1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
|
/*
* Copyright (C) 2019 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.crypto;
import android.net.IpSecAlgorithm;
import com.android.ike.ikev2.SaProposal;
import java.nio.ByteBuffer;
import java.security.InvalidAlgorithmParameterException;
import java.security.InvalidKeyException;
import java.security.Provider;
import java.security.spec.AlgorithmParameterSpec;
import java.util.Arrays;
import javax.crypto.AEADBadTagException;
import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.ShortBufferException;
import javax.crypto.spec.GCMParameterSpec;
import javax.crypto.spec.SecretKeySpec;
/**
* IkeCipher represents a negotiated combined-mode cipher(AEAD) encryption algorithm.
*
* <p>Checksum mentioned in this class is also known as authentication tag or Integrity Checksum
* Vector(ICV)
*
* @see <a href="https://tools.ietf.org/html/rfc7296#section-3.3.2">RFC 7296, Internet Key Exchange
* Protocol Version 2 (IKEv2)</a>
* @see <a href="https://tools.ietf.org/html/rfc5282">RFC 5282,Using Authenticated Encryption
* Algorithms with the Encrypted Payload of the Internet Key Exchange version 2 (IKEv2)
* Protocol</a>
*/
public final class IkeCombinedModeCipher extends IkeCipher {
private static final int SALT_LEN_GCM = 4;
private final int mChecksumLen;
private final int mSaltLen;
/** Package private */
IkeCombinedModeCipher(
int algorithmId, int keyLength, int ivLength, String algorithmName, Provider provider) {
super(algorithmId, keyLength, ivLength, algorithmName, true /*isAead*/, provider);
switch (algorithmId) {
case SaProposal.ENCRYPTION_ALGORITHM_AES_GCM_8:
mSaltLen = SALT_LEN_GCM;
mChecksumLen = 8;
break;
case SaProposal.ENCRYPTION_ALGORITHM_AES_GCM_12:
mSaltLen = SALT_LEN_GCM;
mChecksumLen = 12;
break;
case SaProposal.ENCRYPTION_ALGORITHM_AES_GCM_16:
mSaltLen = SALT_LEN_GCM;
mChecksumLen = 16;
break;
default:
throw new IllegalArgumentException(
"Unrecognized Encryption Algorithm ID: " + algorithmId);
}
}
private byte[] doCipherAction(
byte[] data, byte[] additionalAuthData, byte[] keyBytes, byte[] ivBytes, int opmode)
throws AEADBadTagException {
try {
// Provided key consists of encryption/decryption key plus 4-byte salt. Salt is used
// with IV to build the nonce.
ByteBuffer secretKeyAndSaltBuffer = ByteBuffer.wrap(keyBytes);
byte[] secretKeyBytes = new byte[keyBytes.length - mSaltLen];
byte[] salt = new byte[mSaltLen];
secretKeyAndSaltBuffer.get(secretKeyBytes);
secretKeyAndSaltBuffer.get(salt);
SecretKeySpec key = new SecretKeySpec(secretKeyBytes, getAlgorithmName());
ByteBuffer nonceBuffer = ByteBuffer.allocate(mSaltLen + ivBytes.length);
nonceBuffer.put(salt);
nonceBuffer.put(ivBytes);
mCipher.init(opmode, key, getParamSpec(nonceBuffer.array()));
mCipher.updateAAD(additionalAuthData);
ByteBuffer inputBuffer = ByteBuffer.wrap(data);
int outputLen = data.length;
if (opmode == Cipher.ENCRYPT_MODE) outputLen += mChecksumLen;
ByteBuffer outputBuffer = ByteBuffer.allocate(outputLen);
mCipher.doFinal(inputBuffer, outputBuffer);
return outputBuffer.array();
} catch (AEADBadTagException e) {
// Checksum failed in decryption
throw (AEADBadTagException) e;
} catch (InvalidKeyException
| InvalidAlgorithmParameterException
| IllegalBlockSizeException
| BadPaddingException
| ShortBufferException e) {
String errorMessage =
Cipher.ENCRYPT_MODE == opmode
? "Failed to encrypt data: "
: "Failed to decrypt data: ";
throw new IllegalArgumentException(errorMessage, e);
}
}
private AlgorithmParameterSpec getParamSpec(byte[] nonce) {
switch (getAlgorithmId()) {
case SaProposal.ENCRYPTION_ALGORITHM_AES_GCM_8:
// Fall through
case SaProposal.ENCRYPTION_ALGORITHM_AES_GCM_12:
// Fall through
case SaProposal.ENCRYPTION_ALGORITHM_AES_GCM_16:
return new GCMParameterSpec(mChecksumLen * 8, nonce);
default:
throw new IllegalArgumentException(
"Unrecognized Encryption Algorithm ID: " + getAlgorithmId());
}
}
/**
* Encrypt padded data and calculate checksum for it.
*
* @param paddedData the padded data to encrypt.
* @param additionalAuthData additional data to authenticate (also known as associated data).
* @param keyBytes the encryption key.
* @param ivBytes the initialization vector (IV).
* @return the encrypted and padded data with checksum.
*/
public byte[] encrypt(
byte[] paddedData, byte[] additionalAuthData, byte[] keyBytes, byte[] ivBytes) {
try {
return doCipherAction(
paddedData, additionalAuthData, keyBytes, ivBytes, Cipher.ENCRYPT_MODE);
} catch (AEADBadTagException e) {
throw new IllegalArgumentException("Failed to encrypt data: ", e);
}
}
/**
* Authenticate and decrypt the padded data with checksum.
*
* @param paddedDataWithChecksum the padded data with checksum.
* @param additionalAuthData additional data to authenticate (also known as associated data).
* @param keyBytes the decryption key.
* @param ivBytes the initialization vector (IV).
* @return the decrypted and padded data
* @throws AEADBadTagException if authentication or decryption fails
*/
public byte[] decrypt(
byte[] paddedDataWithChecksum,
byte[] additionalAuthData,
byte[] keyBytes,
byte[] ivBytes)
throws AEADBadTagException {
byte[] decryptPaddedDataAndAuthTag =
doCipherAction(
paddedDataWithChecksum,
additionalAuthData,
keyBytes,
ivBytes,
Cipher.DECRYPT_MODE);
int decryptPaddedDataLen = decryptPaddedDataAndAuthTag.length - mChecksumLen;
return Arrays.copyOf(decryptPaddedDataAndAuthTag, decryptPaddedDataLen);
}
/**
* Gets key length of this algorithm (in bytes).
*
* @return the key length (in bytes).
*/
@Override
public int getKeyLength() {
return super.getKeyLength() + mSaltLen;
}
/**
* Returns length of checksum.
*
* @return the length of checksum in bytes.
*/
public int getChecksumLen() {
return mChecksumLen;
}
@Override
public IpSecAlgorithm buildIpSecAlgorithmWithKey(byte[] key) {
validateKeyLenOrThrow(key);
return new IpSecAlgorithm(IpSecAlgorithm.AUTH_CRYPT_AES_GCM, key, mChecksumLen * 8);
}
}
|
