Youfu Zhang zhangyoufu

Tested against the WebKit git repo by entering the repo with 1 file dirty.

git diff --quiet --ignore-submodules HEAD # Will tell if there are any uncomitted changes, staged or not.
0.6 sec

git diff-index --quiet HEAD # Only tracked
2 sec

CSS Layout Debugger

A tweet-sized debugger for visualizing your CSS layouts. Outlines every DOM element on your page a random (valid) CSS hex color.

One-line version to paste in your DevTools

Use $$ if your browser aliases it:

~ 108 byte version

REG EX

Writeup

This is a writeup of the reversing challenge 'REG EX' from PlaidCTF 2015.

The challenge provided two files: a python server program and a crazy-huge regex (see regex.txt). The python server is very basic: it simply listens for a connection, prompts for a 'key', and then checks whether the key matches the regex. It will then send the flag, but only if the provided key did NOT match the regex.

After the initial shock of looking at many screenfulls of regex, it actually breaks down into simple chunks. The regex consists of a single group which must match the entire string (^(...)$), containing a number of alternatives. Because we need to find a string which does not match the regex, we need to ensure that none of the alternatives match our string. The first alternative (.*[^plaidctf].*) will match any string which contains any character not in 'plaidctf', so we know our solution will contain only those characters. The second two alternatives (.{,170}|.{172,}) will match any string

	#!/bin/bash

	OPENSSL_VERSION="1.0.1g"

	curl -O http://www.openssl.org/source/openssl-$OPENSSL_VERSION.tar.gz
	tar -xvzf openssl-$OPENSSL_VERSION.tar.gz
	mv openssl-$OPENSSL_VERSION openssl_i386
	tar -xvzf openssl-$OPENSSL_VERSION.tar.gz
	mv openssl-$OPENSSL_VERSION openssl_x86_64
	cd openssl_i386

	#ifndef __FINK_ENDIANDEV_PKG_ENDIAN_H__
	#define __FINK_ENDIANDEV_PKG_ENDIAN_H__ 1

	/** compatibility header for endian.h
	* This is a simple compatibility shim to convert
	* BSD/Linux endian macros to the Mac OS X equivalents.
	* It is public domain.
	* */

	#ifndef __APPLE__

	# Xcode 4.3.3
	Apple clang version 3.1 (tags/Apple/clang-318.0.61) (based on LLVM 3.1svn)
	Target: x86_64-apple-darwin11.4.0
	Thread model: posix

	# Xcode 4.3.2
	Apple clang version 3.1 (tags/Apple/clang-318.0.58) (based on LLVM 3.1svn)
	Target: x86_64-apple-darwin11.4.0
	Thread model: posix

	#!/bin/bash


	if [ -z "$1" ]; then
	echo
	echo usage: $0 network-interface
	echo
	echo e.g. $0 eth0
	echo
	echo shows packets-per-second

	irb(main):008:0> crx = open('emoine.crx', 'rb')
	=> #<File:emoine.crx>
	irb(main):009:0> magic = crx.read(4)
	=> "Cr24"
	irb(main):010:0> version = crx.read(4).unpack("i*")
	=> [2]
	irb(main):011:0> public_key_length = crx.read(4).unpack("i*")
	=> [162]
	irb(main):012:0> signature_length = crx.read(4).unpack("i*")
	=> [128]

	# v2 pbzx stream handler
	# My personal writeup on the differences here: https://gist.github.com/pudquick/29fcfe09c326a9b96cf5
	#
	# Pure python reimplementation of .cpio.xz content extraction from pbzx file payload originally here:
	# http://www.tonymacx86.com/general-help/135458-pbzx-stream-parser.html
	#
	# Cleaned up C version (as the basis for my code) here, thanks to Pepijn Bruienne / @bruienne
	# https://gist.github.com/bruienne/029494bbcfb358098b41

	import struct, sys