Running shell commands through pdflatex and mpost - link
write18 - Stream 18 is 'special’ as it is not a file at all: instead, it is a way of sending commands to the operating system
CTF writeup1
Sends shell commands through an mpost file
CTF writeup2
Ascii Encoding - (Q: How are the Double Carats working?)
Black Hole - 10 pts
Open it in a hex editor, you will find the flag encoded in Base64 at the end
WoodStock-1 - 10 pts
Running strings gave away the answer here
WoodStock-2 - 55 pts
I spent some time initially looking at the conversation through wireshark. Looking at the BZ signature, I realised there might be some bzip2 files sent over the network(Later came to know about binwalk which extracts all of the files in a snap). I extracted them and found that the size of flag file is 14 and also came to know the TTH value. So, I realised the flag can be recovered with just a brute-force over all possible strings of 4 length size (BITSCTF{} has 9 bytes and one for the new line char). Unfortunately, we couldn't solve this in the competetion as we couldn't find a reliable TTH calculator. I tried using the tiger module in python with no success :( (Later: Investiage more on why this is happening)
Yep! tiger and TTH are different SO-link(look at one of the comments). Looks like TTH uses the tiger message digest and does some more other stuff. Here are some tools used by other teams - rhash, tthsum