def make_not_authenticated_error(self) -> HTTPException:
        return HTTPException(
            status_code=HTTP_401_UNAUTHORIZED,
            detail="Not authenticated",
            headers={"WWW-Authenticate": "Bearer"},
        )

    async def __call__(self, request: Request) -> Optional[str]:
        authorization = request.headers.get("Authorization")
        if not authorization:
            if self.auto_error:

{* ../../docs_src/security/tutorial003_an_py310.py hl[58:66,69:74,94] *}

/// info | Informação

O cabeçalho adicional `WWW-Authenticate` com valor `Bearer` que estamos retornando aqui também faz parte da especificação.

Qualquer código de status HTTP (erro) 401 "UNAUTHORIZED" também deve retornar um cabeçalho `WWW-Authenticate`.

No caso de tokens ao portador (nosso caso), o valor desse cabeçalho deve ser `Bearer`.

 */
class JavaNetAuthenticator(
  private val defaultDns: Dns = Dns.SYSTEM,
) : okhttp3.Authenticator {
  @Throws(IOException::class)
  override fun authenticate(
    route: Route?,
    response: Response,
  ): Request? {
    val challenges = response.challenges()
    val request = response.request
    val url = request.url
    val proxyAuthorization = response.code == 407

     */
    @Size(max = 10)
    public String appendQueryParameter;

    /**
     * Enable or disable login requirement for search access.
     * When enabled, users must authenticate before performing searches.
     */
    @Size(max = 10)
    public String loginRequired;

    /**
     * Enable or disable result collapsing for similar documents.

else
  # The volume mapping flag below shares the user's gcloud credentials, if any,
  # with the container, in case the user has credentials stored there.
  # This would allow Bazel to authenticate for RBE.
  # Note: TF's CI does not have any credentials stored there.
  TFCI_DOCKER_ARGS="$TFCI_DOCKER_ARGS -v $HOME/.config/gcloud:/root/.config/gcloud"

     * @param challenge the server challenge (may be null for some auth types)
     * @return authentication response data
     * @throws CIFSException if authentication fails
     */
    byte[] authenticate(CIFSContext context, byte[] challenge) throws CIFSException;

    /**
     * Gets the session key after successful authentication
     *
     * @return the session key or null if not available
     */

    'sts',
    region_name='us-east-1',
    use_ssl=False,
    endpoint_url='http://localhost:9000',
)

app = Flask(__name__)


@app.route('/')
def homepage():
    text = '<a href="%s">Authenticate with keycloak</a>'
    return text % make_authorization_url()


def make_authorization_url():
    # Generate a random string for the state parameter
    # Save it for use later to prevent xsrf attacks

Let's imagine that you have your **backend** API in some domain.

And you have a **frontend** in another domain or in a different path of the same domain (or in a mobile application).

And you want to have a way for the frontend to authenticate with the backend, using a **username** and **password**.

We can use **OAuth2** to build that with **FastAPI**.

        // Full NTLM handshake testing would require more complex mocking

        // Arrange - Mock a server that supports NTLM
        mockResponse(HTTP_UNAUTHORIZED, "Unauthorized", Collections.singletonMap("WWW-Authenticate", Collections.singletonList("NTLM")),
                new ByteArrayInputStream(new byte[0]));

        // Act - Trigger handshake
        int responseCode = ntlmConnection.getResponseCode();

/// tip

The *path operation* for `swagger_ui_redirect` is a helper for when you use OAuth2.

If you integrate your API with an OAuth2 provider, you will be able to authenticate and come back to the API docs with the acquired credentials. And interact with it using the real OAuth2 authentication.

Swagger UI will handle it behind the scenes for you, but it needs this "redirect" helper.

///