Buffer Overflow

Intro Classic ROP challange. File Info $ file vuln vuln: ELF 32-bit LSB executable, Intel 80386, version 1 (GNU/Linux), statically linked, BuildID[sha1]=3aa2bb6a5bf44d90a355da83fa909bbf5d9d90ce, for GNU/Linux 3.2.0, not stripped Statically linked binary. Source code #include <stdio.h>#include <stdlib.h>#include <string.h>#include <unistd.h>#include <sys/types.h> #define BUFSIZE 16 void vuln() { char buf[16]; printf("How strong is your ROP-fu? Snatch the shell from my hand, grasshopper!\n"); return gets(buf); } int main(int argc, char **argv){ setvbuf(stdout, NULL, _IONBF, 0); // Set the gid to the effective gid // this prevents /bin/sh from dropping the privileges gid_t gid = getegid(); setresgid(gid, gid, gid); vuln(); } Running Executable $ ....

Intro Do you think you can bypass the protection and get the flag? It looks like Dr. Oswal added a stack canary to this program to protect against buffer overflows. We are given compiled binary, its source and the host and port where challenge is hosted. saturn.picoctf.net 63181 #include <stdio.h>#include <stdlib.h>#include <string.h>#include <unistd.h>#include <sys/types.h>#include <wchar.h>#include <locale.h> #define BUFSIZE 64 #define FLAGSIZE 64 #define CANARY_SIZE 4 void win() { char buf[FLAGSIZE]; FILE *f = fopen("flag....

Intro Overflow the buffer and change the return address to the flag function. We are given the compiled binary, the application source code along with the hostname and port to connect to. #include <stdio.h>#include <stdlib.h>#include <string.h>#include <unistd.h>#include <sys/types.h> #define BUFFSIZE 64 #define FLAGSIZE 64 void flag() { char buf[FLAGSIZE]; FILE *f = fopen("flag.txt","r"); if (f == NULL) { printf("%s %s", "Please create 'flag.txt' in this directory with your", "own debugging flag....

Investigation When connecting to challenge server on the given hostname and port, it is an echo server which echoes back the user input in alternate case. $ nc mercury.picoctf.net 37289 WeLcOmE To mY EcHo sErVeR! test TeSt ^C We are given following files: $ ls -lR .: total 20 drwxr-xr-x 2 kali kali 4096 Nov 9 00:32 libc -rw-r--r-- 1 kali kali 95 Mar 15 2021 Makefile -rw-r--r-- 1 kali kali 8560 Mar 15 2021 vuln ....

Introduction This is walkthrough for Ropasaurusrex challenge from PlaidCTF 2013. Repo for binary: https://github.com/adamdoupe/ctf-training/tree/master/ropasaurusrex Docker: docker run -p 127.0.0.1:31337:31337 -it adamdoupe/ropasaurusrex Crashing the Program: Enable Core Dumps: $ ulimit -c unlimited Sending large string: $ python -c "print ('A'*300)" | ./ropasaurusrex zsh: done python -c "print ('A'*300)" | zsh: segmentation fault (core dumped) ./ropasaurusrex Inspecting core dump: $ gdb ./ropasaurusrex -q core Reading symbols from ./ropasaurusrex... (No debugging symbols found in ....

Introduction This is walkthrough for level2 of ROP Primer from vulnhub. Running the Application level0@rop:/home/level2$ ls -l total 588 -rw-r----- 1 root root 27 Jan 20 2015 flag -rwsr-xr-x 1 root root 595252 Jan 20 2015 level2 level0@rop:/home/level2$ level0@rop:/home/level2$ ./level2 level0@rop:/home/level2$ ./level2 AAAAAAAAAA [+] ROP tutorial level2 [+] Bet you can't ROP me this time around, AAAAAAAAAA! level0@rop:/home/level2$ Application accepts command line arguments. Crashing the Application Enable core dump - ulimit -c unlimited...

Introduction This is walkthrough for level1 of ROP Primer from vulnhub. Exploit Development Running the Application level0@rop:/home/level1$ ./level1 [!] error bind()ing! [+] retrying bind() [!] error bind()ing! ^C This means that a service is already listening on the port. Inspecting netstat to look for listening ports. level0@rop:~$ su root Password: root@rop:/home/level0# netstat -antp Active Internet connections (servers and established) Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name tcp 0 0 0....

Introduction This is walkthrough for level0 of ROP Primer from vulnhub. ROP Primer This VM is meant as a small introduction to 32-bit return-oriented-programming on Linux. It contains three vulnerable binaries, that must be exploited using ROP. The machine is built and tested in VirtualBox 4.3.20. It’s an Ubuntu 32 bit VM, with ASLR disabled. Useful tools like gdb-peda are installed. A description of the levels, including instructions, can be found on the webserver....

Challenge Description Can you point to the stars? Make the pointer point to the flag! Connect to the challenge at exploitation.ps.ctf.ae:5454 ...

Protostar introduces the following in a friendly way: Network programming Byte order Handling sockets Stack overflows Format strings Heap overflows ...