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fix(auth): accept RFC 8414 metadata served at the OIDC well-known path

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The SDK's `discoverAuthorizationServerMetadata` picks its validation schema
from the well-known filename that resolved rather than from the document that
came back, so anything found at `/.well-known/openid-configuration` is
validated as an OpenID provider document — requiring `jwks_uri`,
`subject_types_supported` and `id_token_signing_alg_values_supported`, three
fields RFC 8414 does not define. RFC 8414 §5 permits that filename for general
OAuth metadata, so a conforming plain OAuth 2.0 authorization server is
rejected; and because the parse throws instead of continuing the candidate
loop, discovery aborts and the connection fails outright.

Filed upstream as modelcontextprotocol/typescript-sdk#2733.

`core/auth/oidcDiscoveryCompat.ts` works around it without fabricating a
field: on a failed RFC 8414 candidate it probes the OIDC candidates the SDK
would try next and, when one returns a document that satisfies
`OAuthMetadataSchema` but fails the OIDC schema, serves that body as the RFC
8414 response so the SDK picks the schema that describes it. A genuine OpenID
provider document is left to the SDK's own OIDC leg. Issuer validation runs
unchanged, since the substituted document is the one the server published.

It wraps `effectiveAuthFetch` — above the fetch tracker, the opposite of
`withOAuthEndpointOverrides` — so the Network tab still records the real 404
and the real probe rather than the substitution.

The candidate derivation mirrors the SDK's `buildDiscoveryUrls`, which a fetch
wrapper cannot call, and a test pins it against that export so the two cannot
drift.

Adds `oauth.asMetadataPath` to the composable test server (mirroring
`oauth.resourceMetadataPath`) and the `oauth-rfc8414-at-oidc-path-http.json`
showcase config that reproduces the failure.

Closes #2172

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01UL9retfvAXRgvi6EWk4SY4
Signed-off-by: cliffhall <cliff@futurescale.com>
This commit is contained in:
cliffhall 2026-08-28 00:40:11 -04:00
commit 7ca753bc4c
1 changed files with 844 additions and 36 deletions
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8
test-servers/src/load-config.ts
View file

@ -22,6 +22,8 @@ export interface ConfigFileOAuth {
resource?: string;
/** Serve RFC 9728 metadata from this path and advertise it on 401 (#2071). */
resourceMetadataPath?: string;
/** Serve RFC 8414 AS metadata from this path instead of the default (#2172). */
asMetadataPath?: string;
issuerUrl?: string;
accessTokenIssuers?: string[];
jwksUri?: string;
@ -222,6 +224,12 @@ function validateConfig(
`Invalid config in ${filePath}: oauth.resourceMetadataPath must be an origin-relative path (e.g. "/custom/protected-resource") — a value such as "//host/doc" would advertise a document the server does not serve`,
);
}
const asPath = oauth.asMetadataPath;
if (asPath !== undefined && !isOriginRelativePath(asPath)) {
throw new Error(
`Invalid config in ${filePath}: oauth.asMetadataPath must be an origin-relative path (e.g. "/.well-known/openid-configuration") — a value such as "//host/doc" would move the document off this server entirely`,
);
}
if (transportType === "stdio" && oauth.enabled === true) {
throw new Error(
`Invalid config in ${filePath}: oauth requires streamable-http or sse transport`,