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// MinIO Cloud Storage, (C) 2019-2020 MinIO, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package crypto
import (
"bytes"
"context"
"crypto/tls"
"crypto/x509"
"errors"
"fmt"
"io"
"io/ioutil"
"net/http"
"net/url"
"os"
"path/filepath"
"strings"
"time"
jsoniter "github.com/json-iterator/go"
xhttp "github.com/minio/minio/cmd/http"
xnet "github.com/minio/minio/pkg/net"
)
var json = jsoniter.ConfigCompatibleWithStandardLibrary
// ErrKESKeyExists is the error returned a KES server
// when a master key does exist.
var ErrKESKeyExists = NewKESError(http.StatusBadRequest, "key does already exist")
// KesConfig contains the configuration required
// to initialize and connect to a kes server.
type KesConfig struct {
Enabled bool
// The KES server endpoints.
Endpoint []string
// The path to the TLS private key used
// by MinIO to authenticate to the kes
// server during the TLS handshake (mTLS).
KeyFile string
// The path to the TLS certificate used
// by MinIO to authenticate to the kes
// server during the TLS handshake (mTLS).
//
// The kes server will also allow or deny
// access based on this certificate.
// In particular, the kes server will
// lookup the policy that corresponds to
// the identity in this certificate.
CertFile string
// Path to a file or directory containing
// the CA certificate(s) that issued / will
// issue certificates for the kes server.
//
// This is required if the TLS certificate
// of the kes server has not been issued
// (e.g. b/c it's self-signed) by a CA that
// MinIO trusts.
CAPath string
// The default key ID returned by KMS.KeyID().
DefaultKeyID string
// The HTTP transport configuration for
// the KES client.
Transport *http.Transport
}
// Verify verifies if the kes configuration is correct
func (k KesConfig) Verify() (err error) {
switch {
case len(k.Endpoint) == 0:
err = Errorf("crypto: missing kes endpoint")
case k.CertFile == "":
err = Errorf("crypto: missing cert file")
case k.KeyFile == "":
err = Errorf("crypto: missing key file")
case k.DefaultKeyID == "":
err = Errorf("crypto: missing default key id")
}
return err
}
type kesService struct {
client *kesClient
endpoints []string
defaultKeyID string
}
// NewKes returns a new kes KMS client. The returned KMS
// uses the X.509 certificate to authenticate itself to
// the kes server available at address.
//
// The defaultKeyID is the key ID returned when calling
// KMS.KeyID().
func NewKes(cfg KesConfig) (KMS, error) {
cert, err := tls.LoadX509KeyPair(cfg.CertFile, cfg.KeyFile)
if err != nil {
return nil, err
}
if cfg.Transport.TLSClientConfig != nil {
if err = loadCACertificates(cfg.CAPath,
cfg.Transport.TLSClientConfig.RootCAs); err != nil {
return nil, err
}
} else {
rootCAs, _ := x509.SystemCertPool()
if rootCAs == nil {
// In some systems (like Windows) system cert pool is
// not supported or no certificates are present on the
// system - so we create a new cert pool.
rootCAs = x509.NewCertPool()
}
if err = loadCACertificates(cfg.CAPath, rootCAs); err != nil {
return nil, err
}
cfg.Transport.TLSClientConfig = &tls.Config{
RootCAs: rootCAs,
}
}
cfg.Transport.TLSClientConfig.Certificates = []tls.Certificate{cert}
cfg.Transport.TLSClientConfig.NextProtos = []string{"h2"}
return &kesService{
client: &kesClient{
endpoints: cfg.Endpoint,
httpClient: http.Client{
Transport: cfg.Transport,
},
},
endpoints: cfg.Endpoint,
defaultKeyID: cfg.DefaultKeyID,
}, nil
}
// DefaultKeyID returns the default key ID that should be
// used for SSE-S3 or SSE-KMS when the S3 client does not
// provide an explicit key ID.
func (kes *kesService) DefaultKeyID() string {
return kes.defaultKeyID
}
// Info returns some information about the KES,
// configuration - like the endpoint or authentication
// method.
func (kes *kesService) Info() KMSInfo {
return KMSInfo{
Endpoints: kes.endpoints,
Name: kes.DefaultKeyID(),
AuthType: "TLS",
}
}
// CreateKey tries to create a new master key with the given keyID.
func (kes *kesService) CreateKey(keyID string) error { return kes.client.CreateKey(keyID) }
// GenerateKey returns a new plaintext key, generated by the KMS,
// and a sealed version of this plaintext key encrypted using the
// named key referenced by keyID. It also binds the generated key
// cryptographically to the provided context.
func (kes *kesService) GenerateKey(keyID string, ctx Context) (key [32]byte, sealedKey []byte, err error) {
context := ctx.AppendTo(make([]byte, 0, 128))
var plainKey []byte
plainKey, sealedKey, err = kes.client.GenerateDataKey(keyID, context)
if err != nil {
return key, nil, err
}
if len(plainKey) != len(key) {
return key, nil, Errorf("crypto: received invalid plaintext key size from KMS")
}
copy(key[:], plainKey)
return key, sealedKey, nil
}
// UnsealKey returns the decrypted sealedKey as plaintext key.
// Therefore it sends the sealedKey to the KMS which decrypts
// it using the named key referenced by keyID and responses with
// the plaintext key.
//
// The context must be same context as the one provided while
// generating the plaintext key / sealedKey.
func (kes *kesService) UnsealKey(keyID string, sealedKey []byte, ctx Context) (key [32]byte, err error) {
context := ctx.AppendTo(make([]byte, 0, 128))
var plainKey []byte
plainKey, err = kes.client.DecryptDataKey(keyID, sealedKey, context)
if err != nil {
return key, err
}
if len(plainKey) != len(key) {
return key, Errorf("crypto: received invalid plaintext key size from KMS")
}
copy(key[:], plainKey)
return key, nil
}
// kesClient implements the bare minimum functionality needed for
// MinIO to talk to a KES server. In particular, it implements
// • CreateKey (API: /v1/key/create/)
// • GenerateDataKey (API: /v1/key/generate/)
// • DecryptDataKey (API: /v1/key/decrypt/)
type kesClient struct {
endpoints []string
httpClient http.Client
}
// CreateKey tries to create a new cryptographic key with
// the specified name.
//
// The key will be generated by the server. The client
// application does not have the cryptographic key at
// any point in time.
func (c *kesClient) CreateKey(name string) error {
path := fmt.Sprintf("/v1/key/create/%s", url.PathEscape(name))
_, err := c.postRetry(path, nil, 0) // No request body and no response expected
if err != nil {
return err
}
return nil
}
// GenerateDataKey requests a new data key from the KES server.
// On success, the KES server will respond with the plaintext key
// and the ciphertext key as the plaintext key encrypted with
// the key specified by name.
//
// The optional context is crytpo. bound to the generated data key
// such that you have to provide the same context when decrypting
// the data key.
func (c *kesClient) GenerateDataKey(name string, context []byte) ([]byte, []byte, error) {
type Request struct {
Context []byte `json:"context"`
}
type Response struct {
Plaintext []byte `json:"plaintext"`
Ciphertext []byte `json:"ciphertext"`
}
body, err := json.Marshal(Request{
Context: context,
})
if err != nil {
return nil, nil, err
}
const limit = 1 << 20 // A plaintext/ciphertext key pair will never be larger than 1 MB
path := fmt.Sprintf("/v1/key/generate/%s", url.PathEscape(name))
resp, err := c.postRetry(path, bytes.NewReader(body), limit)
if err != nil {
return nil, nil, err
}
var response Response
if err = json.NewDecoder(resp).Decode(&response); err != nil {
return nil, nil, err
}
return response.Plaintext, response.Ciphertext, nil
}
// GenerateDataKey decrypts an encrypted data key with the key
// specified by name by talking to the KES server.
// On success, the KES server will respond with the plaintext key.
//
// The optional context must match the value you provided when
// generating the data key.
func (c *kesClient) DecryptDataKey(name string, ciphertext, context []byte) ([]byte, error) {
type Request struct {
Ciphertext []byte `json:"ciphertext"`
Context []byte `json:"context,omitempty"`
}
type Response struct {
Plaintext []byte `json:"plaintext"`
}
body, err := json.Marshal(Request{
Ciphertext: ciphertext,
Context: context,
})
if err != nil {
return nil, err
}
const limit = 1 << 20 // A data key will never be larger than 1 MiB
path := fmt.Sprintf("/v1/key/decrypt/%s", url.PathEscape(name))
resp, err := c.postRetry(path, bytes.NewReader(body), limit)
if err != nil {
return nil, err
}
var response Response
if err = json.NewDecoder(resp).Decode(&response); err != nil {
return nil, err
}
return response.Plaintext, nil
}
// NewKESError returns a new KES API error with the given
// HTTP status code and error message.
//
// Two errors with the same status code and
// error message are equal:
// e1 == e2 // true.
func NewKESError(code int, text string) error {
return kesError{
code: code,
message: text,
}
}
type kesError struct {
code int
message string
}
// Status returns the HTTP status code of the error.
func (e kesError) Status() int { return e.code }
// Status returns the error message of the error.
func (e kesError) Error() string { return e.message }
func parseErrorResponse(resp *http.Response) error {
if resp == nil || resp.StatusCode < 400 {
return nil
}
if resp.Body == nil {
return NewKESError(resp.StatusCode, "")
}
defer resp.Body.Close()
const MaxBodySize = 1 << 20
var size = resp.ContentLength
if size < 0 || size > MaxBodySize {
size = MaxBodySize
}
contentType := strings.TrimSpace(resp.Header.Get("Content-Type"))
if strings.HasPrefix(contentType, "application/json") {
type Response struct {
Message string `json:"message"`
}
var response Response
if err := json.NewDecoder(io.LimitReader(resp.Body, size)).Decode(&response); err != nil {
return err
}
return NewKESError(resp.StatusCode, response.Message)
}
var sb strings.Builder
if _, err := io.Copy(&sb, io.LimitReader(resp.Body, size)); err != nil {
return err
}
return NewKESError(resp.StatusCode, sb.String())
}
func (c *kesClient) post(url string, body io.Reader, limit int64) (io.Reader, error) {
ctx, cancel := context.WithTimeout(context.Background(), 3*time.Second)
defer cancel()
req, err := http.NewRequestWithContext(ctx, http.MethodPost, url, body)
if err != nil {
return nil, err
}
req.Header.Set("Content-Type", "application/json")
resp, err := c.httpClient.Do(req)
if err != nil {
return nil, err
}
// Drain the entire body to make sure we have re-use connections
defer xhttp.DrainBody(resp.Body)
if resp.StatusCode != http.StatusOK {
return nil, parseErrorResponse(resp)
}
// We have to copy the response body due to draining.
var respBody bytes.Buffer
if _, err = io.Copy(&respBody, io.LimitReader(resp.Body, limit)); err != nil {
return nil, err
}
return &respBody, nil
}
func (c *kesClient) postRetry(path string, body io.ReadSeeker, limit int64) (io.Reader, error) {
retryMax := 1 + len(c.endpoints)
for i := 0; ; i++ {
if body != nil {
body.Seek(0, io.SeekStart) // seek to the beginning of the body.
}
response, err := c.post(c.endpoints[i%len(c.endpoints)]+path, body, limit)
if err == nil {
return response, nil
}
// If the error is not temp. / retryable => fail the request immediately.
if !xnet.IsNetworkOrHostDown(err, false) &&
!errors.Is(err, io.EOF) &&
!errors.Is(err, io.ErrUnexpectedEOF) &&
!errors.Is(err, context.DeadlineExceeded) {
return nil, err
}
if remain := retryMax - i; remain <= 0 { // Fail if we exceeded our retry limit.
return response, err
}
// If there are more KES instances then skip waiting and
// try the next endpoint directly.
if i < len(c.endpoints) {
continue
}
<-time.After(LinearJitterBackoff(retryWaitMin, retryWaitMax, i))
}
}
// loadCACertificates returns a new CertPool
// that contains all system root CA certificates
// and any PEM-encoded certificate(s) found at
// path.
//
// If path is a file, loadCACertificates will
// try to parse it as PEM-encoded certificate.
// If this fails, it returns an error.
//
// If path is a directory it tries to parse each
// file as PEM-encoded certificate and add it to
// the CertPool. If a file is not a PEM certificate
// it will be ignored.
func loadCACertificates(path string, rootCAs *x509.CertPool) error {
if path == "" {
return nil
}
stat, err := os.Stat(path)
if err != nil {
if os.IsNotExist(err) || os.IsPermission(err) {
return nil
}
return Errorf("crypto: cannot open '%s': %v", path, err)
}
// If path is a file, parse as PEM-encoded certifcate
// and try to add it to the CertPool. If this fails
// return an error.
if !stat.IsDir() {
cert, err := ioutil.ReadFile(path)
if err != nil {
return err
}
if !rootCAs.AppendCertsFromPEM(cert) {
return Errorf("crypto: '%s' is not a valid PEM-encoded certificate", path)
}
return nil
}
// If path is a directory then try
// to parse each file as PEM-encoded
// certificate and add it to the CertPool.
// If a file is not a PEM-encoded certificate
// we ignore it.
files, err := ioutil.ReadDir(path)
if err != nil {
return err
}
for _, file := range files {
cert, err := ioutil.ReadFile(filepath.Join(path, file.Name()))
if err != nil {
continue // ignore files which are not readable
}
rootCAs.AppendCertsFromPEM(cert) // ignore files which are not PEM certtificates
}
return nil
}