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This repository aims to hold suggestions (and hopefully/eventually code) for CTF challenges. The "project" is nicknamed Katana.
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John Hammond aca707c9de Added note for PNGcheck 2018-02-25 15:02:53 -05:00
README.md Added note for PNGcheck 2018-02-25 15:02:53 -05:00

README.md

CTF-Katana

John Hammond | February 1st, 2018

This repository, at the time of writing, will just host a listing of tools and commands that may help with CTF challenges. I hope to keep it as a "live document," and ideally it will not die out like the old "tools" page I had made (https://github.com/USCGA/tools).

Hopefully, at some point I will develop software that will run through a lot of the low-hanging fruit and simple command-line tools, generate a report and have all the output in one place.

Steganography

  • openstego

    A Java .JAR tool, that can extract data from an image. A good tool to use on guessing challenges, when you don't have any other leads. We found this tool after the Misc50 challenge from HackIM 2018

  • Stegsolve.jar

    A Java .JAR tool, that will open an image and let you as the user arrow through different renditions of the image (viewing color channels, inverted colors, and more). The tool is surprisingly useful.

  • steghide

    A command-line tool typically used alongside a password or key, that could be uncovered some other way when solving a challenge.

  • [zsteg][zsteg]

    Command-line tool for use against Least Significant Bit steganography... unfortunately only works against PNG and BMP images.

  • Morse Code

    Always test for this if you are seeing two distinct values... it may not always be binary!

  • Whitespace

    Tabs and spaces could be representing 1's and 0's and treating them as a binary message... or, they could be whitespace done with snow or an esoteric programming language interpreter: http://ws2js.luilak.net/interpreter.html

  • snow

    A command-line tool for whitespace steganography (see above).

  • SONIC Visualizer (audio spectrum)

    Some classic challenges use an audio file to hide a flag or other sensitive stuff. SONIC visualizer easily shows you spectrogram. If it sounds like there is random bleeps and bloops in the sound, try this tactic!

  • Detect DTMF Tones

    Audio frequencies common to a phone button, DTMF: https://en.wikipedia.org/wiki/Dual-tone_multi-frequency_signaling.

  • hipshot

    A Python module to compress a video into a single standalone image, simulating a long-exposure photograph. Was used to steal a QR code visible in a video, displayed through "Star Wars" style text motion.

  • QR code

    A small square "barcode" image that holds data.

  • zbarimg

    A command-line tool to quickly scan multiple forms of barcodes, QR codes included. Installed like so on a typical Ubuntu image:

sudo apt install zbar-tools

Cryptography

  • Reversed Text

    Sometimes a "ciphertext" is just as easy as reversed text. Don't forgot to check under this rock! You can reverse a string in Python like so:

"UOYMORFEDIHOTGNIYRTEBTHGIMFTCATAHTTERCESASISIHT"[::-1]

  • XOR

    ANY text could be XOR'd. Techniques for this are Trey's code, and XORing the data against the known flag format. Typically it is given in just hex, but once it is decoded into raw binary data, it gives it keeps it's hex form (as in \xde\xad\xbe\xef etc..) Note that you can do easy XOR locally with Python like so (you need pwntools installed):

    python >>> import pwn; pwn.xor("KEY", "RAW_BINARY_CIPHER")

  • Caesar Cipher

    The most classic shift cipher. Tons of online tools like this: https://www.dcode.fr/caesar-cipher or use caesar as a command-line tool (sudo apt install bsdgames) and you can supply a key for it. Here's a one liner to try all letter positions:

    cipher='jeoi{geiwev_gmtliv_ws_svmkmrep}' ; for i in {0..25}; do echo $cipher | caesar $i; done

    Be aware! Some challenges include punctuation in their shift! If this is the case, try to a shift within all 255 ASCII characters, not just 26 alphabetical letters!

  • caesar

    A command-line caesar cipher tool (noted above) found in the bsdgames package.

  • Atbash Cipher

    If you have some text that you have no idea what it is, try the Atbash cipher! It's a letter mapping, but the alphabet is reversed: like A maps to Z, B maps to Y and so on. There are tons of online tools to do this (http://rumkin.com/tools/cipher/atbash.php), and you can build it with Python.

  • Vigenere Cipher

    http://www.mygeocachingprofile.com/codebreaker.vigenerecipher.aspx, https://www.guballa.de/vigenere-solver

  • Beaufourt Cipher

    https://www.dcode.fr/beaufort-cipher

  • Transposition Cipher

  • RSA: Classic RSA

    Variables typically given: n, c, e. ALWAYS try and give to http://factordb.com

  • RSA: Multi-prime RSA

  • RSA: e is 3 (or small)

    If e is 3, you can try the cubed-root attack. If you the cubed root of c, and if that is smaller than the cubed root of n, then your plaintext message m is just the cubed root of c! Here is Python code to take the cubed root:

def root3rd(x):
    y, y1 = None, 2
    while y!=y1:
        y = y1
        y3 = y**3
        d = (2*y3+x)
        y1 = (y*(y3+2*x)+d//2)//d
    return y

Networking

  • Wireshark

    The go-to tool for examining .pcap files.

  • Network Miner

    Seriously cool tool that will try and scrape out images, files, credentials and other goods from PCAP and PCAPNG files.

  • PCAPNG

    Not all tools like the PCAPNG file format... so you can convert them with an online tool http://pcapng.com/ or from the command-line with the editcap command that comes with installing Wireshark:

editcap old_file.pcapng new_file.pcap

  • [tcpflow][tcpflow]

    A command-line tool for reorganizing packets in a PCAP file and getting files out of them. Typically it gives no output, but it creates the files in your current directory!

tcpflow -r my_file.pcap
ls -1t | head -5 # see the last 5 recently modified files

  • PcapXray

    A GUI tool to visualize network traffic.

PHP

  • Magic Hashes

    A common vulnerability in PHP that fakes hash "collisions..." where the == operator falls short in PHP type comparison, thinking everything that follows 0e is considered scientific notation (and therefore 0). More valuable info can be found here: https://github.com/spaze/hashes, but below are the most common breaks.

Plaintext MD5 Hash
240610708 0e462097431906509019562988736854
QLTHNDT 0e405967825401955372549139051580
QNKCDZO 0e830400451993494058024219903391
PJNPDWY 0e291529052894702774557631701704
NWWKITQ 0e763082070976038347657360817689
NOOPCJF 0e818888003657176127862245791911
MMHUWUV 0e701732711630150438129209816536
MAUXXQC 0e478478466848439040434801845361
IHKFRNS 0e256160682445802696926137988570
GZECLQZ 0e537612333747236407713628225676
GGHMVOE 0e362766013028313274586933780773
GEGHBXL 0e248776895502908863709684713578
EEIZDOI 0e782601363539291779881938479162
DYAXWCA 0e424759758842488633464374063001
DQWRASX 0e742373665639232907775599582643
BRTKUJZ 00e57640477961333848717747276704
ABJIHVY 0e755264355178451322893275696586
aaaXXAYW 0e540853622400160407992788832284
aabg7XSs 0e087386482136013740957780965295
aabC9RqS 0e041022518165728065344349536299
Plaintext SHA1 Hash
aaroZmOk 0e66507019969427134894567494305185566735
aaK1STfY 0e76658526655756207688271159624026011393
aaO8zKZF 0e89257456677279068558073954252716165668
aa3OFF9m 0e36977786278517984959260394024281014729 
http://xqi.cc/index.php?m=php://filter/convert.base64-encode/resource=index

PDF Files

  • pdfinfo

    A command-line tool to get a basic synopsis of what the PDF file is.

  • pdfcrack

    A comand-line tool to recover a password from a PDF file. Supports dictionary wordlists and bruteforce.

  • pdfimages

    A command-line tool, the first thing to reach for when given a PDF file. It extracts the images stored in a PDF file, but it needs the name of an output directory (that it will create for) to place the found images.

  • pdfdetach

    A command-line tool to extract files out of a PDF.

Forensics

  • Magic Numbers

    The starting values that identify a file format. These are often crucial for programs to properly read a certain file type, so they must be correct. If some files are acting strangely, try verifying their magic number with a trusted list of file signatures.

  • hexed.it

    An online tool that allows you to modify the hexadecimal and binary values of an uploaded file. This is a good tool for correcting files with a corrupt magic number

  • dumpzilla

    A Python script to examine a .mozilla configuration file, to examine downloads, bookmarks, history or bookmarks and registered passwords. Usage may be as such:

python dumpzilla.py .mozilla/firefox/c3a958fk.default/ --Downloads --History --Bookmarks --Passwords

  • foremost

    A command-line tool to carve files out of another file. Usage is foremost [filename] and it will create an output directory.

sudo apt install foremost

  • binwalk

    A command-line tool to carve files out of another file. Usage to extract is binwalk -e [filename] and it will create a _[filename]_extracted directory.

sudo apt install binwalk

  • hachoir-subfile

    A command-line tool to carve out files of another file. Very similar to the other tools like binwalk and foremost, but always try everything!

  • TestDisk

    A command-line tool, used to recover deleted files from a file system image. Handy to use if given a .dd and .img file etc.

PNG File Forensics

  • pngcheck

    A command-line tool for "checking" a PNG image file. Especially good for verifying checksums.

Web

  • robots.txt

    This file tries to hide webpages from web crawlers, like Google or Bing or Yahoo. A lot of sites try and use this mask sensitive files or folders, so it should always be some where you check during a CTF. http://www.robotstxt.org/

  • Edit This Cookie

    A web browser plug-in that offers an easy interface to modifying cookies.

  • /admin/

    This directory is often found by directory scanning bruteforce tools, so I recommend just checking the directory on your own, as part of your own "low-hanging fruits" check.

  • /.git/

    A classic CTF challenge is to leave a git repository live and available on a website. You can see this with nmap -A (or whatever specific script catches it) and just by trying to view that specific folder, /.git/. A good command-line tool for this is [GitDumper.sh][https://github.com/internetwache/GitTools], or just simply using wget.

  • GitDumper.sh

    A command-line tool that will automatically scrape and download a git repository hosted online with a given URL.

  • XSS/Cross-site scripting

    XSS Filter Evasion Cheat Sheet. Cross-site scripting, vulnerability where the user can control rendered HTML and ideally inject JavaScript code that could drive a browser to any other website or make any malicious network calls. Example test payload is as follows:

<IMG SRC=/ onerror="alert(String.fromCharCode(88,83,83))"></img>

Windows Executables

Python Reversing

  • [Easy Python Decompiler]

    A small .exe GUI application that will "decompile" Python bytecode, often seen in .pyc extension. The tool runs reliably on Linux with Wine.

Binary/pwn

  • printf vulnerability

  • formatStringExploiter

    A good Python module to streamline exploiting a format string vulnerability.

  • 64-bit Buffer Overflow

    64-bit buffer overflow challenges are often difficult because the null bytes get in the way of memory addresses (for the function you want to jump to, that you can usually find with readelf -s). But, check if whether or not the function address you need starts with the same hex values already on the stack (in rsp). Maybe you only have to write two or three bytes after the overflow, rather than the whole function address.

Java Reversing

Android APK Reversing

VisualBasicScript Reversing

Miscellaneous

sudo apt install -y caca-utils