API Overview

This overview only shows you how to use Casbin APIs and doesn’t explain how Casbin is installed and how it works. You can find those tutorials here: installation of Casbin and how Casbin works. So, when you start reading this tutorial, we assume that you have fully installed and imported Casbin into your code.

Enforce API

Let’s start at the Enforce APIs of Casbin. We will load a RBAC model from model.conf, and load policies from policy.csv. You can learn the Model syntax here, and we won’t talk about it in this tutorial. We assume that you can understand the config files given below:

model.conf

[request_definition]
r = sub, obj, act

[policy_definition]
p = sub, obj, act

[role_definition]
g = _, _

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

[matchers]
m = g(r.sub, p.sub) && r.obj == p.obj && r.act == p.act

policy.csv

p, admin, data1, read
p, admin, data1, write
p, admin, data2, read
p, admin, data2, write
p, alice, data1, read
p, bob, data2, write
g, amber, admin
g, abc, admin

After reading the config files, please read the following code.

// load information from files
enforcer, err := casbin.NewEnforcer("./example/model.conf", "./example/policy.csv")
if err != nil {
    log.Fatalf("error, detail: %s", err)
}
ok, err := enforcer.Enforce("alice", "data1", "read")

This code loads the access control model and policies from local files. Function casbin.NewEnforcer() will return an enforcer. It will recognize its 2 parameters as file paths, and load the files from there. Errors occurred in the process are stored in err. This code used the default adapter to load model and policies. And of course you can get the same result by using a third-party adapter.

Code ok, err := enforcer.Enforce(“alice”, “data1”, “read”) is to confirm access permissions. If alice can access the data1 with the operation read, the returned value ok will be true, otherwise it’ll be false. In this example, the value of ok is true.

EnforceEx API

Sometimes you may wonder which policy allowed the request, so we prepared the function EnforceEx(). You can use it like this:

ok, reason, err := enforcer.EnforceEx("amber", "data1", "read")
fmt.Println(ok, reason) // true [admin data1 read]

function EnforceEx() will return the exact policy string in the return value reason. In this example, amber is a role of admin, so policy p, admin, data1, read made this request true. The out put of this code is in the comment.

Casbin prepared a lot of APIs like this. Those APIs added some extra functions on the basic one. They are:

ok, err := enforcer.EnforceWithMatcher(matcher, request)

With a matcher.

ok, reason, err := enforcer.EnforceExWithMatcher(matcher, request)

A combination of EnforceWithMatcher() and EnforceEx().

boolArray, err := enforcer.BatchEnforce(requests)

Do a list job, returns an array.

This is a simple use of Casbin. You can use Casbin to start an authorization server via these APIs. We will show you some other types of APIs in the next paragraphs.

Management API

Get API

These APIs are used to get exact objects in policies. This time we loaded an enforcer like the last example and get something from it.

Please read the following code:

enforcer,err := casbin.NewEnforcer("./example/model.conf", "./example/policy.csv")
if err != nil {
    fmt.Printf("Error, details: %s\n", err)
}
allSubjects := enforcer.GetAllSubjects()
fmt.Println(allSubjects)

Same as the last example, the first 4 lines loaded some necessary information from local files. We won’t talk about that here anymore.

Code allSubjects := enforcer.GetAllSubjects() got all the subjects in the policy file and returned them as an array. Then we printed that array.

Normally, the output of the code should be:

[admin alice bob]

You can also change the function GetAllSubjects() to GetAllNamedSubjects() ，to get the list of subjects that show up in the current named policy.

Similarly, we prepared GetAll functions for Objects, Actions, Roles. The only thing you need to do is to change the word Subject in the function name to what you want if you want to access those functions.

Besides, we have more getters for policies. The call method and return value are similar to those above.

policy = e.GetPolicy() gets all the authorization rules in the policy.

filteredPolicy := e.GetFilteredPolicy(0, “alice”) gets all the authorization rules in the policy, field filters can be specified.

namedPolicy := e.GetNamedPolicy(“p”) gets all the authorization rules in the named policy.

filteredNamedPolicy = e.GetFilteredNamedPolicy(“p”, 0, “bob”) gets all the authorization rules in the named policy, field filters can be specified.

groupingPolicy := e.GetGroupingPolicy() gets all the role inheritance rules in the policy.

filteredGroupingPolicy := e.GetFilteredGroupingPolicy(0, “alice”) gets all the role inheritance rules in the policy, field filters can be specified.

namedGroupingPolicy := e.GetNamedGroupingPolicy(“g”) gets all the role inheritance rules in the policy.

namedGroupingPolicy := e.GetFilteredNamedGroupingPolicy(“g”, 0, “alice”) gets all the role inheritance rules in the policy.

Add, Delete, Update API

Casbin prepared a lot of APIs for policies. These APIs allow you to add, delete or edit policies dynamically at runtime.

This code shows you how to add, remove and update your policies, and told you how to confirm that a policy exists:

// load information from files
enforcer,err := casbin.NewEnforcer("./example/model.conf", "./example/policy.csv")
if err != nil {
   fmt.Printf("Error, details: %s\n", err)
}

// add a policy, then use HasPolicy() to confirm that
enforcer.AddPolicy("added_user", "data1", "read")
hasPolicy := enforcer.HasPolicy("added_user", "data1", "read")
fmt.Println(hasPolicy) // true, we added that policy successfully

// remove a policy, then use HasPolicy() to confirm that
enforcer.RemovePolicy("alice", "data1", "read")
hasPolicy = enforcer.HasPolicy("alice", "data1", "read")
fmt.Println(hasPolicy) // false, we deleted that policy successfully

// update a policy, then use HasPolicy() to confirm that
enforcer.UpdatePolicy([]string{"added_user", "data1", "read"}, []string{"added_user", "data1", "write"})
hasPolicy = enforcer.HasPolicy("added_user", "data1", "read")
fmt.Println(hasPolicy) // false, the origin policy has lapsed
hasPolicy = enforcer.HasPolicy("added_user", "data1", "write")
fmt.Println(hasPolicy) // true, the new policy is in use

Using these four kinds of APIs can edit your policies. Like these, we prepared same kinds of APIs to FilteredPolicy, NamedPolicy, FilteredNamedPolicy, GroupingPolicy, NamedGroupingPolicy, FilteredGroupingPolicy, FilteredNamedGroupingPolicy. To use them, you only need to replace word Policy in the function name to the words above.

Besides, if you change parameters to arrays, you can batch edit you policies.

For example, to functions like this:

enforcer.UpdatePolicy([]string{"eve", "data3", "read"}, []string{"eve", "data3", "write"})

if we change Policy to Policies, and edit the parameter to:

enforcer.UpdatePolicies([][]string{{"eve", "data3", "read"}, {"jack", "data3", "read"}}, [][]string{{"eve", "data3", "write"}, {"jack", "data3", "write"}})

then we can batch edit these policies.

Same operations also useful to GroupingPolicy, NamedGroupingPolicy.

RBAC API

Casbin provided come APIs for you to modify the RBAC model and policies. If you are familiar with RBAC, you can use these APIs easily.

Here we only show you how to use RBAC APIs of Casbin and won’t talk about RBAC itself. You can get more details here.

We use this code to load model and policies just like before.

enforcer,err := casbin.NewEnforcer("./example/model.conf", "./example/policy.csv")
if err != nil {
    fmt.Printf("Error, details: %s\n", err)
}

then, use a instance of Enforcer enforcer to access these APIs.

roles, err := enforcer.GetRolesForUser("amber")
fmt.Println(roles) // [admin]
users, err := enforcer.GetUsersForRole("admin")
fmt.Println(users) // [amber abc]

GetRolesForUser() returned an array that contained all roles contained amber. In this example, amber has only one role admin, so array roles is [admin]. And similarly, you can use GetUsersForRole() to get users belongs to the role. The return value of this function is also an array.

enforcer.HasRoleForUser("amber", "admin") // true

You can use HasRoleForUser() to confirm whether the user belongs to the role. In this example, amber is a member of admin, so the return value of the function is true.

fmt.Println(enforcer.Enforce("bob", "data2", "write")) // true
enforcer.DeletePermission("data2", "write")
fmt.Println(enforcer.Enforce("bob", "data2", "write")) // false

You can use DeletePermission() to delete a permission.

fmt.Println(enforcer.Enforce("alice", "data1", "read")) // true
enforcer.DeletePermissionForUser("alice", "data1", "read")
fmt.Println(enforcer.Enforce("alice", "data1", "read")) // false

And use DeletePermissionForUser() to delete a permission for a user.

Casbin have a lot of APIs like this. Their call methods and return values have the same style as the above APIs. You can find these APIs in next documents.