Questions tagged [ctf]
Capture the Flag (CTF) is a form of hacking competition. Use for questions about the design and operation of such contests. Do not use for questions asking for help with winning contests.
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Encoding shellcode to hide in filename / directory
Working on a CTF challenge and the coordinators hint suggests that one of the vectors to inject shellcode is via pathing. Looking at debugging prints does show the cwd and filename are passed onto the ...
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Exporting shellcode to environment variable doesn't work as expected
(This is a question regarding a challenge in a wargame on overthewire.org called Narnia similar to Shellcode does not execute as the owner )
When exporting shellcode to EGG environment variable
export ...
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Trying to ret2text on 64bit program issues, can't jump to shell
Here is the elf summary of the program:
Arch: amd64-64-little
RELRO: Partial RELRO
Stack: No canary found
NX: NX enabled
PIE: No PIE (0x400000)
This is the ...
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0
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73
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What type of token is this?
I started noticing this kind of token in a lot of CTF tasks from different authors:
eyJlbWFpbCI6ImVtYWlsQG1haWxib3guZG9tYWluIiwiaWQiOjN9.ZLNCAQ.MxwKVKj_dramWyfT5XxT6g9U3xk
The structure is as follows:
...
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1
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1
answer
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AES ECB cookie bypass
I am currently participating in a CTF Challenge and have reached a stage where I discovered a "log_admin" page. This page generates a cookie that is encrypted using AES 128 ECB. I obtained ...
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202
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PHP CTF: Vulnerabilities in PHP before 2007?
I came across a CTF that i'm trying to solve, the goal is fairly simple: Bypass the authentication form and access the admin-restricted area. You can find the code snippet below.
Things to consider:
...
user291842
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Anyone can help with this buffer ovewrflow (ctf) question?
I am new to bufferoverflow and was told that this code can lead to a buffer overflow.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <openssl/sha.h>
#...
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33
votes
1
answer
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Crashing the sha1() function in PHP?
I am working on the following war game from Defend The Web, which requires me to do a source code review to login as the user memtash. The code is on GitLab here.
Here is my methodology:
Reset the ...
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1
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How long would this take to bruteforce?
I am working on the following war game from Defend The Web, which requires me to do a source code review to login as the user memtash. The code is on GitLab here.
Having inspected the source code ...
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2
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1
answer
126
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Void pointer and their attribute constructor
I am supposed to find the vulnerability in the code (as a part of a ctf) and I feel it's hidden either in the __attribute__((constructor)) or the pointer.
Here I can make out that it's a void pointer ...
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1
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64-bit ROP-based Buffer Overflow Attack
I am facing a CTF challenge in which I have to conduct an attack using a ROP chain on this program below:
#include <stdio.h>
#include <stdint.h>
#include <stdbool.h>
#include <sys/...
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227
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Flask URL Vulnerabilities
I am doing a CTF-style assignment and I am confronted with a web site created in Flask. This web site appears fairly unremarkable - it has 4 pages and no log-in/authentication functionality, nor does ...
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2
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Abusing Shell Feature for Privilege Escalation
This was covered in Linux PrivEsc, task 15, in this TryHackMe room.
I am having trouble understanding how this debugging mode is executing the commands in the PS4 variable, and why I must put /usr/...
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CTF Crypto question
The question in a CTF was this:
They used two hydrogen atoms (H2) from the SHA-256 molecule to encrypt
in some form of AES, and the result was as follows:
{mIT+GVt+p0YfgfOltHgqoetTS6h8bRSAScAGKrBE+...
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1
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How does this PortSwigger lab's XSS work?
I was doing the following PortSwigger Lab on cross site scripting (XSS).
The following payload works perfectly.
http://foo?'-alert(1)-'
Which is input into the following section of ...
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156
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I cannot make a reverse connection
I am playing with a Linux CTF server and came across a kind of reverse connection block. I uploaded a php webshell, gained control of www-data user and tried to make a reverse shell.
Possible a UFW ...
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1
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Why does this SQL injection have an equals symbol?
I was reading into the basics of SQL injection attacks on w3schools here.
In the second example, I was curious as to why the equal sign was used. I have quoted within the line below.
" or "&...
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411
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Metasploit module for NULL LDAP credentials
This article covers the solution for the LDAP challenges on a capture the flag.
I understand how the first example works, using the NULL value for the username and password to authenticate to the LDAP ...
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1
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Why when i nmap scan a machine i get the port 554 (RTSP) open?
I train on vulnerable boxes and during my recon phase, I use nmap to collect info on open ports.
I use the command nmap -sS [IP|URL] and no matter the machine, I get the result that port 554 - RTSP ...
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How to perform php post request attack with javascript sanitization?
The following code demonstrates the source code of this challenge and basically, I need to send a post request with arbitrary code to execute on the server. However, after multiple attempts Im unable ...
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C - Remote string format attack exploit - %n Does not seem to write anything on the stack
[As part of a ctf] I am trying to exploit a remote server through a tcp connection. The server is using snprintf() and provides user input as the formatting string. My goal is to dump the stack. ...
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Payload uploaded but error : "no session was created"
I'm doing a capture-the-flag challenge (similar to HackTheBox) and I can't figure it out despite looking at many workarounds how to solve my issue.
I did:
nmap --> got port 8080
firefox -> 10....
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Is it possible to create an NTFS partition having only the $MFT and $J tables ? Forensics CTF
This is the third part of a forensics challenge in a European CTF, and it is apparently the most difficult one because only three people flagged it among 700 participating.
I'm only here for guidance ...
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1
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408
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Some introductory reverse engineering help on finding a string
I understand the crackme I am researching is from 2007, however this was the point in my life when I initially became interested in reverse engineering and wish to complete it for nostalgia sake. ...
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1
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Segfault after reaching system
I'm doing a pretty bog-standard return-to-libc attack and I'm in a bit of a pickle.
I first got the entire attack working with my local version of libc, then I used the version of libc provided by the ...
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695
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Sudo -l systemctl bypass
I am trying to privilege escalate a vulnerable box and I've stuck with this output:
sudo -l
Matching Defaults entries for charlie on sewers:
env_reset, mail_badpass,
secure_path=/usr/local/...
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1
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0
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176
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ctf kernel challenges does not work [closed]
I'm trying to learn and solve some 'kernel related' ctf challenges (reading writups to try to run same environment and achieve root using one of the kernel-pwn technique...).
I'm using Ubuntu 20 VM ...
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2
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967
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Cracking diffie-hellman public key to obtain shared key
I'm given 2 prime numbers, g and n, as well 2 public keys, ga mod n and gb mod n, as part of a leaked Diffie hellman key exchange. I need to derive the shared key gab mod n using the given information....
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how to do a pentest to /assets/js/login.js [closed]
Hey guys this is my first question in this kind of platform. I made a pentest a vulnerable machine this is like a web page video content there are not much target vectors. In my attack a detect only ...
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2
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Is union based mysql injection able to read files outside database?
Can files outside database which are not part of any tables in database be read via union based SQL injection? For eg
http://xyz.com/fetch?id=3
Consider id parameter is used at server side by cursor ...
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Exploit apache2 service as member of www-data group
I am attempting to solve a CTF challenge where I am logged in as a member of the www-data group and the apache2 service is misconfigured and can be run as sudo without a password. What I am attempting ...
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613
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Steganography CTF question
I have recently participated in a CTF competition and failed in the following stage where the solution was never revealed.
After a really hard job I got access to a text file that contains a really ...
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358
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how to hack rbash --?
I'm solving CTF challenge, and have to escalate the privilege from user1 to user2, $HOME is read-only, so i can't change $HOME/.bashrc.
sudo -l shows (user2) NOPASSOWRD: /usr/rbash -- i can't write ...
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How to secure home environment when testing vulnerable VMs
I'd like to practice CTFs and cyber attacks on vulnerable VMs downloaded from seemingly reputable sources.
Which are the basic guidelines for securing the environment and avoid that malware (if any) ...
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How to fix TCP stream in Wireshark with spurious retransmission?
This was for a CTF (it ended yesterday, so I'm not cheating), but I've spent so many hours on it that I really just want to understand what I should have done.
Here is the PasteBin Hex Dump. I ...
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How can I use nohup command to get root access of the target machine?
I am playing ctf and I have gained access to the target machine but not as root. I can see nohup utility has root access on the machine and I used this command to get the root access but that did not ...
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1
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CTF setup for debugging heap exploits
I'm currently studying binary heap exploitation (mainly the glibc (ptmalloc2) implementation), for CTF competitions. The problem I'm facing is debugging challenges designed for a certain glibc version....
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URL Encoding leading to invalid flag
I'm currently completing an XSS challenge in a CTF. I successfully redirect the admin cookie to my request bin, but the flag is said to be invalid.
I am told this is because the flag string gets ...
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3
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Break out or bypass php functions
I'm currently doing an online CTF and I have LFI an can read the source code of the upload function. In there I see the following line:
shell_exec('rm -rf ' . directory/ . '*.p*');
So anytime I ...
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1
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XXE - possible to read directories?
I have come across XXE on a CTF a while ago and I can't get my head around where to go from where I am.
<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE foo [<!ENTITY xxe SYSTEM "php:...
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Using GET request to find html file
I'm doing a basic CTF at the moment. Using,
GET / HTTP/1.1
Host: subdomain.domain.com
I am getting the response:
<a href="/c98efc0d-5c3f-45ec-996a-2cb82d35ed26.html">follow this link to get ...
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4
answers
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What is hacking hackable virtual machines useful for? [closed]
I was watching an ethical hacking course where the tutor taught me to hack into different virtual machines and also machines from Hack The Box.
In the real world, how are these practices of hacking ...
user235696
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how to check offset for a program on remote server
I am solving pwn problems in CTF challenges. my exploits are working in the local system but it doesn't work on the remote server when connecting using Netcat. The issue was that even the function ...
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How to find vulnerable PHP parameter such as `.php?id=` as found in Kioptrix 3?
This is part of my preparation for OSCP.
According to https://www.vulnhub.com/entry/kioptrix-level-12-3,24/, Kioptrix 3 is vulnerable to SQL Injection.
However, I found that SQLi challenge on ...
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ZAP Error [java.net.ConnectException]: Connection refused (Connection refused)
I am trying to connect to http://challenge01.root-me.org/web-serveur/ch10/ in Firefox with FoxyProxy and OWASP ZAP and I got this error message
ZAP Error [java.net.ConnectException]: Connection ...
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Print contents of PHP file in CTF
I am working with a PHP vulnerability. Below is the code snippet. Basically, I need to print the contents of get_flag.php.
My train of thought is that the following could be the vulnerabilities in the ...
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Retrieving a flag from vim commands by reading through strace output [CTF]
So, to clarify, I'm currently working on a CTF challenge that consists of running an strace over on a bash script that is running vim commands using commands like vim -c ":!cat flag.txt" inside of a ...
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SQL Injection only with OR
I am doing a practise SQL injection in a search field and I don't understand the logic of what is happening.
The following behaviours is what I noticed:
Entering ' OR '1' = '1 shows all the results.
...
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How editing html and javascript of a website makes it vulnerable? [duplicate]
I was practicing web pentesting on this level of ctf2 and I was supposed to edit the HTML and the Javascript to get rid of the input validation and < > sanitization. I succeded after looking up ...
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