This example uses the StaticInterceptor and FileWatcherInterceptor from the google.golang.org/grpc/authz package. It uses a header based RBAC policy to match each gRPC method to a required role. For simplicity, the context is injected with mock metadata which includes the required roles, but this should be fetched from an appropriate service based on the authenticated context.
Server is expected to require the following roles on an authenticated user to authorize usage of these methods:
UnaryEcho requires the role UNARY_ECHO:WBidirectionalStreamingEcho requires the role STREAM_ECHO:RWUpon receiving a request, the server first checks that a token was supplied, decodes it and checks that a secret is correctly set (hardcoded to super-secret for simplicity, this should use a proper ID provider in production).
If the above is successful, it uses the username in the token to set appropriate roles (hardcoded to the 2 required roles above if the username matches super-user for simplicity, these roles should be supplied externally as well).
Start the server with:
go run server/main.go
The client implementation shows how using a valid token (setting username and secret) with each of the endpoints will return successfully. It also exemplifies how using a bad token will result in codes.PermissionDenied being returned from the service.
Start the client with:
go run client/main.go
The server accepts an optional --authz-option filewatcher flag to set up authorization policy by reading a policy file, and to look for update on the policy file every 100 millisecond. Having GRPC_GO_LOG_SEVERITY_LEVEL environment variable set to info will log out the reload activity of the policy every time a file update is detected.
Start the server with:
GRPC_GO_LOG_SEVERITY_LEVEL=info go run server/main.go --authz-option filewatcher
Start the client with:
go run client/main.go
The client will first hit codes.PermissionDenied error when invoking UnaryEcho although a legitimate username (super-user) is associated with the RPC. This is because the policy file has an intentional glitch (falsely asks for role UNARY_ECHO:RW).
While the server is still running, edit and save the policy file to replace UNARY_ECHO:RW with the correct role UNARY_ECHO:W (policy reload activity should now be found in server logs). This time when the client is started again with the command above, it will be able to get responses just as in the static-policy example.