Casbin

News: still worry about how to write the correct Casbin policy? Casbin online editor is coming to help! Try it at: http://casbin.org/editor/

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.

All the languages supported by Casbin:

Casbin	jCasbin	node-Casbin	PHP-Casbin
production-ready	production-ready	production-ready	production-ready

Table of contents

• Supported models
• How it works?
• Features
• Installation
• Documentation
• Online editor
• Tutorials
• Get started
• Policy management
• Policy persistence
• Policy consistence between multiple nodes
• Role manager
• Multi-threading
• Benchmarks
• Examples
• How to use Casbin as a service?
• 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

We also support multi-line mode by appending '\' in the end:

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

Further more, if you are using ABAC, you can try operator in like following in Casbin golang edition (jCasbin and Node-Casbin are not supported yet):

# Matchers
[matchers]
m = r.obj == p.obj && r.act == p.act || r.obj in ('data2', 'data3')

But you SHOULD make sure that the length of the array is MORE than 1, otherwise there will cause it to panic.

For more operators, you may take a look at govaluate

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

Documentation

https://casbin.org/docs/en/overview

Online editor

You can also use the online editor (http://casbin.org/editor/) to write your Casbin model and policy in your web browser. It provides functionality such as syntax highlighting and code completion, just like an IDE for a programming language.

Tutorials

https://casbin.org/docs/en/tutorials

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.

2. 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
   }

3. 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")

See Policy management APIs for more usage.

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

Policy management

Casbin provides two sets of APIs to manage permissions:

• Management API: the primitive API that provides full support for Casbin policy management. See here for examples.
• 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. See here for examples.

We also provide a web-based UI for model management and policy management:

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 (except the default file adapter). 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:)

Adapter	Type	Author	Description
File Adapter (built-in)	File	Casbin	Persistence for .CSV (Comma-Separated Values) files
Filtered File Adapter (built-in)	File	@faceless-saint	Persistence for .CSV (Comma-Separated Values) files with policy subset loading support
Xorm Adapter	ORM	Casbin	MySQL, PostgreSQL, TiDB, SQLite, SQL Server, Oracle are supported by Xorm
Gorm Adapter	ORM	Casbin	MySQL, PostgreSQL, Sqlite3, SQL Server are supported by Gorm
Beego ORM Adapter	ORM	Casbin	MySQL, PostgreSQL, Sqlite3 are supported by Beego ORM
MongoDB Adapter	NoSQL	Casbin	Persistence for MongoDB
Cassandra Adapter	NoSQL	Casbin	Persistence for Apache Cassandra DB
Consul Adapter	KV store	@ankitm123	Persistence for HashiCorp Consul
Redis Adapter	KV store	Casbin	Persistence for Redis
Etcd Adapter	KV store	Casbin	Persistence for etcd
Protobuf Adapter	Stream	Casbin	Persistence for Google Protocol Buffers
JSON Adapter	String	Casbin	Persistence for JSON
String Adapter	String	@qiangmzsx	Persistence for String
RQLite Adapter	SQL	EDOMO Systems	Persistence for RQLite
PostgreSQL Adapter	SQL	Going	Persistence for PostgreSQL
RethinkDB Adapter	NoSQL	@adityapandey9	Persistence for RethinkDB
DynamoDB Adapter	NoSQL	HOOQ	Persistence for Amazon DynamoDB
Minio/AWS S3 Adapter	Object storage	Soluto	Persistence for Minio and Amazon S3
Bolt Adapter	KV store	@wirepair	Persistence for Bolt

For details of adapters, please refer to the documentation: https://casbin.org/docs/en/policy-storage

Policy enforcement at scale

Some adapters support filtered policy management. This means that the policy loaded by Casbin is a subset of the policy in storage based on a given filter. This allows for efficient policy enforcement in large, multi-tenant environments when parsing the entire policy becomes a performance bottleneck.

To use filtered policies with a supported adapter, simply call the LoadFilteredPolicy method. The valid format for the filter parameter depends on the adapter used. To prevent accidental data loss, the SavePolicy method is disabled when a filtered policy is loaded.

For example, the following code snippet uses the built-in filtered file adapter and the RBAC model with domains. In this case, the filter limits the policy to a single domain. Any policy lines for domains other than "domain1" are omitted from the loaded policy:

import (
    "github.com/casbin/casbin"
)

enforcer := casbin.NewEnforcer()

adapter := fileadapter.NewFilteredAdapter("examples/rbac_with_domains_policy.csv")
enforcer.InitWithAdapter("examples/rbac_with_domains_model.conf", adapter)

filter := &fileadapter.Filter{
    P: []string{"", "domain1"},
    G: []string{"", "", "domain1"},
}
enforcer.LoadFilteredPolicy(filter)

// The loaded policy now only contains the entries pertaining to "domain1".

Policy consistence between multiple nodes

We support to use distributed messaging systems like etcd to keep consistence between multiple Casbin enforcer instances. So our users can concurrently use multiple Casbin enforcers to handle large number of permission checking requests.

Similar to policy storage adapters, we don't put watcher code in the main library. Any support for a new messaging system should be implemented as a watcher. A complete list of Casbin watchers is provided as below. Any 3rd-party contribution on a new watcher is welcomed, please inform us and I will put it in this list:)

Watcher	Type	Author	Description
Etcd Watcher	KV store	Casbin	Watcher for etcd
NATS Watcher	Messaging system	Soluto	Watcher for NATS
ZooKeeper Watcher	KV store	Grepsr	Watcher for Apache ZooKeeper
Redis Watcher	KV store	@billcobbler	Watcher for Redis

Role manager

The role manager is used to manage the RBAC role hierarchy (user-role mapping) in Casbin. A role manager can retrieve the role data from Casbin policy rules or external sources such as LDAP, Okta, Auth0, Azure AD, etc. We support different implementations of a role manager. To keep light-weight, we don't put role manager code in the main library (except the default role manager). A complete list of Casbin role managers is provided as below. Any 3rd-party contribution on a new role manager is welcomed, please inform us and I will put it in this list:)

Role manager	Author	Description
Default Role Manager (built-in)	Casbin	Supports role hierarchy stored in Casbin policy
Session Role Manager	EDOMO Systems	Supports role hierarchy stored in Casbin policy, with time-range-based sessions
Okta Role Manager	Casbin	Supports role hierarchy stored in Okta
Auth0 Role Manager	Casbin	Supports role hierarchy stored in Auth0's Authorization Extension

For developers: all role managers must implement the RoleManager interface. Session Role Manager can be used as a reference implementation.

Multi-threading

If you use Casbin in a multi-threading manner, you can use the synchronized wrapper of the Casbin enforcer: https://github.com/casbin/casbin/blob/master/enforcer_synced.go.

It also supports the AutoLoad feature, which means the Casbin enforcer will automatically load the latest policy rules from DB if it has changed. Call StartAutoLoadPolicy() to start automatically loading policy periodically and call StopAutoLoadPolicy() to stop it.

Benchmarks

The overhead of policy enforcement is benchmarked in model_b_test.go. The testbed is:

Intel(R) Core(TM) i7-6700HQ CPU @ 2.60GHz, 2601 Mhz, 4 Core(s), 8 Logical Processor(s)

The benchmarking result of go test -bench=. -benchmem is as follows (op = an Enforce() call, ms = millisecond, KB = kilo bytes):

Test case	Size	Time overhead	Memory overhead
ACL	2 rules (2 users)	0.015493 ms/op	5.649 KB
RBAC	5 rules (2 users, 1 role)	0.021738 ms/op	7.522 KB
RBAC (small)	1100 rules (1000 users, 100 roles)	0.164309 ms/op	80.620 KB
RBAC (medium)	11000 rules (10000 users, 1000 roles)	2.258262 ms/op	765.152 KB
RBAC (large)	110000 rules (100000 users, 10000 roles)	23.916776 ms/op	7.606 MB
RBAC with resource roles	6 rules (2 users, 2 roles)	0.021146 ms/op	7.906 KB
RBAC with domains/tenants	6 rules (2 users, 1 role, 2 domains)	0.032696 ms/op	10.755 KB
ABAC	0 rule (0 user)	0.007510 ms/op	2.328 KB
RESTful	5 rules (3 users)	0.045398 ms/op	91.774 KB
Deny-override	6 rules (2 users, 1 role)	0.023281 ms/op	8.370 KB
Priority	9 rules (2 users, 2 roles)	0.016389 ms/op	5.313 KB

Examples

Model	Model file	Policy file
ACL	basic_model.conf	basic_policy.csv
ACL with superuser	basic_model_with_root.conf	basic_policy.csv
ACL without users	basic_model_without_users.conf	basic_policy_without_users.csv
ACL without resources	basic_model_without_resources.conf	basic_policy_without_resources.csv
RBAC	rbac_model.conf	rbac_policy.csv
RBAC with resource roles	rbac_model_with_resource_roles.conf	rbac_policy_with_resource_roles.csv
RBAC with domains/tenants	rbac_model_with_domains.conf	rbac_policy_with_domains.csv
ABAC	abac_model.conf	N/A
RESTful	keymatch_model.conf	keymatch_policy.csv
Deny-override	rbac_model_with_deny.conf	rbac_policy_with_deny.csv
Priority	priority_model.conf	priority_policy.csv

How to use Casbin as a service?

• Casbin Server: The official Casbin as a Service solution based on gRPC, both Management API and RBAC API are provided.
• Go-Simple-API-Gateway: A simple API gateway written by golang, supports for authentication and authorization.
• middleware-acl: RESTful access control middleware based on Casbin.

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: auth/casbin
• 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

• Intel RMD: Intel's resource management daemon, via direct integration, see: model, policy rules
• VMware Dispatch: A framework for deploying and managing serverless style applications, via direct integration, see: model (in code), policy rules (in code)
• Banzai Pipeline: Banzai Cloud's RESTful API to provision or reuse managed Kubernetes clusters in the cloud, via direct integration, see: model (in code), policy rules (in code)
• Docker: The world's leading software container platform, via plugin: casbin-authz-plugin (recommended by Docker)
• Gobis: Orange's lightweight API Gateway written in go, via plugin: casbin, see model (in code), policy rules (from request)
• Skydive: An open source real-time network topology and protocols analyzer, via direct integration, see: model (in code), policy rules
• Zenpress: A CMS system written in Golang, via direct integration, see: model, policy rules (in Gorm)
• Argo CD: GitOps continuous delivery for Kubernetes, via direct integration, see: model, policy rules
• Muxi Cloud: PaaS of Muxi Cloud, an easier way to manage Kubernetes cluster, via direct integration, see: model, policy rules (in code)
• EngineerCMS: A CMS to manage knowledge for engineers, via direct integration, see: model, policy rules (in SQLite)
• Cyber Auth API: A Golang authentication API project, via direct integration, see: model, policy rules
• IRIS Community: Website for IRIS Community Activities, via direct integration, see: model, policy rules
• Metadata DB: BB archive metadata database, via direct integration, see: model, policy rules

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
• [email protected]
• Tencent QQ group: 546057381