OverTheWire Advent Bonanza 2019

Files reverse.py Challenge I ran this program but it never finished… maybe my computer is too slow. Maybe yours is faster? Inizialmente non avevo letto che la challenge fosse math e quindi ho subito pensato ad un ottimizzazione del codice. Ho iniziato a riscriverlo in python cachando le varie operazioni. Ottendendo cosi le 3 operazioni fondamentali che vengono utilizzate all’interno del <main>: @cached(cache={}) def pshufd(src,order): line=bin(src)[2:].rjust(128,"0") n=32 src=[line[i:i+n] for i in range(0, len(line), n)][::-1] #print(src) line=bin(order)[2:]....

Files change_perms.c 4bytes.py Challenge We have to change 4 bytes and we can give our name as input, so we can put something on the stack of the length that we want. Of course we want to put a shellcode on the stack, and use the 4 bytes to jump on it. The first problem is that NX was enabled, so we have to use 1 byte to disable it in the header....

The challenge allows the use of cowsay on a website. You can create a custom one, if you select ‘custom’ from the input list, meaning that you want to write a custom file that will be executed from cowsay with the ‘-f’ parameter. So the only things that I can work with is the body had to work with the body, but every command inside was not executed, just printed....

The challenge use a classic RSA sign and verify, without anything strange. So, differently from the others, I abused the fact that we can give both the Sign and the plaintext as inputs. Is enought to switch S with M when given as input, where S is calculated encrypting M with the public key that is given. Since verify(m,s): return m==encrypt(s,publickey) If we give verify(encrypt("AAAA",publicKey),"AAAA") # encrypt("AAAA",publickey)==encrypt("AAAA",publickey) we will pass the test....