content: /*
   * Licensed to the Apache Software Foundation (ASF) under one or more
   * contributor license agreements.  See the NOTICE file distributed with
   * this work for additional information regarding copyright ownership.
   * The ASF licenses this file to You under the Apache License, Version 2.0
   * (the "License"); you may not use this file except in compliance with
   * the License.  You may obtain a copy of the License at
   *
   *    http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package org.apache.arrow.flight.auth;
  
  import io.grpc.Context;
  import io.grpc.Contexts;
  import io.grpc.Metadata;
  import io.grpc.ServerCall;
  import io.grpc.ServerCall.Listener;
  import io.grpc.ServerCallHandler;
  import io.grpc.ServerInterceptor;
  import io.grpc.Status;
  import io.grpc.StatusRuntimeException;
  import java.util.Optional;
  import org.apache.arrow.flight.FlightRuntimeException;
  import org.apache.arrow.flight.grpc.StatusUtils;
  
  /** GRPC Interceptor for performing authentication. */
  public class ServerAuthInterceptor implements ServerInterceptor {
  
    private final ServerAuthHandler authHandler;
  
    public ServerAuthInterceptor(ServerAuthHandler authHandler) {
      this.authHandler = authHandler;
    }
  
    @Override
    public <ReqT, RespT> Listener<ReqT> interceptCall(
        ServerCall<ReqT, RespT> call, Metadata headers, ServerCallHandler<ReqT, RespT> next) {
      if (!call.getMethodDescriptor()
          .getFullMethodName()
          .equals(AuthConstants.HANDSHAKE_DESCRIPTOR_NAME)) {
        final Optional<String> peerIdentity;
  
        // Allow customizing the response code by throwing FlightRuntimeException
        try {
          peerIdentity = isValid(headers);
        } catch (FlightRuntimeException e) {
          final Status grpcStatus = StatusUtils.toGrpcStatus(e.status());
          call.close(grpcStatus, new Metadata());
          return new NoopServerCallListener<>();
        } catch (StatusRuntimeException e) {
          Metadata trailers = e.getTrailers();
          call.close(e.getStatus(), trailers == null ? new Metadata() : trailers);
          return new NoopServerCallListener<>();
        }
  
        if (!peerIdentity.isPresent()) {
          // Send back a description along with the status code
          call.close(
              Status.UNAUTHENTICATED.withDescription(
                  "Unauthenticated (invalid or missing auth token)"),
              new Metadata());
          return new NoopServerCallListener<>();
        }
        return Contexts.interceptCall(
            Context.current().withValue(AuthConstants.PEER_IDENTITY_KEY, peerIdentity.get()),
            call,
            headers,
            next);
      }
  
      return next.startCall(call, headers);
    }
  
    private Optional<String> isValid(Metadata headers) {
      byte[] token = headers.get(AuthConstants.TOKEN_KEY);
      return authHandler.isValid(token);
    }
  
    private static class NoopServerCallListener<T> extends ServerCall.Listener<T> {}
  }
  