Re: [quicwg/base-drafts] Allow Smaller Stateless Resets (#2927)

[David Schinazi <[e-mail]>]

DavidSchinazi commented on this pull request.



> @@ -2389,19 +2389,26 @@ of bytes following it that are set to unpredictable values.  The last 16 bytes
 of the datagram contain a Stateless Reset Token.
 
 To entities other than its intended recipient, a stateless reset will appear
-to be a packet with a short header.  For the packet to appear as valid, the
-Unpredictable Bits field needs to include at least 198 bits of data (or 25
-bytes, less the two fixed bits).  This is intended to allow for a Destination
-Connection ID of the maximum length permitted, with a minimal packet number, and
-payload.  The Stateless Reset Token corresponds to the minimum expansion of the
+to be a packet with a short header.  For the stateless reset to appear as a
+valid QUIC packet and be smaller than the received packet, the Unpredictable
+Bits field needs to include at least 46 bits of data (or 6 bytes, less the
+two fixed bits), because packets that are smaller than 21 bytes are never
+valid.  To ensure the stateless reset packet is not smaller than other
+packets received on the connection, the an endpoint SHOULD also ensure the

typo: the an

> @@ -2389,19 +2389,26 @@ of bytes following it that are set to unpredictable values.  The last 16 bytes
 of the datagram contain a Stateless Reset Token.
 
 To entities other than its intended recipient, a stateless reset will appear
-to be a packet with a short header.  For the packet to appear as valid, the
-Unpredictable Bits field needs to include at least 198 bits of data (or 25
-bytes, less the two fixed bits).  This is intended to allow for a Destination
-Connection ID of the maximum length permitted, with a minimal packet number, and
-payload.  The Stateless Reset Token corresponds to the minimum expansion of the
+to be a packet with a short header.  For the stateless reset to appear as a
+valid QUIC packet and be smaller than the received packet, the Unpredictable
+Bits field needs to include at least 46 bits of data (or 6 bytes, less the
+two fixed bits), because packets that are smaller than 21 bytes are never
+valid.  To ensure the stateless reset packet is not smaller than other
+packets received on the connection, the an endpoint SHOULD also ensure the
+total packet length is at least the minimum chosen CID length + 19 bytes.
+19 bytes allows for 1 type byte, 1 data byte, the 16 byte authentication

The invariant we have is `payload_length + packet_number_length >= 4` to which you add type byte (1) and auth tag (16) to get 1 + 4 + 16 = 21. I think we want 22 + chosen CID length

>  packet protection AEAD.  More unpredictable bytes might be necessary if the
 endpoint could have negotiated a packet protection scheme with a larger minimum
 AEAD expansion.
 
 An endpoint SHOULD NOT send a stateless reset that is significantly larger than
 the packet it receives.  Endpoints MUST discard packets that are too small to be
 valid QUIC packets.  With the set of AEAD functions defined in {{QUIC-TLS}},
-packets that are smaller than 21 bytes are never valid.
+packets that are smaller than 21 bytes are never valid.  When a packet is b

was this intentional?

-- 
You are receiving this because you are subscribed to this thread.
Reply to this email directly or view it on GitHub:
https://github.com/quicwg/base-drafts/pull/2927#pullrequestreview-265410787