A buffer overflow, or buffer overrun, is an anomaly where a program, while writing data to a buffer, overruns the buffer's boundary and overwrites adjacent memory.

learn more… | top users | synonyms

40
votes
7answers
19k views

How to explain buffer overflow to a layman

Every once in a while (when I think out loud and people overhear me) I am forced to explain what a buffer overflow is. Because I can't really think of a good metaphor, I end up spending about 10 ...
36
votes
8answers
3k views

Should I bother teaching buffer overflows any more?

The students are skeptical that turning off non-executable stacks, turning off canaries and turning off ASLR represents a realistic environment. If PaX, DEP, W^X, etc., are effective at stopping ...
35
votes
2answers
5k views

What is the most hardened set of options for GCC compiling C/C++?

What set of GCC options provide the best protection against memory corruption vulnerabilities such as Buffer Overflows, and Dangling Pointers? Does GCC provide any type of ROP chain mitigation? Are ...
34
votes
3answers
21k views

Stack Overflows - Defeating Canaries, ASLR, DEP, NX

To prevent buffer overflows, there are several protections available such as using Canary values, ASLR, DEP, NX. But, where there is a will, there is a way. I am researching on the various methods an ...
19
votes
2answers
4k views

How can vending machines be hacked? And how can I prevent it?

I am developing a vending machine and want to make it secure. In a comment to my previous question, @Polynomial said "Vending machines (and similar devices) can often be pwned via buffer overflows on ...
16
votes
5answers
5k views

Would the Heartbleed bug have been prevented if OpenSSL was written in Go/D/Vala?

IIUC the Heartbleed vulnerability happens due to a bug in the C source code of OpenSSL, by performing a memcpy() from a buffer that is too short. I'm wondering if the bug would have been prevented ...
16
votes
4answers
921 views

Does compiling from sources “kinda” protects from buffer overflow attacks?

While discussing buffers overflows, somebody told me that compiling your own binary for an application (with specific compilation flags) instead of using the "mainstream binary" makes it more ...
16
votes
4answers
751 views

Tricky code to make memory-safe

I'm designing a homework challenge for students who are learning about memory safety and writing secure C code. As part of this, I am looking for a small programming task where it's non-trivial to ...
15
votes
1answer
2k views

Return-oriented programming: how to find a stack pivot

I have a program with a heap overflow. It contains some code that is not randomized (is not using ASLR). I want to do a return-oriented programming exploit. Since this is a heap overflow, the first ...
12
votes
3answers
1k views

Bypassing Address Space Layout Randomization

How effective is ASLR in preventing arbitrary code execution in a buffer overflow type exploit? How hard is it for an attacker to bypass this without simply guessing where the addresses are?
11
votes
4answers
2k views

Adding 65K buffer to protect from buffer overflows?

If you had a very complex and important function in C that you wanted to protect, would it be worth it to put a 65K buffer at the top of the stack to protect from buffer overflows? You would put your ...
10
votes
7answers
4k views

Secure memcpy for pure C

Buffer overflows are nothing new. And yet they still appear often, especially in native (i.e. not managed) code... Part of the root cause, is usage of "unsafe" functions, including C++ staples ...
10
votes
1answer
1k views

Exploiting buffer overflow leads to segfault

I am trying to exploit simple stack overflow vulnerability. I have a basic code in c: #include <cstring> int main( int argc, char** argv ) { char buffer[500]; strcpy(buffer, ...
10
votes
2answers
554 views

AMD64 overflows and null bytes

In the past, I have managed to overflow my own vulnerable programs, and those of others, but only ever in a 32bit environment. Every time I try even a simple stack smash on a 64bit machine, I run into ...
9
votes
4answers
692 views

Why don't computers check whether there are memory contents in some memory space?

Buffer overflow occurs because it writes to memory spaces that are used by, or will be used by other parts of the program. Computer programs usually write to the memorylocation that has been ...
9
votes
4answers
5k views

How is printf() in C/C++ a Buffer overflow vulnerability?

According to an article I just read, the functions printf and strcpy are considered security vulnerabilities due to Buffer overflows. I understand how strcpy is vulnerable, but could someone possibly ...
8
votes
4answers
664 views

Evading IDS in exploit development

In the context of buffer overflow exploit development, I was asked: Discuss how your exploit may be modified to evade an Intrusion Detection System. I'm not asking for my homework to be done, but ...
7
votes
2answers
451 views

Why are buffer overflows executed in the direction they are?

I'm following The Security Tube’s video here. He overviews buffer overflows, and mentions how memory is executed from highest to lowest in the stack (at least with his implementation I assume). So we ...
7
votes
3answers
716 views

Remote return into libc attack

It is often shown that non-executable data segemnts are possible to bypass through return-to-libc attacks. It's evident on /bin/sh but is it also possible to invoke a remote shell?
7
votes
2answers
477 views

How stack smashing is prevented?

I just read AlephOne's paper on smashing the stack, and implemented it on my machine (Ubuntu 12.04), it was a bit old so had to take a lot of help from the internet but I enjoyed it. Now, I want to ...
7
votes
1answer
645 views

How does ASCII-Armoring help to prevent buffer-overflow attacks?

I was reading about return-to-libc attacks at Wikipedia. According to what I read and understood from the article, ASCII armoring means that binary data is converted into ASCII values by grouping ...
7
votes
1answer
502 views

Sulley - optional element and command check

I'm currently using Sulley to fuzz my FTP server, but I'm having problems. I want to specify the STRU command, which has a syntax: STRU [<SP> F|R|P] <CRLF> I tried to specify the ...
6
votes
1answer
483 views

stack buffer overflow in the main function? [closed]

I am trying to exploit a stack based overflow vulnerability. All the examples I can find make use of a ret address though. The buffer overflow I found is inside the main function, and I cannot find ...
6
votes
3answers
5k views

How to get this to buffer overflow?

I'm trying to understand buffer overflow, and am working with a simple piece of code, as below. #include <stdlib.h> #include <stdio.h> #include <string.h> int bof(char *str) { ...
6
votes
3answers
346 views

Buffer overflow stack adjustment

I am quite new to buffer overflows and I am practicing right now different types of buffer overflow attacks. the shellcode was not executed until it was padded with NOPs although its set properly in ...
6
votes
3answers
421 views

What is a buffer overflow?

I'm learning C in a tutorial and have reached the point where the term "buffer" s being mentioned regularly. It has also mentioned how certain bad programming practises involving memory can be ...
6
votes
2answers
113 views

Modify C code with buffer overflow vulnerability to skip code

I'm trying to find a way to exploit the buffer overflow vulnerability in the following source code so the line, printf("x is 1") will be skipped: #include <stdio.h> #include <stdlib.h> ...
5
votes
1answer
2k views

“Hello World” example of a Buffer Overflow attack in many programming languages

I'm looking for a very simple application that has an intentional Buffer Overflow embedded in it. I'm assuming this possible in systems where DEP and ASLR are not being used Ideally (and if ...
5
votes
1answer
293 views

Information disclosure attack, using a heap overflow

A typical strategy for defeating ASLR is to find both a buffer overflow bug and an information disclosure bug. But when attacking servers that are automatically restarted whenever they crash/die, is ...
5
votes
2answers
415 views

On Hawkes' technique to bypass canaries

I found this reference to bypass canaries: http://sota.gen.nz/hawkes_openbsd.pdf It recommends to brute force the canary byte-for-byte. I don't understand how this works: "Technique is to brute force ...
5
votes
1answer
397 views

Stack canaries protection and ROP

As far as I know stack canaries are values written on the stack that, if overwritten by a buffer overflow, force the application to close at return. My question is: if I overwrite both EIP and stack ...
5
votes
1answer
674 views

ROP Exploitation on ARM

I was wondering about since, Ret2Libc attack doesn't works on ARM, and we have to rely on ROP for that. How different is ROP on ARM from the x86 architecture. Are there any tools, such as mona.py ...
5
votes
1answer
123 views

Return oriented programming without int 0x80

I have a program with a stack based buffer overflow. It is running PIE with ASLR and DEP, however there is a section of executable code that is at a fixed location. However, this region does not ...
4
votes
2answers
668 views

Smashing the stack if it grows upwards

As we know that on most of the processor architectures, the stack grows downwards. Hence, memory exploits involving smashing of stack and buffer overflow and their explanation make sense. Just ...
4
votes
1answer
709 views

Explaining a buffer overflow vulnerability in C

Given this C program: #include <stdio.h> #include <string.h> int main(int argc, char **argv) { char buf[1024]; strcpy(buf, argv[1]); } Built with: gcc -m32 -z execstack prog.c -o ...
4
votes
1answer
779 views

Is this fprintf statement potentially vulnerable?

Here's the statement: fprintf(stderr, "Some random string\n"). Is it okay not to have a format specifier, such as %s, even though the statement doesn't take any user input? Is it still potentially ...
4
votes
2answers
1k views

Do I always have to overwrite EIP to get to write on the stack in a buffer overflow?

Do I always have to overwrite EIP to get to write on the stack in a buffer overflow? How's the memory organized? I can't find a proper graph with google
4
votes
3answers
735 views

Is writing shellcode still a valid skill to have/learn?

Following up from this question: Should I bother teaching buffer overflows any more? I am a it sec researcher and also security course instructor. Recently questions have been raised about the ...
4
votes
1answer
552 views

NX bit causes segfault on NOP slide?

doing an assignment for university. We have to exec a shell on a remote server. We're told the NX bit is not set, however, when we redirect to our injected code, the server has a segmentation fault. ...
4
votes
1answer
967 views

buffer/heap overflow - register of what is executed

When buffer overflow/heap overflow is executed, is EIP the one that tells which part will be executed next? Also, when exploiting the part that has buffer overflow vulnerability, after execution, will ...
4
votes
3answers
7k views

Finding environment variables with gdb, to exploit a buffer overflow

I have to exploit a very simple buffer overflow in a vulnerable C++ program for an assignment and I am not being able to find the environment variable SHELL. I have never worked with BoF before, and ...
4
votes
1answer
527 views

How to implement canaries to prevent buffer overflows?

This is probably a very basic question. I've read about canaries, and how they work in theory. You have a global variable that you set to a random number in the prolog of a function, do your function, ...
4
votes
1answer
70 views

Buffer Overflow due to wrong data type

I am reading the OWASP page on buffer overflow. It mentions: buffer overflow can be prevented using higher-level programming languages that are strongly typed and developer should validate input to ...
4
votes
1answer
194 views

Why are countermeasures against control-flow hijacking attacks mostly implemented in software?

I wonder why countermeasures against code-injection and control-flow hijacking attacks (e.g. stack-based buffer overflows and heap-based buffer overflows) are mostly implemented in software. Examples ...
4
votes
1answer
725 views

Is a return to libc attack possible without the system function?

Every return to libc buffer overflow attack I've seen uses the system function to execute commands. I have an executable with DEP enabled (I can't execute on the stack) and the system function isn't ...
4
votes
1answer
257 views

How do attackers gather remote feedback for identifying and exploiting buffer overflows?

Local buffer overflows are relatively easy to understand: throw some input at an interface and see if the process fails with a core dump or similar. However, in my mind, this kind of exploit works ...
4
votes
2answers
289 views

Heap canaries, to protect function pointers in heap objects

I'm wondering if anyone has previously proposed, evaluated, or deployed the following measure to harden systems against heap-based buffer overruns: basically, stack canaries, but applied before ...
4
votes
1answer
223 views

What to do next for this possible buffer overflow?

I've been instructed to test a few of our newer applications before user release, and managed to find a buffer overflow on one of the fields. Here is where I've run into a brick wall though, and ...
3
votes
5answers
2k views

What programming language does this code use?

Watching this article: http://www.exploit-db.com/exploits/13474/ I can see this: /* * NetBSD * execve() of /bin/sh by humble of Rhino9 */ char shellcode[] = "\xeb\x23" "\x5e" "\x8d\x1e" ...
3
votes
2answers
132 views

how do compilers detect buffer overflow?

I just started researching about security at the systems level and challenges, especially with respect to low level languages such as C/C++ and objective c. I have understood buffer overflow and how ...