Core/PacketIO: Fix crash and exploit caused when client sends tampered mover guids

Closes: #4056

src/server/game/Entities/Player/Player.cpp

@@ -21731,6 +21731,8 @@ void Player::SendInitialPacketsBeforeAddToMap()
     // SMSG_PET_GUIDS
     // SMSG_UPDATE_WORLD_STATE
     // SMSG_POWER_UPDATE
+
+    SetMover(this);
 }
 
 void Player::SendInitialPacketsAfterAddToMap()

src/server/game/Server/Protocol/Handlers/MovementHandler.cpp

@@ -472,18 +472,7 @@ void WorldSession::HandleSetActiveMoverOpcode(WorldPacket &recv_data)
 
     if (GetPlayer()->IsInWorld())
     {
-        if (Unit* mover = ObjectAccessor::GetUnit(*GetPlayer(), guid))
+        if (_player->m_mover->GetGUID() != guid)
-        {
-            GetPlayer()->SetMover(mover);
-            if (mover != GetPlayer() && mover->canFly())
-            {
-                WorldPacket data(SMSG_MOVE_SET_CAN_FLY, 12);
-                data.append(mover->GetPackGUID());
-                data << uint32(0);
-                SendPacket(&data);
-            }
-        }
-        else
         {
             sLog->outError("HandleSetActiveMoverOpcode: incorrect mover guid: mover is " UI64FMTD " (%s - Entry: %u) and should be " UI64FMTD, guid, GetLogNameForGuid(guid), GUID_ENPART(guid), _player->m_mover->GetGUID());
             GetPlayer()->SetMover(GetPlayer());

src/server/game/Spells/Auras/SpellAuraEffects.cpp

@@ -3096,9 +3096,15 @@ void AuraEffect::HandleModPossess(AuraApplication const* aurApp, uint8 mode, boo
     }
 
     if (apply)
-        target->SetCharmedBy(caster, CHARM_TYPE_POSSESS, aurApp);
+    {
+        if (target->SetCharmedBy(caster, CHARM_TYPE_POSSESS, aurApp))
+            caster->ToPlayer()->SetMover(target);
+    }
     else
+    {
         target->RemoveCharmedBy(caster);
+        caster->ToPlayer()->SetMover(caster);
+    }
 }
 
 // only one spell has this aura
@@ -3126,11 +3132,13 @@ void AuraEffect::HandleModPossessPet(AuraApplication const* aurApp, uint8 mode,
         if (caster->ToPlayer()->GetPet() != pet)
             return;
 
-        pet->SetCharmedBy(caster, CHARM_TYPE_POSSESS, aurApp);
+        if (pet->SetCharmedBy(caster, CHARM_TYPE_POSSESS, aurApp))
+            caster->ToPlayer()->SetMover(pet);
     }
     else
     {
         pet->RemoveCharmedBy(caster);
+        caster->ToPlayer()->SetMover(caster);
 
         if (!pet->IsWithinDistInMap(caster, pet->GetMap()->GetVisibilityRange()))
             pet->Remove(PET_SAVE_NOT_IN_SLOT, true);
@@ -4807,7 +4815,7 @@ void AuraEffect::HandleAuraDummy(AuraApplication const* aurApp, uint8 mode, bool
                     if (Aura* newAura = target->AddAura(71564, target))
                         newAura->SetStackAmount(newAura->GetSpellInfo()->StackAmount);
                         break;
-                case 59628: // Tricks of the Trade  
+                case 59628: // Tricks of the Trade
                     if (caster && caster->GetMisdirectionTarget())
                         target->SetReducedThreatPercent(100, caster->GetMisdirectionTarget()->GetGUID());
                     break;
@@ -4970,7 +4978,7 @@ void AuraEffect::HandleAuraDummy(AuraApplication const* aurApp, uint8 mode, bool
                                 target->SetReducedThreatPercent(0,0);
                             else
                                 target->SetReducedThreatPercent(0,caster->GetMisdirectionTarget()->GetGUID());
-                            break;       
+                            break;
                     }
                 default:
                     break;