From 470bdf3e26e433032fe7986f379cad797cdd94cd Mon Sep 17 00:00:00 2001
From: "Jason A. Donenfeld" <Jason@zx2c4.com>
Date: Thu, 14 Oct 2021 06:37:50 +0000
Subject: [PATCH] api: use proper instance id bounds

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
---
 api/adapter.c            | 2 +-
 api/adapter.h            | 4 ++--
 api/rundll32.c           | 6 +++---
 api/rundll32.h           | 2 +-
 setupapihost/host_win7.h | 4 ++--
 5 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/api/adapter.c b/api/adapter.c
index ab79f0c..0dd8c42 100644
--- a/api/adapter.c
+++ b/api/adapter.c
@@ -523,7 +523,7 @@ DeviceCreateCallback(
     SW_DEVICE_CREATE_CTX *Ctx = Context;
     Ctx->CreateResult = CreateResult;
     if (DeviceInstanceId)
-        wcsncpy_s(Ctx->DeviceInstanceId, MAX_INSTANCE_ID, DeviceInstanceId, _TRUNCATE);
+        wcsncpy_s(Ctx->DeviceInstanceId, MAX_DEVICE_ID_LEN, DeviceInstanceId, _TRUNCATE);
     SetEvent(Ctx->Triggered);
 }
 
diff --git a/api/adapter.h b/api/adapter.h
index 567ee82..cfa22fd 100644
--- a/api/adapter.h
+++ b/api/adapter.h
@@ -8,9 +8,9 @@
 #include "wintun.h"
 #include <IPExport.h>
 #include <SetupAPI.h>
+#include <cfgmgr32.h>
 #include <Windows.h>
 
-#define MAX_INSTANCE_ID MAX_PATH /* TODO: Is MAX_PATH always enough? */
 #define WINTUN_HWID L"Wintun"
 #define WINTUN_ENUMERATOR (IsWindows7 ? L"ROOT\\" WINTUN_HWID : L"SWD\\" WINTUN_HWID)
 
@@ -28,7 +28,7 @@ typedef struct _WINTUN_ADAPTER
     SP_DEVINFO_DATA DevInfoData;
     WCHAR *InterfaceFilename;
     GUID CfgInstanceID;
-    WCHAR DevInstanceID[MAX_INSTANCE_ID];
+    WCHAR DevInstanceID[MAX_DEVICE_ID_LEN];
     DWORD LuidIndex;
     DWORD IfType;
     DWORD IfIndex;
diff --git a/api/rundll32.c b/api/rundll32.c
index 6bdc7c9..5ea2b15 100644
--- a/api/rundll32.c
+++ b/api/rundll32.c
@@ -311,7 +311,7 @@ InvokeClassInstaller(_In_ LPCWSTR Action, _In_ LPCWSTR Function, _In_ HDEVINFO D
 {
     LOG(WINTUN_LOG_INFO, L"Spawning native process to %s instance", Action);
 
-    WCHAR InstanceId[MAX_INSTANCE_ID];
+    WCHAR InstanceId[MAX_DEVICE_ID_LEN];
     DWORD RequiredChars = _countof(InstanceId);
     if (!SetupDiGetDeviceInstanceIdW(DevInfo, DevInfoData, InstanceId, RequiredChars, &RequiredChars))
     {
@@ -374,7 +374,7 @@ CreateInstanceWin7ViaRundll32(LPWSTR InstanceId)
     LOG(WINTUN_LOG_INFO, L"Spawning native process to create instance");
 
     DWORD LastError;
-    WCHAR Response[MAX_INSTANCE_ID + 1];
+    WCHAR Response[MAX_DEVICE_ID_LEN + 1];
     if (!ExecuteRunDll32(L"CreateInstanceWin7", L"", Response, _countof(Response)))
     {
         LastError = LOG_LAST_ERROR(L"Error executing worker process");
@@ -389,7 +389,7 @@ CreateInstanceWin7ViaRundll32(LPWSTR InstanceId)
     }
     LastError = wcstoul(Argv[0], NULL, 16);
     if (LastError == ERROR_SUCCESS)
-        wcsncpy_s(InstanceId, MAX_INSTANCE_ID, Argv[1], _TRUNCATE);
+        wcsncpy_s(InstanceId, MAX_DEVICE_ID_LEN, Argv[1], _TRUNCATE);
 cleanupArgv:
     LocalFree(Argv);
 cleanup:
diff --git a/api/rundll32.h b/api/rundll32.h
index 030419c..762bfcf 100644
--- a/api/rundll32.h
+++ b/api/rundll32.h
@@ -23,4 +23,4 @@ DisableInstanceViaRundll32(_In_ HDEVINFO DevInfo, _In_ SP_DEVINFO_DATA *DevInfoD
 
 _Return_type_success_(return != FALSE)
 BOOL
-CreateInstanceWin7ViaRundll32(_Out_writes_z_(MAX_INSTANCE_ID) LPWSTR InstanceId);
\ No newline at end of file
+CreateInstanceWin7ViaRundll32(_Out_writes_z_(MAX_DEVICE_ID_LEN) LPWSTR InstanceId);
\ No newline at end of file
diff --git a/setupapihost/host_win7.h b/setupapihost/host_win7.h
index 4e65bff..2640c26 100644
--- a/setupapihost/host_win7.h
+++ b/setupapihost/host_win7.h
@@ -4,8 +4,8 @@
  */
 
 #include <devguid.h>
+#include <cfgmgr32.h>
 
-#define MAX_INSTANCE_ID MAX_PATH /* TODO: Is MAX_PATH always enough? */
 #define WINTUN_HWID L"Wintun"
 
 VOID __stdcall CreateInstanceWin7(HWND hwnd, HINSTANCE hinst, LPSTR lpszCmdLine, int nCmdShow)
@@ -13,7 +13,7 @@ VOID __stdcall CreateInstanceWin7(HWND hwnd, HINSTANCE hinst, LPSTR lpszCmdLine,
 #pragma EXPORT
 
     DWORD LastError = ERROR_SUCCESS;
-    WCHAR InstanceId[MAX_INSTANCE_ID] = { 0 };
+    WCHAR InstanceId[MAX_DEVICE_ID_LEN] = { 0 };
 
     HDEVINFO DevInfo = SetupDiCreateDeviceInfoListExW(&GUID_DEVCLASS_NET, NULL, NULL, NULL);
     if (DevInfo == INVALID_HANDLE_VALUE)