Perl

Platform: CUSTOM | Category: Reversing | Type: Challenge | Difficulty: Easy | OS: N/A | **Author: XESXOR Techniques: base64_decode, eval_deobfuscation

Summary

Walkthrough of the CUSTOM Reversing Perl. Language: Perl. Source code provided. Obfuscated Perl script using base64-encoded eval.

Description

Language: Perl. Source code provided. Obfuscated Perl script using base64-encoded eval.

Analysis

Source code:

 perl read-only • copy allowed Copy
#!/usr/bin/env perl
use MIME::Base64;
print eval decode_base64('JGE9PD47IGlmICgkYSA9fiAicGVybHVzX2ZsYWd1cyIpeyJPa2F5X2l0KWlzX2ZpcnN0X3N0YWdlX2ZsYWcifWVsc2V7Ildvdywgbm9vIn0=');

Decoding the base64:

 perl read-only • copy allowed Copy
$a=<>; if ($a =~ "REDACTED"){"Okay_it)is_first_stage_flag"}else{"Wow, noo"}

The code reads input and checks if it contains the string "REDACTED". ‍​‌‌​​​​‌​‌‌​​‌‌​​‌‌​​‌‌​​‌‌​​‌​​​​‌‌​​​​​‌‌​​‌‌​​‌‌​​‌​‌​‌‌​​‌​‌‍

Solution

The flag is the string that passes the check: REDACTED. ‍​‌‌​​​​‌​‌‌​​‌‌​​‌‌​​‌‌​​‌‌​​‌​​​​‌‌​​​​​‌‌​​‌‌​​‌‌​​‌​‌​‌‌​​‌​‌‍

Key Takeaways / Lessons

• Mastering base64_decode, eval_deobfuscation was key to this challenge.
• Always check for common misconfigurations and verify assumptions.

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Crafted by XESXOR Research • 2026-03-09 • CUSTOM • Perl • Difficulty: Easy