Re: [quicwg/base-drafts] Add retry integrity tag (#3120)

[Christian Huitema <[e-mail]>]

huitema commented on this pull request.



> +The Retry Pseudo-Packet is not sent over the wire. It is computed by taking
+the transmitted Retry packet, removing the Retry Integrity Tag and prepending
+the two following fields:
+
+ODCID Len:
+
+: The ODCID Len contains the length in bytes of the Original Destination
+  Connection ID field that follows it, encoded as an 8-bit unsigned integer.
+
+Original Destination Connection ID:
+
+: The Original Destination Connection ID contains the value of the Destination
+  Connection ID from the Initial packet that this Retry is in response to. The
+  length of this field is given in ODCID Len. The presence of this field
+  mitigates an off-path attacker's ability to inject a Retry packet.
+

Overselling! If the off-path attacker has a copy of the original Initial packet sent by the client, then it knows the ODCID. I don't see how appending a checksum will change that.

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