[Tarantool-patches] [PATCH v2 2/2] box: protects box.cfg from raw data modification

[Olga Arkhangelskaia <arkholga@tarantool.org>]

Forbids the possibility of the raw modification for box.cfg table.
Now the only way to change table value is box.cfg{}.

Closes #2867
---
 src/box/lua/load_cfg.lua  | 14 +++++++++++++-
 test/box-tap/cfg.test.lua | 11 ++++++++++-
 2 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/src/box/lua/load_cfg.lua b/src/box/lua/load_cfg.lua
index 85617c8f0..27ac6bb77 100644
--- a/src/box/lua/load_cfg.lua
+++ b/src/box/lua/load_cfg.lua
@@ -533,12 +533,24 @@ local function load_cfg(cfg)
     end
     setmetatable(box, nil)
     box_configured = nil
-    box.cfg = setmetatable(cfg,
+
+    local actual = cfg
+    box.cfg = setmetatable({},
         {
             __newindex = function(table, index)
                 error('Attempt to modify a read-only table')
             end,
             __call = locked(reload_cfg),
+            __index = function (self, k)
+                return actual[k]
+            end,
+            __serialize = function() return actual end,
+            __pairs = function(self)
+                local function iter(actual, k)
+                    return next(actual, k)
+                end
+                return iter, actual, nil
+            end
         })
     private.cfg_load()
     for key, fun in pairs(dynamic_cfg) do
diff --git a/test/box-tap/cfg.test.lua b/test/box-tap/cfg.test.lua
index d529447bb..443dfafbc 100755
--- a/test/box-tap/cfg.test.lua
+++ b/test/box-tap/cfg.test.lua
@@ -6,7 +6,7 @@ local socket = require('socket')
 local fio = require('fio')
 local uuid = require('uuid')
 local msgpack = require('msgpack')
-test:plan(104)
+test:plan(105)
 
 --------------------------------------------------------------------------------
 -- Invalid values
@@ -592,6 +592,15 @@ box.cfg{read_only=true}
 ]]
 test:is(run_script(code), PANIC, "panic on bootstrapping a read-only instance as master")
 
+--
+-- gf-2867 raise on raw modifications of box.cfg values
+--
+code = [[
+box.cfg{}
+box.cfg["read_only"] = true
+]]
+
+test:is(run_script(code), PANIC, "attempt to modify a read-only table")
 
 test:check()
 os.exit(0)
-- 
2.20.1 (Apple Git-117)