From 24574712d19f1a5117936beeaa1ed9773199d4f3 Mon Sep 17 00:00:00 2001
From: LoRd_MuldeR <mulder2@gmx.de>
Date: Wed, 21 Oct 2020 19:29:37 +0200
Subject: [PATCH] Use RtlGenRandom() directly on the Windows platform.

---
 frontend/src/main.c          |  2 +-
 libslunkcrypt/src/internal.c | 67 ++++++++++++++++++++++--------------
 2 files changed, 43 insertions(+), 26 deletions(-)

diff --git a/frontend/src/main.c b/frontend/src/main.c
index 764ebee..e61c46d 100644
--- a/frontend/src/main.c
+++ b/frontend/src/main.c
@@ -512,7 +512,7 @@ static int run_test_case(const char *const message)
 		goto clean_up;
 	}
 
-	if (strncmp(message, text_temp, length) != 0)
+	if (memcmp(message, text_temp, length * sizeof(char)) != 0)
 	{
 		FPUTS(T("\n\nWhoops: Decrypted message does *not* match the original message!\n\n"), stderr);
 		goto clean_up;
diff --git a/libslunkcrypt/src/internal.c b/libslunkcrypt/src/internal.c
index c141395..acc949c 100644
--- a/libslunkcrypt/src/internal.c
+++ b/libslunkcrypt/src/internal.c
@@ -3,58 +3,75 @@
 /* This work has been released under the CC0 1.0 Universal license!           */
 /******************************************************************************/
 
-#ifdef _WIN32
-#define _WIN32_WINNT 0x0600
-#define _CRT_RAND_S 1
-#define WIN32_LEAN_AND_MEAN 1
-#endif
-
 #include <slunkcrypt.h>
 
 #ifdef _WIN32
+#define WIN32_LEAN_AND_MEAN 1
 #include <Windows.h>
+typedef BOOLEAN(WINAPI *genrandom_t)(void*, ULONG);
+static volatile LONG g_random_init = 0L;
+static HMODULE g_advapi32 = NULL;
+static genrandom_t g_genrandom = NULL;
 #else
 #include <unistd.h>
 #include <fcntl.h>
 #include <string.h>
-#if (defined(__GLIBC__) && defined(__GLIBC_MINOR__) && (__GLIBC__ >= 2) && (__GLIBC_MINOR__ >= 25)) || (defined(__FreeBSD__) && (__FreeBSD__ >= 12))
+#if (defined(__GLIBC__) && __GLIBC_PREREQ(2,25)) || (defined(__FreeBSD__) && (__FreeBSD__ >= 12))
 #include <sys/random.h>
+#else
+static const char *const DEV_RANDOM[] = { "/dev/urandom", "/dev/arandom", "/dev/random", NULL };
 #endif
 #endif
 
+#ifdef _WIN32
+static genrandom_t init_genrandom()
+{
+	LONG state;
+	while ((state = InterlockedCompareExchange(&g_random_init, -1L, 0L)) != 0L)
+	{
+		if (state > 0L)
+		{
+			return g_genrandom;
+		}
+		Sleep(0U);
+	}
+	if (g_advapi32 || (g_advapi32 = LoadLibrary(L"advapi32.dll")))
+	{
+		if ((g_genrandom = (genrandom_t)GetProcAddress(g_advapi32, "SystemFunction036")))
+		{
+			InterlockedExchange(&g_random_init, 1L);
+			return g_genrandom;
+		}
+	}
+	InterlockedExchange(&g_random_init, 0L);
+	return NULL;
+}
+#endif
+
 int slunkcrypt_random_bytes(uint8_t* const buffer, const size_t length)
 {
 #ifdef _WIN32
-	size_t pos = 0U;
-	while (pos < length)
+	if ((length <= ((size_t)ULONG_MAX)))
 	{
-		const size_t bytes_left = length - pos;
-		const size_t bytes_copy = (bytes_left < sizeof(uint32_t)) ? bytes_left : sizeof(uint32_t);
-		uint32_t temp;
-		if (rand_s(&temp) != 0)
+		const genrandom_t genrandom = init_genrandom();
+		if (genrandom)
 		{
-			return -1;
-		}
-		for (size_t i = 0; i < bytes_copy; ++i)
-		{
-			buffer[pos++] = (uint8_t)(temp & 0xFF);
-			temp >>= 8;
+			return genrandom(buffer, (ULONG)length) ? 0 : (-1);
 		}
 	}
-	return 0;
+	return -1;
 #else
-#if (defined(__GLIBC__) && defined(__GLIBC_MINOR__) && (__GLIBC__ >= 2) && (__GLIBC_MINOR__ >= 25)) || (defined(__FreeBSD__) && (__FreeBSD__ >= 12))
+#if (defined(__GLIBC__) && __GLIBC_PREREQ(2,25)) || (defined(__FreeBSD__) && (__FreeBSD__ >= 12))
 	if (getrandom(buffer, length, 0U) >= length)
 	{
 		return 0;
 	}
 	return -1;
 #else
-	static const char* const PATH[] = { "/dev/urandom", "/dev/arandom", "/dev/random" };
 	int result = -1;
-	for (size_t i = 0; (i < 3U) && (result < 0); ++i)
+	for (size_t i = 0U; DEV_RANDOM[i] && (result != 0); ++i)
 	{
-		const int fd = open(PATH[i], O_RDONLY);
+		const int fd = open(DEV_RANDOM[i], O_RDONLY);
 		if (fd >= 0)
 		{
 			if (read(fd, buffer, length) >= length)
@@ -76,7 +93,7 @@ void slunkcrypt_bzero(void* const ptr, const size_t length)
 #if defined(_WIN32) && defined(SecureZeroMemory)
 		SecureZeroMemory(ptr, length);
 #else
-#if (defined(__GLIBC__) && defined(__GLIBC_MINOR__) && (__GLIBC__ >= 2) && (__GLIBC_MINOR__ >= 25)) || (defined(__FreeBSD__) && (__FreeBSD__ >= 11))
+#if (defined(__GLIBC__) && __GLIBC_PREREQ(2,25)) || (defined(__FreeBSD__) && (__FreeBSD__ >= 11))
 		explicit_bzero(ptr, length);
 #else
 		volatile uint8_t *buffer = (volatile uint8_t*)ptr;