clear out plaintext buffers in Android SDK where possible

android/olm-sdk/src/main/java/org/matrix/olm/OlmInboundGroupSession.java

@@ -25,6 +25,8 @@ import java.io.ObjectInputStream;
 import java.io.ObjectOutputStream;
 import java.io.Serializable;
 
+import java.util.Arrays;
+
 /**
  * Class used to create an inbound <a href="http://matrix.org/docs/guides/e2e_implementation.html#handling-an-m-room-key-event">Megolm session</a>.<br>
  * Counter part of the outbound group session {@link OlmOutboundGroupSession}, this class decrypts the messages sent by the outbound side.
@@ -236,7 +238,7 @@ public class OlmInboundGroupSession extends CommonSerializeUtils implements Seri
      * In case of error, null is returned and an error message description is provided in aErrorMsg.
      * @param aEncryptedMsg the message to be decrypted
      * @return the decrypted message information
-     * @exception OlmException teh failure reason
+     * @exception OlmException the failure reason
      */
     public DecryptMessageResult decryptMessage(String aEncryptedMsg) throws OlmException {
         DecryptMessageResult result = new DecryptMessageResult();
@@ -246,6 +248,7 @@ public class OlmInboundGroupSession extends CommonSerializeUtils implements Seri
 
             if (null != decryptedMessageBuffer) {
                 result.mDecryptedMessage = new String(decryptedMessageBuffer, "UTF-8");
+                Arrays.fill(decryptedMessageBuffer, (byte) 0);
             }
         } catch (Exception e) {
             Log.e(LOG_TAG, "## decryptMessage() failed " + e.getMessage());

android/olm-sdk/src/main/java/org/matrix/olm/OlmOutboundGroupSession.java

@@ -26,6 +26,8 @@ import java.io.ObjectInputStream;
 import java.io.ObjectOutputStream;
 import java.io.Serializable;
 
+import java.util.Arrays;
+
 /**
  * Class used to create an outbound a <a href="http://matrix.org/docs/guides/e2e_implementation.html#starting-a-megolm-session">Megolm session</a>.<br>
  * To send a first message in an encrypted room, the client should start a new outbound Megolm session.
@@ -166,7 +168,9 @@ public class OlmOutboundGroupSession extends CommonSerializeUtils implements Ser
 
         if (!TextUtils.isEmpty(aClearMsg)) {
             try {
-                byte[] encryptedBuffer = encryptMessageJni(aClearMsg.getBytes("UTF-8"));
+                byte[] clearMsgBuffer = aClearMsg.getBytes("UTF-8");
+                byte[] encryptedBuffer = encryptMessageJni(clearMsgBuffer);
+                Arrays.fill(clearMsgBuffer, (byte) 0);
 
                 if (null != encryptedBuffer) {
                     retValue = new String(encryptedBuffer , "UTF-8");

android/olm-sdk/src/main/java/org/matrix/olm/OlmPkDecryption.java

@@ -18,6 +18,8 @@ package org.matrix.olm;
 
 import android.util.Log;
 
+import java.util.Arrays;
+
 public class OlmPkDecryption {
     private static final String LOG_TAG = "OlmPkDecryption";
 
@@ -67,7 +69,10 @@ public class OlmPkDecryption {
         }
 
         try {
-            return new String(decryptJni(aMessage), "UTF-8");
+            byte[] plaintextBuffer = decryptJni(aMessage);
+            String plaintext = new String(plaintextBuffer, "UTF-8");
+            Arrays.fill(plaintextBuffer, (byte) 0);
+            return plaintext;
         } catch (Exception e) {
             Log.e(LOG_TAG, "## pkDecrypt(): failed " + e.getMessage());
             throw new OlmException(OlmException.EXCEPTION_CODE_PK_DECRYPTION_DECRYPT, e.getMessage());

android/olm-sdk/src/main/java/org/matrix/olm/OlmPkEncryption.java

@@ -18,6 +18,8 @@ package org.matrix.olm;
 
 import android.util.Log;
 
+import java.util.Arrays;
+
 public class OlmPkEncryption {
     private static final String LOG_TAG = "OlmPkEncryption";
 
@@ -72,7 +74,9 @@ public class OlmPkEncryption {
         OlmPkMessage encryptedMsgRetValue = new OlmPkMessage();
 
         try {
-            byte[] ciphertextBuffer = encryptJni(aPlaintext.getBytes("UTF-8"), encryptedMsgRetValue);
+            byte[] plaintextBuffer = aPlaintext.getBytes("UTF-8");
+            byte[] ciphertextBuffer = encryptJni(plaintextBuffer, encryptedMsgRetValue);
+            Arrays.fill(plaintextBuffer, (byte) 0);
 
             if (null != ciphertextBuffer) {
                 encryptedMsgRetValue.mCipherText = new String(ciphertextBuffer, "UTF-8");

android/olm-sdk/src/main/java/org/matrix/olm/OlmSession.java

@@ -25,6 +25,8 @@ import java.io.ObjectInputStream;
 import java.io.ObjectOutputStream;
 import java.io.Serializable;
 
+import java.util.Arrays;
+
 /**
  * Session class used to create Olm sessions in conjunction with {@link OlmAccount} class.<br>
  * Olm session is used to encrypt data between devices, especially to create Olm group sessions (see {@link OlmOutboundGroupSession} and {@link OlmInboundGroupSession}).<br>
@@ -295,7 +297,9 @@ public class OlmSession extends CommonSerializeUtils implements Serializable {
         OlmMessage encryptedMsgRetValue = new OlmMessage();
 
         try {
-            byte[] encryptedMessageBuffer = encryptMessageJni(aClearMsg.getBytes("UTF-8"), encryptedMsgRetValue);
+            byte[] clearMsgBuffer = aClearMsg.getBytes("UTF-8");
+            byte[] encryptedMessageBuffer = encryptMessageJni(clearMsgBuffer, encryptedMsgRetValue);
+            Arrays.fill(clearMsgBuffer, (byte) 0);
 
             if (null != encryptedMessageBuffer) {
                 encryptedMsgRetValue.mCipherText = new String(encryptedMessageBuffer, "UTF-8");
@@ -330,7 +334,10 @@ public class OlmSession extends CommonSerializeUtils implements Serializable {
         }
 
         try {
-            return new String(decryptMessageJni(aEncryptedMsg), "UTF-8");
+            byte[] plaintextBuffer = decryptMessageJni(aEncryptedMsg);
+            String plaintext = new String(plaintextBuffer, "UTF-8");
+            Arrays.fill(plaintextBuffer, (byte) 0);
+            return plaintext;
         } catch (Exception e) {
             Log.e(LOG_TAG, "## decryptMessage(): failed " + e.getMessage());
             throw new OlmException(OlmException.EXCEPTION_CODE_SESSION_DECRYPT_MESSAGE, e.getMessage());

android/olm-sdk/src/main/jni/olm_outbound_group_session.cpp

@@ -297,6 +297,7 @@ JNIEXPORT jbyteArray OLM_OUTBOUND_GROUP_SESSION_FUNC_DEF(encryptMessageJni)(JNIE
 
     OlmOutboundGroupSession *sessionPtr = NULL;
     jbyte* clearMsgPtr = NULL;
+    jboolean clearMsgIsCopied = JNI_FALSE;
 
     if (!(sessionPtr = (OlmOutboundGroupSession*)getOutboundGroupSessionInstanceId(env,thiz)))
     {
@@ -308,7 +309,7 @@ JNIEXPORT jbyteArray OLM_OUTBOUND_GROUP_SESSION_FUNC_DEF(encryptMessageJni)(JNIE
         LOGE(" ## encryptMessageJni(): failure - invalid clear message");
         errorMessage = "invalid clear message";
     }
-    else if (!(clearMsgPtr = env->GetByteArrayElements(aClearMsgBuffer, NULL)))
+    else if (!(clearMsgPtr = env->GetByteArrayElements(aClearMsgBuffer, &clearMsgIsCopied)))
     {
         LOGE(" ## encryptMessageJni(): failure - clear message JNI allocation OOM");
         errorMessage = "clear message JNI allocation OOM";
@@ -359,6 +360,10 @@ JNIEXPORT jbyteArray OLM_OUTBOUND_GROUP_SESSION_FUNC_DEF(encryptMessageJni)(JNIE
     // free alloc
     if (clearMsgPtr)
     {
+        if (clearMsgIsCopied)
+        {
+            memset(clearMsgPtr, 0, (size_t)env->GetArrayLength(aClearMsgBuffer));
+        }
         env->ReleaseByteArrayElements(aClearMsgBuffer, clearMsgPtr, JNI_ABORT);
     }
 

android/olm-sdk/src/main/jni/olm_pk.cpp

@@ -150,6 +150,7 @@ JNIEXPORT jbyteArray OLM_PK_ENCRYPTION_FUNC_DEF(encryptJni)(
     jbyteArray encryptedMsgRet = 0;
     const char* errorMessage = NULL;
     jbyte *plaintextPtr = NULL;
+    jboolean plaintextIsCopied = JNI_FALSE;
 
     OlmPkEncryption *encryptionPtr = getPkEncryptionInstanceId(env, thiz);
     jclass encryptedMsgJClass = 0;
@@ -165,7 +166,7 @@ JNIEXPORT jbyteArray OLM_PK_ENCRYPTION_FUNC_DEF(encryptJni)(
         LOGE(" ## pkEncryptJni(): failure - invalid clear message");
         errorMessage = "invalid clear message";
     }
-    else if (!(plaintextPtr = env->GetByteArrayElements(aPlaintextBuffer, 0)))
+    else if (!(plaintextPtr = env->GetByteArrayElements(aPlaintextBuffer, &plaintextIsCopied)))
     {
         LOGE(" ## pkEncryptJni(): failure - plaintext JNI allocation OOM");
         errorMessage = "plaintext JNI allocation OOM";
@@ -269,6 +270,10 @@ JNIEXPORT jbyteArray OLM_PK_ENCRYPTION_FUNC_DEF(encryptJni)(
 
     if (plaintextPtr)
     {
+        if (plaintextIsCopied)
+        {
+            memset(plaintextPtr, 0, (size_t)env->GetArrayLength(aPlaintextBuffer));
+        }
         env->ReleaseByteArrayElements(aPlaintextBuffer, plaintextPtr, JNI_ABORT);
     }
 
@@ -561,6 +566,7 @@ JNIEXPORT jbyteArray OLM_PK_DECRYPTION_FUNC_DEF(decryptJni)(
         }
         if (plaintextPtr)
         {
+          memset(plaintextPtr, 0, maxPlaintextLength);
           free(plaintextPtr);
         }
     }

android/olm-sdk/src/main/jni/olm_session.cpp

@@ -472,6 +472,7 @@ JNIEXPORT jbyteArray OLM_SESSION_FUNC_DEF(encryptMessageJni)(JNIEnv *env, jobjec
 
     OlmSession *sessionPtr = getSessionInstanceId(env, thiz);
     jbyte *clearMsgPtr = NULL;
+    jboolean clearMsgIsCopied = JNI_FALSE;
     jclass encryptedMsgJClass = 0;
     jfieldID typeMsgFieldId;
 
@@ -490,8 +491,9 @@ JNIEXPORT jbyteArray OLM_SESSION_FUNC_DEF(encryptMessageJni)(JNIEnv *env, jobjec
     else if (!aEncryptedMsg)
     {
         LOGE("## encryptMessageJni(): failure - invalid encrypted message");
+        errorMessage = "invalid encrypted message";
     }
-    else if (!(clearMsgPtr = env->GetByteArrayElements(aClearMsgBuffer, 0)))
+    else if (!(clearMsgPtr = env->GetByteArrayElements(aClearMsgBuffer, &clearMsgIsCopied)))
     {
         LOGE("## encryptMessageJni(): failure - clear message JNI allocation OOM");
         errorMessage = "clear message JNI allocation OOM";
@@ -580,6 +582,10 @@ JNIEXPORT jbyteArray OLM_SESSION_FUNC_DEF(encryptMessageJni)(JNIEnv *env, jobjec
     // free alloc
     if (clearMsgPtr)
     {
+        if (clearMsgIsCopied)
+        {
+            memset(clearMsgPtr, 0, (size_t)env->GetArrayLength(aClearMsgBuffer));
+        }
         env->ReleaseByteArrayElements(aClearMsgBuffer, clearMsgPtr, JNI_ABORT);
     }
 
@@ -702,6 +708,8 @@ JNIEXPORT jbyteArray OLM_SESSION_FUNC_DEF(decryptMessageJni)(JNIEnv *env, jobjec
 
                 LOGD(" ## decryptMessageJni(): UTF-8 Conversion - decrypted returnedLg=%lu OK",static_cast<long unsigned int>(plaintextLength));
             }
+
+            memset(plainTextMsgPtr, 0, maxPlainTextLength);
         }
     }