"No-Keyserver" (and other) flags on keys

[Dan Mahoney, System Admin]

On Sun, 27 Jun 2010, David Shaw wrote:

> On Jun 27, 2010, at 7:50 PM, Dan Mahoney, System Admin wrote:
>
>>>>> It's effectively a no-op though, as no server supports it.
>>>>
>>>> I'm looking into making mods to at least one server type (we run one 
>>>> locally at work), and commit them upstream.  If I'm going to wade 
>>>> into that muck, I might as well have multiple things to try to make 
>>>> work.
>>>>
>>>> The change in the key file format is the "hard" part :)
>>>
>>> Having keyservers support no-modify requires that they first support 
>>> crypto at all.  That's a really big step.
>>
>> The ones I've seen have enough awareness of what's in a key to pull a 
>> key apart and determine who's signed it, when, and when it's expired. 
>> Is there more than that to read these bits?  Again:step zero may be to 
>> determine what the internal format is.
>
> Vastly more.  Keyservers are basically databases with a front-end that 
> understands the OpenPGP key format.  They don't actually do any crypto 
> math - just storing the key packets in the database and allowing people 
> to search for them.
>
>> However, you raise another question: How does a keyserver know who is 
>> uploading the key?
>
> At the moment, it doesn't.  That would need to be addressed if you want 
> keyservers to be able to reject a no-ks-modify key.  One way to do it is 
> to only accept key updates that are signed by the key itself.  But, of 
> course, to do that, the keyserver needs to be able to verify a 
> signature...

That's one way.  Another is to do it the keyserver.pgp.com way, and email 
the primary uid a cookie.  No crypto required.  RFC2440 doesn't at all 
require that the authenticity be verified cryptographically.  Correct?

While we're at this, do the various keyserver client-implementations 
provide any option for passing a human-readable message back to gpg? I 
don't see anything in draft-shaw-openpgp-hkp-00, but that's long expired 
(but good reading).

>From what you're telling me, it also sounds like keyservers don't actually 
verify the signatures that are on a key, and that's left up to the client.

However, I think you're still missing my question: is it necessary for the 
keyserver to be crypto-aware if I just want a keyserver to reject those 
keys outright?  Is there crypto involved in reading that flag, or is it 
just a simple parse?  From reading RFC2440 it seems the latter, but I 
certainly respect you've been doing this longer than I :)

-Dan

-- 

--------Dan Mahoney--------
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