Authorization is a critical part of any application. In this article, we'll take a look at some advanced topics and best practices around Kotlin and authorization.
Authorization is the process of determining whether a user is allowed to perform an action or access a resource. In most applications, authorization is enforced by checking the user's roles and permissions.
In this article, we'll take a look at some advanced topics around Kotlin and authorization. We'll start by looking at how to define roles and permissions. Then, we'll see how to work with the authorization context. Finally, we'll look at how to enforce authorization.
One of the first steps in setting up authorization is to define the roles and permissions that users can have. There are many ways to do this, but one approach is to use an enumeration:
enum class Role {
USER,
ADMIN
}
enum class Permission {
READ,
WRITE,
DELETE
}
In this example, we've defined two roles: USER
and ADMIN
. We've also defined three permissions: READ
, WRITE
, and DELETE
.
Once you've defined your roles and permissions, you need to decide how to assign them to users. One approach is to use a map:
val roles: Map<String, Set<Role>> = mapOf(
"alice" to setOf(Role.USER),
"bob" to setOf(Role.USER, Role.ADMIN)
)
val permissions: Map<Role, Set<Permission>> = mapOf(
Role.USER to setOf(Permission.READ),
Role.ADMIN to setOf(Permission.READ, Permission.WRITE, Permission.DELETE)
)
In this example, we've defined two maps: roles
and permissions
. The roles
map maps user names to sets of roles. The permissions
map maps roles to sets of permissions.
In most applications, the authorization context is a thread-local variable. This means that each thread has its own authorization context.
The authorization context typically contains information about the user that is currently logged in. In Kotlin, this can be represented as a data class:
data class AuthorizationContext(
val user: String,
val roles: Set<Role>
)
In this example, the authorization context contains a user
property and a roles
property. The user
property contains the name of the user that is currently logged in. The roles
property contains the set of roles that the user has.
The authorization context can be accessed using the getContext()
function:
val context: AuthorizationContext? = getContext()
The getContext()
function returns an AuthorizationContext?
(i.e. a nullable AuthorizationContext
). This means that the context may not be available.
If the context is available, you can use the withContext()
function to run a block of code with a specific context:
withContext(context) {
// Code that needs the context goes here
}
The withContext()
function takes an AuthorizationContext
and a block of code. It runs the block of code with the given context.
Now that we've seen how to set up roles and permissions, and how to work with the authorization context, let's take a look at how to enforce authorization.
The easiest way to enforce authorization is to use the require()
function:
require(context != null) { "No authorization context available." }
require(context.user == "alice") { "Unauthorized user." }
require(context.roles.contains(Role.USER)) { "Unauthorized role." }
require(permissions[Role.USER]!!.contains(Permission.READ)) { "Unauthorized permission." }
In this example, we're using the require()
function to check the user's roles and permissions. If the user doesn't have the READ
permission, then an IllegalArgumentException
will be thrown.
Another way to enforce authorization is to use the check()
function:
check(context != null) { "No authorization context available." }
check(context.user == "alice") { "Unauthorized user." }
check(context.roles.contains(Role.USER)) { "Unauthorized role." }
check(permissions[Role.USER]!!.contains(Permission.READ)) { "Unauthorized permission." }
In this example, we're using the check()
function to check the user's roles and permissions. If the user doesn't have the READ
permission, then a IllegalStateException
will be thrown.
In this article, we've looked at some advanced topics and best practices around Kotlin and authorization. We've seen how to define roles and permissions, how to work with the authorization context, and how to enforce authorization.
Authorization is a critical part of any application. By following the tips and tricks in this article, you can be sure that your application is secure.