Application hooking (winsock) from c++/c#

Question

I got an (old) application that calls to the winsocket function:

struct hostent* FAR gethostbyname(
  __in  const char *name
);

It currently imports it as ws32_dll.#52 instead the normal name calling.

My intention is just to be able to do something like opening a messagebox when a host search happens (which should be at app start).

I tried to create a c++ dll with the pragma comments pointing to #52 and putting it on the app dir (including a "exe.local" and "exe.manifest" files to try to redirect it) but it loaded the c:\windows\system32 instead.

After that, i created a c# project launching the process itself(hence getting the PID from the Process object), adding the easyhook dll to it.

I checked the example at: http://www.codeproject.com/KB/DLL/EasyHook64.aspx

Changing the calls to:

    FileMon.FileMonInterface Interface;
    LocalHook CreateFileHook;
    Stack<String> Queue = new Stack<String>();

    public Main(
        RemoteHooking.IContext InContext,
        String InChannelName)
    {
        // connect to host...

        Interface = 
          RemoteHooking.IpcConnectClient<FileMon.FileMonInterface>(InChannelName);
    }

    public void Run(
        RemoteHooking.IContext InContext,
        String InChannelName)
    {
        // install hook...
        try
        {
            CreateFileHook = LocalHook.Create(
                LocalHook.GetProcAddress("ws2_32.dll", "gethostbyname"),
                new DCreateFile(GetHostByName_Hooked),
                this);

            CreateFileHook.ThreadACL.SetExclusiveACL(new Int32[] { 0 });
        }
        catch (Exception ExtInfo)
        {
            Interface.ReportException(ExtInfo);

            return;
        }

        Interface.IsInstalled(RemoteHooking.GetCurrentProcessId());

        // wait for host process termination...
        try
        {
            while (true)
            {
                Thread.Sleep(500);

                // transmit newly monitored file accesses...
                if (Queue.Count > 0)
                {
                    String[] Package = null;

                    lock (Queue)
                    {
                        Package = Queue.ToArray();

                        Queue.Clear();
                    }

                    Interface.OnCreateFile(RemoteHooking.GetCurrentProcessId(), Package);
                }
                else
                    Interface.Ping();
            }
        }
        catch
        {
            // NET Remoting will raise an exception if host is unreachable
        }
    }


    [UnmanagedFunctionPointer(CallingConvention.StdCall,
        CharSet = CharSet.Auto,
        SetLastError = true)]
    delegate IntPtr DGetHostByName(
        String name);

    // just use a P-Invoke implementation to get native API access
    // from C# (this step is not necessary for C++.NET)
    [DllImport("ws2_32.dll",
        CharSet = CharSet.Auto,
        SetLastError = true,
        CallingConvention = CallingConvention.StdCall)]
    static extern IntPtr gethostbyname(
        String name);

    // this is where we are intercepting all file accesses!
    static IntPtr GetHostByName_Hooked(
        String name)
    {
        try
        {
            Main This = (Main)HookRuntimeInfo.Callback;
            MessageBox.Show("hi!");


        }
        catch
        {
        }

        // call original API...
        return GetHostByName(
            name);
    }
}

}

(may have made typos writing it here, but project compiled succesfully @ home).

The thing is that i dunno what I need to do the hooking this methods<-> the application itself.

I mean.. what lefts to just do the hooking with c# easyhook (assuming the app is "foo.exe")? Do i need to create a custom dll for easyhook?(in that case, what content do i need to define inside?)

I found it a bit... "complex" for a helloworld hook,hehe.

Thanks in advance ;)

Answer 1

In the end, using the "Gray hack python" book taugh me how to make all this with fewer lines, and just the same i wanted.

No exe yet but... that's it.

Using pydbg + hooks.