Allow PKCS#8 private keys in .pem files (sideshow#101)

* Allow PKCS#8 private keys in .pem files

* Fix tests and test new behavior

certificate/_fixtures/certificate-valid-pkcs8.pem

@@ -0,0 +1,60 @@
+Bag Attributes
+    localKeyID: 8C 1A 9F 00 66 BD 24 42 B9 5D 1E EB FE 5E 8B CA 04 3D 73 83 
+    friendlyName: APNS/2 Private Key
+subject=/C=NZ/ST=Wellington/L=Wellington/O=Internet Widgits Pty Ltd/OU=9ZEH62KRVV/CN=APNS/2 Development IOS Push Services: com.sideshow.Apns2
+issuer=/C=NZ/ST=Wellington/L=Wellington/O=APNS/2 Inc./OU=APNS/2 Worldwide Developer Relations/CN=APNS/2 Worldwide Developer Relations Certification Authority
+-----BEGIN CERTIFICATE-----
+MIID6zCCAtMCAQIwDQYJKoZIhvcNAQELBQAwgcMxCzAJBgNVBAYTAk5aMRMwEQYD
+VQQIEwpXZWxsaW5ndG9uMRMwEQYDVQQHEwpXZWxsaW5ndG9uMRQwEgYDVQQKEwtB
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+mYO5mJkIobUa4+ZJhCPKEdmgpFbRGk0wVuaDM9Cv6P2srsYAjaO4y3VP0GvNKRI=
+-----END CERTIFICATE-----
+Bag Attributes
+    localKeyID: 8C 1A 9F 00 66 BD 24 42 B9 5D 1E EB FE 5E 8B CA 04 3D 73 83 
+    friendlyName: APNS/2 Private Key
+Key Attributes: <No Attributes>
+-----BEGIN PRIVATE KEY-----
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+mYuNoitP6pDdcAZ0kDXeFyY=
+-----END PRIVATE KEY-----

certificate/certificate.go

@@ -16,11 +16,11 @@ import (
 
 // Possible errors when parsing a certificate.
 var (
-	ErrFailedToDecryptKey           = errors.New("failed to decrypt private key")
-	ErrFailedToParsePKCS1PrivateKey = errors.New("failed to parse PKCS1 private key")
-	ErrFailedToParseCertificate     = errors.New("failed to parse certificate PEM data")
-	ErrNoPrivateKey                 = errors.New("no private key")
-	ErrNoCertificate                = errors.New("no certificate")
+	ErrFailedToDecryptKey       = errors.New("failed to decrypt private key")
+	ErrFailedToParsePrivateKey  = errors.New("failed to parse private key")
+	ErrFailedToParseCertificate = errors.New("failed to parse certificate PEM data")
+	ErrNoPrivateKey             = errors.New("no private key")
+	ErrNoCertificate            = errors.New("no certificate")
 )
 
 // FromP12File loads a PKCS#12 certificate from a local file and returns a
@@ -120,9 +120,14 @@ func unencryptPrivateKey(block *pem.Block, password string) (crypto.PrivateKey,
 }
 
 func parsePrivateKey(bytes []byte) (crypto.PrivateKey, error) {
+	var key crypto.PrivateKey
 	key, err := x509.ParsePKCS1PrivateKey(bytes)
-	if err != nil {
-		return nil, ErrFailedToParsePKCS1PrivateKey
+	if err == nil {
+		return key, nil
+	}
+	key, err = x509.ParsePKCS8PrivateKey(bytes)
+	if err == nil {
+		return key, nil
 	}
-	return key, nil
+	return nil, ErrFailedToParsePrivateKey
 }

certificate/certificate_test.go

@@ -58,6 +58,19 @@ func TestValidCertificateFromPemBytes(t *testing.T) {
 	assert.Nil(t, verifyHostname(cer))
 }
 
+func TestValidCertificateFromPemFileWithPKCS8PrivateKey(t *testing.T) {
+	cer, err := certificate.FromPemFile("_fixtures/certificate-valid-pkcs8.pem", "")
+	assert.NoError(t, err)
+	assert.Nil(t, verifyHostname(cer))
+}
+
+func TestValidCertificateFromPemBytesWithPKCS8PrivateKey(t *testing.T) {
+	bytes, _ := ioutil.ReadFile("_fixtures/certificate-valid-pkcs8.pem")
+	cer, err := certificate.FromPemBytes(bytes, "")
+	assert.NoError(t, err)
+	assert.Nil(t, verifyHostname(cer))
+}
+
 func TestEncryptedValidCertificateFromPemFile(t *testing.T) {
 	cer, err := certificate.FromPemFile("_fixtures/certificate-valid-encrypted.pem", "password")
 	assert.NoError(t, err)
@@ -79,7 +92,7 @@ func TestBadPasswordPemFile(t *testing.T) {
 func TestBadKeyPemFile(t *testing.T) {
 	cer, err := certificate.FromPemFile("_fixtures/certificate-bad-key.pem", "")
 	assert.Equal(t, tls.Certificate{}, cer)
-	assert.Equal(t, certificate.ErrFailedToParsePKCS1PrivateKey, err)
+	assert.Equal(t, certificate.ErrFailedToParsePrivateKey, err)
 }
 
 func TestNoKeyPemFile(t *testing.T) {