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This paper presents a systematic solution to the persistent problem of buffer overflow attacks. Buffer overflow attack gained notoriety in 1988 as part of the Morris Worm incident on the Internet [23]. Despite the fact that fixing individual buffer overflow vulnerabilities is fairly simple, buffer overflow attacks continue to this day, as reported in the SANS Network Security Digest:

Buffer overflows appear to be the most common problems reported in May, with degradation-of-service problems a distant second. Many of the buffer overflow problems are probably the result of careless programming, and could have been found and corrected by the vendors, before releasing the software, if the vendors had performed elementary testing or code reviews along the way.[4]

The base problem is that, while individual buffer overflow vulnerabilities are simple to patch, the vulnerabilities are profligate. Thousands of lines of legacy code are still running as privileged daemons (SUID root) that contain numerous software errors. New programs are being developed with more care, but are often still developed using unsafe languages such as C, where simple errors can leave serious vulnerabilities.

The continued success of these attacks is also due to the ``patchy'' nature by which we protect against such attacks. The life cycle of a buffer overflow attack is simple: A (malicious) user finds the vulnerability in a highly privileged program and someone else implements a patch to that particular attack, on that privileged program. Fixes to buffer overflow attacks attempt to solve the problem at the source (the vulnerable program) instead of at the destination (the stack that is being overflowed).

This paper presents StackGuard, a systematic solution to the buffer overflow problem. StackGuard is a simple compiler extension that limits the amount of damage that a buffer overflow attack can inflict on a program. Programs compiled with StackGuard are safe from buffer overflow attack, regardless of the software engineering quality of the program.

Section 2 describes buffer overflow attacks in detail. Section 3 details how StackGuard defends against buffer overflow attacks. Section 4 presents performance and penetration testing of StackGuard-enhanced programs. Section 5 discusses some of the abstract ideas represented in StackGuard, and their implications. Section 6 describes related work in defending against buffer overflow attack. Finally, Section 7 presents our conclusions.

next up previous
Next: Buffer Overflow Attacks Up: StackGuard: Automatic Adaptive Detection Previous: Abstract

Crispin Cowan
Tue Dec 9 16:04:30 PST 1997