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Isolate library tables between sandbox and insecure env

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sfan5 2021-03-28 22:53:48 +02:00
parent 52c0384bd1
commit 623f0a8613
1 changed files with 43 additions and 1 deletions
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44
src/script/cpp_api/s_security.cpp
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@ -45,6 +45,21 @@ static inline void copy_safe(lua_State *L, const char *list[], unsigned len, int
} }
} }
static void shallow_copy_table(lua_State *L, int from=-2, int to=-1)
{
if (from < 0) from = lua_gettop(L) + from + 1;
if (to < 0) to = lua_gettop(L) + to + 1;
lua_pushnil(L);
while (lua_next(L, from) != 0) {
assert(lua_type(L, -1) != LUA_TTABLE);
// duplicate key and value for lua_rawset
lua_pushvalue(L, -2);
lua_pushvalue(L, -2);
lua_rawset(L, to);
lua_pop(L, 1);
}
}
// Pushes the original version of a library function on the stack, from the old version // Pushes the original version of a library function on the stack, from the old version
static inline void push_original(lua_State *L, const char *lib, const char *func) static inline void push_original(lua_State *L, const char *lib, const char *func)
{ {
@ -83,7 +98,10 @@ void ScriptApiSecurity::initializeSecurity()
"unpack", "unpack",
"_VERSION", "_VERSION",
"xpcall", "xpcall",
// Completely safe libraries };
static const char *whitelist_tables[] = {
// These libraries are completely safe BUT we need to duplicate their table
// to ensure the sandbox can't affect the insecure env
"coroutine", "coroutine",
"string", "string",
"table", "table",
@ -167,6 +185,17 @@ void ScriptApiSecurity::initializeSecurity()
lua_pop(L, 1); lua_pop(L, 1);
// Copy safe libraries
for (const char *libname : whitelist_tables) {
lua_getfield(L, old_globals, libname);
lua_newtable(L);
shallow_copy_table(L);
lua_setglobal(L, libname);
lua_pop(L, 1);
}
// Copy safe IO functions // Copy safe IO functions
lua_getfield(L, old_globals, "io"); lua_getfield(L, old_globals, "io");
lua_newtable(L); lua_newtable(L);
@ -222,6 +251,19 @@ void ScriptApiSecurity::initializeSecurity()
#endif #endif
lua_pop(L, 1); // Pop globals_backup lua_pop(L, 1); // Pop globals_backup
/*
* In addition to copying the tables in whitelist_tables, we also need to
* replace the string metatable. Otherwise old_globals.string would
* be accessible via getmetatable("").__index from inside the sandbox.
*/
lua_pushliteral(L, "");
lua_newtable(L);
lua_getglobal(L, "string");
lua_setfield(L, -2, "__index");
lua_setmetatable(L, -2);
lua_pop(L, 1); // Pop empty string
} }
void ScriptApiSecurity::initializeSecurityClient() void ScriptApiSecurity::initializeSecurityClient()