ruby-sdk/test/mcp/client/oauth/cross_app_access_provider_test.rb
Koichi ITO 145a6b6230 Support SEP-990 Cross-App Access via ID-JAG and the jwt-bearer Grant
## 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`.
2026-07-13 11:45:42 +09:00

94 lines
3 KiB
Ruby

# frozen_string_literal: true
require "test_helper"
require "mcp/client/oauth"
module MCP
class Client
module OAuth
class CrossAppAccessProviderTest < Minitest::Test
def build_provider(assertion_provider: ->(**) { "id-jag" })
CrossAppAccessProvider.new(
client_id: "xaa-client",
client_secret: "xaa-secret",
assertion_provider: assertion_provider,
)
end
def test_initialize_stores_credentials_with_basic_auth_method
provider = build_provider
info = provider.client_information
assert_equal("xaa-client", info["client_id"])
assert_equal("xaa-secret", info["client_secret"])
assert_equal("client_secret_basic", info["token_endpoint_auth_method"])
end
def test_authorization_flow_is_jwt_bearer
assert_equal(:jwt_bearer, build_provider.authorization_flow)
end
def test_jwt_bearer_assertion_passes_audience_and_resource_through
received = nil
provider = build_provider(
assertion_provider: ->(audience:, resource:) {
received = { audience: audience, resource: resource }
"id-jag-assertion"
},
)
assertion = provider.jwt_bearer_assertion(
audience: "https://auth.example.com",
resource: "https://srv.example.com/mcp",
)
assert_equal("id-jag-assertion", assertion)
assert_equal(
{ audience: "https://auth.example.com", resource: "https://srv.example.com/mcp" },
received,
)
end
def test_initialize_rejects_missing_client_id
assert_raises(CrossAppAccessProvider::InvalidConfigurationError) do
CrossAppAccessProvider.new(
client_id: " ",
client_secret: "xaa-secret",
assertion_provider: ->(**) { "id-jag" },
)
end
end
def test_initialize_rejects_missing_client_secret
# SEP-990 authenticates the jwt-bearer grant with client_secret_basic.
assert_raises(CrossAppAccessProvider::InvalidConfigurationError) do
CrossAppAccessProvider.new(
client_id: "xaa-client",
client_secret: nil,
assertion_provider: ->(**) { "id-jag" },
)
end
end
def test_initialize_rejects_non_callable_assertion_provider
assert_raises(CrossAppAccessProvider::InvalidConfigurationError) do
CrossAppAccessProvider.new(
client_id: "xaa-client",
client_secret: "xaa-secret",
assertion_provider: "not callable",
)
end
end
def test_token_helpers_delegate_to_storage
provider = build_provider
provider.save_tokens("access_token" => "xaa-token")
assert_equal("xaa-token", provider.access_token)
provider.clear_tokens!
assert_nil(provider.tokens)
end
end
end
end
end