On Thu, Sep 22, 2011 at 7:55 PM, Roger Dingledine <[email protected]> wrote: > On Tue, Sep 20, 2011 at 03:33:42PM -0400, Nick Mathewson wrote: >> Design: Indicating variable-length cells. >> >> Beginning with the v3 link protocol, we specify that all cell >> types in the range 128..255 indicate variable-length cells. >> Cell types in the range 0..127 are still used for 512-byte >> cells, except that the VERSIONS cell type (7) also indicates a >> variable-length cell (for backward compatibility). >> >> As before, all Tor instances must ignore cells with types that >> they don't recognize. > > Sounds good. > >> Design: Variable-length padding. >> >> We add a new variable-length cell type, "VPADDING", to be used for >> padding. All Tor instances may send a DROP cell at any point that >> a VERSIONS cell is not required; a VPADDING cell's body may be any >> length; the body of a VPADDING cell MAY have any content. Upon >> receiving a VPADDING cell, the recipient should drop it, as with a >> PADDING cell. > > Also sounds fine. But to clarify, did you mean to talk about a DROP cell > in one of those sentences? I think you meant to say VPADDING there?
Yup; will fix. > Also to be clear, there's no way to send a variable-length padding > cell that's less than 5 bytes, right? I don't imagine that will bite us > immediately, but we should call it out as a known constraint. Correct. I'll add a note. > By "the body of a vpadding cell may have any content", did you have in > mind to randomize it to help protect against future TLS gotchas? Or just > to leave us the option to do so in the future? Both, but I think "randomize it now" is the answer. I'll add a note. -- Nick _______________________________________________ tor-dev mailing list [email protected] https://lists.torproject.org/cgi-bin/mailman/listinfo/tor-dev
