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package sshgen
import (
"bytes"
"crypto/ecdsa"
"crypto/elliptic"
"crypto/rand"
"crypto/x509"
"encoding/json"
"encoding/pem"
"fmt"
"io"
"io/ioutil"
"net/http"
"net/url"
"time"
homedir "github.com/mitchellh/go-homedir"
"github.com/pkg/errors"
gossh "golang.org/x/crypto/ssh"
"gopkg.in/square/go-jose.v2/jwt"
"github.com/cloudflare/cloudflared/config"
cfpath "github.com/cloudflare/cloudflared/token"
)
const (
signEndpoint = "/cdn-cgi/access/cert_sign"
keyName = "cf_key"
)
// signPayload represents the request body sent to the sign handler API
type signPayload struct {
PublicKey string `json:"public_key"`
JWT string `json:"jwt"`
Issuer string `json:"issuer"`
}
// signResponse represents the response body from the sign handler API
type signResponse struct {
KeyID string `json:"id"`
Certificate string `json:"certificate"`
ExpiresAt time.Time `json:"expires_at"`
}
// ErrorResponse struct stores error information after any error-prone function
type errorResponse struct {
Status int `json:"status"`
Message string `json:"message"`
}
var mockRequest func(url, contentType string, body io.Reader) (*http.Response, error) = nil
// GenerateShortLivedCertificate generates and stores a keypair for short lived certs
func GenerateShortLivedCertificate(appURL *url.URL, token string) error {
fullName, err := cfpath.GenerateSSHCertFilePathFromURL(appURL, keyName)
if err != nil {
return err
}
cert, err := handleCertificateGeneration(token, fullName)
if err != nil {
return err
}
name := fullName + "-cert.pub"
if err := writeKey(name, []byte(cert)); err != nil {
return err
}
return nil
}
// handleCertificateGeneration takes a JWT and uses it build a signPayload
// to send to the Sign endpoint with the public key from the keypair it generated
func handleCertificateGeneration(token, fullName string) (string, error) {
pub, err := generateKeyPair(fullName)
if err != nil {
return "", err
}
return SignCert(token, string(pub))
}
func SignCert(token, pubKey string) (string, error) {
if token == "" {
return "", errors.New("invalid token")
}
parsedToken, err := jwt.ParseSigned(token)
if err != nil {
return "", errors.Wrap(err, "failed to parse JWT")
}
claims := jwt.Claims{}
err = parsedToken.UnsafeClaimsWithoutVerification(&claims)
if err != nil {
return "", errors.Wrap(err, "failed to retrieve JWT claims")
}
buf, err := json.Marshal(&signPayload{
PublicKey: pubKey,
JWT: token,
Issuer: claims.Issuer,
})
if err != nil {
return "", errors.Wrap(err, "failed to marshal signPayload")
}
var res *http.Response
if mockRequest != nil {
res, err = mockRequest(claims.Issuer+signEndpoint, "application/json", bytes.NewBuffer(buf))
} else {
client := http.Client{
Timeout: 10 * time.Second,
}
res, err = client.Post(claims.Issuer+signEndpoint, "application/json", bytes.NewBuffer(buf))
}
if err != nil {
return "", errors.Wrap(err, "failed to send request")
}
defer res.Body.Close()
decoder := json.NewDecoder(res.Body)
if res.StatusCode != 200 {
var errResponse errorResponse
if err := decoder.Decode(&errResponse); err != nil {
return "", err
}
return "", fmt.Errorf("%d: %s", errResponse.Status, errResponse.Message)
}
var signRes signResponse
if err := decoder.Decode(&signRes); err != nil {
return "", errors.Wrap(err, "failed to decode HTTP response")
}
return signRes.Certificate, nil
}
// generateKeyPair creates a EC keypair (P256) and stores them in the homedir.
// returns the generated public key from the successful keypair generation
func generateKeyPair(fullName string) ([]byte, error) {
pubKeyName := fullName + ".pub"
exist, err := config.FileExists(pubKeyName)
if err != nil {
return nil, err
}
if exist {
return ioutil.ReadFile(pubKeyName)
}
key, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
if err != nil {
return nil, err
}
parsed, err := x509.MarshalECPrivateKey(key)
if err != nil {
return nil, err
}
if err := writeKey(fullName, pem.EncodeToMemory(&pem.Block{
Type: "EC PRIVATE KEY",
Bytes: parsed,
})); err != nil {
return nil, err
}
pub, err := gossh.NewPublicKey(&key.PublicKey)
if err != nil {
return nil, err
}
data := gossh.MarshalAuthorizedKey(pub)
if err := writeKey(pubKeyName, data); err != nil {
return nil, err
}
return data, nil
}
// writeKey will write a key to disk in DER format (it's a standard pem key)
func writeKey(filename string, data []byte) error {
filepath, err := homedir.Expand(filename)
if err != nil {
return err
}
return ioutil.WriteFile(filepath, data, 0600)
}