package jwt
import (
"crypto/subtle"
"fmt"
"time"
)
// For a type to be a Claims object, it must just have a Valid method that determines
// if the token is invalid for any supported reason
type Claims interface {
Valid() error
}
// Structured version of Claims Section, as referenced at
// https://tools.ietf.org/html/rfc7519#section-4.1
// See examples for how to use this with your own claim types
type StandardClaims struct {
Audience string `json:"aud,omitempty"`
ExpiresAt int64 `json:"exp,omitempty"`
Id string `json:"jti,omitempty"`
IssuedAt int64 `json:"iat,omitempty"`
Issuer string `json:"iss,omitempty"`
NotBefore int64 `json:"nbf,omitempty"`
Subject string `json:"sub,omitempty"`
}
// Validates time based claims "exp, iat, nbf".
// There is no accounting for clock skew.
// As well, if any of the above claims are not in the token, it will still
// be considered a valid claim.
func (c StandardClaims) Valid() error {
vErr := new(ValidationError)
now := TimeFunc().Unix()
// The claims below are optional, by default, so if they are set to the
// default value in Go, let's not fail the verification for them.
if c.VerifyExpiresAt(now, false) == false {
delta := time.Unix(now, 0).Sub(time.Unix(c.ExpiresAt, 0))
vErr.Inner = fmt.Errorf("token is expired by %v", delta)
vErr.Errors |= ValidationErrorExpired
}
if c.VerifyIssuedAt(now, false) == false {
vErr.Inner = fmt.Errorf("Token used before issued")
vErr.Errors |= ValidationErrorIssuedAt
}
if c.VerifyNotBefore(now, false) == false {
vErr.Inner = fmt.Errorf("token is not valid yet")
vErr.Errors |= ValidationErrorNotValidYet
}
if vErr.valid() {
return nil
}
return vErr
}
// Compares the aud claim against cmp.
// If required is false, this method will return true if the value matches or is unset
func (c *StandardClaims) VerifyAudience(cmp string, req bool) bool {
return verifyAud(c.Audience, cmp, req)
}
// Compares the exp claim against cmp.
// If required is false, this method will return true if the value matches or is unset
func (c *StandardClaims) VerifyExpiresAt(cmp int64, req bool) bool {
return verifyExp(c.ExpiresAt, cmp, req)
}
// Compares the iat claim against cmp.
// If required is false, this method will return true if the value matches or is unset
func (c *StandardClaims) VerifyIssuedAt(cmp int64, req bool) bool {
return verifyIat(c.IssuedAt, cmp, req)
}
// Compares the iss claim against cmp.
// If required is false, this method will return true if the value matches or is unset
func (c *StandardClaims) VerifyIssuer(cmp string, req bool) bool {
return verifyIss(c.Issuer, cmp, req)
}
// Compares the nbf claim against cmp.
// If required is false, this method will return true if the value matches or is unset
func (c *StandardClaims) VerifyNotBefore(cmp int64, req bool) bool {
return verifyNbf(c.NotBefore, cmp, req)
}
// ----- helpers
func verifyAud(aud string, cmp string, required bool) bool {
if aud == "" {
return !required
}
if subtle.ConstantTimeCompare([]byte(aud), []byte(cmp)) != 0 {
return true
} else {
return false
}
}
func verifyExp(exp int64, now int64, required bool) bool {
if exp == 0 {
return !required
}
return now <= exp
}
func verifyIat(iat int64, now int64, required bool) bool {
if iat == 0 {
return !required
}
return now >= iat
}
func verifyIss(iss string, cmp string, required bool) bool {
if iss == "" {
return !required
}
if subtle.ConstantTimeCompare([]byte(iss), []byte(cmp)) != 0 {
return true
} else {
return false
}
}
func verifyNbf(nbf int64, now int64, required bool) bool {
if nbf == 0 {
return !required
}
return now >= nbf
}
