feat: support Client ID Metadata Document (CIMD) for OAuth#8550
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Add CIMD support so Goose can connect to MCP servers that support CIMD-based OAuth without requiring manual client registration or DCR. - Host a client metadata JSON document that will be served at https://goose-docs.ai/oauth/client-metadata.json - Use rmcp's start_authorization_with_metadata_url() to pass the CIMD URL into the OAuth flow, with transparent DCR fallback
jh-block
requested review from
DOsinga,
angiejones and
blackgirlbytes
as code owners
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The actual redirect URI sent during the OAuth flow includes /oauth_callback, so the CIMD document must match. RFC 8252 allows dynamic ports for loopback, but the path must be consistent.
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Per documentation/AGENTS.md brand guidelines, the product name should always use a lowercase "g".
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| { | ||
| "client_id": "https://goose-docs.ai/oauth/client-metadata.json", | ||
| "client_name": "goose", | ||
| "redirect_uris": ["http://localhost/oauth_callback"], |
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The OAuth flow sends redirect_uri as http://localhost:{port}/oauth_callback with an ephemeral port (crates/goose/src/oauth/mod.rs line 83), but this metadata document only registers http://localhost/oauth_callback. On authorization servers that enforce exact redirect URI matching for Client ID Metadata Documents, authorization will fail with an invalid redirect URI. Fresh evidence: rmcp’s URL-based client-id path (AuthorizationSession::new in transport/auth.rs, lines 2129-2148 on docs.rs) uses the metadata URL directly when client_id_metadata_document_supported=true and does not fall back to DCR in that branch, so this mismatch is terminal.
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This specific issue is invalid, though it does reveal another issue. RFC 8252 Section 7.3 says that for URLs pointing at loopback IP literals, any port can be used at the time of the request. However, we're using localhost and not an IP literal. Fixed.
RFC 8252 Section 7.3 specifies that dynamic port allowance applies to loopback IP literals (127.0.0.1, [::1]), not "localhost". Switch the redirect URI from localhost to 127.0.0.1, and whitelist both IPv4 and IPv6 loopback addresses in the CIMD document. Existing DCR-registered credentials using localhost will be treated as stale and re-registered on next auth.
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Remove the "scope" field — goose passes an empty scope list and lets the server advertise required scopes. Hardcoding "openid profile email" would cause invalid_scope errors on MCP servers with different scope requirements. Add "refresh_token" to grant_types since goose attempts token refresh on startup via stored credentials.
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| .start_authorization_with_metadata_url( | ||
| &[], | ||
| redirect_uri.as_str(), | ||
| Some("goose"), | ||
| Some(CLIENT_METADATA_URL), |
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Passing Some(CLIENT_METADATA_URL) unconditionally forces rmcp down the URL-based client-id path whenever the server advertises client_id_metadata_document_supported; in AuthorizationSession::new, that branch does not fall back to register_client if the authorization server later fails to resolve the metadata URL. In environments where the server has restricted egress (common for private/enterprise MCP deployments), OAuth now fails even though dynamic client registration would have worked before this change.
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A server which cannot fetch CIMD documents but nonetheless advertises support for CIMD is misconfigured; it's not the client's responsibility to work around that.
| let mut oauth_state = OAuthState::new(mcp_server_url, None).await?; | ||
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| let redirect_uri = format!("http://localhost:{}/oauth_callback", used_addr.port()); | ||
| let redirect_uri = format!("http://127.0.0.1:{}/oauth_callback", used_addr.port()); |
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This change is because we use a dynamic port. RFC 8252 Section 7.3 says that a redirect URL listed in a CIMD which points at a loopback IP literal matches the same URL with any port, but this behaviour is explicitly only for loopback IP literals, not for localhost.
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Summary
Add CIMD (Client ID Metadata Document) support so Goose can connect to MCP servers that support CIMD-based OAuth (SEP-991) without requiring manual client registration or Dynamic Client Registration.
documentation/static/oauth/client-metadata.json, which will be served athttps://goose-docs.ai/oauth/client-metadata.jsonvia the existing docs deploymentstart_authorization_with_metadata_url(), passing the CIMD URL. Servers that support CIMD will use it; others fall back to DCR transparently.Testing
cargo build -p goosecompiles successfullycargo test -p goosepasses (3 pre-existing unrelated failures)Related Issues
Relates to #7071