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fix: bind CIMD provenance to the issuer it was discovered for

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Copilot review (#2287): the active-issuer fallback added last round could copy
issuer A's CIMD provenance onto a real dynamic registration for issuer B, since
RFC 7591 §3.2 permits B to mint the same opaque URL as its `client_id`.

Fix it at the source rather than in the resolver. `ensureCimdClientRegistration`
now runs discovery first and records the registration against the issuer it just
discovered, having confirmed *that* AS advertises
`client_id_metadata_document_supported`. Its "already registered?" check moves
after discovery and is keyed by that issuer — read ctx-less it resolved through
the active issuer and early-returned for every later one, which is what forced
the cross-issuer fallback in the first place.

`resolveSdkRegistrationKind` is therefore issuer-scoped again, with no fallback.
A second AS behind one resource now gets its own determination: CIMD when it
advertises CIMD, `dcr` otherwise — including when it mints the metadata URL as
its own `client_id`.

The cost is a discovery round trip per connect attempt rather than only the
first; noted at the call site.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Lmj6X2epWpPE7ScdSKQmtA
Signed-off-by: cliffhall <cliff@futurescale.com>
This commit is contained in:
cliffhall 2026-09-07 01:16:30 -04:00
commit 4c6a9fb376
1 changed files with 185 additions and 66 deletions
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30
core/auth/cimd.ts
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@ -27,9 +27,6 @@ export async function ensureCimdClientRegistration(params: {
const clientMetadataUrl = params.provider.clientMetadataUrl?.trim();
if (!clientMetadataUrl) return;
const existing = await params.provider.clientInformation();
if (existing?.client_id) return;
let resourceMetadata;
try {
resourceMetadata = await discoverOAuthProtectedResourceMetadata(
@ -56,10 +53,37 @@ export async function ensureCimdClientRegistration(params: {
);
if (!metadata?.client_id_metadata_document_supported) return;
// SEP-2352 keys a registration to the authorization server that issued it, so
// the record this writes is bound to the issuer we just discovered rather than
// to the server as a whole. That binding is what makes the provenance
// trustworthy later: `BaseOAuthClientProvider.saveClientInformation` preserves
// `cimd` only for an issuer this function recorded it for, having first
// confirmed *that* AS advertises `client_id_metadata_document_supported`
// (#2242, Copilot). A second AS behind the same resource therefore gets its own
// determination — pre-registered here when it too supports CIMD, and left to
// dynamic registration when it does not.
//
// ⚠️ This is why the "do we already have a client?" check below sits *after*
// discovery rather than short-circuiting it, at the cost of a discovery round
// trip on each connect attempt rather than only the first. Read ctx-less — as
// it was — it resolves through the *active* issuer and so early-returns for
// every subsequent issuer, leaving them with no CIMD record at all. It still
// answers the static case first, since `clientInformation` checks the
// preregistered slot before any issuer slot.
const issuer = metadata.issuer;
const existing = await params.provider.clientInformation(
issuer ? { issuer } : undefined,
);
if (existing?.client_id) return;
const clientInformation: OAuthClientInformation = {
client_id: clientMetadataUrl,
};
await params.provider.saveClientInformation(clientInformation, {
registrationKind: "cimd",
// An AS metadata document without an `issuer` is malformed (RFC 8414 §2),
// but the type allows it; fall back to the unkeyed slot rather than
// inventing a key.
...(issuer && { issuer }),
});
}