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JWTService.go
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JWTService.go
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// Copyright 2013-2018 Adam Presley. All rights reserved
// Use of this source code is governed by the MIT license
// that can be found in the LICENSE file.
package jwt
import (
"bytes"
"crypto/aes"
"crypto/cipher"
"crypto/rand"
"crypto/sha1"
"encoding/base64"
"io"
"time"
"golang.org/x/crypto/pbkdf2"
"github.com/dgrijalva/jwt-go"
"github.com/mailslurper/mailslurper/pkg/mailslurper"
"github.com/pkg/errors"
)
/*
JWTService provides methods for working with
JWTs in MailSlurper
*/
type JWTService struct {
Config *mailslurper.Configuration
}
/*
CreateToken creates a new JWT token for use in
MailSlurper services
*/
func (s *JWTService) CreateToken(authSecret, user string) (string, error) {
claims := &Claims{
StandardClaims: jwt.StandardClaims{
ExpiresAt: time.Now().Add(time.Minute * time.Duration(s.Config.AuthTimeoutInMinutes)).Unix(),
Issuer: JWTIssuer,
},
User: user,
}
token := jwt.NewWithClaims(jwt.SigningMethodHS256, claims)
return token.SignedString([]byte(authSecret))
}
/*
DecryptToken takes a Base64 encoded token which has been encrypted
using AES-256 encryption. This returns the unencoded, unencrypted
token
*/
func (s *JWTService) DecryptToken(token string) (string, error) {
var err error
var aesBlock cipher.Block
var unencodedToken []byte
var gcm cipher.AEAD
var nonce []byte
var resultBytes []byte
key := s.generateAESKey()
if unencodedToken, err = base64.StdEncoding.DecodeString(token); err != nil {
return "", errors.Wrapf(err, "Unable to base64 decode JWT token")
}
if aesBlock, err = aes.NewCipher(key); err != nil {
return "", errors.Wrapf(err, "Unable to create AES cipher block")
}
if gcm, err = cipher.NewGCM(aesBlock); err != nil {
return "", errors.Wrapf(err, "Problem creating GCM")
}
nonceSize := gcm.NonceSize()
if len(unencodedToken) < nonceSize {
return "", errors.Wrapf(err, "Ciphertext too short")
}
nonce, cipherText := unencodedToken[:nonceSize], unencodedToken[nonceSize:]
if resultBytes, err = gcm.Open(nil, nonce, cipherText, nil); err != nil {
return "", errors.Wrapf(err, "Problem decrypting token")
}
return string(resultBytes), nil
}
/*
EncryptToken takes a token string, encrypts it using AES-256,
then encodes it in Base64.
*/
func (s *JWTService) EncryptToken(token string) (string, error) {
var err error
var aesBlock cipher.Block
var gcm cipher.AEAD
var nonce []byte
var encryptedResult []byte
key := s.generateAESKey()
if aesBlock, err = aes.NewCipher(key); err != nil {
return "", errors.Wrapf(err, "Unable to create AES cipher block")
}
if gcm, err = cipher.NewGCM(aesBlock); err != nil {
return "", errors.Wrapf(err, "Problem creating GCM")
}
nonce = make([]byte, gcm.NonceSize())
io.ReadFull(rand.Reader, nonce)
encryptedResult = gcm.Seal(nonce, nonce, []byte(token), nil)
encodedResult := base64.StdEncoding.EncodeToString(encryptedResult)
return encodedResult, nil
}
/*
GetUserFromToken retrieves the user from the claims in
a JWT token
*/
func (s *JWTService) GetUserFromToken(token *jwt.Token) string {
var claims *Claims
claims, _ = token.Claims.(*Claims)
return claims.User
}
/*
Parse decrypts the provided token and returns a JWT token object
*/
func (s *JWTService) Parse(tokenFromHeader, authSecret string) (*jwt.Token, error) {
var result *jwt.Token
var decryptedToken string
var err error
/*
* Decrypt token first
*/
if decryptedToken, err = s.DecryptToken(tokenFromHeader); err != nil {
return result, errors.Wrapf(err, "Problem decrypting JWT token in Parse")
}
if result, err = jwt.ParseWithClaims(decryptedToken, &Claims{}, func(token *jwt.Token) (interface{}, error) {
var ok bool
if _, ok = token.Method.(*jwt.SigningMethodHMAC); !ok {
return result, ErrInvalidToken
}
return []byte(authSecret), nil
}); err != nil {
return result, errors.Wrapf(err, "Problem parsing JWT token")
}
if err = s.IsTokenValid(result); err != nil {
return result, err
}
return result, nil
}
/*
IsTokenValid returns an error if there are any issues with the
provided JWT token. Possible issues include:
* Missing claims
* Invalid token format
* Invalid issuer
* User doesn't have a corresponding entry in the credentials table
*/
func (s *JWTService) IsTokenValid(token *jwt.Token) error {
var claims *Claims
var ok bool
claims, ok = token.Claims.(*Claims)
if !ok {
return ErrTokenMissingClaims
}
if !token.Valid {
return ErrInvalidToken
}
if claims.Issuer != JWTIssuer {
return ErrInvalidIssuer
}
if _, ok = s.Config.Credentials[claims.User]; !ok {
return ErrInvalidUser
}
return nil
}
func (s *JWTService) generateAESKey() []byte {
return pbkdf2.Key([]byte(s.Config.AuthSecret), []byte(s.Config.AuthSalt), 4096, 32, sha1.New)
}
func (s *JWTService) pkcs5Padding(content []byte) []byte {
padding := aes.BlockSize - len(content)%aes.BlockSize
padtext := bytes.Repeat([]byte{byte(padding)}, padding)
return append(content, padtext...)
}