[Standards] XEP-0115 redux

[Peter Saint-Andre]

Justin Karneges wrote:
> On Thursday 10 January 2008 8:32 am, Peter Saint-Andre wrote:
>> The hashing algorithm matters because when you send me caps, I need to
>> verify the contents (i.e., the long string of identity+features that you
>> used as input to the hash function). The spec says:
>>
>>     The requesting entity MUST check the identities and supported
>>     features against the 'ver' value by calculating the hash as described
>>     under Generation of the ver Attribute and making sure that the values
>>     match.
>>
>> This helps me be sure that you're not poisoning the caps ecosystem. But
>> if you used SHA-384 to generate the hash and I don't support that
>> algorithm, then I can't verify the contents.
>>
>> Or so it seems to me. :)
> 
> In the case where you don't understand the hash algorithm, would it be enough 
> to simply cache the hash value on a per-jid basis and not bother verifying 
> it?  As I understand it, the only reason for the security discussion we're 
> having is because one jid is allowed to speak for another.  However, per-jid 
> caching is naturally secure and should be quite effective if your client has 
> a disk cache.

It's probably a good idea to have some text about what you do when you 
receive a caps notification using a hash you don't understand, but 
hopefully if we settle on a MTI algorithm that won't happen so often.

I'll do some wordsmithing on the text you provided, thanks.

Peter

-- 
Peter Saint-Andre
https://stpeter.im/

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