Yes, Ory Oathkeeper can support authenticating gRPC requests through its gRPC middleware feature. This allows you to embed Oathkeeper directly into your Go application as a gRPC middleware, eliminating the need for an additional network hop. The gRPC middleware handles traffic as if it were a standalone Oathkeeper instance. However, it's important to note that this feature is experimental and may change, with no compatibility guarantees regarding the API. This option is only available if you're using Go and gRPC. Here's how you can use Oathkeeper as a gRPC middleware:

go import (       "<http://github.com/ory/oathkeeper/middleware|github.com/ory/oathkeeper/middleware>"       "<http://google.golang.org/grpc|google.golang.org/grpc>"   )      func setup() {       oathkeeperMW, err := middleware.New(ctx, middleware.WithConfigFile("path/to/config"))       if err != nil {           return nil, nil, fmt.Errorf("failed to create oathkeeper middleware: %w", err)       }          s := grpc.NewServer(           grpc.UnaryInterceptor(mw.UnaryInterceptor()),           grpc.StreamInterceptor(mw.StreamInterceptor()),       )        // register your service to s, start the server, ...   }

The middleware will match only against explicit gRPC matchers, which you can use by specifying

authority

and

full_method

in your JSON configuration:

json {     "id": "some-id",     "version": "v0.36.0-beta.4",     "match": {       "authority": "<http://example.com|example.com>",       "full_method": "my.grpc.package/MyService/MyMethod"     },     "authenticators": [{ "handler": "noop" }],     "authorizer": { "handler": "allow" },     "mutators": [{ "handler": "noop" }],     "errors": [{ "handler": "json" }]   }

[Oathkeeper gRPC middleware documentation](https://www.ory.sh/docs/oathkeeper/grpc-middleware) provides more details on this feature.

Yes, you can use Ory Oathkeeper as a standalone service to authenticate and authorize gRPC requests instead of embedding it as middleware. This would be done through Oathkeeper's Access Control Decision API. When using Oathkeeper as a standalone service for gRPC, you would typically: 1. Configure your gRPC service to make a decision request to Oathkeeper's API before processing each request 2. Use Oathkeeper's decision endpoint to determine if the request should be allowed The Access Control Decision API follows best practices and works with most modern API gateways and reverse proxies. To verify a request, you would send it to the

decisions

endpoint located at the Oathkeeper API port:

GET /decisions/my-service/whatever

Oathkeeper will then respond with a status code indicating whether the request should be allowed (200) or denied (401, etc.). [Oathkeeper Operating Modes documentation](https://www.ory.sh/docs/oathkeeper#operating-modes) explains how the Access Control Decision API works, which you can integrate with your gRPC service. This approach is similar to how Oathkeeper integrates with other proxies like Traefik, as shown in the [Traefik proxy integration guide](https://www.ory.sh/docs/oathkeeper/guides/traefik-proxy-integration), where Traefik forwards authentication decisions to Oathkeeper. For gRPC specifically, you would need to implement the client-side logic to make these decision requests to Oathkeeper before processing each gRPC call.