From fadf7d944d9b956155e32c53dd106127c85b9644 Mon Sep 17 00:00:00 2001
From: "Radames S. Cruz Moreno" <racruzmo@microsoft.com>
Date: Fri, 24 Jul 2020 18:06:50 -0700
Subject: [PATCH 1/2] Use RtlGenRandom if BCryptGenRandom fails

In some circumstances BCryptGenRandom can fail (for example, when
running within a Google Chrome sandboxed process). If this ever happens,
use RtlGenRandom instead to generate a cryptographically secure random
number.
---
 random/random.c | 35 +++++++++++++++++++++++++++++++++--
 1 file changed, 33 insertions(+), 2 deletions(-)

diff --git a/random/random.c b/random/random.c
index fc547fe..ea41dd2 100644
--- a/random/random.c
+++ b/random/random.c
@@ -18,6 +18,14 @@
     static int lock = -1;
 #endif
 
+#if defined(__WINDOWS__)
+
+#define RTL_GENRANDOM "SystemFunction036"
+
+NTSTATUS last_bcrypt_error = 0;
+
+#endif
+
 
 static __inline void delay(unsigned int count)
 {
@@ -29,8 +37,31 @@ int random_bytes(unsigned char* random_array, unsigned int nbytes)
 { // Generation of "nbytes" of random values
 
 #if defined(__WINDOWS__)	
-	if (!BCRYPT_SUCCESS(BCryptGenRandom(NULL, random_array, nbytes, BCRYPT_USE_SYSTEM_PREFERRED_RNG))) {
-		return false;
+    if (BCRYPT_SUCCESS(last_bcrypt_error))
+    {
+        NTSTATUS status = BCryptGenRandom(
+            NULL, random_array, nbytes, BCRYPT_USE_SYSTEM_PREFERRED_RNG);
+
+        if (BCRYPT_SUCCESS(status))
+        {
+            return true;
+        }
+
+        last_bcrypt_error = status;
+    }
+
+    HMODULE hAdvApi = LoadLibraryA("ADVAPI32.DLL");
+    if (hAdvApi)
+    {
+        BOOLEAN(APIENTRY * RtlGenRandom)
+            (void*, ULONG) = (BOOLEAN(APIENTRY*)(void*, ULONG))GetProcAddress(hAdvApi, RTL_GENRANDOM);
+
+        if (!RtlGenRandom || !RtlGenRandom(random_array, nbytes))
+        {
+            return false;
+        }
+
+        FreeLibrary(hAdvApi);
     }
 
 #elif defined(__LINUX__)

From ae63d036ea9290cd8073243e55f00f5f9b4931da Mon Sep 17 00:00:00 2001
From: "Radames S. Cruz Moreno" <racruzmo@microsoft.com>
Date: Thu, 30 Jul 2020 13:14:58 -0700
Subject: [PATCH 2/2] Return false if unable to load advapi32.dll. Correctly
 free advapi32.dll when failing to do GetProcAddress.

---
 random/random.c | 78 +++++++++++++++++++++++++++----------------------
 1 file changed, 43 insertions(+), 35 deletions(-)

diff --git a/random/random.c b/random/random.c
index ea41dd2..593d14e 100644
--- a/random/random.c
+++ b/random/random.c
@@ -10,12 +10,12 @@
 #include <stdlib.h>
 #include <stdbool.h>
 #if defined(__WINDOWS__)
-    #include <windows.h>
-    #include <bcrypt.h>
+	#include <windows.h>
+	#include <bcrypt.h>
 #elif defined(__LINUX__)
-    #include <unistd.h>
-    #include <fcntl.h>
-    static int lock = -1;
+	#include <unistd.h>
+	#include <fcntl.h>
+	static int lock = -1;
 #endif
 
 #if defined(__WINDOWS__)
@@ -37,44 +37,52 @@ int random_bytes(unsigned char* random_array, unsigned int nbytes)
 { // Generation of "nbytes" of random values
 
 #if defined(__WINDOWS__)	
-    if (BCRYPT_SUCCESS(last_bcrypt_error))
-    {
-        NTSTATUS status = BCryptGenRandom(
-            NULL, random_array, nbytes, BCRYPT_USE_SYSTEM_PREFERRED_RNG);
+	if (BCRYPT_SUCCESS(last_bcrypt_error))
+	{
+		NTSTATUS status = BCryptGenRandom(
+			NULL, random_array, nbytes, BCRYPT_USE_SYSTEM_PREFERRED_RNG);
 
-        if (BCRYPT_SUCCESS(status))
-        {
-            return true;
-        }
+		if (BCRYPT_SUCCESS(status))
+		{
+			return true;
+		}
 
-        last_bcrypt_error = status;
-    }
+		last_bcrypt_error = status;
+	}
 
-    HMODULE hAdvApi = LoadLibraryA("ADVAPI32.DLL");
-    if (hAdvApi)
-    {
-        BOOLEAN(APIENTRY * RtlGenRandom)
-            (void*, ULONG) = (BOOLEAN(APIENTRY*)(void*, ULONG))GetProcAddress(hAdvApi, RTL_GENRANDOM);
+	HMODULE hAdvApi = LoadLibraryA("ADVAPI32.DLL");
+	if (!hAdvApi)
+	{
+		return false;
+	}
 
-        if (!RtlGenRandom || !RtlGenRandom(random_array, nbytes))
-        {
-            return false;
-        }
+	BOOLEAN(APIENTRY * RtlGenRandom)
+		(void*, ULONG) = (BOOLEAN(APIENTRY*)(void*, ULONG))GetProcAddress(hAdvApi, RTL_GENRANDOM);
 
-        FreeLibrary(hAdvApi);
-    }
+	BOOLEAN genrand_result = FALSE;
+	if (RtlGenRandom)
+	{
+		genrand_result = RtlGenRandom(random_array, nbytes);
+	}
+
+	FreeLibrary(hAdvApi);
+
+	if (!genrand_result)
+	{
+		return false;
+	}
 
 #elif defined(__LINUX__)
 	int r, n = nbytes, count = 0;
-    
-    if (lock == -1) {
-	    do {
-		    lock = open("/dev/urandom", O_RDONLY);
-		    if (lock == -1) {
-			    delay(0xFFFFF);
-		    }
-	    } while (lock == -1);
-    }
+	
+	if (lock == -1) {
+		do {
+			lock = open("/dev/urandom", O_RDONLY);
+			if (lock == -1) {
+				delay(0xFFFFF);
+			}
+		} while (lock == -1);
+	}
 
 	while (n > 0) {
 		do {