Path traversal in Tekton Pipelines git resolver allows reading arbitrary files from the resolver pod

Summary

The Tekton Pipelines git resolver is vulnerable to path traversal via the pathInRepo parameter. A tenant with permission to create ResolutionRequests (e.g. by creating TaskRuns or PipelineRuns that use the git resolver) can read arbitrary files from the resolver pod's filesystem, including ServiceAccount tokens. The file contents are returned base64-encoded in resolutionrequest.status.data.

Details

The git resolver's getFileContent() function in pkg/resolution/resolver/git/repository.go constructs a file path by joining the repository clone directory with the user-supplied pathInRepo parameter:

fileContents, err := os.ReadFile(filepath.Join(repo.directory, path))

The pathInRepo parameter is not validated for path traversal sequences. An attacker can supply values like ../../../../etc/passwd to escape the cloned repository directory and read arbitrary files from the resolver pod's filesystem.

The vulnerability was introduced in commit 318006c4e3a5 which switched the git resolver from the go-git library (using an in-memory filesystem that cannot be escaped) to shelling out to the git binary and reading files with os.ReadFile() from the real filesystem.

Impact

Arbitrary file read — A namespace-scoped tenant who can create TaskRuns or PipelineRuns with git resolver parameters can read any file readable by the resolver pod process.

Credential exfiltration and privilege escalation — The resolver pod's ServiceAccount token is readable at a well-known path (/var/run/secrets/kubernetes.io/serviceaccount/token). In the default RBAC configuration, the tekton-pipelines-resolvers ServiceAccount has get, list, and watch permissions on secrets cluster-wide. An attacker who exfiltrates this token gains the ability to read all Secrets across all namespaces, escalating from namespace-scoped access to cluster-wide secret access.

Patches

Fixed in 1.0.x, 1.3.x, 1.6.x, 1.9.x, 1.10.x.

The fix validates pathInRepo to reject paths containing .. components at parameter validation time, and adds a containment check using filepath.EvalSymlinks() to prevent symlink-based escapes from attacker-controlled repositories.