Questions tagged [stack-overflow]
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Does VxWorks has a stack canary mechanism?
I'm trying to understand if VxWorks has the ability to support stack canary protection. I couldn't find any info on that.
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bufferoverflow chars gets replaced on stack
So I try to understand stack based buffer-overflow but now I am stuck. This is the vulnerable function (32 bit ELF).
int test(char* input)
{
char buf[100];
printf("Buffer is at %p\n",...
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2
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259
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Is Stack Exchange immune to DDoS and DoS attacks?
I have heard that DDoS and DoS attacks work most of the time and that they are used when SQL insertion and other methods fail. I know Stack Exchange has a lot of programmers, and that they have this ...
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Why are stack canaries not enabled by default on GCC?
I'm trying to understand why stack canaries are not enabled by default. It makes sense to me that they should be, given the interest in security? https://stackoverflow.com/questions/49693870/stack-...
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Buffer Overflow with ROP Chain Output Problem
I have the following problem: I have this C program and I have done buffer overflow using ROP gadgets. I have a problem with the output.
I want to stop the printf() call in the vuln function to get ...
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1
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Stack vs Heap exploit, which have more CVE documented?
I tried to google this topic but most of them are conflicting each other. On the other side, I found a case where I can use either stack (local variable) or heap for a dynamic string. It's C by the ...
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Heap overflow - strcpy() on x86_64 (64bit)
I'm stuck on the Heap1 challenge from Exploit Education.
After compiling the source code in a 64bit system, without any security mechanism, I try to overflow the heap in order to overwrite the main ...
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What can you do against fortify-source (stack overflow)?
I was practicing stack buffer exploitation on a well known application
I was able to bypass canaries, ASLR and nx bit with techniques easily found on the internet
However it has fortify-source enabled ...
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Is this paper on stack canaries outdated?
According to this paper on defeating stackguard, it seems canaries are placed lower in the stack (higher address) than EBP, allowing the attacker to overwrite EBP without being noticed. But when I ...
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618
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What is the maximum payload injection size
I have been conducting some minor research into the various forms of exploitation, such as buffer overflows and similar.
Most tutorials seem to focus on executing shellcode, that is code which ...
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Question on stack overflow
I am preparing for an exam in Computer Security and doing a past-exam without soluions, so I wanted to check if my reasoning holds on a question about stack overflow. Below is the C code in question. ...
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Can you perform a buffer overflow and a format string attack at the same time?
So I hope I'm phrasing this right. I'm trying to exploit a piece of c code which you can see below.
#include <stdlib.h>
#include <unistd.h>
#include <stdio.h>
#include <string.h&...
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1
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Why does my compiler warn me about gets but not about scanf?
If I compile a code with gets, the compiler outputs a warning saying that the function shouldn't be used:
<source>:5:13: warning: 'char* gets(char*)' is deprecated [-Wdeprecated-declarations]
...
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1
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279
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Having trouble with learning Buffer Overflows
So I have this program in C that I'm trying to exploit which has a vulnerability in a function, namely it's using gets. I'm trying to overflow and change the return address so the program returns one ...
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Is it possible to use ROP to call legitimate functions even if the stack is not executable?
I read about the hardware protection that blocks the CPU from jumping to stack address. But hacker may still edit the return address to an address in code memory that shouldn't run at that moment.
For ...
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Where does the SP (Stack Pointer) point to when the buffer is overflown?
Let's consider a stack that grows downwards and a function that has a local variable for a buffer that takes 100 bytes of memory.
So, reading from top to bottom, it would be a 4-byte long return ...
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336
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Problem with return 2 libc in 64 bit arch
I want to perform return to libc in 64 bit architecture using execve. I found a gadget with /bin/sh in it (the /bin/sh offset is 18a143):
cbcd8: 00 00
cbcda: 4c 89 ea ...
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1
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474
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BufferOverFlow - How come ESP points to the end of the payload
I just don't understand how ESP points to the shellcode
let's say we've sent this string
string = 100 * 'A' + 'BBBB' + 'CCCC'
I have filled the stack with 'AAAA..' and overwritten the EIP value and ...
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1
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193
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Automatically insertion of 00 in EIP in Stack Overflow 64bit
I am trying to overflow a stack in C sample code to execute uncalled function in code.
The problem is when i overflow stack by entering a(24 times), $EIP is 0x555555550061. I want it to be ...
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1
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420
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Return address incorrect (buffer overflow)
I'm trying to exploit the following code with a buffer overflow to get a shell:
int main()
{
char str[64]
gets(str);
return(0);
}
The platform is Ubuntu 64 bit, arch i686.
The program is ...
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1
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997
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Buffer overflow Mona modules all show Rebase SafeSEH ASLR True
Almost every beginners (noob friendly) tutorial written for Stack based buffer overflow explains when using mona module to locate a safe reliable memory address for our EIP to JMP to our shellcode ...
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Exploit education stack-five: trouble opening shell
Im trying the phoenix vm, challenge stack-five on exploit.education (http://exploit.education/phoenix/stack-five/).
I run onto a problem while exploiting a stack overflow. The challenge is run execve('...
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Cannot execute shellcode using buffer overflow
As a home exercise I'm trying to achieve buffer overflow attack by running a simple char array program that stores the input argument in the program stack and then overflowing that stack with long ...
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EIP pointing to shellcode but shellcode is not executing?
I have successfully overwritten the EIP register (pointing to my shellcode) but the shellcode is not executing. I compiled with the command
gcc -g -fno-stack-protector -z execstack -no-pie vuln.c -o ...
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3
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ret2libc - why need 4 bytes of garbage
So I started to learn reverse engineering, and I came across the ret2libc exploit.
I tried to understand how it works and I got a bit confused.
They say that when you return to the address of system ...
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3
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Does a buffer overflow vulnerability always mean a code execution vulnerability?
Since buffer overflows always let an evil hacker write outside the buffer and overwrite the return pointer to a shellcode the evil hacker can place, does it mean that successful exploitation of a ...
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Why Does Only 1 Of These 2 Almost-identical Payloads Give Me A Shell?
I wrote a vulnerable test program to practice buffer overflows; however, I was having trouble getting it to work. Finally, after slightly modifying the return address, I was able to gain a shell, but ...
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ret2libc calling function arguments order
While I was studying ret2libc, I saw that tutorials use:
call_to_function + ret addr + arguments
For example I understand that if I want to execute system function from libc I can use the following ...
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How are stack canaries padded by unmapped pages?
I was reading the wikipedia article on this subject and it states that when a program starts, the canary is calculated at random, stored in a local variable(which I presume was introduced by the ...
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2
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In Return-Oriented Programming how can the machine execute unaligned instructions?
I am reading "The Geometry of Innocent Flesh on the Bone: Return-into-libc without Function Calls (on the x86)".
The author claims that x86 code is like English written without punctuation or spaces, ...
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Cannot exploit stack-based buffer overflow with ASLR-disabled, since RSP differs heavily between executions?
I have made a little toy program, compiled with ALSR disabled, that I want to exploit using stack-based buffer overflow:
// gcc stackexec0x1.c -Wl,-z,execstack -no-pie -fno-stack-protector -o ...
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What is Return-Oriented Programming? [closed]
With return-oriented programming, when we fill a buffer with the stack contents (arguments and return addresses) for the function calls we plan on "injecting," how do we actually change the stack ...
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Need help in exploiting an overflow on Linux [closed]
There is a 32-bit linux application. It's possible to overwrite EIP easily. I will call this process: "send a string".
It's also possible to send about 10000 custom bytes to heap (it's possible to ...
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Overflowing the buffer yet not jumping to address
I am a beginner at buffer overflows been studying this subject from a few days and i found this exercise (code from: here)
I think understand the basic concept i write more than 64 bytes characters ...
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Smashing stack in x86_64
Exploiting functions like strcpy() relies on the fact that the payload string must not contain zero bytes that would terminate the copy function. If the payload contains x86_64 addresses (e.g. in ...
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How does gcc compiler guard stack for stack overflow?
When we compile c program with gcc, we have to inlude "-z execstack" option to enable stack overflow attack.
The question I want to ask is how does gcc implement this .
Without this option, how does ...
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Why do we need to remove null bytes from shell code?
I'm studying the basics of making shell codes. I have a question about it.
In my textbook, the author stores his shell code in an environment variable, and injects the address of it using strcpy() ...
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2
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Buffer Overflow Stack Attack Exercise Help
So I am trying to complete a buffer overflow exercise. The code I am trying to exploit is below. What I want to be able to do is to insert my own print statement through the overflow attack. What I ...
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How do I bypass a return address overwrite not doing anything?
This is main:
(gdb) disass main
Dump of assembler code for function main:
0x000000000040057c <+0>: push rbp
0x000000000040057d <+1>: mov rbp,rsp
0x0000000000400580 <+4&...
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2
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C - Simple Buffer Overflow Exploitation, how is the EIP overwritten in different type calling functions?
General Background:
I have written an echo server trying to implement an example of BoF in C that utilizes a strcpy() function call like such:
// .... including the corresponding libraries depending ...
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Understanding a crash
Say you're fuzzing a Windows x32 application for a file format bug and, say, you found a pattern that causes the application to crash.
My normal steps are:
load application into a debugger
...
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Why do registers get overwritten upon overflow?
I know that upon a overflow, the stack gets partially overwritten, but I do not understand why registers such as EIP or RIP get changed in this process.
How come some registers are modified by such ...
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Stackpivoting techniques
I'm practicing exploit development and one of the scenario I am haing most difficulties with is stack pivoting besides the "ADD ESP, XXX" or something like that.
The question is, during the writing ...
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Bufferoverflow - jmp esp. Do I need nops sled? Does call esp also work?
I'm learning about stack buffer overflow and I'd appreciate help.
I'm exploiting simple web server containing this log function. Argument s1 is the input that I supply via HTTP. Server is running on ...
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Software overflow exploitation lab
Working through a binary exploitation course posted by RPI a few years ago. Currently on the ASLR lab and having some trouble with it (although not with the parts related to ASLR). I can't figure out ...
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Some vulnerable projects in C or C++ for a lecture? [closed]
I'm looking for some real projects which have stack overflow vulnerabilities. The important thing is, I am going to teach finding the vulnerabilities and the way of fixing them by these examples. So, ...
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Hard-wired vs relative addresses in shellcode
This question is primarily in the context of arbitrary command execution in a buffer (e.g. stack) overflow.
I read somewhere recently that hard-wired (absolute) addresses are not good for shellcode e....
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Using instruction set architecture (ISA) to stop stack overflows
I have been learning about using stack overflows to get arbitrary code execution, one of the tricks used is overwriting the return address to make control flow go the way you want it. Assuming our ...
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How is the stack protection enforced in a binary?
On a linux box with an Intel CPU, lets say I compiled by binary with -fstack-protect-all.
How is this encoded into the binary? (Can I see this info using readelf? ). Is it encoded into every page/...
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Exploit does not work outside GDB
I already tried various solutions provided to other "exploit doesn't work outside gdb" questions (r.sh, invoke.sh, removing environment variables) and at this point I legit have no idea why the ...
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