Merge pull request #111783 from SataQiu/fix-kubeadm-20220810

kubeadm: try to load CA cert from external CertificateAuthority file when CertificateAuthorityData is empty for existing kubeconfig

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

@@ -22,6 +22,7 @@ import (
 	"crypto/x509"
 	"fmt"
 	"io"
+	"io/ioutil"
 	"os"
 	"path/filepath"
 	"time"
@@ -238,6 +239,18 @@ func validateKubeConfig(outDir, filename string, config *clientcmdapi.Config) er
 	// 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)
+	if len(caCurrent) == 0 {
+		// fallback to load CA cert data from external CA file
+		clusterCAFilePath := currentConfig.Clusters[currentCluster].CertificateAuthority
+		if len(clusterCAFilePath) > 0 {
+			clusterCABytes, err := ioutil.ReadFile(clusterCAFilePath)
+			if err != nil {
+				klog.Warningf("failed to load CA cert from %q for kubeconfig %q, %v", clusterCAFilePath, kubeConfigFilePath, err)
+			} else {
+				caCurrent = bytes.TrimSpace(clusterCABytes)
+			}
+		}
+	}
 	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

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

@@ -22,6 +22,7 @@ import (
 	"crypto/x509"
 	"fmt"
 	"io"
+	"io/ioutil"
 	"os"
 	"path/filepath"
 	"reflect"
@@ -483,6 +484,25 @@ 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")
 
+	configWithSameClusterCaByExternalFile := config.DeepCopy()
+	currentCtx, exists := configWithSameClusterCaByExternalFile.Contexts[configWithSameClusterCaByExternalFile.CurrentContext]
+	if !exists {
+		t.Fatal("failed to find CurrentContext in Contexts of the kubeconfig")
+	}
+	if configWithSameClusterCaByExternalFile.Clusters[currentCtx.Cluster] == nil {
+		t.Fatal("failed to find the given CurrentContext Cluster in Clusters of the kubeconfig")
+	}
+	tmpfile, err := ioutil.TempFile("", "external-ca.crt")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.Remove(tmpfile.Name())
+	if _, err := tmpfile.Write(pkiutil.EncodeCertPEM(caCert)); err != nil {
+		t.Fatal(err)
+	}
+	configWithSameClusterCaByExternalFile.Clusters[currentCtx.Cluster].CertificateAuthorityData = nil
+	configWithSameClusterCaByExternalFile.Clusters[currentCtx.Cluster].CertificateAuthority = tmpfile.Name()
+
 	// create a valid config but with whitespace around the CA PEM.
 	// validateKubeConfig() should tolerate that.
 	configWhitespace := config.DeepCopy()
@@ -519,6 +539,11 @@ func TestValidateKubeConfig(t *testing.T) {
 			kubeConfig:         config,
 			expectedError:      false,
 		},
+		"kubeconfig exist and is valid even if its CA is provided as an external file": {
+			existingKubeConfig: configWithSameClusterCaByExternalFile,
+			kubeConfig:         config,
+			expectedError:      false,
+		},
 	}
 
 	for name, test := range tests {