jwt (JSON Web Token for Go)

About

This package is a JWT signer, verifier and validator for Go (or Golang).

Although there are many JWT packages out there for Go, many lack support for some signing, verifying or validation methods and, when they don't, they're overcomplicated. This package tries to mimic the ease of use from Node JWT library's API while following the Effective Go guidelines.

Support for JWE isn't provided (not yet but is in the roadmap, see #17). Instead, JWS is used, narrowed down to the JWT specification.

Supported signing methods

	SHA-256	SHA-384	SHA-512
HMAC	✔️	✔️	✔️
RSA	✔️	✔️	✔️
RSA-PSS	✔️	✔️	✔️
ECDSA	✔️	✔️	✔️
EdDSA	➖	➖	✔️

Important

Branch master is unstable, always use tagged versions. That way it is possible to differentiate pre-release tags from production ones. In other words, API changes all the time in master. It's a place for public experiment. Thus, make use of the latest stable version via Go modules.

Usage

Full documentation here.

Installing

Important

For Go 1.11, make sure the environment variable GO111MODULE is set as on when running the install command.

$ go get -u github.com/gbrlsnchs/jwt/v3

Signing

import (
	"time"

	"github.com/gbrlsnchs/jwt/v3"
)

type CustomPayload struct {
	jwt.Payload
	Foo string `json:"foo,omitempty"`
	Bar int    `json:"bar,omitempty"`
}

var hs = jwt.NewHS256([]byte("secret"))

func main() {
	now := time.Now()
	pl := CustomPayload{
		Payload: jwt.Payload{
			Issuer:         "gbrlsnchs",
			Subject:        "someone",
			Audience:       jwt.Audience{"https://golang.org", "https://jwt.io"},
			ExpirationTime: jwt.NumericDate(now.Add(24 * 30 * 12 * time.Hour)),
			NotBefore:      jwt.NumericDate(now.Add(30 * time.Minute)),
			IssuedAt:       jwt.NumericDate(now),
			JWTID:          "foobar",
		},
		Foo: "foo",
		Bar: 1337,
	}

	token, err := jwt.Sign(pl, hs)
	if err != nil {
		// ...
	}

	// ...
}

Verifying

import "github.com/gbrlsnchs/jwt/v3"

type CustomPayload struct {
	jwt.Payload
	Foo string `json:"foo,omitempty"`
	Bar int    `json:"bar,omitempty"`
}

var hs = jwt.NewHS256([]byte("secret"))

func main() {
	// ...

	var pl CustomPayload
	hd, err := jwt.Verify(token, hs, &pl)
	if err != nil {
		// ...
	}

	// ...
}

Other use case examples

Setting "cty" and "kid" claims

The "cty" and "kid" claims can be set by passing options to the jwt.Sign function:

import (
	"time"

	"github.com/gbrlsnchs/jwt/v3"
)

var hs = jwt.NewHS256([]byte("secret"))

func main() {
	pl := jwt.Payload{
		Subject:  "gbrlsnchs",
		Issuer:   "gsr.dev",
		IssuedAt: jwt.NumericDate(time.Now()),
	}

	token, err := jwt.Sign(pl, hs, jwt.ContentType("JWT"), jwt.KeyID("my_key"))
	if err != nil {
		// ...
	}

	// ...
}

Validating claims

import (
	"time"

	"github.com/gbrlsnchs/jwt/v3"
)

type CustomPayload struct {
	jwt.Payload
	Foo string `json:"foo,omitempty"`
	Bar int    `json:"bar,omitempty"`
}

var hs = jwt.NewHS256([]byte("secret"))

func main() {
	// ...

	var (
		now = time.Now()
		aud = jwt.Audience{"https://golang.org"}

		// Validate claims "iat", "exp" and "aud".
		iatValidator = jwt.IssuedAtValidator(now)
		expValidator = jwt.ExpirationTimeValidator(now)
		audValidator = jwt.AudienceValidator(aud)

		// Use jwt.ValidatePayload to build a jwt.VerifyOption.
		// Validators are run in the order informed.
		pl              CustomPayload
		validatePayload = jwt.ValidatePayload(&pl.Payload, iatValidator, expValidator, audValidator)
	)

	hd, err := jwt.Verify(token, hs, &pl, validatePayload)
	if err != nil {
		// ...
	}

	// ...
}

Validating "alg" before verifying

For validating the "alg" field in a JOSE header before verification, the jwt.ValidateHeader option must be passed to jwt.Verify.

import "github.com/gbrlsnchs/jwt/v3"

var hs = jwt.NewHS256([]byte("secret"))

func main() {
	// ...

	var pl jwt.Payload
	if _, err := jwt.Verify(token, hs, &pl, jwt.ValidateHeader); err != nil {
		// ...
	}

	// ...
}

Using an Algorithm resolver

import (
	"errors"

	"github.com/gbrlsnchs/jwt/v3"
	"github.com/gbrlsnchs/jwt/v3/jwtutil"
)

var (
	// ...

	rs256 = jwt.NewRS256(jwt.RSAPublicKey(myRSAPublicKey))
	es256 = jwt.NewES256(jwt.ECDSAPublicKey(myECDSAPublicKey))
)

func main() {
	rv := &jwtutil.Resolver{New: func(hd jwt.Header) (jwt.Algorithm, error) {
		switch hd.KeyID {
		case "foo":
			return rs256, nil
		case "bar":
			return es256, nil
		default:
			return nil, errors.New(`invalid "kid"`)
		}
	}}
	var pl jwt.Payload
	if _, err := jwt.Verify(token, rv, &pl); err != nil {
		// ...
	}

	// ...
}

Contributing

How to help

• For bugs and opinions, please open an issue
• For pushing changes, please open a pull request