1 files changed, 32 insertions, 0 deletions
diff --git a/downlevelshim/shim.c b/downlevelshim/shim.c
new file mode 100644
index 0000000..d277639
--- /dev/null
+++ b/downlevelshim/shim.c
@@ -0,0 +1,32 @@
+/* SPDX-License-Identifier: GPL-2.0
+ *
+ * Copyright (C) 2018-2021 WireGuard LLC. All Rights Reserved.
+ */
+
+#include <windows.h>
+#include <wintrust.h>
+
+typedef DWORD(DRIVER_FINAL_POLICY_FN)(CRYPT_PROVIDER_DATA *);
+typedef DRIVER_FINAL_POLICY_FN *PDRIVER_FINAL_POLICY_FN;
+
+DRIVER_FINAL_POLICY_FN DriverFinalPolicy;
+
+DWORD
+DriverFinalPolicy(CRYPT_PROVIDER_DATA *ProvData)
+{
+    DWORD OriginalLastError = GetLastError();
+    HMODULE WintrustModule = GetModuleHandleA("WINTRUST.DLL");
+    if (!WintrustModule)
+        return ERROR_INVALID_LIBRARY;
+    PDRIVER_FINAL_POLICY_FN RealDriverFinalPolicy =
+        (PDRIVER_FINAL_POLICY_FN)GetProcAddress(WintrustModule, "DriverFinalPolicy");
+    if (!RealDriverFinalPolicy)
+        return ERROR_INVALID_FUNCTION;
+    DWORD Ret = RealDriverFinalPolicy(ProvData);
+    if (Ret == ERROR_APP_WRONG_OS)
+    {
+        Ret = ERROR_SUCCESS;
+        SetLastError(OriginalLastError);
+    }
+    return Ret;
+}