virtualx-engine/thirdparty/mbedtls/patches/windows-entropy-bcrypt.diff

Backported from: https://github.com/Mbed-TLS/mbedtls/pull/8047

diff --git a/thirdparty/mbedtls/library/entropy_poll.c b/thirdparty/mbedtls/library/entropy_poll.c
index cde49e66a0..4c5184686e 100644
--- a/thirdparty/mbedtls/library/entropy_poll.c
+++ b/thirdparty/mbedtls/library/entropy_poll.c
@@ -39,32 +39,34 @@
 
 #if defined(_WIN32) && !defined(EFIX64) && !defined(EFI32)
 
-#if !defined(_WIN32_WINNT)
-#define _WIN32_WINNT 0x0400
-#endif
 #include <windows.h>
-#include <wincrypt.h>
+#include <bcrypt.h>
+#include <intsafe.h>
 
 int mbedtls_platform_entropy_poll(void *data, unsigned char *output, size_t len,
                                   size_t *olen)
 {
-    HCRYPTPROV provider;
     ((void) data);
     *olen = 0;
 
-    if (CryptAcquireContext(&provider, NULL, NULL,
-                            PROV_RSA_FULL, CRYPT_VERIFYCONTEXT) == FALSE) {
-        return MBEDTLS_ERR_ENTROPY_SOURCE_FAILED;
-    }
+    /*
+     * BCryptGenRandom takes ULONG for size, which is smaller than size_t on
+     * 64-bit Windows platforms. Extract entropy in chunks of len (dependent
+     * on ULONG_MAX) size.
+     */
+    while (len != 0) {
+        unsigned long ulong_bytes =
+            (len > ULONG_MAX) ? ULONG_MAX : (unsigned long) len;
+
+        if (!BCRYPT_SUCCESS(BCryptGenRandom(NULL, output, ulong_bytes,
+                                            BCRYPT_USE_SYSTEM_PREFERRED_RNG))) {
+            return MBEDTLS_ERR_ENTROPY_SOURCE_FAILED;
+        }
 
-    if (CryptGenRandom(provider, (DWORD) len, output) == FALSE) {
-        CryptReleaseContext(provider, 0);
-        return MBEDTLS_ERR_ENTROPY_SOURCE_FAILED;
+        *olen += ulong_bytes;
+        len -= ulong_bytes;
     }
 
-    CryptReleaseContext(provider, 0);
-    *olen = len;
-
     return 0;
 }
 #else /* _WIN32 && !EFIX64 && !EFI32 */