package acme import ( "bytes" "crypto" "crypto/ecdsa" "crypto/elliptic" "crypto/rand" "crypto/rsa" "crypto/x509" "crypto/x509/pkix" "encoding/asn1" "encoding/base64" "encoding/pem" "errors" "fmt" "io" "io/ioutil" "math/big" "net/http" "time" "golang.org/x/crypto/ocsp" jose "gopkg.in/square/go-jose.v2" ) // KeyType represents the key algo as well as the key size or curve to use. type KeyType string type derCertificateBytes []byte // Constants for all key types we support. const ( EC256 = KeyType("P256") EC384 = KeyType("P384") 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 ) // Constants for OCSP must staple var ( tlsFeatureExtensionOID = asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 1, 24} ocspMustStapleFeature = []byte{0x30, 0x03, 0x02, 0x01, 0x05} ) // 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 } defer resp.Body.Close() 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 // We want it ordered right SRV CRT -> CA certificates = append(certificates, issuerCert) } 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 } defer req.Body.Close() ocspResBytes, err := ioutil.ReadAll(limitReader(req.Body, 1024*1024)) if err != nil { return nil, nil, err } ocspRes, err := ocsp.ParseResponse(ocspResBytes, 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 := &jose.JSONWebKey{Key: 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.RawURLEncoding.EncodeToString(thumbBytes) return token + "." + keyThumb, nil } // 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 } 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) } func generateCsr(privateKey crypto.PrivateKey, domain string, san []string, mustStaple bool) ([]byte, error) { template := x509.CertificateRequest{ Subject: pkix.Name{CommonName: domain}, } if len(san) > 0 { template.DNSNames = san } if mustStaple { template.ExtraExtensions = append(template.ExtraExtensions, pkix.Extension{ Id: tlsFeatureExtensionOID, Value: ocspMustStapleFeature, }) } 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} case *rsa.PrivateKey: pemBlock = &pem.Block{Type: "RSA PRIVATE KEY", Bytes: x509.MarshalPKCS1PrivateKey(key)} case *x509.CertificateRequest: pemBlock = &pem.Block{Type: "CERTIFICATE REQUEST", Bytes: key.Raw} 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) } func pemDecodeTox509CSR(pem []byte) (*x509.CertificateRequest, error) { pemBlock, err := pemDecode(pem) if pemBlock == nil { return nil, err } if pemBlock.Type != "CERTIFICATE REQUEST" { return nil, fmt.Errorf("PEM block is not a certificate request") } return x509.ParseCertificateRequest(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, extensions []pkix.Extension) ([]byte, error) { derBytes, err := generateDerCert(privKey, time.Time{}, domain, extensions) 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, extensions []pkix.Extension) ([]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}, ExtraExtensions: extensions, } return x509.CreateCertificate(rand.Reader, &template, &template, &privKey.PublicKey, privKey) } func limitReader(rd io.ReadCloser, numBytes int64) io.ReadCloser { return http.MaxBytesReader(nil, rd, numBytes) }