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
|
package org.spongycastle.crypto.engines;
import org.spongycastle.crypto.BlockCipher;
import org.spongycastle.crypto.CipherParameters;
import org.spongycastle.crypto.InvalidCipherTextException;
import org.spongycastle.crypto.Wrapper;
import org.spongycastle.crypto.modes.CBCBlockCipher;
import org.spongycastle.crypto.params.ParametersWithIV;
import org.spongycastle.crypto.params.ParametersWithRandom;
import java.security.SecureRandom;
/**
* an implementation of the RFC 3211 Key Wrap
* Specification.
*/
public class RFC3211WrapEngine
implements Wrapper
{
private CBCBlockCipher engine;
private ParametersWithIV param;
private boolean forWrapping;
private SecureRandom rand;
public RFC3211WrapEngine(BlockCipher engine)
{
this.engine = new CBCBlockCipher(engine);
}
public void init(
boolean forWrapping,
CipherParameters param)
{
this.forWrapping = forWrapping;
if (param instanceof ParametersWithRandom)
{
ParametersWithRandom p = (ParametersWithRandom)param;
rand = p.getRandom();
this.param = (ParametersWithIV)p.getParameters();
}
else
{
if (forWrapping)
{
rand = new SecureRandom();
}
this.param = (ParametersWithIV)param;
}
}
public String getAlgorithmName()
{
return engine.getUnderlyingCipher().getAlgorithmName() + "/RFC3211Wrap";
}
public byte[] wrap(
byte[] in,
int inOff,
int inLen)
{
if (!forWrapping)
{
throw new IllegalStateException("not set for wrapping");
}
engine.init(true, param);
int blockSize = engine.getBlockSize();
byte[] cekBlock;
if (inLen + 4 < blockSize * 2)
{
cekBlock = new byte[blockSize * 2];
}
else
{
cekBlock = new byte[(inLen + 4) % blockSize == 0 ? inLen + 4 : ((inLen + 4) / blockSize + 1) * blockSize];
}
cekBlock[0] = (byte)inLen;
cekBlock[1] = (byte)~in[inOff];
cekBlock[2] = (byte)~in[inOff + 1];
cekBlock[3] = (byte)~in[inOff + 2];
System.arraycopy(in, inOff, cekBlock, 4, inLen);
for (int i = inLen + 4; i < cekBlock.length; i++)
{
cekBlock[i] = (byte)rand.nextInt();
}
for (int i = 0; i < cekBlock.length; i += blockSize)
{
engine.processBlock(cekBlock, i, cekBlock, i);
}
for (int i = 0; i < cekBlock.length; i += blockSize)
{
engine.processBlock(cekBlock, i, cekBlock, i);
}
return cekBlock;
}
public byte[] unwrap(
byte[] in,
int inOff,
int inLen)
throws InvalidCipherTextException
{
if (forWrapping)
{
throw new IllegalStateException("not set for unwrapping");
}
int blockSize = engine.getBlockSize();
if (inLen < 2 * blockSize)
{
throw new InvalidCipherTextException("input too short");
}
byte[] cekBlock = new byte[inLen];
byte[] iv = new byte[blockSize];
System.arraycopy(in, inOff, cekBlock, 0, inLen);
System.arraycopy(in, inOff, iv, 0, iv.length);
engine.init(false, new ParametersWithIV(param.getParameters(), iv));
for (int i = blockSize; i < cekBlock.length; i += blockSize)
{
engine.processBlock(cekBlock, i, cekBlock, i);
}
System.arraycopy(cekBlock, cekBlock.length - iv.length, iv, 0, iv.length);
engine.init(false, new ParametersWithIV(param.getParameters(), iv));
engine.processBlock(cekBlock, 0, cekBlock, 0);
engine.init(false, param);
for (int i = 0; i < cekBlock.length; i += blockSize)
{
engine.processBlock(cekBlock, i, cekBlock, i);
}
if ((cekBlock[0] & 0xff) > cekBlock.length - 4)
{
throw new InvalidCipherTextException("wrapped key corrupted");
}
byte[] key = new byte[cekBlock[0] & 0xff];
System.arraycopy(cekBlock, 4, key, 0, cekBlock[0]);
// Note: Using constant time comparison
int nonEqual = 0;
for (int i = 0; i != 3; i++)
{
byte check = (byte)~cekBlock[1 + i];
nonEqual |= (check ^ key[i]);
}
if (nonEqual != 0)
{
throw new InvalidCipherTextException("wrapped key fails checksum");
}
return key;
}
}
|