From Technologia Incognita
| CTF-practice-evening:2014-07-07
|
| Date
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2014/07/07
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| Time
|
|
| Location
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ACTA
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| Type
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Workshop
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| Contact
|
Melanie
|
Capture The Flag evening - Part 21
- 7 July, 2014 - 7 PM
- Please bring along a laptop with you!!!
General CTF Info
Pwnium CTF Retrospective
- Link to Dimitris' Etherpad
- Link to download the challenges:
Walk throughs
- Dimitris is discussing the challenges solved by Team Knuffelhackers in the Pwnium CTF last weekend
- Kernel land (150 points):
- Static binary - Dimitris loaded it into QEMU
- When he runs it it produces ticks - the hint: the flag is on the 3rd ticket
- He added a debugger to the VM
- He put a breakpoint on timer tick - and there's also a variable called 'flag'
- He needed to add the symbols to GDB
- He single stepped through the "ticks" , through the 3rd tick, and then examine the flag variable in memory at Tick 3
- USB is fun (100 points):
- We're given a pcap file with a USB transaction
- He was able to find the flag just by running strings on it!
- Look closer (50 points)
- We got a rar file that is actually a jpeg
- If you look at the jpg file, you can see the flag
- Break me (100 points)
- Dimitris base 64 decoded it - it's a bzip2 file
- Dimitris decompressed it w/ bunzip
- This gave the flag value
- So basic (75 points)
- He is given a zip file containing 2 byte strings
- Each of these hashes represents a number 1-40
- He wrote a bash script that puts these things in order
- It's a chain of MD5 hashes
- If it's present in the directory, you copy this to flag.txt
- If you hex decode this (i.e. in Python) then you get the flag value
- Altered code
- We're given a main.c file with some computations, rotations, and a secret code
- He noticed 2 places where indentation was broken (somebody had modified the files)
- He commented these lines out, and then the program gave the flag when run
- ROT (300 points)
- A URL and port # gave a base 64 string, it expected an answer for about 5 seconds, and then closed down
- If he decodes the string, it gives you a string - but you only have 5 seconds to extract the text and submit it as a flag!
- He started looking into image transformations w/ Python
- He used Python to clean up the image - then he needed OCR to extract the text
- He converted the image to black and white
- He was using an OCR program called "cuneiform"(?)
- Baybe crackme
- You get the flag by adding an arbitrary command line parameter
- Find the owner:
- This binary was connecting to a Tunesian government website
- He concatenated the ip address and port, and that was a flag
- Be a robot
- Buffer overflow - jump to a function - get a shell from there
- Dimitris solved it locally but not remotely
