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.
Workarounds
There 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 Versions
All releases from v1.0.0 through v1.10.0, including all patch releases:
- v1.0.0, v1.1.0, v1.2.0
- v1.3.0, v1.3.1, v1.3.2
- v1.4.0, v1.5.0, v1.6.0, v1.7.0
- v1.9.0, v1.9.1, v1.10.0
Releases 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.
Acknowledgments
This vulnerability was reported by Oleh Konko (@1seal), who provided a thorough vulnerability analysis, proof-of-concept, and review of the fix. Thank you!
References
- Fix: (link to merged PR/commit)
- Introduced in:
318006c4e3a5 ("fix: resolve Git Anonymous Resolver excessive memory usage")
References
1seal Reporter
vdemeester Remediation developer
afrittoli Remediation reviewer
KoreaSecurity Finder
Summary
The Tekton Pipelines git resolver is vulnerable to path traversal via the
pathInRepoparameter. A tenant with permission to createResolutionRequests(e.g. by creatingTaskRunsorPipelineRunsthat use the git resolver) can read arbitrary files from the resolver pod's filesystem, including ServiceAccount tokens. The file contents are returned base64-encoded inresolutionrequest.status.data.Details
The git resolver's
getFileContent()function inpkg/resolution/resolver/git/repository.goconstructs a file path by joining the repository clone directory with the user-suppliedpathInRepoparameter:The
pathInRepoparameter is not validated for path traversal sequences. An attacker can supply values like../../../../etc/passwdto escape the cloned repository directory and read arbitrary files from the resolver pod's filesystem.The vulnerability was introduced in commit
318006c4e3a5which switched the git resolver from the go-git library (using an in-memory filesystem that cannot be escaped) to shelling out to thegitbinary and reading files withos.ReadFile()from the real filesystem.Impact
Arbitrary file read — A namespace-scoped tenant who can create
TaskRunsorPipelineRunswith 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, thetekton-pipelines-resolversServiceAccount hasget,list, andwatchpermissions onsecretscluster-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
pathInRepoto reject paths containing..components at parameter validation time, and adds a containment check usingfilepath.EvalSymlinks()to prevent symlink-based escapes from attacker-controlled repositories.Workarounds
There is no workaround other than restricting which users can create
TaskRuns,PipelineRuns, orResolutionRequeststhat use the git resolver. Administrators can also reduce the impact by scoping the resolver pod's ServiceAccount RBAC permissions using a customClusterRolewith more restrictive rules.Affected Versions
All releases from v1.0.0 through v1.10.0, including all patch releases:
Releases 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.
Acknowledgments
This vulnerability was reported by Oleh Konko (@1seal), who provided a thorough vulnerability analysis, proof-of-concept, and review of the fix. Thank you!
References
318006c4e3a5("fix: resolve Git Anonymous Resolver excessive memory usage")References