Re: [Enigmail] Future OpenPGP Support in Thunderbird

Werner Koch <[email protected]> Wed, 30 Oct 2019 10:29:26 +0100

Newsgroups	gmane.comp.mozilla.enigmail.general
Message-ID	<[email protected]>

On Tue, 29 Oct 2019 18:18, Daniel Kahn Gillmor said:

>> You can't.  Neither can a webbroweser avoid downloading huge images or
>> other stuff from stupid web pages.
>
> i think the idea that there's no defense against malicious input is
> rather defeatist.  There are plenty of counterexamples, where small

I was talking about the complaint that GnuPG takes up a lot of
"bandwidth" by first downloading a large keyblock and may only then
discard the entire keyblock.  The structure of an OpenPGP keyblock does
in general not allow to process and evaluate it in small chunks during
the download.  Thus downloading the entire keyblock is necessary.  I am
all in favor of having a limit on the client side but it would be better
if keyservers don't send all the data they once acquired.

Sure we could abort the download after a certain amount of data has been
received.  But then again, what limit do we want and how do we handle,
for example, valid revocations inside that keyblock.  The concept of
serving entire keyblocks is thus questionable.  I mentioned this some
time ago: We have a very similar problem with CRLs where a single slow
CRL server can grind the entire mail sending process.

> These small defenses add up, and we should be encouraging more of them,
> rather than dismissing work on input validation as impossible.

What we do is to source out fixing of bogus keyblocks to the client
instead of simply rejecting them.  The server is in a way better
position to fix up keyblocks.


Shalom-Salam,

   Werner

-- 
Die Gedanken sind frei.  Ausnahmen regelt ein Bundesgesetz.

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