figure out fallbacks with omemo source id

3 files changed, 55 insertions, 3 deletions

diff --git a/src/main/java/de/pixart/messenger/crypto/axolotl/AxolotlService.java b/src/main/java/de/pixart/messenger/crypto/axolotl/AxolotlService.java
index d23e3a88b..ed432bb9b 100644
--- a/src/main/java/de/pixart/messenger/crypto/axolotl/AxolotlService.java
+++ b/src/main/java/de/pixart/messenger/crypto/axolotl/AxolotlService.java
@@ -206,6 +206,19 @@ public class AxolotlService implements OnAdvancedStreamFeaturesLoaded {
             this.fillMap(store);
         }
 
+        public Set<Jid> findCounterpartsForSourceId(Integer sid) {
+            Set<Jid> candidates = new HashSet<>();
+            synchronized (MAP_LOCK) {
+                for (Map.Entry<String, Map<Integer, XmppAxolotlSession>> entry : map.entrySet()) {
+                    String key = entry.getKey();
+                    if (entry.getValue().containsKey(sid)) {
+                        candidates.add(Jid.of(key));
+                    }
+                }
+            }
+            return candidates;
+        }
+
         private void putDevicesForJid(String bareJid, List<Integer> deviceIds, SQLiteAxolotlStore store) {
             for (Integer deviceId : deviceIds) {
                 SignalProtocolAddress axolotlAddress = new SignalProtocolAddress(bareJid, deviceId);
@@ -316,6 +329,10 @@ public class AxolotlService implements OnAdvancedStreamFeaturesLoaded {
         return keys;
     }
 
+    public Set<Jid> findCounterpartsBySourceId(int sid) {
+        return sessions.findCounterpartsForSourceId(sid);
+    }
+
     public long getNumTrustedKeys(Jid jid) {
         return axolotlStore.getContactNumTrustedKeys(jid.asBareJid().toString());
     }
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 603eedde8..f5a41e6b3 100644
--- a/src/main/java/de/pixart/messenger/crypto/axolotl/XmppAxolotlMessage.java
+++ b/src/main/java/de/pixart/messenger/crypto/axolotl/XmppAxolotlMessage.java
@@ -88,6 +88,18 @@ public class XmppAxolotlMessage {
         }
     }
 
+    public static int parseSourceId(final Element axolotlMessage) throws IllegalArgumentException {
+        final Element header = axolotlMessage.findChild(HEADER);
+        if (header == null) {
+            throw new IllegalArgumentException("No header found");
+        }
+        try {
+            return Integer.parseInt(header.getAttribute(SOURCEID));
+        } catch (NumberFormatException e) {
+            throw new IllegalArgumentException("invalid source id");
+        }
+    }
+
     private XmppAxolotlMessage(final Element axolotlMessage, final Jid from) throws IllegalArgumentException {
         this.from = from;
         Element header = axolotlMessage.findChild(HEADER);
diff --git a/src/main/java/de/pixart/messenger/parser/MessageParser.java b/src/main/java/de/pixart/messenger/parser/MessageParser.java
index e908ae0e1..8dad92356 100644
--- a/src/main/java/de/pixart/messenger/parser/MessageParser.java
+++ b/src/main/java/de/pixart/messenger/parser/MessageParser.java
@@ -11,6 +11,7 @@ import net.java.otr4j.session.SessionStatus;
 import java.text.SimpleDateFormat;
 import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.Date;
 import java.util.List;
 import java.util.Locale;
@@ -472,17 +473,39 @@ public class MessageParser extends AbstractParser implements OnMessagePacketRece
                 message = new Message(conversation, pgpEncrypted, Message.ENCRYPTION_PGP, status);
             } else if (axolotlEncrypted != null && Config.supportOmemo()) {
                 Jid origin;
+                Set<Jid> fallbacksBySourceId = Collections.emptySet();
                 if (conversationMultiMode) {
                     final Jid fallback = conversation.getMucOptions().getTrueCounterpart(counterpart);
                     origin = getTrueCounterpart(query != null ? mucUserElement : null, fallback);
                     if (origin == null) {
-                        Log.d(Config.LOGTAG, "axolotl message in non anonymous conference received");
+                        try {
+                            fallbacksBySourceId = account.getAxolotlService().findCounterpartsBySourceId(XmppAxolotlMessage.parseSourceId(axolotlEncrypted));
+                        } catch (IllegalArgumentException e) {
+                            //ignoring
+                        }
+                    }
+                    if (origin == null && fallbacksBySourceId.size() == 0) {
+                        Log.d(Config.LOGTAG, "axolotl message in anonymous conference received and no possible fallbacks");
                         return;
                     }
                 } else {
+                    fallbacksBySourceId = Collections.emptySet();
                     origin = from;
                 }
-                message = parseAxolotlChat(axolotlEncrypted, origin, conversation, status, query != null);
+                if (origin != null) {
+                    message = parseAxolotlChat(axolotlEncrypted, origin, conversation, status, query != null);
+                } else {
+                    Message trial = null;
+                    for (Jid fallback : fallbacksBySourceId) {
+                        trial = parseAxolotlChat(axolotlEncrypted, fallback, conversation, status, query != null);
+                        if (trial != null) {
+                            Log.d(Config.LOGTAG, account.getJid().asBareJid() + ": decoded muc message using fallback");
+                            origin = fallback;
+                            break;
+                        }
+                    }
+                    message = trial;
+                }
                 if (message == null) {
                     if (query == null && extractChatState(mXmppConnectionService.find(account, counterpart.asBareJid()), isTypeGroupChat, packet)) {
                         mXmppConnectionService.updateConversationUi();
@@ -686,7 +709,7 @@ public class MessageParser extends AbstractParser implements OnMessagePacketRece
                     final Jid fallback = conversation.getMucOptions().getTrueCounterpart(counterpart);
                     origin = getTrueCounterpart(query != null ? mucUserElement : null, fallback);
                     if (origin == null) {
-                        Log.d(Config.LOGTAG, "omemo key transport message in non anonymous conference received");
+                        Log.d(Config.LOGTAG, "omemo key transport message in anonymous conference received");
                         return;
                     }
                 } else if (isTypeGroupChat) {