Fix extensions copy on renew

Fixes #36

authority/tls.go

@@ -30,8 +30,9 @@ type SignOptions struct {
 }
 
 var (
-	stepOIDRoot        = asn1.ObjectIdentifier{1, 3, 6, 1, 4, 1, 37476, 9000, 64}
-	stepOIDProvisioner = append(asn1.ObjectIdentifier(nil), append(stepOIDRoot, 1)...)
+	stepOIDRoot               = asn1.ObjectIdentifier{1, 3, 6, 1, 4, 1, 37476, 9000, 64}
+	stepOIDProvisioner        = append(asn1.ObjectIdentifier(nil), append(stepOIDRoot, 1)...)
+	oidAuthorityKeyIdentifier = asn1.ObjectIdentifier{2, 5, 29, 35}
 )
 
 type stepProvisionerASN1 struct {
@@ -190,8 +191,6 @@ func (a *Authority) Renew(ocx *x509.Certificate) (*x509.Certificate, *x509.Certi
 		NotBefore:                   now,
 		NotAfter:                    now.Add(duration),
 		KeyUsage:                    oldCert.KeyUsage,
-		Extensions:                  oldCert.Extensions,
-		ExtraExtensions:             oldCert.ExtraExtensions,
 		UnhandledCriticalExtensions: oldCert.UnhandledCriticalExtensions,
 		ExtKeyUsage:                 oldCert.ExtKeyUsage,
 		UnknownExtKeyUsage:          oldCert.UnknownExtKeyUsage,
@@ -218,6 +217,15 @@ func (a *Authority) Renew(ocx *x509.Certificate) (*x509.Certificate, *x509.Certi
 		PolicyIdentifiers:           oldCert.PolicyIdentifiers,
 	}
 
+	// Copy all extensions except for Authority Key Identifier. This one might
+	// be different if we rotate the intermediate certificate and it will cause
+	// a TLS bad certificate error.
+	for _, ext := range oldCert.Extensions {
+		if !ext.Id.Equal(oidAuthorityKeyIdentifier) {
+			newCert.ExtraExtensions = append(newCert.ExtraExtensions, ext)
+		}
+	}
+
 	leaf, err := x509util.NewLeafProfileWithTemplate(newCert,
 		issIdentity.Crt, issIdentity.Key)
 	if err != nil {

authority/tls_test.go

@@ -9,6 +9,7 @@ import (
 	"fmt"
 	"net"
 	"net/http"
+	"reflect"
 	"testing"
 	"time"
 
@@ -269,7 +270,8 @@ func TestRenew(t *testing.T) {
 		a.intermediateIdentity.Key,
 		x509util.WithNotBeforeAfterDuration(so.NotBefore, so.NotAfter, 0),
 		withDefaultASN1DN(a.config.AuthorityConfig.Template),
-		x509util.WithPublicKey(pub), x509util.WithHosts("test.smallstep.com,test"))
+		x509util.WithPublicKey(pub), x509util.WithHosts("test.smallstep.com,test"),
+		withProvisionerOID("Max", a.config.AuthorityConfig.Provisioners[0].Key.KeyID))
 	assert.FatalError(t, err)
 	crtBytes, err := leaf.CreateCertificate()
 	assert.FatalError(t, err)
@@ -390,6 +392,20 @@ func TestRenew(t *testing.T) {
 					realIntermediate, err := x509.ParseCertificate(a.intermediateIdentity.Crt.Raw)
 					assert.FatalError(t, err)
 					assert.Equals(t, intermediate, realIntermediate)
+
+					// Compare extensions: they can be in a different order
+					for _, ext1 := range crt.Extensions {
+						found := false
+						for _, ext2 := range leaf.Extensions {
+							if reflect.DeepEqual(ext1, ext2) {
+								found = true
+								break
+							}
+						}
+						if !found {
+							t.Errorf("x509 extension %s not found in renewed certificate", ext1.Id.String())
+						}
+					}
 				}
 			}
 		})