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Server selects a key exchange group the client never offered

Abort with illegal_parameter. §4.1.3 is explicit that if the selected group was not offered, the client MUST abort — accepting it would let a server steer a client onto a group it deliberately excluded. The port names secp384r1 in its ServerHello against a client that offered only the hybrid, and leaves the payload exactly as generated: the only thing wrong is the name, so a client that aborts can only be aborting over §4.1.3 and not over a share it could not parse. What is judged is the abort, not the alert value. RFC 9001 §4.8 lets a QUIC endpoint replace any alert with a generic one — handshake_failure in place of illegal_parameter — expressly so that a client need not say what it objected to, so the code a client chooses is reported here and not scored. A handshake that ends without any CONNECTION_CLOSE is inconclusive rather than a failure: the group was certainly not accepted, but a close that was never sent cannot be told from one that was lost.

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t-group-not-offered · RFC 8446 §4.1.3, §4.2.8, RFC 9001 §4.8 · correctness · layer tls · udp/4514 · MUST

Passing this means: Rejected something invalid, with the code the RFC names.

Anomaly type: transport

How each client answered

ClientVersionVerdictWhat happened
curl ngtcp2/1.11.0 Not run Not attempted.
quinn noq fork Inconclusive The handshake did not complete, so the group was not accepted, but nothing arrived to say the client rejected it deliberately. RFC 9001 §4.8 carries a TLS alert in a CONNECTION_CLOSE and none was seen; a close that was never sent and one that was lost look the same from here.
aioquic 1.3.0 Not run Not attempted.
chromium build 1223 Pass Responded correctly: aborted with illegal_parameter (alert 47) over a key_share naming a group it never offered, which is exactly what RFC 8446 §4.1.3 requires.
quic-go quic-go v0.61.0 Pass Responded correctly: aborted with illegal_parameter (alert 47) over a key_share naming a group it never offered, which is exactly what RFC 8446 §4.1.3 requires.
quiche 0.30.0 Pass Responded correctly: aborted with illegal_parameter (alert 47) over a key_share naming a group it never offered, which is exactly what RFC 8446 §4.1.3 requires.
neqo 0.31.1 Pass Responded correctly: aborted with illegal_parameter (alert 47) over a key_share naming a group it never offered, which is exactly what RFC 8446 §4.1.3 requires.

What the clause requires

Abort with illegal_parameter. §4.1.3 is explicit that if the selected group was not offered, the client MUST abort — accepting it would let a server steer a client onto a group it deliberately excluded. The port names secp384r1 in its ServerHello against a client that offered only the hybrid, and leaves the payload exactly as generated: the only thing wrong is the name, so a client that aborts can only be aborting over §4.1.3 and not over a share it could not parse. What is judged is the abort, not the alert value. RFC 9001 §4.8 lets a QUIC endpoint replace any alert with a generic one — handshake_failure in place of illegal_parameter — expressly so that a client need not say what it objected to, so the code a client chooses is reported here and not scored. A handshake that ends without any CONNECTION_CLOSE is inconclusive rather than a failure: the group was certainly not accepted, but a close that was never sent cannot be told from one that was lost.

Judged against RFC 8446, RFC 9001.

Run this one yourself

Every test is reachable from your own client. Nothing here needs an account.

curl -s https://conformance.pqcrypta.com/catalog.json \
  | jq '.tests[] | select(.id == "t-group-not-offered")'

What this suite is · The full grid · All clients · All tests · Findings