SlunkCrypt/libslunkcrypt/src/internal.c

/******************************************************************************/
/* SlunkCrypt, by LoRd_MuldeR <MuldeR2@GMX.de>                                */
/* This work has been released under the CC0 1.0 Universal license!           */
/******************************************************************************/

#include <slunkcrypt.h>

#ifdef _WIN32
#	define WIN32_LEAN_AND_MEAN 1
#	include <Windows.h>
#	if defined(SecureZeroMemory)
#		define HAVE_SECURE_ZERO_MEMORY 1
#	else
#		define HAVE_SECURE_ZERO_MEMORY 0
#	endif
#	define HAVE_GETRANDOM 0
#	define HAVE_EXPLICIT_BZERO 0
#else
#	include <unistd.h>
#	include <fcntl.h>
#	include <string.h>
#	if defined(__GLIBC__) && (__GLIBC__ >= 2) && (__GLIBC_MINOR__ >= 25)
#		define HAVE_GETRANDOM 1
#		define HAVE_EXPLICIT_BZERO 1
#	elif defined(__FreeBSD__) && (__FreeBSD__ >= 12)
#		define HAVE_GETRANDOM 1
#		define HAVE_EXPLICIT_BZERO 1
#	elif defined(__FreeBSD__) && (__FreeBSD__ >= 11)
#		define HAVE_GETRANDOM 0
#		define HAVE_EXPLICIT_BZERO 1
#	else
#		define HAVE_GETRANDOM 0
#		define HAVE_EXPLICIT_BZERO 0
#	endif
#	if HAVE_GETRANDOM
#		include <sys/random.h>
#	else
#		include <pthread.h>
#	endif
#endif

// ==========================================================================
// Initialization
// ==========================================================================

#if defined(_WIN32)
typedef BOOLEAN(WINAPI *genrandom_t)(void*, ULONG);
static genrandom_t win32_init_random(void)
{
	static volatile LONG s_random_init = 0L;
	static HMODULE s_advapi32 = NULL;
	static genrandom_t s_genrandom = NULL;
	LONG state;
	while ((state = InterlockedCompareExchange(&s_random_init, -1L, 0L)) != 0L)
	{
		if (state > 0L)
		{
			return s_genrandom;
		}
		Sleep(0U);
	}
	if (s_advapi32 || (s_advapi32 = LoadLibraryW(L"advapi32.dll")))
	{
		if ((s_genrandom = (genrandom_t)GetProcAddress(s_advapi32, "SystemFunction036")))
		{
			InterlockedExchange(&s_random_init, 1L);
			return s_genrandom;
		}
	}
	InterlockedExchange(&s_random_init, 0L);
	return NULL;
}
#elif !HAVE_GETRANDOM
static int unix_init_random(void)
{
	static pthread_mutex_t s_mutex = PTHREAD_MUTEX_INITIALIZER;
	static int s_random_fd = -1;
	static const char *const DEV_RANDOM[] = { "/dev/urandom", "/dev/arandom", "/dev/random", NULL };
	if (pthread_mutex_lock(&s_mutex) != 0)
	{
		return -1;
	}
	if (s_random_fd < 0)
	{
		for (size_t i = 0U; DEV_RANDOM[i]; ++i)
		{
			if ((s_random_fd = open(DEV_RANDOM[i], O_RDONLY)) >= 0)
			{
				break;
			}
		}
	}
	pthread_mutex_unlock(&s_mutex);
	return s_random_fd;
}
#endif

// ==========================================================================
// Public functions
// ==========================================================================

int slunkcrypt_random_bytes(uint8_t* const buffer, const size_t length)
{
#if defined(_WIN32)
	if ((length <= ((size_t)ULONG_MAX)))
	{
		const genrandom_t genrandom = win32_init_random();
		if (genrandom)
		{
			return genrandom(buffer, (ULONG)length) ? 0 : (-1);
		}
	}
	return -1;
#elif HAVE_GETRANDOM
	if (getrandom(buffer, length, 0U) >= length)
	{
		return 0;
	}
	return -1;
#else
	const int fd = unix_init_random();
	if (fd >= 0)
	{
		if (read(fd, buffer, length) >= length)
		{
			return 0;
		}
	}
	return -1;
#endif
}

void slunkcrypt_bzero(void* const ptr, const size_t length)
{
	if ((ptr) && (length > 0U))
	{
#if HAVE_SECURE_ZERO_MEMORY
		SecureZeroMemory(ptr, length);
#elif HAVE_EXPLICIT_BZERO
		explicit_bzero(ptr, length);
#else
		volatile uint8_t *buffer = (volatile uint8_t*)ptr;
		for (size_t i = 0U; i < length; ++i)
		{
			buffer[i] = 0U;
		}
#endif
	}
}