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/*
* 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 com.android.ike.ikev2.exceptions.IkeProtocolException;
import com.android.ike.ikev2.exceptions.InvalidSyntaxException;
import java.nio.ByteBuffer;
import java.security.SecureRandom;
/**
* IkeNoncePayload represents a Nonce payload.
*
* <p>Length of nonce data must be at least half the key size of negotiated PRF. It must be between
* 16 and 256 octets. IKE library always generates nonce of GENERATED_NONCE_LEN octets which is long
* enough for all currently known PRFs.
*
* <p>Critical bit must be ignored when doing decoding and must not be set when doing encoding for
* this payload.
*
* @see <a href="https://tools.ietf.org/html/rfc7296">RFC 7296, Internet Key Exchange Protocol
* Version 2 (IKEv2).
*/
public final class IkeNoncePayload extends IkePayload {
// The longest key size of all currently known PRFs is 512 bits (64 bytes). Since we are
// required to generate nonce that is long enough for all proposed PRFs, it is simple that we
// always generate 32 bytes nonce, which is enough for all known PRFs.
private static final int GENERATED_NONCE_LEN = 32;
private static final int MIN_NONCE_LEN = 16;
private static final int MAX_NONCE_LEN = 256;
public final byte[] nonceData;
/**
* Construct an instance of IkeNoncePayload in the context of {@link IkePayloadFactory}.
*
* @param critical indicates if it is a critical payload.
* @param payloadBody the nonce data
*/
IkeNoncePayload(boolean critical, byte[] payloadBody) throws IkeProtocolException {
super(PAYLOAD_TYPE_NONCE, critical);
if (payloadBody.length < MIN_NONCE_LEN || payloadBody.length > MAX_NONCE_LEN) {
throw new InvalidSyntaxException(
"Invalid nonce data with length of: " + payloadBody.length);
}
// Check that the length of payloadBody satisfies the "half the key size of negotiated PRF"
// condition when processing IKE Message in upper layer. Cannot do this check here for
// lacking PRF information.
nonceData = payloadBody;
}
/** Generate Nonce data and construct an instance of IkeNoncePayload. */
public IkeNoncePayload() {
super(PAYLOAD_TYPE_NONCE, false);
nonceData = new byte[GENERATED_NONCE_LEN];
new SecureRandom().nextBytes(nonceData);
}
/**
* Encode Nonce payload to ByteBuffer.
*
* @param nextPayload type of payload that follows this payload.
* @param byteBuffer destination ByteBuffer that stores encoded payload.
*/
@Override
protected void encodeToByteBuffer(@PayloadType int nextPayload, ByteBuffer byteBuffer) {
int payloadLength = GENERIC_HEADER_LENGTH + nonceData.length;
encodePayloadHeaderToByteBuffer(nextPayload, payloadLength, byteBuffer);
byteBuffer.put(nonceData);
}
/**
* Get entire payload length.
*
* @return entire payload length.
*/
@Override
protected int getPayloadLength() {
return GENERIC_HEADER_LENGTH + nonceData.length;
}
/**
* Return the payload type as a String.
*
* @return the payload type as a String.
*/
@Override
public String getTypeString() {
return "Nonce";
}
}
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