Commit 65907a43 authored Jun 11, 2008 by Gerrit Renker

dccp ccid-2: Bug-Fix - Ack Vectors need to be ignored on request sockets

This fixes an oversight from an earlier patch, ensuring that Ack Vectors
are not processed on request sockets.

The issue is that Ack Vectors must not be parsed on request sockets, since
the Ack Vector feature depends on the selection of the (TX) CCID. During the
initial handshake the CCIDs are undefined, and so RFC 4340, 10.3 applies:

"Using CCID-specific options and feature options during a negotiation
for the corresponding CCID feature is NOT RECOMMENDED [...]"

And it is not even possible: when the server receives the Request from the
client, the CCID and Ack vector features are undefined; when the Ack finalising
the 3-way hanshake arrives, the request socket has not been cloned yet into a
full socket. (This order is necessary, since otherwise the newly created socket
would have to be destroyed whenever an option error occurred - a malicious
hacker could simply send garbage options and exploit this.)

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>

parent 1e2f0e5e

net/dccp/options.c

+3 −1

Original line number	Diff line number	Diff line
		@@ -107,9 +107,11 @@ int dccp_parse_options(struct sock sk, struct dccp_request_sock dreq,
		*
		* CCID-specific options are ignored during connection setup, as
		* negotiation may still be in progress (see RFC 4340, 10.3).
		* The same applies to Ack Vectors, as these depend on the CCID.
		*
		*/
		if (dreq != NULL && opt >= 128)
		if (dreq != NULL && (opt >= 128 \|\|
		opt == DCCPO_ACK_VECTOR_0 \|\| opt == DCCPO_ACK_VECTOR_1))
		goto ignore_option;

		switch (opt) {

Admin message