use the topic from -apns-cert if specified (#280)

The MDM Certificate should now be uploaded instead of specified in a
flag, but the flag should still work for backwards compatibility.

Closes #260

config/db.go

@@ -5,11 +5,11 @@ import (
 	"context"
 	"crypto/tls"
 	"crypto/x509"
-	"encoding/asn1"
 	"encoding/pem"
 	"fmt"
 
 	"github.com/boltdb/bolt"
+	"github.com/micromdm/micromdm/crypto"
 	"github.com/micromdm/micromdm/pubsub"
 	"github.com/pkg/errors"
 )
@@ -118,21 +118,10 @@ func (db *DB) PushTopic() (string, error) {
 	if err != nil {
 		return "", errors.Wrap(err, "get push certificate for topic")
 	}
-	topic, err := topicFromCert(cert.Leaf)
+	topic, err := crypto.TopicFromCert(cert.Leaf)
 	return topic, errors.Wrap(err, "get topic from push certificate")
 }
 
-func topicFromCert(cert *x509.Certificate) (string, error) {
-	var oidASN1UserID = asn1.ObjectIdentifier{0, 9, 2342, 19200300, 100, 1, 1}
-	for _, v := range cert.Subject.Names {
-		if v.Type.Equal(oidASN1UserID) {
-			return v.Value.(string), nil
-		}
-	}
-
-	return "", errors.New("could not find Push Topic (UserID OID) in certificate")
-}
-
 func isNotFound(err error) bool {
 	if _, ok := err.(*notFound); ok {
 		return true

crypto/helpers.go

@@ -5,6 +5,7 @@ import (
 	"crypto/rsa"
 	"crypto/x509"
 	"crypto/x509/pkix"
+	"encoding/asn1"
 	"encoding/pem"
 	"errors"
 	"io/ioutil"
@@ -114,3 +115,15 @@ func WritePEMRSAKeyFile(key *rsa.PrivateKey, path string) error {
 			Bytes: x509.MarshalPKCS1PrivateKey(key),
 		})
 }
+
+// TopicFromCert extracts the push certificate topic from the provided certificate.
+func TopicFromCert(cert *x509.Certificate) (string, error) {
+	var oidASN1UserID = asn1.ObjectIdentifier{0, 9, 2342, 19200300, 100, 1, 1}
+	for _, v := range cert.Subject.Names {
+		if v.Type.Equal(oidASN1UserID) {
+			return v.Value.(string), nil
+		}
+	}
+
+	return "", errors.New("could not find Push Topic (UserID OID) in certificate")
+}

serve.go

@@ -674,11 +674,23 @@ func (c *config) setupEnrollmentService() {
 		return
 	}
 
+	var topicProvider enroll.TopicProvider
+	if c.pushCert.Certificate != nil {
+		pushTopic, err := crypto.TopicFromCert(c.pushCert.Certificate)
+		if err != nil {
+			c.err = errors.Wrap(err, "get apns topic from certificate")
+			return
+		}
+		topicProvider = staticTopicProvider{topic: pushTopic}
+	} else {
+		topicProvider = c.configDB
+	}
+
 	var SCEPCertificateSubject string
 	// TODO: clean up order of inputs. Maybe pass *SCEPConfig as an arg?
 	// but if you do, the packages are coupled, better not.
 	c.enrollService, c.err = enroll.NewService(
-		c.configDB,
+		topicProvider,
 		c.pubclient,
 		c.scepCACertPath,
 		c.ServerPublicURL+"/scep",
@@ -690,6 +702,13 @@ func (c *config) setupEnrollmentService() {
 	)
 }
 
+// if the apns-cert flags are specified this provider will be used in the enroll service.
+type staticTopicProvider struct{ topic string }
+
+func (p staticTopicProvider) PushTopic() (string, error) {
+	return p.topic, nil
+}
+
 func (c *config) depClient() (dep.Client, error) {
 	if c.err != nil {
 		return nil, c.err