Basic authentication

The Basic authentication scheme can be used for logging in users. In this scheme, user credentials are transmitted as username/password pairs encoded using Base64.

Basic authentication flow

The basic authentication flow looks as follows:

A client makes a request without the Authorization header to a specific resource in a server application.
A server responds to a client with a 401 (Unauthorized) response status and uses a WWW-Authenticate response header to provide information that the basic authentication scheme is used to protect a route. A typical WWW-Authenticate header looks like this:
WWW-Authenticate: Basic realm="Access to the '/' path", charset="UTF-8"
The Ktor client allows you to send credentials without waiting the WWW-Authenticate header using the sendWithoutRequest function.
Usually, a client displays a login dialog where a user can enter credentials. Then, a client makes a request with the Authorization header containing a username and password pair encoded using Base64, for example:
Authorization: Basic amV0YnJhaW5zOmZvb2Jhcg
A server validates credentials sent by the client and responds with the requested content.

Configure basic authentication

To send user credentials in the Authorization header using the Basic scheme, you need to configure the basic authentication provider as follows:

Call the basic function inside the install block.
Provide the required credentials using BasicAuthCredentials and pass this object to the credentials function.
Configure the realm using the realm property.
val client = HttpClient(CIO) { install(Auth) { basic { credentials { BasicAuthCredentials(username = "jetbrains", password = "foobar") } realm = "Access to the '/' path" } } }
Optionally, enable sending credentials in the initial request without waiting for a 401 (Unauthorized) response with the WWW-Authenticate header. You need to call the sendWithoutRequest function returning boolean and check the request parameters.
install(Auth) { basic { // ... sendWithoutRequest { request -> request.url.host == "0.0.0.0" } } }

Last modified: 26 December 2022