Tekton Pipelines Git Resolver API Token Exfiltration Vulnerability

A vulnerability exists in the Tekton Pipelines Git resolver when used in API mode, specifically in versions 1.0.0 through 1.10.0. The issue arises because the resolver sends the system-configured Git API token to a user-controlled server URL if the user does not provide a token. This allows a tenant with permission to create TaskRuns or PipelineRuns to exfiltrate sensitive API tokens, such as GitHub Personal Access Tokens or GitLab tokens, by directing the server URL to an attacker-controlled endpoint.

Impact

Exfiltration of the system Git API token to an attacker-controlled endpoint. This token typically has read access to private repositories, including source code, secrets, and CI/CD configurations.

Reproduction

To reproduce this vulnerability, create a TaskRun or PipelineRun using the Tekton Pipelines Git resolver in API mode. Omit the token parameter and provide a server URL that points to an attacker-controlled endpoint. The Git resolver will automatically send the system-configured API token to the specified URL, allowing for token exfiltration.

Remediation

Do not configure a system-level API token in the Git resolver ConfigMap. Instead, require users to provide their own tokens via the token parameter. Additionally, restrict TaskRun creation to limit which users or ServiceAccounts can create TaskRuns and PipelineRuns that use the Git resolver.