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Merge pull request #365 from koic/conformance_client_auth_offline_access_scope

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Request offline_access scope when supported (SEP-2207)
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Koichi ITO 2026-06-01 01:09:01 +09:00 • committed by GitHub
commit cf44475ce9
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5 changed files with 229 additions and 2 deletions
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3
README.md
View file

@ -1913,6 +1913,9 @@ pass an `MCP::Client::OAuth::Provider` to the transport instead of a static `Aut
- On a `401 Unauthorized`, parse the `WWW-Authenticate` header, discover the authorization server (Protected Resource Metadata + RFC 8414 Authorization Server Metadata),
perform Dynamic Client Registration if needed, run the OAuth 2.1 Authorization Code flow with PKCE (S256), and retry the failed request with the acquired token.
- On subsequent 401s with a saved `refresh_token`, exchange it at the token endpoint before falling back to the full interactive flow (RFC 6749 Section 6).
- Request the `offline_access` scope when `client_metadata[:grant_types]` includes `refresh_token` and the authorization server advertises `offline_access` in its metadata
`scopes_supported` (SEP-2207). This is what lets the server issue the `refresh_token` used above. As an SDK-level safeguard, when the authorization server does not advertise
`offline_access` the scope is also stripped from any other source (challenge, PRM, or provider-supplied scope) so a server that does not support it never receives it.
```ruby
require "mcp"

2
conformance/client.rb
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@ -87,7 +87,7 @@ def build_oauth_provider(context, scenario:)
client_metadata: {
client_name: "ruby-sdk-conformance-client",
redirect_uris: [redirect_uri],
grant_types: ["authorization_code"],
grant_types: ["authorization_code", "refresh_token"],
response_types: ["code"],
token_endpoint_auth_method: "none",
},

1
conformance/expected_failures.yml
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@ -11,4 +11,3 @@ client:
- auth/client-credentials-jwt
- auth/client-credentials-basic
- auth/cross-app-access-complete-flow
- auth/offline-access-scope

43
lib/mcp/client/oauth/flow.rb
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@ -59,6 +59,7 @@ module MCP
client_info = ensure_client_registered(as_metadata: as_metadata)
effective_scope = resolve_scope(scope: scope, prm: prm)
effective_scope = normalize_offline_access_scope(effective_scope, as_metadata: as_metadata)
pkce = PKCE.generate
state = SecureRandom.urlsafe_base64(32)
@ -441,6 +442,48 @@ module MCP
nil
end
# Applies the SDK's `offline_access` policy to the resolved scope. The policy has two halves:
#
# - Spec (SEP-2207): a client that wants a refresh token (signalled here by listing
# `refresh_token` in its registered `grant_types`) MAY request `offline_access`
# when the authorization server advertises it in metadata `scopes_supported`.
# When the server advertises it and the client opted in, add it if absent.
#
# - SDK policy (defensive hardening): when the server does NOT advertise `offline_access`,
# strip it from the resolved scope no matter where it came from (the `WWW-Authenticate` challenge,
# PRM `scopes_supported`, or the provider-supplied scope). SEP-2207 only says clients SHOULD NOT
# request unsupported scopes, but a misbehaving RS that includes `offline_access` in its challenge,
# or a misconfigured PRM that lists it under `scopes_supported`, would otherwise propagate into
# the authorization request even though the AS will not honour it. Stripping here keeps the SDK's
# own request consistent with the AS's advertisement.
#
# Returns `nil` when the result is empty so `build_authorization_url` omits the `scope` parameter entirely.
# https://github.com/modelcontextprotocol/modelcontextprotocol/pull/2207
def normalize_offline_access_scope(scope, as_metadata:)
scopes = scope.to_s.split
if server_supports_offline_access?(as_metadata)
scopes << "offline_access" if wants_refresh_token? && !scopes.include?("offline_access")
else
scopes.delete("offline_access")
end
scopes.empty? ? nil : scopes.join(" ")
end
def server_supports_offline_access?(as_metadata)
supported = as_metadata["scopes_supported"]
supported.is_a?(Array) && supported.include?("offline_access")
end
def wants_refresh_token?
metadata = @provider.client_metadata
grant_types = metadata[:grant_types] || metadata["grant_types"]
Array(grant_types).include?("refresh_token")
end
def build_authorization_url(as_metadata:, client_id:, scope:, state:, code_challenge:, resource:)
authorization_endpoint = as_metadata["authorization_endpoint"]
unless authorization_endpoint

182
test/mcp/client/oauth/flow_test.rb
View file

@ -68,6 +68,34 @@ module MCP
WebMock.reset!
end
# Runs the full authorization flow and returns the `scope` query parameter
# sent on the authorization request. The caller stubs the AS metadata;
# this helper supplies a provider whose `grant_types` and optional pre-set
# `scope` drive the SEP-2207 offline_access decision.
def capture_authorization_scope(grant_types:, provider_scope: nil)
captured_scope = nil
state_holder = {}
provider = Provider.new(
client_metadata: {
redirect_uris: ["http://localhost:0/callback"],
grant_types: grant_types,
response_types: ["code"],
token_endpoint_auth_method: "none",
},
redirect_uri: "http://localhost:0/callback",
redirect_handler: ->(url) {
query = URI.decode_www_form(url.query).to_h
captured_scope = query["scope"]
state_holder[:state] = query.fetch("state")
},
callback_handler: -> { ["test-auth-code", state_holder[:state]] },
scope: provider_scope,
)
Flow.new(provider: provider).run!(server_url: @server_url, resource_metadata_url: @prm_url)
captured_scope
end
def test_run_completes_full_authorization_flow
captured_authorization_url = nil
state_value = nil
@ -112,6 +140,160 @@ module MCP
end
end
def test_run_requests_offline_access_when_advertised_and_refresh_token_grant_declared
# SEP-2207: a client that declares the `refresh_token` grant type requests `offline_access`
# when the AS advertises it, so it can obtain a refresh token.
stub_request(:get, @as_metadata_url).to_return(
status: 200,
headers: { "Content-Type" => "application/json" },
body: JSON.generate(
issuer: @auth_base,
authorization_endpoint: "#{@auth_base}/authorize",
token_endpoint: "#{@auth_base}/token",
registration_endpoint: "#{@auth_base}/register",
response_types_supported: ["code"],
grant_types_supported: ["authorization_code", "refresh_token"],
code_challenge_methods_supported: ["S256"],
token_endpoint_auth_methods_supported: ["none"],
scopes_supported: ["mcp:basic", "offline_access"],
),
)
captured = capture_authorization_scope(grant_types: ["authorization_code", "refresh_token"])
assert_includes(captured.split, "offline_access")
end
def test_run_does_not_request_offline_access_when_refresh_token_grant_not_declared
# The AS advertises offline_access, but the client did not opt into refresh tokens,
# so the scope is not requested.
stub_request(:get, @as_metadata_url).to_return(
status: 200,
headers: { "Content-Type" => "application/json" },
body: JSON.generate(
issuer: @auth_base,
authorization_endpoint: "#{@auth_base}/authorize",
token_endpoint: "#{@auth_base}/token",
registration_endpoint: "#{@auth_base}/register",
response_types_supported: ["code"],
grant_types_supported: ["authorization_code"],
code_challenge_methods_supported: ["S256"],
token_endpoint_auth_methods_supported: ["none"],
scopes_supported: ["mcp:basic", "offline_access"],
),
)
captured = capture_authorization_scope(grant_types: ["authorization_code"])
refute_includes(captured.to_s.split, "offline_access")
end
def test_run_does_not_request_offline_access_when_server_does_not_advertise_it
# SEP-2207 forbids requesting offline_access when the AS does not list it,
# even if the client declared the refresh_token grant type.
stub_request(:get, @as_metadata_url).to_return(
status: 200,
headers: { "Content-Type" => "application/json" },
body: JSON.generate(
issuer: @auth_base,
authorization_endpoint: "#{@auth_base}/authorize",
token_endpoint: "#{@auth_base}/token",
registration_endpoint: "#{@auth_base}/register",
response_types_supported: ["code"],
grant_types_supported: ["authorization_code", "refresh_token"],
code_challenge_methods_supported: ["S256"],
token_endpoint_auth_methods_supported: ["none"],
scopes_supported: ["mcp:basic", "mcp:read"],
),
)
captured = capture_authorization_scope(grant_types: ["authorization_code", "refresh_token"])
refute_includes(captured.to_s.split, "offline_access")
end
def test_run_strips_offline_access_from_provider_scope_when_server_does_not_advertise_it
# SDK policy: even when `offline_access` reaches the resolved scope from a provider-supplied scope
# (or a challenge / PRM scope), do not propagate it to the AS when the AS does not advertise the scope.
# SEP-2207 itself only says clients should not request unsupported scopes; this strip is the SDK's
# defensive layer against misbehaving resource servers and misconfigured PRMs that surface `offline_access`
# even though the AS has not opted in.
stub_request(:get, @as_metadata_url).to_return(
status: 200,
headers: { "Content-Type" => "application/json" },
body: JSON.generate(
issuer: @auth_base,
authorization_endpoint: "#{@auth_base}/authorize",
token_endpoint: "#{@auth_base}/token",
registration_endpoint: "#{@auth_base}/register",
response_types_supported: ["code"],
grant_types_supported: ["authorization_code", "refresh_token"],
code_challenge_methods_supported: ["S256"],
token_endpoint_auth_methods_supported: ["none"],
scopes_supported: ["mcp:basic"],
),
)
captured = capture_authorization_scope(
grant_types: ["authorization_code", "refresh_token"],
provider_scope: "mcp:basic offline_access",
)
refute_includes(captured.to_s.split, "offline_access")
assert_includes(captured.to_s.split, "mcp:basic")
end
def test_run_strips_sole_offline_access_scope_when_server_does_not_advertise_it
# When stripping leaves an empty scope, no `scope` parameter is sent.
stub_request(:get, @as_metadata_url).to_return(
status: 200,
headers: { "Content-Type" => "application/json" },
body: JSON.generate(
issuer: @auth_base,
authorization_endpoint: "#{@auth_base}/authorize",
token_endpoint: "#{@auth_base}/token",
registration_endpoint: "#{@auth_base}/register",
response_types_supported: ["code"],
grant_types_supported: ["authorization_code", "refresh_token"],
code_challenge_methods_supported: ["S256"],
token_endpoint_auth_methods_supported: ["none"],
scopes_supported: ["mcp:basic"],
),
)
captured = capture_authorization_scope(
grant_types: ["authorization_code", "refresh_token"],
provider_scope: "offline_access",
)
assert_nil(captured)
end
def test_run_does_not_duplicate_offline_access_already_in_scope
stub_request(:get, @as_metadata_url).to_return(
status: 200,
headers: { "Content-Type" => "application/json" },
body: JSON.generate(
issuer: @auth_base,
authorization_endpoint: "#{@auth_base}/authorize",
token_endpoint: "#{@auth_base}/token",
registration_endpoint: "#{@auth_base}/register",
response_types_supported: ["code"],
grant_types_supported: ["authorization_code", "refresh_token"],
code_challenge_methods_supported: ["S256"],
token_endpoint_auth_methods_supported: ["none"],
scopes_supported: ["mcp:basic", "offline_access"],
),
)
captured = capture_authorization_scope(
grant_types: ["authorization_code", "refresh_token"],
provider_scope: "mcp:basic offline_access",
)
assert_equal(1, captured.split.count("offline_access"))
end
def test_run_raises_on_state_mismatch
provider = Provider.new(
client_metadata: {