certificates/ca/client.go

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2018-10-05 21:48:36 +00:00
package ca
import (
"bytes"
"crypto"
"crypto/ecdsa"
"crypto/elliptic"
"crypto/rand"
"crypto/sha256"
"crypto/tls"
"crypto/x509"
"crypto/x509/pkix"
"encoding/hex"
"encoding/json"
"encoding/pem"
"io"
"io/ioutil"
"net/http"
"net/url"
"strings"
"github.com/pkg/errors"
"github.com/smallstep/ca-component/api"
"golang.org/x/net/http2"
"gopkg.in/square/go-jose.v2/jwt"
)
// ClientOption is the type of options passed to the Client constructor.
type ClientOption func(o *clientOptions) error
type clientOptions struct {
transport http.RoundTripper
rootSHA256 string
rootFilename string
}
func (o *clientOptions) apply(opts []ClientOption) (err error) {
for _, fn := range opts {
if err = fn(o); err != nil {
return
}
}
return
}
// checkTransport checks if other ways to set up a transport have been provided.
// If they have it returns an error.
func (o *clientOptions) checkTransport() error {
if o.transport != nil || o.rootFilename != "" || o.rootSHA256 != "" {
return errors.New("multiple transport methods have been configured")
}
return nil
}
// getTransport returns the transport configured in the clientOptions.
func (o *clientOptions) getTransport(endpoint string) (tr http.RoundTripper, err error) {
if o.transport != nil {
tr = o.transport
}
if o.rootFilename != "" {
if tr, err = getTransportFromFile(o.rootFilename); err != nil {
return nil, err
}
}
if o.rootSHA256 != "" {
if tr, err = getTransportFromSHA256(endpoint, o.rootSHA256); err != nil {
return nil, err
}
}
if tr == nil {
return nil, errors.New("a transport, a root cert, or a root sha256 must be used")
}
return tr, nil
}
// WithTransport adds a custom transport to the Client. If the transport is
// given is given it will have preference over WithRootFile and WithRootSHA256.
func WithTransport(tr http.RoundTripper) ClientOption {
return func(o *clientOptions) error {
if err := o.checkTransport(); err != nil {
return err
}
o.transport = tr
return nil
}
}
// WithRootFile will create the transport using the given root certificate. If
// the root file is given it will have preference over WithRootSHA256, but less
// preference than WithTransport.
func WithRootFile(filename string) ClientOption {
return func(o *clientOptions) error {
if err := o.checkTransport(); err != nil {
return err
}
o.rootFilename = filename
return nil
}
}
// WithRootSHA256 will create the transport using an insecure client to retrieve the
// root certificate. It has less preference than WithTransport and WithRootFile.
func WithRootSHA256(sum string) ClientOption {
return func(o *clientOptions) error {
if err := o.checkTransport(); err != nil {
return err
}
o.rootSHA256 = sum
return nil
}
}
func getTransportFromFile(filename string) (http.RoundTripper, error) {
data, err := ioutil.ReadFile(filename)
if err != nil {
return nil, errors.Wrapf(err, "error reading %s", filename)
}
block, _ := pem.Decode(data)
if block == nil {
return nil, errors.Errorf("error decoding %s", filename)
}
root, err := x509.ParseCertificate(block.Bytes)
if err != nil {
return nil, errors.Wrapf(err, "error parsing %s", filename)
}
pool := x509.NewCertPool()
pool.AddCert(root)
return getDefaultTransport(&tls.Config{
MinVersion: tls.VersionTLS12,
PreferServerCipherSuites: true,
RootCAs: pool,
})
}
func getTransportFromSHA256(endpoint, sum string) (http.RoundTripper, error) {
client, err := NewClient(endpoint)
if err != nil {
return nil, err
}
root, err := client.Root(sum)
if err != nil {
return nil, err
}
pool := x509.NewCertPool()
pool.AddCert(root.RootPEM.Certificate)
return getDefaultTransport(&tls.Config{
MinVersion: tls.VersionTLS12,
PreferServerCipherSuites: true,
RootCAs: pool,
})
}
// Client implements an HTTP client for the CA server.
type Client struct {
client *http.Client
endpoint *url.URL
certPool *x509.CertPool
}
// NewClient creates a new Client with the given endpoint and options.
func NewClient(endpoint string, opts ...ClientOption) (*Client, error) {
// Validate endpoint
u, err := url.Parse(endpoint)
if err != nil {
return nil, errors.Wrap(err, "error parsing endpoint")
}
if u.Scheme == "" || u.Host == "" {
return nil, errors.New("error parsing endpoint: url is not valid")
}
// Retrieve transport from options.
o := new(clientOptions)
if err := o.apply(opts); err != nil {
return nil, err
}
tr, err := o.getTransport(endpoint)
if err != nil {
return nil, err
}
var cp *x509.CertPool
switch tr := tr.(type) {
case *http.Transport:
if tr.TLSClientConfig != nil && tr.TLSClientConfig.RootCAs != nil {
cp = tr.TLSClientConfig.RootCAs
}
case *http2.Transport:
if tr.TLSClientConfig != nil && tr.TLSClientConfig.RootCAs != nil {
cp = tr.TLSClientConfig.RootCAs
}
}
return &Client{
client: &http.Client{
Transport: tr,
},
endpoint: u,
certPool: cp,
}, nil
}
// Health performs the health request to the CA and returns the
// api.HealthResponse struct.
func (c *Client) Health() (*api.HealthResponse, error) {
u := c.endpoint.ResolveReference(&url.URL{Path: "/health"})
resp, err := c.client.Get(u.String())
if err != nil {
return nil, errors.Wrapf(err, "client GET %s failed", u)
}
if resp.StatusCode >= 400 {
return nil, readError(resp.Body)
}
var health api.HealthResponse
if err := readJSON(resp.Body, &health); err != nil {
return nil, errors.Wrapf(err, "error reading %s", u)
}
return &health, nil
}
// Root performs the root request to the CA with the given SHA256 and returns
// the api.RootResponse struct. It uses an insecure client, but it checks the
// resulting root certificate with the given SHA256, returning an error if they
// do not match.
func (c *Client) Root(sha256Sum string) (*api.RootResponse, error) {
sha256Sum = strings.ToLower(strings.Replace(sha256Sum, "-", "", -1))
u := c.endpoint.ResolveReference(&url.URL{Path: "/root/" + sha256Sum})
resp, err := getInsecureClient().Get(u.String())
if err != nil {
return nil, errors.Wrapf(err, "client GET %s failed", u)
}
if resp.StatusCode >= 400 {
return nil, readError(resp.Body)
}
var root api.RootResponse
if err := readJSON(resp.Body, &root); err != nil {
return nil, errors.Wrapf(err, "error reading %s", u)
}
// verify the sha256
sum := sha256.Sum256(root.RootPEM.Raw)
if sha256Sum != strings.ToLower(hex.EncodeToString(sum[:])) {
return nil, errors.New("root certificate SHA256 fingerprint do not match")
}
return &root, nil
}
// Sign performs the sign request to the CA and returns the api.SignResponse
// struct.
func (c *Client) Sign(req *api.SignRequest) (*api.SignResponse, error) {
body, err := json.Marshal(req)
if err != nil {
return nil, errors.Wrap(err, "error marshaling request")
}
u := c.endpoint.ResolveReference(&url.URL{Path: "/sign"})
resp, err := c.client.Post(u.String(), "application/json", bytes.NewReader(body))
if err != nil {
return nil, errors.Wrapf(err, "client POST %s failed", u)
}
if resp.StatusCode >= 400 {
return nil, readError(resp.Body)
}
var sign api.SignResponse
if err := readJSON(resp.Body, &sign); err != nil {
return nil, errors.Wrapf(err, "error reading %s", u)
}
// Add tls.ConnectionState:
// We'll extract the root certificate from the verified chains
sign.TLS = resp.TLS
return &sign, nil
}
// Renew performs the renew request to the CA and returns the api.SignResponse
// struct.
func (c *Client) Renew(tr http.RoundTripper) (*api.SignResponse, error) {
u := c.endpoint.ResolveReference(&url.URL{Path: "/renew"})
client := &http.Client{Transport: tr}
resp, err := client.Post(u.String(), "application/json", http.NoBody)
if err != nil {
return nil, errors.Wrapf(err, "client POST %s failed", u)
}
if resp.StatusCode >= 400 {
return nil, readError(resp.Body)
}
var sign api.SignResponse
if err := readJSON(resp.Body, &sign); err != nil {
return nil, errors.Wrapf(err, "error reading %s", u)
}
return &sign, nil
}
// CreateSignRequest is a helper function that given an x509 OTT returns a
// simple but secure sign request as well as the private key used.
func CreateSignRequest(ott string) (*api.SignRequest, crypto.PrivateKey, error) {
token, err := jwt.ParseSigned(ott)
if err != nil {
return nil, nil, errors.Wrap(err, "error parsing ott")
}
var claims jwt.Claims
if err := token.UnsafeClaimsWithoutVerification(&claims); err != nil {
return nil, nil, errors.Wrap(err, "error parsing ott")
}
pk, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
if err != nil {
return nil, nil, errors.Wrap(err, "error generating key")
}
template := &x509.CertificateRequest{
Subject: pkix.Name{
CommonName: claims.Subject,
},
SignatureAlgorithm: x509.ECDSAWithSHA256,
DNSNames: []string{claims.Subject},
}
csr, err := x509.CreateCertificateRequest(rand.Reader, template, pk)
if err != nil {
return nil, nil, errors.Wrap(err, "error creating certificate request")
}
cr, err := x509.ParseCertificateRequest(csr)
if err != nil {
return nil, nil, errors.Wrap(err, "error parsing certificate request")
}
if err := cr.CheckSignature(); err != nil {
return nil, nil, errors.Wrap(err, "error signing certificate request")
}
return &api.SignRequest{
CsrPEM: api.CertificateRequest{CertificateRequest: cr},
OTT: ott,
}, pk, nil
}
func getInsecureClient() *http.Client {
return &http.Client{
Transport: &http.Transport{
TLSClientConfig: &tls.Config{InsecureSkipVerify: true},
},
}
}
func readJSON(r io.ReadCloser, v interface{}) error {
defer r.Close()
return json.NewDecoder(r).Decode(v)
}
func readError(r io.ReadCloser) error {
defer r.Close()
apiErr := new(api.Error)
if err := json.NewDecoder(r).Decode(apiErr); err != nil {
return err
}
return apiErr
}