Implementing `Is(err) bool` to support Go 1.13 style error checking (#136)

claims.go

@@ -56,17 +56,17 @@ func (c RegisteredClaims) Valid() error {
 	// 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("token is expired by %v", delta)
+		vErr.Inner = fmt.Errorf("%s by %v", delta, ErrTokenExpired)
 		vErr.Errors |= ValidationErrorExpired
 	}
 
 	if !c.VerifyIssuedAt(now, false) {
-		vErr.Inner = fmt.Errorf("token used before issued")
+		vErr.Inner = ErrTokenUsedBeforeIssued
 		vErr.Errors |= ValidationErrorIssuedAt
 	}
 
 	if !c.VerifyNotBefore(now, false) {
-		vErr.Inner = fmt.Errorf("token is not valid yet")
+		vErr.Inner = ErrTokenNotValidYet
 		vErr.Errors |= ValidationErrorNotValidYet
 	}
 
@@ -149,17 +149,17 @@ func (c StandardClaims) Valid() error {
 	// 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("token is expired by %v", delta)
+		vErr.Inner = fmt.Errorf("%s by %v", delta, ErrTokenExpired)
 		vErr.Errors |= ValidationErrorExpired
 	}
 
 	if !c.VerifyIssuedAt(now, false) {
-		vErr.Inner = fmt.Errorf("token used before issued")
+		vErr.Inner = ErrTokenUsedBeforeIssued
 		vErr.Errors |= ValidationErrorIssuedAt
 	}
 
 	if !c.VerifyNotBefore(now, false) {
-		vErr.Inner = fmt.Errorf("token is not valid yet")
+		vErr.Inner = ErrTokenNotValidYet
 		vErr.Errors |= ValidationErrorNotValidYet
 	}
 

errors.go

@@ -9,6 +9,18 @@ var (
 	ErrInvalidKey      = errors.New("key is invalid")
 	ErrInvalidKeyType  = errors.New("key is of invalid type")
 	ErrHashUnavailable = errors.New("the requested hash function is unavailable")
+
+	ErrTokenMalformed        = errors.New("token is malformed")
+	ErrTokenUnverifiable     = errors.New("token is unverifiable")
+	ErrTokenSignatureInvalid = errors.New("token signature is invalid")
+
+	ErrTokenInvalidAudience  = errors.New("token has invalid audience")
+	ErrTokenExpired          = errors.New("token is expired")
+	ErrTokenUsedBeforeIssued = errors.New("token used before issued")
+	ErrTokenInvalidIssuer    = errors.New("token has invalid issuer")
+	ErrTokenNotValidYet      = errors.New("token is not valid yet")
+	ErrTokenInvalidId        = errors.New("token has invalid id")
+	ErrTokenInvalidClaims    = errors.New("token has invalid claims")
 )
 
 // The errors that might occur when parsing and validating a token
@@ -62,3 +74,39 @@ func (e *ValidationError) Unwrap() error {
 func (e *ValidationError) valid() bool {
 	return e.Errors == 0
 }
+
+// Is checks if this ValidationError is of the supplied error. We are first checking for the exact error message
+// by comparing the inner error message. If that fails, we compare using the error flags. This way we can use
+// custom error messages (mainly for backwards compatability) and still leverage errors.Is using the global error variables.
+func (e *ValidationError) Is(err error) bool {
+	// Check, if our inner error is a direct match
+	if errors.Is(errors.Unwrap(e), err) {
+		return true
+	}
+
+	// Otherwise, we need to match using our error flags
+	switch err {
+	case ErrTokenMalformed:
+		return e.Errors&ValidationErrorMalformed != 0
+	case ErrTokenUnverifiable:
+		return e.Errors&ValidationErrorUnverifiable != 0
+	case ErrTokenSignatureInvalid:
+		return e.Errors&ValidationErrorSignatureInvalid != 0
+	case ErrTokenInvalidAudience:
+		return e.Errors&ValidationErrorAudience != 0
+	case ErrTokenExpired:
+		return e.Errors&ValidationErrorExpired != 0
+	case ErrTokenUsedBeforeIssued:
+		return e.Errors&ValidationErrorIssuedAt != 0
+	case ErrTokenInvalidIssuer:
+		return e.Errors&ValidationErrorIssuer != 0
+	case ErrTokenNotValidYet:
+		return e.Errors&ValidationErrorNotValidYet != 0
+	case ErrTokenInvalidId:
+		return e.Errors&ValidationErrorId != 0
+	case ErrTokenInvalidClaims:
+		return e.Errors&ValidationErrorClaimsInvalid != 0
+	}
+
+	return false
+}

example_test.go

@@ -1,6 +1,7 @@
 package jwt_test
 
 import (
+	"errors"
 	"fmt"
 	"time"
 
@@ -103,18 +104,14 @@ func ExampleParse_errorChecking() {
 
 	if token.Valid {
 		fmt.Println("You look nice today")
-	} else if ve, ok := err.(*jwt.ValidationError); ok {
-		if ve.Errors&jwt.ValidationErrorMalformed != 0 {
+	} else if errors.Is(err, jwt.ErrTokenMalformed) {
 		fmt.Println("That's not even a token")
-		} else if ve.Errors&(jwt.ValidationErrorExpired|jwt.ValidationErrorNotValidYet) != 0 {
+	} else if errors.Is(err, jwt.ErrTokenExpired) || errors.Is(err, jwt.ErrTokenNotValidYet) {
 		// Token is either expired or not active yet
 		fmt.Println("Timing is everything")
 	} else {
 		fmt.Println("Couldn't handle this token:", err)
 	}
-	} else {
-		fmt.Println("Couldn't handle this token:", err)
-	}
 
 	// Output: Timing is everything
 }

map_claims.go

@@ -126,16 +126,19 @@ func (m MapClaims) Valid() error {
 	now := TimeFunc().Unix()
 
 	if !m.VerifyExpiresAt(now, false) {
+		// TODO(oxisto): this should be replaced with ErrTokenExpired
 		vErr.Inner = errors.New("Token is expired")
 		vErr.Errors |= ValidationErrorExpired
 	}
 
 	if !m.VerifyIssuedAt(now, false) {
+		// TODO(oxisto): this should be replaced with ErrTokenUsedBeforeIssued
 		vErr.Inner = errors.New("Token used before issued")
 		vErr.Errors |= ValidationErrorIssuedAt
 	}
 
 	if !m.VerifyNotBefore(now, false) {
+		// TODO(oxisto): this should be replaced with ErrTokenNotValidYet
 		vErr.Inner = errors.New("Token is not valid yet")
 		vErr.Errors |= ValidationErrorNotValidYet
 	}

parser_test.go

@@ -4,6 +4,7 @@ import (
 	"crypto"
 	"crypto/rsa"
 	"encoding/json"
+	"errors"
 	"fmt"
 	"reflect"
 	"testing"
@@ -51,6 +52,7 @@ var jwtTestData = []struct {
 	claims        jwt.Claims
 	valid         bool
 	errors        uint32
+	err           []error
 	parser        *jwt.Parser
 	signingMethod jwt.SigningMethod // The method to sign the JWT token for test purpose
 }{
@@ -62,6 +64,7 @@ var jwtTestData = []struct {
 		true,
 		0,
 		nil,
+		nil,
 		jwt.SigningMethodRS256,
 	},
 	{
@@ -71,6 +74,7 @@ var jwtTestData = []struct {
 		jwt.MapClaims{"foo": "bar", "exp": float64(time.Now().Unix() - 100)},
 		false,
 		jwt.ValidationErrorExpired,
+		[]error{jwt.ErrTokenExpired},
 		nil,
 		jwt.SigningMethodRS256,
 	},
@@ -81,6 +85,7 @@ var jwtTestData = []struct {
 		jwt.MapClaims{"foo": "bar", "nbf": float64(time.Now().Unix() + 100)},
 		false,
 		jwt.ValidationErrorNotValidYet,
+		[]error{jwt.ErrTokenNotValidYet},
 		nil,
 		jwt.SigningMethodRS256,
 	},
@@ -91,6 +96,7 @@ var jwtTestData = []struct {
 		jwt.MapClaims{"foo": "bar", "nbf": float64(time.Now().Unix() + 100), "exp": float64(time.Now().Unix() - 100)},
 		false,
 		jwt.ValidationErrorNotValidYet | jwt.ValidationErrorExpired,
+		[]error{jwt.ErrTokenNotValidYet},
 		nil,
 		jwt.SigningMethodRS256,
 	},
@@ -101,6 +107,7 @@ var jwtTestData = []struct {
 		jwt.MapClaims{"foo": "bar"},
 		false,
 		jwt.ValidationErrorSignatureInvalid,
+		[]error{jwt.ErrTokenSignatureInvalid, rsa.ErrVerification},
 		nil,
 		jwt.SigningMethodRS256,
 	},
@@ -111,6 +118,7 @@ var jwtTestData = []struct {
 		jwt.MapClaims{"foo": "bar"},
 		false,
 		jwt.ValidationErrorUnverifiable,
+		[]error{jwt.ErrTokenUnverifiable},
 		nil,
 		jwt.SigningMethodRS256,
 	},
@@ -121,6 +129,7 @@ var jwtTestData = []struct {
 		jwt.MapClaims{"foo": "bar"},
 		false,
 		jwt.ValidationErrorSignatureInvalid,
+		[]error{jwt.ErrTokenSignatureInvalid},
 		nil,
 		jwt.SigningMethodRS256,
 	},
@@ -131,6 +140,7 @@ var jwtTestData = []struct {
 		jwt.MapClaims{"foo": "bar"},
 		false,
 		jwt.ValidationErrorUnverifiable,
+		[]error{jwt.ErrTokenUnverifiable, errKeyFuncError},
 		nil,
 		jwt.SigningMethodRS256,
 	},
@@ -141,6 +151,7 @@ var jwtTestData = []struct {
 		jwt.MapClaims{"foo": "bar"},
 		false,
 		jwt.ValidationErrorSignatureInvalid,
+		[]error{jwt.ErrTokenSignatureInvalid},
 		&jwt.Parser{ValidMethods: []string{"HS256"}},
 		jwt.SigningMethodRS256,
 	},
@@ -151,6 +162,7 @@ var jwtTestData = []struct {
 		jwt.MapClaims{"foo": "bar"},
 		true,
 		0,
+		nil,
 		&jwt.Parser{ValidMethods: []string{"RS256", "HS256"}},
 		jwt.SigningMethodRS256,
 	},
@@ -161,6 +173,7 @@ var jwtTestData = []struct {
 		jwt.MapClaims{"foo": "bar"},
 		false,
 		jwt.ValidationErrorSignatureInvalid,
+		[]error{jwt.ErrTokenSignatureInvalid},
 		&jwt.Parser{ValidMethods: []string{"RS256", "HS256"}},
 		jwt.SigningMethodES256,
 	},
@@ -171,6 +184,7 @@ var jwtTestData = []struct {
 		jwt.MapClaims{"foo": "bar"},
 		true,
 		0,
+		nil,
 		&jwt.Parser{ValidMethods: []string{"HS256", "ES256"}},
 		jwt.SigningMethodES256,
 	},
@@ -181,6 +195,7 @@ var jwtTestData = []struct {
 		jwt.MapClaims{"foo": json.Number("123.4")},
 		true,
 		0,
+		nil,
 		&jwt.Parser{UseJSONNumber: true},
 		jwt.SigningMethodRS256,
 	},
@@ -193,6 +208,7 @@ var jwtTestData = []struct {
 		},
 		true,
 		0,
+		nil,
 		&jwt.Parser{UseJSONNumber: true},
 		jwt.SigningMethodRS256,
 	},
@@ -203,6 +219,7 @@ var jwtTestData = []struct {
 		jwt.MapClaims{"foo": "bar", "exp": json.Number(fmt.Sprintf("%v", time.Now().Unix()-100))},
 		false,
 		jwt.ValidationErrorExpired,
+		[]error{jwt.ErrTokenExpired},
 		&jwt.Parser{UseJSONNumber: true},
 		jwt.SigningMethodRS256,
 	},
@@ -213,6 +230,7 @@ var jwtTestData = []struct {
 		jwt.MapClaims{"foo": "bar", "nbf": json.Number(fmt.Sprintf("%v", time.Now().Unix()+100))},
 		false,
 		jwt.ValidationErrorNotValidYet,
+		[]error{jwt.ErrTokenNotValidYet},
 		&jwt.Parser{UseJSONNumber: true},
 		jwt.SigningMethodRS256,
 	},
@@ -223,6 +241,7 @@ var jwtTestData = []struct {
 		jwt.MapClaims{"foo": "bar", "nbf": json.Number(fmt.Sprintf("%v", time.Now().Unix()+100)), "exp": json.Number(fmt.Sprintf("%v", time.Now().Unix()-100))},
 		false,
 		jwt.ValidationErrorNotValidYet | jwt.ValidationErrorExpired,
+		[]error{jwt.ErrTokenNotValidYet},
 		&jwt.Parser{UseJSONNumber: true},
 		jwt.SigningMethodRS256,
 	},
@@ -233,6 +252,7 @@ var jwtTestData = []struct {
 		jwt.MapClaims{"foo": "bar", "nbf": json.Number(fmt.Sprintf("%v", time.Now().Unix()+100))},
 		true,
 		0,
+		nil,
 		&jwt.Parser{UseJSONNumber: true, SkipClaimsValidation: true},
 		jwt.SigningMethodRS256,
 	},
@@ -245,6 +265,7 @@ var jwtTestData = []struct {
 		},
 		true,
 		0,
+		nil,
 		&jwt.Parser{UseJSONNumber: true},
 		jwt.SigningMethodRS256,
 	},
@@ -257,6 +278,7 @@ var jwtTestData = []struct {
 		},
 		true,
 		0,
+		nil,
 		&jwt.Parser{UseJSONNumber: true},
 		jwt.SigningMethodRS256,
 	},
@@ -269,6 +291,7 @@ var jwtTestData = []struct {
 		},
 		true,
 		0,
+		nil,
 		&jwt.Parser{UseJSONNumber: true},
 		jwt.SigningMethodRS256,
 	},
@@ -281,6 +304,7 @@ var jwtTestData = []struct {
 		},
 		false,
 		jwt.ValidationErrorMalformed,
+		[]error{jwt.ErrTokenMalformed},
 		&jwt.Parser{UseJSONNumber: true},
 		jwt.SigningMethodRS256,
 	},
@@ -293,6 +317,7 @@ var jwtTestData = []struct {
 		},
 		false,
 		jwt.ValidationErrorMalformed,
+		[]error{jwt.ErrTokenMalformed},
 		&jwt.Parser{UseJSONNumber: true},
 		jwt.SigningMethodRS256,
 	},
@@ -325,6 +350,7 @@ func TestParser_Parse(t *testing.T) {
 
 			// Parse the token
 			var token *jwt.Token
+			var ve *jwt.ValidationError
 			var err error
 			var parser = data.parser
 			if parser == nil {
@@ -361,8 +387,7 @@ func TestParser_Parse(t *testing.T) {
 				if err == nil {
 					t.Errorf("[%v] Expecting error. Didn't get one.", data.name)
 				} else {
-
-					ve := err.(*jwt.ValidationError)
+					if errors.As(err, &ve) {
 						// compare the bitfield part of the error
 						if e := ve.Errors; e != data.errors {
 							t.Errorf("[%v] Errors don't match expectation.  %v != %v", data.name, e, data.errors)
@@ -373,6 +398,23 @@ func TestParser_Parse(t *testing.T) {
 						}
 					}
 				}
+			}
+
+			if data.err != nil {
+				if err == nil {
+					t.Errorf("[%v] Expecting error(s). Didn't get one.", data.name)
+				} else {
+					var all = false
+					for _, e := range data.err {
+						all = errors.Is(err, e)
+					}
+
+					if !all {
+						t.Errorf("[%v] Errors don't match expectation.  %v should contain all of %v", data.name, err, data.err)
+					}
+				}
+			}
+
 			if data.valid {
 				if token.Signature == "" {
 					t.Errorf("[%v] Signature is left unpopulated after parsing", data.name)