Improve envelope timestamp validation.

libsignal-service/src/main/java/org/whispersystems/signalservice/api/messages/EnvelopeContentValidator.kt

@@ -77,7 +77,7 @@ object EnvelopeContentValidator {
     }
 
     if (dataMessage.timestamp != envelope.timestamp) {
-      Result.Invalid("[DataMessage] Timestamps don't match! envelope: ${envelope.timestamp}, content: ${dataMessage.timestamp}")
+      return Result.Invalid("[DataMessage] Timestamps don't match! envelope: ${envelope.timestamp}, content: ${dataMessage.timestamp}")
     }
 
     if (dataMessage.quote != null && dataMessage.quote.authorAci.isNullOrInvalidAci()) {

libsignal-service/src/test/java/org/whispersystems/signalservice/api/messages/EnvelopeContentValidatorTest.kt

@@ -0,0 +1,35 @@
+/*
+ * Copyright 2025 Signal Messenger, LLC
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+package org.whispersystems.signalservice.api.messages
+
+import org.junit.Test
+import org.whispersystems.signalservice.api.push.ServiceId
+import org.whispersystems.signalservice.internal.push.Content
+import org.whispersystems.signalservice.internal.push.DataMessage
+import org.whispersystems.signalservice.internal.push.Envelope
+
+class EnvelopeContentValidatorTest {
+
+  companion object {
+    private val SELF_ACI = ServiceId.ACI.parseOrThrow("0a5ebe7e-9de7-41a5-a25f-6ace4f8e11d1")
+  }
+
+  @Test
+  fun `validate - ensure mismatched timestamps are marked invalid`() {
+    val envelope = Envelope(
+      timestamp = 1234
+    )
+
+    val content = Content(
+      dataMessage = DataMessage(
+        timestamp = 12345
+      )
+    )
+
+    val result = EnvelopeContentValidator.validate(envelope, content, SELF_ACI)
+    assert(result is EnvelopeContentValidator.Result.Invalid)
+  }
+}