[OAUTH2][KEYCLOAK] Auto refresh token for @nuxtjs/auth module

auth-refresh-token.js

const strategy = 'keycloak'

export default function ({ app }) {

  const { $axios, $auth } = app

  if (!$auth.loggedIn || !$auth.strategies[strategy])
    return

  const options = $auth.strategies.keycloak.options
  let token = $auth.getToken(strategy)
  let refreshToken = $auth.getRefreshToken(strategy)

  if (!token || !refreshToken)
    return

  // calculate timeout before token expiration (75% from expiration time)
  const tokenParsed = decodeToken.call(this, token)
  let refreshInterval = (tokenParsed.exp * 1000 - Date.now()) * 0.75

  // Limit 10 seconds (avoid self attack)
  if (refreshInterval < 10000) {
    refreshInterval = 10000
  }

  // keep refreshing token before expiration time
  let refresher = setInterval(async function () {
    try {
      const response = await $axios.post(options.access_token_endpoint,
        encodeQuery({
          refresh_token: refreshToken.replace(options.token_type + ' ', ''),
          client_id: options.client_id,
          grant_type: 'refresh_token'
        })
      )

      token = options.token_type + ' ' + response.data.access_token
      refreshToken = options.token_type + ' ' + response.data.refresh_token

      $auth.setToken(strategy, token)
      $auth.setRefreshToken(strategy, refreshToken)
      $axios.setToken(token)
    } catch (error) {
      $auth.logout()
      throw new Error('Erro while refreshing token')
    }
  }, refreshInterval)
}

// Properly encode data 
function encodeQuery (queryObject) {
  return Object.keys(queryObject)
    .map(
      key =>
        encodeURIComponent(key) + '=' + encodeURIComponent(queryObject[key])
    )
    .join('&')
}

// Decode JWT token
function decodeToken (str) {
  str = str.split('.')[1];

  str = str.replace('/-/g', '+');
  str = str.replace('/_/g', '/');
  switch (str.length % 4) {
    case 0:
      break;
    case 2:
      str += '==';
      break;
    case 3:
      str += '=';
      break;
    default:
      throw 'Invalid token';
  }

  str = (str + '===').slice(0, str.length + (str.length % 4));
  str = str.replace(/-/g, '+').replace(/_/g, '/');

  str = decodeURIComponent(escape(atob(str)));

  str = JSON.parse(str);
  return str;
}

Hi @robsontenorio, where is let refresher called?

@mejiamanuel57, it's using setInterval() so the function will be executed repeatedly at the defined interval. You don't need to assign the result to a variable to achieve that. It seems that the reference to the result, refresher, isn't used in this code but the reference is probably only needed to stop the code from running (refresher.close()).

Note: You can import some JWT library to decode/encode data. But, just used plain JS.

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