chore: import upstream snapshot with attribution

examples/stories/oauth_client_credentials/server_lowlevel.py

@@ -0,0 +1,82 @@
+"""Bearer-gated MCP resource server (lowlevel API) + the same minimal ``client_credentials`` AS."""
+
+import base64
+import json
+import secrets
+from typing import Any
+
+import mcp_types as types
+from pydantic import AnyHttpUrl
+from starlette.applications import Starlette
+from starlette.requests import Request
+from starlette.responses import JSONResponse
+from starlette.routing import Route
+
+from mcp.server.auth.middleware.auth_context import get_access_token
+from mcp.server.auth.provider import AccessToken
+from mcp.server.context import ServerRequestContext
+from mcp.server.lowlevel import Server
+from mcp.shared.auth import OAuthMetadata, OAuthToken
+from stories._hosting import NO_DNS_REBIND, run_app_from_args
+from stories._shared.auth import BASE_URL, auth_settings
+
+from .server import DEMO_CLIENT_ID, DEMO_CLIENT_SECRET, DEMO_SCOPE
+
+
+def build_app() -> Starlette:
+    issued: dict[str, AccessToken] = {}
+
+    class _Verifier:
+        async def verify_token(self, token: str) -> AccessToken | None:
+            return issued.get(token)
+
+    async def list_tools(
+        ctx: ServerRequestContext[Any], params: types.PaginatedRequestParams | None
+    ) -> types.ListToolsResult:
+        return types.ListToolsResult(tools=[types.Tool(name="whoami", input_schema={"type": "object"})])
+
+    async def call_tool(ctx: ServerRequestContext[Any], params: types.CallToolRequestParams) -> types.CallToolResult:
+        assert params.name == "whoami"
+        token = get_access_token()
+        assert token is not None
+        payload = {"client_id": token.client_id, "scopes": token.scopes}
+        return types.CallToolResult(content=[types.TextContent(text=json.dumps(payload))], structured_content=payload)
+
+    server = Server("oauth-client-credentials-example", on_list_tools=list_tools, on_call_tool=call_tool)
+
+    async def as_metadata(request: Request) -> JSONResponse:
+        meta = OAuthMetadata(
+            issuer=AnyHttpUrl(BASE_URL),
+            authorization_endpoint=AnyHttpUrl(f"{BASE_URL}/authorize"),  # unused; required
+            token_endpoint=AnyHttpUrl(f"{BASE_URL}/token"),
+            grant_types_supported=["client_credentials"],
+            token_endpoint_auth_methods_supported=["client_secret_basic"],
+            scopes_supported=[DEMO_SCOPE],
+        )
+        return JSONResponse(meta.model_dump(by_alias=True, mode="json", exclude_none=True))
+
+    async def token_endpoint(request: Request) -> JSONResponse:
+        form = await request.form()
+        if form.get("grant_type") != "client_credentials":
+            return JSONResponse({"error": "unsupported_grant_type"}, status_code=400)
+        creds = base64.b64decode(request.headers.get("authorization", "").removeprefix("Basic ")).decode()
+        if creds != f"{DEMO_CLIENT_ID}:{DEMO_CLIENT_SECRET}":
+            return JSONResponse({"error": "invalid_client"}, status_code=401)
+        access = f"access_{secrets.token_hex(16)}"
+        issued[access] = AccessToken(token=access, client_id=DEMO_CLIENT_ID, scopes=[DEMO_SCOPE], expires_at=None)
+        body = OAuthToken(access_token=access, token_type="Bearer", expires_in=3600, scope=DEMO_SCOPE)
+        return JSONResponse(body.model_dump(exclude_none=True), headers={"cache-control": "no-store"})
+
+    return server.streamable_http_app(
+        auth=auth_settings(required_scopes=[DEMO_SCOPE]),
+        token_verifier=_Verifier(),
+        custom_starlette_routes=[
+            Route("/.well-known/oauth-authorization-server", as_metadata, methods=["GET"]),
+            Route("/token", token_endpoint, methods=["POST"]),
+        ],
+        transport_security=NO_DNS_REBIND,
+    )
+
+
+if __name__ == "__main__":
+    run_app_from_args(build_app)