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
|
/* ====================================================================
Licensed to the Apache Software Foundation (ASF) under one or more
contributor license agreements. See the NOTICE file distributed with
this work for additional information regarding copyright ownership.
The ASF licenses this file to You 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 org.apache.poi.poifs.crypt;
import org.apache.poi.poifs.filesystem.DocumentInputStream;
import org.apache.poi.poifs.filesystem.POIFSFileSystem;
import org.apache.poi.util.LittleEndian;
import javax.crypto.Cipher;
import javax.crypto.CipherInputStream;
import javax.crypto.SecretKey;
import javax.crypto.spec.SecretKeySpec;
import java.io.IOException;
import java.io.InputStream;
import java.io.UnsupportedEncodingException;
import java.nio.charset.Charset;
import java.security.GeneralSecurityException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.Arrays;
/**
* @author Maxim Valyanskiy
*/
public class Decryptor {
public static final String DEFAULT_PASSWORD="VelvetSweatshop";
private final EncryptionInfo info;
private byte[] passwordHash;
public Decryptor(EncryptionInfo info) {
this.info = info;
}
private void generatePasswordHash(String password) throws NoSuchAlgorithmException {
MessageDigest sha1 = MessageDigest.getInstance("SHA-1");
byte[] passwordBytes;
try {
passwordBytes = password.getBytes("UTF-16LE");
} catch(UnsupportedEncodingException e) {
throw new RuntimeException("Your JVM is broken - UTF16 not found!");
}
sha1.update(info.getVerifier().getSalt());
byte[] hash = sha1.digest(passwordBytes);
byte[] iterator = new byte[4];
for (int i = 0; i<50000; i++) {
sha1.reset();
LittleEndian.putInt(iterator, i);
sha1.update(iterator);
hash = sha1.digest(hash);
}
passwordHash = hash;
}
private byte[] generateKey(int block) throws NoSuchAlgorithmException {
MessageDigest sha1 = MessageDigest.getInstance("SHA-1");
sha1.update(passwordHash);
byte[] blockValue = new byte[4];
LittleEndian.putInt(blockValue, block);
byte[] finalHash = sha1.digest(blockValue);
int requiredKeyLength = info.getHeader().getKeySize()/8;
byte[] buff = new byte[64];
Arrays.fill(buff, (byte) 0x36);
for (int i=0; i<finalHash.length; i++) {
buff[i] = (byte) (buff[i] ^ finalHash[i]);
}
sha1.reset();
byte[] x1 = sha1.digest(buff);
Arrays.fill(buff, (byte) 0x5c);
for (int i=0; i<finalHash.length; i++) {
buff[i] = (byte) (buff[i] ^ finalHash[i]);
}
sha1.reset();
byte[] x2 = sha1.digest(buff);
byte[] x3 = new byte[x1.length + x2.length];
System.arraycopy(x1, 0, x3, 0, x1.length);
System.arraycopy(x2, 0, x3, x1.length, x2.length);
return Arrays.copyOf(x3, requiredKeyLength);
}
public boolean verifyPassword(String password) throws GeneralSecurityException {
generatePasswordHash(password);
Cipher cipher = getCipher();
byte[] verifier = cipher.doFinal(info.getVerifier().getVerifier());
MessageDigest sha1 = MessageDigest.getInstance("SHA-1");
byte[] calcVerifierHash = sha1.digest(verifier);
byte[] verifierHash = Arrays.copyOf(cipher.doFinal(info.getVerifier().getVerifierHash()), calcVerifierHash.length);
return Arrays.equals(calcVerifierHash, verifierHash);
}
private Cipher getCipher() throws GeneralSecurityException {
byte[] key = generateKey(0);
Cipher cipher = Cipher.getInstance("AES/ECB/NoPadding");
SecretKey skey = new SecretKeySpec(key, "AES");
cipher.init(Cipher.DECRYPT_MODE, skey);
return cipher;
}
public InputStream getDataStream(POIFSFileSystem fs) throws IOException, GeneralSecurityException {
DocumentInputStream dis = fs.createDocumentInputStream("EncryptedPackage");
long size = dis.readLong();
return new CipherInputStream(dis, getCipher());
}
}
|
