miscfreeeasy

Cred Hunter

hackthebox

Task: Parse mixed emails and passwords, find valid credential pairs where the firstname from the email appears as a substring in the password. Solution: Extract firstname from email local part (all chars except last), check substring match against all passwords, sort pairs lexicographically.

$ ls tags/ techniques/
regexparsingstring_matchingcredential_pairing
substring_searchemail_parsinglexicographic_sorting

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Cred Hunter - HackTheBox

Challenge Info

FieldValue
EventHackTheBox
CategoryProgramming/Misc
DifficultyEasy
Target94.237.56.175:43741
FlagHTB{th4t_1s_4n_0bvi0us_p41r1ng}

Description

The data leaked quietly - unnoticed, unguarded, and brimming with opportunity. You're in deep now. A tangle of credentials spilled from a forgotten system connected to CygnusCorp's sprawling digital perimeter. Half garbage, half gold. Somewhere in this chaos are access keys - real names, real logins, real passwords. You just have to find the ones that match.

Analysis

This is a web-based coding challenge using Monaco editor interface. The task involves:

  1. Input: N strings containing a mix of emails and passwords
  2. Email Format: CygnusCorp uses firstname + first_letter_of_lastname@domain
  3. Valid Pair: An (email, password) pair is valid when the firstname (extracted from email) appears as a substring in the password
  4. Output: All valid pairs sorted lexicographically by email, then by password

Key Insight

The email format firstnameX@domain means:

  • Local part = firstname + first_letter_of_lastname
  • Therefore: firstname = local_part[:-1] (remove last character)

For example:

Solution

Algorithm

  1. Parse input - Read N strings
  2. Classify strings - Separate emails from passwords using regex
  3. Extract firstnames - For each email, get local_part[:-1]
  4. Find pairs - For each (email, password) combination, check if firstname is substring of password
  5. Sort and output - Sort pairs lexicographically (email first, then password)

Python Solution

import re

...

$ grep --similar

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