api: add debugging rundll32 entry point

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

5 files changed, 117 insertions, 15 deletions

diff --git a/api/api.vcxproj b/api/api.vcxproj
index b93990d..af28a41 100644
--- a/api/api.vcxproj
+++ b/api/api.vcxproj
@@ -100,6 +100,11 @@
     <CodeAnalysisRuleSet>NativeRecommendedRules.ruleset</CodeAnalysisRuleSet>
     <RunCodeAnalysis>true</RunCodeAnalysis>
   </PropertyGroup>
+  <PropertyGroup Condition="'$(Configuration)'=='Debug'" Label="Configuration">
+    <LocalDebuggerCommand>rundll32.exe</LocalDebuggerCommand>
+    <LocalDebuggerCommandArguments>$(OutDir)$(TargetName)$(TargetExt),DoThingsForDebugging</LocalDebuggerCommandArguments>
+    <DebuggerFlavor>WindowsLocalDebugger</DebuggerFlavor>
+  </PropertyGroup>
   <ItemDefinitionGroup>
     <ClCompile>
       <PreprocessorDefinitions>_WINDOWS;_USRDLL;%(PreprocessorDefinitions)</PreprocessorDefinitions>
@@ -164,6 +169,7 @@
     <ClInclude Include="ntldr.h" />
     <ClInclude Include="registry.h" />
     <ClInclude Include="resource.h" />
+    <ClInclude Include="session.h" />
     <ClInclude Include="wintun.h" />
   </ItemGroup>
   <ItemGroup>
@@ -194,4 +200,4 @@
   <Target Name="CleanSignTarget">
     <Delete Files="$(IntermediateOutputPath)$(TargetName).sign" />
   </Target>
-</Project>
\ No newline at end of file
+</Project>
diff --git a/api/api.vcxproj.filters b/api/api.vcxproj.filters
index c1db346..7d29920 100644
--- a/api/api.vcxproj.filters
+++ b/api/api.vcxproj.filters
@@ -58,6 +58,9 @@
     <ClInclude Include="entry.h">
       <Filter>Header Files</Filter>
     </ClInclude>
+    <ClInclude Include="session.h">
+      <Filter>Header Files</Filter>
+    </ClInclude>
   </ItemGroup>
   <ItemGroup>
     <ClCompile Include="namespace.c">
diff --git a/api/rundll32.c b/api/rundll32.c
index 2b2f11d..d594723 100644
--- a/api/rundll32.c
+++ b/api/rundll32.c
@@ -5,15 +5,23 @@
 
 #include "adapter.h"
 #include "logger.h"
+#include "session.h"
 #include "wintun.h"
 
 #include <Windows.h>
 #include <cfgmgr32.h>
 #include <objbase.h>
+#include <assert.h>
 
 #define EXPORT comment(linker, "/EXPORT:" __FUNCTION__ "=" __FUNCDNAME__)
 
-#ifdef ACCEPT_WOW64
+#if defined(ACCEPT_WOW64) || defined(_DEBUG)
+
+static
+#ifndef _DEBUG
+const
+#endif
+BOOL WriteToConsole = FALSE;
 
 static DWORD
 WriteFormatted(_In_ DWORD StdHandle, _In_z_ const WCHAR *Template, ...)
@@ -22,19 +30,18 @@ WriteFormatted(_In_ DWORD StdHandle, _In_z_ const WCHAR *Template, ...)
     DWORD SizeWritten;
     va_list Arguments;
     va_start(Arguments, Template);
-    WriteFile(
-        GetStdHandle(StdHandle),
-        FormattedMessage,
-        sizeof(WCHAR) * FormatMessageW(
-                            FORMAT_MESSAGE_FROM_STRING | FORMAT_MESSAGE_ALLOCATE_BUFFER,
-                            Template,
-                            0,
-                            0,
-                            (void *)&FormattedMessage,
-                            0,
-                            &Arguments),
-        &SizeWritten,
-        NULL);
+    DWORD Len = sizeof(WCHAR) * FormatMessageW(
+                                    FORMAT_MESSAGE_FROM_STRING | FORMAT_MESSAGE_ALLOCATE_BUFFER,
+                                    Template,
+                                    0,
+                                    0,
+                                    (void *)&FormattedMessage,
+                                    0,
+                                    &Arguments);
+    if (WriteToConsole)
+        WriteConsoleW(GetStdHandle(StdHandle), FormattedMessage, Len, &SizeWritten, NULL);
+    else
+        WriteFile(GetStdHandle(StdHandle), FormattedMessage, Len, &SizeWritten, NULL);
     LocalFree(FormattedMessage);
     va_end(Arguments);
     return SizeWritten / sizeof(WCHAR);
@@ -141,4 +148,35 @@ cleanup:
     Done();
 }
 
+#ifdef _DEBUG
+VOID __stdcall DoThingsForDebugging(HWND hwnd, HINSTANCE hinst, LPSTR lpszCmdLine, int nCmdShow)
+{
+#    pragma EXPORT
+    UNREFERENCED_PARAMETER(hwnd);
+    UNREFERENCED_PARAMETER(hinst);
+    UNREFERENCED_PARAMETER(lpszCmdLine);
+    UNREFERENCED_PARAMETER(nCmdShow);
+
+    AllocConsole();
+    WriteToConsole = TRUE;
+    Init();
+    GUID TestGuid = {
+        0xdeadbabe,
+        0xcafe,
+        0xbeef,
+        { 0x01, 0x23, 0x45, 0x67, 0x89, 0xab, 0xcd, 0xef }
+    };
+    WINTUN_ADAPTER *Adapter;
+    BOOL RebootRequired = FALSE;
+    assert(WintunCreateAdapter(L"Wintun", L"Test", &TestGuid, &Adapter, &RebootRequired) == ERROR_SUCCESS);
+    assert(!RebootRequired);
+    TUN_SESSION *Session;
+    HANDLE ReadWait;
+    assert(WintunStartSession(Adapter, WINTUN_MIN_RING_CAPACITY, &Session, &ReadWait) == ERROR_SUCCESS);
+    WintunEndSession(Session);
+    assert(WintunDeleteAdapter(Adapter, TRUE, &RebootRequired) == ERROR_SUCCESS);
+    assert(!RebootRequired);
+}
+#endif
+
 #endif
diff --git a/api/session.c b/api/session.c
index 67772f0..940a9ff 100644
--- a/api/session.c
+++ b/api/session.c
@@ -7,6 +7,7 @@
 #include "elevate.h"
 #include "entry.h"
 #include "logger.h"
+#include "session.h"
 #include "wintun.h"
 #include <Windows.h>
 
diff --git a/api/session.h b/api/session.h
new file mode 100644
index 0000000..735b927
--- /dev/null
+++ b/api/session.h
@@ -0,0 +1,54 @@
+/* SPDX-License-Identifier: GPL-2.0
+ *
+ * Copyright (C) 2018-2020 WireGuard LLC. All Rights Reserved.
+ */
+
+#pragma once
+
+#include "wintun.h"
+#include <Windows.h>
+
+typedef struct _TUN_SESSION TUN_SESSION;
+
+/**
+ * @copydoc WINTUN_START_SESSION_FUNC
+ */
+WINTUN_STATUS WINAPI
+WintunStartSession(
+    _In_ const WINTUN_ADAPTER *Adapter,
+    _In_ DWORD Capacity,
+    _Out_ TUN_SESSION **Session,
+    _Out_ HANDLE *ReadWait);
+
+/**
+ * @copydoc WINTUN_END_SESSION_FUNC
+ */
+void WINAPI
+WintunEndSession(_In_ TUN_SESSION *Session);
+
+/**
+ * @copydoc WINTUN_RECEIVE_PACKET_FUNC
+ */
+WINTUN_STATUS WINAPI
+WintunReceivePacket(_In_ TUN_SESSION *Session, _Out_bytecapcount_(*PacketSize) BYTE **Packet, _Out_ DWORD *PacketSize);
+
+/**
+ * @copydoc WINTUN_RECEIVE_RELEASE_FUNC
+ */
+void WINAPI
+WintunReceiveRelease(_In_ TUN_SESSION *Session, _In_ const BYTE *Packet);
+
+/**
+ * @copydoc WINTUN_ALLOCATE_SEND_PACKET
+ */
+WINTUN_STATUS WINAPI
+WintunAllocateSendPacket(
+    _In_ TUN_SESSION *Session,
+    _In_ DWORD PacketSize,
+    _Out_bytecapcount_(PacketSize) BYTE **Packet);
+
+/**
+ * @copydoc WINTUN_SEND_PACKET
+ */
+void WINAPI
+WintunSendPacket(_In_ TUN_SESSION *Session, _In_ const BYTE *Packet);