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Pad path validation in both directions #4241

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merged 9 commits into from Oct 20, 2020
Merged

Pad path validation in both directions #4241

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c904daf
Pad when validating addresses
martinthomson Oct 16, 2020
d21c32b
A big caveat
martinthomson Oct 16, 2020
2686b0a
Datagrams, not packets
martinthomson Oct 16, 2020
b9bfce8
Revert automated formatting of tables, wrap
martinthomson Oct 16, 2020
b3ce9e6
Pad PATH_RESPONSE too
martinthomson Oct 19, 2020
663465c
Tweaks
martinthomson Oct 19, 2020
80cbb76
Wrap; make the other a SHOULD too
martinthomson Oct 19, 2020
abde090
Peer path validation...
martinthomson Oct 20, 2020
1e95cb2
MUST
martinthomson Oct 20, 2020
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26 changes: 20 additions & 6 deletions draft-ietf-quic-transport.md
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Expand Up @@ -2205,16 +2205,29 @@ connection.
The endpoint MUST use unpredictable data in every PATH_CHALLENGE frame so that
it can associate the peer's response with the corresponding PATH_CHALLENGE.

An endpoint MUST expand datagrams that contain a PATH_CHALLENGE frame to at
least the smallest allowed maximum datagram size of 1200 bytes. Sending UDP
datagrams of this size ensures that the network path from the endpoint to the
peer can be used for QUIC; see {{datagram-size}}.


### Path Validation Responses

On receiving a PATH_CHALLENGE frame, an endpoint MUST respond by echoing the
data contained in the PATH_CHALLENGE frame in a PATH_RESPONSE frame. A
PATH_RESPONSE frame does not need to be sent on the network path where the
PATH_CHALLENGE was received; a PATH_RESPONSE can be sent on any network path.
An endpoint MUST NOT delay transmission of a packet containing a PATH_RESPONSE
data contained in the PATH_CHALLENGE frame in a PATH_RESPONSE frame. An
endpoint MUST NOT delay transmission of a packet containing a PATH_RESPONSE
frame unless constrained by congestion control.

A PATH_RESPONSE frame MUST be sent on the network path where the
PATH_CHALLENGE was received. This ensures that path validation by a peer only
succeeds if the path is functional in both directions. This requirement MUST
NOT be enforced by the endpoint that initiates path validation as that would
enable an attack on migration; see {{off-path-forward}}.

An endpoint MUST expand datagrams that contain a PATH_RESPONSE frame to at
least the smallest allowed maximum datagram size of 1200 bytes. This verifies
that the path is able to carry datagrams of this size in both directions.

An endpoint MUST NOT send more than one PATH_RESPONSE frame in response to one
PATH_CHALLENGE frame; see {{retransmission-of-information}}. The peer is
expected to send more PATH_CHALLENGE frames as necessary to evoke additional
Expand All @@ -2224,8 +2237,9 @@ PATH_RESPONSE frames.
### Successful Path Validation

Path validation succeeds when a PATH_RESPONSE frame is received that contains
the data that was sent in a previous PATH_CHALLENGE frame. This validates the
path on which the PATH_CHALLENGE was sent.
the data that was sent in a previous PATH_CHALLENGE frame. A PATH_RESPONSE
frame received on any network path validates the path on which the
PATH_CHALLENGE was sent.
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I guess it actually only validates one direction of that path but I guess that nit picking...


Receipt of an acknowledgment for a packet containing a PATH_CHALLENGE frame is
not adequate validation, since the acknowledgment can be spoofed by a malicious
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