wehub-resource-sync
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97 lines
4.5 KiB
Markdown
97 lines
4.5 KiB
Markdown
# bearer-auth
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Resource-server-only bearer auth. Pass a `TokenVerifier` + `AuthSettings`
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(issuer, resource URL, required scopes) when building the streamable-HTTP app
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and the SDK wires three things automatically: a bearer gate that answers 401 +
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`WWW-Authenticate: Bearer ... resource_metadata=...` (or 403 `insufficient_scope`),
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the RFC 9728 protected-resource-metadata document at
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`/.well-known/oauth-protected-resource/mcp`, and the verified `AccessToken`
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inside tool handlers via `get_access_token()`. The verifier here accepts one
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static token — replace it with JWT verification or RFC 7662 introspection. No
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authorization server; see `../oauth/` for the full grant flow.
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## Run it
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```bash
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# HTTP — the client self-hosts the bearer-gated app, connects with the demo
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# bearer token, then tears it down. Self-hosting uses this story's fixed :8000
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# (the issuer/PRM metadata pin it), so :8000 must be free.
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uv run python -m stories.bearer_auth.client --http
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# same, against the lowlevel-API server variant
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uv run python -m stories.bearer_auth.client --http --server server_lowlevel
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# against a server you run yourself (real uvicorn on :8000). The next section's
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# curl probes use it too and `kill` it when done. While it is up it owns :8000,
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# so the two self-host lines above refuse to run rather than test it by mistake.
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uv run python -m stories.bearer_auth.server --port 8000 &
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SERVER_PID=$!
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uv run python -m stories.bearer_auth.client --http http://127.0.0.1:8000/mcp
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```
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`Client(url)` has no `auth=` passthrough, so a target built from a bare URL
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can't carry the token. Both runners close that gap the same way: `run_client`
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(above) and the pytest harness thread the module's `build_auth` export onto the
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`httpx.AsyncClient` underneath the transport and hand `main` a target that is
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already routed through it.
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## Try it without the SDK client
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```bash
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# no token → 401 + WWW-Authenticate pointing at the PRM document
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curl -i -X POST http://127.0.0.1:8000/mcp \
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-H 'content-type: application/json' -H 'accept: application/json, text/event-stream' \
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-d '{"jsonrpc":"2.0","id":1,"method":"ping"}'
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# the RFC 9728 protected-resource-metadata document
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curl -s http://127.0.0.1:8000/.well-known/oauth-protected-resource/mcp | jq
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# done with the server you started in "Run it"
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kill "$SERVER_PID"
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```
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## What to look at
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- `client.py` `main` — opens with `async with Client(target, mode=mode) as
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client:` and that is the whole program. The `target` it receives is a
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transport that already carries the bearer token; nothing in the body knows
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auth exists.
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- `client.py` `build_auth` / `StaticBearerAuth` — bearer auth client-side is
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five lines of `httpx.Auth`. `Client(url, auth=...)` is the ergonomic the SDK
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is missing; until it lands, the auth has to be threaded onto the
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`httpx.AsyncClient` underneath the transport, outside `main`.
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- `server.py` — `MCPServer(token_verifier=..., auth=AuthSettings(...))` is the
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whole recipe; `streamable_http_app()` reads those constructor kwargs and
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mounts the bearer gate + PRM route.
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- `server_lowlevel.py` — same gate, but `lowlevel.Server` takes
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`auth=` / `token_verifier=` at **`streamable_http_app(...)` time**, not in the
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constructor. `mcp.server.auth.*` imports are allowed in lowlevel files
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(helper-tier).
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- `whoami()` — `get_access_token()` returns the per-HTTP-request `AccessToken`.
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It is **not** on `Context` (unlike other SDKs' `ctx.authInfo`); a later
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release will namespace it as `ctx.transport.auth`.
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## Caveats
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- `transport_security=NO_DNS_REBIND` — DNS-rebinding protection is on by default
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for localhost binds; the harness disables it because the in-process httpx
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client sends no `Origin` header. Drop the kwarg for a real deployment.
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- `RESOURCE_URL` is hard-coded to port 8000 (the harness's in-process origin).
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If you change `--port`, edit `RESOURCE_URL` to match or the PRM document's
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`resource` field will be wrong.
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- Auth is HTTP-only; over stdio or the in-memory transport `get_access_token()`
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returns `None` and there is no gate.
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- The 401/403 status codes and `WWW-Authenticate` header are HTTP-level and
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`Client` cannot observe them; they are pinned by
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`tests/interaction/auth/test_bearer.py` and shown via `curl` above.
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## Spec
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[Authorization](https://modelcontextprotocol.io/specification/2025-11-25/basic/authorization)
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· RFC 9728 (Protected Resource Metadata) · RFC 6750 (`WWW-Authenticate: Bearer`)
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## See also
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`oauth/` (full authorization-code grant with an in-process AS) ·
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`oauth_client_credentials/` (M2M `client_credentials` grant) ·
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`stateless_legacy/` (the un-gated hosting baseline).
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