Compatibility with jwt-go (golang-jwt) v5

Includes the StandardClaims implementation from jwt-go v4, where it was marked as
deprecated before removed in v5. The box backend needs this.

See #7115

backend/box/box.go

@@ -27,7 +27,6 @@ import (
 	"sync/atomic"
 	"time"
 
-	"github.com/golang-jwt/jwt/v4"
 	"github.com/rclone/rclone/backend/box/api"
 	"github.com/rclone/rclone/fs"
 	"github.com/rclone/rclone/fs/config"
@@ -77,7 +76,7 @@ var (
 )
 
 type boxCustomClaims struct {
-	jwt.StandardClaims
+	jwtutil.StandardClaims
 	BoxSubType string `json:"box_sub_type,omitempty"`
 }
 
@@ -225,10 +224,8 @@ func getClaims(boxConfig *api.ConfigJSON, boxSubType string) (claims *boxCustomC
 	}
 
 	claims = &boxCustomClaims{
-		//lint:ignore SA1019 since we need to use jwt.StandardClaims even if deprecated in jwt-go v4 until a more permanent solution is ready in time before jwt-go v5 where it is removed entirely
-		//nolint:staticcheck // Don't include staticcheck when running golangci-lint to avoid SA1019
-		StandardClaims: jwt.StandardClaims{
-			Id:        val,
+		StandardClaims: jwtutil.StandardClaims{
+			ID:        val,
 			Issuer:    boxConfig.BoxAppSettings.ClientID,
 			Subject:   boxConfig.EnterpriseID,
 			Audience:  tokenURL,

lib/jwtutil/claims.go

@@ -0,0 +1,160 @@
+package jwtutil
+
+import (
+	"crypto/subtle"
+	"fmt"
+	"time"
+
+	"github.com/golang-jwt/jwt/v4"
+)
+
+// StandardClaims implementation from jwt-go v4, where it was marked as deprecated
+// before removed in v5.
+// See: https://github.com/golang-jwt/jwt/blob/v4/claims.go
+//
+// 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.
+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(jwt.ValidationError)
+	now := jwt.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", jwt.ErrTokenExpired, delta)
+		vErr.Errors |= jwt.ValidationErrorExpired
+	}
+
+	if !c.VerifyIssuedAt(now, false) {
+		vErr.Inner = jwt.ErrTokenUsedBeforeIssued
+		vErr.Errors |= jwt.ValidationErrorIssuedAt
+	}
+
+	if !c.VerifyNotBefore(now, false) {
+		vErr.Inner = jwt.ErrTokenNotValidYet
+		vErr.Errors |= jwt.ValidationErrorNotValidYet
+	}
+
+	if vErr.Errors == 0 {
+		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
+}
+
+func verifyExp(exp *time.Time, now time.Time, required bool) bool {
+	if exp == nil {
+		return !required
+	}
+	return now.Before(*exp)
+}
+
+func verifyIat(iat *time.Time, now time.Time, required bool) bool {
+	if iat == nil {
+		return !required
+	}
+	return now.After(*iat) || now.Equal(*iat)
+}
+
+func verifyNbf(nbf *time.Time, now time.Time, required bool) bool {
+	if nbf == nil {
+		return !required
+	}
+	return now.After(*nbf) || now.Equal(*nbf)
+}
+
+func verifyIss(iss string, cmp string, required bool) bool {
+	if iss == "" {
+		return !required
+	}
+	return subtle.ConstantTimeCompare([]byte(iss), []byte(cmp)) != 0
+}