OAuth 2.0

OAuth 2.0 (formally specified by RFC 6749) provides an authorization framework which allows users to authorize access to third-party applications. When authorized, the application is issued a token to use as an authentication credential. This has two primary security benefits:

  1. The application does not need to store the user's username and password.
  2. The token can have a restricted scope (for example: read-only access).

These benefits are particularly important for ensuring the security of web applications, making OAuth 2.0 the predominant standard for API authentication.

When using OAuth 2.0 to protect API endpoints, there are three distinct steps that must be performed:

  1. The application requests permission from the user for access to protected resources.
  2. A token is issued to the application, if permission is granted by the user.
  3. The application authenticates using the token to access protected resources.

Issuing Tokens

OAuth2orize, a sibling project to Passport, provides a toolkit for implementing OAuth 2.0 authorization servers.

The authorization process is a complex sequence that involves authenticating both the requesting application and the user, as well as prompting the user for permission, ensuring that enough detail is provided for the user to make an informed decision.

Additionally, it is up to the implementor to determine what limits can be placed on the application regarding scope of access, as well as subsequently enforcing those limits.

As a toolkit, OAuth2orize does not attempt to make implementation decisions. This guide does not cover these issues, but does highly recommend that services deploying OAuth 2.0 have a complete understanding of the security considerations involved.

Authenticating Tokens

OAuth 2.0 provides a framework, in which an arbitrarily extensible set of token types can be issued. In practice, only specific token types have gained widespread use.

Bearer Tokens

Bearer tokens are the most widely issued type of token in OAuth 2.0. So much so, in fact, that many implementations assume that bearer tokens are the only type of token issued.

Bearer tokens can be authenticated using the passport-http-bearer module.

Install

$ npm install passport-http-bearer

Configuration

passport.use(new BearerStrategy(
  function(token, done) {
    User.findOne({ token: token }, function (err, user) {
      if (err) { return done(err); }
      if (!user) { return done(null, false); }
      return done(null, user, { scope: 'read' });
    });
  }
));

The verify callback for bearer tokens accepts the token as an argument. When invoking done, optional info can be passed, which will be set by Passport at req.authInfo. This is typically used to convey the scope of the token, and can be used when making access control checks.

Protect Endpoints

app.get('/api/me',
  passport.authenticate('bearer', { session: false }),
  function(req, res) {
    res.json(req.user);
  });

Specify passport.authenticate() with the bearer strategy to protect API endpoints. Sessions are not typically needed by APIs, so they can be disabled.

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