#include <stdlib.h>

#include <stdio.h>

#include <errno.h>

#include <lua.h>

#include <lauxlib.h>

#include <mbedtls/gcm.h>

static int gcm_crypt(lua_State *L, unsigned int mode) {

size_t dataLen, keyLen, ivLen;

const unsigned char *const data = (const unsigned char *)luaL_checklstring(L, 1, &dataLen);

const unsigned char *const key = (const unsigned char *)luaL_checklstring(L, 2, &keyLen);

const unsigned char *const iv = (const unsigned char *)luaL_checklstring(L, 3, &ivLen);

mbedtls_gcm_context ctx;

mbedtls_gcm_init(&ctx);

const int err1 = mbedtls_gcm_setkey(&ctx, MBEDTLS_CIPHER_ID_AES, key, keyLen * 8);

if (err1) {

mbedtls_gcm_free(&ctx);

return luaL_error(L, "mbedtls_gcm_setkey failed: err:%d errno:%d", err1, errno);

}

unsigned char *const output = (unsigned char *)malloc(dataLen);

if (!output) {

mbedtls_gcm_free(&ctx);

return luaL_error(L, "malloc failed: %d", errno);

}

const size_t tagLen = 16;

unsigned char tag[tagLen];

const int err2 = mbedtls_gcm_crypt_and_tag(

&ctx,

mode,

dataLen,

iv, ivLen,

NULL, 0,

data, output,

tagLen, tag);

mbedtls_gcm_free(&ctx);

if (err2) {

free(output);

return luaL_error(L, "mbedtls_gcm_crypt_and_tag failed: err:%d errno:%d", err2, errno);

}

lua_pushlstring(L, (const unsigned char *)output, dataLen);

lua_pushlstring(L, (const unsigned char *)tag, tagLen);

free(output);

return 2;

}

static int gcm_encrypt(lua_State *L) {

return gcm_crypt(L, MBEDTLS_GCM_ENCRYPT);

}

static int gcm_decrypt(lua_State *L) {

return gcm_crypt(L, MBEDTLS_GCM_DECRYPT);

}

/*

encrypt(data, key, iv) -> (data, tag)

decrypt(data, key, iv) -> (data, tag)

*/

LUA_API int luaopen_gcm(lua_State *L) {

lua_newtable(L);

lua_pushcfunction(L, gcm_encrypt);

lua_setfield(L, -2, "encrypt");

lua_pushcfunction(L, gcm_decrypt);

lua_setfield(L, -2, "decrypt");

return 1;

}