src/java/com/android/ike/ikev2/message/IkePayloadFactory.java

/*
 * Copyright (C) 2018 The Android Open Source Project
 *
 * 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 com.android.ike.ikev2.message;

import android.util.Pair;

import com.android.ike.ikev2.exceptions.IkeException;
import com.android.internal.annotations.VisibleForTesting;

import java.nio.ByteBuffer;

/**
 * IkePayloadFactory is used for creating IkePayload according to is type.
 *
 * @see <a href="https://tools.ietf.org/html/rfc7296#section-3">RFC 7296, Internet Key Exchange
 *     Protocol Version 2 (IKEv2).
 */
final class IkePayloadFactory {

    /** Default instance used for constructing IkePayload */
    @VisibleForTesting
    static IkePayloadDecoder sDecoderInstance =
            new IkePayloadDecoder() {
                @Override
                public IkePayload decodeIkePayload(
                        int payloadType, boolean isCritical, byte[] payloadBody)
                        throws IkeException {
                    switch (payloadType) {
                            // TODO: Add cases for creating supported payloads.
                        case IkePayload.PAYLOAD_TYPE_SA:
                            return new IkeSaPayload(isCritical, payloadBody);
                        case IkePayload.PAYLOAD_TYPE_KE:
                            return new IkeKePayload(isCritical, payloadBody);
                        case IkePayload.PAYLOAD_TYPE_NONCE:
                            return new IkeNoncePayload(isCritical, payloadBody);
                        case IkePayload.PAYLOAD_TYPE_NOTIFY:
                            return new IkeNotifyPayload(isCritical, payloadBody);
                        case IkePayload.PAYLOAD_TYPE_VENDOR:
                            return new IkeVendorPayload(isCritical, payloadBody);
                        default:
                            return new IkeUnsupportedPayload(payloadType, isCritical);
                    }
                }
            };

    /**
     * Construct an instance of IkePayload according to its payload type.
     *
     * @param payloadType the current payload type. All supported types will fall in {@link
     *     IkePayload.PayloadType}
     * @param input the encoded IKE message body containing all payloads. Position of it will
     *     increment.
     */
    static Pair<IkePayload, Integer> getIkePayload(int payloadType, ByteBuffer input)
            throws IkeException {
        int nextPayloadType = (int) input.get();
        // read critical bit
        boolean isCritical = ((input.get() & 0x80) == 0x80);

        int payloadLength = Short.toUnsignedInt(input.getShort());
        int bodyLength = payloadLength - IkePayload.GENERIC_HEADER_LENGTH;
        byte[] payloadBody = new byte[bodyLength];
        input.get(payloadBody);

        IkePayload payload =
                sDecoderInstance.decodeIkePayload(payloadType, isCritical, payloadBody);
        return new Pair(payload, nextPayloadType);
    }

    @VisibleForTesting
    interface IkePayloadDecoder {
        IkePayload decodeIkePayload(int payloadType, boolean isCritical, byte[] payloadBody)
                throws IkeException;
    }
}