1 /* 2 * Copyright (C) 2018 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 package com.android.internal.net.ipsec.ike.message; 18 19 import android.net.ipsec.ike.exceptions.IkeProtocolException; 20 import android.net.ipsec.ike.exceptions.InvalidSyntaxException; 21 22 import com.android.internal.net.ipsec.ike.utils.RandomnessFactory; 23 24 import java.nio.ByteBuffer; 25 import java.security.SecureRandom; 26 27 /** 28 * IkeNoncePayload represents a Nonce payload. 29 * 30 * <p>Length of nonce data must be at least half the key size of negotiated PRF. It must be between 31 * 16 and 256 octets. IKE library always generates nonce of GENERATED_NONCE_LEN octets which is long 32 * enough for all currently known PRFs. 33 * 34 * <p>Critical bit must be ignored when doing decoding and must not be set when doing encoding for 35 * this payload. 36 * 37 * @see <a href="https://tools.ietf.org/html/rfc7296">RFC 7296, Internet Key Exchange Protocol 38 * Version 2 (IKEv2). 39 */ 40 public final class IkeNoncePayload extends IkePayload { 41 // The longest key size of all currently known PRFs is 512 bits (64 bytes). Since we are 42 // required to generate nonce that is long enough for all proposed PRFs, it is simple that we 43 // always generate 32 bytes nonce, which is enough for all known PRFs. 44 private static final int GENERATED_NONCE_LEN = 32; 45 46 private static final int MIN_NONCE_LEN = 16; 47 private static final int MAX_NONCE_LEN = 256; 48 49 public final byte[] nonceData; 50 51 /** 52 * Construct an instance of IkeNoncePayload in the context of {@link IkePayloadFactory}. 53 * 54 * @param critical indicates if it is a critical payload. 55 * @param payloadBody the nonce data 56 */ IkeNoncePayload(boolean critical, byte[] payloadBody)57 IkeNoncePayload(boolean critical, byte[] payloadBody) throws IkeProtocolException { 58 super(PAYLOAD_TYPE_NONCE, critical); 59 if (payloadBody.length < MIN_NONCE_LEN || payloadBody.length > MAX_NONCE_LEN) { 60 throw new InvalidSyntaxException( 61 "Invalid nonce data with length of: " + payloadBody.length); 62 } 63 // Check that the length of payloadBody satisfies the "half the key size of negotiated PRF" 64 // condition when processing IKE Message in upper layer. Cannot do this check here for 65 // lacking PRF information. 66 nonceData = payloadBody; 67 } 68 69 /** Generate Nonce data and construct an instance of IkeNoncePayload. */ IkeNoncePayload(RandomnessFactory randomnessFactory)70 public IkeNoncePayload(RandomnessFactory randomnessFactory) { 71 super(PAYLOAD_TYPE_NONCE, false); 72 nonceData = new byte[GENERATED_NONCE_LEN]; 73 74 SecureRandom random = randomnessFactory.getRandom(); 75 random = random == null ? new SecureRandom() : random; 76 random.nextBytes(nonceData); 77 } 78 79 /** 80 * Encode Nonce payload to ByteBuffer. 81 * 82 * @param nextPayload type of payload that follows this payload. 83 * @param byteBuffer destination ByteBuffer that stores encoded payload. 84 */ 85 @Override encodeToByteBuffer(@ayloadType int nextPayload, ByteBuffer byteBuffer)86 protected void encodeToByteBuffer(@PayloadType int nextPayload, ByteBuffer byteBuffer) { 87 int payloadLength = GENERIC_HEADER_LENGTH + nonceData.length; 88 89 encodePayloadHeaderToByteBuffer(nextPayload, payloadLength, byteBuffer); 90 byteBuffer.put(nonceData); 91 } 92 93 /** 94 * Get entire payload length. 95 * 96 * @return entire payload length. 97 */ 98 @Override getPayloadLength()99 protected int getPayloadLength() { 100 return GENERIC_HEADER_LENGTH + nonceData.length; 101 } 102 103 /** 104 * Return the payload type as a String. 105 * 106 * @return the payload type as a String. 107 */ 108 @Override getTypeString()109 public String getTypeString() { 110 return "Nonce"; 111 } 112 } 113