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From Dr Stephen Henson <shen...@oss-institute.org>
Subject Re: [PATCH] mod_ssl: improving session caching for SNI configurations
Date Sat, 07 Nov 2009 17:35:39 GMT
Kaspar Brand wrote:
> Dr Stephen Henson wrote:
>> A few comments about that:
> 
> Thanks for the review!
> 
>> These are cryptographic keys (or at least the HMAC and AES keys are) so you
>> should use RAND_bytes(), not RAND_pseudo_bytes().
> 
> Ok - when looking at ssl_lib.c:SSL_CTX_new(), I didn't realize that
> RAND_pseudo_bytes() is only used for tlsext_tick_key_name. Changed
> accordingly.
> 
>> Don't dereference the structures directly as at some point the sizes might
>> change, the structure made opaque or a different mechanism used for storing keys
>> (e.g. HSM support).
> 
> I was looking at a way to determine the size at compile time, but if you
> think that's an unsafe method (note: it's only expected to work for
> 0.9.8f through 0.9.8l), then let's change it.
> 

These things have a habit of persisting far longer than their expected lifetime ;-)

>> The approved way is to call:
>>
>> SSL_CTX_set_tlsext_ticket_keys(sc->server->ssl_ctx, NULL, -1)
>>
>> which will return the combined length of all keys.
> 
> Did that - does v3 of the patch (attached) look better? Is it ok to use
> apr_palloc here?
> 

Yes that looks better. There is an alternative technique if it is easier to find
a "base" SSL_CTX, you can retrieve the auto generated keys using
SSL_CTX_get_tlsext_ticket_keys() and then copy to the new context as above.

Steve.
-- 
Dr Stephen N. Henson. Senior Technical/Cryptography Advisor,
Open Source Software Institute: www.oss-institute.org
OpenSSL Core team: www.openssl.org

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