The issue is that the "TLSCiphertext.length" is the same field as
the "uint16 length", so you are saying that this field has the value
of "cid_length plus itself", which is impossible in integers modulo
[a value larger than cid_length]. In the "formal" grammar, you'd
need to define a new field.
-Ben
On Tue, Mar 20, 2018 at 11:45:59PM +0000, John Mattsson wrote:
> Correct, I just copied pasted the length of the arrays, should be length =
> cid_length + encrypted_record.length.
>
> The example was taken from draft-ietf-tls-tls13-27. If I understand
> correctly, It seems like the same circular definition is done there as
> well....
>
> -----------------------------------------------------
> struct {
> ContentType opaque_type = application_data; /* 23 */
> ProtocolVersion legacy_record_version = 0x0303; /* TLS v1.2 */
> uint16 length;
> opaque encrypted_record[TLSCiphertext.length];
> } TLSCiphertext;
> -----------------------------------------------------
>
> Shouldn't this be...
>
> -----------------------------------------------------
> struct {
> ContentType opaque_type = application_data; /* 23 */
> ProtocolVersion legacy_record_version = 0x0303; /* TLS v1.2 */
> uint16 length;
> opaque encrypted_record[encrypted_record.length];
> } TLSCiphertext;
> -----------------------------------------------------
>
> Does this mean the
> On 2018-03-20, 19:29, "Stephen Checkoway" <s...@pahtak.org> wrote:
>
>
>
> > On Mar 20, 2018, at 11:38, John Mattsson <john.matts...@ericsson.com>
> wrote:
> >
> > I think Connection ID is an important enabler for end-to-end security
> with (D)TLS. There seems to be important use cases for connection ID in TLS
> as well, see https://www.ietf.org/mailman/listinfo/atlas. At the Monday
> afternoon TLS session, it was stated that Connection ID in TLS was
> unemployable in the wild due to middleboxes. Couldn't that be solved by
> placing the cid field after the length field? E.g.
> >
> > struct {
> > ContentType opaque_type = application_data; /* 23 */
> > ProtocolVersion legacy_record_version = 0x0303; /* TLS v1.2 */
> > uint16 length;
> > opaque cid[cid_length]; // New field
> > opaque encrypted_record[TLSCiphertext.length];
> > } TLSCiphertext;
> >
> > length The sum of cid_length and TLSCiphertext.length
>
> This defines length in terms of itself since length is
> TLSCiphertext.length.
>
> --
> Stephen Checkoway
>
>
>
>
>
>
>
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