From: peli0101 <peli0101@72b678ce-9140-0410-bee8-679b907dd61a>
Date: Fri, 3 Apr 2009 06:57:58 +0000 (+0000)
Subject: OI Safe: Implement secure delete for encryption / decryption of files.
X-Git-Url: https://hydra-www.ietfng.org/gitweb/?a=commitdiff_plain;h=e65c4c42ea77c1f1fba8a7ca13c295566bac11c0;p=android-vcpass-oisafe

OI Safe: Implement secure delete for encryption / decryption of files.

git-svn-id: http://openintents.googlecode.com/svn/trunk/Safe@2012 72b678ce-9140-0410-bee8-679b907dd61a
---

diff --git a/src/org/openintents/safe/CryptoHelper.java b/src/org/openintents/safe/CryptoHelper.java
index 9400f74..1d289b5 100644
--- a/src/org/openintents/safe/CryptoHelper.java
+++ b/src/org/openintents/safe/CryptoHelper.java
@@ -41,6 +41,8 @@ import javax.crypto.SecretKeyFactory;
 import javax.crypto.spec.PBEKeySpec;
 import javax.crypto.spec.PBEParameterSpec;
 
+import org.openintents.util.SecureDelete;
+
 import android.content.ContentResolver;
 import android.net.Uri;
 import android.os.Environment;
@@ -657,6 +659,9 @@ public class CryptoHelper {
 				is.close();
 				os.close();
 				
+				// Securely delete the original file:
+				SecureDelete.delete(new File(fileUri.getPath()));
+				
 		    } catch (ESJException e) {
 				Log.e(TAG, "Error encrypting file", e);
 	    	}
@@ -796,6 +801,9 @@ public class CryptoHelper {
 				// Close the input stream and return bytes
 				is.close();
 				os.close();
+
+				// Securely delete the original file:
+				SecureDelete.delete(new File(fileUri.getPath()));
 				
 		    } catch (ESJException e) {
 				Log.e(TAG, "Error encrypting file", e);
diff --git a/src/org/openintents/util/SecureDelete.java b/src/org/openintents/util/SecureDelete.java
new file mode 100644
index 0000000..ef3372c
--- /dev/null
+++ b/src/org/openintents/util/SecureDelete.java
@@ -0,0 +1,84 @@
+package org.openintents.util;
+
+import java.io.File;
+import java.io.FileNotFoundException;
+import java.io.IOException;
+import java.io.RandomAccessFile;
+import java.nio.MappedByteBuffer;
+import java.nio.channels.FileChannel;
+import java.security.SecureRandom;
+
+import estreamj.ciphers.trivium.Trivium;
+import estreamj.framework.ESJException;
+
+import android.util.Log;
+
+/**
+ * Secure file delete.
+ * 
+ * @author Peli
+ *
+ */
+public class SecureDelete {
+	private static final String TAG = "SecureDelete";
+
+	/**
+	 * Securely delete a file.
+	 * 
+	 * Currently, there is only 1 pass that overwrites the file first
+	 * with a random bit stream generated by Trivium.
+	 * 
+	 * @param file
+	 * @return true if this File was deleted, false otherwise.
+	 */
+	public static boolean delete(File file) {
+
+		if (file.exists()) {
+			SecureRandom random = new SecureRandom();
+
+			Trivium tri = new Trivium();
+			
+			try {
+				RandomAccessFile raf = new RandomAccessFile(file, "rw");
+				FileChannel channel = raf.getChannel();
+				MappedByteBuffer buffer = channel.map(
+						FileChannel.MapMode.READ_WRITE, 0, raf.length());
+
+				byte[] key = new byte[10];
+				byte[] nonce = new byte[10];
+				random.nextBytes(key);
+				random.nextBytes(nonce);
+				
+			    tri.setupKey(Trivium.MODE_DECRYPT,
+			    		key, 0);
+				tri.setupNonce(nonce, 0);
+
+				int buffersize = 1024;
+				byte[] bytes = new byte[1024];
+				
+				// overwrite with random numbers
+				while (buffer.hasRemaining()) {
+					int max = buffer.limit() - buffer.position();
+					if (max > buffersize) max = buffersize;
+					//random.nextBytes(bytes);
+
+				    tri.process(bytes, 0,
+				    		bytes, 0, max);
+				    
+					buffer.put(bytes, 0, max);
+				}
+				buffer.force();
+				buffer.rewind();
+
+			} catch (FileNotFoundException e) {
+				Log.d(TAG, "FileNotFoundException", e);
+			} catch (IOException e) {
+				Log.d(TAG, "IOException", e);
+			} catch (ESJException e) {
+				Log.d(TAG, "ESJException", e);
+			}
+			return file.delete();
+		}
+		return false;
+	}
+}