Add LuaSecureRandom

src/script/lua_api/l_noise.cpp

@@ -22,6 +22,8 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #include "common/c_converter.h"
 #include "common/c_content.h"
 #include "log.h"
+#include "porting.h"
+#include "util/numeric.h"
 
 ///////////////////////////////////////
 /*
@@ -600,3 +602,116 @@ const luaL_reg LuaPcgRandom::methods[] = {
 	luamethod(LuaPcgRandom, rand_normal_dist),
 	{0,0}
 };
+
+///////////////////////////////////////
+/*
+	LuaSecureRandom
+*/
+
+bool LuaSecureRandom::fillRandBuf()
+{
+	return porting::secure_rand_fill_buf(m_rand_buf, RAND_BUF_SIZE);
+}
+
+int LuaSecureRandom::l_next_bytes(lua_State *L)
+{
+	NO_MAP_LOCK_REQUIRED;
+
+	LuaSecureRandom *o = checkobject(L, 1);
+	u32 count = lua_isnumber(L, 2) ? lua_tointeger(L, 2) : 1;
+
+	// Limit count
+	count = MYMIN(RAND_BUF_SIZE, count);
+
+	// Find out whether we can pass directly from our array, or have to do some gluing
+	size_t count_remaining = RAND_BUF_SIZE - o->m_rand_idx;
+	if (count_remaining >= count) {
+		lua_pushlstring(L, o->m_rand_buf + o->m_rand_idx, count);
+		o->m_rand_idx += count;
+	} else {
+		char output_buf[RAND_BUF_SIZE];
+
+		// Copy over with what we have left from our current buffer
+		memcpy(output_buf, o->m_rand_buf + o->m_rand_idx, count_remaining);
+
+		// Refill buffer and copy over the remainder of what was requested
+		o->fillRandBuf();
+		memcpy(output_buf + count_remaining, o->m_rand_buf, count - count_remaining);
+
+		// Update index
+		o->m_rand_idx = count - count_remaining;
+
+		lua_pushlstring(L, output_buf, count);
+	}
+
+	return 1;
+}
+
+
+int LuaSecureRandom::create_object(lua_State *L)
+{
+	LuaSecureRandom *o = new LuaSecureRandom();
+
+	// Fail and return nil if we can't securely fill the buffer
+	if (!o->fillRandBuf()) {
+		delete o;
+		return 0;
+	}
+
+	*(void **)(lua_newuserdata(L, sizeof(void *))) = o;
+	luaL_getmetatable(L, className);
+	lua_setmetatable(L, -2);
+	return 1;
+}
+
+
+int LuaSecureRandom::gc_object(lua_State *L)
+{
+	LuaSecureRandom *o = *(LuaSecureRandom **)(lua_touserdata(L, 1));
+	delete o;
+	return 0;
+}
+
+
+LuaSecureRandom *LuaSecureRandom::checkobject(lua_State *L, int narg)
+{
+	luaL_checktype(L, narg, LUA_TUSERDATA);
+	void *ud = luaL_checkudata(L, narg, className);
+	if (!ud)
+		luaL_typerror(L, narg, className);
+	return *(LuaSecureRandom **)ud;
+}
+
+
+void LuaSecureRandom::Register(lua_State *L)
+{
+	lua_newtable(L);
+	int methodtable = lua_gettop(L);
+	luaL_newmetatable(L, className);
+	int metatable = lua_gettop(L);
+
+	lua_pushliteral(L, "__metatable");
+	lua_pushvalue(L, methodtable);
+	lua_settable(L, metatable);
+
+	lua_pushliteral(L, "__index");
+	lua_pushvalue(L, methodtable);
+	lua_settable(L, metatable);
+
+	lua_pushliteral(L, "__gc");
+	lua_pushcfunction(L, gc_object);
+	lua_settable(L, metatable);
+
+	lua_pop(L, 1);
+
+	luaL_openlib(L, 0, methods, 0);
+	lua_pop(L, 1);
+
+	lua_register(L, className, create_object);
+}
+
+const char LuaSecureRandom::className[] = "SecureRandom";
+const luaL_reg LuaSecureRandom::methods[] = {
+	luamethod(LuaSecureRandom, next_bytes),
+	{0,0}
+};

src/script/lua_api/l_noise.h

@@ -160,4 +160,37 @@ public:
 	static void Register(lua_State *L);
 };
 
+
+/*
+	LuaSecureRandom
+*/
+class LuaSecureRandom : public ModApiBase {
+private:
+	static const size_t RAND_BUF_SIZE = 2048;
+	static const char className[];
+	static const luaL_reg methods[];
+
+	u32 m_rand_idx;
+	char m_rand_buf[RAND_BUF_SIZE];
+
+	// Exported functions
+
+	// garbage collector
+	static int gc_object(lua_State *L);
+
+	// next_bytes(self, count) -> get count many bytes
+	static int l_next_bytes(lua_State *L);
+
+public:
+	bool fillRandBuf();
+
+	// LuaSecureRandom()
+	// Creates an LuaSecureRandom and leaves it on top of stack
+	static int create_object(lua_State *L);
+
+	static LuaSecureRandom *checkobject(lua_State *L, int narg);
+
+	static void Register(lua_State *L);
+};
+
 #endif /* L_NOISE_H_ */