (for example, a 17-byte vector of uint16 would be illegal).

This requirement does not seem to allow a vector to be made up of
variable-sized elements as in Stefan's suggestion.

On 3/31/2010 4:42 AM, Stefan Santesson wrote:
>
>       struct {
>            CachedInformationType type;
>            opaque digest_value<0..8>;
>       } CachedObject;
>
>       struct {
>            CachedObject cached_info<1..1024>;
>       } CachedInformation;

So perhaps some other notation is needed for this class of structure?

On 3/31/2010 10:52 AM, Michael D'Errico wrote:
>
> This idea has buffer overflow written all over it.

Now I'm inclined to agree!

There are something like four potentially contradictory byte lengths in
play.

- Marsh