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
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
|
package org.bouncycastle.crypto.encodings;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.security.SecureRandom;
import org.bouncycastle.crypto.AsymmetricBlockCipher;
import org.bouncycastle.crypto.CipherParameters;
import org.bouncycastle.crypto.InvalidCipherTextException;
import org.bouncycastle.crypto.params.AsymmetricKeyParameter;
import org.bouncycastle.crypto.params.ParametersWithRandom;
/**
* this does your basic PKCS 1 v1.5 padding - whether or not you should be using this
* depends on your application - see PKCS1 Version 2 for details.
*/
public class PKCS1Encoding
implements AsymmetricBlockCipher
{
/**
* some providers fail to include the leading zero in PKCS1 encoded blocks. If you need to
* work with one of these set the system property org.bouncycastle.pkcs1.strict to false.
* <p>
* The system property is checked during construction of the encoding object, it is set to
* true by default.
* </p>
*/
public static final String STRICT_LENGTH_ENABLED_PROPERTY = "org.bouncycastle.pkcs1.strict";
private static final int HEADER_LENGTH = 10;
private SecureRandom random;
private AsymmetricBlockCipher engine;
private boolean forEncryption;
private boolean forPrivateKey;
private boolean useStrictLength;
/**
* Basic constructor.
* @param cipher
*/
public PKCS1Encoding(
AsymmetricBlockCipher cipher)
{
this.engine = cipher;
this.useStrictLength = useStrict();
}
//
// for J2ME compatibility
//
private boolean useStrict()
{
// required if security manager has been installed.
String strict = (String)AccessController.doPrivileged(new PrivilegedAction()
{
public Object run()
{
return System.getProperty(STRICT_LENGTH_ENABLED_PROPERTY);
}
});
return strict == null || strict.equals("true");
}
public AsymmetricBlockCipher getUnderlyingCipher()
{
return engine;
}
public void init(
boolean forEncryption,
CipherParameters param)
{
AsymmetricKeyParameter kParam;
if (param instanceof ParametersWithRandom)
{
ParametersWithRandom rParam = (ParametersWithRandom)param;
this.random = rParam.getRandom();
kParam = (AsymmetricKeyParameter)rParam.getParameters();
}
else
{
this.random = new SecureRandom();
kParam = (AsymmetricKeyParameter)param;
}
engine.init(forEncryption, param);
this.forPrivateKey = kParam.isPrivate();
this.forEncryption = forEncryption;
}
public int getInputBlockSize()
{
int baseBlockSize = engine.getInputBlockSize();
if (forEncryption)
{
return baseBlockSize - HEADER_LENGTH;
}
else
{
return baseBlockSize;
}
}
public int getOutputBlockSize()
{
int baseBlockSize = engine.getOutputBlockSize();
if (forEncryption)
{
return baseBlockSize;
}
else
{
return baseBlockSize - HEADER_LENGTH;
}
}
public byte[] processBlock(
byte[] in,
int inOff,
int inLen)
throws InvalidCipherTextException
{
if (forEncryption)
{
return encodeBlock(in, inOff, inLen);
}
else
{
return decodeBlock(in, inOff, inLen);
}
}
private byte[] encodeBlock(
byte[] in,
int inOff,
int inLen)
throws InvalidCipherTextException
{
if (inLen > getInputBlockSize())
{
throw new IllegalArgumentException("input data too large");
}
byte[] block = new byte[engine.getInputBlockSize()];
if (forPrivateKey)
{
block[0] = 0x01; // type code 1
for (int i = 1; i != block.length - inLen - 1; i++)
{
block[i] = (byte)0xFF;
}
}
else
{
random.nextBytes(block); // random fill
block[0] = 0x02; // type code 2
//
// a zero byte marks the end of the padding, so all
// the pad bytes must be non-zero.
//
for (int i = 1; i != block.length - inLen - 1; i++)
{
while (block[i] == 0)
{
block[i] = (byte)random.nextInt();
}
}
}
block[block.length - inLen - 1] = 0x00; // mark the end of the padding
System.arraycopy(in, inOff, block, block.length - inLen, inLen);
return engine.processBlock(block, 0, block.length);
}
/**
* @exception InvalidCipherTextException if the decrypted block is not in PKCS1 format.
*/
private byte[] decodeBlock(
byte[] in,
int inOff,
int inLen)
throws InvalidCipherTextException
{
byte[] block = engine.processBlock(in, inOff, inLen);
if (block.length < getOutputBlockSize())
{
throw new InvalidCipherTextException("block truncated");
}
byte type = block[0];
if (type != 1 && type != 2)
{
throw new InvalidCipherTextException("unknown block type");
}
// BEGIN android-added
if ((type == 1 && forPrivateKey) || (type == 2 && !forPrivateKey))
{
throw new InvalidCipherTextException("invalid block type " + type);
}
// END android-added
if (useStrictLength && block.length != engine.getOutputBlockSize())
{
throw new InvalidCipherTextException("block incorrect size");
}
//
// find and extract the message block.
//
int start;
for (start = 1; start != block.length; start++)
{
byte pad = block[start];
if (pad == 0)
{
break;
}
if (type == 1 && pad != (byte)0xff)
{
throw new InvalidCipherTextException("block padding incorrect");
}
}
start++; // data should start at the next byte
if (start > block.length || start < HEADER_LENGTH)
{
throw new InvalidCipherTextException("no data in block");
}
byte[] result = new byte[block.length - start];
System.arraycopy(block, start, result, 0, result.length);
return result;
}
}
|