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Refactor trusted mod checking code
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sfan5 committed Dec 18, 2021
1 parent f405459 commit b2409b14d0682655363c1b3b3b6bafbaa7e7c1bf
Showing with 46 additions and 72 deletions.
  1. +33 −0 src/script/cpp_api/s_security.cpp
  2. +9 −5 src/script/cpp_api/s_security.h
  3. +3 −36 src/script/lua_api/l_http.cpp
  4. +1 −31 src/script/lua_api/l_util.cpp
@@ -27,6 +27,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,

#include <cerrno>
#include <string>
#include <algorithm>
#include <iostream>


@@ -604,6 +605,38 @@ bool ScriptApiSecurity::checkPath(lua_State *L, const char *path,
return false;
}

bool ScriptApiSecurity::checkWhitelisted(lua_State *L, const std::string &setting)
{
assert(str_starts_with(setting, "secure."));

// We have to make sure that this function is being called directly by
// a mod, otherwise a malicious mod could override this function and
// steal its return value.
lua_Debug info;

// Make sure there's only one item below this function on the stack...
if (lua_getstack(L, 2, &info))
return false;
FATAL_ERROR_IF(!lua_getstack(L, 1, &info), "lua_getstack() failed");
FATAL_ERROR_IF(!lua_getinfo(L, "S", &info), "lua_getinfo() failed");

// ...and that that item is the main file scope.
if (strcmp(info.what, "main") != 0)
return false;

// Mod must be listed in secure.http_mods or secure.trusted_mods
lua_rawgeti(L, LUA_REGISTRYINDEX, CUSTOM_RIDX_CURRENT_MOD_NAME);
if (!lua_isstring(L, -1))
return false;
std::string mod_name = readParam<std::string>(L, -1);

std::string value = g_settings->get(setting);
value.erase(std::remove(value.begin(), value.end(), ' '), value.end());
auto mod_list = str_split(value, ',');

return CONTAINS(mod_list, mod_name);
}


int ScriptApiSecurity::sl_g_dofile(lua_State *L)
{
@@ -40,11 +40,6 @@ with this program; if not, write to the Free Software Foundation, Inc.,
class ScriptApiSecurity : virtual public ScriptApiBase
{
public:
int getThread(lua_State *L);
// creates an empty Lua environment
void createEmptyEnv(lua_State *L);
// sets the enviroment to the table thats on top of the stack
void setLuaEnv(lua_State *L, int thread);
// Sets up security on the ScriptApi's Lua state
void initializeSecurity();
void initializeSecurityClient();
@@ -57,8 +52,17 @@ class ScriptApiSecurity : virtual public ScriptApiBase
// Checks if mods are allowed to read (and optionally write) to the path
static bool checkPath(lua_State *L, const char *path, bool write_required,
bool *write_allowed=NULL);
// Check if mod is whitelisted in the given setting
// This additionally checks that the mod's main file scope is executing.
static bool checkWhitelisted(lua_State *L, const std::string &setting);

private:
int getThread(lua_State *L);
// sets the enviroment to the table thats on top of the stack
void setLuaEnv(lua_State *L, int thread);
// creates an empty Lua environment
void createEmptyEnv(lua_State *L);

// Syntax: "sl_" <Library name or 'g' (global)> '_' <Function name>
// (sl stands for Secure Lua)

@@ -21,14 +21,13 @@ with this program; if not, write to the Free Software Foundation, Inc.,
#include "common/c_converter.h"
#include "common/c_content.h"
#include "lua_api/l_http.h"
#include "cpp_api/s_security.h"
#include "httpfetch.h"
#include "settings.h"
#include "debug.h"
#include "log.h"

#include <algorithm>
#include <iomanip>
#include <cctype>

#define HTTP_API(name) \
lua_pushstring(L, #name); \
@@ -181,40 +180,8 @@ int ModApiHttp::l_request_http_api(lua_State *L)
{
NO_MAP_LOCK_REQUIRED;

// We have to make sure that this function is being called directly by
// a mod, otherwise a malicious mod could override this function and
// steal its return value.
lua_Debug info;

// Make sure there's only one item below this function on the stack...
if (lua_getstack(L, 2, &info)) {
return 0;
}
FATAL_ERROR_IF(!lua_getstack(L, 1, &info), "lua_getstack() failed");
FATAL_ERROR_IF(!lua_getinfo(L, "S", &info), "lua_getinfo() failed");

// ...and that that item is the main file scope.
if (strcmp(info.what, "main") != 0) {
return 0;
}

// Mod must be listed in secure.http_mods or secure.trusted_mods
lua_rawgeti(L, LUA_REGISTRYINDEX, CUSTOM_RIDX_CURRENT_MOD_NAME);
if (!lua_isstring(L, -1)) {
return 0;
}

std::string mod_name = readParam<std::string>(L, -1);
std::string http_mods = g_settings->get("secure.http_mods");
http_mods.erase(std::remove(http_mods.begin(), http_mods.end(), ' '), http_mods.end());
std::vector<std::string> mod_list_http = str_split(http_mods, ',');

std::string trusted_mods = g_settings->get("secure.trusted_mods");
trusted_mods.erase(std::remove(trusted_mods.begin(), trusted_mods.end(), ' '), trusted_mods.end());
std::vector<std::string> mod_list_trusted = str_split(trusted_mods, ',');

mod_list_http.insert(mod_list_http.end(), mod_list_trusted.begin(), mod_list_trusted.end());
if (std::find(mod_list_http.begin(), mod_list_http.end(), mod_name) == mod_list_http.end()) {
if (!ScriptApiSecurity::checkWhitelisted(L, "secure.http_mods") &&
!ScriptApiSecurity::checkWhitelisted(L, "secure.trusted_mods")) {
lua_pushnil(L);
return 1;
}
@@ -41,7 +41,6 @@ with this program; if not, write to the Free Software Foundation, Inc.,
#include "util/hex.h"
#include "util/sha1.h"
#include "util/png.h"
#include <algorithm>
#include <cstdio>

// log([level,] text)
@@ -444,36 +443,7 @@ int ModApiUtil::l_request_insecure_environment(lua_State *L)
return 1;
}

// We have to make sure that this function is being called directly by
// a mod, otherwise a malicious mod could override this function and
// steal its return value.
lua_Debug info;
// Make sure there's only one item below this function on the stack...
if (lua_getstack(L, 2, &info)) {
return 0;
}
FATAL_ERROR_IF(!lua_getstack(L, 1, &info), "lua_getstack() failed");
FATAL_ERROR_IF(!lua_getinfo(L, "S", &info), "lua_getinfo() failed");
// ...and that that item is the main file scope.
if (strcmp(info.what, "main") != 0) {
return 0;
}

// Get mod name
lua_rawgeti(L, LUA_REGISTRYINDEX, CUSTOM_RIDX_CURRENT_MOD_NAME);
if (!lua_isstring(L, -1)) {
return 0;
}

// Check secure.trusted_mods
std::string mod_name = readParam<std::string>(L, -1);
std::string trusted_mods = g_settings->get("secure.trusted_mods");
trusted_mods.erase(std::remove_if(trusted_mods.begin(),
trusted_mods.end(), static_cast<int(*)(int)>(&std::isspace)),
trusted_mods.end());
std::vector<std::string> mod_list = str_split(trusted_mods, ',');
if (std::find(mod_list.begin(), mod_list.end(), mod_name) ==
mod_list.end()) {
if (!ScriptApiSecurity::checkWhitelisted(L, "secure.trusted_mods")) {
return 0;
}

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