Fix noisy SSL error

Signed-off-by: Bryan Frimin <bryan@getprobo.com>

pkg/certmanager/selector.go

@@ -32,8 +32,15 @@ type (
 		cache         sync.Map
 		encryptionKey cipher.EncryptionKey
 	}
+
+	// NoSNIError is returned when a TLS client doesn't provide SNI (Server Name Indication)
+	NoSNIError struct{}
 )
 
+func (e *NoSNIError) Error() string {
+	return "no SNI provided"
+}
+
 func NewSelector(
 	pg *pg.Client,
 	encryptionKey cipher.EncryptionKey,
@@ -49,7 +56,7 @@ func (s *Selector) GetCertificate(hello *tls.ClientHelloInfo) (*tls.Certificate,
 
 	// Empty domain, return error
 	if domain == "" {
-		return nil, fmt.Errorf("no SNI provided")
+		return nil, &NoSNIError{}
 	}
 
 	if cached, ok := s.cache.Load(domain); ok {

pkg/probod/probod.go

@@ -614,8 +614,18 @@ func (impl *Implm) runTrustCenterServer(
 	)
 
 	httpsServer.TLSConfig = &tls.Config{
-		GetCertificate: certSelector.GetCertificate,
-		MinVersion:     tls.VersionTLS12,
+		GetCertificate: func(hello *tls.ClientHelloInfo) (*tls.Certificate, error) {
+			cert, err := certSelector.GetCertificate(hello)
+			// Silently reject connections without SNI (load balancers, health checks, scanners)
+			if err != nil {
+				var noSNIErr *certmanager.NoSNIError
+				if errors.As(err, &noSNIErr) {
+					return nil, nil
+				}
+			}
+			return cert, err
+		},
+		MinVersion: tls.VersionTLS12,
 		CipherSuites: []uint16{
 			tls.TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384,
 			tls.TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256,