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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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Simple Buffer Overflow (Function Call) Problem

I'm trying to develop a simple buffer overflow CTF challenge inspired by the "Csaw 2016 Quals Warmup" challenge, here. I've managed to replicate the source code: #include <stdio.h> #...
FreezeLuiz's user avatar
0 votes
0 answers
118 views

Hydra says different passwords with are correct each run, but only one works

I am doing CTF 'Skynet' from THM and came across this problem. Enumerating SMB, I gathered credentials 'milesdyson' and a list of passwords 'log1.txt'. I figured that I could try to brute force ...
Juan Vega Seco's user avatar
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0 answers
239 views

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 ...
TKC's user avatar
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1 answer
238 views

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 ...
Black Hemera's user avatar
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0 answers
94 views

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 ...
Nsion's user avatar
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0 answers
131 views

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: ...
Andrey's user avatar
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1 vote
1 answer
425 views

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 ...
user294797's user avatar
3 votes
0 answers
293 views

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: ...
user avatar
33 votes
1 answer
5k views

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 ...
user5623335's user avatar
0 votes
1 answer
774 views

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 ...
user5623335's user avatar
2 votes
1 answer
186 views

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 ...
Haaziq Jamal's user avatar
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1 answer
316 views

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/...
justsobad's user avatar
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0 answers
399 views

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 ...
justsobad's user avatar
1 vote
2 answers
1k views

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/...
questioner's user avatar
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221 views

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+...
it dev's user avatar
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1 answer
257 views

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?&apos;-alert(1)-&apos; Which is input into the following section of ...
questioner's user avatar
0 votes
0 answers
264 views

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 ...
Shinomoto Asakura's user avatar
1 vote
1 answer
800 views

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 "&...
questioner's user avatar
0 votes
0 answers
571 views

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 ...
questioner's user avatar
1 vote
1 answer
1k views

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 ...
Jarthaul's user avatar
0 votes
0 answers
369 views

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 ...
UkaChan's user avatar
1 vote
0 answers
405 views

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. ...
Desperados's user avatar
1 vote
1 answer
5k views

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....
J.erome's user avatar
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0 votes
0 answers
137 views

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 ...
Anass Naqqad's user avatar
0 votes
1 answer
862 views

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. ...
questioner's user avatar
0 votes
1 answer
625 views

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 ...
nickelpro's user avatar
  • 111
0 votes
0 answers
836 views

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/...
saroglou's user avatar
1 vote
0 answers
221 views

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 ...
guesst's user avatar
  • 11
1 vote
2 answers
1k views

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....
AnzioElane's user avatar
0 votes
1 answer
481 views

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 ...
lexus's user avatar
  • 1
0 votes
2 answers
3k views

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 ...
Ryuzaki 's user avatar
1 vote
0 answers
378 views

CyberChef Challenge #21 [closed]

The challenge data is: ...
CtfLover's user avatar
2 votes
1 answer
2k views

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 ...
retsek680's user avatar
0 votes
1 answer
715 views

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 ...
user245607's user avatar
0 votes
0 answers
417 views

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 ...
Error's user avatar
  • 103
0 votes
0 answers
161 views

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) ...
kuma's user avatar
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2 votes
0 answers
1k views

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 ...
XRBtoTheMOON's user avatar
0 votes
0 answers
381 views

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 ...
Hacker54's user avatar
2 votes
1 answer
2k views

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....
Z. Alessandro's user avatar
0 votes
0 answers
216 views

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 ...
Plonker's user avatar
4 votes
3 answers
1k views

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 ...
Nerotix's user avatar
  • 191
2 votes
1 answer
10k views

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:...
pee2pee's user avatar
  • 297
0 votes
1 answer
1k views

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 ...
Plonker's user avatar
6 votes
4 answers
3k views

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 ...
user avatar
0 votes
0 answers
225 views

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 ...
Shubham Kumar's user avatar
0 votes
1 answer
2k views

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 ...
Wolf's user avatar
  • 367
0 votes
0 answers
3k views

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 ...
MrPython's user avatar
1 vote
0 answers
975 views

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 ...
yewheng95's user avatar
2 votes
0 answers
613 views

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 ...
0xFFFFFF's user avatar
1 vote
0 answers
227 views

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. ...
Jonathan's user avatar