Pipelines do not validate child UIDs
Date: 2023-07
Affected: go/github.com/tektoncd/pipeline
Attack vector: other
Category: vulnerability-disclosure
Severity: Low
CVE: CVE-2023-37264
CWE: CWE-345
CVSS: 3.7 (CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:L/I:L/A:N)

### Summary Pipelines do not validate child UIDs, which means that a user that has access to create TaskRuns can create their own Tasks that the Pipelines controller will accept as the child Task. We should add UID to PipelineRun status and validate that child Run status/results only come from Runs matching the same UID. ### Details While we [store and validate the PipelineRun's (api version, kind, name, uid) in the child Run's OwnerReference](https://github.com/tektoncd/pipeline/blob/2d38f5fa840291395178422d34b36b1bc739e2a2/pkg/reconciler/pipelinerun/pipelinerun.go#L1358-L1372), we only store (api version, kind, name) in the [ChildStatusReference](https://pkg.go.dev/github.com/tektoncd/pipeline/pkg/apis/pipeline/v1beta1#ChildStatusReference) . This means that if a client had access to create TaskRuns on a cluster, they could create a child TaskRun for a pipeline with the same name + owner reference, and the Pipeline controller picks it up as if it was the original TaskRun. This is problematic since it can let users modify the config of Pipelines at runtime, which violates SLSA L2 Service Generated / Non-falsifiable requirements. I believe this is also true for [TaskRuns -> Pods since it looks like we only lookup by name](https://github.com/tektoncd/pipeline/blob/0b8349b770a76877051c9c790c94bf9ed897c75c/test/pipelinerun_test.go#L992), though I haven't tested this. If you have update permissions on tekton resources, you could also perform a similar bypass like this (beca


Mitigations:

Architectural layers (MAESTRO):