Fix: don't accept unencrypted messages

client.go

@@ -186,7 +186,6 @@ func (c *Client) read_loop(ctx context.Context, pending []string) {
 
 func (c *Client) handle_incoming_text(s string) {
     if len(s) > 0 && s[0] == '/' {
-		// Ignore unknown commands after handshake for now.
         return
     }
 
@@ -205,16 +204,29 @@ func (c *Client) handle_incoming_text(s string) {
     session_id_bytes := c.state.SessionIdBytes
     c.mu.Unlock()
 
-	content := in.Content
+    // Enforce encryption after handshake.
+    if !in.IsEncrypted {
+        c.emit(Event{
+            Kind: EventError,
+            Err:  fmt.Errorf("received unencrypted message after handshake"),
+        })
+        return
+    }
 
-	if in.IsEncrypted {
-		plain, err := DecryptAESGCM(shared_key, session_id_bytes, in.Content, in.Salt, in.SeqNum, in.IsResponse)
+    plain, err := DecryptAESGCM(
+        shared_key,
+        session_id_bytes,
+        in.Content,
+        in.Salt,
+        in.SeqNum,
+        in.IsResponse,
+    )
     if err != nil {
         c.emit(Event{Kind: EventError, Err: err})
         return
     }
-		content = string(plain)
-	}
+
+    content := string(plain)
 
     c.mu.Lock()
     if in.SeqNum > c.state.SeqInMax {

client_test.go

@@ -55,6 +55,10 @@ var _ = Describe("Client", func() {
 			written := <-conn.write_ch
 			Expect(written).To(HavePrefix("/create:"))
 
+			// First complete handshake
+			conn.read_ch <- "/session:" + session_id + ":" + server_pub_b64 + ":" + salt_b64 + ":12:34"
+
+			// Then send encrypted history (now processed normally)
 			history_enc, err := sdk.EncryptAESGCM(shared_key, session_id_bytes, []byte("hist"), 10, false)
 			Expect(err).To(BeNil())
 
@@ -68,8 +72,6 @@ var _ = Describe("Client", func() {
 				"created_at":   int64(1),
 			})
 			conn.read_ch <- string(history_json)
-
-			conn.read_ch <- "/session:" + session_id + ":" + server_pub_b64 + ":" + salt_b64 + ":12:34"
 		}()
 
 		err = client.Connect(ctx, "")