From 1efbd14c2c65c75d147512e2953966a5de7b81bb Mon Sep 17 00:00:00 2001
From: "Jason A. Donenfeld" <Jason@zx2c4.com>
Date: Mon, 10 May 2021 11:02:31 +0200
Subject: [PATCH] api: check that GUID is valid before assuming it's in use

ROOT/NET/000X could have been claimed by a different driver, so we want
to double check.

Link: https://lists.zx2c4.com/pipermail/wireguard/2021-May/006716.html
Reported-by: Piotr Sobczak <piotrs@glosol.com>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
---
 api/adapter.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/api/adapter.c b/api/adapter.c
index ba4467c..ec14d99 100644
--- a/api/adapter.c
+++ b/api/adapter.c
@@ -1452,8 +1452,13 @@ static _Return_type_success_(return != NULL) WINTUN_ADAPTER *CreateAdapter(
         if (RegOpenKeyExW(HKEY_LOCAL_MACHINE, RegPath, 0, KEY_QUERY_VALUE, &Key) == ERROR_SUCCESS)
         {
             RegCloseKey(Key);
-            SetLastError(LOG_ERROR(ERROR_ALREADY_EXISTS, L"Requested GUID is already in use: %s", RequestedGUIDStr));
-            return NULL;
+            NET_LUID Luid;
+            if (ConvertInterfaceGuidToLuid(RequestedGUID, &Luid) == NO_ERROR)
+            {
+                SetLastError(
+                    LOG_ERROR(ERROR_ALREADY_EXISTS, L"Requested GUID is already in use: %s", RequestedGUIDStr));
+                return NULL;
+            }
         }
         LOG(WINTUN_LOG_WARN, L"Requested GUID %s has leftover residue", RequestedGUIDStr);
         HANDLE OriginalToken;