Posts From Category: Code

BinPeek - an app to determine if a #Windows executable is managed or unmanaged.

BinPeek is an application that checks to see if a Windows application is managed(.NET) or unmanaged(native). It handles x86 and x84 executables. If doing it manually, you must check several values in the PE (Portable Executable) file header that differ slightly based on whether the executable is 32-bit or 64-bit. BinPeek does that work for you.

Usage

D:\source\repos\BinPeek>binpeek BinPeek.exe
BinPeek.exe --> Unmanaged

Project Page on Github

Install

Build with Visual Studio or just use the release version in the repo.

License

MIT

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#ruby code to access the @haveibeenpwned api.

This is just some ruby I whipped up really quickly to access the API of havibeenpwned.com which is a cool new site by Troy Hunt that aggregates password dump information from breaches and allows you to search for your email address.

I think the code is pretty self-explanatory, but comment or send me a line if you have questions/suggestions/criticism/etc!

require 'mechanize'
require 'addressable/uri'

agent = Mechanize.new

File.open('addresses.txt').each do |line|
  line = line.chomp
  begin
    target = "http://haveibeenpwned.com/api/breachedaccount/#{line}"
    page = agent.get Addressable::URI.parse(target)
  rescue Mechanize::ResponseCodeError  => e
    case e.response_code
      when '404'
        puts "#{line} => Not Found"
      when '400'
        puts "#{line} => Bad Request"
      else
        puts "#{line} => #{e.message}"
     end
  else
    puts "#{line} => #{page.content}"
  end
end

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Fun with C++ - Placement New

So, for some reason in the last few days I’ve been thinking about the old days of when I was a developer and really into C/C++. One of the things that I found interesting was placement new. In a nutshell it’s a way that you can instantiate a new object, but specify where in memory it will go. There are some interesting cases where it’s necessary such as cases where you might try to optimize by pre-allocating a bunch of memory and then re-using it. Kind of managing your own memory space. Anyway, this example shows how it’s done.

#include "stdafx.h"


class Foo
{
public:
  Foo() { strncpy(message, "Hello, World", 12);}
  void * operator new (size_t, void * p) throw() { return p ; }
  void operator delete (void *, void *) throw() { }
  void printMessage() { printf("message is - %s\n", message); }
private:
  char message[13];
};

int _tmain(int argc, _TCHAR* argv[])
{
  char buf[sizeof(Foo)];
  memset(buf, 0, sizeof(buf));
  Foo *f = new((void *)buf) Foo();
  printf("address of buf - %x\n", buf);
  printf("address of f - %x\n", f);
  printf("contents of buf - %s\n", buf);
  f->printMessage();
  buf[0] = 'h';
  f->printMessage();
  f->~Foo();
  return 0;
}

Line 8 defines the constructor that placement new uses.

Line 9 defines the destructor.

Line 17 creates a buffer that is the size of a Foo object.

Line 19 instantiates a Foo object, but uses the buffer as the address of where the object will be instantiated.

Lines 20 and 21 print the addresses of the buffer and of f (the new object). They are the same.

Line 22 prints the contents of the buf, which is “Hello, World”. This is the value of the message variable in the object.

Line 23 prints the message.

Line 24 changes the first character in buf to be ‘h’. This should change it within f as well.

Line 25 shows that it changed.

Line 26 explicitly calls the destructor. That needs to be done when using placement new.

That’s about it! The example created a buffer, created an object in that buffer, changed the buffer, and showed that the object changed. Fun stuff!

Running it on my machine show-

address of buf - 31fbe0
address of f - 31fbe0
contents of buf - Hello, World
message is - Hello, World
message is - hello, World

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How to do dynamic loading on Windows

So, after hitting DerbyCon a few weeks ago and going to some of the malware talks, I was reminded of my Windows programming days and decided to shake the rust off and do some examples. Today’s example is of how to load a dll dynamically in Windows.

The following is an example function that I created and put in a DLL called DynamicLoadedDLL.dll. The actual creation of the project and how to build is beyond the scope of this post. But, basically I created an empty solution and added a Win32 Project called DynamicLoadedDLL and specified the type DLL.

The code for the DLL in DynamicLoadedDLL.cpp is-

#include "stdafx.h"

extern "C"
{
	__declspec( dllexport ) int AddTwo(int a, int b)
	{
		return a + b;
	}
}

Basically what that does is define a function called AddTwo that takes two integers and returns their sum. __declspec( dllexport ) tells the compiler to add the function to the Export Address Table so that it is exposed as a function in the DLL. The “extern “C”” block on line 3 tells the compiler to expose it without the C++ name mangling. This makes it callable by many different languages. If you want to see the difference of having it vs. not, first open a developer command prompt and go to the output directory. Run the command “dumpbin /exports DynamicLoadedDLL.dll” and see what it shows. Then remove the “extern “C”” block, build, and repeat.

Then I created a Win32 Console app in the same solution called DynamicLoader and it’s code is-

#include "stdafx.h"

typedef int (*AddTwo)(int, int);

int _tmain(int argc, _TCHAR* argv[])
{
	HMODULE hLib = LoadLibrary(TEXT("DynamicLoadedDLL.dll"));
	printf("\r\nDynamicLoadedDLL.dll loaded into memory at 0x%x\r\n", hLib);

	AddTwo AT = (AddTwo) GetProcAddress(hLib, "AddTwo");
	printf("AddTwo method loaded into memory at 0x%x\r\n", AT);
	printf("6 + 5 = %d\r\n", AT(6,5));
        CloseHandle(hLib);
	return 0;
}

Line 3 defines the function pointer. It says create a type called AddTwo that is a pointer to a function that takes 2 integers as a parameter and returns an integer. If you were statically linking to a library, you would have the header file and the lib file and wouldn’t need to do this. Line 7 is how we load the library into memory. It looks in the standard Windows search path for the library. If it can load the library the hLib parameter actually points to where the library is loaded in the memory space of the process as demonstrated by line 8. Line 10 gets the address of the “AddTwo” function from the library and creates a function called AT that points to it. Line 11 shows the address of the function in memory. Line 12 calls the function and prints the result. Line 13 closes the handle to the library. Error checking has been left out for brevity.

The output is-

DynamicLoadedDLL.dll loaded into memory at 0x585c0000
AddTwo method loaded into memory at 0x585c1010
6 + 5 = 11

If you run “dumpbin /imports” on DynamicLoader.exe you won’t see any reference to DynamicLoadedDLL.dll at all.

That’s pretty much it!

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