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fix!: stop leaving the GKE control plane open to every address - #5
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The public GKE endpoint was always enabled and master authorized networks were only configured when authorized_networks was non-empty, so the default cluster accepted any address. Master authorized networks are now always managed with Google Cloud public IP access disabled. The API is reachable only from authorized_networks, only on the private endpoint with the new enable_private_endpoint, or from any address only with the new allow_public_api_server opt-in. The plan fails until one mode is chosen, and ranges broader than /8 (IPv4) or /16 (IPv6) need the opt-in. In private-endpoint mode the kubectl_config_command output adds --internal-ip. The example takes the allowlist as a required input and uses the module source from this repository. CI runs mock-provider tests for the new rules and validates the example. BREAKING CHANGE: a configuration with an empty authorized_networks no longer plans. Set authorized_networks (an in-place update that adds master_authorized_networks_config), set enable_private_endpoint = true (an in-place update; requires enable_private_nodes), or set allow_public_api_server = true to keep the previous behaviour with no plan change. Configurations that already set authorized_networks keep working; Google Cloud public IP access is now pinned to disabled.
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Included review availability: This review used your included allowance. 0 included reviews remain after this review. Your included PR review attempts over the past 7 days set your current allowance at 4 reviews per hour. 📝 WalkthroughWalkthroughThe module adds Kubernetes API access settings for authorized CIDRs, private endpoints, and explicitly unrestricted public access. It validates and applies these settings, adds Terraform tests, and updates the documentation and dev-l4-spot example. ChangesKubernetes API access
Suggested reviewers: Priority: ➖ Normal Merge Risk: ⚪ Minimal · up to The example and CI flow preserve the intended setup, with users instructed to provide their own authorized CIDR. No actionable merge blocker remains. 🚥 Pre-merge checks | ✅ 5✅ Passed checks (5 passed)
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Review comments at @main.tf:
- Line 157: Update the GKE private-cluster configuration near
gcp_public_cidrs_access_enabled to enable private_endpoint_enforcement_enabled
only when var.enable_private_endpoint is true and var.authorized_networks is
non-empty. Preserve the empty-list private-endpoint behavior by leaving
enforcement disabled in that case.
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In private-endpoint mode, authorized_networks was not applied to the private endpoint, so listed internal ranges did not restrict access. Set private_endpoint_enforcement_enabled when the private endpoint is used with a non-empty list, and leave it unmanaged otherwise so the module never turns an existing enforcement off.
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Review comments at @main.tf:
- Line 158: Guard private_endpoint_enforcement_enabled against the GKE
prerequisites: when private endpoint enforcement is requested, validate that
Envoy is enabled and the control plane is at least 1.28.10-gke.1058000, or
provide an upgrade path before enabling it. Keep the current null behavior when
enforcement is not requested.
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…d cluster The mock tests only covered the validations, because the cluster_ca_certificate output indexed a master_auth block that mocks cannot produce, so no mocked plan could complete. The output now uses try(), and the CI tests assert what the module renders: the endpoint mode, the managed authorized networks with Google Cloud public access disabled, private-endpoint enforcement, the opt-in path, and the --internal-ip kubectl command. The rendered-cluster runs move out of the credentialed test file. authorized_networks now accepts IPv4 CIDR blocks only, at most 100 entries (the GKE limit), no documentation ranges, and at most one /8 of addresses in total unless allow_public_api_server is set. The new variables are non-nullable. The documentation now states that the private endpoint is reachable in-region from the VPC network and that the list restricts it only in private-endpoint mode. BREAKING CHANGE: authorized_networks rejects IPv6 entries, more than 100 entries, documentation ranges such as 203.0.113.0/24, and lists that cover more than one /8 in total unless allow_public_api_server is set.
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Inline comments:
Review comments at @README.md:
- Line 177: Update the upgrade guidance for gcp_public_cidrs_access_enabled to
warn that disabling it may not immediately restrict previously allowed Google
Cloud external IPs because firewall changes can take several hours to propagate.
Tell operators to verify effective access before treating the endpoint as
restricted.
Review comments at @variables.tf:
- Line 162: Update the description for allow_public_api_server and its matching
statement in README.md to say that requests require Kubernetes API
authentication and authorization, not specifically Google authentication. Keep
the existing explanation of public endpoint exposure and authorized_networks
behavior unchanged.
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GKE can take several hours to enforce disabled Google Cloud public IP access, so the upgrade note asks operators to verify effective access. Requests are authenticated by the Kubernetes API (including ServiceAccount tokens), not only by Google identities, so the wording now says so.
The documentation-range guard only checked entries of /24 or narrower, so a broader range that contains a documentation range passed. Entries inside a documentation range are now always rejected, and broader entries that contain one need allow_public_api_server, so an explicit 0.0.0.0/0 under the opt-in still works.
Kubernetes serves /healthz, /livez, /readyz and /version without authentication, so the opt-in description and README now say that other requests still need Kubernetes API authentication and authorization.
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In private-endpoint mode authorized_networks restricts the private endpoint and holds internal ranges, so a list with all three RFC 1918 ranges was rejected unless allow_public_api_server was set, and that opt-in stayed set if private mode was later turned off. The one-/8 total now applies only while the public endpoint is enabled. The per-entry IPv4 and documentation-range checks apply in both modes. Tests cover the RFC 1918 list in private mode (accepted) and in public mode (rejected).
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The example is meant to be copied and used on its own, so it pins superlinked/sie/google from the Terraform Registry again instead of a local path. Before the release-please setup, each release commit bumped this pin to the version being released. release-please keeps doing that through extra-files: the version line carries an x-release-please-version marker, so the release pull request sets it to the new module version and every tag names its own release. CI still validates the example against the module code in the pull request. A workflow step rewrites the checked-out example to source "../.." and drops the marked version line before init and validate. The rewrite is never committed, and the step fails if it did not apply. A Terraform override file cannot do this, because it cannot remove the version argument, and a version constraint is rejected for a local module path.
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Summary
This change decides who can reach the GKE Kubernetes API. It needs a security review before merge.
The module hardcoded
private_cluster_config.enable_private_endpoint = false. It renderedmaster_authorized_networks_configonly whenauthorized_networkswas non-empty, andauthorized_networksdefaults to[]. A cluster built with the defaults therefore served the control plane on a public IP with no network restriction.Change
The module never leaves the control plane open to every address unless the operator opts in. The plan fails until one of three modes is chosen:
authorized_networks(existing)[]enable_private_endpoint(new)falseenable_private_nodes.allow_public_api_server(new)falseauthorized_networksthe module leaves master authorized networks unmanaged, as before.Behaviour:
master_authorized_networks_configis always rendered except under the explicit opt-in with no networks, so an empty list admits no external address instead of every address. It setsgcp_public_cidrs_access_enabled = false, so public IP addresses of any Google Cloud customer are not admitted implicitly.authorized_networksalso setsprivate_endpoint_enforcement_enabled = true, which needs GKE1.28.10-gke.1058000or later with Envoy enabled. Otherwise the attribute is left unmanaged, so the module never turns existing enforcement off.kubectl_config_commandadds--internal-ipin private-endpoint mode.Validations on
authorized_networks:/8) unlessallow_public_api_serveris set. This rejects0.0.0.0/0, split halves, and many broad ranges alike. In private-endpoint mode the list holds internal ranges for the private endpoint and has no total limit, so all three RFC 1918 ranges are accepted without the opt-in.192.0.2.0/24,198.51.100.0/24,203.0.113.0/24) are always rejected, so an unedited README placeholder fails at plan time. Broader entries that contain one need the opt-in.The existing
authorized_networksname and object shape (withdisplay_name) are kept. The new variables are non-nullable. Both the endpoint mode and the authorized networks are updated in place by the provider, through the control-plane endpoints update, so no mode change replaces the cluster. The DNS-based control-plane endpoint is not enabled by this module.Documented flow
This module installs nothing into the cluster, so
terraform applyworks in every mode, and correctingauthorized_networksrestores access after a lockout.examples/dev-l4-spotnow requiresapi_server_authorized_ip_ranges, which it maps toauthorized_networks. The README placeholder is a documentation range and is rejected if copied unchanged. The example keeps its Registry source (source = "superlinked/sie/google"), so it can be copied and used on its own. The released 0.7.x module does not accept the new inputs, so the pinnedversionline carries anx-release-please-versionmarker, andrelease-please-config.jsonlists the example underextra-files. The release pull request for this change sets the pin to the new module version, as the release commits up to 0.7.2 did, so each tag's example names that tag's release. CI validates the example against the module code in this pull request: a workflow step rewrites the checked-out file tosource = "../.."and drops the marked version line before init and validate. The rewrite is never committed. An override file cannot do this, because it cannot removeversion, which Terraform rejects on a local path.Service exposure is not changed here. The chart keeps its gateway and config Services as
ClusterIP, and superlinked/sie#393 turns off the preset Ingress and requires authentication and TLS for gateway exposure.Upgrade notes
Released as a breaking change.
authorized_networksalready set: no action if the entries are IPv4, outside the documentation ranges, at most 100, and no broader than one/8in total. Otherwise setallow_public_api_server = true.terraform planshowsgcp_public_cidrs_access_enabled = falseonly if it had been enabled outside Terraform.authorized_networksempty: the plan fails with a message listing the three modes. Then:authorized_networks.terraform planshows an in-place update addingmaster_authorized_networks_config.enable_private_endpoint = true.terraform planshows an in-place update ofprivate_cluster_config.enable_private_endpoint.allow_public_api_server = true.terraform planshows no change to the endpoint.Tests
tests/api_access.tftest.hclruns in CI with mock providers only (20 runs).0.0.0.0/0, a split/1pair, two/8blocks,::/0,::/16, a non-CIDR entry, the documentation placeholder (also under the opt-in), a range containing a documentation range, 101 entries, a private endpoint without private nodes, and the three RFC 1918 ranges on the public endpoint./8in total; private mode with an empty list and--internal-ip; enforcement on the private endpoint when networks are listed; all three RFC 1918 ranges accepted in private-endpoint mode without the opt-in; the opt-in leaving authorized networks unmanaged; and the opt-in accepting0.0.0.0/0.cluster_ca_certificateoutput now usestry(), so mocked plans complete; without it no mocked plan could evaluate the outputs.enable_private_endpoint = false, droppinggcp_public_cidrs_access_enabled, restoring the previousfor_each, dropping enforcement, dropping--internal-ip, or weakening any validation each makes a test fail.terraform fmt -check -recursive,tflint,terraform validatefor the module and the example, and the mock tests (20 passed).Security review
This changes a trust boundary: who can reach the Kubernetes control plane. It requests an independent security review before merge. Points worth checking: the condition that omits the authorized-networks block, the aggregate rule, and the in-place update path on existing clusters.
Summary by CodeRabbit
kubectlcommands use the internal IP when private-endpoint mode is enabled.nullif the certificate cannot be accessed.