Trace my libraries

Trace my libraries

Author: Marin Radu

Description

Investigate a binary's system call activities to discover hidden function calls and decode the underlying behavior.

Requirements

• Binary analysis
• ltrace utility

Solve

Inspect the binary with ltrace to trace library calls and spot the concealed operations. The binary performs obfuscation which can be reversed to reveal the flag.

ltrace ./vuln

The output from ltrace won't immediately show the complete information due to the limited buffer size, so adjusting the string size parameter is necessary.

ltrace -s 100 ./vuln

You can see the initial scripts:
Create the encoded flag: encode.py
Script before compilation: vuln.c

Flag: CSCTF{l3t.s_trAc3_the_libr@r13S_______________________bUT_w3_n3ED_the_bIg.piCtUr3}