lego/acme/crypto.go

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package acme
import (
"bytes"
"crypto"
"crypto/ecdsa"
"crypto/elliptic"
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"crypto/rand"
"crypto/rsa"
"crypto/x509"
"crypto/x509/pkix"
"encoding/base64"
"encoding/binary"
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"encoding/pem"
"errors"
"fmt"
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"io"
"io/ioutil"
"math/big"
"net/http"
"strings"
"time"
"golang.org/x/crypto/ocsp"
"golang.org/x/crypto/sha3"
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)
// KeyType represents the key algo as well as the key size or curve to use.
type KeyType string
type derCertificateBytes []byte
const (
EC256 = KeyType("P256")
EC384 = KeyType("P348")
RSA2048 = KeyType("2048")
RSA4096 = KeyType("4096")
RSA8192 = KeyType("8192")
)
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 parsed response, and an error, if any. The returned []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. If the []byte and/or ocsp.Response return
// values are nil, the OCSP status may be assumed OCSPUnknown.
func GetOCSPForCert(bundle []byte) ([]byte, *ocsp.Response, error) {
certificates, err := parsePEMBundle(bundle)
if err != nil {
return nil, nil, err
}
// We expect the certificate slice to be ordered downwards the chain.
// SRV CRT -> CA. We need to pull the leaf and issuer certs out of it,
// which should always be the first two certificates. If there's no
// OCSP server listed in the leaf cert, there's nothing to do. And if
// we have only one certificate so far, we need to get the issuer cert.
issuedCert := certificates[0]
if len(issuedCert.OCSPServer) == 0 {
return nil, nil, errors.New("no OCSP server specified in cert")
}
if len(certificates) == 1 {
// TODO: build fallback. If this fails, check the remaining array entries.
if len(issuedCert.IssuingCertificateURL) == 0 {
return nil, nil, errors.New("no issuing certificate URL")
}
resp, err := httpGet(issuedCert.IssuingCertificateURL[0])
if err != nil {
return nil, nil, err
}
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defer resp.Body.Close()
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issuerBytes, err := ioutil.ReadAll(limitReader(resp.Body, 1024*1024))
if err != nil {
return nil, nil, err
}
issuerCert, err := x509.ParseCertificate(issuerBytes)
if err != nil {
return nil, nil, err
}
// Insert it into the slice on position 0
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// We want it ordered right SRV CRT -> CA
certificates = append(certificates, issuerCert)
}
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issuerCert := certificates[1]
// Finally kick off the OCSP request.
ocspReq, err := ocsp.CreateRequest(issuedCert, issuerCert, nil)
if err != nil {
return nil, nil, err
}
reader := bytes.NewReader(ocspReq)
req, err := httpPost(issuedCert.OCSPServer[0], "application/ocsp-request", reader)
if err != nil {
return nil, nil, err
}
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defer req.Body.Close()
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ocspResBytes, err := ioutil.ReadAll(limitReader(req.Body, 1024*1024))
ocspRes, err := ocsp.ParseResponse(ocspResBytes, issuerCert)
if err != nil {
return nil, nil, err
}
if ocspRes.Certificate == nil {
err = ocspRes.CheckSignatureFrom(issuerCert)
if err != nil {
return nil, nil, err
}
}
return ocspResBytes, ocspRes, nil
}
func getKeyAuthorization(token string, key interface{}) (string, error) {
var publicKey crypto.PublicKey
switch k := key.(type) {
case *ecdsa.PrivateKey:
publicKey = k.Public()
case *rsa.PrivateKey:
publicKey = k.Public()
}
// Generate the Key Authorization for the challenge
jwk := keyAsJWK(publicKey)
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
var certDERBlock *pem.Block
for {
certDERBlock, bundle = pem.Decode(bundle)
if certDERBlock == nil {
break
}
if certDERBlock.Type == "CERTIFICATE" {
cert, err := x509.ParseCertificate(certDERBlock.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
}
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func parsePEMPrivateKey(key []byte) (crypto.PrivateKey, error) {
keyBlock, _ := pem.Decode(key)
switch keyBlock.Type {
case "RSA PRIVATE KEY":
return x509.ParsePKCS1PrivateKey(keyBlock.Bytes)
case "EC PRIVATE KEY":
return x509.ParseECPrivateKey(keyBlock.Bytes)
default:
return nil, errors.New("Unknown PEM header value")
}
}
func generatePrivateKey(keyType KeyType) (crypto.PrivateKey, error) {
switch keyType {
case EC256:
return ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
case EC384:
return ecdsa.GenerateKey(elliptic.P384(), rand.Reader)
case RSA2048:
return rsa.GenerateKey(rand.Reader, 2048)
case RSA4096:
return rsa.GenerateKey(rand.Reader, 4096)
case RSA8192:
return rsa.GenerateKey(rand.Reader, 8192)
}
return nil, fmt.Errorf("Invalid KeyType: %s", keyType)
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}
func generateCsr(privateKey crypto.PrivateKey, domain string, san []string) ([]byte, error) {
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template := x509.CertificateRequest{
Subject: pkix.Name{
CommonName: domain,
},
}
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if len(san) > 0 {
template.DNSNames = san
}
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return x509.CreateCertificateRequest(rand.Reader, &template, privateKey)
}
func pemEncode(data interface{}) []byte {
var pemBlock *pem.Block
switch key := data.(type) {
case *ecdsa.PrivateKey:
keyBytes, _ := x509.MarshalECPrivateKey(key)
pemBlock = &pem.Block{Type: "EC PRIVATE KEY", Bytes: keyBytes}
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case *rsa.PrivateKey:
pemBlock = &pem.Block{Type: "RSA PRIVATE KEY", Bytes: x509.MarshalPKCS1PrivateKey(key)}
break
case derCertificateBytes:
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pemBlock = &pem.Block{Type: "CERTIFICATE", Bytes: []byte(data.(derCertificateBytes))}
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}
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
}
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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)
}
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func limitReader(rd io.ReadCloser, numBytes int64) io.ReadCloser {
return http.MaxBytesReader(nil, rd, numBytes)
}