## Motivation and Context The MCP Enterprise Managed Authorization extension (SEP-990, modelcontextprotocol/modelcontextprotocol#990, accepted/final, published in the ext-auth repository) lets enterprise identity providers govern MCP authorization: the client exchanges an IdP-issued ID token for an Identity Assertion Authorization Grant (ID-JAG) via RFC 8693 token exchange at the IdP, then presents the ID-JAG to the MCP authorization server with the RFC 7523 `jwt-bearer` grant, authenticating with `client_secret_basic`. The `auth/cross-app-access-complete-flow` conformance scenario exercises the complete flow and previously failed its two core checks (the Ruby client ran the authorization-code flow instead). This mirrors the merged TypeScript SDK implementation (`requestJwtAuthorizationGrant` / `CrossAppAccessProvider` in typescript-sdk; the Python SDK tracks the same work in the open python-sdk#1721), adapted to this SDK's provider design: - New `MCP::Client::OAuth::IDJAGTokenExchange.request` performs the RFC 8693 exchange at the IdP token endpoint (`subject_token_type` id_token, `requested_token_type` id-jag, `audience` = the MCP authorization server's issuer, `resource` = the canonical MCP server URL) and validates that the response's `issued_token_type` is an ID-JAG before returning the assertion. The ID-JAG itself is treated as opaque, as in the TypeScript SDK. - New `MCP::Client::OAuth::CrossAppAccessProvider` declares `authorization_flow :jwt_bearer` and takes the assertion from a callable (`call(audience:, resource:)`), so the common `IDJAGTokenExchange` case, enterprise secret stores, and tests all plug in the same way (the TypeScript provider's assertion callback works identically). The MCP AS credentials are stored as `client_secret_basic` client information. - `Flow` dispatches `:jwt_bearer` alongside `:client_credentials`: discovery, issuer validation, and endpoint security checks are shared with `run!`, then `run_jwt_bearer!` requests the assertion with the validated issuer as the audience and posts the `jwt-bearer` grant through the existing `post_to_token_endpoint`. - The conformance client builds a `CrossAppAccessProvider` when the harness injects `idp_id_token` (exchanging it at `idp_token_endpoint` with `idp_client_id`, like the TypeScript and Python conformance clients), and `auth/cross-app-access-complete-flow` is removed from `conformance/expected_failures.yml`. ## How Has This Been Tested? - New `test/mcp/client/oauth/id_jag_token_exchange_test.rb` asserts the exact RFC 8693 form parameters on the wire and the response validation: a non-ID-JAG `issued_token_type` is rejected, as are a missing `access_token`, non-2xx responses, unparseable bodies, and non-object JSON. - New `test/mcp/client/oauth/cross_app_access_provider_test.rb` covers the provider surface: stored `client_secret_basic` credentials, the `:jwt_bearer` flow declaration, audience/resource passthrough to the assertion callable, constructor validation (missing client_id, missing client_secret, non-callable assertion provider), and storage delegation. - New tests in `test/mcp/client/oauth/flow_test.rb` run the full grant against WebMock stubs: the token request carries `grant_type=urn:ietf:params:oauth:grant-type:jwt-bearer`, the assertion, the RFC 8707 `resource`, and HTTP Basic credentials, with no DCR and no authorization-code machinery; the assertion callable receives the validated issuer as `audience` and the canonical server URL as `resource`; an empty assertion aborts before the token endpoint is contacted. ## Breaking Changes None. `IDJAGTokenExchange` and `CrossAppAccessProvider` are new, and the `Flow` dispatch only activates for providers that declare `authorization_flow :jwt_bearer`.
94 lines
3 KiB
Ruby
94 lines
3 KiB
Ruby
# frozen_string_literal: true
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require "test_helper"
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require "mcp/client/oauth"
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module MCP
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class Client
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module OAuth
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class CrossAppAccessProviderTest < Minitest::Test
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def build_provider(assertion_provider: ->(**) { "id-jag" })
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CrossAppAccessProvider.new(
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client_id: "xaa-client",
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client_secret: "xaa-secret",
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assertion_provider: assertion_provider,
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)
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end
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def test_initialize_stores_credentials_with_basic_auth_method
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provider = build_provider
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info = provider.client_information
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assert_equal("xaa-client", info["client_id"])
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assert_equal("xaa-secret", info["client_secret"])
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assert_equal("client_secret_basic", info["token_endpoint_auth_method"])
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end
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def test_authorization_flow_is_jwt_bearer
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assert_equal(:jwt_bearer, build_provider.authorization_flow)
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end
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def test_jwt_bearer_assertion_passes_audience_and_resource_through
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received = nil
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provider = build_provider(
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assertion_provider: ->(audience:, resource:) {
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received = { audience: audience, resource: resource }
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"id-jag-assertion"
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},
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)
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assertion = provider.jwt_bearer_assertion(
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audience: "https://auth.example.com",
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resource: "https://srv.example.com/mcp",
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)
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assert_equal("id-jag-assertion", assertion)
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assert_equal(
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{ audience: "https://auth.example.com", resource: "https://srv.example.com/mcp" },
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received,
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)
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end
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def test_initialize_rejects_missing_client_id
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assert_raises(CrossAppAccessProvider::InvalidConfigurationError) do
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CrossAppAccessProvider.new(
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client_id: " ",
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client_secret: "xaa-secret",
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assertion_provider: ->(**) { "id-jag" },
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)
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end
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end
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def test_initialize_rejects_missing_client_secret
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# SEP-990 authenticates the jwt-bearer grant with client_secret_basic.
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assert_raises(CrossAppAccessProvider::InvalidConfigurationError) do
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CrossAppAccessProvider.new(
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client_id: "xaa-client",
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client_secret: nil,
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assertion_provider: ->(**) { "id-jag" },
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)
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end
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end
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def test_initialize_rejects_non_callable_assertion_provider
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assert_raises(CrossAppAccessProvider::InvalidConfigurationError) do
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CrossAppAccessProvider.new(
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client_id: "xaa-client",
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client_secret: "xaa-secret",
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assertion_provider: "not callable",
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)
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end
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end
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def test_token_helpers_delegate_to_storage
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provider = build_provider
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provider.save_tokens("access_token" => "xaa-token")
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assert_equal("xaa-token", provider.access_token)
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provider.clear_tokens!
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assert_nil(provider.tokens)
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end
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end
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end
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end
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end
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