mirror of
https://github.com/PrefectHQ/fastmcp.git
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297 lines
11 KiB
Python
297 lines
11 KiB
Python
"""Tests that `issuer_url` is authoritative for authorization server identity.
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Regression tests for #4610. `issuer_url` lets the OAuth issuer identity differ
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from `base_url`, which is where the OAuth endpoints are actually mounted. The
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issuer identity — the `issuer` field of the authorization server metadata, the
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`iss` claim of minted tokens, and the RFC 9207 `iss` authorization response
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parameter — must come from `issuer_url`, while every endpoint URL must keep
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coming from `base_url`.
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RFC 8414 §3.3 is the reason this matters: the protected resource metadata points
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clients at `issuer_url`, the client performs discovery there, and the `issuer`
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in the returned metadata must match the identifier used for discovery.
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"""
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import re
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import time
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from urllib.parse import parse_qs, urlparse
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import httpx2
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import pytest
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from key_value.aio.stores.memory import MemoryStore
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from mcp.server.auth.provider import AuthorizationParams
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from mcp.server.auth.settings import ClientRegistrationOptions, RevocationOptions
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from mcp.shared.auth import OAuthClientInformationFull
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from pydantic import AnyUrl
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from starlette.applications import Starlette
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from starlette.routing import Mount
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from starlette.testclient import TestClient
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from fastmcp import FastMCP
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from fastmcp.server.auth.auth import AccessToken, TokenVerifier
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from fastmcp.server.auth.identity_assertion import IdentityAssertion
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from fastmcp.server.auth.oauth_proxy import OAuthProxy
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from fastmcp.server.auth.providers.in_memory import InMemoryOAuthProvider
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# The server is mounted under /api, so its endpoints live at BASE_URL while its
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# issuer identity is the root of the same host.
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BASE_URL = "https://api.example.com/api"
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ISSUER_URL = "https://api.example.com"
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# Pydantic renders a bare-authority AnyHttpUrl with a trailing slash.
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ISSUER = "https://api.example.com/"
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BASE_URL_ISSUER = "https://api.example.com/api"
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class _Verifier(TokenVerifier):
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"""Minimal token verifier."""
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def __init__(self):
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self.required_scopes = ["read"]
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async def verify_token(self, token: str) -> AccessToken:
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return AccessToken(
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token=token,
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client_id="client-id",
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scopes=self.required_scopes,
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expires_at=int(time.time() + 3600),
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)
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def build_proxy(issuer_url: str | None) -> OAuthProxy:
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"""Build an OAuth proxy mounted at BASE_URL, optionally with a distinct issuer."""
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return OAuthProxy(
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upstream_authorization_endpoint="https://upstream.example.com/authorize",
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upstream_token_endpoint="https://upstream.example.com/token",
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upstream_revocation_endpoint="https://upstream.example.com/revoke",
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upstream_client_id="client-id",
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upstream_client_secret="client-secret",
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token_verifier=_Verifier(),
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base_url=BASE_URL,
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issuer_url=issuer_url,
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client_storage=MemoryStore(),
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jwt_signing_key="test-secret",
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)
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def build_provider(issuer_url: str | None) -> InMemoryOAuthProvider:
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"""Build a plain OAuth provider mounted at BASE_URL, optionally with a distinct issuer."""
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return InMemoryOAuthProvider(
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base_url=BASE_URL,
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issuer_url=issuer_url,
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client_registration_options=ClientRegistrationOptions(enabled=True),
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revocation_options=RevocationOptions(enabled=True),
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)
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def build_mounted_app(auth_provider) -> Starlette:
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"""Mount an authenticated FastMCP server under /api with well-known routes at root."""
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mcp = FastMCP("test-server", auth=auth_provider)
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mcp_app = mcp.http_app(path="/mcp")
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return Starlette(
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routes=[
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*auth_provider.get_well_known_routes(mcp_path="/mcp"),
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Mount("/api", app=mcp_app),
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],
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lifespan=mcp_app.lifespan,
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)
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async def fetch_json(auth_provider, path: str) -> dict:
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"""Fetch a well-known document from a mounted authenticated server."""
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async with httpx2.AsyncClient(
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transport=httpx2.ASGITransport(app=build_mounted_app(auth_provider)),
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base_url=ISSUER_URL,
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) as client:
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response = await client.get(path)
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assert response.status_code == 200
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return response.json()
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class TestOAuthProxyIssuerIdentity:
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"""`OAuthProxy` (and therefore `OIDCProxy`) identity comes from `issuer_url`."""
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async def test_protected_resource_metadata_points_at_issuer_url(self):
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metadata = await fetch_json(
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build_proxy(ISSUER_URL), "/.well-known/oauth-protected-resource/api/mcp"
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)
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assert metadata["authorization_servers"] == [ISSUER]
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async def test_authorization_server_metadata_issuer_is_issuer_url(self):
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metadata = await fetch_json(
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build_proxy(ISSUER_URL), "/.well-known/oauth-authorization-server"
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)
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assert metadata["issuer"] == ISSUER
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@pytest.mark.parametrize(
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"field, expected",
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[
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("authorization_endpoint", f"{BASE_URL}/authorize"),
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("token_endpoint", f"{BASE_URL}/token"),
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("registration_endpoint", f"{BASE_URL}/register"),
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("revocation_endpoint", f"{BASE_URL}/revoke"),
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],
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)
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async def test_endpoints_stay_on_base_url(self, field: str, expected: str):
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metadata = await fetch_json(
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build_proxy(ISSUER_URL), "/.well-known/oauth-authorization-server"
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)
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assert metadata[field] == expected
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async def test_minted_token_iss_claim_is_issuer_url(self):
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proxy = build_proxy(ISSUER_URL)
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# get_routes() configures the MCP path, which creates the JWT issuer.
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proxy.get_routes(mcp_path="/mcp")
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token = proxy.jwt_issuer.issue_access_token(
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client_id="client-id", scopes=["read"], jti="test-jti"
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)
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assert proxy.jwt_issuer.verify_token(token)["iss"] == ISSUER
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async def test_authorization_response_iss_matches_metadata_issuer(self):
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"""RFC 9207: the `iss` on a client-facing response matches the metadata."""
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proxy = build_proxy(ISSUER_URL)
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redirect = "http://localhost:5100/callback"
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client = OAuthClientInformationFull(
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client_id="rfc9207-client",
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client_secret="s",
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redirect_uris=[AnyUrl(redirect)],
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)
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await proxy.register_client(client)
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consent_url = await proxy.authorize(
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client,
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AuthorizationParams(
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redirect_uri=AnyUrl(redirect),
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redirect_uri_provided_explicitly=True,
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state="client-state",
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code_challenge="challenge",
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scopes=["read"],
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),
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)
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txn_id = parse_qs(urlparse(consent_url).query)["txn_id"][0]
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app = Starlette(routes=proxy.get_routes())
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with TestClient(app) as test_client:
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metadata = test_client.get("/.well-known/oauth-authorization-server").json()
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consent = test_client.get(f"/consent?txn_id={txn_id}")
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csrf_match = re.search(
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r"name=\"csrf_token\"\s+value=\"([^\"]+)\"", consent.text
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)
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assert csrf_match
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for name, value in consent.cookies.items():
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test_client.cookies.set(name, value)
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denial = test_client.post(
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"/consent",
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data={
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"action": "deny",
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"txn_id": txn_id,
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"csrf_token": csrf_match.group(1),
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},
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follow_redirects=False,
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)
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assert denial.status_code in (302, 303)
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params = parse_qs(urlparse(denial.headers["location"]).query)
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assert params["iss"] == [ISSUER]
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assert params["iss"] == [metadata["issuer"]]
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@pytest.mark.parametrize(
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"issuer_url, expected",
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[(ISSUER_URL, ISSUER), (None, BASE_URL_ISSUER)],
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)
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def test_identity_assertion_audience_is_issuer_identifier(
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self, issuer_url: str | None, expected: str
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):
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"""SEP-990: an ID-JAG is bound to the server's advertised issuer.
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RFC 7523 §3 requires the `aud` to identify the authorization server,
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and an authorization server is identified by its issuer — the value
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published as `issuer` in the authorization server metadata.
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"""
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proxy = OAuthProxy(
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upstream_authorization_endpoint="https://upstream.example.com/authorize",
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upstream_token_endpoint="https://upstream.example.com/token",
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upstream_client_id="client-id",
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upstream_client_secret="client-secret",
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token_verifier=_Verifier(),
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base_url=BASE_URL,
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issuer_url=issuer_url,
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client_storage=MemoryStore(),
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jwt_signing_key="test-secret",
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identity_assertion=IdentityAssertion(
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trusted_issuers=["https://login.example.com"]
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),
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)
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validator = proxy._identity_assertion_validator
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assert validator is not None
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assert validator.audience == [expected.rstrip("/"), f"{expected.rstrip('/')}/"]
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class TestOAuthProxyIssuerDefaults:
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"""With `issuer_url` unset, identity falls back to `base_url` as before."""
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async def test_authorization_server_metadata_issuer_is_base_url(self):
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# base_url has a path, so RFC 8414 path-aware discovery applies.
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metadata = await fetch_json(
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build_proxy(None), "/.well-known/oauth-authorization-server/api"
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)
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assert metadata["issuer"] == BASE_URL_ISSUER
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async def test_protected_resource_metadata_points_at_base_url(self):
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metadata = await fetch_json(
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build_proxy(None), "/.well-known/oauth-protected-resource/api/mcp"
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)
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assert metadata["authorization_servers"] == [BASE_URL_ISSUER]
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async def test_minted_token_iss_claim_is_base_url(self):
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proxy = build_proxy(None)
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proxy.get_routes(mcp_path="/mcp")
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token = proxy.jwt_issuer.issue_access_token(
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client_id="client-id", scopes=["read"], jti="test-jti"
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)
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assert proxy.jwt_issuer.verify_token(token)["iss"] == BASE_URL_ISSUER
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class TestOAuthProviderIssuerIdentity:
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"""The plain `OAuthProvider` path behaves the same way."""
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async def test_authorization_server_metadata_issuer_is_issuer_url(self):
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metadata = await fetch_json(
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build_provider(ISSUER_URL), "/.well-known/oauth-authorization-server"
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)
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assert metadata["issuer"] == ISSUER
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async def test_protected_resource_metadata_points_at_issuer_url(self):
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metadata = await fetch_json(
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build_provider(ISSUER_URL),
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"/.well-known/oauth-protected-resource/api/mcp",
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)
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assert metadata["authorization_servers"] == [ISSUER]
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@pytest.mark.parametrize(
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"field, expected",
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[
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("authorization_endpoint", f"{BASE_URL}/authorize"),
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("token_endpoint", f"{BASE_URL}/token"),
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("registration_endpoint", f"{BASE_URL}/register"),
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("revocation_endpoint", f"{BASE_URL}/revoke"),
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],
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)
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async def test_endpoints_stay_on_base_url(self, field: str, expected: str):
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metadata = await fetch_json(
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build_provider(ISSUER_URL), "/.well-known/oauth-authorization-server"
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)
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assert metadata[field] == expected
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async def test_issuer_defaults_to_base_url(self):
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# base_url has a path, so RFC 8414 path-aware discovery applies.
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metadata = await fetch_json(
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build_provider(None), "/.well-known/oauth-authorization-server/api"
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)
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assert metadata["issuer"] == BASE_URL_ISSUER
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