My project needs to inspect .c and .dll files. it combines those informations to determine what it is supposed to call and then calls that.
I need to inspect the dlls to find which dll has which function. I have gotten so far as to map the dll to memory without initialising it. now i need to map the header to something so i can read out the section that has the callable names in it.
how can i do that? this is the code so far:
[DllImport("kernel32.dll")]
static extern IntPtr LoadLibraryEx(string lpFileName, IntPtr hReservedNull, LoadLibraryFlags dwFlags);
public static string[] GetFKTNames(string dll)
{
IntPtr lib = LoadLibraryEx(dll, IntPtr.Zero, LoadLibraryFlags.DONT_RESOLVE_DLL_REFERENCES);
//INDICATES WHAT I WANT TO DO, BUT DOES NOT WORk
//Header header = GetHeader(lib);
//Unload(lib);
//return header.Names;
}
EDIT #2:
i made a little bit of progress and quit it for today... there are 4 free days coming up here in germany...
i am not entirely sure if that marshalling is correct - i had no way to test it. I would love to read a book on that topic - so please comment if you know a good book that explains how that headerstuff works and what different headers are out there.
private static List<string> ListDLLFunctions(string sADllName)
{
List<string> names = new List<string>();
IntPtr LoadedImage = LoadLibraryEx(sADllName, IntPtr.Zero, LoadLibraryFlags.DONT_RESOLVE_DLL_REFERENCES);
IMAGE_NT_HEADERS header = (IMAGE_NT_HEADERS) Marshal.PtrToStructure(libPtr, typeof(IMAGE_NT_HEADERS));
// ImageExportDirectory = (_IMAGE_EXPORT_DIRECTORY*)
// ImageDirectoryEntryToData(LoadedImage.MappedAddress,
// false, IMAGE_DIRECTORY_ENTRY_EXPORT, &cDirSize);
// if (ImageExportDirectory != NULL)
// {
// dNameRVAs = (DWORD *)ImageRvaToVa(LoadedImage.FileHeader,
// LoadedImage.MappedAddress,
// ImageExportDirectory->AddressOfNames, NULL);
// for(size_t i = 0; i < ImageExportDirectory->NumberOfNames; i++)
// {
// sName = (char *)ImageRvaToVa(LoadedImage.FileHeader,
// LoadedImage.MappedAddress,
// dNameRVAs[i], NULL);
// slListOfDllFunctions.push_back(sName);
// }
// }
FreeLibrary(LoadedImage);
return names;
}
static void Main(string[] args)
{
List<string> names = ListDLLFunctions("KERNEL32.DLL");
}
I solved the problem for my usecase:
I load the lib into momory, copy it into a bytearray and then investigate it using PE information.
There are a couple of useful ressources for this topic that helped me a lot:
In retrospec i get how i could have used the other approaches to get my information. The Class that i have written is great to learn PE and explore some dlls, i recommand rewriting it if you want to get the grip of how the PE works.
Here is the Class:
public class DLLHelper
{
private byte[] dllInMemory;
private UInt32 PESizeOfImage;
private UInt32 VA_PE;
[DllImport("kernel32.dll")]
static public extern IntPtr LoadLibraryEx(string lpFileName, IntPtr hReservedNull, LoadLibraryFlags dwFlags);
[DllImport("kernel32.dll")]
static public extern bool FreeLibrary(IntPtr hModule);
public enum LoadLibraryFlags : uint
{
DONT_RESOLVE_DLL_REFERENCES = 0x00000001,
LOAD_IGNORE_CODE_AUTHZ_LEVEL = 0x00000010,
LOAD_LIBRARY_AS_DATAFILE = 0x00000002,
LOAD_LIBRARY_AS_DATAFILE_EXCLUSIVE = 0x00000040,
LOAD_LIBRARY_AS_IMAGE_RESOURCE = 0x00000020,
LOAD_WITH_ALTERED_SEARCH_PATH = 0x00000008
}
public DLLHelper(string dllpath)
{
PESizeOfImage = GetDllSizeInMemory(dllpath);
dllInMemory = GetDLLCopy(dllpath, PESizeOfImage);
UInt32 VA_p_PE = 0x3C;
VA_PE = Get4ByteFromLocation(VA_p_PE, dllInMemory);
}
private byte[] GetDLLCopy(string dllpath, uint PESizeOfImage)
{
IntPtr libPtr = LoadLibraryEx(dllpath, IntPtr.Zero, LoadLibraryFlags.DONT_RESOLVE_DLL_REFERENCES);
byte[] dllInMemory = new byte[PESizeOfImage];
Marshal.Copy(libPtr, dllInMemory, 0, (int)PESizeOfImage);
FreeLibrary(libPtr);
return dllInMemory;
}
private UInt32 GetDllSizeInMemory(string dllpath)
{
byte[] dllpreload = File.ReadAllBytes(dllpath);
UInt32 pp_PE = 0x3C;
UInt32 p_PE = Get4ByteFromLocation(pp_PE, dllpreload);
UInt32 p_PEOPTIONALHEADER = p_PE + 0x18;
UInt32 p_PESizeOfImage = p_PEOPTIONALHEADER + 0x38;
return Get4ByteFromLocation(p_PESizeOfImage, dllpreload);
}
public void DumpToFile(String filename)
{
File.WriteAllBytes(filename, dllInMemory);
}
public string GetDLLName()
{
UInt32 VAExport = GetVAExport(VA_PE, dllInMemory);
UInt32 VAName = GetVAName(VAExport, dllInMemory);
String Name = GetString(VAName, dllInMemory);
return Name;
}
public List<String> GetFunctionNames()
{
List<String> fkts = new List<String>();
UInt32 VAExport = GetVAExport(VA_PE, dllInMemory);
UInt32 VA_p_firstFKT = GetVA_p_firstFKT(VAExport, dllInMemory);
UInt32 VA_p_lastFKT = GetVA_p_lastFKT(VAExport, dllInMemory);
for (UInt32 VA_p_fkt = VA_p_firstFKT; VA_p_fkt <= VA_p_lastFKT; VA_p_fkt += sizeof(UInt32))
{
UInt32 VA_fkt = Get4ByteFromLocation(VA_p_fkt, dllInMemory);
fkts.Add(GetString(VA_fkt, dllInMemory));
}
return fkts;
}
private UInt32 GetVA_p_lastFKT(UInt32 VAExport, byte[] dllInMemory)
{
UInt32 first = GetVA_p_firstFKT(VAExport, dllInMemory);
UInt32 count = GetfktCount(VAExport, dllInMemory);
UInt32 last = first + (count - 1) * sizeof(UInt32);
return last;
}
private UInt32 GetfktCount(UInt32 VAExport, byte[] dllInMemory)
{
UInt32 RVA_Count = 0x14;
UInt32 VA_Count = VAExport + RVA_Count;
return Get4ByteFromLocation(VA_Count, dllInMemory);
}
private UInt32 GetVA_p_firstFKT(UInt32 VAExport, byte[] dllInMemory)
{
UInt32 RVA_p_FIRST = 0x20;
UInt32 VA_p_FIRST = VAExport + RVA_p_FIRST;
return Get4ByteFromLocation(VA_p_FIRST, dllInMemory);
}
private UInt32 GetVAName(UInt32 VAExport, byte[] dllInMemory)
{
UInt32 RVA_p_NAME = 0x0C;
UInt32 VA_p_NAME = VAExport + RVA_p_NAME;
return Get4ByteFromLocation(VA_p_NAME, dllInMemory);
}
private UInt32 GetVAExport(UInt32 VAPE, byte[] dllInMemory)
{
UInt32 RVA_p_EXPORT = 0x78;
UInt32 VA_p_EXPORT = VAPE + RVA_p_EXPORT;
return Get4ByteFromLocation(VA_p_EXPORT, dllInMemory);
}
string GetString(UInt32 location, byte[] dll)
{
int length = 0;
while (dll[location + length] != 0x00)
{
length++;
}
if (location > int.MaxValue) throw new Exception("uncastable");
return Encoding.UTF8.GetString(dll, (int)location, length);
}
private UInt32 Get4ByteFromLocation(UInt32 location, byte[] dll)
{
if (!(BitConverter.IsLittleEndian))
{
byte[] partial = GetByteSubset(4, location, dll);
Array.Reverse(partial);
return BitConverter.ToUInt32(partial, 0);
}
return BitConverter.ToUInt32(dll, (int)location);
}
private byte[] GetByteSubset(int size, UInt32 location, byte[] dll)
{
byte[] val = new byte[size];
for (int i = 0; i < size; i++)
{
val[i] = dll[location + i];
}
return val;
}
}