documentation:2.0:rbac
Keywords: documentation,2.0,rbac

# RBAC model

## Presentation

RBAC stands for Role Based Access Control. It means that you manage authorizations to access applications by checking the role(s) of the user, and provide this role to the application.

As the definition of access rules is free in LemonLDAP::NG, you can implement an RBAC model if you need.

## Configuration

### Roles as simple values of a user attribute

Imagine you've set your directory schema to store roles as values of an attribute of the user, for example “description”. This is simple because you can send the role to the application by creating a HTTP header (for example Auth-Role) with the concatenated values (';' is the concatenation string):

    Auth-Roles => $description

If the user has these values inside its entry:

    description: user
    description: admin

Then you got this value inside the Auth-Roles header:

    user; admin

### Roles as entries in the directory

Now imagine the following DIT:

- dc=example,dc=com
  - ou=users
    - uid=coudot
  - ou=roles
    - ou=aaa
      - cn=admin
      - cn=user
    - ou=bbb
      - cn=admin
      - cn=user

Roles are entries, below branches representing applications. We can use the standard LDAP objectClass `organizationalRole` to maintain roles, for example:

    dn: cn=admin,ou=aaa,ou=roles,dc=example,dc=com
    objectClass: organizationalRole
    objectClass: top
    cn: admin
    ou: aaa
    roleOccupant: uid=coudot,ou=users,dc=example,dc=com

A user is attached to a role if its DN is in `roleOccupant` attribute. We add the attribute `ou` to allow LL::NG to know which application is concerned by this role.

So imagine the user coudot is “user” on application “BBB” and “admin” on application “AAA”.

#### Gather roles in session

Use the LDAP group configuration to store roles as groups in the user session:

- Base: ou=roles,dc=example,dc=com
- Object class: organizationalRole
- Target attribute: roleOccupant
- Searched attributes: cn ou

#### Restrict access to application

We configure LL::NG to authorize people on an application only if they have a role on it. For this, we use the `$hGroups` variable.

- For application AAA:

    default => groupMatch($hGroups, 'ou', 'aaa')

- For application BBB:

    default => groupMatch($hGroups, 'ou', 'bbb')

#### Send role to application

It is done by creating the correct HTTP header:

- For application AAA:

    Auth-Roles => ((grep{/aaa/} split(';',$groups))[0] =~ /([a-zA-Z]+?)/)[0]

- For application BBB:

    Auth-Roles => ((grep{/bbb/} split(';',$groups))[0] =~ /([a-zA-Z]+?)/)[0]