api: port tun\wintun\namespace_windows.go from wireguard-go

Signed-off-by: Simon Rozman <simon@rozman.si>

api/api.c

@@ -16,9 +16,11 @@ DllMain(_In_ HINSTANCE hinstDLL, _In_ DWORD fdwReason, _In_ LPVOID lpvReserved)
     {
     case DLL_PROCESS_ATTACH:
         ResourceModule = hinstDLL;
-    case DLL_THREAD_ATTACH:
-    case DLL_THREAD_DETACH:
+        NamespaceInit();
+        break;
+
     case DLL_PROCESS_DETACH:
+        NamespaceCleanup();
         break;
     }
     return TRUE;

api/api.h

@@ -8,3 +8,16 @@
 #include <Windows.h>
 
 extern HINSTANCE ResourceModule;
+
+_Check_return_
+HANDLE
+TakeNameMutex(_In_z_ LPCWSTR Pool);
+
+void
+ReleaseNameMutex(_In_ HANDLE Mutex);
+
+void
+NamespaceInit();
+
+void
+NamespaceCleanup();

api/api.vcxproj

@@ -120,6 +120,7 @@
       <AdditionalIncludeDirectories>..\$(WintunPlatform)\$(Configuration);%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
     </ResourceCompile>
     <Link>
+      <AdditionalDependencies>Bcrypt.lib;%(AdditionalDependencies)</AdditionalDependencies>
       <ModuleDefinitionFile>exports.def</ModuleDefinitionFile>
       <SubSystem>Windows</SubSystem>
     </Link>
@@ -158,6 +159,7 @@
   </ItemGroup>
   <ItemGroup>
     <ClCompile Include="api.c" />
+    <ClCompile Include="namespace.c" />
   </ItemGroup>
   <Import Project="$(VCTargetsPath)\Microsoft.Cpp.targets" />
   <ImportGroup Label="ExtensionTargets">

api/api.vcxproj.filters

@@ -33,5 +33,8 @@
     <ClCompile Include="api.c">
       <Filter>Source Files</Filter>
     </ClCompile>
+    <ClCompile Include="namespace.c">
+      <Filter>Source Files</Filter>
+    </ClCompile>
   </ItemGroup>
 </Project>

api/namespace.c

@@ -0,0 +1,200 @@
+/* SPDX-License-Identifier: GPL-2.0
+ *
+ * Copyright (C) 2018-2020 WireGuard LLC. All Rights Reserved.
+ */
+
+#include "api.h"
+#include <bcrypt.h>
+#include <sddl.h>
+
+static SECURITY_ATTRIBUTES SecurityAttributes = { .nLength = sizeof(SECURITY_ATTRIBUTES) };
+static BOOL HasInitialized = FALSE;
+static CRITICAL_SECTION Initializing;
+static BCRYPT_ALG_HANDLE AlgProvider;
+
+static LPWSTR
+NormalizeStringAlloc(_In_ NORM_FORM NormForm, _In_z_ LPCWSTR Source)
+{
+    LPWSTR Result = NULL;
+    HANDLE Heap = GetProcessHeap();
+    int Len = NormalizeString(NormForm, Source, -1, NULL, 0);
+    for (int i = 0; i < 10; ++i)
+    {
+        if (Result)
+            HeapFree(Heap, 0, Result);
+        Result = HeapAlloc(Heap, 0, sizeof(WCHAR) * Len);
+        Len = NormalizeString(NormForm, Source, -1, Result, Len);
+        if (Len > 0)
+            return Result;
+        if (GetLastError() != ERROR_INSUFFICIENT_BUFFER)
+            break;
+        Len = -Len;
+    }
+    if (Result)
+        HeapFree(Heap, 0, Result);
+    return NULL;
+}
+
+static void
+Bin2Hex(_In_bytecount_(Size) const void *Source, size_t Size, _Out_capcount_(Size * 2) LPWSTR Destination)
+{
+    for (size_t i = 0; i < Size; ++i)
+    {
+        static const WCHAR nibble[] = L"0123456789ABCDEF";
+        *(Destination++) = nibble[(((unsigned char *)Source)[i] & 0xf0) >> 4];
+        *(Destination++) = nibble[(((unsigned char *)Source)[i] & 0x0f)];
+    }
+}
+
+static DWORD
+NamespaceRuntimeInit()
+{
+    DWORD Result;
+
+    EnterCriticalSection(&Initializing);
+    if (HasInitialized)
+    {
+        LeaveCriticalSection(&Initializing);
+        return ERROR_SUCCESS;
+    }
+
+    /* TODO: wireguard-go uses Blake2s hashing in tun\wintun\namespace_windows.go, unfortunately not available in
+     * Windows API. SHA-256 is used instead. */
+    if (!BCRYPT_SUCCESS(BCryptOpenAlgorithmProvider(&AlgProvider, BCRYPT_SHA256_ALGORITHM, NULL, 0)))
+    {
+        Result = ERROR_GEN_FAILURE;
+        goto cleanupLeaveCriticalSection;
+    }
+
+    ULONG SecDescrSize;
+    if (!ConvertStringSecurityDescriptorToSecurityDescriptorW(
+            L"O:SYD:P(A;;GA;;;SY)", 1, &SecurityAttributes.lpSecurityDescriptor, &SecDescrSize))
+    {
+        Result = GetLastError();
+        goto cleanupBCryptCloseAlgorithmProvider;
+    }
+    BYTE Sid[MAX_SID_SIZE];
+    DWORD SidSize = MAX_SID_SIZE;
+    if (!CreateWellKnownSid(WinLocalSystemSid, NULL, Sid, &SidSize))
+    {
+        Result = GetLastError();
+        goto cleanupSecurityDescriptor;
+    }
+
+    HANDLE Boundary = CreateBoundaryDescriptorW(L"Wintun", 0);
+    if (!Boundary)
+    {
+        Result = GetLastError();
+        goto cleanupSecurityDescriptor;
+    }
+    if (!AddSIDToBoundaryDescriptor(&Boundary, Sid))
+    {
+        Result = GetLastError();
+        goto cleanupSecurityDescriptor;
+    }
+
+    for (;;)
+    {
+        if (CreatePrivateNamespaceW(&SecurityAttributes, Boundary, L"Wintun"))
+            break;
+        Result = GetLastError();
+        if (Result == ERROR_ALREADY_EXISTS)
+        {
+            if (OpenPrivateNamespaceW(Boundary, L"Wintun"))
+                break;
+            Result = GetLastError();
+            if (Result == ERROR_PATH_NOT_FOUND)
+                continue;
+        }
+        goto cleanupSecurityDescriptor;
+    }
+
+    HasInitialized = TRUE;
+    Result = ERROR_SUCCESS;
+    goto cleanupLeaveCriticalSection;
+
+cleanupSecurityDescriptor:
+    LocalFree(SecurityAttributes.lpSecurityDescriptor);
+cleanupBCryptCloseAlgorithmProvider:
+    BCryptCloseAlgorithmProvider(AlgProvider, 0);
+cleanupLeaveCriticalSection:
+    LeaveCriticalSection(&Initializing);
+    return Result;
+}
+
+_Check_return_
+HANDLE
+TakeNameMutex(_In_z_ LPCWSTR Pool)
+{
+    HANDLE Mutex = NULL;
+
+    if (NamespaceRuntimeInit() != ERROR_SUCCESS)
+        return NULL;
+
+    /* TODO: wireguard-go uses Blake2s hashing in tun\wintun\namespace_windows.go, unfortunately not available in
+     * Windows API. SHA-256 is used instead. */
+    BCRYPT_HASH_HANDLE Sha256 = NULL;
+    if (!BCRYPT_SUCCESS(BCryptCreateHash(AlgProvider, &Sha256, NULL, 0, NULL, 0, 0)))
+        return NULL;
+    static const char mutex_label[] = "WireGuard Adapter Name Mutex Stable Suffix v1 jason@zx2c4.com";
+    if (!BCRYPT_SUCCESS(BCryptHashData(Sha256, (PUCHAR)mutex_label, sizeof(mutex_label) - sizeof(char), 0)))
+        goto cleanupSha256;
+    LPWSTR PoolNorm = NormalizeStringAlloc(NormalizationC, Pool);
+    if (!PoolNorm)
+        goto cleanupSha256;
+    /* TODO: wireguard-go hashes UTF-8 normalized pool name. We hash UTF-16 here. */
+    if (!BCRYPT_SUCCESS(BCryptHashData(Sha256, (PUCHAR)PoolNorm, (int)wcslen(PoolNorm), 0)))
+        goto cleanupPoolNorm;
+    BYTE Hash[32];
+    if (!BCRYPT_SUCCESS(BCryptFinishHash(Sha256, Hash, sizeof(Hash), 0)))
+        goto cleanupPoolNorm;
+    static const WCHAR MutexNamePrefix[] = L"Wintun\\Wintun-Name-Mutex-";
+    WCHAR MutexName[_countof(MutexNamePrefix) /*<= incl. terminator*/ + sizeof(Hash) * 2];
+    memcpy(MutexName, MutexNamePrefix, sizeof(MutexNamePrefix) - sizeof(WCHAR));
+    Bin2Hex(Hash, sizeof(Hash), MutexName + _countof(MutexNamePrefix) - 1);
+    MutexName[_countof(MutexName) - 1] = 0;
+    Mutex = CreateMutexW(&SecurityAttributes, FALSE, MutexName);
+    if (!Mutex)
+        goto cleanupPoolNorm;
+    switch (WaitForSingleObject(Mutex, INFINITE))
+    {
+    case WAIT_OBJECT_0:
+    case WAIT_ABANDONED:
+        goto cleanupPoolNorm;
+    }
+
+    CloseHandle(Mutex);
+    Mutex = NULL;
+cleanupPoolNorm:
+    HeapFree(GetProcessHeap(), 0, PoolNorm);
+cleanupSha256:
+    BCryptDestroyHash(Sha256);
+    return Mutex;
+}
+
+void
+ReleaseNameMutex(_In_ HANDLE Mutex)
+{
+    ReleaseMutex(Mutex);
+    CloseHandle(Mutex);
+}
+
+void
+NamespaceInit()
+{
+    InitializeCriticalSection(&Initializing);
+}
+
+void
+NamespaceCleanup()
+{
+    EnterCriticalSection(&Initializing);
+    if (HasInitialized)
+    {
+        LocalFree(SecurityAttributes.lpSecurityDescriptor);
+        BCryptCloseAlgorithmProvider(AlgProvider, 0);
+        HasInitialized = FALSE;
+    }
+    LeaveCriticalSection(&Initializing);
+    DeleteCriticalSection(&Initializing);
+}