authentic

A Rust crate to handle authentication of HTTP calls. Documentation at https://docs.rs/authentic/latest/authentic/.

Authentication schemes can require specific workflows, such as making third-party calls to refresh a token or performing an initial request to get challenge information.

Using a fixed code structure, authentic can perform the necessary interactions for each authentication scheme. This allows schemes to be changed easily.

For example, the following code uses reqwest to access a site using HTTP Basic authentication. (See the repository tests directory for fully working examples).

```rust let client = ::reqwest::Client::new();

let credential = UsernamePasswordCredential::new("username".into(), "password".into()); let mut scheme = HttpAuthentication::new(&credential).into_scheme();

let response = loop { while let Some(authstep) = scheme.step() { match authstep { AuthenticationStep::Request(request) => { let authresponse = client.execute(request).await; scheme.respond(authresponse); } AuthenticationStep::WaitFor(duration) => { time::sleep(duration).await; } } } let request = client .get("https://httpbin.org/basic-auth/username/password") .with_authentication(&scheme) .build()?;

let response = client.execute(request).await?;

if scheme.has_completed(&response) {
    break response;
}

}; ```

The creation of the request takes place inside a loop. First, the authentication scheme is given an opportunity to perform any third-party calls using step(). HTTP Basic authentication does not use this, but it can be used, for example, to refresh an expired OAuth2 access token.

The request is created using a standard reqwest::RequestBuilder, using a new with_authentication() method to modify the request for the authentication scheme. For HTTP authentication, the first iteration makes no change to the request.

The request is sent and a response is received. For HTTP authentication, this returns a 401 Unauthorized response.

The has_completed() method checks if the response is ready to be returned or if the authentication scheme needs to retry. For HTTP authentication, this reads the returned www-authenticate challenge and updates the scheme to send the correct credentials. As the request needs to be retried, has_completed() returns false and a second iteration begins.

On the second iteration of the loop, with_authentication() adds the credentials as the Authorization header to the request. The request is authenticated and the response contains the correct data. has_completed() will return true and the loop exits with the response.