Media
General problem description We got a 9 hours long video captured with a webcam on the top of a tall building in Tokyo(?). Find the flag. Solution First our guess was, that there will be a single frame which shows the flag, but fast-forwarding the video did not reveal anything like that. The next idea was to export every frame and use fuzzy hashing to find very different frames. While the script was doing the exporting we were fast-forwarding the...
Read Morereversing
General problem description We were given a arm64 ELF-Binary which was accessing a special device named xorshift64. The flag and some additional random values were hard-coded into the elf. Solution The ELF does more-or-less the same as this pseudocode: # init device #with open('/dev/xorshift64', 'r') as d: d.write(0x139408fcbbf7a44) # decode flag with open('/dev/xorshift64', 'r') as d: for i
reversing
General problem description Given was a Windows binary, which was apparently waiting to be started with the correct cmd arguments. Solution The binary checked character by character the cmd arguments with a hard-coded value which was: "C:\\Temp\\SECCON2018Online.exe" SECCON{Runn1n6_P47h} The flag was: SECCON{Runn1n6_P47h}...
Read MoreNo weekly meetup today.
We are not holding a weekly meetup today. Enjoy the long weekend....
Read MoreMISC
General problem description Similar to the previous challenge we got two images (see below) and a pcap. Solution Like before we use the found wireshark dissector to see what happens. However this time we find way more relevant packages than before. After some filtering we identified, that the base station sends only four different commands: OUTPUT_TIME_SPEED: go in a direction with a constant speed for given time OUTPUT_STEP_SYNC: turn given "ticks" long OUTPUT_STEP_SPEED: go in...
Read MoreMISC
General problem description For this challenge we got a picture of a Lego Mindstorm EV3, which displays the flag partly (see below). And we also got a pcap (OK, it was in the apple PackageLogger format) with captured Bluetooth transmission. Solution The pcap shows Bluetooth traffic, and wireshark finds furthermore identifies RFCOMM protocol. Some of them includes additional data parts. If you dig around long enough on the internet you can find a wireshark dissector written...
Read MoreRust Safe Code Bypass
Description I heard Rust is a safe programming language. So I built this CodePad where you can compile and run safe Rust code. Initial Situation We had access to a web-terminal with a limited set of commands: $ help help - print this help clear - clear screen ls - list files cat - print file content rusty - compile rusty...
Read Moretools
Because we decided on the meetup date on relatively short notice, we'll give an overview of the tools we regularly use. If requested, we can go into detail into certain topics. Where: @FH4, TU Wien (Wiedner Hauptstraße 8-10, 1040 Wien, Yellow Area) When: Thursday, 18.10.2018, 18:30 (CEST) What: Tooling overview...
Read MoreJavaScript Anti-Debug
General problem definition You stumbled upon someone's "JS Safe" on the web. It's a simple HTML file that can store secrets in the browser's localStorage. This means that you won't be able to extract any secret from it (the secrets are on the computer of the owner), but it looks like it was hand-crafted to work only with the password of the owner... The assignment was a Javascript file, which needs the Flag as input. Getting to...
Read MoreC64 BASIC Reversing
General problem description You won't find any assembly in this challenge, only C64 BASIC. Once you get the password, the flag is CTF{password}. P.S. The challenge has been tested on the VICE emulator. We got an old .prg file, which is a C64 program file. Parsing the file First we tried using parsers that exist in the wild, that would parse the file for us, but that proved to be not effective, as there were not many and...
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