Functionality for providing Basic HTTP authentication.

It is recommended to only use this module in production if SSL is enabled and enforced. See Plug.SSL for more information.

Compile-time usage

If you have a single username and password, you can use the basic_auth/2 plug:

import Plug.BasicAuth
plug :basic_auth, username: "hello", password: "secret"

Or if you would rather put those in a config file:

# lib/your_app.ex
import Plug.BasicAuth
plug :basic_auth, Application.compile_env(:my_app, :basic_auth)

# config/config.exs
config :my_app, :basic_auth, username: "hello", password: "secret"

Once the user first accesses the page, the request will be denied with reason 401 and the request is halted. The browser will then prompt the user for username and password. If they match, then the request succeeds.

Both approaches shown above rely on static configuration. Let's see alternatives.

Runtime-time usage

As any other Plug, we can use the basic_auth at runtime by simply wrapping it in a function:

plug :auth

defp auth(conn, _opts) do
  username = System.fetch_env!("AUTH_USERNAME")
  password = System.fetch_env!("AUTH_PASSWORD")
  Plug.BasicAuth.basic_auth(conn, username: username, password: password)
end

This approach is useful when both username and password are specified upfront and available at runtime. However, you may also want to compute a different password for each different user. In those cases, we can use the low-level API.

Low-level usage

If you want to provide your own authentication logic on top of Basic HTTP auth, you can use the low-level functions. As an example, we define :auth plug that extracts username and password from the request headers, compares them against the database, and either assigns a :current_user on success or responds with an error on failure.

plug :auth

defp auth(conn, _opts) do
  with {user, pass} <- Plug.BasicAuth.parse_basic_auth(conn),
       %User{} = user <- MyApp.Accounts.find_by_username_and_password(user, pass) do
    assign(conn, :current_user, user)
  else
    _ -> conn |> Plug.BasicAuth.request_basic_auth() |> halt()
  end
end

Keep in mind that:

• The supplied user and pass may be empty strings;

• If you are comparing the username and password with existing strings, do not use ==/2 or pattern matching. Use Plug.Crypto.secure_compare/2 instead.