Plug v1.10.3 Plug.BasicAuth View Source

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.

High-level 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. In the next section we will explore using lower level API for a more dynamic solution where the credentials might be stored in a database, environment variables etc.

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. Use Plug.Crypto.secure_compare/2 instead.

Link to this section Summary

Functions

Higher level usage of Basic HTTP auth.

Encodes a basic authentication header.

Parses the request username and password from Basic HTTP auth.

Requests basic authentication from the client.

Link to this section Functions

Link to this function

basic_auth(conn, options \\ [])

View Source

Higher level usage of Basic HTTP auth.

See the module docs for examples.

Options

  • :username - the expected username
  • :password - the expected password
  • :realm - the authentication realm. The value is not fully sanitized, so do not accept user input as the realm and use strings with only alphanumeric characters and space
Link to this function

encode_basic_auth(user, pass)

View Source

Encodes a basic authentication header.

This can be used during tests:

put_req_header(conn, "authorization", encode_basic_auth("hello", "world"))

Parses the request username and password from Basic HTTP auth.

It returns either {user, pass} or :error. Note the username and password may be empty strings. When comparing the username and password with the expected values, be sure to use Plug.Crypto.secure_compare/2.

See the module docs for examples.

Link to this function

request_basic_auth(conn, options \\ [])

View Source

Requests basic authentication from the client.

It sets the response to status 401 with "Unauthorized" as body. The response is not sent though (nor the connection is halted), allowing developers to further customize it.

Options

  • :realm - the authentication realm. The value is not fully sanitized, so do not accept user input as the realm and use strings with only alphanumeric characters and space