Store encrypted messages on disk when receiving them

- Acknowledge to the server only after the message is stored.
- Delete the message when decrypting was successful

src/main/java/org/asamk/signal/Main.java

@@ -768,7 +768,7 @@ public class Main {
         }
 
         @Override
-        public void handleMessage(SignalServiceEnvelope envelope, SignalServiceContent content) {
+        public void handleMessage(SignalServiceEnvelope envelope, SignalServiceContent content, Throwable exception) {
             SignalServiceAddress source = envelope.getSourceAddress();
             ContactInfo sourceContact = m.getContact(source.getNumber());
             System.out.println(String.format("Envelope from: %s (device: %d)", (sourceContact == null ? "" : "“" + sourceContact.name + "” ") + source.getNumber(), envelope.getSourceDevice()));
@@ -780,6 +780,16 @@ public class Main {
             if (envelope.isReceipt()) {
                 System.out.println("Got receipt.");
             } else if (envelope.isSignalMessage() | envelope.isPreKeySignalMessage()) {
+                if (exception != null) {
+                    if (exception instanceof org.whispersystems.libsignal.UntrustedIdentityException) {
+                        org.whispersystems.libsignal.UntrustedIdentityException e = (org.whispersystems.libsignal.UntrustedIdentityException) exception;
+                        System.out.println("The user’s key is untrusted, either the user has reinstalled Signal or a third party sent this message.");
+                        System.out.println("Use 'signal-cli -u " + m.getUsername() + " listIdentities -n " + e.getName() + "', verify the key and run 'signal-cli -u " + m.getUsername() + " trust -v \"FINGER_PRINT\" " + e.getName() + "' to mark it as trusted");
+                        System.out.println("If you don't care about security, use 'signal-cli -u " + m.getUsername() + " trust -a " + e.getName() + "' to trust it without verification");
+                    } else {
+                        System.out.println("Exception: " + exception.getMessage() + " (" + exception.getClass().getSimpleName() + ")");
+                    }
+                }
                 if (content == null) {
                     System.out.println("Failed to decrypt message.");
                 } else {
@@ -904,8 +914,8 @@ public class Main {
         }
 
         @Override
-        public void handleMessage(SignalServiceEnvelope envelope, SignalServiceContent content) {
+        public void handleMessage(SignalServiceEnvelope envelope, SignalServiceContent content, Throwable exception) {
-            super.handleMessage(envelope, content);
+            super.handleMessage(envelope, content, exception);
 
             if (!envelope.isReceipt() && content != null && content.getDataMessage().isPresent()) {
                 SignalServiceDataMessage message = content.getDataMessage().get();

src/main/java/org/asamk/signal/Manager.java

@@ -133,6 +133,20 @@ class Manager implements Signal {
         return dataPath + "/" + username;
     }
 
+    private String getMessageCachePath() {
+        return this.dataPath + "/" + username + ".d/msg-cache";
+    }
+
+    private String getMessageCachePath(String sender) {
+        return getMessageCachePath() + "/" + sender.replace("/", "_");
+    }
+
+    private File getMessageCacheFile(String sender, long now, long timestamp) throws IOException {
+        String cachePath = getMessageCachePath(sender);
+        createPrivateDirectories(cachePath);
+        return new File(cachePath + "/" + now + "_" + timestamp);
+    }
+
     private static void createPrivateDirectories(String path) throws IOException {
         final Path file = new File(path).toPath();
         try {
@@ -778,11 +792,8 @@ class Manager implements Signal {
         try {
             return cipher.decrypt(envelope);
         } catch (org.whispersystems.libsignal.UntrustedIdentityException e) {
-            // TODO temporarily store message, until user has accepted the key
             signalProtocolStore.saveIdentity(e.getName(), e.getUntrustedIdentity(), TrustLevel.UNTRUSTED);
             throw e;
-        } catch (Exception e) {
-            throw e;
         }
     }
 
@@ -791,7 +802,7 @@ class Manager implements Signal {
     }
 
     public interface ReceiveMessageHandler {
-        void handleMessage(SignalServiceEnvelope envelope, SignalServiceContent decryptedContent);
+        void handleMessage(SignalServiceEnvelope envelope, SignalServiceContent decryptedContent, Throwable e);
     }
 
     private void handleSignalServiceDataMessage(SignalServiceDataMessage message, boolean isSync, String source, String destination) {
@@ -863,17 +874,56 @@ class Manager implements Signal {
             while (true) {
                 SignalServiceEnvelope envelope;
                 SignalServiceContent content = null;
+                Exception exception = null;
+                final long now = new Date().getTime();
                 try {
-                    envelope = messagePipe.read(timeoutSeconds, TimeUnit.SECONDS);
+                    envelope = messagePipe.read(timeoutSeconds, TimeUnit.SECONDS, new SignalServiceMessagePipe.MessagePipeCallback() {
+                        @Override
+                        public void onMessage(SignalServiceEnvelope envelope) {
+                            // store message on disk, before acknowledging receipt to the server
+                            try {
+                                File cacheFile = getMessageCacheFile(envelope.getSource(), now, envelope.getTimestamp());
+                                storeEnvelope(envelope, cacheFile);
+                            } catch (IOException e) {
+                                System.err.println("Failed to store encrypted message in disk cache, ignoring: " + e.getMessage());
+                            }
+                        }
+                    });
+                } catch (TimeoutException e) {
+                    if (returnOnTimeout)
+                        return;
+                    continue;
+                } catch (InvalidVersionException e) {
+                    System.err.println("Ignoring error: " + e.getMessage());
+                    continue;
+                }
                 if (!envelope.isReceipt()) {
-                        Exception exception;
                     try {
                         content = decryptMessage(envelope);
                     } catch (Exception e) {
                         exception = e;
-                            // TODO pass exception to handler instead
-                            e.printStackTrace();
                     }
+                    handleMessage(envelope, content);
+                }
+                save();
+                handler.handleMessage(envelope, content, exception);
+                if (exception == null || !(exception instanceof org.whispersystems.libsignal.UntrustedIdentityException)) {
+                    try {
+                        File cacheFile = getMessageCacheFile(envelope.getSource(), now, envelope.getTimestamp());
+                        cacheFile.delete();
+                    } catch (IOException e) {
+                        // Ignoring
+                        return;
+                    }
+                }
+            }
+        } finally {
+            if (messagePipe != null)
+                messagePipe.shutdown();
+        }
+    }
+
+    private void handleMessage(SignalServiceEnvelope envelope, SignalServiceContent content) {
         if (content != null) {
             if (content.getDataMessage().isPresent()) {
                 SignalServiceDataMessage message = content.getDataMessage().get();
@@ -890,14 +940,14 @@ class Manager implements Signal {
                     if (rm.isContactsRequest()) {
                         try {
                             sendContacts();
-                                        } catch (UntrustedIdentityException e) {
+                        } catch (UntrustedIdentityException | IOException e) {
                             e.printStackTrace();
                         }
                     }
                     if (rm.isGroupsRequest()) {
                         try {
                             sendGroups();
-                                        } catch (UntrustedIdentityException e) {
+                        } catch (UntrustedIdentityException | IOException e) {
                             e.printStackTrace();
                         }
                     }
@@ -949,18 +999,29 @@ class Manager implements Signal {
             }
         }
     }
-                    save();
+
-                    handler.handleMessage(envelope, content);
+    private void storeEnvelope(SignalServiceEnvelope envelope, File file) throws IOException {
-                } catch (TimeoutException e) {
+        try (FileOutputStream f = new FileOutputStream(file)) {
-                    if (returnOnTimeout)
+            DataOutputStream out = new DataOutputStream(f);
-                        return;
+            out.writeInt(1); // version
-                } catch (InvalidVersionException e) {
+            out.writeInt(envelope.getType());
-                    System.err.println("Ignoring error: " + e.getMessage());
+            out.writeUTF(envelope.getSource());
+            out.writeInt(envelope.getSourceDevice());
+            out.writeUTF(envelope.getRelay());
+            out.writeLong(envelope.getTimestamp());
+            if (envelope.hasContent()) {
+                out.writeInt(envelope.getContent().length);
+                out.write(envelope.getContent());
+            } else {
+                out.writeInt(0);
             }
+            if (envelope.hasLegacyMessage()) {
+                out.writeInt(envelope.getLegacyMessage().length);
+                out.write(envelope.getLegacyMessage());
+            } else {
+                out.writeInt(0);
             }
-        } finally {
+            out.close();
-            if (messagePipe != null)
-                messagePipe.shutdown();
         }
     }