CI/CD Pipeline Hardening

CI/CD pipelines are prime targets for attackers. They have access to source code, secrets, and production environments. A compromised pipeline can inject malicious code into every deployment, steal credentials, or pivot to internal systems. High-profile attacks like SolarWinds and Codecov demonstrate the devastating impact of pipeline compromises.

Pipeline hardening is about reducing the attack surface of your build and deployment infrastructure. This means isolating runners, protecting secrets, validating artifacts, and implementing the principle of least privilege throughout your pipeline.

This guide covers practical techniques to secure GitHub Actions, GitLab CI, Jenkins, and other CI/CD platforms against modern threats.

What You'll Learn

This guide consists of the following parts:

1. Pipeline Security Fundamentals - Threat model, attack vectors, and security principles
2. Runner and Environment Security - Isolation, hardening, and ephemeral environments
3. Secrets and Credentials - Secure secret management, rotation, and access control
4. Artifact Security - Signing, verification, and supply chain integrity

Why Pipeline Security Matters

Consider these attack scenarios:

• An attacker compromises a dependency and injects code that runs during your build
• A malicious pull request modifies the CI config to exfiltrate secrets
• Stolen CI credentials are used to push malicious artifacts to production
• A compromised build artifact contains a backdoor that deploys to all environments

Each scenario represents a real attack pattern. The 2020 SolarWinds attack inserted malicious code during the build process, affecting 18,000 organizations. The 2021 Codecov breach exposed secrets from thousands of repositories through a compromised bash uploader.

Pipeline Threat Model

Understanding threats helps prioritize defenses:

Threat	Impact	Likelihood
Compromised dependencies	Code injection, data theft	High
Secret exposure	Credential theft, lateral movement	High
Malicious PR attacks	Pipeline hijacking	Medium
Runner compromise	Persistent access, code injection	Medium
Artifact tampering	Supply chain attacks	Medium
Configuration drift	Security control bypass	High

Prerequisites

This guide assumes you have:

• Experience with at least one CI/CD platform (GitHub Actions, GitLab CI, Jenkins)
• Basic understanding of containerization and infrastructure
• Familiarity with secrets management concepts

Let's secure your pipelines!