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}...
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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
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...
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General problem description We were given a moxie ELF-Binary which was implementing the xorshift32 PRNG algorithm. The flag and some additional random values were hard-coded into the elf. Solution Similar to the Special device file challenge the binary took the flag xored with a random value hard-coded into to binary and xored again with a value taken from the xorshift32 algorithm. The catch was again, that we didn't know the correct configuration of the algorithm only the seed and...
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...
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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 MoreAndroid APK Reversing
General problem description Win the game 1,000,000 times to get the flag. For this challenge we got an .apk file, which we should apperently run and win 1,000,000 times. We let the online Java-decompiler at http://www.javadecompilers.com/apk. Running the apk on an Android-Phone or emulator shows us the game: Tic Tac Toe. We also get a counter 0/1000000 on the bottom of the screen. Each win increases the counter by one. Naive approach by recompiling the app We used...
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