sandbox: allow newfstatat

Testing on Arch x86_64, when connecting to the login server this syscall triggered the secomp filter

src/Email.cpp

@@ -252,11 +252,26 @@ static void emailSend(CNSocket* sock, CNPacketData* data) {
         if (attachment.ItemInven.iID == 0)
             continue;
 
+        sItemBase* item = &pkt->aItem[i].ItemInven;
+        sItemBase* real = &plr->Inven[attachment.iSlotNum];
+
         resp.aItem[i] = attachment;
         attachments.push_back(attachment.ItemInven);
         attSlots.push_back(attachment.iSlotNum);
-        // delete item
-        plr->Inven[attachment.iSlotNum] = { 0, 0, 0, 0 };
+        if (real->iOpt == item->iOpt) // delete item (if they attached the whole stack)
+            *real = { 0, 0, 0, 0 };
+        else // otherwise, decrement the item
+            real->iOpt -= item->iOpt;
+
+        // update the slot
+        INITSTRUCT(sP_FE2CL_PC_ITEM_MOVE_SUCC, itemResp);
+        itemResp.iFromSlotNum = attachment.iSlotNum;
+        itemResp.iToSlotNum = attachment.iSlotNum;
+        itemResp.FromSlotItem = *real;
+        itemResp.ToSlotItem = *real;
+        itemResp.eFrom = (int32_t)Items::SlotType::INVENTORY;
+        itemResp.eTo = (int32_t)Items::SlotType::INVENTORY;
+        sock->sendPacket(itemResp, P_FE2CL_PC_ITEM_MOVE_SUCC);
     }
 
     int cost = pkt->iCash + 50 + 20 * attachments.size(); // attached taros + postage

src/sandbox/seccomp.cpp

@@ -157,6 +157,7 @@ static sock_filter filter[] = {
     ALLOW_SYSCALL(stat),
 #endif
     ALLOW_SYSCALL(fstat),
+    ALLOW_SYSCALL(newfstatat),
     ALLOW_SYSCALL(fsync), // maybe
 #if __NR_creat
     ALLOW_SYSCALL(creat), // maybe; for DB journal