Add a certificate error handler

This is used in two different Submariner binaries (the gateway agent
and route agent) and will be used in Lighthouse.

Signed-off-by: Stephen Kitt <skitt@redhat.com>

pkg/util/helpers.go

@@ -19,14 +19,18 @@ limitations under the License.
 package util
 
 import (
+	"crypto/x509"
 	"fmt"
+	"sync/atomic"
 
 	"github.com/pkg/errors"
+	"github.com/submariner-io/admiral/pkg/resource"
 	resourceUtil "github.com/submariner-io/admiral/pkg/resource"
 	"k8s.io/apimachinery/pkg/api/meta"
 	"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
 	"k8s.io/apimachinery/pkg/runtime"
 	"k8s.io/apimachinery/pkg/runtime/schema"
+	utilruntime "k8s.io/apimachinery/pkg/util/runtime"
 	"k8s.io/client-go/discovery"
 	"k8s.io/client-go/rest"
 	"k8s.io/client-go/restmapper"
@@ -39,6 +43,8 @@ const (
 	StatusField      = "status"
 )
 
+var lastBadCertificate atomic.Value
+
 func BuildRestMapper(restConfig *rest.Config) (meta.RESTMapper, error) {
 	discoveryClient, err := discovery.NewDiscoveryClientForConfig(restConfig)
 	if err != nil {
@@ -131,3 +137,23 @@ func CopyImmutableMetadata(from, to *unstructured.Unstructured) *unstructured.Un
 
 	return to
 }
+
+func AddCertificateErrorHandler(fatal bool) {
+	var logCertificateError = logger.Errorf
+	if fatal {
+		logCertificateError = logger.FatalfOnError
+	}
+
+	//nolint:reassign // We need to reassign ErrorHandlers to register our handler
+	utilruntime.ErrorHandlers = append(utilruntime.ErrorHandlers, func(err error) {
+		var unknownAuthorityError x509.UnknownAuthorityError
+		if errors.As(err, &unknownAuthorityError) && lastBadCertificate.Swap(unknownAuthorityError.Cert) != unknownAuthorityError.Cert {
+			logCertificateError(err, "Certificate error: %s", resource.ToJSON(err))
+		}
+		var certificateInvalidError x509.CertificateInvalidError
+		if errors.As(err, &certificateInvalidError) && lastBadCertificate.Swap(certificateInvalidError.Cert) != certificateInvalidError.Cert {
+			logCertificateError(err, "Certificate error: %s", resource.ToJSON(err))
+		}
+		// The generic handler has already logged the error, no need to repeat if we don't want extra detail
+	})
+}