Repair broken session with preKeyMessage

smack-omemo-signal/src/main/java/org/jivesoftware/smackx/omemo/signal/SignalOmemoRatchet.java

@@ -107,7 +107,7 @@ public class SignalOmemoRatchet
                 throw new CryptoFailedException(e);
             }
             catch (InvalidKeyIdException e) {
-                throw new NoRawSessionException(e);
+                throw new NoRawSessionException(sender, e);
             }
             catch (DuplicateMessageException e) {
                 LOGGER.log(Level.INFO, "Decryption of PreKeyMessage from " + sender +
@@ -125,7 +125,7 @@ public class SignalOmemoRatchet
                 throw new AssertionError("Signals trust management MUST be disabled.");
             }
             catch (InvalidMessageException | NoSessionException e) {
-                throw new NoRawSessionException(e);
+                throw new NoRawSessionException(sender, e);
             }
             catch (LegacyMessageException e) {
                 throw new CryptoFailedException(e);

smack-omemo/src/main/java/org/jivesoftware/smackx/omemo/OmemoConfiguration.java

@@ -52,17 +52,9 @@ public final class OmemoConfiguration {
      */
     private static boolean ADD_OMEMO_HINT_BODY = true;
 
-    /**
+    private static boolean REPAIR_BROKEN_SESSIONS_WITH_PREKEY_MESSAGES = true;
-     * Add Explicit Message Encryption hint (XEP-0380) to the message.
-     * TODO: REMOVE
-     */
-    private static boolean ADD_EME_ENCRYPTION_HINT = true;
 
-    /**
+    private static boolean COMPLETE_SESSION_WITH_EMPTY_MESSAGE = true;
-     * Add MAM storage hint to allow the server to store messages that do not contain a body.
-     * TODO: REMOVE
-     */
-    private static boolean ADD_MAM_STORAGE_HINT = true;
 
     private static File FILE_BASED_OMEMO_STORE_DEFAULT_PATH = null;
 
@@ -104,14 +96,31 @@ public final class OmemoConfiguration {
         return DELETE_STALE_DEVICE_AFTER_HOURS;
     }
 
+    /**
+     * Decide, whether signed preKeys are automatically rotated or not.
+     * It is highly recommended to rotate signed preKeys to preserve forward secrecy.
+     *
+     * @param renew automatically rotate signed preKeys?
+     */
     public static void setRenewOldSignedPreKeys(boolean renew) {
         RENEW_OLD_SIGNED_PREKEYS = renew;
     }
 
+    /**
+     * Determine, whether signed preKeys are automatically rotated or not.
+     *
+     * @return auto-rotate signed preKeys?
+     */
     public static boolean getRenewOldSignedPreKeys() {
         return RENEW_OLD_SIGNED_PREKEYS;
     }
 
+    /**
+     * Set the interval in hours, after which the published signed preKey should be renewed.
+     * This value should be between one or two weeks.
+     *
+     * @param hours hours after which signed preKeys should be rotated.
+     */
     public static void setRenewOldSignedPreKeysAfterHours(int hours) {
         if (hours <= 0) {
             throw new IllegalArgumentException("Hours must be greater than 0.");
@@ -119,10 +128,23 @@ public final class OmemoConfiguration {
         RENEW_OLD_SIGNED_PREKEYS_AFTER_HOURS = hours;
     }
 
+    /**
+     * Get the interval in hours, after which the published signed preKey should be renewed.
+     * This value should be between one or two weeks.
+     *
+     * @return hours after which signed preKeys should be rotated.
+     */
     public static int getRenewOldSignedPreKeysAfterHours() {
         return RENEW_OLD_SIGNED_PREKEYS_AFTER_HOURS;
     }
 
+    /**
+     * Set the maximum number of signed preKeys that are cached until the oldest one gets deleted.
+     * This number should not be too small in order to prevent message loss, but also not too big
+     * to preserve forward secrecy.
+     *
+     * @param number number of cached signed preKeys.
+     */
     public static void setMaxNumberOfStoredSignedPreKeys(int number) {
         if (number <= 0) {
             throw new IllegalArgumentException("Number must be greater than 0.");
@@ -130,34 +152,33 @@ public final class OmemoConfiguration {
         MAX_NUMBER_OF_STORED_SIGNED_PREKEYS = number;
     }
 
+    /**
+     * Return the maximum number of signed preKeys that are cached until the oldest one gets deleted.
+     * @return max number of cached signed preKeys.
+     */
     public static int getMaxNumberOfStoredSignedPreKeys() {
         return MAX_NUMBER_OF_STORED_SIGNED_PREKEYS;
     }
 
+    /**
+     * Decide, whether an OMEMO message should carry a plaintext hint about OMEMO encryption.
+     * Eg. "I sent you an OMEMO encrypted message..."
+     *
+     * @param addHint shall we add a hint?
+     */
     public static void setAddOmemoHintBody(boolean addHint) {
         ADD_OMEMO_HINT_BODY = addHint;
     }
 
+    /**
+     * Determine, whether an OMEMO message should carry a plaintext hint about OMEMO encryption.
+     *
+     * @return true, if a hint is added to the message.
+     */
     public static boolean getAddOmemoHintBody() {
         return ADD_OMEMO_HINT_BODY;
     }
 
-    public static void setAddEmeEncryptionHint(boolean addHint) {
-        ADD_EME_ENCRYPTION_HINT = addHint;
-    }
-
-    public static boolean getAddEmeEncryptionHint() {
-        return ADD_EME_ENCRYPTION_HINT;
-    }
-
-    public static void setAddMAMStorageProcessingHint(boolean addStorageHint) {
-        ADD_MAM_STORAGE_HINT = addStorageHint;
-    }
-
-    public static boolean getAddMAMStorageProcessingHint() {
-        return ADD_MAM_STORAGE_HINT;
-    }
-
     public static void setFileBasedOmemoStoreDefaultPath(File path) {
         FILE_BASED_OMEMO_STORE_DEFAULT_PATH = path;
     }
@@ -165,4 +186,44 @@ public final class OmemoConfiguration {
     public static File getFileBasedOmemoStoreDefaultPath() {
         return FILE_BASED_OMEMO_STORE_DEFAULT_PATH;
     }
+
+    /**
+     * Determine, whether incoming messages, which have broken sessions should automatically be answered by an empty
+     * preKeyMessage in order to establish a new session.
+     *
+     * @return true if session should be repaired automatically.
+     */
+    public static boolean getRepairBrokenSessionsWithPreKeyMessages() {
+        return REPAIR_BROKEN_SESSIONS_WITH_PREKEY_MESSAGES;
+    }
+
+    /**
+     * Decide, whether incoming messages, which have broken sessions should automatically be answered by an empty
+     * preKeyMessage in order to establish a new session.
+     *
+     * @param repair repair sessions?
+     */
+    public static void setRepairBrokenSessionsWithPrekeyMessages(boolean repair) {
+        REPAIR_BROKEN_SESSIONS_WITH_PREKEY_MESSAGES = repair;
+    }
+
+    /**
+     * Determine, whether incoming preKeyMessages should automatically be answered by an empty message in order to
+     * complete the session.
+     *
+     * @return true if sessions should be completed.
+     */
+    public static boolean getCompleteSessionWithEmptyMessage() {
+        return COMPLETE_SESSION_WITH_EMPTY_MESSAGE;
+    }
+
+    /**
+     * Decide, whether incoming preKeyMessages should automatically be answered by an empty message in order to
+     * complete the session.
+     *
+     * @param complete complete the session or not
+     */
+    public static void setCompleteSessionWithEmptyMessage(boolean complete) {
+        COMPLETE_SESSION_WITH_EMPTY_MESSAGE = complete;
+    }
 }

smack-omemo/src/main/java/org/jivesoftware/smackx/omemo/OmemoRatchet.java

@@ -62,7 +62,7 @@ public abstract class OmemoRatchet<T_IdKeyPair, T_IdKey, T_PreKey, T_SigPreKey,
      * @return decrypted message key.
      *
      * @throws CorruptedOmemoKeyException
-     * @throws NoRawSessionException
+     * @throws NoRawSessionException when no double ratchet session was found.
      * @throws CryptoFailedException
      * @throws UntrustedOmemoIdentityException
      */

smack-omemo/src/main/java/org/jivesoftware/smackx/omemo/OmemoService.java

@@ -1087,7 +1087,9 @@ public abstract class OmemoService<T_IdKeyPair, T_IdKey, T_PreKey, T_SigPreKey,
         }
 
         OmemoMessage.Received decrypted;
+        BareJid sender;
 
+        try {
             MultiUserChat muc = getMuc(manager.getConnection(), stanza.getFrom());
             if (muc != null) {
                 Occupant occupant = muc.getOccupant(stanza.getFrom().asEntityFullJidIfPossible());
@@ -1099,8 +1101,9 @@ public abstract class OmemoService<T_IdKeyPair, T_IdKey, T_PreKey, T_SigPreKey,
                     return;
                 }
 
-            BareJid sender = occupantJid.asBareJid();
+                sender = occupantJid.asBareJid();
-            try {
+
+                // try is for this
                 decrypted = decryptMessage(managerGuard, sender, element, OmemoMessage.CARBON.NONE);
 
                 if (element.isMessageElement()) {
@@ -1108,14 +1111,10 @@ public abstract class OmemoService<T_IdKeyPair, T_IdKey, T_PreKey, T_SigPreKey,
                 } else {
                     manager.notifyOmemoMucKeyTransportMessageReceived(muc, stanza, decrypted);
                 }
-
-            } catch (CorruptedOmemoKeyException | CryptoFailedException | NoRawSessionException e) {
-                LOGGER.log(Level.WARNING, "Could not decrypt incoming message: ", e);
-            }
-
             } else {
-            BareJid sender = stanza.getFrom().asBareJid();
+                sender = stanza.getFrom().asBareJid();
-            try {
+
+                // and this
                 decrypted = decryptMessage(managerGuard, sender, element, OmemoMessage.CARBON.NONE);
 
                 if (element.isMessageElement()) {
@@ -1123,10 +1122,49 @@ public abstract class OmemoService<T_IdKeyPair, T_IdKey, T_PreKey, T_SigPreKey,
                 } else {
                     manager.notifyOmemoKeyTransportMessageReceived(stanza, decrypted);
                 }
-            } catch (CorruptedOmemoKeyException | CryptoFailedException | NoRawSessionException e) {
+            }
+        }
+        catch (NoRawSessionException e) {
+            OmemoDevice device = e.getDeviceWithoutSession();
+            LOGGER.log(Level.WARNING, "No raw session found for contact " + device + ". ", e);
+
+            if (OmemoConfiguration.getRepairBrokenSessionsWithPreKeyMessages()) {
+                repairBrokenSessionWithPreKeyMessage(managerGuard, device);
+            }
+        }
+            catch (CorruptedOmemoKeyException | CryptoFailedException e) {
             LOGGER.log(Level.WARNING, "Could not decrypt incoming message: ", e);
         }
     }
+
+    /**
+     * Fetch and process a fresh bundle and send an empty preKeyMessage in order to establish a fresh session.
+     *
+     * @param managerGuard authenticated OmemoManager.
+     * @param brokenDevice device which session broke.
+     */
+    private void repairBrokenSessionWithPreKeyMessage(OmemoManager.LoggedInOmemoManager managerGuard,
+                                                      OmemoDevice brokenDevice)
+    {
+        LOGGER.log(Level.WARNING, "Attempt to repair the session by sending a fresh preKey message to "
+                + brokenDevice);
+        OmemoManager manager = managerGuard.get();
+        try {
+            // Create fresh session and send new preKeyMessage.
+            buildFreshSessionWithDevice(manager.getConnection(), manager.getOwnDevice(), brokenDevice);
+            OmemoElement ratchetUpdate = createRatchetUpdateElement(managerGuard, brokenDevice);
+            Message m = new Message();
+            m.setTo(brokenDevice.getJid());
+            m.addExtension(ratchetUpdate);
+            manager.getConnection().sendStanza(m);
+
+        } catch (CannotEstablishOmemoSessionException | CorruptedOmemoKeyException e) {
+            LOGGER.log(Level.WARNING, "Unable to repair session with " + brokenDevice, e);
+        } catch (SmackException.NotConnectedException | InterruptedException | SmackException.NoResponseException e) {
+            LOGGER.log(Level.WARNING, "Could not fetch fresh bundle for " + brokenDevice, e);
+        } catch (CryptoFailedException | NoSuchAlgorithmException e) {
+            LOGGER.log(Level.WARNING, "Could not create PreKeyMessage", e);
+        }
     }
 
     /**

smack-omemo/src/main/java/org/jivesoftware/smackx/omemo/exceptions/NoRawSessionException.java

@@ -16,6 +16,8 @@
  */
 package org.jivesoftware.smackx.omemo.exceptions;
 
+import org.jivesoftware.smackx.omemo.internal.OmemoDevice;
+
 /**
  * Exception that gets thrown whenever a OmemoMessage arrives that no OmemoSession was found for to decrypt it.
  *
@@ -25,7 +27,14 @@ public class NoRawSessionException extends Exception {
 
     private static final long serialVersionUID = 3466888654338119954L;
 
-    public NoRawSessionException(Exception e) {
+    private final OmemoDevice device;
+
+    public NoRawSessionException(OmemoDevice device, Exception e) {
         super(e);
+        this.device = device;
+    }
+
+    public OmemoDevice getDeviceWithoutSession() {
+        return device;
     }
 }