Re: [quicwg/base-drafts] Rework Retry packet (#1498)

[Martin Thomson <[e-mail]>]

martinthomson commented on this pull request.



> +
+A server MUST only send a Retry in response to a client Initial packet.
+
+If the Original Destination Connection ID field does not match the Destination
+Connection ID from most recent the Initial packet it sent, clients MUST discard
+the packet.  This prevents an off-path attacker from injecting a Retry packet
+with a bogus new Source Connection ID.
+
+The client responds to a Retry packet with Initial packet that includes the
+provided Retry Token to continue connection establishment.
+
+A server that might send another Retry packet in response to a subsequent
+Initial packet MUST set the Source Connection ID to new value of at least 8
+octets in length.  This allows clients to distinguish between Retry packets when
+the server sends multiple rounds of Retry packets.  A server that will not send
+additional Retry packets can set the Source Connection ID to any value.

I thought that I caught that already.

ekr is right, if you send the first Initial with DCIL>=8 and the server respects this rule, then you will never ever get a Retry with ODCIL>=8.

mikkel, any value is correct.  The server can keep the old value if that suits it.

> @@ -731,12 +733,18 @@ If the client has a token received in a NEW_TOKEN frame on a previous connection
 to what it believes to be the same server, it can include that value in the
 Token field of its Initial packet.
 
-A client SHOULD NOT reuse a token.  Reusing a token on different network paths
-would allow activity to be linked between paths (see {{migration-linkability}}).
-A client MUST NOT reuse a token if it believes that its point of network
-attachment has changed; that is, if there is a change in its local IP address or
-network interface.  A client needs to start the connection process over if it
-migrates prior to completing the handshake.
+A token allows a server to correlate activity between connections.
+Specifically, the connection where the token was issued, and any connection
+where it is used.  Clients that want to break continuity of identity with a
+server MAY discard tokens provided using the NEW_TOKEN frame.  Tokens obtained
+in Retry packets MUST NOT be discarded.

Yes, the intent of this paragraph is to cover that.  The paragraph below is privacy-from-network.

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