Express-Authz

Express-Authz is an authorization middleware for Express, it's based on Node-Casbin: https://github.com/casbin/node-casbin.

Installation

use casbin v2.x

npm install casbin@2 casbin-express-authz@1 --save

use casbin v3.x

npm install casbin@3 casbin-express-authz@2 --save

or you can simply use,

npm install express casbin casbin-express-authz --save

Usage with Basic HTTP Authentication

By default casbin-authz supports HTTP Basic Authentication of the form Authentication: Basic {Base64Encoded(username:password)}

Usage with Other HTTP Authentication

To use other HTTP Authentication like Bearer/Digest you can use a custom middleware to define the res.locals.username variable and casbin-authz will automatically pick up the value from the variable.

const { newEnforcer } = require('casbin');
const express = require('express');
const { authz } = require('casbin-express-authz');

const app = express();
const enforcer = await newEnforcer('examples/authz_model.conf', 'examples/authz_policy.csv');

// set userinfo
app.use((req, res, next) => {
  res.locals.username = getUsernameFromToken(); // Your custom function for retrieving username
  next();
});

// use authz middleware
app.use(authz({ newEnforcer: enforcer }));

// response
app.use((req, res, next) => {
  res.status(200).json({ status: 'OK' });
});

app.listen(3000);

Usage with customized authorizer

This package provides BasicAuthorizer, it uses HTTP Basic Authentication as the authentication method. If you want to use another authentication method like OAuth, you needs to implement Authorizer as below:

import { Enforcer, newEnforcer } from 'casbin';
import { authz, Authorizer } from 'casbin-express-authz';
import * as express from 'express';

const app = express();

class MyAuthorizer implements Authorizer {
  private e: Enforcer;

  constructor(e: Enforcer) {
    this.e = e;
  }

  checkPermission(): Promise<boolean> {
    // do something
    return true;
  }
}
const e = await newEnforcer('examples/authz_model.conf', 'examples/authz_policy.csv');

app.use(
  authz({
    newEnforcer: e,
    authorizer: new MyAuthorizer(e),
  })
);

app.listen(3000);

Usage with customized authorizer class

When the authorizer needs the request and response object to check the permission, one can pass the constructor of the customized Authorizer class instead of an instance.

import { Enforcer, newEnforcer } from 'casbin';
import { authz, AuthorizerConstructor } from 'casbin-express-authz';
import { Request, Response } from 'express';

const app = express();

class MyAuthorizer implements Authorizer {
  private e: Enforcer;
  private req: Request;
  private res: Respons;

  constructor(req:Request, res:Respons, e: Enforcer) {
    this.e = e;
    this.req = req
    this.res = res
  }

  checkPermission(): Promise<boolean> {
    // do something
    return true;
  }
}
const e = await newEnforcer('examples/authz_model.conf', 'examples/authz_policy.csv');

app.use(
  authz({
    newEnforcer: e,
    authorizer: MyAuthorizer,
  })
);

app.listen(3000);

How to control the access

The authorization determines a request based on {subject, object, action}, which means what subject can perform what action on what object. In this plugin, the meanings are:

1. subject: the logged-on user name
2. object: the URL path for the web resource like "dataset1/item1"
3. action: HTTP method like GET, POST, PUT, DELETE, or the high-level actions you defined like "read-file", "write-blog"

For how to write authorization policy and other details, please refer to the Casbin's documentation.

Getting Help

• Node-Casbin

License

This project is licensed under the Apache 2.0 license.