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Apache POI - Java API To Access Microsoft Format Files
/* ====================================================================
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.xor;
import java.io.File;
import java.io.IOException;
import java.io.OutputStream;
import java.security.GeneralSecurityException;
import java.util.BitSet;
import javax.crypto.Cipher;
import javax.crypto.spec.SecretKeySpec;
import org.apache.poi.EncryptedDocumentException;
import org.apache.poi.poifs.crypt.ChunkedCipherOutputStream;
import org.apache.poi.poifs.crypt.CryptoFunctions;
import org.apache.poi.poifs.crypt.Encryptor;
import org.apache.poi.poifs.filesystem.DirectoryNode;
import org.apache.poi.util.LittleEndian;
public class XOREncryptor extends Encryptor implements Cloneable {
protected XOREncryptor() {
}
@Override
public void confirmPassword(String password) {
int keyComp = CryptoFunctions.createXorKey1(password);
int verifierComp = CryptoFunctions.createXorVerifier1(password);
byte[] xorArray = CryptoFunctions.createXorArray1(password);
byte[] shortBuf = new byte[2];
XOREncryptionVerifier ver = (XOREncryptionVerifier)getEncryptionInfo().getVerifier();
LittleEndian.putUShort(shortBuf, 0, keyComp);
ver.setEncryptedKey(shortBuf);
LittleEndian.putUShort(shortBuf, 0, verifierComp);
ver.setEncryptedVerifier(shortBuf);
setSecretKey(new SecretKeySpec(xorArray, "XOR"));
}
@Override
public void confirmPassword(String password, byte[] keySpec,
byte[] keySalt, byte[] verifier, byte[] verifierSalt,
byte[] integritySalt) {
confirmPassword(password);
}
@Override
public OutputStream getDataStream(DirectoryNode dir)
throws IOException, GeneralSecurityException {
return new XORCipherOutputStream(dir);
}
@Override
public XORCipherOutputStream getDataStream(OutputStream stream, int initialOffset)
throws IOException, GeneralSecurityException {
return new XORCipherOutputStream(stream, initialOffset);
}
protected int getKeySizeInBytes() {
return -1;
}
@Override
public void setChunkSize(int chunkSize) {
// chunkSize is irrelevant
}
@Override
public XOREncryptor clone() throws CloneNotSupportedException {
return (XOREncryptor)super.clone();
}
private class XORCipherOutputStream extends ChunkedCipherOutputStream {
private int recordStart;
private int recordEnd;
public XORCipherOutputStream(OutputStream stream, int initialPos) throws IOException, GeneralSecurityException {
super(stream, -1);
}
public XORCipherOutputStream(DirectoryNode dir) throws IOException, GeneralSecurityException {
super(dir, -1);
}
@Override
protected Cipher initCipherForBlock(Cipher cipher, int block, boolean lastChunk)
throws GeneralSecurityException {
return XORDecryptor.initCipherForBlock(cipher, block, getEncryptionInfo(), getSecretKey(), Cipher.ENCRYPT_MODE);
}
@Override
protected void calculateChecksum(File file, int i) {
}
@Override
protected void createEncryptionInfoEntry(DirectoryNode dir, File tmpFile) {
throw new EncryptedDocumentException("createEncryptionInfoEntry not supported");
}
@Override
public void setNextRecordSize(int recordSize, boolean isPlain) {
if (recordEnd > 0 && !isPlain) {
// encrypt last record
invokeCipher((int)getPos(), true);
}
recordStart = (int)getTotalPos()+4;
recordEnd = recordStart+recordSize;
}
@Override
public void flush() throws IOException {
setNextRecordSize(0, true);
super.flush();
}
@Override
protected int invokeCipher(int posInChunk, boolean doFinal) {
if (posInChunk == 0) {
return 0;
}
final int start = Math.max(posInChunk-(recordEnd-recordStart), 0);
final BitSet plainBytes = getPlainByteFlags();
final byte[] xorArray = getEncryptionInfo().getEncryptor().getSecretKey().getEncoded();
final byte[] chunk = getChunk();
final byte[] plain = (plainBytes.isEmpty()) ? null : chunk.clone();
/*
* From: http://social.msdn.microsoft.com/Forums/en-US/3dadbed3-0e68-4f11-8b43-3a2328d9ebd5
*
* The initial value for XorArrayIndex is as follows:
* XorArrayIndex = (FileOffset + Data.Length) % 16
*
* The FileOffset variable in this context is the stream offset into the Workbook stream at
* the time we are about to write each of the bytes of the record data.
* This (the value) is then incremented after each byte is written.
*/
// ... also need to handle invocation in case of a filled chunk
int xorArrayIndex = recordEnd+(start-recordStart);
for (int i=start; i < posInChunk; i++) {
byte value = chunk[i];
value ^= xorArray[(xorArrayIndex++) & 0x0F];
value = rotateLeft(value, 8-3);
chunk[i] = value;
}
if (plain != null) {
int i = plainBytes.nextSetBit(start);
while (i >= 0 && i < posInChunk) {
chunk[i] = plain[i];
i = plainBytes.nextSetBit(i + 1);
}
}
return posInChunk;
}
private byte rotateLeft(byte bits, int shift) {
return (byte)(((bits & 0xff) << shift) | ((bits & 0xff) >>> (8 - shift)));
}
}
}