protected void validateNonce(final StateData stateData, final IAuthenticationResult authData) {
        final String idToken = authData.idToken();
        if (logger.isDebugEnabled()) {
            logger.debug("idToken: {}", idToken);
        }
        try {
            final JWTClaimsSet claimsSet = JWTParser.parse(idToken).getJWTClaimsSet();
            if (claimsSet == null) {

expiry:
  signingKeys: "3h"
  idTokens: "3h"

  # Options for controlling the logger.
  logger:
    level: "debug"
    format: "text" # can also be "json"

# Default values shown below
oauth2:
  # use ["code", "token", "id_token"] to enable implicit flow for web-only clients
  responseTypes: [ "code", "token", "id_token" ] # also allowed are "token" and "id_token"

	defer resp.Body.Close()
	if resp.StatusCode != http.StatusOK {
		return nil, fmt.Errorf("%s", resp.Status)
	}

	var idpToken JWTToken
	if err = json.NewDecoder(resp.Body).Decode(&idpToken); err != nil {
		return nil, err
	}

	return &credentials.ClientGrantsToken{Token: idpToken.AccessToken, Expiry: idpToken.Expiry}, nil
}

func main() {
	flag.Parse()
	if clientID == "" || clientSecret == "" {
		flag.PrintDefaults()

1. The id_token is an identifier that is hard to guess. For example, a randomly generated string of sufficient length, that the server handling the protected resource can use to lookup the associated authorization information.

- The redirection URI (callback handler) receives the OAuth2 callback, verifies the state parameter, and obtains a Token.
- Using the id_token the callback handler further talks to Google OAuth2 Token URL to obtain an JWT id_token.
- Once obtained the JWT id_token is further sent to STS endpoint i.e MinIO to retrieve temporary credentials.
- Temporary credentials are displayed on the browser upon successful retrieval.

	flag.IntVar(&port, "port", 8080, "Port")
}

func implicitFlowURL(c oauth2.Config, state string) string {
	var buf bytes.Buffer
	buf.WriteString(c.Endpoint.AuthURL)
	v := url.Values{
		"response_type": {"id_token"},
		"response_mode": {"form_post"},
		"client_id":     {c.ClientID},
	}
	if c.RedirectURL != "" {
		v.Set("redirect_uri", c.RedirectURL)
	}
	if len(c.Scopes) > 0 {

    # we can now use the id_token as much as we want to access protected resources.
    tokens = json.loads(id_token_response.text)
    id_token = tokens['id_token']

    response = sts_client.assume_role_with_web_identity(
        RoleArn='arn:aws:iam::123456789012:user/svc-internal-api',
        RoleSessionName='test',
        WebIdentityToken=id_token,
        DurationSeconds=3600
    )

>
> - [**AssumeRole**](https://github.com/minio/minio/blob/master/docs/sts/assume-role.md)
> - [**AD/LDAP**](https://github.com/minio/minio/blob/master/docs/sts/ldap.md)

time="2020-07-12T20:45:50Z" level=info msg="config connector: mock"
time="2020-07-12T20:45:50Z" level=info msg="config connector: local passwords enabled"
time="2020-07-12T20:45:50Z" level=info msg="config response types accepted: [code token id_token]"
time="2020-07-12T20:45:50Z" level=info msg="config using password grant connector: local"
time="2020-07-12T20:45:50Z" level=info msg="config signing keys expire after: 3h0m0s"

```

### Using WebIdentiy API

On another terminal run `web-identity.go` a sample client application which obtains JWT id_tokens from an identity provider, in our case its Keycloak. Uses the returned id_token response to get new temporary credentials from the MinIO server using the STS API call `AssumeRoleWithWebIdentity`.

```