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jwt.go
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jwt.go
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package token
import (
"errors"
"fmt"
"time"
"github.com/dgrijalva/jwt-go"
)
var ErrJWInvalid = errors.New("token is invalid")
type authClaims struct {
Username string `json:"username"`
jwt.StandardClaims
}
type JW struct {
secret, username string
exp time.Time
tokenStr string
}
func NewJW(secret, username string, exp time.Duration) *JW {
return &JW{secret, username, time.Now().Add(exp), ""}
}
func NewJWFromExisting(secret, tokenStr string) (*JW, error) {
token, err := jwt.Parse(tokenStr, func(token *jwt.Token) (interface{}, error) {
if _, ok := token.Method.(*jwt.SigningMethodHMAC); !ok {
return nil, fmt.Errorf("unexpected signing method: %v: %w", token.Header["alg"], ErrJWInvalid)
}
return []byte(secret), nil
})
if err != nil {
return nil, fmt.Errorf("failed to parse token: %s: %w", tokenStr, err)
}
if !token.Valid {
return nil, ErrJWInvalid
}
claims, ok := token.Claims.(jwt.MapClaims)
if !ok {
return nil, fmt.Errorf("failed to extract claims: token claims type: %T: %w", claims, ErrJWInvalid)
}
t := &JW{secret: secret, tokenStr: tokenStr}
t.username, ok = claims["username"].(string)
if !ok {
return nil, fmt.Errorf("failed to extract username from claim: wanted: string got: %T: %w",
claims["username"], ErrJWInvalid)
}
exp, ok := claims["exp"].(float64)
if !ok {
return nil, fmt.Errorf("failed to extract expiration from claim: wanted: float64 got: %T: %w",
claims["exp"], ErrJWInvalid)
}
t.exp = time.Unix(int64(exp), 0)
return t, nil
}
func (t *JW) Token() string {
return t.tokenStr
}
func (t *JW) Generate() error {
token := jwt.NewWithClaims(jwt.SigningMethodHS256, &authClaims{
Username: t.username,
StandardClaims: jwt.StandardClaims{
ExpiresAt: t.exp.Unix(),
},
})
tokenStr, err := token.SignedString([]byte(t.secret))
if err != nil {
return fmt.Errorf("could not sign jwt: %w", err)
}
t.tokenStr = tokenStr
return nil
}
func (t *JW) ExpiresIn() time.Duration {
return time.Until(t.exp)
}
func (t *JW) IsExpired() bool {
return t.exp.Unix() < time.Now().Unix()
}