roachtest/cdc: fix cdc/kafka-auth

From [kafka
2.0](https://kafka.apache.org/20/documentation.html#security_confighostname)
onwards, host name verification of servers is enabled by default.

Previously, the self-signed test certificate we generated for kafka-auth only
included “localhost” in the list of subject alternative names. However, kafka
appears to make internal connections using the fully qualified domain name. As a
result, some inter-broker communication has been failing with a hostname
verification error for some time. But the failure wasn’t raised to the user
until the sarama upgrade happened. This patch fixes the failure by adding the
proper hostname of the kafka node to the certificate.

We don’t believe this represents a meaningful customer-facing issue. The
misconfiguration of the test kafka cluster would have surfaced even with older
sarama versions if the test had involved more than just connecting to the kafka
cluster.

Fixes: #118525
Release note: none

Author: wenyihu6

pkg/cmd/roachtest/tests/cdc.go

@@ -1698,7 +1698,7 @@ func (t *testCerts) CACertBase64() string {
 	return base64.StdEncoding.EncodeToString([]byte(t.CACert))
 }
 
-func makeTestCerts(sinkNodeIP string) (*testCerts, error) {
+func makeTestCerts(sinkNodeIP string, dnsNames ...string) (*testCerts, error) {
 	CAKey, err := rsa.GenerateKey(cryptorand.Reader, keyLength)
 	if err != nil {
 		return nil, errors.Wrap(err, "CA private key")
@@ -1714,7 +1714,7 @@ func makeTestCerts(sinkNodeIP string) (*testCerts, error) {
 		return nil, errors.Wrap(err, "CA cert gen")
 	}
 
-	SinkCert, err := generateSinkCert(sinkNodeIP, SinkKey, CACertSpec, CAKey)
+	SinkCert, err := generateSinkCert(sinkNodeIP, SinkKey, CACertSpec, CAKey, dnsNames...)
 	if err != nil {
 		return nil, errors.Wrap(err, "kafka cert gen")
 	}
@@ -1748,7 +1748,11 @@ func makeTestCerts(sinkNodeIP string) (*testCerts, error) {
 }
 
 func generateSinkCert(
-	sinkIP string, priv *rsa.PrivateKey, CACert *x509.Certificate, CAKey *rsa.PrivateKey,
+	sinkIP string,
+	priv *rsa.PrivateKey,
+	CACert *x509.Certificate,
+	CAKey *rsa.PrivateKey,
+	dnsNames ...string,
 ) ([]byte, error) {
 	ip := net.ParseIP(sinkIP)
 	if ip == nil {
@@ -1772,10 +1776,9 @@ func generateSinkCert(
 		NotAfter:    timeutil.Now().Add(certLifetime),
 		KeyUsage:    x509.KeyUsageKeyEncipherment | x509.KeyUsageDataEncipherment | x509.KeyUsageDigitalSignature | x509.KeyUsageKeyAgreement,
 		ExtKeyUsage: []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth, x509.ExtKeyUsageClientAuth},
-		DNSNames:    []string{"localhost"},
+		DNSNames:    append([]string{"localhost"}, dnsNames...),
 		IPAddresses: []net.IP{ip},
 	}
-
 	return x509.CreateCertificate(cryptorand.Reader, certSpec, CACert, &priv.PublicKey, CAKey)
 }
 
@@ -2347,7 +2350,13 @@ func (k kafkaManager) configureAuth(ctx context.Context) *testCerts {
 	}
 	kafkaIP := ips[0]
 
-	testCerts, err := makeTestCerts(kafkaIP)
+	details, err := k.c.RunWithDetailsSingleNode(ctx, k.t.L(), option.WithNodes(k.kafkaSinkNode), "hostname", "-f")
+	if err != nil {
+		k.t.Fatal(err)
+	}
+	hostname := strings.TrimSpace(details.Stdout)
+	k.t.L().Printf("hostname included in TLS certificates: %s", hostname)
+	testCerts, err := makeTestCerts(kafkaIP, hostname)
 	if err != nil {
 		k.t.Fatal(err)
 	}