From f0c3b31a42ac6269a0ca299f2fa470586f6120be Mon Sep 17 00:00:00 2001
From: Daniel Gultsch <daniel@gultsch.de>
Date: Mon, 9 Jan 2017 21:47:07 +0100
Subject: treat omemo keys >= 32 bytes as containing auth tag. add config flag
 to put auth tag in key

---
 .../crypto/axolotl/XmppAxolotlMessage.java         | 31 ++++++++++++++++++++--
 1 file changed, 29 insertions(+), 2 deletions(-)

(limited to 'src/main/java/eu/siacs/conversations/crypto/axolotl/XmppAxolotlMessage.java')

diff --git a/src/main/java/eu/siacs/conversations/crypto/axolotl/XmppAxolotlMessage.java b/src/main/java/eu/siacs/conversations/crypto/axolotl/XmppAxolotlMessage.java
index 2d6bba55..1f532370 100644
--- a/src/main/java/eu/siacs/conversations/crypto/axolotl/XmppAxolotlMessage.java
+++ b/src/main/java/eu/siacs/conversations/crypto/axolotl/XmppAxolotlMessage.java
@@ -3,7 +3,6 @@ package eu.siacs.conversations.crypto.axolotl;
 import android.util.Base64;
 import android.util.Log;
 
-import org.whispersystems.libaxolotl.protocol.CiphertextMessage;
 
 import java.security.InvalidAlgorithmParameterException;
 import java.security.InvalidKeyException;
@@ -24,6 +23,7 @@ import javax.crypto.spec.IvParameterSpec;
 import javax.crypto.spec.SecretKeySpec;
 
 import eu.siacs.conversations.Config;
+import eu.siacs.conversations.utils.CryptoHelper;
 import eu.siacs.conversations.xml.Element;
 import eu.siacs.conversations.xmpp.jid.Jid;
 
@@ -42,6 +42,7 @@ public class XmppAxolotlMessage {
 
 	private byte[] innerKey;
 	private byte[] ciphertext = null;
+	private byte[] authtagPlusInnerKey = null;
 	private byte[] iv = null;
 	private final Map<Integer, XmppAxolotlSession.AxolotlKey> keys;
 	private final Jid from;
@@ -166,6 +167,14 @@ public class XmppAxolotlMessage {
 			Cipher cipher = Cipher.getInstance(CIPHERMODE, PROVIDER);
 			cipher.init(Cipher.ENCRYPT_MODE, secretKey, ivSpec);
 			this.ciphertext = cipher.doFinal(Config.OMEMO_PADDING ? getPaddedBytes(plaintext) : plaintext.getBytes());
+			if (Config.PUT_AUTH_TAG_INTO_KEY && this.ciphertext != null) {
+				this.authtagPlusInnerKey = new byte[16+16];
+				byte[] ciphertext = new byte[this.ciphertext.length - 16];
+				System.arraycopy(this.ciphertext,0,ciphertext,0,ciphertext.length);
+				System.arraycopy(this.ciphertext,ciphertext.length,authtagPlusInnerKey,16,16);
+				System.arraycopy(this.innerKey,0,authtagPlusInnerKey,0,this.innerKey.length);
+				this.ciphertext = ciphertext;
+			}
 		} catch (NoSuchAlgorithmException | NoSuchPaddingException | InvalidKeyException
 				| IllegalBlockSizeException | BadPaddingException | NoSuchProviderException
 				| InvalidAlgorithmParameterException e) {
@@ -202,7 +211,12 @@ public class XmppAxolotlMessage {
 	}
 
 	public void addDevice(XmppAxolotlSession session) {
-		XmppAxolotlSession.AxolotlKey key = session.processSending(innerKey);
+		XmppAxolotlSession.AxolotlKey key;
+		if (authtagPlusInnerKey != null) {
+			key = session.processSending(authtagPlusInnerKey);
+		} else {
+			key = session.processSending(innerKey);
+		}
 		if (key != null) {
 			keys.put(session.getRemoteAddress().getDeviceId(), key);
 		}
@@ -254,6 +268,19 @@ public class XmppAxolotlMessage {
 		byte[] key = unpackKey(session, sourceDeviceId);
 		if (key != null) {
 			try {
+
+				if (key.length >= 32) {
+					int authtaglength = key.length - 16;
+					Log.d(Config.LOGTAG,"found auth tag as part of omemo key");
+					byte[] newCipherText = new byte[key.length - 16  + ciphertext.length];
+					byte[] newKey = new byte[16];
+					System.arraycopy(ciphertext, 0, newCipherText, 0, ciphertext.length);
+					System.arraycopy(key, 16, newCipherText, ciphertext.length, authtaglength);
+					System.arraycopy(key,0,newKey,0,newKey.length);
+					ciphertext = newCipherText;
+					key = newKey;
+				}
+
 				Cipher cipher = Cipher.getInstance(CIPHERMODE, PROVIDER);
 				SecretKeySpec keySpec = new SecretKeySpec(key, KEYTYPE);
 				IvParameterSpec ivSpec = new IvParameterSpec(iv);
-- 
cgit v1.2.3