KickJava   Java API By Example, From Geeks To Geeks.

Java > Open Source Codes > org > apache > derby > impl > store > raw > data > DecryptInputStream


1 /*
2
3    Derby - Class org.apache.derby.impl.store.raw.data.DecryptInputStream
4
5    Licensed to the Apache Software Foundation (ASF) under one or more
6    contributor license agreements. See the NOTICE file distributed with
7    this work for additional information regarding copyright ownership.
8    The ASF licenses this file to you under the Apache License, Version 2.0
9    (the "License"); you may not use this file except in compliance with
10    the License. You may obtain a copy of the License at
11
12       http://www.apache.org/licenses/LICENSE-2.0
13
14    Unless required by applicable law or agreed to in writing, software
15    distributed under the License is distributed on an "AS IS" BASIS,
16    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
17    See the License for the specific language governing permissions and
18    limitations under the License.
19
20  */
21
22 package org.apache.derby.impl.store.raw.data;
23
24 import org.apache.derby.iapi.error.StandardException;
25 import org.apache.derby.iapi.store.raw.data.DataFactory;
26 import org.apache.derby.iapi.store.raw.RawStoreFactory;
27
28 import org.apache.derby.iapi.services.io.CompressedNumber;
29
30 import java.io.InputStream JavaDoc;
31 import java.io.IOException JavaDoc;
32
33 /**
34     A DecryptInputStream is used by stream container to access an encrypted
35     stream of bytes.
36 */
37 public class DecryptInputStream extends BufferedByteHolderInputStream {
38
39     // if database is encrypted, bytes to reserve at the beginning of the buffer
40 //protected static final int ENCRYPTION_RESERVE = dataFactory.getEncryptionBlockSize() - 1;
41
42     protected DataFactory dataFactory;
43     protected InputStream JavaDoc in;
44
45     public DecryptInputStream(InputStream JavaDoc in, ByteHolder bh, DataFactory dataFactory)
46         throws IOException JavaDoc {
47
48         super(bh);
49         this.in = in;
50         this.dataFactory = dataFactory;
51         fillByteHolder();
52     }
53
54     public void fillByteHolder() throws IOException JavaDoc {
55
56         if (this.bh.available() == 0) {
57
58             this.bh.clear();
59
60             try {
61                 // from the stream, read the actual length of the bytes
62 // before it was padded and encrypted.
63 int realLen = CompressedNumber.readInt(in);
64                 // if it is -1, we have reached the end of the file.
65 // then we are done.
66 if (realLen == -1)
67                     return;
68
69                 // calculate out what the padding was based on the actual length
70 int tail = realLen % dataFactory.getEncryptionBlockSize();
71                 int padding = (tail == 0) ? 0 : (dataFactory.getEncryptionBlockSize() - tail);
72                 int encryptedLen = realLen + padding;
73
74                 // read all encrypted data including the padding.
75 byte[] ciphertext = new byte[encryptedLen];
76                 in.read(ciphertext, 0, encryptedLen);
77                 byte[] cleartext = new byte[encryptedLen];
78                 // decrypt the data, and stored it in a new byte array.
79 dataFactory.decrypt(ciphertext, 0, encryptedLen, cleartext, 0);
80
81                 // only put the actual data without the padding into the byte holder.
82 bh.write(cleartext, padding, realLen);
83
84             } catch (StandardException se) {
85                 throw new IOException JavaDoc();
86             }
87
88             // allow reading from the byte holder.
89 this.bh.startReading();
90         }
91     }
92 }
93
Popular Tags