EvanMcBroom

Encrypting Strings at Compile Time

Thank you to SpecterOps for supporting this research and to Duane and Matt for proofreading and editing! Crossposted on the SpecterOps Blog.

TLDR: You may use this header file for reliable compile time string encryption without needing any additional dependencies.

Programmers of DRM software, security products, or other sensitive code bases are commonly required to minimize the amount of human readable strings in binary output files. The goal of the minimization is to hinder others from reverse engineering their proprietary technology.

Common approaches that are taken to meet this requirement often add an additional maintenance burden to the developer and are prone to error. These approaches will be presented along with t

EvanMcBroom

/*
* Research by Evan McBroom and Chris Thompson (@_Mayyhem)
* Roger Zander made security recommendations for SCCM based on the claim that NAA credentials could be recovered.
* Source: https://rzander.azurewebsites.net/network-access-accounts-are-evil/
* Roger stated that recover was "possible with a few lines of code" but did not provide any code. Here is working code.
*/

#include <Windows.h>
#include <stdio.h>

EvanMcBroom

PIC and String Literals Part 2

I previously wrote about how to use macro metaprogramming to simplify using string literals in position independent code (PIC). The results are summarized in the below code snippet and the article can be read on GitHub.

void f() {
    // Example 1: The Pic idiom for instantiating a string
    char picString1[]{ 'a', 'b', 'c' };

EvanMcBroom

// Copyright (C) 2022 Evan McBroom
// If you are using Visual Studio, you will need to disable the "Edit and Continue" feature.

// Prng based off of Parker Miller's
// "Multiplicative Linear Congruential Generator"
// https://en.wikipedia.org/wiki/Lehmer_random_number_generator
namespace mlcg {
    constexpr uint32_t modulus() {
        return 0x7fffffff;
    }

EvanMcBroom

IllBeBack - An Undocumented Function

Microsoft purchased the software Softricity SoftGrid in 2006 and renamed it to Microsoft Application Virtualization, or App-V for short. Windows shipped with several libraries in System32 and SysWOW64 to support App-V.

AppVTerminator.dll

One App-V library stands out from all the rest because it only has one exported function named IllBeBack... That's right! A library signed by Microsoft, with Terminator in the name, that only has a single callable function named IllBeBack.

EvanMcBroom

Position Independent Code and String Literals

A common programming idiom when writing position independent code (PIC) is to expand a string literal into its individual characters when instantiating a local variable.

void f() {
    // Example 1: A normal instantiation with a string literal
    char a[]{ "a long string" };

 // Example 2: The Pic idiom for instantiating a string

EvanMcBroom

Switch Statements with Full Strings

C++11 introduced the constexpr keyword for defining a constant expression. A constant expression is a variable or function that may be evaluated at compile time. This has many uses, including extending a switch statement to support full strings.

Constant Expression Hash Functions

C++ only supports using an integer as the condition in a switch statement and an integer that is known at compile time in a case statement. You can define a hash function and use it to convert a string to an integer to use in a switch statement. If you define that hash function as a constexpr you can use it to convert a string literal to an integer to use in a case statement as well.

EvanMcBroom

FireEye Red Team Tools - Notes

These are my notes on FireEye's yara rules for it's red team's tools.

These are the public projects that I could identify to be directly associated with a tool:

Project	Source
AndrewSpecial	https://github.com/hoangprod/AndrewSpecial
BloodHound	https://github.com/BloodHoundAD/BloodHound