Merge pull request kubernetes#86705 from neolit123/1.18-fix-ca-whitespace-comparison

kubeadm: tolerate whitespace when validating user CA PEMs

Author: k8s-ci-robot

cmd/kubeadm/app/phases/kubeconfig/kubeconfig.go

@@ -235,8 +235,14 @@ func validateKubeConfig(outDir, filename string, config *clientcmdapi.Config) er
 		return errors.Errorf("failed to find the given CurrentContext Cluster in Clusters of the kubeconfig file %s", kubeConfigFilePath)
 	}
 
+	// Make sure the compared CAs are whitespace-trimmed. The function clientcmd.LoadFromFile() just decodes
+	// the base64 CA and places it raw in the v1.Config object. In case the user has extra whitespace
+	// in the CA they used to create a kubeconfig this comparison to a generated v1.Config will otherwise fail.
+	caCurrent := bytes.TrimSpace(currentConfig.Clusters[currentCluster].CertificateAuthorityData)
+	caExpected := bytes.TrimSpace(config.Clusters[expectedCluster].CertificateAuthorityData)
+
 	// If the current CA cert on disk doesn't match the expected CA cert, error out because we have a file, but it's stale
-	if !bytes.Equal(currentConfig.Clusters[currentCluster].CertificateAuthorityData, config.Clusters[expectedCluster].CertificateAuthorityData) {
+	if !bytes.Equal(caCurrent, caExpected) {
 		return errors.Errorf("a kubeconfig file %q exists already but has got the wrong CA cert", kubeConfigFilePath)
 	}
 	// If the current API Server location on disk doesn't match the expected API server, error out because we have a file, but it's stale

cmd/kubeadm/app/phases/kubeconfig/kubeconfig_test.go

@@ -469,6 +469,14 @@ func TestValidateKubeConfig(t *testing.T) {
 	configWithAnotherClusterCa := setupdKubeConfigWithClientAuth(t, anotherCaCert, anotherCaKey, "https://1.2.3.4:1234", "test-cluster", "myOrg1")
 	configWithAnotherServerURL := setupdKubeConfigWithClientAuth(t, caCert, caKey, "https://4.3.2.1:4321", "test-cluster", "myOrg1")
 
+	// create a valid config but with whitespace around the CA PEM.
+	// validateKubeConfig() should tollerate that.
+	configWhitespace := config.DeepCopy()
+	configWhitespaceCtx := configWhitespace.Contexts[configWhitespace.CurrentContext]
+	configWhitespaceCA := string(configWhitespace.Clusters[configWhitespaceCtx.Cluster].CertificateAuthorityData)
+	configWhitespaceCA = "\n" + configWhitespaceCA + "\n"
+	configWhitespace.Clusters[configWhitespaceCtx.Cluster].CertificateAuthorityData = []byte(configWhitespaceCA)
+
 	tests := map[string]struct {
 		existingKubeConfig *clientcmdapi.Config
 		kubeConfig         *clientcmdapi.Config
@@ -493,6 +501,11 @@ func TestValidateKubeConfig(t *testing.T) {
 			kubeConfig:         config,
 			expectedError:      false,
 		},
+		"kubeconfig exist and is valid even if its CA contains whitespace": {
+			existingKubeConfig: configWhitespace,
+			kubeConfig:         config,
+			expectedError:      false,
+		},
 	}
 
 	for name, test := range tests {