GHSA-j5q5-j9gm-2w5c: Path traversal in Tekton Pipelines git resolver allows reading arbitrary files from the resolver pod
SummaryThe 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`.DetailsThe 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: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.PatchesFixed 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.WorkaroundsThere is no workaround other than restricting which users can create `TaskRuns`, `PipelineRuns`, or `ResolutionRequests` that use the git resolver. Administrators can also reduce the impact by scoping the resolver pod's ServiceAccount RBAC permissions using a custom `ClusterRole` with more restrictive rules.Affected VersionsAll releases from **v1.0.0** through **v1.10.0**, including all patch releases:v1.0.0, v1.1.0, v1.2.0v1.3.0, v1.3.1, v1.3.2v1.4.0, v1.5.0, v1.6.0, v1.7.0v1.9.0, v1.9.1, v1.10.0Releases prior to v1.0.0 (e.g. v0.70.0 and earlier) are **not affected** because they used the go-git library's in-memory filesystem where path traversal cannot escape the git worktree.AcknowledgmentsThis vulnerability was reported by Oleh Konko (@1seal), who provided a thorough vulnerability analysis, proof-of-concept, and review of the fix. Thank you!ReferencesFix: _(link to merged PR/commit)_Introduced in: `318006c4e3a5` ("fix: resolve Git Anonymous Resolver excessive memory usage")
CVSS v3.1: 9.6