Option to skip authentication if no credentials provided

README.md

@@ -60,6 +60,17 @@ as part of a release.
   ]
   ```
 
+  If you want to skip authentication instead of `ArgumentError` if no credentials are provided (environment variables are not set) you can use `skip_if_no_credentials_configured` option
+
+  ```elixir
+  config :basic_auth, my_auth_with_system: [
+    username: {:system, "BASIC_AUTH_USERNAME"},
+    password: {:system, "BASIC_AUTH_PASSWORD"},
+    realm:    {:system, "BASIC_AUTH_REALM"},
+    skip_if_no_credentials_configured: true
+  ]
+  ```
+
 Alternatively you can provide a custom function to the plug to authenticate the user any way
 you want, such as finding the user from a database.
 

lib/basic_auth/configured.ex

@@ -13,14 +13,22 @@ defmodule BasicAuth.Configured do
      %__MODULE__{config_options: config_options}
   end
 
-  def respond(conn, ["Basic " <> encoded], options) do
+  def respond(conn, params, options) do
+    if skip_authentication?(options) do
+      conn
+    else
+      authenticate(conn, params, options)
+    end
+  end
+
+  def authenticate(conn, ["Basic " <> encoded], options) do
     case Base.decode64(encoded) do
       {:ok, token} -> check_token(conn, token, options)
       _ ->
         send_unauthorised_response(conn, options)
     end
   end
-  def respond(conn, _, options) do
+  def authenticate(conn, _, options) do
     send_unauthorised_response(conn, options)
   end
 
@@ -42,15 +50,19 @@ defmodule BasicAuth.Configured do
   defp to_value(value), do: value
 
   defp configured_token(config_options) do
-    username(config_options) <> ":" <> password(config_options)
+    username!(config_options) <> ":" <> password!(config_options)
   end
 
-  defp username(config_options), do: credential_part!(config_options, :username)
+  defp username(config_options), do: credential_part(config_options, :username)
+  defp username!(config_options), do: credential_part!(config_options, :username)
 
-  defp password(config_options), do: credential_part!(config_options, :password)
+  defp password(config_options), do: credential_part(config_options, :password)
+  defp password!(config_options), do: credential_part!(config_options, :password)
 
   defp realm(config_options), do: credential_part(config_options, :realm)
 
+  defp skip_if_no_credentials_configured(config_options), do: credential_part(config_options, :skip_if_no_credentials_configured)
+
   defp credential_part({app, key}, part) do
     app
     |> Application.fetch_env!(key)
@@ -64,4 +76,10 @@ defmodule BasicAuth.Configured do
       value -> value
     end
   end
+
+  defp skip_authentication?(%__MODULE__{config_options: config_options}) do
+    skip_if_no_credentials_configured(config_options) &&
+      !username(config_options) &&
+      !password(config_options)
+  end
 end

test/basic_auth/configured_test.exs

@@ -119,5 +119,44 @@ defmodule BasicAuth.ConfiguredTest do
       Application.put_env(:basic_auth, :my_auth, username: "admin")
       assert_raise(ArgumentError, ~r/Missing/, fn -> SimplePlug.call(conn, []) end)
     end
+
+  end
+
+  describe "with skip_if_no_credentials_configured option" do
+    test "skips authentication if no credentials configured" do
+      Application.put_env(:basic_auth, :my_auth,
+        username: nil,
+        password: nil,
+        realm: "Admin Area",
+        skip_if_no_credentials_configured: true
+      )
+
+      conn = call_without_credentials(SimplePlug)
+      assert conn.status == 200
+    end
+
+    test "doesn't authenticate if credentials don't match" do
+      Application.put_env(:basic_auth, :my_auth,
+        username: "admin",
+        password: "simple:password",
+        realm: "Admin Area",
+        skip_if_no_credentials_configured: true
+      )
+
+      conn = call_without_credentials(SimplePlug)
+      assert conn.status == 401
+    end
+
+    test "authenticates if credentials match" do
+      Application.put_env(:basic_auth, :my_auth,
+        username: "admin",
+        password: "simple:password",
+        realm: "Admin Area",
+        skip_if_no_credentials_configured: true
+      )
+
+      conn = call_with_credentials(SimplePlug, "admin:simple:password")
+      assert conn.status == 200
+    end
   end
 end