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Casbin

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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 Logo

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:

golang java nodejs php
Casbin jCasbin node-Casbin PHP-Casbin
production-ready production-ready production-ready production-ready
python delphi dotnet rust
PyCasbin Casbin4D Casbin-Net Casbin-RS
production-ready experimental WIP WIP

Table of contents

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.

  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")

See Policy management APIs for more usage.

  1. 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:

model editor

policy editor

Policy persistence

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

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

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

Role manager

https://casbin.org/docs/en/role-managers

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

  • Gin: A HTTP web framework featuring a Martini-like API with much better performance, via plugin: authz
  • 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
  • Go kit: A toolkit for microservices, via built-in plugin: plugins/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
  • Chi: A lightweight, idiomatic and composable router for building HTTP services, via plugin: chi-authz
  • Buffalo: A Go web development eco-system, designed to make your life easier, via plugin: buffalo-mw-rbac (thanks to @kgosse)
  • Macaron: A high productive and modular web framework in Go, via plugin: authz
  • DotWeb: Simple and easy go web micro framework, via plugin: authz
  • Tango: Micro & pluggable web framework for Go, via plugin: authz
  • Baa: An express Go web framework with routing, middleware, dependency injection and http context, via plugin: authz

Others

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.