Linux Kernel Exploitation Part 3: Ret2Usr and SMEP

Introduction

I’d like to talk about the ret2usr attack in Linux kernel exploitation and the corresponding Supervisor Mode Execution Prevention (SMEP). Rather than detailing the exploitation details in control flow hijacking, this post will explain what is ret2usr attack and what is the expected behaviour from SMEP.
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Towards Automated Generation of Exploitation Primitives for Web Browsers

Introduction

This is a paper published in ACSAC 2018. In this paper, the author introduces a method to automatically generate exploitation primitives during the web browser exploitation. In this paper, the author uses CVE-2016-9079 as an example to demonstrate their work, which happens to be analysed in my post before.
In this post, I’d like to take this chance to give some academic definitions about those jargons in our previous posts. One interesting thing about this paper is that the paper is put into the session of web security not software security during the conference. ~~~OO~~~
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From Collision To Exploitation:Unleashing Use-After-Free Vulnerabilities in Linux Kernel

Introduction

This paper was published in CCS 2015. With the introduction of the various mitigation deployed in the user space, especially sandbox, the vulnerability in the linux kernel has become a target of the attacker. However, the memory space in the kernel is hard to predict since the kernel space are used by various tasks. In this paper, the author introduces a much stabler way to put desired vulnerable target into kernel memory space by exploiting a use-after-free in linux kernel.
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Linux Kernel Exploitation Part 2: Buddy Allocator and SLUB Allocator

Introduction

I will continue to talk about the exploitation of CVE-2017-7308. In this post, I will discuss the implementation details of buddy allocator and SLUB allocator in Linux-4.10.6. I will show how to put the victim object (struct packet_sock in this post) next adjacent to the vulnerable buffer (packet rv_ring buffer in previous post).
In [3], a general abstraction of Linux Kernel memory management is given as following picture. From the picture, we can find that two types of allocators (slab allocator and buddy allocator) are provided for Linux kernel functions. For both allocators, I will give some debugging info to give a straight view on how those objects are allocated and shaped in memory combined with some explanation on the source code.
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Linux Kernel Exploitation Part 1: Setting Up Debugging Environment

Introduction

These days I think there is still necessity to write a tutorial series on Linux Kernel exploitation and hope to summarize the kernel exploitation techniques as following:
(1) Kernel Debugging
(2) Return-oriented-Programming in Kernel
(3) Kernel Mitigation: KASLR, SMEP, SMAP
(4) Kernel Space Memory Allocator: SLAB Allocator
In this post, I will introduce how to debug a Linux Kernel via CVE-2017-7308 [1], including setting up debugging environment, root cause analysis and exploit primitive analysis.
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Analysis on CVE-2017-3000

Introduction

In this post, I will introduce CVE-2017-3000, a CVE assigned to us last year. We analyse the weak implementation of the PRNG in Flash Player, which is used for constant blinding in its JIT compiler. We find two methods circumventing the constant blinding. Furthermore, we give a detailed exploitation plan on how to insert desired value into JIT code even if constant blinding is in place as demonstrated on the cover page. In this post, I will give details on the design of the PRNG and full exploit based on CVE-2015-5122.
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