Re: [TLS] About the contents of Record Layers

[Juho Vähä-Herttua <[e-mail]>]

On 1.8.2010, at 18.08, JCA wrote:
> Does the TLS 1.* specs allow to send a Record Layer with an empty
> body? That is, a Record Layer containing only the protocol ID, version
> and length fields? I don't see why would anyone want to do that but,
> is it legal?

The specification seems to be quite clear about this, in TLS 1.0:

6.2.  Record Layer

   The TLS record layer receives uninterpreted data from higher layers
   in non-empty blocks of arbitrary size.

...and clarified in TLS 1.2...

   Implementations MUST NOT send zero-length fragments of Handshake,
   Alert, or ChangeCipherSpec content types.  Zero-length fragments of
   Application data MAY be sent as they are potentially useful as a
   traffic analysis countermeasure.

So in case of application data they can be sent, in reality I would do serious testing with existing implementations to see how they behave. If they are TLS 1.2 compliant and negotiate a TLS 1.2 connection they should all accept the empty records though.


Juho