oauth2/google/jwt.go
Andrew Gerrand 397fe76494 google: add support for JWT Access Tokens
This is a new form of authentication for Google services, where instead
of passing a signed claim to obtain a token from the OAuth endpoint, you
present the signed claim *as* the token to the API endpoint.

Fixes #139.
Fixes #140.

Change-Id: Ibf0f168a0ec111660ac08b86121c943fb96e146c
Reviewed-on: https://go-review.googlesource.com/10667
Reviewed-by: David Symonds <dsymonds@golang.org>
Reviewed-by: Dave Day <djd@golang.org>
2015-08-13 22:40:26 +00:00

68 lines
1.8 KiB
Go

// Copyright 2015 The oauth2 Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package google
import (
"crypto/rsa"
"fmt"
"time"
"golang.org/x/oauth2"
"golang.org/x/oauth2/internal"
"golang.org/x/oauth2/jws"
)
// JWTAccessTokenSourceFromJSON uses a Google Developers service account JSON
// key file to read the credentials that authorize and authenticate the
// requests, and returns a TokenSource that does not use any OAuth2 flow but
// instead creates a JWT and sends that as the access token.
// The audience is typically a URL that specifies the scope of the credentials.
func JWTAccessTokenSourceFromJSON(jsonKey []byte, audience string) (oauth2.TokenSource, error) {
cfg, err := JWTConfigFromJSON(jsonKey)
if err != nil {
return nil, fmt.Errorf("google: could not parse JSON key: %v", err)
}
pk, err := internal.ParseKey(cfg.PrivateKey)
if err != nil {
return nil, fmt.Errorf("google: could not parse key: %v", err)
}
ts := &jwtAccessTokenSource{
email: cfg.Email,
audience: audience,
pk: pk,
}
tok, err := ts.Token()
if err != nil {
return nil, err
}
return oauth2.ReuseTokenSource(tok, ts), nil
}
type jwtAccessTokenSource struct {
email, audience string
pk *rsa.PrivateKey
}
func (ts *jwtAccessTokenSource) Token() (*oauth2.Token, error) {
iat := time.Now()
exp := iat.Add(time.Hour)
cs := &jws.ClaimSet{
Iss: ts.email,
Sub: ts.email,
Aud: ts.audience,
Iat: iat.Unix(),
Exp: exp.Unix(),
}
hdr := &jws.Header{
Algorithm: "RS256",
Typ: "JWT",
}
msg, err := jws.Encode(hdr, cs, ts.pk)
if err != nil {
return nil, fmt.Errorf("google: could not encode JWT: %v", err)
}
return &oauth2.Token{AccessToken: msg}, nil
}