k8s: Validate API server excluded admission plugins

This patch verifies if CIS Kubernetes Benchmark v1.3.0 section
regarding master node configuration is satisfied (1.1.10).

However, CIS Kubernetes Benchmark v1.3.0 mismatches official
documentation: Kubernetes 1.10+ already provides safe defaults from
security standpoint [1] (ONAP Casablanca uses 1.11).

Deprecated admission control plugin flag has also been validated since
it was still available in Kubernetes provided by Rancher [2].

[1] https://kubernetes.io/docs/reference/access-authn-authz/admission-controllers/#is-there-a-recommended-set-of-admission-controllers-to-use
[2] https://github.com/rancher/rancher/issues/15064

Issue-ID: SECCOM-235
Change-Id: I0e8fe9f885861f155cb8265df085fa93dbdff6d2
Signed-off-by: Pawel Wieczorek <p.wieczorek2@samsung.com>

3 files changed, 53 insertions, 0 deletions

diff --git a/test/security/k8s/src/check/cmd/check/check.go b/test/security/k8s/src/check/cmd/check/check.go
index 3c005f77c..2ea180628 100644
--- a/test/security/k8s/src/check/cmd/check/check.go
+++ b/test/security/k8s/src/check/cmd/check/check.go
@@ -51,4 +51,6 @@ func main() {
 	log.Printf("IsKubeletHTTPSAbsentOrEnabled: %t\n", master.IsKubeletHTTPSAbsentOrEnabled(k8sParams))
 	log.Printf("IsInsecureBindAddressAbsentOrLoopback: %t\n", master.IsInsecureBindAddressAbsentOrLoopback(k8sParams))
 	log.Printf("IsSecurePortAbsentOrValid: %t\n", master.IsSecurePortAbsentOrValid(k8sParams))
+
+	log.Printf("IsAlwaysAdmitAdmissionControlPluginExcluded: %t\n", master.IsAlwaysAdmitAdmissionControlPluginExcluded(k8sParams))
 }
diff --git a/test/security/k8s/src/check/validators/master/api.go b/test/security/k8s/src/check/validators/master/api.go
index c91b77e30..58064ef10 100644
--- a/test/security/k8s/src/check/validators/master/api.go
+++ b/test/security/k8s/src/check/validators/master/api.go
@@ -126,3 +126,39 @@ func hasFlagValidPort(flag string, params []string) bool {
 	}
 	return true
 }
+
+// IsAlwaysAdmitAdmissionControlPluginExcluded validates AlwaysAdmit is excluded from admission control plugins.
+func IsAlwaysAdmitAdmissionControlPluginExcluded(params []string) bool {
+	if isSingleFlagPresent("--enable-admission-plugins=", params) {
+		return !hasFlagArgumentIncluded("--enable-admission-plugins=", "AlwaysAdmit", params)
+	}
+	if isSingleFlagPresent("--admission-control=", params) {
+		return !hasFlagArgumentIncluded("--admission-control=", "AlwaysAdmit", params)
+	}
+	return false
+}
+
+// isSingleFlagPresent checks presence of selected flag and whether it was used once.
+func isSingleFlagPresent(flag string, params []string) bool {
+	found := filterFlags(params, flag)
+	if len(found) != 1 {
+		return false
+	}
+	return true
+}
+
+// hasFlagArgumentIncluded checks whether selected flag includes requested argument.
+func hasFlagArgumentIncluded(flag string, argument string, params []string) bool {
+	found := filterFlags(params, flag)
+	if len(found) != 1 {
+		return false
+	}
+
+	_, values := splitKV(found[0], "=")
+	for _, v := range strings.Split(values, ",") {
+		if v == argument {
+			return true
+		}
+	}
+	return false
+}
diff --git a/test/security/k8s/src/check/validators/master/api_test.go b/test/security/k8s/src/check/validators/master/api_test.go
index bee199519..f7c6daa52 100644
--- a/test/security/k8s/src/check/validators/master/api_test.go
+++ b/test/security/k8s/src/check/validators/master/api_test.go
@@ -18,6 +18,10 @@ var _ = Describe("Api", func() {
 			"--profiling=false",
 			"--repair-malformed-updates=false",
 			"--service-account-lookup=true",
+			"--enable-admission-plugins=NamespaceLifecycle,LimitRanger,ServiceAccount," +
+				"TaintNodesByCondition,Priority,DefaultTolerationSeconds,DefaultStorageClass," +
+				"PersistentVolumeClaimResize,MutatingAdmissionWebhook,ValidatingAdmissionWebhook," +
+				"ResourceQuota",
 		}
 
 		// kubeApiServerCasablanca was obtained from virtual environment for testing
@@ -212,5 +216,16 @@ var _ = Describe("Api", func() {
 			Entry("Should be set to true on CIS-compliant cluster", kubeApiServerCISCompliant, true),
 			Entry("Should be set to true on Dublin cluster", kubeApiServerDublin, true),
 		)
+
+		DescribeTable("AlwaysAdmit admission control plugin",
+			func(params []string, expected bool) {
+				Expect(IsAlwaysAdmitAdmissionControlPluginExcluded(params)).To(Equal(expected))
+			},
+			Entry("Is not absent on insecure cluster", []string{"--enable-admission-plugins=Foo,Bar,AlwaysAdmit,Baz,Quuz"}, false),
+			Entry("Is not absent on insecure deprecated cluster", []string{"--admission-control=Foo,Bar,AlwaysAdmit,Baz,Quuz"}, false),
+			Entry("Should be absent on CIS-compliant cluster", kubeApiServerCISCompliant, true),
+			Entry("Should be absent on Casablanca cluster", kubeApiServerCasablanca, true),
+			Entry("Should be absent on Dublin cluster", kubeApiServerDublin, true),
+		)
 	})
 })