Introduce support for 3rd-party auth (OAuth2 & LDAP)

Signed-off-by: Thomas Citharel <tcit@tcit.fr>

lib/web/controllers/auth_controller.ex

@@ -0,0 +1,82 @@
+defmodule Mobilizon.Web.AuthController do
+  use Mobilizon.Web, :controller
+
+  alias Mobilizon.Service.Auth.Authenticator
+  alias Mobilizon.Users
+  alias Mobilizon.Users.User
+  require Logger
+  plug(:put_layout, false)
+
+  plug(Ueberauth)
+
+  def request(conn, %{"provider" => provider} = _params) do
+    redirect(conn, to: "/login?code=Login Provider not found&provider=#{provider}")
+  end
+
+  def callback(
+        %{assigns: %{ueberauth_failure: fails}} = conn,
+        %{"provider" => provider} = _params
+      ) do
+    Logger.warn("Unable to login user with #{provider} #{inspect(fails)}")
+
+    redirect(conn, to: "/login?code=Error with Login Provider&provider=#{provider}")
+  end
+
+  def callback(
+        %{assigns: %{ueberauth_auth: %Ueberauth.Auth{strategy: strategy} = auth}} = conn,
+        _params
+      ) do
+    email = email_from_ueberauth(auth)
+    [_, _, _, strategy] = strategy |> to_string() |> String.split(".")
+    strategy = String.downcase(strategy)
+
+    user =
+      with {:valid_email, false} <- {:valid_email, is_nil(email) or email == ""},
+           {:error, :user_not_found} <- Users.get_user_by_email(email),
+           {:ok, %User{} = user} <- Users.create_external(email, strategy) do
+        user
+      else
+        {:ok, %User{} = user} ->
+          user
+
+        {:error, error} ->
+          {:error, error}
+
+        error ->
+          {:error, error}
+      end
+
+    with %User{} = user <- user,
+         {:ok, %{access_token: access_token, refresh_token: refresh_token}} <-
+           Authenticator.generate_tokens(user) do
+      Logger.info("Logged-in user \"#{email}\" through #{strategy}")
+
+      render(conn, "callback.html", %{
+        access_token: access_token,
+        refresh_token: refresh_token,
+        user: user
+      })
+    else
+      err ->
+        Logger.warn("Unable to login user \"#{email}\" #{inspect(err)}")
+        redirect(conn, to: "/login?code=Error with Login Provider&provider=#{strategy}")
+    end
+  end
+
+  # Github only give public emails as part of the user profile,
+  # so we explicitely request all user emails and filter on the primary one
+  defp email_from_ueberauth(%Ueberauth.Auth{
+         strategy: Ueberauth.Strategy.Github,
+         extra: %Ueberauth.Auth.Extra{raw_info: %{user: %{"emails" => emails}}}
+       })
+       when length(emails) > 0,
+       do: emails |> Enum.find(& &1["primary"]) |> (& &1["email"]).()
+
+  defp email_from_ueberauth(%Ueberauth.Auth{
+         extra: %Ueberauth.Auth.Extra{raw_info: %{user: %{"email" => email}}}
+       })
+       when not is_nil(email) and email != "",
+       do: email
+
+  defp email_from_ueberauth(_), do: nil
+end