Pivot Chain Challenge

hackthebox

Task: Find minimum detection risk path through a network graph. Solution: Dijkstra algorithm with priority queue for weighted shortest path.

python graph dijkstra shortest_path algorithms web_api heapq

api_interactiongraph_traversaldijkstra_algorithmpriority_queue

$ ls tags/ techniques/

python graph dijkstra shortest_path algorithms web_api heapq

api_interactiongraph_traversaldijkstra_algorithmpriority_queue

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Pivot Chain Challenge — HackTheBox

Description

After bypassing CygnusCorp's perimeter defenses and cracking the PIN to gain internal access, you've uncovered a crucial piece of the network: the Core Administration Server. Your goal is to pivot laterally through the internal network to reach the server, but the path is not clear. The network is heavily monitored, and each host you move through carries a detection risk. Can you navigate the network stealthily, identify the safest paths, and reach the Core Administration Server without being detected?

Target: 94.237.120.233:40330

Analysis

Reconnaissance

Connected to the service — discovered an HTTP server with a web code editor
Page title "Pivot Chain" with an interface for solving challenges
Found API endpoint /run for submitting code in Python, C, C++ or Rust

Challenge Format

Input: N (hosts), M (paths), start host, target host
Then M lines of edges: source destination risk
Output: minimum total detection risk from start to target
Constraints: 5 <= N <= 150000, 6 <= M <= 10^6
Example: 5 hosts, 6 paths, optimal path host_1→host_2→host_3→host_4→host_5 with total risk 26

Algorithm Selection

This is a classic shortest path problem in a weighted directed graph:

Dijkstra's algorithm — optimal for finding minimum cost path
heapq from Python — efficient priority queue implementation
Complexity: O((V + E) log V)

Solution

import sys
import heapq
from collections import defaultdict

...