Feature: Make section count configurable, fix RTC error, and expose DetourIsFunctionImported (#225)

A few minor changes:

- Expose detour_is_imported via a new public function DetourIsFunctionImported
- Make certain runtime checks happy by masking pbTarget before casting to smaller type
- Enable user to compile with a different number of supported section headers (leaves default at 32)

src/detours.cpp

@@ -1395,6 +1395,12 @@ PVOID WINAPI DetourAllocateRegionWithinJumpBounds(_In_ LPCVOID pbTarget,
     return pbNewlyAllocated;
 }
 
+BOOL WINAPI DetourIsFunctionImported(_In_ PBYTE pbCode,
+                                     _In_ PBYTE pbAddress)
+{
+    return detour_is_imported(pbCode, pbAddress);
+}
+
 static PDETOUR_TRAMPOLINE detour_alloc_trampoline(PBYTE pbTarget)
 {
     // We have to place trampolines within +/- 2GB of target.
@@ -1437,7 +1443,8 @@ static PDETOUR_TRAMPOLINE detour_alloc_trampoline(PBYTE pbTarget)
     // We need to allocate a new region.
 
     // Round pbTarget down to 64KB block.
-    pbTarget = pbTarget - (PtrToUlong(pbTarget) & 0xffff);
+    // /RTCc RuntimeChecks breaks PtrToUlong.
+    pbTarget = pbTarget - (ULONG)((ULONG_PTR)pbTarget & 0xffff);
 
     PVOID pbNewlyAllocated =
         detour_alloc_trampoline_allocate_new(pbTarget, pLo, pHi);

src/detours.h

@@ -381,7 +381,11 @@ extern const GUID DETOUR_EXE_RESTORE_GUID;
 extern const GUID DETOUR_EXE_HELPER_GUID;
 
 #define DETOUR_TRAMPOLINE_SIGNATURE             0x21727444  // Dtr!
-typedef struct _DETOUR_TRAMPOLINE DETOUR_TRAMPOLINE, *PDETOUR_TRAMPOLINE;
+typedef struct _DETOUR_TRAMPOLINE DETOUR_TRAMPOLINE, *PDETOUR_TRAMPOLINE;
+
+#ifndef DETOUR_MAX_SUPPORTED_IMAGE_SECTION_HEADERS
+#define DETOUR_MAX_SUPPORTED_IMAGE_SECTION_HEADERS      32
+#endif // !DETOUR_MAX_SUPPORTED_IMAGE_SECTION_HEADERS
 
 /////////////////////////////////////////////////////////// Binary Structures.
 //
@@ -454,9 +458,9 @@ typedef struct _DETOUR_EXE_RESTORE
 #endif
 #ifdef IMAGE_NT_OPTIONAL_HDR64_MAGIC    // some environments do not have this
         BYTE                raw[sizeof(IMAGE_NT_HEADERS64) +
-                                sizeof(IMAGE_SECTION_HEADER) * 32];
+                                sizeof(IMAGE_SECTION_HEADER) * DETOUR_MAX_SUPPORTED_IMAGE_SECTION_HEADERS];
 #else
-        BYTE                raw[0x108 + sizeof(IMAGE_SECTION_HEADER) * 32];
+        BYTE                raw[0x108 + sizeof(IMAGE_SECTION_HEADER) * DETOUR_MAX_SUPPORTED_IMAGE_SECTION_HEADERS];
 #endif
     };
     DETOUR_CLR_HEADER   clr;
@@ -590,7 +594,9 @@ PVOID WINAPI DetourCopyInstruction(_In_opt_ PVOID pDst,
 BOOL WINAPI DetourSetCodeModule(_In_ HMODULE hModule,
                                 _In_ BOOL fLimitReferencesToModule);
 PVOID WINAPI DetourAllocateRegionWithinJumpBounds(_In_ LPCVOID pbTarget,
-                                                  _Out_ PDWORD pcbAllocatedSize);
+                                                  _Out_ PDWORD pcbAllocatedSize);
+BOOL WINAPI DetourIsFunctionImported(_In_ PBYTE pbCode,
+                                     _In_ PBYTE pbAddress);
 
 ///////////////////////////////////////////////////// Loaded Binary Functions.
 //

tests/test_module_api.cpp

@@ -728,4 +728,29 @@ TEST_CASE("DetourRestoreAfterWithEx", "[module]")
     // TODO: Needs to be written.
 }
 
+// Define the import symbol so that we can get the address of the IAT entry for a static import
+#ifdef _X86_
+#pragma warning(disable:4483) // disable warning/error about __identifier(<string>)
+#define __imp_SetLastError      __identifier("_imp__SetLastError@4")
+#endif
+
+extern "C" extern void *__imp_SetLastError;
+
+TEST_CASE("DetourIsFunctionImported", "[module]")
+{
+    SECTION("Passing NULL code pointer, results in false")
+    {
+        REQUIRE(!DetourIsFunctionImported(NULL, reinterpret_cast<PBYTE>(&__imp_SetLastError)));
+    }
+    
+    SECTION("Passing NULL target, results in false")
+    {
+        REQUIRE(!DetourIsFunctionImported(reinterpret_cast<PBYTE>(&__ImageBase), NULL));
+    }
+    
+    SECTION("Passing imported function, results in true")
+    {
+        REQUIRE(DetourIsFunctionImported(reinterpret_cast<PBYTE>(&__ImageBase), reinterpret_cast<PBYTE>(&__imp_SetLastError)));
+    }
+}