[openssl-dev] [openssl.org #4080] Malformed Client Hello messages are accepted (session_id length)

[Viktor Dukhovni]

On Thu, Oct 08, 2015 at 04:12:50PM +0000, Hubert Kario via RT wrote:

> The server does not abort connection upon receiving a Client Hello 
> message with malformed session_id field.
> 
> Affects 1.0.1, 1.0.2 and master.
> 
> In SSLv3 and all versions of TLS (e.g. RFC 5246), the SessionID is 
> defined as
> 
>       opaque SessionID<0..32>;
>
> that means, that any SessionID longer than 32 bytes creates an 
> incorrectly formatted Client Hello message, and as such, should be 
> rejected.

Can be rejected, and perhaps even should be rejected, but I don't
see a MUST here.  It seems there's little harm in tolerating longer
session ids (which never match, so are effectively ignored).

So yes, I support adding a check for this (likely above the PACKET
layer), but I don't think this has much urgency and likely should
not be back-ported to stable releases.

-- 
	Viktor.