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.

Supported by Auth0

If you want to easily add authentication and authorization to your Go projects, feel free to check out Auth0's Go SDK and free plan at auth0.com/overview

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

Documentation

See: Our Wiki

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. 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
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
Protobuf Adapter Stream Casbin Persistence for Google Protocol Buffers
JSON Adapter Stream Casbin Persistence for JSON
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

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

Policy consistence between multiple nodes

We support to use etcd to keep consistence between multiple Casbin enforcer instances. Please see: https://github.com/casbin/etcd-watcher

Role manager

We support different implementations of a RBAC role manager. The currently supported adapters are:

Role manager Description
Default role manager Supports role hierarchy
Session role manager Supports role hierarchy, time-range-based sessions

For developers: all role managers must implement the RoleManager interface.

To use a custom role manager implementation:

type myCustomRoleManager struct {} // assumes the type satisfies the RoleManager interface

func newRoleManager() rbac.RoleManagerConstructor {
 return func() rbac.RoleManager {
  return &myCustomRoleManager{}
 }
}

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

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.