基于段长限制的缓冲区溢出保护

为防范缓冲区溢出攻击,在Intel 32位CPU及Windows系统下实现了不可执行堆栈。设计了一个内核驱动程序,将应用程序的堆栈移动到代码区的上部,并修改代码段的限长将堆栈区排除在代码段之外。堆栈中的攻击代码被执行时,CPU就会触发一个保护异常,攻击代码不能继续执行。这种方法能够防范各种已知及未知的堆栈溢出攻击,性能开销低于基于页的防护方式。     

Memory monitor module for embedded systems

Embedded systems are vulnerable to buffer overflow attacks. In this paper, we propose a hardware memory monitor module that aims to detect buffer overflow attacks by analyzing the security of an embedded processor at the instruction level. The functionality of the memory monitor module does not rely on the source code and can perform security check through dynamic methods. Compared with several existing countermeasures that protect only part of the program’s data space, our proposed memory monitor module can protect the program’s entire data space. The proposed memory monitor module has negligible performance overhead because it runs in parallel with the embedded processor. As demonstrated in an FPGA (Field Programmable Gate Array) based prototype, the experimental results show that our memory monitor module can effectively resist several types of buffer overflow attacks with approximately a 15% hardware cost overhead and only a 0.1% performance penalty.     

SigFree: A Signature-Free Buffer Overflow Attack Blocker

We propose SigFree, an online signature-free out-of-the-box application-layer method for blocking code-injection buffer overflow attack messages targeting at various Internet services such as web service. Motivated by the observation that buffer overflow attacks typically contain executables whereas legitimate client requests never contain executables in most Internet services, SigFree blocks attacks by detecting the presence of code. Unlike the previous code detection algorithms, SigFree uses a new data-flow analysis technique called code abstraction that is generic, fast, and hard for exploit code to evade. SigFree is signature free, thus it can block new and unknown buffer overflow attacks; SigFree is also immunized from most attack-side code obfuscation methods. Since SigFree is a transparent deployment to the servers being protected, it is good for economical Internet-wide deployment with very low deployment and maintenance cost. We implemented and tested SigFree; our experimental study shows that the dependency-degree-based SigFree could block all types of code-injection attack packets (above 750) tested in our experiments with very few false positives. Moreover, SigFree causes very small extra latency to normal client requests when some requests contain exploit code.     

基于Linux系统的Apache服务器安全对策

Apacheweb具有良好的跨平台性和极强的可扩展性,功能强大。虽然Apache也存在诸如拒绝服务攻击、缓冲区溢出攻击、非法获得root权限等安全缺陷。讨论了从Linux系统的安全入手并加强Apache服务器的配置,对安全漏洞采取积极的防范措施,从而提高Apacheweb安全性的方法。     

嵌入式网络安全设备的抗缓冲区溢出攻击机制

缓冲区溢出攻击已经成为网络安全威胁中最为严重的一类,而嵌入式网络安全设备则更需要有抗缓冲区溢出攻击的能力.在分析了缓冲区溢出的基本原理以及抗缓冲区溢出攻击的方法后,提出建立全新的嵌入式网络安全设备的安全架构,并构建多层次的抗缓冲区溢出攻击机制.根据网络安全设备的特点和特殊需求,详细阐述了适合嵌入式网络安全设备需要的多层次,全方位的抗缓冲区溢出攻击机制.     

Automatic Buffer Overflow Warning Validation

Static buffer overflow detection techniques tend to report too many false positives fundamentally due to the lack of software execution information. It is very time consuming to manually inspect all the static warnings. In this paper, we propose BovInspector, a framework for automatically validating static buffer overflow warnings and providing suggestions for automatic repair of true buffer overflow warnings for C programs. Given the program source code and the static buffer overflow warnings, BovInspector first performs warning reachability analysis. Then, BovInspector executes the source code symbolically under the guidance of reachable warnings. Each reachable warning is validated and classified by checking whether all the path conditions and the buffer overflow constraints can be satisfied simultaneously. For each validated true warning, BovInspector provides suggestions to automatically repair it with 11 repair strategies. BovInspector is complementary to prior static buffer overflow discovery schemes. Experimental results on real open source programs show that BovInspector can automatically validate on average 60% of total warnings reported by static tools.

     

SeBROP: blind ROP attacks without returns

Currently, security-critical server programs are well protected by various defense techniques, such as Address Space Layout Randomization(ASLR), eXecute Only Memory(XOM), and Data Execution Prevention(DEP), against modern code-reuse attacks like Return-oriented Programming(ROP) attacks. Moreover, in these victim programs, most syscall instructions lack the following ret instructions, which prevents attacks to stitch multiple system calls to implement advanced behaviors like launching a remote shell. Lacking this kind of gadget greatly constrains the capability of code-reuse attacks. This paper proposes a novel code-reuse attack method called Signal Enhanced Blind Return Oriented Programming(SeBROP) to address these challenges. Our SeBROP can initiate a successful exploit to server-side programs using only a stack overflow vulnerability. By leveraging a side-channel that exists in the victim program, we show how to find a variety of gadgets blindly without any pre-knowledges or reading/disassembling the code segment. Then, we propose a technique that exploits the current vulnerable signal checking mechanism to realize the execution flow control even when ret instructions are absent. Our technique can stitch a number of system calls without returns, which is more superior to conventional ROP attacks. Finally, the SeBROP attack precisely identifies many useful gadgets to constitute a Turing-complete set. SeBROP attack can defeat almost all state-of-the-art defense techniques. The SeBROP attack is compatible with both modern 64-bit and 32-bit systems. To validate its effectiveness, We craft three exploits of the SeBROP attack for three real-world applications, i.e., 32-bit Apache 1.3.49, 32-bit ProFTPD 1.3.0, and 64-bit Nginx 1.4.0. Experimental results demonstrate that the SeBROP attack can successfully spawn a remote shell on Nginx, ProFTPD, and Apache with less than 8500/4300/2100 requests, respectively.     

"Patch on demand" saves even more time? [network security]

Zero-day attacks are those for which users receive no prior warning and thus have no preventive measures in place. We integrate the vulnerability discovery, patch generation, and patch application cycles into a system that automatically detects a new attack, analyzes its modus operandi, determines the best software patch, and applies it at the desired level of granularity LAN, enterprise, or Internet-wide. We develop a vaccination system that automatically generates patches to protect an application's source code.     

Defeating buffer overflow attacks via virtualization

Buffer overflow defenses have been comprehensively studied for many years. Different from previous solutions, we propose PHUKO, an on-the-fly buffer overflow prevention system which leverages virtualization technology. PHUKO offers the protected program a fully transparent environment and an easy deployment without the need to restart the program. Generally, the working process of PHUKO can be divided into two stages. First, we utilize static binary analysis to identify the instructions offline which are the entries of vulnerable functions. Second, by combining virtual machine introspection and online patching, PHUKO instruments the protected running program on-the-fly with memory safety enforcement. The experiments show that our system can defend against realistic buffer overflow attacks effectively with a moderate performance overhead.     

基于缓冲区溢出的网络渗透技术的研究

网络安全是当今计算机网络研究的热点,而基于缓冲区溢出的网络渗透技术则是严重威胁网络安全的行为之一.详细介绍了缓冲区溢出的原理,并采用跳转指令的方法阐述了Widows环境下缓冲区溢出的实现过程,最后探讨了相关的防范措施,对于有效防范缓冲区溢出攻击有着积极的作用.     

面向Linux的内核级代码复用攻击检测技术

近年来,代码复用攻击与防御成为安全领域研究的热点.内核级代码复用攻击使用内核自身代码绕过传统的防御机制.现有的代码复用攻击检测与防御方法多面向应用层代码复用攻击,忽略了内核级代码复用攻击.为有效检测内核级代码复用攻击,提出了一种基于细粒度控制流完整性（CFI）的检测方法.首先根据代码复用攻击原理和正常程序控制流构建CFI约束规则,然后提出了基于状态机和CFI约束规则的检测模型.在此基础上,基于编译器辅助实现CFI标签指令插桩,并在Hypervisor中实现CFI约束规则验证,提高了检测方法的安全性.实验结果表明该方法能够有效检测内核级代码复用攻击,并且性能开销不超过60%.     

基于源代码的缓冲区溢出预防技术

基于缓冲区溢出的攻击是一种常见的安全攻击手段,也是目前惟一最重要最常见的安全威胁。在所有的软件安全漏洞中,缓冲区溢出漏洞大约占一半。该文从编程的角度分析了缓冲区溢出攻击,并提出在源代码阶段尽量避免缓冲区溢出的方法。     

缓冲区溢出漏洞分析技术研究进展

本文首先介绍了缓冲区溢出漏洞危害的严重性和广泛性,然后从如何利用缓冲区溢出漏洞的角度,依次介绍了缓冲区溢出漏洞的定义、操作系统内存组织方式以及缓冲区溢出攻击方式.本文将缓冲区溢出分析技术分为三类：自动检测、自动修复、以及运行时防护,并对每一类技术进行了介绍、分析和讨论.最后,对相关工作进行了总结,并讨论了缓冲区溢出分析领域未来可能的三个研究方向：（1）对二进制代码进行分析.（2）结合机器学习算法进行分析.（3）综合利用多种技术进行分析.     

缓冲区溢出分析及其防范策略研究

缓冲区溢出是一种在各种操作系统和应用软件中广泛存在且危害较大的漏洞。分析了缓冲区溢出攻击的原理,讨论了基于缓冲区溢出的攻击方式和一般规律以及攻击代码的植入方式,给出了防范缓冲区溢出攻击的策略和措施。     

一种缓冲区溢出攻击描述语言的研究与设计

分析目前缓冲区溢出攻击的弱点,提出一种新的攻击方法。通过抽象缓冲区溢出攻击的规律,分析植入代码的结构特征,给出缓冲区溢出攻击描述语言的文法。对于不同的缓冲区溢出漏洞,攻击描述语言能够动态地构造植入代码,实现攻击的自动化。     

Secure Bit: Transparent, Hardware Buffer-Overflow Protection

We propose a minimalist, architectural approach, Secure Bit (patent pending), to protect against buffer overflow attacks on control data (return-address and function-pointer attacks in particular). Secure Bit provides a hardware bit to protect the integrity of addresses for the purpose of preventing such buffer-overflow attacks. Secure Bit is transparent to user software: it provides backward compatibility with legacy user code. It can detect and prevent all address-corrupting buffer-overflow attacks with little runtime performance penalty. Addresses passed in buffers between processes are marked insecure, and control instructions using those addresses as targets will raise an exception. An important differentiating aspect of our protocol is that, once an address has been marked as insecure, there is no instruction to remark it as secure. Robustness and transparency are demonstrated by emulating the hardware, booting Linux on the emulator, running application software on that Linux, and performing known attacks     

A Behavior-based Buffer Overflow Attack Blocker

A common way to gain control of victim hosts is to launch buffer overflow attacks by remote exploits.This paper proposes a behavior-based buffer overflow attacker blocker,which can dynamically detect and prevent remote buffer overflow attacks by filtering out the client requests that contain malicious executable codes.An important advantage of this approach is that it can block the attack before the exploit code begins affecting the target program.The blocker is composed of three major components,packet dec...     

一种基于程序逻辑结构分析的缓冲区溢出攻击抵御方法

本文针对缓冲区溢出攻击提出了一种有效的抵御方法。该方法通过分析程序的逻辑结构试图发现所有可能的缓冲区,对这些缓冲区的访问进行跟踪,并插入必要的边界检查代码。与已有的方法相比,该方法具有较好的兼容性和性能方面的优势。     

一种抗地址淹没的缓冲区栈溢出算法

缓冲区溢出是常见的网络漏洞攻击,其中最重要的是栈溢出攻击。通过分析缓冲区溢出攻击的方法和特点,提出一种基于StackShield改进的RetProtect算法,首先利用IDA Pro对源程序反汇编分析,然后建立新的库函数,并通过修改gcc源代码来实现程序执行时对函数返回地址的备份的方法来检测缓冲区溢出攻击的发生。与其它栈溢出攻击检测方法相比,RetProtect算法可有效地阻止对返回地址进行淹没的栈溢出攻击,对用户透明,系统兼容性好。     

基于动态二进制平台的缓冲区溢出过程分析

提出一种基于动态二进制平台的缓冲区溢出过程分析方法,并实现基于该方法的原型系统。分析缓冲区溢出攻击方法的特点,给出基于异常捕获、控制流分析和内存状态检查的溢出检测方法。通过对内存读写指令、控制转移指令进行监控,获得函数调用序列和数据传递关系,定位导致缓冲区溢出的代码。实验结果表明,该系统能有效检测缓冲区溢出,准确定位导致溢出的代码位置。