func()

in jwt/jwt.go [101:185]

• 80 lines of code
• 15 McCabe index (conditional complexity)

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,
		PrivateClaims: js.conf.PrivateClaims,
	}
	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
	}
	if t := js.conf.Expires; t > 0 {
		claimSet.Exp = time.Now().Add(t).Unix()
	}
	if aud := js.conf.Audience; aud != "" {
		claimSet.Aud = aud
	}
	h := *defaultHeader
	h.KeyID = js.conf.PrivateKeyID
	payload, err := jws.Encode(&h, 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, &oauth2.RetrieveError{
			Response: resp,
			Body:     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)
	}
	if js.conf.UseIDToken {
		if tokenRes.IDToken == "" {
			return nil, fmt.Errorf("oauth2: response doesn't have JWT token")
		}
		token.AccessToken = tokenRes.IDToken
	}
	return token, nil
}