Enhance postUpgradeTasks with self hosted renovate

[dspaeth-breuni]

When using self-hosted Renovate with postUpgradeTasks configured, there is a significant trust requirement in the projects being checked. This configuration allows for the execution of arbitrary commands post-upgrade, which can potentially be exploited for malicious purposes. Even when you use allowedPostUpgradeCommands in your configuration.

Example Configuration:

"postUpgradeTasks": {
    "commands": [ "./gradlew dependencies --write-locks" ],
    "fileFilters": [ "gradle.lockfile", "buildscript-gradle.lockfile" ],
    "executionMode": "branch"
}

The flexibility of postUpgradeTasks to execute any script or command introduces a risk, especially in a scenario where a project's build script (./gradlew in this example) could be maliciously modified. For instance, an altered gradlew script could include harmful commands like ps -ef >> gradle.lockfile, or other shell commands that could compromise security, extract sensitive information, or execute unauthorized actions.

To mitigate this risk, could a sidecar container approach be considered? The idea is to isolate the execution environment of the tools called by postUpgradeTasks. By utilizing a sidecar container equipped with a pre-approved suite of tools, Renovate can operate in a secure, controlled environment, eliminating the dependency on repository-provided tools and enhancing overall security. This method would significantly reduce the risk of executing potentially malicious code and improve security by:

• Limiting the scope of accessible commands and tools to those explicitly included in the sidecar.
  

• Isolating the execution context from the main application or project environment.
  

• Providing a more controlled and secure way to manage dependencies and post-upgrade tasks.
  

Looking forward to your thoughts and any further suggestions.

[rarkins]

As far as I can tell, the attack vector here is that your own developers wish to exploit you, the operator of your company's Renovate instance. For most companies this is an edge case, because malicious developers within a company can likely do far worse than compromise a Renovate instance. Do you have a different viewpoint on that?

On the technical matter, Renovate supports binarySource=docker, which runs such child processes in its own sidecar image.
If you are referring to k8s sidecars, that would be a pretty large amount of work, which we don't currently plan to do.

[dspaeth-breuni]

Yes, I'm specifically referring to a Kubernetes (k8s) environment.

It's important to note that access to tools like GitLab isn't exclusive to developers; in some organizations, various team members can create repositories. And some times there are CVE's.

While the potential risks associated with CI jobs are well recognized, the dangers posed by postUpgradeTasks might not be as apparent. At a glance, it seems harmless enough – merely creating a gradle.lockfile, right?

Additionally, Renovate is frequently set up to automatically detect new repositories. An attacker could create a malicious repository and, once Renovate automatically initiates its tasks (including postUpgradeTasks), subsequently delete the repository, leaving behind little to no trace of the attack.

However, CI runners are typically safeguarded through multiple layers of security, a precaution that doesn't seem as evident for postUpgradeTasks. The feature allowedPostUpgradeCommands might offer a false sense of security. It requires the same level of cautious configuration as a sudo setup does. The moment you prefix a command with ./, you're potentially opening up a security vulnerability, even a simple call to gradle may do this.

Firstly, a malicious user could exploit this to gain access to sensitive environment variables, such as MEND_RNV_GITLAB_PAT, which often carries more privileges than the user's regular permissions allow.

Furthermore, within a k8s environment, the Renovate pod is not typically perceived as a significant threat, which means it may not be as securely configured as it should be. This oversight could inadvertently allow for broader access to the entire cluster.

Perhaps this issue could be mitigated with better documentation, emphasizing the potential security risks and recommending best practices for securing postUpgradeTasks in a Kubernetes environment.

[rarkins]

Docs PRs on this topic are welcome

[dspaeth-breuni]

I'm unsure where to place these documents, but here is my suggestion for improving them.

Security Advisory for Self-Hosted Renovate Instances

Overview

When using self-hosted versions of Renovate for dependency management, it is imperative to understand the security implications associated with monitoring and updating repositories. The process that Renovate uses to update dependencies runs under the same user context as the Renovate process itself. This means it has the same level of access to information and resources.

Trusting Repository Developers

Key Point: All self-hosted Renovate instances must operate under a trust relationship with the developers of the monitored repositories.
Implications

1. Access to Information: Since the update process runs with the same user privileges as the Renovate process, it inherently has access to the same information and resources. This includes sensitive data that may be stored within the environment where Renovate is hosted.

2. Execution of Code: In certain scenarios, code from the monitored repository is executed as part of the update process. This is particularly true during postUpgradeTasks, where scripts specified by the repository are run. These scripts can contain arbitrary code, which poses a significant security risk if the repository's integrity is compromised or if the repository maintainers have malicious intentions.

Centralized Logging and Sensitive Information Management

While centralized logging plays a pivotal role in monitoring and troubleshooting within self-hosted Renovate environments, it inadvertently bears the risk of capturing and exposing sensitive information. Operations that involve customEnvVariables, among others, could lead to such exposures when sensitive data is logged.

Recommendations

1. Vet and Monitor Repositories: Before integrating a repository with your self-hosted Renovate instance, thoroughly vet the repository for security and trustworthiness. This includes reviewing the repository's ownership, contribution history, and open issues or pull requests for security concerns.

2. Limit Permissions: Configure the environment running Renovate with the principle of least privilege in mind. Ensure that the Renovate process has only the permissions necessary to perform its tasks and no more. This can help mitigate the impact of any malicious code execution.

3. Regularly Review Post-Upgrade Tasks: Regularly review the actions taken by postUpgradeTasks to ensure they do not execute unnecessary or risky operations. Consider implementing a review process for changes to these tasks within repositories.

4. Use Security Tools: Employ security tools and practices, such as code scanning and vulnerability assessments, on both the Renovate configuration and the repositories it manages. This can help identify potentially malicious code before it is executed.

5. Securing Environment Variables: When configuring customEnvVariables, always opt for Renovate's secrets management syntax ({{ secrets.VAR_NAME }}) to reference sensitive variables securely. This approach ensures that sensitive data is not exposed in plain text.

6. Logging Infrastructure Security: Ensure that the logging infrastructure is configured to handle logs as sensitive data. This includes measures like log encryption, access controls to restrict log viewing to authorized personnel only, and secure storage and transmission of log data.

7. Log Review and Redaction Processes: Implement rigorous log review mechanisms to regularly scan for and redact sensitive information that might be logged inadvertently. Automated tools can assist in identifying patterns indicative of sensitive data, such as credentials or personal information, enabling timely redaction or alerting.

8. Stay Informed: Keep abreast of updates and security advisories related to Renovate itself. Apply updates promptly to ensure that your self-hosted instances benefit from the latest security enhancements and bug fixes.

Conclusion

The flexibility and power of Renovate come with the responsibility to manage security proactively. By understanding the risks associated with repository management and taking steps to mitigate those risks, organizations can maintain a secure and efficient development workflow.

[rarkins]

@dspaeth-breuni what if it were added to the bottom of https://docs.renovatebot.com/security-and-permissions/ ?

[HonkingGoose]

I opened a PR to put this info in the docs, with some of my changes on top:

• docs: add security awareness for self-hosted users #28415