add execution of modulefiles from a modulefile

Some modulefiles may execute another modulefile,
which may modify the PATH variable. This is
generally done with the dofile() or loadfile()
function, but they break out of the sandbox.
By redefining these functions so the file is
executed in the sandbox env, modulefiles can
be safely loaded from within another modulefile.

Author: JLague

src/lua/sandbox.lua

@@ -50,8 +50,22 @@ function getenv (...)
     if val then return val else return "" end
 end
 
+-- The bare minimum to check for PATH modifications in modulefiles
+test_env = {
+    pathJoin        = pathJoin,
+    prepend_path    = handle_path,
+    append_path     = handle_path,
+    os              = {getenv = getenv},
+    assert          = assert,
+    error           = error,
+    ipairs          = ipairs,
+    pairs           = pairs,
+}
+
 meta_table.__index  = fake_func
 
+-- These functions may get called if the modulefile tries to use a
+-- function which isn't defined in the test env
 local meta_obj = {
     __index     = fake_func,
     __call      = fake_func,
@@ -62,49 +76,59 @@ local meta_obj = {
     __le        = fake_compare,
 }
 
-test_env = {
-    pathJoin        = pathJoin,
-    prepend_path    = handle_path,
-    append_path     = handle_path,
-    os              = {getenv = getenv},
-    assert          = assert,
-    error           = error,
-}
-
 setmetatable(fake_obj, meta_obj)
 setmetatable(test_env, meta_table)
 
 --------------------------------------------------------------------------
--- This function is what actually "loads" a modulefile with protection
--- against modulefiles call functions they shouldn't or syntax errors
--- of any kind.
+-- Load the provided code in a sandbox environment and return it as a
+-- function. This function works with Lua 5.1.
 -- @param untrusted_code A string containing lua code
-
-local function run5_1(untrusted_code)
-    paths = {}
+local function loadcode5_1(untrusted_code)
     if untrusted_code:byte(1) == 27 then error("binary bytecode prohibited") end
     local untrusted_function, message = loadstring(untrusted_code)
     if not untrusted_function then error(message) end
     setfenv(untrusted_function, test_env)
-    untrusted_function()
-    return paths
+    return untrusted_function
 end
 
 --------------------------------------------------------------------------
--- This function is what actually "loads" a modulefile with protection
--- against modulefiles call functions they shouldn't or syntax errors
--- of any kind. This run codes under environment [Lua 5.2] or later.
+-- Load the provided code in a sandbox environment and return it as a
+-- function. This function works with Lua 5.2 or higher.
 -- @param untrusted_code A string containing lua code
-local function run5_2(untrusted_code)
-    paths = {}
+local function loadcode5_2(untrusted_code)
     local untrusted_function, message = load(untrusted_code, nil, 't', test_env)
     if not untrusted_function then error(message) end
-    untrusted_function()
-    return paths
+    return untrusted_function
 end
 
+loadcode = (_VERSION == "Lua 5.1") and loadcode5_1 or loadcode5_2
+
 --------------------------------------------------------------------------
--- Define two version: Lua 5.1 or 5.2.  It is likely that
--- The 5.2 version will be good for many new versions of
--- Lua but time will only tell.
-sandbox_run = (_VERSION == "Lua 5.1") and run5_1 or run5_2
+-- Read an entire file and load it's code as a function in a sandbox env.
+-- @param filename The name/path of the file to load
+function loadfile(filename)
+    local file = assert(io.open(filename, "r"))
+    local code = file:read("*a")
+    file:close()
+    return loadcode(code)
+end
+
+--------------------------------------------------------------------------
+-- Execute a lua file in a sandbox environment.
+-- @param filename The name/path of the file to load
+function dofile(filename)
+    return assert(loadfile(filename))()
+end
+
+-- add the functions to the sandbox env
+test_env.loadfile = loadfile
+test_env.dofile   = dofile
+
+--------------------------------------------------------------------------
+-- Load the provided code in a sandbox environment and execute it
+-- @param untrusted_code A string containing lua code
+function sandbox_run(untrusted_code)
+    paths = {}
+    loadcode(untrusted_code)()
+    return paths
+end