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](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.
This language is easily detectable by its huge use of plus signs, braces, and arrows. There are plenty of online interpreters, like this one: [https://copy.sh/brainfuck/](https://copy.sh/brainfuck/) Some example code:
An esoteric language that looks a lot like Base85... but isn't. Often has references to "Inferno" or "Hell" or "Dante." Online interpreters like so: [http://www.malbolge.doleczek.pl/](http://www.malbolge.doleczek.pl/) Example code:
Don't ever forget about [`steghide`][steghide]! This tool can use a password list like `rockyou.txt` with steghide. SOME IMAGES CAN HAVE MULTIPLE FILED ENCODED WITH MULTIPLE PASSWORDS.
A [Java][Java] [`.JAR`][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](http://0xahmed.ninja/nullcon-hackim18-ctf-writeups/) challenge from [HackIM 2018](https://ctftime.org/event/566)
* [`Stegsolve.jar`][Stegsolve.jar]
A [Java][Java] [`.JAR`][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.
Another command-line tool to use against JPEG images. [https://github.com/lukechampine/jsteg](https://github.com/lukechampine/jsteg) Handy for Hackerrank Codefest CTF 2018.
A GUI tool for JPG steganography. [https://sourceforge.net/projects/jstego/](https://sourceforge.net/projects/jstego/) It is a [Java][Java] [JAR] file similar to stegsolve.jar
Always test for this if you are seeing two distinct values... _it may not always be binary!_ Online decoders like so: [https://morsecode.scphillips.com/translator.html](https://morsecode.scphillips.com/translator.html)
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`][snow] or an esoteric programming language interpreter: [https://tio.run/#whitespace](https://tio.run/#whitespace)
Some classic challenges use an audio file to hide a flag or other sensitive stuff. SONIC visualizer easily shows you [spectrogram](https://en.wikipedia.org/wiki/Spectrogram). __If it sounds like there is random bleeps and bloops in the sound, try this tactic!__
Audio frequencies common to a phone button, DTMF: [https://en.wikipedia.org/wiki/Dual-tone_multi-frequency_signaling](https://en.wikipedia.org/wiki/Dual-tone_multi-frequency_signaling).
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`][zbarimg]
A command-line tool to quickly scan multiple forms of barcodes, [QR codes] included. Installed like so on a typical [Ubuntu] image:
I have seen some challenges use just the end of `.` or `?` or `!` to represent the [Ook](http://esolangs.org/wiki/ook!) esoteric programming language. Don't forget that is a thing!
[https://www.dcode.fr/keyboard-shift-cipher](https://www.dcode.fr/keyboard-shift-cipher) If you see any thing that has the shape of a sentence but it looks like nonsense letters, and notes some shift left or right, it may be a keyboard shift...
* Bit Shift
Sometimes the letters may be shifted by a stated hint, like a binary bit shift ( x >> 1 ) or ( x <<1).
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):
The most classic shift cipher. Tons of online tools like this: [https://www.dcode.fr/caesar-cipher](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.
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](http://rumkin.com/tools/cipher/atbash.php)), and you can build it with [Python].
[http://www.mygeocachingprofile.com/codebreaker.vigenerecipher.aspx](http://www.mygeocachingprofile.com/codebreaker.vigenerecipher.aspx), [https://www.guballa.de/vigenere-solver](https://www.guballa.de/vigenere-solver) and personal Python code here: [https://pastebin.com/2Vr29g6J](https://pastebin.com/2Vr29g6J)
[https://github.com/tna0y/Python-random-module-cracker](https://github.com/tna0y/Python-random-module-cracker)... helps attack the Mersenne Twister used in Python's random module.
Variables typically given: `n`, `c`, `e`. _ALWAYS_ try and give to [http://factordb.com](http://factordb.com). If `p` and `q` are able to be determined, use some RSA decryptor; handmade code available here: [https://pastebin.com/ERAMhJ1v](https://pastebin.com/ERAMhJ1v)
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:
The telltale sign for this kind of challenge is an enormously large `e` value. Typically `e` is either 65537 (0x10001) or `3` (like for a Chinese Remainder Theorem challenge). Some stolen code available here: [https://pastebin.com/VKjYsDqD](https://pastebin.com/VKjYsDqD)
These challenges can be spotted when given mutiple `c` cipher texts and multiple `n` moduli. `e` must be the same number of given `c` and `n` pairs. Some handmade code here: [https://pastebin.com/qypwc6wH](https://pastebin.com/qypwc6wH)
The go-to tool for examining [`.pcap`][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/](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
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](https://github.com/spaze/hashes), but below are the most common breaks.
A command-line tool to decode [`bcompiler`][bcompiler] compiled [PHP] code.
* [`php://filter` for Local File Inclusion](https://www.idontplaydarts.com/2011/02/using-php-filter-for-local-file-inclusion/)
A bug in [PHP] where if GET HTTP variables in the URL are controlling the navigation of the web page, perhaps the source code is `include`-ing other files to be served to the user. This can be manipulated by using [PHP filters](http://php.net/manual/en/filters.php) to potentially retrieve source code. Example like so:
A [PHP] stream that can be taken advantage of if used and evaluated as an `include` resource or evaluated. Can be used for RCE: check out this writeup: [https://ctftime.org/writeup/8868](https://ctftime.org/writeup/8868) ... TL;DR:
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.
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](https://en.wikipedia.org/wiki/List_of_file_signatures).
* [`hexed.it`][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`][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:
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.
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/](http://www.robotstxt.org/)
A web browser plug-in that offers an easy interface to modifying [cookies]. ___THIS IS OFTEN OVERLOOKED, WITHOUT CHANGING THE VALUE OF THE COOKIES... BE SURE TO FUZZ EVERYTHING, INCLUDING COOKIE VALUES!___
Some times you may be able to dig up an old version of a webpage (or some PHP source code!) by adding the usual backup suffixes. A good thing to check!
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.
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`][wget].
* [`GitDumper.sh`][GitDumper.sh]
A command-line tool that will automatically scrape and download a [git] repository hosted online with a given URL.
[XSS Filter Evasion Cheat Sheet](https://www.owasp.org/index.php/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:
If you need to script or automate against a page that uses the I'm Under Attack Mode from CloudFlare, or DDOS protection, you can do it like this with linked Python module.
These are handy for some injections and setting up some Blind SQL if you need to. Syntax is like `SELECT ( IF ( 1=1, "Condition successful!", "Condition errored!" ) )`
When debugging AutoIT programs, you may get a notification: "This is a compiled AutoIT script". Here is a good thing to use to decode them: [https://www.autoitscript.com/site/autoit/downloads/](https://www.autoitscript.com/site/autoit/downloads/)
A C binary vulnerability, where `printf` is used with user-supplied input without any arguments. Hand-made code to exploit and overwrite functions: [https://pastebin.com/0r4WGn3D](https://pastebin.com/0r4WGn3D) and a video walkthrough explaining: [https://www.youtube.com/watch?v=t1LH9D5cuK4](https://www.youtube.com/watch?v=t1LH9D5cuK4)
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.
Some CTFs have me solve wordsearchs as part of a challenge (TJCTF 2018). This code is super helpful: [https://github.com/robbiebarrat/word-search](https://github.com/robbiebarrat/word-search)
A sliding puzzle that consists of a 4x4 grid with numbered square tiles, with one missing, set in a random order. It was involved in SharifCTF to determine if a group of these puzzles was solvable: [https://theromanxpl0it.github.io/ctf_sharifctf18/fifteenpuzzle/](https://theromanxpl0it.github.io/ctf_sharifctf18/fifteenpuzzle/)
