Top 9 Ways to Prevent Supply Chain Attacks on Your CI/CD Server

Safeguarding your systems from attacks.

11 min readJan 11, 2024

Your CI/CD server might be quietly humming in the background, but to cyber attackers, it’s a shiny prize. The workhorse drives your operations, the heart of your framework.

Sadly, it’s also increasingly a target for supply chain attacks. But don’t worry, there are ways to fight back which we’ll be walking through in this post.

Today, we’ll share with you nine simple, yet highly effective ways to protect your CI/CD server from these harmful infiltrations. You have the ability and the responsibility to ensure your server remains untamed; let’s find out how.

CI/CD Server

The CI/CD (Continuous Integration/Continuous Deployment) server is the nexus of all development activities. It’s a cardinal point that manages merging, testing, deploying, and delivering software. This server is like an artery that pumps life into the DevOps ecosystem, enabling frequent code integration. This concept of Continuous Integration (CI) encourages regular code input into a communal repository. Each of these entries undergoes automated validation. It functions like a warning system, ensuring problems are nipped in the bud.

The continuous deployment (CD) aspect means that code changes are automatically deployed into a production environment. This enables a smooth, swift, and secure route for software to be developed and released.

The CI/CD server minimizes risks and aids in spotting and rectifying issues earlier in the development lifecycle, thus reducing the overall time to release and the costs associated with delays. Utilizing a CI/CD server means adopting a proactive stance, valuing efficiency, and striving for better quality in software production.

Securing the CI/CD server is vital as it has access to your entire development infrastructure. Implementing correct access policies, maintaining build history, and archiving server logs are all part of ensuring a secure CI/CD environment.

Reasons for Securing your CI/CD Server

CI/CD Server: A Cybersecurity Target
CI/CD servers, the centers of developmental procedures, are prime targets for cyberattacks. Their capacity to manipulate the source code and live environments can lead to extensive implications if unprotected.
Risks of Uncontrolled Vulnerabilities
If hackers find just one weak spot, they can get into the supply chain and access sensitive information. They could even install harmful programs, and this is becoming more common.
Surge in Supply Chain Attacks
Reports and research underscore a worrying rise in supply chain attacks post-2020. Almost 57% of organizations have witnessed security incidents due to DevOps toolchain vulnerabilities.
Significance of CI/CD Server Security
Robust CI/CD server security is crucial to prevent data breaches and service disruptions that lead to considerable financial damage. Appropriate security practices can also enhance software delivery and reduce developer fatigue.

The Actual Risks of a Security Breach

Financial Losses
Potential financial repercussions of a breach can vary in severity, with organizations possibly confronting the need to redress impacted customers and initiate costly incident inquiries along with other responsive strategies. Moreover, fiscal penalties due to non-compliance may also be incurred. Beyond these immediate fiscal damages, businesses might also experience a decline in commercial engagements, causing a drop in their share prices. As per the “Cost of a Data Breach Report 2022”, the average financial toll incurred from a singular breach escalates to a daunting USD 4.35 million.

Operational Disruptions Via CI/CD Server
The probing and restoration procedures can be enormously time-consuming, frequently leading organizations to adjourn part or all CI/CD server operations during that tenure. Unquestionably, prolonged operational downtime increases the propensity of customer attrition fostering further revenue deficiency.

Damage to Reputation Through CI/CD Server Breaches
The contingency of losing present and prospective customers to rivals perceived as more secure escalates significantly in light of CI/CD server security compromises.

Legal Consequences Surrounding CI/CD Server Security
Breaches involving personal data and aimed at an organization’s clientele usually provoke class-action lawsuits. Often, authorities may confine companies from conducting certain business maneuvers until legal scrutiny surrounding their CI/CD server operations is finalized.

Enhancing the Security of your CI/CD Server

CI/CD servers are vulnerable to increasing security incidents as expressed by the “Top 10 CI/CD Security Risks” from the OWASP Foundation. Enhancing security is a persistent process, for which we provide useful advice, following the latest application security guidelines, to fortify your CI/CD pipelines and safeguard your business.

This reading outlines nine optimal strategies for bolstering the security of CI/CD solutions, regardless of whether they’re stationed on-site or in the cloud.

Top 9 Ways to Prevent an Attack

1. Update Your CI/CD Server Regularly
Top of the list is the advised regular updating of your in-house CI/CD server coupled with all related elements like build agents- always aiming for the most recent version.

Concurrently, proactively monitor security updates to ensure your system incorporates state-of-the-art security refinements in its operations. In short, keep your operating system in updated condition and consistently apply security patches.

For those utilizing a cloud-centred CI/CD framework, updates generally apply within the system automatically, although significant updates may warrant manual initiation.

2. Safeguard Your Credentials

The largest recurring factor for data breaches remains the utilization of absconded or compromised credentials. Intrusions resulting from these conditions bear a mean expenditure of upwards of USD 4.5 million.

Furthermore, these types of breaches typically possess the most prolonged lifespan, demanding an approximation of 243 days for identification and an additional 84 days for containment. So,

Utilize Robust Credentials with Care
Ensure reliable credentials for your comprehensive DevOps toolkit, inclusive of CI/CD server, and maintain them away from the following:
– Code repositories like GitHub, GitLab, and so on.
– Environmental variables, as these are frequently logged or disseminated with third-party monitoring systems.
– The build log — to discourage the inadvertent logging of sensitive data.
Preserve Confidential Data with the Password Parameter Type
If the need arises to store crucial passwords or any other sensitive data in your CI server settings, the password parameter type is recommended. This ensures such sensitive data never makes an appearance on the web user interface. Additionally, they remain asterisked in the build log, enhancing the security quotient
Deploy a Secrets Management Instrument
Another viable approach would be deploying a centralized secrets management solution. Your CI/CD server could utilize this to retrieve mandatory secrets at build runtime. This strategy permits the secure consolidation of all secrets into a single location. It also allows an automated system to rotate your secrets periodically — a process that often proves cumbersome when executed manually.
Incorporate External Authentication
Given that your institution employs a consolidated user management system, it would be prudent to consider an integration module that links it with the CI/CD server. The benefits of this approach are twofold: One, it negates the need for storing sensitive user information across varied locations, and two, it simplifies the process of streamlining identity and access management.
Implement Two-Factor Verification
There’s merit in employing 2FA, particularly for administrators or individuals with the authority to change build pipeline configurations. It necessitates the utilization of two distinct methods to verify identity, such as entering user credentials and using a smartphone app for instance.
Employ Encrypted SSH Keys
Part of ensuring the security of systems involves safeguarding SSH keys from unauthorized access. If these keys, unfortunately, land in the wrong hands, unauthorized entry to respective systems becomes an imminent risk. As such, it’s essential to protect your SSH keys using secure passphrase encryption when uploading them to the CI/CD server; thus rendering them unproductive to attackers.

3. Instigate Effective Identity and Access Regulations

A build server accessed by a malignant user can significantly jeopardize the build infrastructure and any users or systems that utilize the structures produced within it. If, unfortunately, a CI/CD server has been breached by an attacker, the proposition of the threat escalating is very likely. It’s mainly due to the extensive privileges typically allocated to CI/CD servers, positioning the attacker to slowly accrue more permissions. A well-orchestrated identity and access management strategy would be an efficient countermeasure to such threats.

Apply the Principle of Minimal Privilege
Only grant staff permissions that are necessary for their tasks. This not only concentrates access where needed but also reduces the risk if an attacker compromises a user by minimizing the attack surface. For instance, developers could be limited to the compilation part of the build pipeline, while DevOps engineers handle only the deployment aspect.
Utilize Groupings and Roles
Avoid assigning permissions to individual users to reduce potential attack vectors. Create user groups that mirror your organization’s structure and assign roles to these groups. Users are then attached to appropriate groups, granting them just the necessary privileges. It’s better to create new roles with specific permissions than quickly assigning all-encompassing admin roles to those needing more privileges.
Minimize Risk Facets Associated with Guest Users
Guest users are potential reservoirs for substantial security risks due to the inherent lack of control and accountability. Always refrain from enabling guest access to any production CI/CD servers unless necessary and justifiable.
Set up unique, restricted-permission users and tokens
For accessing the CI/CD server via an external script or program, it’s suggested to have a distinct user with limited permissions for API calls. Additionally, ensure regular rotation of API tokens to mitigate security threats.
Expunge Stale Users
Any users exiting your company or transitioning to unrelated roles or teams and therefore no longer requiring access should have their access rights swiftly rescinded.

4. Secure your On-premises CI/CD Server

Safeguard Your CI/CD Server
Restricted access should be the order of the day for the machine that your CI/CD server is operational on. Activate the collection of access logs and routinely scrutinize them to detect any unusual login activities on this critical component. Unsanctioned access to your CI/CD server by users can pave the way to all the settings, as well as the build and user data on the server, marking a sizeable security vulnerability.
Solidify Your External Database
Utilizing a self-hosted CI/CD server requires the same vigor in hardening the security of the external database powering it. The database houses all user-, job-, and build-related data. At a bare minimum, a dedicated user account fortified with robust credentials should be used for your CI/CD server’s database schema. Encryption should be seriously considered, provided your database supports it.
Implement HTTPS Across the Board
Standard practice these days is to enable HTTPS for your CI/CD server, thereby ensuring data transits across both directions are encrypted and secured, resulting in a resilient protection.

5. Monitor your Version Control Settings

Effectively Administer Your VCS SSH Keys
For those utilizing SSH keys to gain access to their repositories, avoid storing these keys on your build agents. A more secure approach is to use a dependable SSH key management system in tandem with your CI/CD server’s relevant SSH integration.
Employ a Dedicated VCS User
If your build process refrains from committing to your repository, which is a common scenario, it’s advisable to maintain a dedicated VCS user who boasts bare minimum ‘read’ privileges for your repositories.

6. Monitor Build Agent Configurations

Conduct Pristine Production Builds
Incremental build options can be a convenient choice for non-critical builds, allowing for the reuse of certain files from a previous build on the same agent, thereby accelerating the build process. However, when you’re crafting a production-ready variant of your application, be vigilant to always construct the final artifact entirely from scratch. This ensures protection against potential interference with source code on the agent.
Implement Disposable, Network-Protected Build Agents
Try to employ disposable, single-use build agents in your CI/CD tool whenever possible. The shorter the agent’s lifetime, the less opportunity there is for compromise. Also, incoming network access should be disabled for all potential cloud agents.
Refrain from Utilizing Multiple Build Agents on a Single Machine or Container
If you aren’t utilizing disposable, single-use build agents for your projects, be cognizant of the fact that compromised agents or untrusted projects may potentially alter source code in adjacent working directories. To counteract this risk, operate only one agent per machine or container and utilize different agent pools for different projects — both private and public.

7. Configure all Integrations Securely

Exercise Caution with Public Pull Requests
When dealing with pull requests from unfamiliar users or those outside your organization, it’s crucial to remember that these requests may contain harmful code that would execute on your build agent. It’s advisable to either prohibit building public pull requests or employ segregated, disposable agents.
Understand Security Risks with Versioned Settings
With the configuration as code approach, when versioned settings are placed in the same repository as the source code, a malevolent developer has the potential to modify and leak project configuration settings. For example, the developer could add a build step that reveals passwords or transfers them as a file. A potential solution is using a separate repository for your versioned settings, only granting commit access to select users, provided your CI/CD server supports this feature.
Use Third-Party Plugins Wisely
When installing plugins, it’s necessary to ensure they originate from a trusted source and that their source code is accessible. Plugins have the potential to access all information on a CI/CD server, including sensitive data, thereby considerably expanding the attack surface.

8. Maintain Strict Security Practices for Artifact Storage

Deactivate Anonymous Access
No matter the location of your build artifacts storage (for instance, AWS S3), it’s vital to deactivate anonymous access to your storage site.
Implement Correct Access Policies
Appropriate access policies must be used to protect your S3 or other storage locations and artifact repositories. When possible, use encryption. Ensure to regularly monitor and review access logs of your storage locations.
Avoid Storing Sensitive Data within Artifacts
It might seem evident, yet merits reiteration — never store credentials or any other sensitive data as plain text within a build’s artifacts.

9. Store your Build History and Logs

Maintain Build History
Preserving your build history and logs can be crucial, especially for builds that execute critical deployments or release versions of your software. This preservation aids in tracing and investigating unauthorized activity, even if it occurred in the distant past, and may bea compulsory requirement for multiple compliance audits.
Gather Server and Agent Logs
Amass logs from CI servers and build agents, store them in an archive and keep these in a suitably secure location. This will be of utmost importance if there’s a need for a security investigation or compliance audit in the future.

As the digital sphere has its own set of entanglements, fortifying the CI/CD server consistently stands as a primary strategy to outsmart software supply chain attacks. As per the observation, these attacks mounted an increase of over 300% in 2021. Furthermore, a staggering 82% of CIOs acknowledge that their organizations are exposed to threats that target software supply chains. Therefore, ensuring the CI/CD server’s safety serves as not just an option, but indeed a compulsory drill.

By exercising the previously stated strategies, it becomes feasible to cement the security features of your CI/CD server and pare down the susceptibility to data breach repercussions.

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