Added certificate chains to end-entity certificates (#21)

Author: tsaarni

certificate.go

@@ -104,6 +104,7 @@ const (
 )
 
 // TLSCertificate returns the Certificate as tls.Certificate.
+// Complete certificate chain (up to but not including root) is included for end-entity certificates.
 // A key pair and certificate will be generated at first call of any Certificate functions.
 // Error is not nil if generation fails.
 func (c *Certificate) TLSCertificate() (tls.Certificate, error) {
@@ -149,6 +150,7 @@ func (c *Certificate) PrivateKey() (crypto.Signer, error) {
 }
 
 // PEM returns the Certificate as certificate and private key PEM buffers.
+// Complete certificate chain (up to but not including root) is included for end-entity certificates.
 // A key pair and certificate will be generated at first call of any Certificate functions.
 // Error is not nil if generation fails.
 func (c *Certificate) PEM() (cert []byte, key []byte, err error) {
@@ -157,38 +159,28 @@ func (c *Certificate) PEM() (cert []byte, key []byte, err error) {
 		return
 	}
 
-	var buf bytes.Buffer
-
-	err = pem.Encode(&buf, &pem.Block{
-		Type:  "CERTIFICATE",
-		Bytes: c.GeneratedCert.Certificate[0],
-	})
+	cert, err = encodeToPEMBlocks("CERTIFICATE", c.GeneratedCert.Certificate)
 	if err != nil {
 		return
 	}
-	cert = append(cert, buf.Bytes()...) // Create copy of underlying buf.
-
-	buf.Reset()
 
 	k, err := x509.MarshalPKCS8PrivateKey(c.GeneratedCert.PrivateKey)
 	if err != nil {
 		cert = nil
 		return
 	}
-	err = pem.Encode(&buf, &pem.Block{
-		Type:  "PRIVATE KEY",
-		Bytes: k,
-	})
+
+	key, err = encodeToPEMBlocks("PRIVATE KEY", [][]byte{k})
 	if err != nil {
 		cert = nil
 		return
 	}
-	key = append(key, buf.Bytes()...) // Create copy of underlying buf.
 
 	return
 }
 
 // WritePEM writes the Certificate as certificate and private key PEM files.
+// Complete certificate chain (up to but not including root) is included for end-entity certificates.
 // A key pair and certificate will be generated at first call of any Certificate functions.
 // Error is not nil if generation fails.
 func (c *Certificate) WritePEM(certFile, keyFile string) error {
@@ -357,13 +349,25 @@ func (c *Certificate) Generate() error {
 
 	var issuerCert *x509.Certificate
 	var issuerKey crypto.Signer
+	var chain [][]byte
 	if c.Issuer != nil {
 		issuerCert, err = x509.ParseCertificate(c.Issuer.GeneratedCert.Certificate[0])
 		if err != nil {
 			return nil
 		}
 		issuerKey = c.Issuer.GeneratedCert.PrivateKey.(crypto.Signer)
 
+		// Add certificate chain to end-entity certificates.
+		if !*c.IsCA {
+			issuer := c.Issuer
+			for issuer != nil {
+				// Add issuer to chain unless it is root certificate.
+				if issuer.Issuer != nil {
+					chain = append(chain, issuer.GeneratedCert.Certificate[0])
+				}
+				issuer = issuer.Issuer
+			}
+		}
 	} else {
 		// create self-signed certificate
 		issuerCert = template
@@ -377,9 +381,26 @@ func (c *Certificate) Generate() error {
 	}
 
 	c.GeneratedCert = &tls.Certificate{
-		Certificate: [][]byte{cert},
+		Certificate: append([][]byte{cert}, chain...),
 		PrivateKey:  key,
 	}
 
 	return nil
 }
+
+func encodeToPEMBlocks(blockType string, blocks [][]byte) ([]byte, error) {
+	var buf bytes.Buffer
+
+	for _, b := range blocks {
+		err := pem.Encode(&buf, &pem.Block{
+			Type:  blockType,
+			Bytes: b,
+		})
+		if err != nil {
+			return nil, err
+		}
+
+	}
+
+	return buf.Bytes(), nil
+}

certificate_test.go

@@ -349,3 +349,56 @@ func TestSerial(t *testing.T) {
 	assert.Nil(t, err)
 	assert.NotEqual(t, got1.SerialNumber, got2.SerialNumber)
 }
+
+func TestCertificateChain(t *testing.T) {
+	isCA := true
+	rootCA := Certificate{Subject: "CN=ca"}
+	subCA1 := Certificate{Subject: "CN=sub-ca-1", Issuer: &rootCA, IsCA: &isCA}
+	subCA2 := Certificate{Subject: "CN=sub-ca-2", Issuer: &subCA1, IsCA: &isCA}
+	endEntity := Certificate{Subject: "CN=end-entity", Issuer: &subCA2}
+
+	// End-entity certificates have certificate chains appended.
+	got, err := endEntity.TLSCertificate()
+	assert.Nil(t, err)
+	assert.Equal(t, 3, len(got.Certificate))
+	assert.Equal(t, endEntity.GeneratedCert.Certificate[0], got.Certificate[0])
+	assert.Equal(t, subCA2.GeneratedCert.Certificate[0], got.Certificate[1])
+	assert.Equal(t, subCA1.GeneratedCert.Certificate[0], got.Certificate[2])
+
+	// CA certificates do not have chains appended.
+	got, err = subCA2.TLSCertificate()
+	assert.Nil(t, err)
+	assert.Equal(t, 1, len(got.Certificate))
+}
+
+func TestCertificateChainInPEM(t *testing.T) {
+	isCA := true
+	rootCA := Certificate{Subject: "CN=ca"}
+	subCA1 := Certificate{Subject: "CN=sub-ca-1", Issuer: &rootCA, IsCA: &isCA}
+	subCA2 := Certificate{Subject: "CN=sub-ca-2", Issuer: &subCA1, IsCA: &isCA}
+	endEntity := Certificate{Subject: "CN=end-entity", Issuer: &subCA2}
+
+	// End-entity certificates have certificate chains appended.
+	got, _, err := endEntity.PEM()
+	assert.Nil(t, err)
+
+	block, rest := pem.Decode(got)
+	assert.NotNil(t, block)
+	cert, err := x509.ParseCertificate(block.Bytes)
+	assert.Nil(t, err)
+	assert.Equal(t, "CN=end-entity", cert.Subject.String())
+
+	block, rest = pem.Decode(rest)
+	assert.NotNil(t, block)
+	cert, err = x509.ParseCertificate(block.Bytes)
+	assert.Nil(t, err)
+	assert.Equal(t, "CN=sub-ca-2", cert.Subject.String())
+
+	block, rest = pem.Decode(rest)
+	assert.NotNil(t, block)
+	cert, err = x509.ParseCertificate(block.Bytes)
+	assert.Nil(t, err)
+	assert.Equal(t, "CN=sub-ca-1", cert.Subject.String())
+
+	assert.Empty(t, rest)
+}