casbin

Casbin

Note: The plugins and middleware based on Casbin can be found at: https://github.com/casbin

Casbin is a powerful and efficient open-source access control library for Golang projects. It provides support for enforcing authorization based on various access control models.

Table of contents

• Supported models
• How it works?
• Features
• Installation
• Get started
• Documentation
• Policy persistence
• Examples
• Our adopters

Supported models

1. ACL (Access Control List)
2. ACL with superuser
3. ACL without users: especially useful for systems that don't have authentication or user log-ins.
4. ACL without resources: some scenarios may target for a type of resources instead of an individual resource by using permissions like write-article, read-log. It doesn't control the access to a specific article or log.
5. RBAC (Role-Based Access Control)
6. RBAC with resource roles: both users and resources can have roles (or groups) at the same time.
7. RBAC with domains/tenants: users can have different role sets for different domains/tenants.
8. ABAC (Attribute-Based Access Control): syntax sugar like resource.Owner can be used to get the attribute for a resource.
9. RESTful: supports paths like /res/*, /res/:id and HTTP methods like GET, POST, PUT, DELETE.
10. Deny-override: both allow and deny authorizations are supported, deny overrides the allow.
11. Priority: the policy rules can be prioritized like firewall rules.

How it works?

In Casbin, an access control model is abstracted into a CONF file based on the PERM metamodel (Policy, Effect, Request, Matchers). So switching or upgrading the authorization mechanism for a project is just as simple as modifying a configuration. You can customize your own access control model by combining the available models. For example, you can get RBAC roles and ABAC attributes together inside one model and share one set of policy rules.

The most basic and simplest model in Casbin is ACL. ACL's model CONF is:

# Request definition
[request_definition]
r = sub, obj, act

# Policy definition
[policy_definition]
p = sub, obj, act

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

# Matchers
[matchers]
m = r.sub == p.sub && r.obj == p.obj && r.act == p.act

An example policy for ACL model is like:

p, alice, data1, read
p, bob, data2, write

It means:

• alice can read data1
• bob can write data2

Features

What Casbin does:

1. enforce the policy in the classic {subject, object, action} form or a customized form as you defined, both allow and deny authorizations are supported.
2. handle the storage of the access control model and its policy.
3. manage the role-user mappings and role-role mappings (aka role hierarchy in RBAC).
4. support built-in superuser like root or administrator. A superuser can do anything without explict permissions.
5. multiple built-in operators to support the rule matching. For example, keyMatch can map a resource key /foo/bar to the pattern /foo*.

What Casbin does NOT do:

1. authentication (aka verify username and password when a user logs in)
2. manage the list of users or roles. I believe it's more convenient for the project itself to manage these entities. Users usually have their passwords, and Casbin is not designed as a password container. However, Casbin stores the user-role mapping for the RBAC scenario.

Installation

go get github.com/casbin/casbin

Get started

1. New a Casbin enforcer with a model file and a policy file:

   e := casbin.NewEnforcer("path/to/model.conf", "path/to/policy.csv")
   

Note: you can also initialize an enforcer with policy in DB instead of file, see Persistence section for details.

1. Add an enforcement hook into your code right before the access happens:

   sub := "alice" // the user that wants to access a resource.
   obj := "data1" // the resource that is going to be accessed.
   act := "read" // the operation that the user performs on the resource.
   
   if e.Enforce(sub, obj, act) == true {
       // permit alice to read data1
   } else {
       // deny the request, show an error
   }
   

2. Besides the static policy file, Casbin also provides API for permission management at run-time. For example, You can get all the roles assigned to a user as below:

   roles := e.GetRoles("alice")
   

Note: we provide two sets of APIs to manage permissions:

• Management API: the primitive API that provides full support for Casbin policy management.
• RBAC API: a more friendly API for RBAC. This API is a subset of Management API. The RBAC users could use this API to simplify the code.

1. Please refer to the _test.go files for more usage.

Documentation

See: Our Wiki

Policy persistence

In Casbin, the policy storage is implemented as an adapter (aka middleware for Casbin). To keep light-weight, we don't put adapter code in the main library. A complete list of Casbin adapters is provided as below. Any 3rd-party contribution on a new adapter is welcomed, please inform us and I will put it in this list:)

For details of adapters, please refer to the documentation: https://github.com/casbin/casbin/wiki/Policy-persistence

Examples

Our adopters

Web frameworks

• Beego: An open-source, high-performance web framework for Go, via built-in plugin: plugins/authz
• Caddy: Fast, cross-platform HTTP/2 web server with automatic HTTPS, via plugin: caddy-authz
• Gin: A HTTP web framework featuring a Martini-like API with much better performance, via plugin: authz
• Revel: A high productivity, full-stack web framework for the Go language, via plugin: revel-authz
• Echo: High performance, minimalist Go web framework, via plugin: echo-authz (thanks to @xqbumu)
• Iris: The fastest web framework for Go in (THIS) Earth. HTTP/2 Ready-To-GO, via plugin: casbin (thanks to @hiveminded)
• Negroni: Idiomatic HTTP Middleware for Golang, via plugin: negroni-authz
• Tango: Micro & pluggable web framework for Go, via plugin: authz
• Chi: A lightweight, idiomatic and composable router for building HTTP services, via plugin: chi-authz
• Macaron: A high productive and modular web framework in Go, via plugin: authz
• DotWeb: Simple and easy go web micro framework, via plugin: authz
• Baa: An express Go web framework with routing, middleware, dependency injection and http context, via plugin: authz

Others

• Docker: The world's leading software container platform, via plugin: casbin-authz-plugin (recommended by Docker)
• pybbs-go: A simple BBS with fine-grained permission management based on Beego, via direct integration
• Zenpress: A CMS system written in Golang, via direct integration

License

This project is licensed under the Apache 2.0 license.

Contact

If you have any issues or feature requests, please contact us. PR is welcomed.

• https://github.com/casbin/casbin/issues
• hsluoyz@gmail.com
• Tencent QQ group: 546057381