egg-cancan

Cancancan like authorization plugin for Egg.js

This plugin is our best practice from we developing yuque.com.

Install

$ npm i egg-cancan --save

Usage

// {app_root}/config/plugin.js
exports.cancan = {
  enable: true,
  package: 'egg-cancan',
};

Configuration

// {app_root}/config/config.default.js
exports.cancan = {
// method name of current logined user instance
  contextUserMethod: 'user',
  // Enable disable Ability check result cache
  cache: false,
  // Enable log authorize check result
  log: false,
};

Defining Abilities

You must create app/ability.js file

The Ability class is where all user permissions are defined. An example class looks like this.

'use strict';

const { BaseAbility } = require('egg-cancan');

class Ability extends BaseAbility {
  constructor(ctx, user) {
    super(ctx, user)
  }

  async rules(action, obj, options = {}) {
    const { type } = options;

    if (type === 'topic') {
      if (action === 'update') {
        return await this.canUpdateTopic(obj);
      }

      if (action === 'delete') {
        return await this.canDeleteTopic(obj);
      }
    }

    return true;
  }

  async canUpdateTopic(obj) {
    if (topic.user_id === this.user_id) return true;
    return false;
  }

  async canDeleteTopic(obj) {
    if (this.user.admin) return true;
    return false;
  }
}

Action alias

Cache check result in same Context

Ability support cache Ability check result in ctx, you can enable it by change config/config.default.js

exports.cancan = {
  // defalut is disabled
  cache: true,
};

When you enable that, you call can method will hit cache:

ctx.can('read', user);
- check cache in ability._cache
    found -> return
  not exist ->
    execute `rules` to real check
    write to _cache
    return

Its use action + obj + options stringify as default cache key:

ability.cacheKey('read', { id: 1 }, { type: 'user' });
=> 'read-{id:1}-{type:"user"}'

You can rewrite it by override the cacheKey method, for example:

class Ability extends BaseAbility {
  cacheKey(action, obj, options) {
    return [action, obj.cacheKey, options.type].join(':');
  }
}

Check Abilities

The ctx.can method:

can = await ctx.can('create', topic, { type: 'topic' });
can = await ctx.can('read', topic, { type: 'topic' });
can = await ctx.can('update', topic, { type: 'topic' });
can = await ctx.can('delete', topic, { type: 'topic' });

can = await ctx.can('update', user, { type: 'user' });

// For egg-sequelize model instance, not need pass `:type` option
const topic = await ctx.model.Topic.findById(...);
can = await ctx.can('update', topic);

The ctx.authorize method:

await ctx.authorize('read', topic);
// when permission is ok, not happend
// when no permission, will throw CanCanAccessDenied

Handle Unauthorized Access

If the ctx.authorize check fails, a CanCanAccessDenied error will be throw. You can catch this and modify its behavior:

Add new file: app/middleware/handle_authorize.js

module.exports = () => {
  return async handleAuthorize(next) {
    try {
      await next();
    } catch (e) {
      if (e.name === 'CanCanAccessDenied') {
        this.status = 403;
        this.body = 'Access Denied';
      } else {
        throw e;
      }
    }
  }
}

And enable this middleware by modify config/config.default.js:

exports.middleware = [
  ...
  'handleAuthorize',
  ...
];

Testing your abilities

When you wrote app/ability.js, you may need to write test case.

• egg-sequelize
• factory-girl-sequelize

Create a test file: test/ability.test.js

'use strict';

describe('Ability', () => {
  let allow, user, ability, anonymousAbility;

  beforeAll(async () => {
    user = await create('user');
    ability = new app.Ability(ctx, user);
  });

  describe('Topic', () => {
    describe('Anonymous', () => {
      it('should work', async () => {
        const topic = await create('topic');
        allow = await ability.can('create', topic);
        assert.equal(true, allow);
        allow = await ability.can('read', topic);
        assert.equal(true, allow);
        allow = await ability.can('update', topic);
        assert.equal(false, allow);
        allow = await ability.can('destroy', topic);
        assert.equal(false, allow);
      });
    });

    describe('Author', () => {
      it('should work', async () => {
        const topic = await create('topic', { user_id: user.id });
        allow = await ability.can('create', topic);
        assert.equal(true, allow);
        allow = await ability.can('read', topic);
        assert.equal(true, allow);
        allow = await ability.can('update', topic);
        assert.equal(true, allow);
        allow = await ability.can('destroy', topic);
        assert.equal(true, allow);
      });
    })
  });
});

License

MIT