Skip to content

Commit

Permalink
New Validation API
Browse files Browse the repository at this point in the history 
Some guidelines in designing the new validation API

* Previously, the `Valid` method was placed on the claim, which was always not entirely semantically correct, since the validity is concerning the token, not the claims. Although the validity of the token is based on the processing of the claims (such as `exp`). Therefore, the function `Valid` was removed from the `Claims` interface and the single canonical way to retrieve the validity of the token is to retrieve the `Valid` property of the `Token` struct.
* The previous fact was enhanced by the fact that most claims implementations had additional exported `VerifyXXX` functions, which are now removed
* All validation errors should be comparable with `errors.Is` to determine, why a particular validation has failed
* Developers want to adjust validation options. Popular options include:
  * Leeway when processing exp, nbf, iat
  * Not verifying `iat`, since this is actually just an informational claim. When purely looking at the standard, this should probably the default
  * Verifying `aud` by default, which actually the standard sort of demands. We need to see how strong we want to enforce this
* Developers want to create their own claim types, mostly by embedding one of the existing types such as `RegisteredClaims`.
  * Sometimes there is the need to further tweak the validation of a token by checking the value of a custom claim. Previously, this was possibly by overriding `Valid`. However, this was error-prone, e.g., if the original `Valid` was not called. Therefore, we should provide an easy way for *additional* checks, without by-passing the necessary validations

This leads to the following two major changes:

* The `Claims` interface now represents a set of functions that return the mandatory claims represented in a token, rather than just a `Valid` function. This is also more semantically correct.
* All validation tasks are offloaded to a new (optional) `Validator`, which can also be configured with appropriate options. If no custom validator was supplied, a default one is used.
  • Loading branch information
@oxisto
oxisto committed Aug 27, 2022
1 parent 895749e commit 1b437d8
Show file tree
Hide file tree
Showing 10 changed files with 320 additions and 376 deletions.
255 changes: 27 additions & 228 deletions claims.go
View file
@@ -1,23 +1,25 @@
package jwt

import (
"crypto/subtle"
"fmt"
"time"
)

// Claims must just have a Valid method that determines
// if the token is invalid for any supported reason
// Claims represent any form of a JWT Claims Set according to
// https://datatracker.ietf.org/doc/html/rfc7519#section-4. In order to have a
// common basis for validation, it is required that an implementation is able to
// supply at least the claim names provided in
// https://datatracker.ietf.org/doc/html/rfc7519#section-4.1 namely `exp`,
// `iat`, `nbf`, `iss` and `aud`.
type Claims interface {
Valid() error
GetExpiryAt() *NumericDate
GetIssuedAt() *NumericDate
GetNotBefore() *NumericDate
GetIssuer() string
GetAudience() ClaimStrings
}

// RegisteredClaims are a structured version of the JWT Claims Set,
// restricted to Registered Claim Names, as referenced at
// https://datatracker.ietf.org/doc/html/rfc7519#section-4.1
//
// This type can be used on its own, but then additional private and
// public claims embedded in the JWT will not be parsed. The typical usecase
// public claims embedded in the JWT will not be parsed. The typical use-case
// therefore is to embedded this in a user-defined claim type.
//
// See examples for how to use this with your own claim types.
Expand All @@ -44,230 +46,27 @@ type RegisteredClaims struct {
ID string `json:"jti,omitempty"`
}

// Valid 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 RegisteredClaims) Valid() error {
vErr := new(ValidationError)
now := TimeFunc()

// 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) {
delta := now.Sub(c.ExpiresAt.Time)
vErr.Inner = fmt.Errorf("%s by %s", ErrTokenExpired, delta)
vErr.Errors |= ValidationErrorExpired
}

if !c.VerifyIssuedAt(now, false) {
vErr.Inner = ErrTokenUsedBeforeIssued
vErr.Errors |= ValidationErrorIssuedAt
}

if !c.VerifyNotBefore(now, false) {
vErr.Inner = ErrTokenNotValidYet
vErr.Errors |= ValidationErrorNotValidYet
}

if vErr.valid() {
return nil
}

return vErr
}

// VerifyAudience compares the aud claim against cmp.
// If required is false, this method will return true if the value matches or is unset
func (c *RegisteredClaims) VerifyAudience(cmp string, req bool) bool {
return verifyAud(c.Audience, cmp, req)
}

// VerifyExpiresAt compares the exp claim against cmp (cmp < exp).
// If req is false, it will return true, if exp is unset.
func (c *RegisteredClaims) VerifyExpiresAt(cmp time.Time, req bool) bool {
if c.ExpiresAt == nil {
return verifyExp(nil, cmp, req)
}

return verifyExp(&c.ExpiresAt.Time, cmp, req)
}

// VerifyIssuedAt compares the iat claim against cmp (cmp >= iat).
// If req is false, it will return true, if iat is unset.
func (c *RegisteredClaims) VerifyIssuedAt(cmp time.Time, req bool) bool {
if c.IssuedAt == nil {
return verifyIat(nil, cmp, req)
}

return verifyIat(&c.IssuedAt.Time, cmp, req)
}

// VerifyNotBefore compares the nbf claim against cmp (cmp >= nbf).
// If req is false, it will return true, if nbf is unset.
func (c *RegisteredClaims) VerifyNotBefore(cmp time.Time, req bool) bool {
if c.NotBefore == nil {
return verifyNbf(nil, cmp, req)
}

return verifyNbf(&c.NotBefore.Time, cmp, req)
}

// VerifyIssuer compares the iss claim against cmp.
// If required is false, this method will return true if the value matches or is unset
func (c *RegisteredClaims) VerifyIssuer(cmp string, req bool) bool {
return verifyIss(c.Issuer, cmp, req)
}

// StandardClaims are a structured version of the JWT Claims Set, as referenced at
// https://datatracker.ietf.org/doc/html/rfc7519#section-4. They do not follow the
// specification exactly, since they were based on an earlier draft of the
// specification and not updated. The main difference is that they only
// support integer-based date fields and singular audiences. This might lead to
// incompatibilities with other JWT implementations. The use of this is discouraged, instead
// the newer RegisteredClaims struct should be used.
//
// Deprecated: Use RegisteredClaims instead for a forward-compatible way to access registered claims in a struct.
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"`
}

// Valid 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) {
delta := time.Unix(now, 0).Sub(time.Unix(c.ExpiresAt, 0))
vErr.Inner = fmt.Errorf("%s by %s", ErrTokenExpired, delta)
vErr.Errors |= ValidationErrorExpired
}

if !c.VerifyIssuedAt(now, false) {
vErr.Inner = ErrTokenUsedBeforeIssued
vErr.Errors |= ValidationErrorIssuedAt
}

if !c.VerifyNotBefore(now, false) {
vErr.Inner = ErrTokenNotValidYet
vErr.Errors |= ValidationErrorNotValidYet
}

if vErr.valid() {
return nil
}

return vErr
}

// VerifyAudience 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([]string{c.Audience}, cmp, req)
}

// VerifyExpiresAt compares the exp claim against cmp (cmp < exp).
// If req is false, it will return true, if exp is unset.
func (c *StandardClaims) VerifyExpiresAt(cmp int64, req bool) bool {
if c.ExpiresAt == 0 {
return verifyExp(nil, time.Unix(cmp, 0), req)
}

t := time.Unix(c.ExpiresAt, 0)
return verifyExp(&t, time.Unix(cmp, 0), req)
}

// VerifyIssuedAt compares the iat claim against cmp (cmp >= iat).
// If req is false, it will return true, if iat is unset.
func (c *StandardClaims) VerifyIssuedAt(cmp int64, req bool) bool {
if c.IssuedAt == 0 {
return verifyIat(nil, time.Unix(cmp, 0), req)
}

t := time.Unix(c.IssuedAt, 0)
return verifyIat(&t, time.Unix(cmp, 0), req)
}

// VerifyNotBefore compares the nbf claim against cmp (cmp >= nbf).
// If req is false, it will return true, if nbf is unset.
func (c *StandardClaims) VerifyNotBefore(cmp int64, req bool) bool {
if c.NotBefore == 0 {
return verifyNbf(nil, time.Unix(cmp, 0), req)
}

t := time.Unix(c.NotBefore, 0)
return verifyNbf(&t, time.Unix(cmp, 0), req)
}

// VerifyIssuer 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)
}

// ----- helpers

func verifyAud(aud []string, cmp string, required bool) bool {
if len(aud) == 0 {
return !required
}
// use a var here to keep constant time compare when looping over a number of claims
result := false

var stringClaims string
for _, a := range aud {
if subtle.ConstantTimeCompare([]byte(a), []byte(cmp)) != 0 {
result = true
}
stringClaims = stringClaims + a
}

// case where "" is sent in one or many aud claims
if len(stringClaims) == 0 {
return !required
}

return result
// GetExpiryAt implements the Claims interface.
func (c RegisteredClaims) GetExpiryAt() *NumericDate {
return c.ExpiresAt
}

func verifyExp(exp *time.Time, now time.Time, required bool) bool {
if exp == nil {
return !required
}
return now.Before(*exp)
// GetNotBefore implements the Claims interface.
func (c RegisteredClaims) GetNotBefore() *NumericDate {
return c.NotBefore
}

func verifyIat(iat *time.Time, now time.Time, required bool) bool {
if iat == nil {
return !required
}
return now.After(*iat) || now.Equal(*iat)
// GetIssuedAt implements the Claims interface.
func (c RegisteredClaims) GetIssuedAt() *NumericDate {
return c.IssuedAt
}

func verifyNbf(nbf *time.Time, now time.Time, required bool) bool {
if nbf == nil {
return !required
}
return now.After(*nbf) || now.Equal(*nbf)
// GetAudience implements the Claims interface.
func (c RegisteredClaims) GetAudience() ClaimStrings {
return c.Audience
}

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
}
// GetIssuer implements the Claims interface.
func (c RegisteredClaims) GetIssuer() string {
return c.Issuer
}
26 changes: 25 additions & 1 deletion example_test.go
View file
Expand Up @@ -70,7 +70,7 @@ func ExampleNewWithClaims_customClaimsType() {
//Output: eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJmb28iOiJiYXIiLCJpc3MiOiJ0ZXN0IiwiZXhwIjoxNTE2MjM5MDIyfQ.xVuY2FZ_MRXMIEgVQ7J-TFtaucVFRXUzHm9LmV41goM <nil>
}

// Example creating a token using a custom claims type. The StandardClaim is embedded
// Example creating a token using a custom claims type. The RegisteredClaims is embedded
// in the custom type to allow for easy encoding, parsing and validation of standard claims.
func ExampleParseWithClaims_customClaimsType() {
tokenString := "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJmb28iOiJiYXIiLCJpc3MiOiJ0ZXN0IiwiYXVkIjoic2luZ2xlIn0.QAWg1vGvnqRuCFTMcPkjZljXHh8U3L_qUjszOtQbeaA"
Expand All @@ -93,6 +93,30 @@ func ExampleParseWithClaims_customClaimsType() {
// Output: bar test
}

// Example creating a token using a custom claims type and validation options. The RegisteredClaims is embedded
// in the custom type to allow for easy encoding, parsing and validation of standard claims.
func ExampleParseWithClaims_customValidator() {
tokenString := "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJmb28iOiJiYXIiLCJpc3MiOiJ0ZXN0IiwiYXVkIjoic2luZ2xlIn0.QAWg1vGvnqRuCFTMcPkjZljXHh8U3L_qUjszOtQbeaA"

type MyCustomClaims struct {
Foo string `json:"foo"`
jwt.RegisteredClaims
}

validator := jwt.NewValidator(jwt.WithLeeway(5 * time.Second))
token, err := jwt.ParseWithClaims(tokenString, &MyCustomClaims{}, func(token *jwt.Token) (interface{}, error) {
return []byte("AllYourBase"), nil
}, jwt.WithValidator(validator))

if claims, ok := token.Claims.(*MyCustomClaims); ok && token.Valid {
fmt.Printf("%v %v", claims.Foo, claims.RegisteredClaims.Issuer)
} else {
fmt.Println(err)
}

// Output: bar test
}

// An example of parsing the error types using bitfield checks
func ExampleParse_errorChecking() {
// Token from another example. This token is expired
Expand Down

0 comments on commit 1b437d8

Please sign in to comment.