Initial Project Import

src/org/thoughtcrime/securesms/crypto/DecryptingPartInputStream.java

@@ -0,0 +1,178 @@
+/** 
+ * 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 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 {
+	
+  private static final int IV_LENGTH  = 16;
+  private static final int MAC_LENGTH = 20;
+	
+  private Cipher cipher;
+  private Mac mac;
+	
+  private boolean done;
+  private long totalDataSize;
+  private long totalRead;
+	
+  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!");
+			
+      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!");
+    }
+  }
+	
+  @Override
+  public int read(byte[] buffer) throws IOException {
+    return read(buffer, 0, buffer.length);
+  }
+	
+  @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;
+  }
+	
+  private int readFinal(byte[] buffer, int offset, int length) throws IOException {
+    try {	
+      int flourish = cipher.doFinal(buffer, offset);
+      //			mac.update(buffer, offset, flourish);
+			
+      byte[] ourMac   = mac.doFinal();
+      byte[] theirMac = new byte[mac.getMacLength()];
+      readFully(theirMac);
+			
+      if (!Arrays.equals(ourMac, theirMac))
+        throw new IOException("MAC doesn't match! Potential tampering?");
+			
+      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!");
+    }
+  }
+	
+  private int readIncremental(byte[] buffer, int offset, int length) throws IOException {
+    if (length + totalRead > totalDataSize)
+      length = (int)(totalDataSize - totalRead);
+		
+    byte[] internalBuffer = new byte[length];
+    int read              = super.read(internalBuffer, 0, internalBuffer.length);
+    totalRead            += read;
+		
+    try {
+      mac.update(internalBuffer, 0, read);
+      return cipher.update(internalBuffer, 0, read, buffer, offset);
+    } catch (ShortBufferException e) {
+      throw new AssertionError(e);
+    }		
+  }
+	
+  private Mac initializeMac(SecretKeySpec key) throws NoSuchAlgorithmException, InvalidKeyException {
+    Mac hmac = Mac.getInstance("HmacSHA1");
+    hmac.init(key);
+
+    return hmac;
+  }
+	
+  private Cipher initializeCipher(SecretKeySpec key) 
+    throws InvalidKeyException, InvalidAlgorithmParameterException, 
+	   NoSuchAlgorithmException, NoSuchPaddingException, IOException 
+  {
+    Cipher cipher      = Cipher.getInstance("AES/CBC/PKCS5Padding");
+    IvParameterSpec iv = readIv(cipher.getBlockSize());
+    cipher.init(Cipher.DECRYPT_MODE, key, iv);
+		
+    return cipher;
+  }
+	
+  private IvParameterSpec readIv(int size) throws IOException {
+    byte[] iv = new byte[size];
+    readFully(iv);
+		
+    mac.update(iv);
+    return new IvParameterSpec(iv);
+  }
+	
+  private void readFully(byte[] buffer) throws IOException {
+    int offset = 0;
+		
+    for (;;) {
+      int read = super.read(buffer, offset, buffer.length-offset);
+			
+      if (read + offset < buffer.length) offset += read;
+      else                		       return;
+    }		
+  }
+	
+
+}