Report error for unsupported PKCS #1 format for the private key (#4117)

Java Kafka clients don't support PKCS #1 format for private keys.

Signed-off-by: Pierangelo Di Pilato <[email protected]>
Co-authored-by: Pierangelo Di Pilato <[email protected]>

control-plane/pkg/security/secret.go

@@ -19,8 +19,10 @@ package security
 import (
 	"crypto/tls"
 	"crypto/x509"
+	"encoding/pem"
 	"fmt"
 	"strconv"
+	"strings"
 
 	"github.com/IBM/sarama"
 
@@ -193,6 +195,10 @@ func sslConfig(protocol string, data map[string][]byte) kafka.ConfigOption {
 				if err != nil {
 					return fmt.Errorf("[protocol %s] failed to load x.509 key pair: %w", protocol, err)
 				}
+				// Java Kafka clients don't support PKCS #1 format for the private key
+				if isPrivateKeyPKCS1Format(userKeyCert) {
+					return fmt.Errorf("[protocol %s] unsupported user key format in %s, 'PKCS #1' format is not supported, convert private key to 'PKCS #8'", protocol, UserKey)
+				}
 				tlsCerts = []tls.Certificate{tlsCert}
 			}
 		}
@@ -220,3 +226,19 @@ func skipClientAuthCheck(data map[string][]byte) (bool, error) {
 	}
 	return enabled, nil
 }
+
+func isPrivateKeyPKCS1Format(keyPEMBlock []byte) bool {
+	var keyDERBlock *pem.Block
+	for {
+		keyDERBlock, keyPEMBlock = pem.Decode(keyPEMBlock)
+		if keyDERBlock == nil {
+			return false
+		}
+		if keyDERBlock.Type == "PRIVATE KEY" || strings.HasSuffix(keyDERBlock.Type, " PRIVATE KEY") {
+			break
+		}
+	}
+
+	_, err := x509.ParsePKCS1PrivateKey(keyDERBlock.Bytes)
+	return err == nil
+}

control-plane/pkg/security/secret_test.go

@@ -194,6 +194,22 @@ func TestSSL(t *testing.T) {
 	assert.NotNil(t, config.Net.TLS.Config.RootCAs)
 }
 
+func TestSSLPKCS1(t *testing.T) {
+	ca, userKey, userCert := loadPKCS1Certs(t)
+
+	secret := map[string][]byte{
+		"protocol": []byte("SSL"),
+		"user.key": userKey,
+		"user.crt": userCert,
+		"ca.crt":   ca,
+	}
+	config := sarama.NewConfig()
+
+	err := kafka.Options(config, secretData(secret))
+
+	assert.NotNil(t, err)
+}
+
 func TestSSLNoUserKey(t *testing.T) {
 	ca, _, userCert := loadCerts(t)
 
@@ -384,3 +400,16 @@ func loadCerts(t *testing.T) (ca, userKey, userCert []byte) {
 
 	return ca, userKey, userCert
 }
+
+func loadPKCS1Certs(t *testing.T) (ca, userKey, userCert []byte) {
+	ca, err := os.ReadFile("testdata/ca.crt")
+	assert.Nil(t, err)
+
+	userKey, err = os.ReadFile("testdata/pkcs1_user.key")
+	assert.Nil(t, err)
+
+	userCert, err = os.ReadFile("testdata/user.crt")
+	assert.Nil(t, err)
+
+	return ca, userKey, userCert
+}

control-plane/pkg/security/testdata/pkcs1_user.key

@@ -0,0 +1,27 @@
+-----BEGIN RSA PRIVATE KEY-----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+-----END RSA PRIVATE KEY-----