lego/acme/crypto.go
2015-11-18 22:07:54 +01:00

314 lines
8.2 KiB
Go

package acme
import (
"bytes"
"crypto"
"crypto/ecdsa"
"crypto/elliptic"
"crypto/rand"
"crypto/rsa"
"crypto/x509"
"crypto/x509/pkix"
"encoding/base64"
"encoding/binary"
"encoding/pem"
"errors"
"fmt"
"io/ioutil"
"math/big"
"net/http"
"strings"
"time"
"golang.org/x/crypto/ocsp"
"golang.org/x/crypto/sha3"
)
type keyType int
type derCertificateBytes []byte
const (
eckey keyType = iota
rsakey
)
const (
// OCSPGood means that the certificate is valid.
OCSPGood = ocsp.Good
// OCSPRevoked means that the certificate has been deliberately revoked.
OCSPRevoked = ocsp.Revoked
// OCSPUnknown means that the OCSP responder doesn't know about the certificate.
OCSPUnknown = ocsp.Unknown
// OCSPServerFailed means that the OCSP responder failed to process the request.
OCSPServerFailed = ocsp.ServerFailed
)
// GetOCSPForCert takes a PEM encoded cert or cert bundle returning the raw OCSP response,
// the status code of the response and an error, if any.
// This []byte can be passed directly into the OCSPStaple property of a tls.Certificate.
// If the bundle only contains the issued certificate, this function will try
// to get the issuer certificate from the IssuingCertificateURL in the certificate.
func GetOCSPForCert(bundle []byte) ([]byte, int, error) {
certificates, err := parsePEMBundle(bundle)
if err != nil {
return nil, OCSPUnknown, err
}
// We only got one certificate, means we have no issuer certificate - get it.
if len(certificates) == 1 {
// TODO: build fallback. If this fails, check the remaining array entries.
if len(certificates[0].IssuingCertificateURL) == 0 {
return nil, OCSPUnknown, errors.New("no issuing certificate URL")
}
resp, err := http.Get(certificates[0].IssuingCertificateURL[0])
if err != nil {
return nil, OCSPUnknown, err
}
defer resp.Body.Close()
issuerBytes, err := ioutil.ReadAll(resp.Body)
if err != nil {
return nil, OCSPUnknown, err
}
issuerCert, err := x509.ParseCertificate(issuerBytes)
if err != nil {
return nil, OCSPUnknown, err
}
// Insert it into the slice on position 0
// We want it ordered right SRV CRT -> CA
certificates = append(certificates, issuerCert)
}
// We expect the certificate slice to be ordered downwards the chain.
// SRV CRT -> CA. We need to pull the cert and issuer cert out of it,
// which should always be the last two certificates.
issuedCert := certificates[0]
issuerCert := certificates[1]
// Finally kick off the OCSP request.
ocspReq, err := ocsp.CreateRequest(issuedCert, issuerCert, nil)
if err != nil {
return nil, OCSPUnknown, err
}
reader := bytes.NewReader(ocspReq)
req, err := http.Post(issuedCert.OCSPServer[0], "application/ocsp-request", reader)
if err != nil {
return nil, OCSPUnknown, err
}
defer req.Body.Close()
ocspResBytes, err := ioutil.ReadAll(req.Body)
ocspRes, err := ocsp.ParseResponse(ocspResBytes, issuerCert)
if err != nil {
return nil, OCSPUnknown, err
}
if ocspRes.Certificate == nil {
err = ocspRes.CheckSignatureFrom(issuerCert)
if err != nil {
return nil, OCSPUnknown, err
}
}
return ocspResBytes, ocspRes.Status, nil
}
func getKeyAuthorization(token string, key interface{}) (string, error) {
// Generate the Key Authorization for the challenge
jwk := keyAsJWK(key)
if jwk == nil {
return "", errors.New("Could not generate JWK from key.")
}
thumbBytes, err := jwk.Thumbprint(crypto.SHA256)
if err != nil {
return "", err
}
// unpad the base64URL
keyThumb := base64.URLEncoding.EncodeToString(thumbBytes)
index := strings.Index(keyThumb, "=")
if index != -1 {
keyThumb = keyThumb[:index]
}
return token + "." + keyThumb, nil
}
// Derive the shared secret according to acme spec 5.6
func performECDH(priv *ecdsa.PrivateKey, pub *ecdsa.PublicKey, outLen int, label string) []byte {
// Derive Z from the private and public keys according to SEC 1 Ver. 2.0 - 3.3.1
Z, _ := priv.PublicKey.ScalarMult(pub.X, pub.Y, priv.D.Bytes())
if len(Z.Bytes())+len(label)+4 > 384 {
return nil
}
if outLen < 384*(2^32-1) {
return nil
}
// Derive the shared secret key using the ANS X9.63 KDF - SEC 1 Ver. 2.0 - 3.6.1
hasher := sha3.New384()
buffer := make([]byte, outLen)
bufferLen := 0
for i := 0; i < outLen/384; i++ {
hasher.Reset()
// Ki = Hash(Z || Counter || [SharedInfo])
hasher.Write(Z.Bytes())
binary.Write(hasher, binary.BigEndian, i)
hasher.Write([]byte(label))
hash := hasher.Sum(nil)
copied := copy(buffer[bufferLen:], hash)
bufferLen += copied
}
return buffer
}
// parsePEMBundle parses a certificate bundle from top to bottom and returns
// a slice of x509 certificates. This function will error if no certificates are found.
func parsePEMBundle(bundle []byte) ([]*x509.Certificate, error) {
var certificates []*x509.Certificate
remaining := bundle
for len(remaining) != 0 {
certBlock, rem := pem.Decode(remaining)
// Thanks golang for having me do this :[
remaining = rem
if certBlock == nil {
return nil, errors.New("Could not decode certificate.")
}
cert, err := x509.ParseCertificate(certBlock.Bytes)
if err != nil {
return nil, err
}
certificates = append(certificates, cert)
}
if len(certificates) == 0 {
return nil, errors.New("No certificates were found while parsing the bundle.")
}
return certificates, nil
}
func generatePrivateKey(t keyType, keyLength int) (crypto.PrivateKey, error) {
switch t {
case eckey:
return ecdsa.GenerateKey(elliptic.P384(), rand.Reader)
case rsakey:
return rsa.GenerateKey(rand.Reader, keyLength)
}
return nil, fmt.Errorf("Invalid keytype: %d", t)
}
func generateCsr(privateKey *rsa.PrivateKey, domain string, san []string) ([]byte, error) {
template := x509.CertificateRequest{
Subject: pkix.Name{
CommonName: domain,
},
}
if len(san) > 0 {
template.DNSNames = san
}
return x509.CreateCertificateRequest(rand.Reader, &template, privateKey)
}
func pemEncode(data interface{}) []byte {
var pemBlock *pem.Block
switch key := data.(type) {
case *rsa.PrivateKey:
pemBlock = &pem.Block{Type: "RSA PRIVATE KEY", Bytes: x509.MarshalPKCS1PrivateKey(key)}
break
case derCertificateBytes:
pemBlock = &pem.Block{Type: "CERTIFICATE", Bytes: []byte(data.(derCertificateBytes))}
}
return pem.EncodeToMemory(pemBlock)
}
func pemDecode(data []byte) (*pem.Block, error) {
pemBlock, _ := pem.Decode(data)
if pemBlock == nil {
return nil, fmt.Errorf("Pem decode did not yield a valid block. Is the certificate in the right format?")
}
return pemBlock, nil
}
func pemDecodeTox509(pem []byte) (*x509.Certificate, error) {
pemBlock, err := pemDecode(pem)
if pemBlock == nil {
return nil, err
}
return x509.ParseCertificate(pemBlock.Bytes)
}
// GetPEMCertExpiration returns the "NotAfter" date of a PEM encoded certificate.
// The certificate has to be PEM encoded. Any other encodings like DER will fail.
func GetPEMCertExpiration(cert []byte) (time.Time, error) {
pemBlock, err := pemDecode(cert)
if pemBlock == nil {
return time.Time{}, err
}
return getCertExpiration(pemBlock.Bytes)
}
// getCertExpiration returns the "NotAfter" date of a DER encoded certificate.
func getCertExpiration(cert []byte) (time.Time, error) {
pCert, err := x509.ParseCertificate(cert)
if err != nil {
return time.Time{}, err
}
return pCert.NotAfter, 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: "ACME Challenge TEMP",
},
NotBefore: time.Now(),
NotAfter: expiration,
KeyUsage: x509.KeyUsageKeyEncipherment,
BasicConstraintsValid: true,
DNSNames: []string{domain},
}
return x509.CreateCertificate(rand.Reader, &template, &template, &privKey.PublicKey, privKey)
}