ComputeEngineChannelCredentials.java

/*
 * Copyright 2020 The gRPC Authors
 *
 * Licensed 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 io.grpc.alts;

import com.google.auth.oauth2.ComputeEngineCredentials;
import com.google.common.collect.ImmutableList;
import io.grpc.CallCredentials;
import io.grpc.ChannelCredentials;
import io.grpc.CompositeChannelCredentials;
import io.grpc.Status;
import io.grpc.alts.internal.AltsProtocolNegotiator.GoogleDefaultProtocolNegotiatorFactory;
import io.grpc.auth.MoreCallCredentials;
import io.grpc.internal.SharedResourcePool;
import io.grpc.netty.GrpcSslContexts;
import io.grpc.netty.InternalNettyChannelCredentials;
import io.grpc.netty.InternalProtocolNegotiator;
import io.netty.handler.ssl.SslContext;
import javax.net.ssl.SSLException;

/**
 * Credentials appropriate to contact Google services when running on Google Compute Engine. This
 * class sets up a secure channel using ALTS if applicable and using TLS as fallback. It is a subset
 * of the functionality provided by {@link GoogleDefaultChannelCredentials}.
 */
public final class ComputeEngineChannelCredentials {
  private ComputeEngineChannelCredentials() {}

  /**
   * Creates credentials for Google Compute Engine. This class sets up a secure channel using ALTS
   * if applicable and using TLS as fallback.
   */
  public static ChannelCredentials create() {
    return newBuilder().build();
  }

  public static Builder newBuilder() {
    return new Builder();
  }

  /** Builder for {@link ComputeEngineChannelCredentials} instances. */
  public static final class Builder {
    private CallCredentials callCredentials;

    /**
     * Receives a call credential so that ComputeEngineChannelCredentials can support non-default
     * service account.
     */
    public Builder setCallCredentials(CallCredentials callCreds) {
      callCredentials = callCreds;
      return this;
    }

    /** Build a ComputeEngineChannelCredentials instance. */
    public ChannelCredentials build() {
      ChannelCredentials nettyCredentials =
          InternalNettyChannelCredentials.create(createClientFactory());
      if (!InternalCheckGcpEnvironment.isOnGcp()) {
        callCredentials =
            new FailingCallCredentials(
                Status.INTERNAL.withDescription(
                    "Compute Engine Credentials can only be used on Google Cloud Platform"));
      }
      if (callCredentials == null) {
        callCredentials = MoreCallCredentials.from(ComputeEngineCredentials.create());
      }
      return CompositeChannelCredentials.create(nettyCredentials, callCredentials);
    }

    private static InternalProtocolNegotiator.ClientFactory createClientFactory() {
      SslContext sslContext;
      try {
        sslContext = GrpcSslContexts.forClient().build();
      } catch (SSLException e) {
        throw new RuntimeException(e);
      }
      return new GoogleDefaultProtocolNegotiatorFactory(
          /* targetServiceAccounts= */ ImmutableList.<String>of(),
          SharedResourcePool.forResource(HandshakerServiceChannel.SHARED_HANDSHAKER_CHANNEL),
          sslContext);
    }
  }
}