add acme package, refactor acme as resuable API

Signed-off-by: Emile Vauge <emile@vauge.com>

acme/crypto.go

@@ -0,0 +1,78 @@
+package acme
+
+import (
+	"crypto/rand"
+	"crypto/rsa"
+	"crypto/sha256"
+	"crypto/tls"
+	"crypto/x509"
+	"crypto/x509/pkix"
+	"encoding/hex"
+	"encoding/pem"
+	"fmt"
+	"math/big"
+	"time"
+)
+
+func generateDefaultCertificate() (*tls.Certificate, error) {
+	rsaPrivKey, err := rsa.GenerateKey(rand.Reader, 2048)
+	if err != nil {
+		return nil, err
+	}
+	rsaPrivPEM := pem.EncodeToMemory(&pem.Block{Type: "RSA PRIVATE KEY", Bytes: x509.MarshalPKCS1PrivateKey(rsaPrivKey)})
+
+	randomBytes := make([]byte, 100)
+	_, err = rand.Read(randomBytes)
+	if err != nil {
+		return nil, err
+	}
+	zBytes := sha256.Sum256(randomBytes)
+	z := hex.EncodeToString(zBytes[:sha256.Size])
+	domain := fmt.Sprintf("%s.%s.traefik.default", z[:32], z[32:])
+	tempCertPEM, err := generatePemCert(rsaPrivKey, domain)
+	if err != nil {
+		return nil, err
+	}
+
+	certificate, err := tls.X509KeyPair(tempCertPEM, rsaPrivPEM)
+	if err != nil {
+		return nil, err
+	}
+
+	return &certificate, nil
+}
+func generatePemCert(privKey *rsa.PrivateKey, domain string) ([]byte, error) {
+	derBytes, err := generateDerCert(privKey, time.Time{}, domain)
+	if err != nil {
+		return nil, err
+	}
+
+	return pem.EncodeToMemory(&pem.Block{Type: "CERTIFICATE", Bytes: derBytes}), nil
+}
+
+func generateDerCert(privKey *rsa.PrivateKey, expiration time.Time, domain string) ([]byte, error) {
+	serialNumberLimit := new(big.Int).Lsh(big.NewInt(1), 128)
+	serialNumber, err := rand.Int(rand.Reader, serialNumberLimit)
+	if err != nil {
+		return nil, err
+	}
+
+	if expiration.IsZero() {
+		expiration = time.Now().Add(365)
+	}
+
+	template := x509.Certificate{
+		SerialNumber: serialNumber,
+		Subject: pkix.Name{
+			CommonName: "TRAEFIK DEFAULT CERT",
+		},
+		NotBefore: time.Now(),
+		NotAfter:  expiration,
+
+		KeyUsage:              x509.KeyUsageKeyEncipherment,
+		BasicConstraintsValid: true,
+		DNSNames:              []string{domain},
+	}
+
+	return x509.CreateCertificate(rand.Reader, &template, &template, &privKey.PublicKey, privKey)
+}