session-android/src/org/thoughtcrime/securesms/crypto/DecryptingPartInputStream.java

234 lines
7.4 KiB
Java
Raw Normal View History

2011-12-20 18:20:44 +00:00
/**
* Copyright (C) 2011 Whisper Systems
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
package org.thoughtcrime.securesms.crypto;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.security.InvalidAlgorithmParameterException;
import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;
import java.util.Arrays;
import java.lang.System;
2011-12-20 18:20:44 +00:00
import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.Mac;
import javax.crypto.NoSuchPaddingException;
import javax.crypto.ShortBufferException;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;
import android.util.Log;
/**
* Class for streaming an encrypted MMS "part" off the disk.
*
* @author Moxie Marlinspike
*/
public class DecryptingPartInputStream extends FileInputStream {
2011-12-20 18:20:44 +00:00
private static final int IV_LENGTH = 16;
private static final int MAC_LENGTH = 20;
2011-12-20 18:20:44 +00:00
private Cipher cipher;
private Mac mac;
2011-12-20 18:20:44 +00:00
private boolean done;
private long totalDataSize;
private long totalRead;
private byte[] overflowBuffer;
2011-12-20 18:20:44 +00:00
public DecryptingPartInputStream(File file, MasterSecret masterSecret) throws FileNotFoundException {
super(file);
try {
if (file.length() <= IV_LENGTH + MAC_LENGTH)
throw new FileNotFoundException("Part shorter than crypto overhead!");
2011-12-20 18:20:44 +00:00
done = false;
mac = initializeMac(masterSecret.getMacKey());
cipher = initializeCipher(masterSecret.getEncryptionKey());
totalDataSize = file.length() - cipher.getBlockSize() - mac.getMacLength();
totalRead = 0;
} catch (InvalidKeyException ike) {
Log.w("EncryptingPartInputStream", ike);
throw new FileNotFoundException("Invalid key!");
} catch (NoSuchAlgorithmException e) {
throw new AssertionError(e);
} catch (InvalidAlgorithmParameterException e) {
throw new AssertionError(e);
} catch (NoSuchPaddingException e) {
throw new AssertionError(e);
} catch (IOException e) {
Log.w("EncryptingPartInputStream", e);
throw new FileNotFoundException("IOException while reading IV!");
}
}
2011-12-20 18:20:44 +00:00
@Override
public int read(byte[] buffer) throws IOException {
return read(buffer, 0, buffer.length);
}
2011-12-20 18:20:44 +00:00
@Override
public int read(byte[] buffer, int offset, int length) throws IOException {
if (totalRead != totalDataSize)
return readIncremental(buffer, offset, length);
else if (!done)
return readFinal(buffer, offset, length);
else
return -1;
}
2014-12-12 09:03:24 +00:00
@Override
public boolean markSupported() {
return false;
}
@Override
public long skip(long byteCount) throws IOException {
long skipped = 0L;
while (skipped < byteCount) {
byte[] buf = new byte[Math.min(4096, (int)(byteCount-skipped))];
int read = read(buf);
skipped += read;
}
return skipped;
}
2011-12-20 18:20:44 +00:00
private int readFinal(byte[] buffer, int offset, int length) throws IOException {
try {
2011-12-20 18:20:44 +00:00
int flourish = cipher.doFinal(buffer, offset);
//mac.update(buffer, offset, flourish);
2011-12-20 18:20:44 +00:00
byte[] ourMac = mac.doFinal();
byte[] theirMac = new byte[mac.getMacLength()];
readFully(theirMac);
2011-12-20 18:20:44 +00:00
if (!Arrays.equals(ourMac, theirMac))
throw new IOException("MAC doesn't match! Potential tampering?");
2011-12-20 18:20:44 +00:00
done = true;
return flourish;
} catch (IllegalBlockSizeException e) {
Log.w("EncryptingPartInputStream", e);
throw new IOException("Illegal block size exception!");
} catch (ShortBufferException e) {
Log.w("EncryptingPartInputStream", e);
throw new IOException("Short buffer exception!");
} catch (BadPaddingException e) {
Log.w("EncryptingPartInputStream", e);
throw new IOException("Bad padding exception!");
}
}
2011-12-20 18:20:44 +00:00
private int readIncremental(byte[] buffer, int offset, int length) throws IOException {
int readLength = 0;
if (null != overflowBuffer) {
if (overflowBuffer.length > length) {
System.arraycopy(overflowBuffer, 0, buffer, offset, length);
overflowBuffer = Arrays.copyOfRange(overflowBuffer, length, overflowBuffer.length);
return length;
} else if (overflowBuffer.length == length) {
System.arraycopy(overflowBuffer, 0, buffer, offset, length);
overflowBuffer = null;
return length;
} else {
System.arraycopy(overflowBuffer, 0, buffer, offset, overflowBuffer.length);
readLength += overflowBuffer.length;
offset += readLength;
length -= readLength;
overflowBuffer = null;
}
}
2011-12-20 18:20:44 +00:00
if (length + totalRead > totalDataSize)
length = (int)(totalDataSize - totalRead);
2011-12-20 18:20:44 +00:00
byte[] internalBuffer = new byte[length];
int read = super.read(internalBuffer, 0, internalBuffer.length <= cipher.getBlockSize() ? internalBuffer.length : internalBuffer.length - cipher.getBlockSize());
2011-12-20 18:20:44 +00:00
totalRead += read;
2011-12-20 18:20:44 +00:00
try {
mac.update(internalBuffer, 0, read);
int outputLen = cipher.getOutputSize(read);
if (outputLen <= length) {
readLength += cipher.update(internalBuffer, 0, read, buffer, offset);
return readLength;
}
byte[] transientBuffer = new byte[outputLen];
outputLen = cipher.update(internalBuffer, 0, read, transientBuffer, 0);
if (outputLen <= length) {
System.arraycopy(transientBuffer, 0, buffer, offset, outputLen);
readLength += outputLen;
} else {
System.arraycopy(transientBuffer, 0, buffer, offset, length);
overflowBuffer = Arrays.copyOfRange(transientBuffer, length, outputLen);
readLength += length;
}
return readLength;
2011-12-20 18:20:44 +00:00
} catch (ShortBufferException e) {
throw new AssertionError(e);
}
2011-12-20 18:20:44 +00:00
}
2011-12-20 18:20:44 +00:00
private Mac initializeMac(SecretKeySpec key) throws NoSuchAlgorithmException, InvalidKeyException {
Mac hmac = Mac.getInstance("HmacSHA1");
hmac.init(key);
return hmac;
}
2011-12-20 18:20:44 +00:00
private Cipher initializeCipher(SecretKeySpec key)
throws InvalidKeyException, InvalidAlgorithmParameterException,
NoSuchAlgorithmException, NoSuchPaddingException, IOException
2011-12-20 18:20:44 +00:00
{
Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
IvParameterSpec iv = readIv(cipher.getBlockSize());
cipher.init(Cipher.DECRYPT_MODE, key, iv);
2011-12-20 18:20:44 +00:00
return cipher;
}
2011-12-20 18:20:44 +00:00
private IvParameterSpec readIv(int size) throws IOException {
byte[] iv = new byte[size];
readFully(iv);
2011-12-20 18:20:44 +00:00
mac.update(iv);
return new IvParameterSpec(iv);
}
2011-12-20 18:20:44 +00:00
private void readFully(byte[] buffer) throws IOException {
int offset = 0;
2011-12-20 18:20:44 +00:00
for (;;) {
int read = super.read(buffer, offset, buffer.length-offset);
2011-12-20 18:20:44 +00:00
if (read + offset < buffer.length) offset += read;
else return;
}
2011-12-20 18:20:44 +00:00
}
}