Show and enforce the terminated state of a group

A group admin can permanently terminate a group. Afterwards the group is
read-only for everyone, not even an admin can send messages or start calls;
members keep access to the existing history. Other clients silently drop
messages sent to a terminated group.

Read the DecryptedGroup.terminated flag through GroupInfo.isTerminated() and:

- surface it in listGroups (json and plain text) and as the DBus IsTerminated
  group property
- refuse to send to a terminated group locally (messages, reactions, typing and
  group stories) rather than send one that other clients ignore
- drop incoming messages addressed to a terminated group

lib/src/main/java/org/asamk/signal/manager/api/Group.java

@@ -22,7 +22,8 @@ public record Group(
         GroupPermission permissionEditDetails,
         GroupPermission permissionSendMessage,
         boolean isMember,
-        boolean isAdmin
+        boolean isAdmin,
+        boolean isTerminated
 ) {
 
     public static Group from(
@@ -59,6 +60,7 @@ public record Group(
                 groupInfo.getPermissionEditDetails(),
                 groupInfo.getPermissionSendMessage(),
                 groupInfo.isMember(selfRecipientId),
-                groupInfo.isAdmin(selfRecipientId));
+                groupInfo.isAdmin(selfRecipientId),
+                groupInfo.isTerminated());
     }
 }

lib/src/main/java/org/asamk/signal/manager/helper/IncomingMessageHandler.java

@@ -837,6 +837,15 @@ public final class IncomingMessageHandler {
             return true;
         }
 
+        if (group.isTerminated()) {
+            return message == null
+                    || message.getBody().isPresent()
+                    || message.getAttachments().isPresent()
+                    || message.getQuote().isPresent()
+                    || message.getPreviews().isPresent()
+                    || message.getMentions().isPresent()
+                    || message.getSticker().isPresent();
+        }
         if (group.isAnnouncementGroup() && !group.isAdmin(recipientId)) {
             return message == null
                     || message.getBody().isPresent()

lib/src/main/java/org/asamk/signal/manager/helper/SendHelper.java

@@ -567,7 +567,7 @@ public class SendHelper {
         return results;
     }
 
-    private GroupInfo getGroupForSending(GroupId groupId) throws GroupNotFoundException, NotAGroupMemberException {
+    private GroupInfo getGroupForSending(GroupId groupId) throws GroupNotFoundException, NotAGroupMemberException, GroupSendingNotAllowedException {
         var g = context.getGroupHelper().getGroup(groupId);
         if (g == null) {
             throw new GroupNotFoundException(groupId);
@@ -575,6 +575,10 @@ public class SendHelper {
         if (!g.isMember(account.getSelfRecipientId())) {
             throw new NotAGroupMemberException(groupId, g.getTitle());
         }
+        if (g.isTerminated()) {
+            // Other clients drop messages sent to a terminated group.
+            throw new GroupSendingNotAllowedException(groupId, g.getTitle());
+        }
         if (!g.isProfileSharingEnabled()) {
             g.setProfileSharingEnabled(true);
             account.getGroupStore().updateGroup(g);

lib/src/main/java/org/asamk/signal/manager/internal/ManagerImpl.java

@@ -912,6 +912,10 @@ public class ManagerImpl implements Manager {
         if (!(groupInfo instanceof GroupInfoV2 groupInfoV2)) {
             throw new IOException("Stories are only supported for V2 groups");
         }
+        if (groupInfoV2.isTerminated()) {
+            // Other clients drop messages sent to a terminated group.
+            throw new IOException("Cannot send a story to a group that has been terminated");
+        }
 
         final var uploadedAttachment = context.getAttachmentHelper().uploadAttachment(attachment);
         final var groupContext = SignalServiceGroupV2.newBuilder(groupInfoV2.getMasterKey())

lib/src/main/java/org/asamk/signal/manager/storage/groups/GroupInfo.java

@@ -66,6 +66,8 @@ public sealed abstract class GroupInfo permits GroupInfoV1, GroupInfoV2 {
 
     public abstract boolean isAnnouncementGroup();
 
+    public abstract boolean isTerminated();
+
     public abstract GroupPermission getPermissionAddMember();
 
     public abstract GroupPermission getPermissionEditDetails();

lib/src/main/java/org/asamk/signal/manager/storage/groups/GroupInfoV1.java

@@ -113,6 +113,11 @@ public final class GroupInfoV1 extends GroupInfo {
         return false;
     }
 
+    @Override
+    public boolean isTerminated() {
+        return false;
+    }
+
     @Override
     public GroupPermission getPermissionAddMember() {
         return GroupPermission.EVERY_MEMBER;

lib/src/main/java/org/asamk/signal/manager/storage/groups/GroupInfoV2.java

@@ -211,6 +211,11 @@ public final class GroupInfoV2 extends GroupInfo {
         return this.group != null && this.group.isAnnouncementGroup == EnabledState.ENABLED;
     }
 
+    @Override
+    public boolean isTerminated() {
+        return this.group != null && Boolean.TRUE.equals(this.group.terminated);
+    }
+
     @Override
     public GroupPermission getPermissionAddMember() {
         final var accessControl = getAccessControl();

lib/src/test/java/org/asamk/signal/manager/storage/groups/GroupInfoTerminatedTest.java

@@ -0,0 +1,104 @@
+package org.asamk.signal.manager.storage.groups;
+
+import org.asamk.signal.manager.api.Group;
+import org.asamk.signal.manager.api.GroupId;
+import org.asamk.signal.manager.api.GroupIdV2;
+import org.asamk.signal.manager.groups.GroupUtils;
+import org.asamk.signal.manager.storage.recipients.RecipientAddress;
+import org.asamk.signal.manager.storage.recipients.RecipientId;
+import org.asamk.signal.manager.storage.recipients.RecipientResolver;
+import org.asamk.signal.manager.storage.recipients.TestRecipientId;
+import org.junit.jupiter.api.Test;
+import org.signal.core.models.ServiceId;
+import org.signal.libsignal.zkgroup.InvalidInputException;
+import org.signal.libsignal.zkgroup.groups.GroupMasterKey;
+import org.signal.storageservice.storage.protos.groups.local.DecryptedGroup;
+import org.whispersystems.signalservice.api.push.DistributionId;
+
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+class GroupInfoTerminatedTest {
+
+    private static final RecipientResolver UNUSED_RESOLVER = new RecipientResolver() {
+        @Override
+        public RecipientId resolveRecipient(final RecipientAddress address) {
+            throw new UnsupportedOperationException();
+        }
+
+        @Override
+        public RecipientId resolveRecipient(final long recipientId) {
+            throw new UnsupportedOperationException();
+        }
+
+        @Override
+        public RecipientId resolveRecipient(final String identifier) {
+            throw new UnsupportedOperationException();
+        }
+
+        @Override
+        public RecipientId resolveRecipient(final ServiceId serviceId) {
+            throw new UnsupportedOperationException();
+        }
+    };
+
+    private static GroupMasterKey masterKey() {
+        final var bytes = new byte[32];
+        for (int i = 0; i < bytes.length; i++) {
+            bytes[i] = (byte) (i + 1);
+        }
+        try {
+            return new GroupMasterKey(bytes);
+        } catch (InvalidInputException e) {
+            throw new AssertionError(e);
+        }
+    }
+
+    private static GroupInfoV2 groupV2(final DecryptedGroup group) {
+        final var masterKey = masterKey();
+        return new GroupInfoV2(GroupUtils.getGroupIdV2(masterKey),
+                masterKey,
+                group,
+                DistributionId.create(),
+                false,
+                false,
+                false,
+                null,
+                UNUSED_RESOLVER);
+    }
+
+    @Test
+    void v1GroupsAreNeverTerminated() {
+        final var group = new GroupInfoV1(GroupId.v1(new byte[16]));
+        assertFalse(group.isTerminated());
+    }
+
+    @Test
+    void v2ReadsTerminatedFlagFromDecryptedGroup() {
+        assertTrue(groupV2(new DecryptedGroup.Builder().terminated(true).build()).isTerminated());
+        assertFalse(groupV2(new DecryptedGroup.Builder().terminated(false).build()).isTerminated());
+        assertFalse(groupV2(new DecryptedGroup.Builder().build()).isTerminated());
+    }
+
+    @Test
+    void v2IsNotTerminatedWhenGroupStateMissing() {
+        final var masterKey = masterKey();
+        final var group = new GroupInfoV2(GroupUtils.getGroupIdV2(masterKey), masterKey, UNUSED_RESOLVER);
+        assertFalse(group.isTerminated());
+    }
+
+    @Test
+    void groupApiRecordCarriesTerminatedFromModel() {
+        final RecipientId self = TestRecipientId.createTestId(1);
+
+        final var terminated = Group.from(groupV2(new DecryptedGroup.Builder().terminated(true).build()),
+                recipientId -> null,
+                self);
+        assertTrue(terminated.isTerminated());
+
+        final var live = Group.from(groupV2(new DecryptedGroup.Builder().terminated(false).build()),
+                recipientId -> null,
+                self);
+        assertFalse(live.isTerminated());
+    }
+}

man/signal-cli-dbus.5.adoc

@@ -452,6 +452,7 @@ Groups have the following (case-sensitive) properties:
 * IsBlocked<b> : true=member will not receive group messages; false=not blocked
 * IsMember<b> (read-only) : always true (object path exists only for group members)
 * IsAdmin<b> (read-only) : true=member has admin privileges; false=not admin
+* IsTerminated<b> (read-only) : true=group was permanently ended by an admin; nobody (not even an admin) can send messages or start calls, sending is rejected locally
 * MessageExpirationTimer<i> : int32 representing message expiration time for group
 * Members<as> (read-only) : String array of group members' phone numbers
 * PendingMembers<as> (read-only) : String array of pending members' phone numbers

src/main/java/org/asamk/Signal.java

@@ -595,6 +595,7 @@ public interface Signal extends DBusInterface {
     @DBusProperty(name = "IsBlocked", type = Boolean.class)
     @DBusProperty(name = "IsMember", type = Boolean.class, access = DBusProperty.Access.READ)
     @DBusProperty(name = "IsAdmin", type = Boolean.class, access = DBusProperty.Access.READ)
+    @DBusProperty(name = "IsTerminated", type = Boolean.class, access = DBusProperty.Access.READ)
     @DBusProperty(name = "MessageExpirationTimer", type = Integer.class)
     @DBusProperty(name = "Members", type = String[].class, access = DBusProperty.Access.READ)
     @DBusProperty(name = "PendingMembers", type = String[].class, access = DBusProperty.Access.READ)

src/main/java/org/asamk/signal/commands/ListGroupsCommand.java

@@ -79,12 +79,13 @@ public class ListGroupsCommand implements JsonRpcLocalCommand {
             final var groupInviteLink = group.groupInviteLinkUrl();
 
             writer.println(
-                    "Id: {} Name: {} Description: {} Active: {} Blocked: {} Members: {} Pending members: {} Requesting members: {} Banned: {} Message expiration: {} Link: {}",
+                    "Id: {} Name: {} Description: {} Active: {} Blocked: {} Terminated: {} Members: {} Pending members: {} Requesting members: {} Banned: {} Message expiration: {} Link: {}",
                     group.groupId().toBase64(),
                     group.title(),
                     group.description(),
                     group.isMember(),
                     group.isBlocked(),
+                    group.isTerminated(),
                     resolveMembers(group.members()),
                     resolveMemberAddress(group.pendingMembers()),
                     resolveMemberAddress(group.requestingMembers()),
@@ -92,11 +93,12 @@ public class ListGroupsCommand implements JsonRpcLocalCommand {
                     group.messageExpirationTimer() == 0 ? "disabled" : group.messageExpirationTimer() + "s",
                     groupInviteLink == null ? '-' : groupInviteLink.getUrl());
         } else {
-            writer.println("Id: {} Name: {}  Active: {} Blocked: {}",
+            writer.println("Id: {} Name: {}  Active: {} Blocked: {} Terminated: {}",
                     group.groupId().toBase64(),
                     group.title(),
                     group.isMember(),
-                    group.isBlocked());
+                    group.isBlocked(),
+                    group.isTerminated());
         }
     }
 
@@ -133,7 +135,8 @@ public class ListGroupsCommand implements JsonRpcLocalCommand {
                             group.permissionAddMember().name(),
                             group.permissionEditDetails().name(),
                             group.permissionSendMessage().name(),
-                            groupInviteLink == null ? null : groupInviteLink.getUrl());
+                            groupInviteLink == null ? null : groupInviteLink.getUrl(),
+                            group.isTerminated());
                 }).toList();
                 jsonWriter.write(jsonGroups);
             }
@@ -161,7 +164,8 @@ public class ListGroupsCommand implements JsonRpcLocalCommand {
             String permissionAddMember,
             String permissionEditDetails,
             String permissionSendMessage,
-            String groupInviteLink
+            String groupInviteLink,
+            boolean isTerminated
     ) {}
 
     private record JsonGroupMemberAddress(String number, String uuid) {}

src/main/java/org/asamk/signal/dbus/DbusManagerImpl.java

@@ -871,7 +871,8 @@ public class DbusManagerImpl implements Manager {
                     GroupPermission.valueOf((String) group.get("PermissionEditDetails").getValue()),
                     GroupPermission.valueOf((String) group.get("PermissionSendMessage").getValue()),
                     (boolean) group.get("IsMember").getValue(),
-                    (boolean) group.get("IsAdmin").getValue());
+                    (boolean) group.get("IsAdmin").getValue(),
+                    group.get("IsTerminated") != null && (boolean) group.get("IsTerminated").getValue());
         } catch (GroupInviteLinkUrl.InvalidGroupLinkException | GroupInviteLinkUrl.UnknownGroupLinkVersionException e) {
             throw new AssertionError(e);
         }

src/main/java/org/asamk/signal/dbus/DbusSignalImpl.java

@@ -1308,6 +1308,7 @@ public class DbusSignalImpl implements Signal, AutoCloseable {
                             new DbusProperty<>("IsBlocked", () -> getGroup().isBlocked(), this::setIsBlocked),
                             new DbusProperty<>("IsMember", () -> getGroup().isMember()),
                             new DbusProperty<>("IsAdmin", () -> getGroup().isAdmin()),
+                            new DbusProperty<>("IsTerminated", () -> getGroup().isTerminated()),
                             new DbusProperty<>("MessageExpirationTimer",
                                     () -> getGroup().messageExpirationTimer(),
                                     this::setMessageExpirationTime),