the foundation attribute is currently calculated as
CRC32(baseaddress, protocol, relayprotocol)
which is a way to satisfy the requirements from
https://www.rfc-editor.org/rfc/rfc5245#section-4.1.1.3
However, this leaks the base address which defeats the
MDNS obfuscation described in
https://datatracker.ietf.org/doc/draft-ietf-mmusic-mdns-ice-candidates/
since the CRC32 can be reversed using a table lookup as shown in
https://github.com/niespodd/webrtc-local-ip-leak/
To defeat that lookup, "seed" the CRC32 with the ICE tie-breaker which is a randomly picked unsigned 64 bit integer described in
https://www.rfc-editor.org/rfc/rfc5245#section-5.2
The tie-breaker is not known to Javascript and adding it scopes the foundation within the peer connection as described in section 4.1.1.3
To manually test (preferably with a DCHECK for IceTiebreaker() in ComputeFoundation)
- gather candidates twice on https://webrtc.github.io/samples/src/content/peerconnection/trickle-ice/ and observe that the foundations are not the same after this change
- create two RTCPeerConnections with {iceCandidatePoolSize: 1}, create a datachannel, call setLocalDescription, inspect the candidates and observe that the foundations are not the same after this change.
Unit test changes have been split into a separate CL for easier integration.
BUG=webrtc:14605
Change-Id: I6bbad1635b48997b00ae74d251ae357bf8afd12f
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/280621
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Reviewed-by: Jonas Oreland <jonaso@webrtc.org>
Commit-Queue: Harald Alvestrand <hta@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#38485}
08b882d762