This PR functions as a Reference implementation of
[SEP-2468](https://github.com/modelcontextprotocol/modelcontextprotocol/pull/2468)
/ [RFC9207](https://datatracker.ietf.org/doc/rfc9207/).
This PR hardens the MCP OAuth Client functionality against Mix-Up
attacks:
> Mix-up attacks aim to steal an authorization code or access token by
> tricking the client into sending the authorization code or access
> token to the attacker instead of the honest authorization or resource
> server
This PR hardens the client by adding support for a new `iss` parameter
in authorization responses:
- Authorization Servers broadcast support for the `iss` parameter via
the `authorization_response_iss_parameter_supported` metadata parameter
- If the parameter is supported, clients expect to receive the `iss`
parameter in the authorization response
- Clients compare the `iss` parameter in the authorization response to
the `Issuer` parameter in the authorization metadata. The two must match
exactly for the response to be processed.
Fixes#941
Converted timing-based tests to use Go 1.25's synctest for instant,
deterministic execution with simulated time.
Moved converted tests to *_go125_test.go files. Tests using real I/O
(exec.Command, httptest) remain timing-based as they require actual
system operations.
Fixes#680
---------
Co-authored-by: i586147 <lakshana.goswami@sap.com>
Update examples/server/rate-limiting to use the same replace directive
strategy as the auth-middleware example, and fix the breakages.
Also remove the unneeded type parameters in examples/client/middleware.
Add a client example that lists all features on a stdio server. Since
this is our first client example, organize examples by client / server
-- otherwise it is too difficult to find client examples.
For #33
