HTB CPTS Walkthrough: CPTS 13-14 methodology

HTB CPTS Walkthrough: CPTS 13-14 methodology

Category: Hack The Box Certification Series ??? Advanced Penetration Testing ??? Read Time: 14 min

Compromising the primary Domain Controller in an enterprise assessment often feels like checkmate, but in modern segmented architectures, it is merely the opening gambit. Mature defense-in-depth implementations isolate high-value infrastructure???specifically developer subnets, staging pipelines, and operations tooling???behind dedicated firewall boundaries, jump boxes, and non-routable interfaces. When the primary Kerberos domain is fully mapped and subdued, elite operators inevitably discover that the crown jewels of enterprise control live upstream in unmanaged CI/CD pipelines and administrative enclaves.

Transitioning from domain hegemony to multi-subnet infrastructure dominance demands a distinct operational paradigm. Standard lateral movement techniques fall short when intermediate hosts enforce strict egress filtering or segment dual-homed developer clusters away from production Active Directory trusts. Success in this final phase hinges on weaponizing software supply chains, cracking infrastructure-as-code automation secrets, and establishing resilient multi-tiered routing tunnels.

Phase 1: Deep Network Pivoting & Traffic Routing

Once initial domain foothold servers or secondary domain controllers are compromised, operators frequently encounter dual-homed network adapters bridging standard corporate subnets to isolated development networks. Traditional SOCKS proxies configured via SSH or simple dynamic port forwarders introduce crippling latency, fail to pass raw UDP traffic, and break complex reconnaissance tooling like asynchronous port scanners or raw LDAP queries.

To bridge this boundary effectively, modern methodology relies on TUN-interface tunneling frameworks such as Ligolo-ng or multiplexed tunneling via Chisel. By instantiating a virtual TUN device directly on the attack platform, the operator establishes deterministic Layer 3 network routing straight through the compromised dual-homed host.

This routing paradigm transforms pivoting from a fragile proxy-chain exercise into seamless subnet traversal. Instead of wrestling with individual proxy configuration files, the kernel routes entire CIDR blocks directly through the tunnel interface. This architectural vantage point allows operators to probe internal gateway addresses, map internal DNS zones, and discover unannounced staging environments that are completely invisible from the external perimeter.

Phase 2: Cracking Automation Infrastructure

In heavily automated DevOps ecosystems, systems engineers rarely manage server configurations manually. Instead, configuration management orchestrators???predominantly Ansible, Puppet, or SaltStack???maintain server states across both Windows and Linux instances. The compromised infrastructure nodes themselves often host the playbooks, staging directories, or repository clones used to deploy production configurations.

Senior penetration testers systematically audit compromised developer machines and storage mounts for encrypted automation artifacts, specifically Ansible Vault files ($ANSIBLE_VAULT). While Ansible uses robust symmetric encryption (AES-256) to secure sensitive variables, developers frequently rely on shared master passwords or predictable organizational passphrases to encrypt vault credentials.

• Locate Encrypted Repositories: Search developer working directories for YAML playbooks containing encrypted strings or standalone vault files.
• Hash Extraction & Exfiltration: Parse the vault ciphertext blocks to format them for offline cracking engines without altering host integrity.
• High-Throughput GPU Cracking: Leverage targeted wordlists, corporate mutations, and rule-based cracking against the vault header to recover the master passphrase.

Recovering an Ansible Vault master password is often a catastrophic break for the target organization. Because automation files routinely store administrative passwords for non-domain-joined nodes, API tokens for deployment clusters, and cross-platform service account credentials, a single offline crack frequently unlocks administrative access across the entire development fleet.

Phase 3: Exploiting CI/CD & Developer Tools

With infrastructure credentials harvested from decrypted configuration vaults, lateral movement transitions to developer portals and artifact repositories. In modern enterprise enclaves, services like Sonatype Nexus Repository Manager, SonarQube, and self-hosted GitLab instances operate with excessive trust. These applications sit at the crossroads of software distribution, holding broad service privileges on underlying host operating systems.

Attackers target these management web portals not to alter source code, but to leverage native administrative features that allow arbitrary code execution:

• Administrative Scheduled Tasks: Enterprise artifact managers frequently provide system tasks for maintenance, script execution, or custom Groovy console execution. Legitimate administrative credentials grant the capability to define tasks that execute native system commands directly within the JVM context.
• Custom Plugin & Package Ingestion: Systems that accept custom integrations, extensions, or analyzer plugins allow operators to package custom payloads into signed or unsigned plugin formats. When deployed through legitimate administrative portals, the application unpacks and runs the code at the service user's privilege level.
• Credential Scavenging in Build Configurations: Code quality gateways and build mirrors retain persistent authentication tokens for build nodes, cloud registries, and staging servers, offering lateral pivoting vectors deeper into isolated network zones.

Because these developer portals operate internally behind firewalls, they are rarely patched with the same urgency as edge appliances, frequently leaving known feature-abuse chains completely unobstructed.

Phase 4: Achieving Absolute Domain Dominance

Securing code execution on a development staging node or CI/CD master server opens the final avenue of lateral movement: extracting stored OS secrets to conquer auxiliary network appliances and isolated management platforms.

Development servers frequently require connectivity to non-Active Directory assets, including internal network switches, hypervisor consoles, and web-based management utilities such as Webmin, enterprise HR trackers, or firewall administrative dashboards. Operators employ targeted post-exploitation credential harvesting:

• LSA Secrets & Registry Dumps: Querying Local Security Authority (LSA) secrets on Windows developer workstations reveals stored credentials for service accounts, VPN profiles, and auto-logon routines.
• Linux Credential Extraction: On Linux-based CI nodes, inspecting systemd environment files, cached credential managers, and localized SSH agent sockets provides valid access tokens across administrative tiers.
• Management Dashboard Access: Utilizing harvested administrative tokens against systems like Webmin delivers unconstrained root command execution across isolated standalone nodes.

When these credentials match administrative panels running on appliances like Webmin or enterprise intranet dashboards, operators achieve total operational closure. By compromising administrative web interfaces that execute commands directly as root or system-level daemons, the boundary between the Active Directory domain and the physical or virtual underlying hypervisor collapses entirely.

Strategic Summary: Securing Internal Supply Chains

Enterprise security cannot end at the Domain Controller. Active Directory hardening is rendered meaningless if the automation engines, repository managers, and dual-homed developer enclaves capable of provisioning that infrastructure remain vulnerable.

From a defensive operations standpoint (such as SOC analysts preparing for certifications like OffSec's OSDA (SOC-200) or mastering threat detection via OSDA Elastic Stack Analysis), hunting for anomalous TUN interface creation, unauthorized vault extraction, and unusual JVM child processes is critical to catching sophisticated lateral movement before entire subnets fall.