jwx

Implementation of various JWx technologies

Status

Done

PR/issues welcome.

Package name	Notes
jwt	RFC 7519
jwk	RFC 7517 + RFC 7638
jwa	RFC 7518
jws	RFC 7515
jwe	RFC 7516

In progress:

• jwe - more algorithms

Why?

My goal was to write a server that heavily uses JWK and JWT. At first glance the libraries that already exist seemed sufficient, but soon I realized that

1. To completely implement the protocols, I needed the entire JWT, JWK, JWS, JWE (and JWA, by necessity).
2. Most of the libraries that existed only deal with a subset of the various JWx specifications that were necessary to implement their specific needs

For example, a certain library looks like it had most of JWS, JWE, JWK covered, but then it lacked the ability to include private claims in its JWT responses. Another library had support of all the private claims, but completely lacked in its flexibility to generate various different response formats.

Because I was writing the server side (and the client side for testing), I needed the entire JOSE toolset to properly implement my server, and they needed to be flexible enough to fulfill the entire spec that I was writing.

So here's go-jwx. This library is extensible, customizable, and hopefully well organized to the point that it is easy for you to slice and dice it.

As of this writing (Nov 2015), it's still lacking a few of the algorithms for JWE that are described in JWA (which I believe to be less frequently used), but in general you should be able to do pretty much everything allowed in the specifications.

Notes for users of pre-1.0.0 release

The API has been reworked quite substantially between pre- and post 1.0.0 releases. Please check out the Changes file (or the diff, if you are into that sort of thing)

Synopsis

JWT

See the examples here as well: https://github.com/lestrrat-go/jwx/jwt

func ExampleJWT() {
  const aLongLongTimeAgo = 233431200

  t := jwt.New()
  t.Set(jwt.SubjectKey, `https://github.com/lestrrat-go/jwx/jwt`)
  t.Set(jwt.AudienceKey, `Golang Users`)
  t.Set(jwt.IssuedAtKey, time.Unix(aLongLongTimeAgo, 0))
  t.Set(`privateClaimKey`, `Hello, World!`)

  buf, err := json.MarshalIndent(t, "", "  ")
  if err != nil {
    fmt.Printf("failed to generate JSON: %s\n", err)
    return
  }

  fmt.Printf("%s\n", buf)
  fmt.Printf("aud -> '%s'\n", t.Audience())
  fmt.Printf("iat -> '%s'\n", t.IssuedAt().Format(time.RFC3339))
  if v, ok := t.Get(`privateClaimKey`); ok {
    fmt.Printf("privateClaimKey -> '%s'\n", v)
  }
  fmt.Printf("sub -> '%s'\n", t.Subject())

  key, err := rsa.GenerateKey(rand.Reader, 2048)
  if err != nil {
    log.Printf("failed to generate private key: %s", err)
    return
  }

  {
    // Signing a token (using raw rsa.PrivateKey)
    signed, err := jwt.Sign(t, jwa.RS256, key)
    if err != nil {
      log.Printf("failed to sign token: %s", err)
      return
    }
    _ = signed
  }

  {
    // Signing a token (using JWK)
    jwkKey, err := jwk.New(key)
    if err != nil {
      log.Printf("failed to create JWK key: %s", err)
      return
    }

    signed, err := jwt.Sign(t, jwa.RS256, jwkKey)
    if err != nil {
      log.Printf("failed to sign token: %s", err)
      return
    }
    _ = signed
  }
}

JWT (with OpenID claims)

jwt package can work with token types other than the default one. For OpenID claims, use the token created by openid.New(), or use the jwt.WithOpenIDClaims(). If you need to use other specialized claims, use jwt.WithToken() to specify the exact token type

func Example_openid() {
  const aLongLongTimeAgo = 233431200

  t := openid.New()
  t.Set(jwt.SubjectKey, `https://github.com/lestrrat-go/jwx/jwt`)
  t.Set(jwt.AudienceKey, `Golang Users`)
  t.Set(jwt.IssuedAtKey, time.Unix(aLongLongTimeAgo, 0))
  t.Set(`privateClaimKey`, `Hello, World!`)

  addr := openid.NewAddress()
  addr.Set(openid.AddressPostalCodeKey, `105-0011`)
  addr.Set(openid.AddressCountryKey, `日本`)
  addr.Set(openid.AddressRegionKey, `東京都`)
  addr.Set(openid.AddressLocalityKey, `港区`)
  addr.Set(openid.AddressStreetAddressKey, `芝公園 4-2-8`)
  t.Set(openid.AddressKey, addr)

  buf, err := json.MarshalIndent(t, "", "  ")
  if err != nil {
    fmt.Printf("failed to generate JSON: %s\n", err)
    return
  }
  fmt.Printf("%s\n", buf)

  t2, err := jwt.ParseBytes(buf, jwt.WithOpenIDClaims())
  if err != nil {
    fmt.Printf("failed to parse JSON: %s\n", err)
    return
  }
  if _, ok := t2.(openid.Token); !ok {
    fmt.Printf("using jwt.WithOpenIDClaims() creates an openid.Token instance")
    return
  }
}

JWK

See the examples here as well: https://godoc.org/github.com/lestrrat-go/jwx/jwk#pkg-examples

Create a JWK file from RSA public key:

import(
  "crypto/rand"
  "crypto/rsa"
  "encoding/json"
  "log"
  "os"

  "github.com/lestrrat-go/jwx/jwk"
)

func main() {
  privkey, err := rsa.GenerateKey(rand.Reader, 2048)
  if err != nil {
    log.Printf("failed to generate private key: %s", err)
    return
  }

  key, err := jwk.New(&privkey.PublicKey)
  if err != nil {
    log.Printf("failed to create JWK: %s", err)
    return
  }

  jsonbuf, err := json.MarshalIndent(key, "", "  ")
  if err != nil {
    log.Printf("failed to generate JSON: %s", err)
    return
  }

  os.Stdout.Write(jsonbuf)
}

Parse and use a JWK key:

import (
  "encoding/json"
  "log"

  "github.com/lestrrat-go/jwx/jwk"
)

func main() {
  set, err := jwk.FetchHTTP("https://www.googleapis.com/oauth2/v3/certs")
  if err != nil {
    log.Printf("failed to parse JWK: %s", err)
    return
  }

  // Key setss can be serialized back to JSON
  {
    jsonbuf, err := json.Marshal(set)
    if err != nil {
      log.Printf("failed to marshal key set into JSON: %s", err)
      return
    }
    log.Printf("%s", jsonbuf)
  }

  for it := set.Iterate(context.Background()); it.Next(context.Background()); {
    pair := it.Pair()
    key := pair.Value.(jwk.Key)

    var rawkey interface{} // This is the raw key, like *rsa.PrivateKey or *ecdsa.PrivateKey
    if err := key.Raw(&rawkey); err != nil {
      log.Printf("failed to create public key: %s", err)
      return
    }
    // Use rawkey for jws.Verify() or whatever.
    _ = rawkey

    // You can creatre jwk.Key from a raw key, too
    fromRawKey, err := jwk.New(rawkey)


    // Keys can be serialized back to JSON
    jsonbuf, err := json.Marshal(key)
    if err != nil {
      log.Printf("failed to marshal key into JSON: %s", err)
      return
    }
    log.Printf("%s", jsonbuf)

    // If you know the underlying Key type (RSA, EC, Symmetric), you can
    // create an empy instance first
    //    key := jwk.NewRSAPrivateKey()
    // ..and then use json.Unmarshal
    //    json.Unmarshal(key, jsonbuf)
    //
    // but if you don't know the type first, you have an abstract type
    // jwk.Key, which can't be used as the first argument to json.Unmarshal
    //
    // In this case, use jwk.Parse()
    fromJsonKey, err := jwk.ParseBytes(jsonbuf)
    if err != nil {
      log.Printf("failed to parse json: %s", err)
      return
    }
    _ = fromJsonKey
    _ = fromRawKey
  }
}

JWS

See also VerifyWithJWK and VerifyWithJKU

import(
  "crypto/rand"
  "crypto/rsa"
  "log"

  "github.com/lestrrat-go/jwx/jwa"
  "github.com/lestrrat-go/jwx/jws"
)

func main() {
  privkey, err := rsa.GenerateKey(rand.Reader, 2048)
  if err != nil {
    log.Printf("failed to generate private key: %s", err)
    return
  }

  buf, err := jws.Sign([]byte("Lorem ipsum"), jwa.RS256, privkey)
  if err != nil {
    log.Printf("failed to created JWS message: %s", err)
    return
  }

  // When you received a JWS message, you can verify the signature
  // and grab the payload sent in the message in one go:
  verified, err := jws.Verify(buf, jwa.RS256, &privkey.PublicKey)
  if err != nil {
    log.Printf("failed to verify message: %s", err)
    return
  }

  log.Printf("signed message verified! -> %s", verified)
}

Supported signature algorithms:

Algorithm	Supported?	Constant in go-jwx
HMAC using SHA-256	YES	jwa.HS256
HMAC using SHA-384	YES	jwa.HS384
HMAC using SHA-512	YES	jwa.HS512
RSASSA-PKCS-v1.5 using SHA-256	YES	jwa.RS256
RSASSA-PKCS-v1.5 using SHA-384	YES	jwa.RS384
RSASSA-PKCS-v1.5 using SHA-512	YES	jwa.RS512
ECDSA using P-256 and SHA-256	YES	jwa.ES256
ECDSA using P-384 and SHA-384	YES	jwa.ES384
ECDSA using P-521 and SHA-512	YES	jwa.ES512
RSASSA-PSS using SHA256 and MGF1-SHA256	YES	jwa.PS256
RSASSA-PSS using SHA384 and MGF1-SHA384	YES	jwa.PS384
RSASSA-PSS using SHA512 and MGF1-SHA512	YES	jwa.PS512

JWE

See the examples here as well: https://godoc.org/github.com/lestrrat-go/jwx/jwe#pkg-examples

import(
  "crypto/rand"
  "crypto/rsa"
  "log"

  "github.com/lestrrat-go/jwx/jwa"
  "github.com/lestrrat-go/jwx/jwe"
)

func main() {
  privkey, err := rsa.GenerateKey(rand.Reader, 2048)
  if err != nil {
    log.Printf("failed to generate private key: %s", err)
    return
  }

  payload := []byte("Lorem Ipsum")

  encrypted, err := jwe.Encrypt(payload, jwa.RSA1_5, &privkey.PublicKey, jwa.A128CBC_HS256, jwa.NoCompress)
  if err != nil {
    log.Printf("failed to encrypt payload: %s", err)
    return
  }

  decrypted, err := jwe.Decrypt(encrypted, jwa.RSA1_5, privkey)
  if err != nil {
    log.Printf("failed to decrypt: %s", err)
    return
  }

  if string(decrypted) != "Lorem Ipsum" {
    log.Printf("WHAT?!")
    return
  }
}

Supported key encryption algorithm:

Algorithm	Supported?	Constant in go-jwx
RSA-PKCS1v1.5	YES	jwa.RSA1_5
RSA-OAEP-SHA1	YES	jwa.RSA_OAEP
RSA-OAEP-SHA256	YES	jwa.RSA_OAEP_256
AES key wrap (128)	YES	jwa.A128KW
AES key wrap (192)	YES	jwa.A192KW
AES key wrap (256)	YES	jwa.A256KW
Direct encryption	NO	jwa.DIRECT
ECDH-ES	YES (1)	jwa.ECDH_ES
ECDH-ES + AES key wrap (128)	YES	jwa.ECDH_ES_A128KW
ECDH-ES + AES key wrap (192)	YES	jwa.ECDH_ES_A192KW
ECDH-ES + AES key wrap (256)	YES	jwa.ECDH_ES_A256KW
AES-GCM key wrap (128)	YES	jwa.A128GCMKW
AES-GCM key wrap (192)	YES	jwa.A192GCMKW
AES-GCM key wrap (256)	YES	jwa.A256GCMKW
PBES2 + HMAC-SHA256 + AES key wrap (128)	YES	jwa.PBES2_HS256_A128KW
PBES2 + HMAC-SHA384 + AES key wrap (192)	YES	jwa.PBES2_HS384_A192KW
PBES2 + HMAC-SHA512 + AES key wrap (256)	YES	jwa.PBES2_HS512_A256KW

Note 1: Single-recipient only

Supported content encryption algorithm:

Algorithm	Supported?	Constant in go-jwx
AES-CBC + HMAC-SHA256 (128)	YES	jwa.A128CBC_HS256
AES-CBC + HMAC-SHA384 (192)	YES	jwa.A192CBC_HS384
AES-CBC + HMAC-SHA512 (256)	YES	jwa.A256CBC_HS512
AES-GCM (128)	YES	jwa.A128GCM
AES-GCM (192)	YES	jwa.A192GCM
AES-GCM (256)	YES	jwa.A256GCM

PRs welcome to support missing algorithms!

Configuring JSON Parsing

If you want to parse numbers in the incoming JSON objects as json.Number instead of floats, you can use the following call to globally affect the behavior of JSON parsing.

func init()
  jwx.DecoderSettings(jwx.WithUseNumber(true))
}

Do be aware that this has global effect. All code that calls in to encoding/json within jwx will use your settings.

Other related libraries:

• https://github.com/dgrijalva/jwt-go
• https://github.com/square/go-jose
• https://github.com/coreos/oidc
• https://golang.org/x/oauth2

Contributions

PRs welcome!

Credits

• Work on this library was generously sponsored by HDE Inc (https://www.hde.co.jp)
• Lots of code, especially JWE was taken from go-jose library (https://github.com/square/go-jose)