Buffer Overflows

Buffer Overflow

Buffer Overflows Internet Security Whitepapers

In this paper we discuss how buffer overflow vulnerabilities are exploited, how operating system properties are used in favor of attackers, how poor programming language constructs produce harder to detect but easily exploitable code, and discuss solutions proposed to avoid vulnerable code. Although buffer overflow has been the popular vulnerability there are others that can be just as effective, such as input validation and format string vulnerabilities. In comparison, both these methods are easier to detect and fix than buffer overflow. In this paper we focus on buffer overflow vulnerabilities; readers interested in format string vulnerabilities are referred to [Ref].

Buffer Overflow Study Attacks and Defenses

Buffer Overflows Internet Security Whitepapers Exploit Writing Techniques

Most of the exploits based on buffer overflows aim at forcing the execution of malicious code, mainly in order to provide a root shell to the user. The principle is quite simple: malicious instructions are stored in a buffer, which is overflowed to allow an unexpected use of the process, by altering various memory sections. Thus, we will introduce in this document the way a process is mapped in the machine memory, as well as the buffer notion; then we will focus on two kinds of exploits based on buffer overflow : stack overflows and heap overflows.

Buffer Overflows Attacks and Defenses for the Vulnerability of the Decade

Buffer Overflows Internet Security Whitepapers Exploit Writing Techniques

Buffer overflows have been the most common form of security vulnerability for the last ten years. More over, buffer overflow vulnerabilities dominate the area of remote network penetration vulnerabilities, where an anonymous Internet user seeks to gain partial or total control of a host. If buffer overflow vulnerabilities could be effectively eliminated, a very large portion of the most serious security threats would also be eliminated. In this paper, we survey the various types of buffer overflow vulnerabilities and attacks, and survey the various defensive measures that mitigate buffer overflow vulnerabilities, including our own StackGuard method. We then consider which combinations of techniques can eliminate the problem of buffer overflow vulnerabilities, while preserving the functionality and performance of existing systems.

Defending Against Arbitrary Code Insertion and Execution

Buffer Overflows Internet Security Whitepapers

Buffer Overflows are one of the most common and potentially deadly forms of attack against computer systems to date. They allow an attacker to locally or remotely inject malicious code into a system and compromise its security. They arise out of poor programming practices and buggy software. First seen in the Internet Worm of 1987 they can occur on all major platforms (UNIX, Linux, Win32, and Solaris) and all major architectures (Intel, Alpha and MIPS). There are in fact many variations of buffer overflows but this paper will deal with the most basic and common type, i.e. stack based overflows. Other types include heap-based overflows, frame pointer overflows and adjacent memory space overflows. These however are beyond the scope of this paper. I will begin with observing how this vulnerability arises before assessing what methods are used to prevent such occurrences from being able to happen. Throughout this paper I will be using C code examples and x86 Assembly Language examples (coded in the Intel syntax, the AT&T syntax is messy). All examples are intended to work on a Win32 system but should be portable to Linux unless otherwise stated.

Different Techniques to Prevent Buffer Overflow

Buffer Overflows Internet Security Whitepapers

A buffer overflow is a phenomenon that takes place when a program or process stores more data in a buffer than it can hold. Since buffers are designed with a finite size, usually it overwrites the memory addresses which may hold some valid data or instructions. Basically buffer overflow can be occurred through stack overflow or heap overflow. Though buffer overflow occurs due to lack of carefulness or accidentally but it can done a lot of harms such as sending new instructions to the affected systems through which he/she can corrupt user’s files, delete/change valuable data or retrieve secret information. In the meanwhile, buffer overflow has raised the software vulnerabilities and has become a great panic in case of software security.

Exploits: The Why and How

Buffer Overflows Internet Security Whitepapers

Buffer overflow exploits are the tool of choice of today’s attacker. These exploits have the most power, are the easiest to use, and are all too common. Buffer overflows constitute the largest single threat to enterprises today. (1) Buffer overflow exploits are very common. There are hundreds of known unchecked buffers that can be overflowed by hackers with more being discovered all the time. Over 60% of CERT advisories deal with buffer overflow exploits. (2) Buffer overflow exploits are easy to use. Nearly anyone (12 year olds and script kiddies included) can download buffer overflow attack code and follow a simple “recipe” to execute it. No advanced technical knowledge is necessary to run pre-written buffer overflow exploit code. (3) Buffer overflow exploits are very powerful. In many cases, the malicious code that executes as a result of a buffer overflow will run with administrator-level privileges, and therefore can do anything it wants to the server.

Four Different Tricks to Bypass StackShield and StackGuard Protection

Buffer Overflows Internet Security Whitepapers

Stack shielding technologies have been developed to protect programs against exploitation of stack based buffer overflows. Among different types of protections, we can separate two major groups. Those that modify the environment where applications are executed, for example PaX now integrated into the OpenWall project, and those that alter the way programs are compiled. We will focus on the last group, specially in StackGuard, StackShield, and Microsoft’s new stack smashing protection. Techniques that exploit stack based buffer overflows on protected programs and environment have been presented in the past. Here we’ll describe how the studied protections work, and then we’ll present four more tricks to bypass stack smashing protections, some of which are extentions of older techniques, and some we think are novel.

Web Application Security - Buffer Overflows

Buffer Overflows Internet Security Whitepapers

Buffer overflows occur when more data is written to memory than was allocated by the program. In other words, the programmer was responsible for properly managing memory and made a common error. It doesn’t take much of an overflow to impact a system. As little as one byte of data can cause a security incident. The scary thing is, buffer overflow vulnerabilities are one of the most popular targets of criminal hackers.