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Keith Makan

"So you are interpreters of interpreters?" - Socrates, Ion by Plato

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Showing posts with the label Embedded Linux

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[Hardware] Reverse Engineering UART interfaces (Primer)

Posted by Keith Makan June 03, 2019

Embedded Embedded ARM Embedded Linux Hardware Hardware Engineering Hardware Reverse Engineering UART

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Introduction to the ELF Format (Part VII): Dynamic Linking / Loading and the .dynamic section

Posted by Keith Makan November 09, 2018

Dynamic Linking Dynamic Loading ELF ELF Format Embedded Linux Global Offset Table Linux Procedure Linkage Table Relocation Reverse Engineering Shared libraries Understanding ELF Format

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Introduction to The ELF Format (Part IV): Exploring Section Types and Special Sections

Posted by Keith Makan October 04, 2018

ELF Format Embedded Linux Executable Linkable Format Linux Reverse Engineering

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Introduction to the ELF File Format (Part III) : The Section Headers

Posted by Keith Makan September 25, 2018

ELF ELF Format Embedded Linux Linux Reverse Engineering

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Introduction to the ELF Format Part II : Understanding Program Headers

Posted by Keith Makan September 14, 2018

ELF Embedded Linux Executable Linkable Format Linux Reverse Engineering

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Popular Posts (Last Year)

Introduction to the ELF Format (Part VI) : The Symbol Table and Relocations (Part 1)

This post is part of a series on the ELF format, if you haven't checked out the other parts of the series here they are:

(Part I) : ELF Header https://blog.k3170makan.com/2018/09/introduction-to-elf-format-elf-header.html (Part II) : Program Headers https://blog.k3170makan.com/2018/09/introduction-to-elf-format-part-ii.html (Part III) : Section Header Table https://blog.k3170makan.com/2018/09/introduction-to-elf-file-format-part.html (Part IV) : Section Types and Special Sections https://blog.k3170makan.com/2018/10/introduction-to-elf-format-part-iv.html(Part V) : C Start up https://blog.k3170makan.com/2018/10/introduction-to-elf-format-part-v.htmlthis
In this and the next post I'm going to explore how Elf files manage to pull off the magic of symbol resolution as well as the format, offsets and records in the Elf that represent this information. There are many facets to this mechanism in the format, and before I get into each of them I'd like to provide a gentle intro …

Introduction to the ELF Format : The ELF Header (Part I)

ELF Files are charged with using their magic to perform two holy tasks in the linux universe. The first being to tell the kernel where to place stuff in memory from the ELF file on disk as well as providing ways to invoke the dynamic loaders functions and maybe even help out with some debugging information. Essentially speaking its telling the kernel where to put it in memory and also the plethora of tools that interpret the file where all the data structures are that hold useful information for making sense of the file. Anyway that's as far as I've figured it out - the actual break down is a little less simple.

I'll demonstrate why this is so here and over the next series of posts in the classic "Learn things by breaking them" style.
ELF Header and Identification fields The first thing that appears in an ELF file is of course the header, which is like most things in file formats just a list of offsets in the file. Its purpose is to indicate essentially what kin…

Introduction to the ELF Format (Part V) : Understanding C start up .init_array and .fini_array sections

This post is part of a series on the ELF format, if you haven't checked out the other parts of the series here they are:

(Part I) : ELF Header https://blog.k3170makan.com/2018/09/introduction-to-elf-format-elf-header.html (Part II) : Program Headers https://blog.k3170makan.com/2018/09/introduction-to-elf-format-part-ii.html (Part III) : Section Header Table https://blog.k3170makan.com/2018/09/introduction-to-elf-file-format-part.html (Part IV) : Section Types and Special Sections https://blog.k3170makan.com/2018/10/introduction-to-elf-format-part-iv.htmlthis
In this post I'm going to cover how some of the aspects of C start up and mess around with the .init_array and .fini_array sections to show how they work.

C Start Up
So something must happen to get your code in the main function running. This process is called the C start up and it essentially involves running all the initialize code, setting up pointers to some important arrays and then branching over to main.

What the…

Introduction to the ELF Format Part II : Understanding Program Headers

Welcome back folks! In the previous post I covered pretty much the most trivial parts of the ELF file format. In this post we are actually going to work with one of the most interesting mechanisms in the file - the program headers! I skipped some parts of the ELF header in the previous post and decided to cover them here specifically because they inform on the Program Headers anyway. Lets get started!
Introduction : What are Program Headers?
I mentioned in part 1 that the ELF format performs two tasks. A recipe for how to sublimate dead files into living processes and adds the bells and whistles needed to make the file look pretty to gdb, the dynamic loader and a bunch of other tools. Program Headers (among other functions) are more often for telling the memory loader where to put stuff. It also has some house keeping functions.

We'll get into how these memory loading powers and formats work a little later for now its just important to keep in mind a good idea of what to expect …

[Reverse Engineering Primer] Unpacking cramfs firmware file systems

Reverse engineering firmware from the point of view of an attacker involves levering as much as possible what is accessible from the physical board. Of course the classic question this strives to answer is, if someone gets hold of my board what could go wrong? Reverse engineering some devices in the wild often exposes security keys, default passwords and other forms of security failures that can expose an unfair escalation of privilege or perhaps also allow a complete take over of the device right down to boot loader level - all of this sometimes also possibly learned by analyzing the firmware.

I'm going to talk about some of the more basic skill in getting toward exposing the code and other sensitive artifacts used by the device. Before you can find remote code execs and admin auth by pass vulns you need to get to grips with firmware image formats and embedded file systems.

Setting up the environment
Before getting super in depth and writing our own file format parsers, machine …

Glibc Heap Exploitation Basics : ptmalloc2 internals (Part 3) : The Main Arena

Hi folks, this post is part of a series in which I try to explore the internals of glibc's implementation ptmalloc2 which is used for managing heap memory. In this post I'm going to specifically pay attention to the main_arena and the malloc_state structure, which is used to store some important pointers for searching heap memory.
The main arena The heap bakes the main_arena struct right into process memory. Its a struct of the type malloc_state and holds the following fields (extract from glibc-2.23/malloc/malloc.c):

1686 struct malloc_state
1687 {
1688 /* Serialize access. */
1689 mutex_t mutex;
1690
1691 /* Flags (formerly in max_fast). */
1692 int flags;
1693
1694 /* Fastbins */
1695 mfastbinptr fastbinsY[NFASTBINS];
1696
1697 /* Base of the topmost chunk -- not otherwise kept in a bin */
1698 mchunkptr top;
1699
1700 /* The remainder from the most recent split of a small request */
1701 mchunkptr last_remainder;
1702
1703 /* Normal bins packed as de…

Windows Exploit Development (primer) : Debugging Threads and Analyzing Memory

Hi folks I thought its about time to start blogging about the little experience I have in low level exploitation and analysis - so here goes. To start off on your windows exploitation journey you need to be able to get to grips with a tool and some tricks to get you look at your target the right way. In this post I cover somethings that may help a ton!
Debugging ThreadsTo get started you are probably going to need a couple things sorted out first, namely a simple windows VM setup with debug tools (tons of tutorials out there on the internet) and a target to exploit: A Windows VM (Microsoft made them free which is awesome!)Windows Debug ToolsYou should grab a copy of Easy MPEG to DVD Burner on exploit db.
Before we can start crashing programs and controlling EIPs we need to make sure we have the right view of the target we are exploiting. Windows debugger is actually pretty useful in this regard so open it up, open the target program and attach the debugger to it like so:

Once you've…

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