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gitea/vendor/github.com/couchbase/goutils/scramsha/scramsha.go
2019-02-05 11:52:51 -05:00

208 lines
5.9 KiB
Go
Vendored

// @author Couchbase <info@couchbase.com>
// @copyright 2018 Couchbase, 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 scramsha provides implementation of client side SCRAM-SHA
// according to https://tools.ietf.org/html/rfc5802
package scramsha
import (
"crypto/hmac"
"crypto/rand"
"crypto/sha1"
"crypto/sha256"
"crypto/sha512"
"encoding/base64"
"fmt"
"github.com/pkg/errors"
"golang.org/x/crypto/pbkdf2"
"hash"
"strconv"
"strings"
)
func hmacHash(message []byte, secret []byte, hashFunc func() hash.Hash) []byte {
h := hmac.New(hashFunc, secret)
h.Write(message)
return h.Sum(nil)
}
func shaHash(message []byte, hashFunc func() hash.Hash) []byte {
h := hashFunc()
h.Write(message)
return h.Sum(nil)
}
func generateClientNonce(size int) (string, error) {
randomBytes := make([]byte, size)
_, err := rand.Read(randomBytes)
if err != nil {
return "", errors.Wrap(err, "Unable to generate nonce")
}
return base64.StdEncoding.EncodeToString(randomBytes), nil
}
// ScramSha provides context for SCRAM-SHA handling
type ScramSha struct {
hashSize int
hashFunc func() hash.Hash
clientNonce string
serverNonce string
salt []byte
i int
saltedPassword []byte
authMessage string
}
var knownMethods = []string{"SCRAM-SHA512", "SCRAM-SHA256", "SCRAM-SHA1"}
// BestMethod returns SCRAM-SHA method we consider the best out of suggested
// by server
func BestMethod(methods string) (string, error) {
for _, m := range knownMethods {
if strings.Index(methods, m) != -1 {
return m, nil
}
}
return "", errors.Errorf(
"None of the server suggested methods [%s] are supported",
methods)
}
// NewScramSha creates context for SCRAM-SHA handling
func NewScramSha(method string) (*ScramSha, error) {
s := &ScramSha{}
if method == knownMethods[0] {
s.hashFunc = sha512.New
s.hashSize = 64
} else if method == knownMethods[1] {
s.hashFunc = sha256.New
s.hashSize = 32
} else if method == knownMethods[2] {
s.hashFunc = sha1.New
s.hashSize = 20
} else {
return nil, errors.Errorf("Unsupported method %s", method)
}
return s, nil
}
// GetStartRequest builds start SCRAM-SHA request to be sent to server
func (s *ScramSha) GetStartRequest(user string) (string, error) {
var err error
s.clientNonce, err = generateClientNonce(24)
if err != nil {
return "", errors.Wrapf(err, "Unable to generate SCRAM-SHA "+
"start request for user %s", user)
}
message := fmt.Sprintf("n,,n=%s,r=%s", user, s.clientNonce)
s.authMessage = message[3:]
return message, nil
}
// HandleStartResponse handles server response on start SCRAM-SHA request
func (s *ScramSha) HandleStartResponse(response string) error {
parts := strings.Split(response, ",")
if len(parts) != 3 {
return errors.Errorf("expected 3 fields in first SCRAM-SHA-1 "+
"server message %s", response)
}
if !strings.HasPrefix(parts[0], "r=") || len(parts[0]) < 3 {
return errors.Errorf("Server sent an invalid nonce %s",
parts[0])
}
if !strings.HasPrefix(parts[1], "s=") || len(parts[1]) < 3 {
return errors.Errorf("Server sent an invalid salt %s", parts[1])
}
if !strings.HasPrefix(parts[2], "i=") || len(parts[2]) < 3 {
return errors.Errorf("Server sent an invalid iteration count %s",
parts[2])
}
s.serverNonce = parts[0][2:]
encodedSalt := parts[1][2:]
var err error
s.i, err = strconv.Atoi(parts[2][2:])
if err != nil {
return errors.Errorf("Iteration count %s must be integer.",
parts[2][2:])
}
if s.i < 1 {
return errors.New("Iteration count should be positive")
}
if !strings.HasPrefix(s.serverNonce, s.clientNonce) {
return errors.Errorf("Server nonce %s doesn't contain client"+
" nonce %s", s.serverNonce, s.clientNonce)
}
s.salt, err = base64.StdEncoding.DecodeString(encodedSalt)
if err != nil {
return errors.Wrapf(err, "Unable to decode salt %s",
encodedSalt)
}
s.authMessage = s.authMessage + "," + response
return nil
}
// GetFinalRequest builds final SCRAM-SHA request to be sent to server
func (s *ScramSha) GetFinalRequest(pass string) string {
clientFinalMessageBare := "c=biws,r=" + s.serverNonce
s.authMessage = s.authMessage + "," + clientFinalMessageBare
s.saltedPassword = pbkdf2.Key([]byte(pass), s.salt, s.i,
s.hashSize, s.hashFunc)
clientKey := hmacHash([]byte("Client Key"), s.saltedPassword, s.hashFunc)
storedKey := shaHash(clientKey, s.hashFunc)
clientSignature := hmacHash([]byte(s.authMessage), storedKey, s.hashFunc)
clientProof := make([]byte, len(clientSignature))
for i := 0; i < len(clientSignature); i++ {
clientProof[i] = clientKey[i] ^ clientSignature[i]
}
return clientFinalMessageBare + ",p=" +
base64.StdEncoding.EncodeToString(clientProof)
}
// HandleFinalResponse handles server's response on final SCRAM-SHA request
func (s *ScramSha) HandleFinalResponse(response string) error {
if strings.Contains(response, ",") ||
!strings.HasPrefix(response, "v=") {
return errors.Errorf("Server sent an invalid final message %s",
response)
}
decodedMessage, err := base64.StdEncoding.DecodeString(response[2:])
if err != nil {
return errors.Wrapf(err, "Unable to decode server message %s",
response[2:])
}
serverKey := hmacHash([]byte("Server Key"), s.saltedPassword,
s.hashFunc)
serverSignature := hmacHash([]byte(s.authMessage), serverKey,
s.hashFunc)
if string(decodedMessage) != string(serverSignature) {
return errors.Errorf("Server proof %s doesn't match "+
"the expected: %s",
string(decodedMessage), string(serverSignature))
}
return nil
}