core: shared group ID in group profile for relayed groups (#6716)

* rfc: add shared group ID to profile (the same as linkEntityId and sha256(rootKey))

* implement group ID

* fix

* update simplexmq

* line

* toGroupKeys

* fix test

* fix bot api

* check group ID in other cases

* fix

---------

Co-authored-by: Evgeny @ SimpleX Chat <259188159+evgeny-simplex@users.noreply.github.com>
Co-authored-by: spaced4ndy <8711996+spaced4ndy@users.noreply.github.com>

src/Simplex/Chat/Library/Commands.hs

@@ -2024,6 +2024,9 @@ processChatCommand vr nm = \case
           Nothing -> throwChatError $ CEException "failed to retrieve relays: no short link"
         (FixedLinkData {linkConnReq = mainCReq@(CRContactUri crData), linkEntityId, rootKey}, cData@(ContactLinkData _ UserContactData {owners, relays})) <- getShortLinkConnReq nm user sLnk
         groupSLinkData_ <- liftIO $ decodeLinkUserData cData
+        -- Validate link entity ID matches group profile's sharedGroupId (relay groups must have both)
+        forM_ groupSLinkData_ $ \GroupShortLinkData {groupProfile = GroupProfile {sharedGroupId}} ->
+          unless ((B64UrlByteString <$> linkEntityId) == sharedGroupId) $ throwChatError CEInvalidConnReq
         let publicGroupData_ = groupSLinkData_ >>= \GroupShortLinkData {publicGroupData} -> publicGroupData
             publicMemberCount_ = (\PublicGroupData {publicMemberCount} -> publicMemberCount) <$> publicGroupData_
         -- Prepare group record once before connecting to relays (updatePreparedRelayedGroup):
@@ -2382,11 +2385,13 @@ processChatCommand vr nm = \case
       prepareGroupLink user = do
         gVar <- asks random
         groupLinkId <- GroupLinkId <$> drgRandomBytes 16
-        sharedGroupId <- drgRandomBytes 24
         subMode <- chatReadVar subscriptionMode
-        let crClientData = encodeJSON $ CRDataGroup groupLinkId
-        -- prepare link with sharedGroupId as linkEntityId (no server request)
-        ((_, rootPrivKey), ccLink, preparedParams) <- withAgent $ \a -> prepareConnectionLink a (aUserId user) (Just sharedGroupId) True (Just crClientData)
+        -- generate root key pair; entity ID = sha256(rootPubKey) — see docs/rfcs/2026-03-28-group-identity-binding.md
+        rootKey@(rootPubKey, rootPrivKey) <- liftIO $ atomically $ C.generateKeyPair gVar
+        let entityId = C.sha256Hash $ C.pubKeyBytes rootPubKey
+            crClientData = encodeJSON $ CRDataGroup groupLinkId
+        -- prepare link with entityId as linkEntityId (no server request)
+        (ccLink, preparedParams) <- withAgent $ \a -> prepareConnectionLink a (aUserId user) rootKey entityId True (Just crClientData)
         ccLink' <- createdChannelLink <$> shortenCreatedLink ccLink
         sLnk <- case toShortLinkContact ccLink' of
           Just sl -> pure sl
@@ -2394,12 +2399,12 @@ processChatCommand vr nm = \case
         -- generate owner key, OwnerAuth signed by root key
         memberId <- MemberId <$> liftIO (encodedRandomBytes gVar 12)
         (memberPrivKey, ownerAuth) <- liftIO $ SL.newOwnerAuth gVar (unMemberId memberId) rootPrivKey
-        let groupProfile' = (groupProfile :: GroupProfile) {groupLink = Just sLnk}
+        let groupProfile' = (groupProfile :: GroupProfile) {groupLink = Just sLnk, sharedGroupId = Just $ B64UrlByteString entityId}
             userData = encodeShortLinkData $ GroupShortLinkData {groupProfile = groupProfile', publicGroupData = Just (PublicGroupData 1)}
             userLinkData = UserContactLinkData UserContactData {direct = False, owners = [ownerAuth], relays = [], userData}
         -- create connection with prepared link (single network call)
         connId <- withAgent $ \a -> createConnectionForLink a nm (aUserId user) True ccLink preparedParams userLinkData IKPQOff subMode
-        let groupKeys = GroupKeys {sharedGroupId = B64UrlByteString sharedGroupId, groupRootKey = GRKPrivate rootPrivKey, memberPrivKey}
+        let groupKeys = GroupKeys {sharedGroupId = B64UrlByteString entityId, groupRootKey = GRKPrivate rootPrivKey, memberPrivKey}
             setupLink gInfo = do
               -- TODO [relays] starting role should be communicated in protocol from owner to relays
               subRole <- asks $ channelSubscriberRole . config
@@ -3894,6 +3899,10 @@ processChatCommand vr nm = \case
                 let FixedLinkData {linkConnReq = cReq, linkEntityId} = fd
                     linkInfo = GroupShortLinkInfo {direct, groupRelays = relays, sharedGroupId = B64UrlByteString <$> linkEntityId}
                 groupSLinkData_ <- liftIO $ decodeLinkUserData cData
+                -- Validate link entity ID matches group profile's sharedGroupId
+                forM_ groupSLinkData_ $ \GroupShortLinkData {groupProfile = GroupProfile {sharedGroupId}} ->
+                  unless ((B64UrlByteString <$> linkEntityId) == sharedGroupId) $
+                    throwChatError CEInvalidConnReq
                 plan <- groupJoinRequestPlan user cReq (Just linkInfo) groupSLinkData_
                 pure (con cReq, plan)
             where
@@ -5086,7 +5095,7 @@ chatCommandP =
                 { directMessages = Just DirectMessagesGroupPreference {enable = FEOn, role = Nothing},
                   history = Just HistoryGroupPreference {enable = FEOn}
                 }
-      pure GroupProfile {displayName = gName, fullName = "", shortDescr, description = Nothing, image = Nothing, groupLink = Nothing, groupPreferences, memberAdmission = Nothing}
+      pure GroupProfile {displayName = gName, fullName = "", shortDescr, description = Nothing, image = Nothing, groupLink = Nothing, groupPreferences, memberAdmission = Nothing, sharedGroupId = Nothing}
     memberCriteriaP = ("all" $> Just MCAll) <|> ("off" $> Nothing)
     shortDescrP = do
       descr <- A.takeWhile1 isSpace *> (T.dropWhileEnd isSpace <$> textP) <|> pure ""

src/Simplex/Chat/Library/Internal.hs

@@ -1055,7 +1055,7 @@ acceptRelayJoinRequestAsync
 
 businessGroupProfile :: Profile -> GroupPreferences -> GroupProfile
 businessGroupProfile Profile {displayName, fullName, shortDescr, image} groupPreferences =
-  GroupProfile {displayName, fullName, description = Nothing, shortDescr, image, groupLink = Nothing, groupPreferences = Just groupPreferences, memberAdmission = Nothing}
+  GroupProfile {displayName, fullName, description = Nothing, shortDescr, image, groupLink = Nothing, groupPreferences = Just groupPreferences, memberAdmission = Nothing, sharedGroupId = Nothing}
 
 introduceToModerators :: VersionRangeChat -> User -> GroupInfo -> GroupMember -> CM ()
 introduceToModerators vr user gInfo@GroupInfo {groupId} m@GroupMember {memberRole, memberId} = do
@@ -1882,9 +1882,9 @@ createSndMessages idsEvents = do
           encodeChatMessage maxEncodedMsgLength ChatMessage {chatVRange = vr, msgId = Just sharedMsgId, chatMsgEvent = evnt}
 
 groupMsgSigning :: GroupInfo -> ChatMsgEvent e -> Maybe MsgSigning
-groupMsgSigning gInfo@GroupInfo {membership = GroupMember {memberId}, groupKeys = Just GroupKeys {groupRootKey, memberPrivKey}} evt
+groupMsgSigning gInfo@GroupInfo {membership = GroupMember {memberId}, groupKeys = Just GroupKeys {sharedGroupId, memberPrivKey}} evt
   | useRelays' gInfo && requiresSignature (toCMEventTag evt) =
-      Just $ MsgSigning CBGroup (smpEncode (groupRootPubKey groupRootKey, memberId)) KRMember memberPrivKey
+      Just $ MsgSigning CBGroup (smpEncode (sharedGroupId, memberId)) KRMember memberPrivKey
 groupMsgSigning _ _ = Nothing
 
 sendGroupMemberMessages :: forall e. MsgEncodingI e => User -> GroupInfo -> Connection -> NonEmpty (ChatMsgEvent e) -> CM ()

src/Simplex/Chat/Library/Subscriber.hs

@@ -746,14 +746,16 @@ processAgentMessageConn vr user@User {userId} corrId agentConnId agentMessage =
               _ -> messageError "CONF from invited member must have x.grp.acpt"
           GCHostMember ->
             case chatMsgEvent of
-              XGrpLinkInv glInv -> do
-                -- XGrpLinkInv here means we are connecting via prepared group, and we have to update user and host member records
-                (gInfo', m') <- withStore $ \db -> updatePreparedUserAndHostMembersInvited db vr user gInfo m glInv
-                -- [incognito] send saved profile
-                incognitoProfile <- forM customUserProfileId $ \pId -> withStore (\db -> getProfileById db userId pId)
-                let profileToSend = userProfileInGroup user gInfo (fromLocalProfile <$> incognitoProfile)
-                allowAgentConnectionAsync user conn' confId $ XInfo profileToSend
-                toView $ CEvtGroupLinkConnecting user gInfo' m'
+              XGrpLinkInv glInv@GroupLinkInvitation {groupProfile = GroupProfile {sharedGroupId = rcvGId}}
+                | let GroupInfo {groupProfile = GroupProfile {sharedGroupId = curGId}} = gInfo, rcvGId == curGId -> do
+                    -- XGrpLinkInv here means we are connecting via prepared group, and we have to update user and host member records
+                    (gInfo', m') <- withStore $ \db -> updatePreparedUserAndHostMembersInvited db vr user gInfo m glInv
+                    -- [incognito] send saved profile
+                    incognitoProfile <- forM customUserProfileId $ \pId -> withStore (\db -> getProfileById db userId pId)
+                    let profileToSend = userProfileInGroup user gInfo (fromLocalProfile <$> incognitoProfile)
+                    allowAgentConnectionAsync user conn' confId $ XInfo profileToSend
+                    toView $ CEvtGroupLinkConnecting user gInfo' m'
+                | otherwise -> messageError "x.grp.link.inv: sharedGroupId mismatch"
               XGrpLinkReject glRjct@GroupLinkRejection {rejectionReason} -> do
                 (gInfo', m') <- withStore $ \db -> updatePreparedUserAndHostMembersRejected db vr user gInfo m glRjct
                 toView $ CEvtGroupLinkConnecting user gInfo' m'
@@ -3054,8 +3056,10 @@ processAgentMessageConn vr user@User {userId} corrId agentConnId agentMessage =
       toView $ CEvtGroupDeleted user gInfo'' {membership = membership {memberStatus = GSMemGroupDeleted}} m' msgSigned
 
     xGrpInfo :: GroupInfo -> GroupMember -> GroupProfile -> RcvMessage -> UTCTime -> CM (Maybe DeliveryJobScope)
-    xGrpInfo g@GroupInfo {groupProfile = p, businessChat} m@GroupMember {memberRole} p' msg@RcvMessage {msgSigned} brokerTs
+    xGrpInfo g@GroupInfo {groupProfile = p@GroupProfile {sharedGroupId = gId}, businessChat} m@GroupMember {memberRole} p'@GroupProfile {sharedGroupId = gId'} msg@RcvMessage {msgSigned} brokerTs
       | memberRole < GROwner = messageError "x.grp.info with insufficient member permissions" $> Nothing
+      | useRelays' g && gId' /= gId = messageError "x.grp.info: sharedGroupId cannot be changed" $> Nothing
+      | not (useRelays' g) && isJust gId' = messageError "x.grp.info: sharedGroupId not allowed in p2p groups" $> Nothing
       | otherwise = do
           case businessChat of
             Nothing -> unless (p == p') $ do
@@ -3233,8 +3237,8 @@ processAgentMessageConn vr user@User {userId} corrId agentConnId agentMessage =
           Just sm@SignedMsg {chatBinding, signatures, signedBody}
             | GroupMember {memberPubKey = Just pubKey, memberId} <- member ->
                 case chatBinding of
-                  CBGroup | Just GroupKeys {groupRootKey} <- groupKeys gInfo ->
-                    let prefix = smpEncode chatBinding <> smpEncode (groupRootPubKey groupRootKey, memberId)
+                  CBGroup | Just GroupKeys {sharedGroupId} <- groupKeys gInfo ->
+                    let prefix = smpEncode chatBinding <> smpEncode (sharedGroupId, memberId)
                      in signed MSSVerified <$ guard (all (\(MsgSignature KRMember sig) -> C.verify (C.APublicVerifyKey C.SEd25519 pubKey) sig (prefix <> signedBody)) signatures)
                   _ -> signed MSSSignedNoKey <$ guard signatureOptional
             | otherwise -> signed MSSSignedNoKey <$ guard (signatureOptional || unverifiedAllowed membership member tag)
@@ -3609,7 +3613,9 @@ runRelayRequestWorker a Worker {doWork} = do
               (FixedLinkData {linkEntityId, rootKey}, cData@(ContactLinkData _ UserContactData {owners})) <- getShortLinkConnReq NRMBackground user reqGroupLink
               liftIO (decodeLinkUserData cData) >>= \case
                 Nothing -> throwChatError $ CEException "getLinkDataCreateRelayLink: no group link data"
-                Just GroupShortLinkData {groupProfile = gp} -> do
+                Just GroupShortLinkData {groupProfile = gp@GroupProfile {sharedGroupId}} -> do
+                  unless ((B64UrlByteString <$> linkEntityId) == sharedGroupId) $
+                    throwChatError $ CEException "getLinkDataCreateRelayLink: linkEntityId does not match profile sharedGroupId"
                   validateGroupProfile gp
                   gVar <- asks random
                   (_, memberPrivKey) <- liftIO $ atomically $ C.generateKeyPair gVar

src/Simplex/Chat/Store/Groups.hs

@@ -1459,7 +1459,8 @@ createRelayRequestGroup db vr user@User {userId} GroupRelayInvitation {fromMembe
           image = Nothing,
           groupLink = Nothing,
           groupPreferences = Nothing,
-          memberAdmission = Nothing
+          memberAdmission = Nothing,
+          sharedGroupId = Nothing
         }
   (groupId, _groupLDN) <- createGroup_ db userId placeholderProfile Nothing Nothing True (Just RSInvited) Nothing currentTs
   -- Store relay request data for recovery
@@ -2227,7 +2228,7 @@ updateGroupProfileFromMember db user g@GroupInfo {groupId} Profile {displayName
           |]
             (Only groupId)
     toGroupProfile (displayName, fullName, shortDescr, description, image, groupLink, groupPreferences, memberAdmission) =
-      GroupProfile {displayName, fullName, shortDescr, description, image, groupLink, groupPreferences, memberAdmission}
+      GroupProfile {displayName, fullName, shortDescr, description, image, groupLink, groupPreferences, memberAdmission, sharedGroupId = Nothing}
 
 getGroupInfoByUserContactLinkConnReq :: DB.Connection -> VersionRangeChat -> User -> (ConnReqContact, ConnReqContact) -> IO (Maybe GroupInfo)
 getGroupInfoByUserContactLinkConnReq db vr user@User {userId} (cReqSchema1, cReqSchema2) = do

src/Simplex/Chat/Store/Shared.hs

@@ -676,11 +676,12 @@ toGroupInfo vr userContactId chatTags ((groupId, localDisplayName, displayName,
   let membership = (toGroupMember userContactId userMemberRow) {memberChatVRange = vr}
       chatSettings = ChatSettings {enableNtfs = fromMaybe MFAll enableNtfs_, sendRcpts = unBI <$> sendRcpts, favorite}
       fullGroupPreferences = mergeGroupPreferences groupPreferences
-      groupProfile = GroupProfile {displayName, fullName, shortDescr, description, image, groupPreferences, memberAdmission, groupLink}
+      groupKeys = toGroupKeys groupKeysRow
+      sharedGroupId = (\GroupKeys {sharedGroupId = gId} -> gId) <$> groupKeys
+      groupProfile = GroupProfile {displayName, fullName, shortDescr, description, image, groupPreferences, memberAdmission, groupLink, sharedGroupId}
       businessChat = toBusinessChatInfo businessRow
       preparedGroup = toPreparedGroup preparedGroupRow
       groupSummary = GroupSummary {currentMembers, publicMemberCount}
-      groupKeys = toGroupKeys groupKeysRow
    in GroupInfo {groupId, useRelays = BoolDef useRelays, relayOwnStatus, localDisplayName, groupProfile, localAlias, businessChat, fullGroupPreferences, membership, chatSettings, createdAt, updatedAt, chatTs, userMemberProfileSentAt, preparedGroup, chatTags, chatItemTTL, uiThemes, groupSummary, customData, membersRequireAttention, viaGroupLinkUri, groupKeys}
 
 toPreparedGroup :: PreparedGroupRow -> Maybe PreparedGroup

src/Simplex/Chat/Types.hs

@@ -151,7 +151,7 @@ data NewUser = NewUser
 
 newtype B64UrlByteString = B64UrlByteString ByteString
   deriving (Eq, Show)
-  deriving newtype (FromField)
+  deriving newtype (FromField, Encoding)
 
 instance ToField B64UrlByteString where toField (B64UrlByteString m) = toField $ Binary m
 
@@ -764,7 +764,8 @@ data GroupProfile = GroupProfile
     image :: Maybe ImageData,
     groupLink :: Maybe ShortLinkContact,
     groupPreferences :: Maybe GroupPreferences,
-    memberAdmission :: Maybe GroupMemberAdmission
+    memberAdmission :: Maybe GroupMemberAdmission,
+    sharedGroupId :: Maybe B64UrlByteString -- group identity = sha256(genesis root key), immutable
   }
   deriving (Eq, Show)