From 55e029e81da377a621de5a8ea5d9e6a0206c592a Mon Sep 17 00:00:00 2001
From: jeffrey-signal <jeffrey@signal.org>
Date: Thu, 12 Mar 2026 17:33:54 -0400
Subject: [PATCH] Treat member labels as unset if they can't be decrypted.

---
 .../api/groupsv2/GroupsV2Operations.java      | 28 +++++++--
 ...roupsV2Operations_decrypt_change_Test.java | 58 +++++++++++++++++++
 2 files changed, 82 insertions(+), 4 deletions(-)

diff --git a/lib/libsignal-service/src/main/java/org/whispersystems/signalservice/api/groupsv2/GroupsV2Operations.java b/lib/libsignal-service/src/main/java/org/whispersystems/signalservice/api/groupsv2/GroupsV2Operations.java
index 79da821de5..d6112c893f 100644
--- a/lib/libsignal-service/src/main/java/org/whispersystems/signalservice/api/groupsv2/GroupsV2Operations.java
+++ b/lib/libsignal-service/src/main/java/org/whispersystems/signalservice/api/groupsv2/GroupsV2Operations.java
@@ -769,8 +769,8 @@ public final class GroupsV2Operations {
         modifyMemberLabels.add(
             new DecryptedModifyMemberLabel.Builder()
                 .aciBytes(decryptAciToBinary(action.userId))
-                .labelEmoji(Objects.requireNonNullElse(decryptString(action.labelEmoji), ""))
-                .labelString(Objects.requireNonNullElse(decryptString(action.labelString), ""))
+                .labelEmoji(decryptMemberLabelEmoji(action.labelEmoji))
+                .labelString(decryptMemberLabelText(action.labelString))
                 .build()
         );
       }
@@ -817,8 +817,8 @@ public final class GroupsV2Operations {
     private DecryptedMember.Builder decryptMember(Member member)
         throws InvalidGroupStateException, VerificationFailedException, InvalidInputException
     {
-      String labelEmoji  = Objects.requireNonNullElse(decryptString(member.labelEmoji), "");
-      String labelString = Objects.requireNonNullElse(decryptString(member.labelString), "");
+      String labelEmoji  = decryptMemberLabelEmoji(member.labelEmoji);
+      String labelString = decryptMemberLabelText(member.labelString);
 
       if (member.presentation.size() == 0) {
         ACI aci = decryptAci(member.userId);
@@ -1072,6 +1072,26 @@ public final class GroupsV2Operations {
       return new String(decryptedBytes, StandardCharsets.UTF_8);
     }
 
+    @Nonnull
+    private String decryptMemberLabelText(@Nullable ByteString cipherText) {
+      try {
+        return Objects.requireNonNullElse(decryptString(cipherText), "");
+      } catch (VerificationFailedException e) {
+        Log.w(TAG, "Failed to decrypt member label string, treating as unset");
+        return "";
+      }
+    }
+
+    @Nonnull
+    private String decryptMemberLabelEmoji(@Nullable ByteString cipherText) {
+      try {
+        return Objects.requireNonNullElse(decryptString(cipherText), "");
+      } catch (VerificationFailedException e) {
+        Log.w(TAG, "Failed to decrypt member label emoji, treating as unset");
+        return "";
+      }
+    }
+
     /**
      * Verifies signature and parses actions on a group change.
      */
diff --git a/lib/libsignal-service/src/test/java/org/whispersystems/signalservice/api/groupsv2/GroupsV2Operations_decrypt_change_Test.java b/lib/libsignal-service/src/test/java/org/whispersystems/signalservice/api/groupsv2/GroupsV2Operations_decrypt_change_Test.java
index 82cd0ef634..f60c256262 100644
--- a/lib/libsignal-service/src/test/java/org/whispersystems/signalservice/api/groupsv2/GroupsV2Operations_decrypt_change_Test.java
+++ b/lib/libsignal-service/src/test/java/org/whispersystems/signalservice/api/groupsv2/GroupsV2Operations_decrypt_change_Test.java
@@ -476,6 +476,64 @@ public final class GroupsV2Operations_decrypt_change_Test {
     );
   }
 
+  @Test
+  public void member_label_text_is_treated_as_unset_on_decryption_error_field26() {
+    ACI        aci          = ACI.from(UUID.fromString("d1d1d1d1-0000-4000-8000-000000000001"));
+    ByteString invalidBytes = ByteString.of(new byte[] { 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07 });
+
+    GroupChange.Actions.Builder change = new GroupChange.Actions.Builder()
+        .modifyMemberLabels(
+            List.of(
+                new GroupChange.Actions.ModifyMemberLabelAction.Builder()
+                    .userId(groupOperations.encryptServiceId(aci))
+                    .labelString(invalidBytes)
+                    .build()
+            )
+        );
+
+    DecryptedGroupChange.Builder expected = new DecryptedGroupChange.Builder()
+        .modifyMemberLabels(
+            List.of(
+                new DecryptedModifyMemberLabel.Builder()
+                    .aciBytes(aci.toByteString())
+                    .labelEmoji("")
+                    .labelString("")
+                    .build()
+            )
+        );
+
+    assertDecryption(change, expected);
+  }
+
+  @Test
+  public void member_label_emoji_is_treated_as_unset_on_decryption_error_field26() {
+    ACI        aci          = ACI.from(UUID.fromString("d1d1d1d1-0000-4000-8000-000000000001"));
+    ByteString invalidBytes = ByteString.of(new byte[] { 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07 });
+
+    GroupChange.Actions.Builder change = new GroupChange.Actions.Builder()
+        .modifyMemberLabels(
+            List.of(
+                new GroupChange.Actions.ModifyMemberLabelAction.Builder()
+                    .userId(groupOperations.encryptServiceId(aci))
+                    .labelEmoji(invalidBytes)
+                    .build()
+            )
+        );
+
+    DecryptedGroupChange.Builder expected = new DecryptedGroupChange.Builder()
+        .modifyMemberLabels(
+            List.of(
+                new DecryptedModifyMemberLabel.Builder()
+                    .aciBytes(aci.toByteString())
+                    .labelEmoji("")
+                    .labelString("")
+                    .build()
+            )
+        );
+
+    assertDecryption(change, expected);
+  }
+
   @Test
   public void can_pass_through_new_member_label_access_field_27() {
     GroupChange.Actions.Builder encryptedChange = groupOperations.createChangeMemberLabelRights(AccessControl.AccessRequired.ADMINISTRATOR);