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jwt.go
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jwt.go
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package jwt
import (
"crypto/hmac"
"crypto/sha256"
"encoding/base64"
"encoding/json"
"fmt"
"hash"
"strconv"
"strings"
"time"
)
type JWT struct {
}
func (t *JWT) EncodeJWT(secret string, headers, payload map[string]string) (string, error) {
algo, ok := headers["algo"]
if !ok {
return "", fmt.Errorf("cannot create JWT")
}
hashData := t.createHash(secret, algo)
head, err := json.Marshal(headers)
if err != nil {
return "", err
}
payl, err := json.Marshal(payload)
if err != nil {
return "", err
}
h := base64.URLEncoding.EncodeToString(head)
pl := base64.URLEncoding.EncodeToString(payl)
token := fmt.Sprintf("%s.%s", h, pl)
_, err = hashData.Write([]byte(token))
if err != nil {
return "", err
}
newHash := hashData.Sum(nil)
hs := base64.URLEncoding.EncodeToString(newHash)
return fmt.Sprintf("%s.%s", token, hs), nil
}
func (t *JWT) VerifyJWT(secret, jwt string, expire int64) error {
jwtTokenParts, err := t.extractJWTParts(jwt)
if err != nil {
return err
}
err = t.checkSignature(secret, jwtTokenParts)
if err != nil {
return err
}
payload, err := t.extractPayload(jwtTokenParts[1])
if err != nil {
return err
}
return t.checkTime(payload, expire)
}
func (t *JWT) VerifyJWTAndGetPayload(secret, jwt string, expire int64) (map[string]string, error) {
jwtTokenParts, err := t.extractJWTParts(jwt)
if err != nil {
return nil, err
}
err = t.checkSignature(secret, jwtTokenParts)
if err != nil {
return nil, err
}
payload, err := t.extractPayload(jwtTokenParts[1])
if err != nil {
return nil, err
}
return payload, t.checkTime(payload, expire)
}
func (t *JWT) extractJWTParts(jwt string) ([]string, error) {
jwtToken := strings.Split(jwt, ".")
if len(jwtToken) != 3 {
return nil, fmt.Errorf("token not valid need to be from three parts")
}
return jwtToken, nil
}
func (t *JWT) checkSignature(secret string, jwtToken []string) error {
header := make(map[string]string)
h, err := base64.URLEncoding.DecodeString(jwtToken[0])
if err != nil {
return err
}
err = json.Unmarshal(h, &header)
if err != nil {
return err
}
algo, ok := header["algo"]
if !ok {
return fmt.Errorf("missing algo in header part")
}
jwtType, ok := header["type"]
if !ok || jwtType != "JWT" {
return fmt.Errorf("missing type in header part")
}
mhash := t.createHash(secret, algo)
_, err = mhash.Write([]byte(fmt.Sprintf("%s.%s", jwtToken[0], jwtToken[1])))
if err != nil {
return err
}
jwtTokenValue, _ := base64.URLEncoding.DecodeString(jwtToken[2])
valid := hmac.Equal(mhash.Sum(nil), jwtTokenValue)
if !valid {
return fmt.Errorf("token not valid")
}
return nil
}
func (t *JWT) extractPayload(jwtPayloadPart string) (map[string]string, error) {
payload := make(map[string]string)
payl, err := base64.URLEncoding.DecodeString(jwtPayloadPart)
if err != nil {
return nil, err
}
err = json.Unmarshal(payl, &payload)
if err != nil {
return nil, err
}
return payload, nil
}
func (t *JWT) checkTime(payload map[string]string, expire int64) error {
expireTime, ok := payload["exp"]
if !ok {
return fmt.Errorf("token expire time not valid")
}
expTime, _ := strconv.ParseInt(expireTime, 10, 64)
expTime = time.Now().Unix() - expTime
valid := expTime < expire
if !valid {
return fmt.Errorf("token time not valid %d %d", expTime, expire)
}
return nil
}
func (t *JWT) createHash(secret, algo string) hash.Hash {
switch algo {
case "HS256":
return hmac.New(sha256.New, []byte(secret))
default:
return hmac.New(sha256.New, []byte(secret))
}
}