[openssl-dev] [openssl.org #4119] DTLS resets handshake hash too frequently for ClientHello

[Matt Caswell via RT]

On 03/11/15 17:43, David Benjamin via RT wrote:

> I'm not sure that fix quite works though. If BIO_flush completes
> asynchronously

Ahhh, yes good point. Updated patch attached.

> (hrm, it's missing an rwstate update),

Yes, just discovered that myself and then came back and reread your
email to find out you already pointed it out! Also addressed in updated
patch.


> then I believe you'll
> be in a state where you *do* want to repeat the init_off / init_num adjust.
> You might be able to get away with using init_off/init_num with some minor
> tweaks? Another problem: because the fragment headers clobber whatever was
> already written, msg_callback sees garbage.

Yuck. Not addressed that issue yet. I'll deal with that separately.

> Yeah, this part of DTLS (like much of it) is woefully underspecified. We
> keep stuffing things into ClientHellos, so if one does need to support
> fragmented ones, I think the right way to do stateless HelloVerifyRequest
> is to silently drop all non-initial ClientHello fragments and require the
> initial one be large enough to include the client_random and whatever else
> you figure into the cookie.

I really like that idea. I'll take a look at doing that in the new
DTLSv1_listen code.

Matt


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