feat: include channel-binding data in SCRAM proofs - #6
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AuthMessage c= is base64(gs2-header || cbind-data) when the GS2 flag is p. Without that, SCRAM-SHA-256-PLUS clients fail even when the header parses. Also add a PLUS client and reject the RFC 5802 y downgrade. Co-authored-by: Cursor <cursoragent@cursor.com>
This was referenced Aug 31, 2026
Rejecting n is this server's require-channel-binding policy, not a section 6 MUST. Co-authored-by: Cursor <cursoragent@cursor.com>
levkk
approved these changes
Aug 31, 2026
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Summary
c=is nowbase64(gs2-header || cbind-data)when the GS2 flag isp, which is what libpq and rust-postgres sign over forSCRAM-SHA-256-PLUS.client-firstbut verified the proof as ifc=were only the GS2 header, so a real handshake would fail.ScramClient::new_with_channel_binding) so the handshake can be tested end-to-end, including the stored-key path.ydowngrade when the server is configured for channel binding.Needed for pgdogdev/pgdog#1453 (see also the follow-up pgdog PR).
Test plan
cargo test— existing non-PLUS handshakes stay greentls-server-end-pointdataNotAuthenticatedpg_shadow) PLUS handshake succeedsy/n/ type-mismatch still rejected when the server requires bindingMade with Cursor