added omemo padding but disabled by Config.java flag

2 files changed, 19 insertions, 2 deletions

diff --git a/src/main/java/de/pixart/messenger/Config.java b/src/main/java/de/pixart/messenger/Config.java
index 42d642142..51d44822e 100644
--- a/src/main/java/de/pixart/messenger/Config.java
+++ b/src/main/java/de/pixart/messenger/Config.java
@@ -92,6 +92,7 @@ public final class Config {
 
     public static final long OMEMO_AUTO_EXPIRY = 7 * MILLISECONDS_IN_DAY; // delete old OMEMO devices after 7 days od inactivity
     public static final boolean REMOVE_BROKEN_DEVICES = false;
+    public static final boolean OMEMO_PADDING = false;
 
     public static final int MAX_DISPLAY_MESSAGE_CHARS = 4096;
 
diff --git a/src/main/java/de/pixart/messenger/crypto/axolotl/XmppAxolotlMessage.java b/src/main/java/de/pixart/messenger/crypto/axolotl/XmppAxolotlMessage.java
index f49eefb5a..043cc91ff 100644
--- a/src/main/java/de/pixart/messenger/crypto/axolotl/XmppAxolotlMessage.java
+++ b/src/main/java/de/pixart/messenger/crypto/axolotl/XmppAxolotlMessage.java
@@ -162,7 +162,7 @@ public class XmppAxolotlMessage {
             IvParameterSpec ivSpec = new IvParameterSpec(iv);
             Cipher cipher = Cipher.getInstance(CIPHERMODE, PROVIDER);
             cipher.init(Cipher.ENCRYPT_MODE, secretKey, ivSpec);
-            this.ciphertext = cipher.doFinal(plaintext.getBytes());
+            this.ciphertext = cipher.doFinal(Config.OMEMO_PADDING ? getPaddedBytes(plaintext) : plaintext.getBytes());
         } catch (NoSuchAlgorithmException | NoSuchPaddingException | InvalidKeyException
                 | IllegalBlockSizeException | BadPaddingException | NoSuchProviderException
                 | InvalidAlgorithmParameterException e) {
@@ -170,6 +170,22 @@ public class XmppAxolotlMessage {
         }
     }
 
+    private static byte[] getPaddedBytes(String plaintext) {
+        int plainLength = plaintext.getBytes().length;
+        int pad = Math.max(64,(plainLength / 32 + 1) * 32) - plainLength;
+        SecureRandom random = new SecureRandom();
+        int left = random.nextInt(pad);
+        int right = pad - left;
+        StringBuilder builder = new StringBuilder(plaintext);
+        for(int i = 0; i < left; ++i) {
+            builder.insert(0,random.nextBoolean() ? "\t" : " ");
+        }
+        for(int i = 0; i < right; ++i) {
+            builder.append(random.nextBoolean() ? "\t" : " ");
+        }
+        return builder.toString().getBytes();
+    }
+
     public Jid getFrom() {
         return this.from;
     }
@@ -239,7 +255,7 @@ public class XmppAxolotlMessage {
                 cipher.init(Cipher.DECRYPT_MODE, keySpec, ivSpec);
 
                 String plaintext = new String(cipher.doFinal(ciphertext));
-                plaintextMessage = new XmppAxolotlPlaintextMessage(plaintext, session.getFingerprint());
+                plaintextMessage = new XmppAxolotlPlaintextMessage(Config.OMEMO_PADDING ? plaintext.trim() : plaintext, session.getFingerprint());
 
             } catch (NoSuchAlgorithmException | NoSuchPaddingException | InvalidKeyException
                     | InvalidAlgorithmParameterException | IllegalBlockSizeException