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.camel.component.grpc.auth.jwt;
  
  import com.auth0.jwt.JWT;
  import com.auth0.jwt.JWTVerifier;
  import com.auth0.jwt.algorithms.Algorithm;
  import com.auth0.jwt.exceptions.JWTCreationException;
  import com.auth0.jwt.interfaces.DecodedJWT;
  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 org.apache.camel.component.grpc.GrpcConstants;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /**
   * JSON Web Token credentials validator implementation
   */
  public class JwtServerInterceptor implements ServerInterceptor {
      private static final Logger LOG = LoggerFactory.getLogger(JwtServerInterceptor.class);
  
      @SuppressWarnings("rawtypes")
      private static final ServerCall.Listener NOOP_LISTENER = new ServerCall.Listener() {
      };
  
      private final JWTVerifier verifier;
  
      public JwtServerInterceptor(JwtAlgorithm algorithm, String secret, String issuer, String subject) {
          verifier = prepareJwtVerifier(algorithm, secret, issuer, subject);
      }
  
      @Override
      @SuppressWarnings("unchecked")
      public <ReqT, RespT> Listener<ReqT> interceptCall(
              ServerCall<ReqT, RespT> call, Metadata metadata, ServerCallHandler<ReqT, RespT> serverCallHandler) {
          String jwtToken = metadata.get(GrpcConstants.GRPC_JWT_METADATA_KEY);
          if (jwtToken == null) {
              call.close(Status.UNAUTHENTICATED.withDescription("JWT Token is missing from metadata"), metadata);
              return NOOP_LISTENER;
          }
  
          Context ctx;
          try {
              DecodedJWT verified = verifier.verify(jwtToken);
              ctx = Context.current()
                      .withValue(GrpcConstants.GRPC_JWT_USER_ID_CTX_KEY,
                              verified.getSubject() == null ? "anonymous" : verified.getSubject())
                      .withValue(GrpcConstants.GRPC_JWT_CTX_KEY, jwtToken);
          } catch (Exception e) {
              LOG.debug("JWT token verification failed - Unauthenticated");
              call.close(Status.UNAUTHENTICATED.withDescription(e.getMessage()).withCause(e), metadata);
              return NOOP_LISTENER;
          }
  
          return Contexts.interceptCall(ctx, call, metadata, serverCallHandler);
      }
  
      public static JWTVerifier prepareJwtVerifier(JwtAlgorithm algorithmName, String secret, String issuer, String subject) {
          try {
              Algorithm algorithm = JwtHelper.selectAlgorithm(algorithmName, secret);
              return JWT.require(algorithm).withIssuer(issuer).withSubject(subject).build();
          } catch (JWTCreationException e) {
              throw new IllegalArgumentException("Unable to create JWT verifier", e);
          }
      }
  }
  