Managoat.McpAuth

MCP authorization discovery with a server-side URL guard.

The discovery chain follows the MCP authorization specification:

  1. RFC 9728 protected-resource metadata comes from the MCP server's 401 challenge, its path-specific well-known URL, or the origin fallback.
  2. RFC 8414 authorization-server metadata supplies the authorization, token, revocation, and optional registration endpoints. OpenID Connect's openid-configuration is the fallback.
  3. RFC 7591 dynamic client registration creates a client when the server offers a registration endpoint.

Every fetched URL must use HTTPS, name a hostname rather than an IP literal, and resolve without any loopback, private, link-local, CGNAT, or metadata address. The guard applies to URLs returned by metadata too: a malicious protected-resource document could otherwise point the next discovery request at the cluster's metadata service.

{:ok, metadata} = Managoat.McpAuth.discover("https://mcp.example/mcp")

opts = [client_name: "My client", client_uri: "https://client.example"]

{:ok, client} =

  Managoat.McpAuth.register(metadata, "https://client.example/callback", opts)

client["client_id"]

The library reads optional defaults from its own application environment: config :managoat_mcp_auth, timeout_ms: 15_000, req_options: [], allow_private_hosts: false. Prefer the allow_private_hosts: option on Managoat.McpAuth.UrlGuard.check/2 when a test only needs to bypass DNS resolution.

Licence

Apache-2.0. See LICENSE.