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@ -44,24 +44,24 @@ import android.util.Log;
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*/
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public class DecryptingPartInputStream extends FileInputStream {
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private static final int IV_LENGTH = 16;
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private static final int MAC_LENGTH = 20;
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private Cipher cipher;
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private Mac mac;
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private boolean done;
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private long totalDataSize;
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private long totalRead;
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private byte[] overflowBuffer;
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public DecryptingPartInputStream(File file, MasterSecret masterSecret) throws FileNotFoundException {
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super(file);
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try {
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if (file.length() <= IV_LENGTH + MAC_LENGTH)
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throw new FileNotFoundException("Part shorter than crypto overhead!");
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done = false;
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mac = initializeMac(masterSecret.getMacKey());
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cipher = initializeCipher(masterSecret.getEncryptionKey());
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@ -81,12 +81,12 @@ public class DecryptingPartInputStream extends FileInputStream {
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throw new FileNotFoundException("IOException while reading IV!");
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}
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}
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@Override
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public int read(byte[] buffer) throws IOException {
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return read(buffer, 0, buffer.length);
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}
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@Override
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public int read(byte[] buffer, int offset, int length) throws IOException {
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if (totalRead != totalDataSize)
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@ -96,11 +96,11 @@ public class DecryptingPartInputStream extends FileInputStream {
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else
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return -1;
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}
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private int readFinal(byte[] buffer, int offset, int length) throws IOException {
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try {
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try {
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int flourish = cipher.doFinal(buffer, offset);
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// mac.update(buffer, offset, flourish);
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//mac.update(buffer, offset, flourish);
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byte[] ourMac = mac.doFinal();
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byte[] theirMac = new byte[mac.getMacLength()];
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@ -108,7 +108,7 @@ public class DecryptingPartInputStream extends FileInputStream {
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if (!Arrays.equals(ourMac, theirMac))
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throw new IOException("MAC doesn't match! Potential tampering?");
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done = true;
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return flourish;
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} catch (IllegalBlockSizeException e) {
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@ -122,7 +122,7 @@ public class DecryptingPartInputStream extends FileInputStream {
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throw new IOException("Bad padding exception!");
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}
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}
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private int readIncremental(byte[] buffer, int offset, int length) throws IOException {
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int readLength = 0;
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if (null != overflowBuffer) {
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@ -145,11 +145,11 @@ public class DecryptingPartInputStream extends FileInputStream {
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if (length + totalRead > totalDataSize)
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length = (int)(totalDataSize - totalRead);
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byte[] internalBuffer = new byte[length];
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int read = super.read(internalBuffer, 0, internalBuffer.length <= cipher.getBlockSize() ? internalBuffer.length : internalBuffer.length - cipher.getBlockSize());
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totalRead += read;
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try {
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mac.update(internalBuffer, 0, read);
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@ -175,41 +175,41 @@ public class DecryptingPartInputStream extends FileInputStream {
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throw new AssertionError(e);
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}
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}
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private Mac initializeMac(SecretKeySpec key) throws NoSuchAlgorithmException, InvalidKeyException {
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Mac hmac = Mac.getInstance("HmacSHA1");
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hmac.init(key);
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return hmac;
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}
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private Cipher initializeCipher(SecretKeySpec key)
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throws InvalidKeyException, InvalidAlgorithmParameterException,
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NoSuchAlgorithmException, NoSuchPaddingException, IOException
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NoSuchAlgorithmException, NoSuchPaddingException, IOException
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{
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Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
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IvParameterSpec iv = readIv(cipher.getBlockSize());
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cipher.init(Cipher.DECRYPT_MODE, key, iv);
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return cipher;
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}
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private IvParameterSpec readIv(int size) throws IOException {
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byte[] iv = new byte[size];
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readFully(iv);
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mac.update(iv);
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return new IvParameterSpec(iv);
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}
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private void readFully(byte[] buffer) throws IOException {
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int offset = 0;
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for (;;) {
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int read = super.read(buffer, offset, buffer.length-offset);
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if (read + offset < buffer.length) offset += read;
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else return;
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}
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else return;
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}
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}
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}
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