// fetchToken retrieves a new access token and updates the existing token
// with the newly fetched credentials.
func (c *JWTConfig) FetchToken(existing *Token) (token *Token, err error) {
if existing == nil {
existing = &Token{}
}
claimSet := &jws.ClaimSet{
Iss: c.opts.Email,
Scope: strings.Join(c.opts.Scopes, " "),
Aud: c.aud.String(),
}
if existing.Subject != "" {
claimSet.Sub = existing.Subject
// prn is the old name of sub. Keep setting it
// to be compatible with legacy OAuth 2.0 providers.
claimSet.Prn = existing.Subject
}
payload, err := jws.Encode(defaultHeader, claimSet, c.signature)
if err != nil {
return
}
v := url.Values{}
v.Set("grant_type", defaultGrantType)
v.Set("assertion", payload)
// Make a request with assertion to get a new token.
resp, err := http.DefaultClient.PostForm(c.aud.String(), v)
if err != nil {
return nil, err
}
defer resp.Body.Close()
if resp.StatusCode != 200 {
// TODO(jbd): Provide more context about the response.
return nil, errors.New("Cannot fetch token, response: " + resp.Status)
}
b := &tokenRespBody{}
err = json.NewDecoder(resp.Body).Decode(b)
if err != nil {
return nil, err
}
token = &Token{
AccessToken: b.AccessToken,
TokenType: b.TokenType,
Subject: existing.Subject,
}
if b.IdToken != "" {
// decode returned id token to get expiry
claimSet := &jws.ClaimSet{}
claimSet, err = jws.Decode(b.IdToken)
if err != nil {
return
}
token.Expiry = time.Unix(claimSet.Exp, 0)
return
}
token.Expiry = time.Now().Add(time.Duration(b.ExpiresIn) * time.Second)
return
}
func (js jwtSource) Token() (*oauth2.Token, error) {
pk, err := internal.ParseKey(js.conf.PrivateKey)
if err != nil {
return nil, err
}
hc := oauth2.NewClient(js.ctx, nil)
claimSet := &jws.ClaimSet{
Iss: js.conf.Email,
Scope: strings.Join(js.conf.Scopes, " "),
Aud: js.conf.TokenURL,
}
if subject := js.conf.Subject; subject != "" {
claimSet.Sub = subject
// prn is the old name of sub. Keep setting it
// to be compatible with legacy OAuth 2.0 providers.
claimSet.Prn = subject
}
payload, err := jws.Encode(defaultHeader, claimSet, pk)
if err != nil {
return nil, err
}
v := url.Values{}
v.Set("grant_type", defaultGrantType)
v.Set("assertion", payload)
resp, err := hc.PostForm(js.conf.TokenURL, v)
if err != nil {
return nil, fmt.Errorf("oauth2: cannot fetch token: %v", err)
}
defer resp.Body.Close()
body, err := ioutil.ReadAll(io.LimitReader(resp.Body, 1<<20))
if err != nil {
return nil, fmt.Errorf("oauth2: cannot fetch token: %v", err)
}
if c := resp.StatusCode; c < 200 || c > 299 {
return nil, fmt.Errorf("oauth2: cannot fetch token: %v\nResponse: %s", resp.Status, body)
}
// tokenRes is the JSON response body.
var tokenRes struct {
AccessToken string `json:"access_token"`
TokenType string `json:"token_type"`
IDToken string `json:"id_token"`
ExpiresIn int64 `json:"expires_in"` // relative seconds from now
}
if err := json.Unmarshal(body, &tokenRes); err != nil {
return nil, fmt.Errorf("oauth2: cannot fetch token: %v", err)
}
token := &oauth2.Token{
AccessToken: tokenRes.AccessToken,
TokenType: tokenRes.TokenType,
}
raw := make(map[string]interface{})
json.Unmarshal(body, &raw) // no error checks for optional fields
token = token.WithExtra(raw)
if secs := tokenRes.ExpiresIn; secs > 0 {
token.Expiry = time.Now().Add(time.Duration(secs) * time.Second)
}
if v := tokenRes.IDToken; v != "" {
// decode returned id token to get expiry
claimSet, err := jws.Decode(v)
if err != nil {
return nil, fmt.Errorf("oauth2: error decoding JWT token: %v", err)
}
token.Expiry = time.Unix(claimSet.Exp, 0)
}
return token, nil
}