Casbin Middleware for Hono

This is a third-party Casbin middleware for Hono.

This middleware can be used to enforce authorization policies defined using Casbin in your Hono routes.

Installation

npm i hono @hono/casbin casbin

Configuration

Before using the middleware, you must set up your Casbin model and policy files.

For details on how to write authorization policies and other information, please refer to the Casbin documentation.

Example model.conf

[request_definition]
r = sub, obj, act

[policy_definition]
p = sub, obj, act

[policy_effect]
e = some(where (p.eft == allow))

[matchers]
m = r.sub == p.sub && keyMatch(r.obj, p.obj) && (r.act == p.act || p.act == "*")

Example policy.csv

p, alice, /dataset1/*, *
p, bob, /dataset1/*, GET

Usage with Basic HTTP Authentication

You can perform authorization control after Basic authentication by combining it with basicAuthorizer. (The client needs to send Authentication: Basic {Base64Encoded(username:password)}.)

Let's look at an example. Use the model and policy files from the Configuration section. You can implement a scenario where alice and bob have different permissions. Alice has access to all methods on /dataset1/test, while Bob has access only to the GET method.

import { Hono } from 'hono'
import { basicAuth } from 'hono/basic-auth'
import { newEnforcer } from 'casbin'
import { casbin } from '@hono/casbin'
import { basicAuthorizer } from '@hono/casbin/helper'

const app = new Hono()
app.use('*',
  basicAuth(
    {
      username: 'alice', // alice has full access to /dataset1/test
      password: 'password',
    },
    {
      username: 'bob', // bob cannot post to /dataset1/test
      password: 'password',
    }
  ),
  casbin({
    newEnforcer: newEnforcer('examples/model.conf', 'examples/policy.csv'),
    authorizer: basicAuthorizer
  })
)
app.get('/dataset1/test', (c) => c.text('dataset1 test')) // alice and bob can access /dataset1/test
app.post('/dataset1/test', (c) => c.text('dataset1 test')) // Only alice can access /dataset1/test

Usage with JWT Authentication

By using jwtAuthorizer, you can perform authorization control after JWT authentication. By default, jwtAuthorizer uses the sub in the JWT payload as the username.

import { Hono } from 'hono'
import { jwt } from 'hono/jwt'
import { newEnforcer } from 'casbin'
import { casbin } from '@hono/casbin'
import { jwtAuthorizer } from '@hono/casbin/helper'

const app = new Hono()
app.use('*',
  jwt({
    secret: 'it-is-very-secret',
  }),
  casbin({
    newEnforcer: newEnforcer('examples/model.conf', 'examples/policy.csv'),
    authorizer: jwtAuthorizer
  })
)
app.get('/dataset1/test', (c) => c.text('dataset1 test')) // alice and bob can access /dataset1/test
app.post('/dataset1/test', (c) => c.text('dataset1 test')) // Only alice can access /dataset1/test

Of course, you can use claims other than the sub claim. Specify the key as a user-friendly name and the value as the JWT claim name. The Payload key used for evaluation in the enforcer will be the value.

const claimMapping = {
  username: 'username',
}
// ...
casbin({
  newEnforcer: newEnforcer('examples/model.conf', 'examples/policy.csv'),
  authorizer: (c, e) => jwtAuthorizer(c, e, claimMapping)
})

Usage with Customized Authorizer

You can also use a customized authorizer function to handle the authorization logic.

import { Hono } from 'hono'
import { newEnforcer } from 'casbin'
import { casbin } from '@hono/casbin'

const app = new Hono()
app.use('*', casbin({
  newEnforcer: newEnforcer('path-to-your-model.conf', 'path-to-your-policy.csv'),
  authorizer: async (c, enforcer) => {
    const { user, path, method } = c
    return await enforcer.enforce(user, path, method)
  }
}))

Author

sugar-cat https://github.com/sugar-cat7