Purushottam Sinha created FLINK-40709:
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Summary: Kubernetes Operator: allowlist to exempt trusted hosts
from jarURI restricted-host check
Key: FLINK-40709
URL: https://issues.apache.org/jira/browse/FLINK-40709
Project: Flink
Issue Type: Improvement
Components: Kubernetes Operator
Reporter: Purushottam Sinha
h3. Problem
kubernetes.operator.user.artifacts.disallow-restricted-hosts (default true)
rejects any FlinkSessionJob jarURI resolving to a private/loopback/link-local
address, which also blocks legitimate internal artifact stores (an in-cluster
Service, an on-prem Artifactory on a private address). The only workaround
today is disabling the check entirely, reopening SSRF exposure to everything --
including cloud metadata endpoints -- just to allow one trusted host.
h3. Evidence
* {{JarUriValidationUtils#validateJarURI}} enforces the restricted-host check
unconditionally when enabled, with no exemption mechanism.
* Related to FLINK-40402 / FLIP-613, which introduced the scheme allowlist and
restricted-host check this proposes to extend.
h3. Proposed fix
* Add {{kubernetes.operator.user.artifacts.allowed-uri-prefixes}}
(comma-separated jarURI prefixes, default empty) in
{{KubernetesOperatorConfigOptions.java}}.
* In {{JarUriValidationUtils#validateJarURI}}, skip only the restricted-host
check when the jarURI starts with a configured prefix; the scheme allowlist is
still enforced regardless.
* Wire the new option through {{FlinkOperatorConfiguration}},
{{HttpArtifactFetcher}} (re-checked on every redirect hop), and
{{DefaultValidator}} (admission-time validation for FlinkSessionJob).
h3. Acceptance
* A FlinkSessionJob jarURI resolving to a restricted address is denied by the
webhook by default, then accepted once its prefix is added to
{{allowed-uri-prefixes}}.
* Unit test coverage for both the exemption and the still-enforced scheme
allowlist.
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