Auth subsystem refactoring and tweaks.

Added proper OAuth skipping for SessionAuthenticationPlug. Integrated LegacyAuthenticationPlug into AuthenticationPlug. Adjusted tests & docs.

docs/dev.md

@@ -14,9 +14,9 @@ This document contains notes and guidelines for Pleroma developers.
 
   For `:api` pipeline routes, it'll be verified whether `OAuthScopesPlug` was called or explicitly skipped, and if it was not then auth information will be dropped for request. Then `EnsurePublicOrAuthenticatedPlug` will be called to ensure that either the instance is not private or user is authenticated (unless explicitly skipped). Such automated checks help to prevent human errors and result in higher security / privacy for users.
 
-## [HTTP Basic Authentication](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Authorization)
+## Non-OAuth authentication
 
-* With HTTP Basic Auth, OAuth scopes check is _not_ performed for any action (since password is provided during the auth, requester is able to obtain a token with full permissions anyways). `Pleroma.Web.Plugs.AuthenticationPlug` and `Pleroma.Web.Plugs.LegacyAuthenticationPlug` both call `Pleroma.Web.Plugs.OAuthScopesPlug.skip_plug(conn)` when password is provided.
+* With non-OAuth authentication ([HTTP Basic Authentication](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Authorization) or HTTP header- or params-provided auth), OAuth scopes check is _not_ performed for any action (since password is provided during the auth, requester is able to obtain a token with full permissions anyways); auth plugs invoke `Pleroma.Helpers.AuthHelper.skip_oauth(conn)` in this case.
 
 ## Auth-related configuration, OAuth consumer mode etc.
 

lib/pleroma/helpers/auth_helper.ex

@@ -0,0 +1,17 @@
+# Pleroma: A lightweight social networking server
+# Copyright © 2017-2020 Pleroma Authors <https://pleroma.social/>
+# SPDX-License-Identifier: AGPL-3.0-only
+
+defmodule Pleroma.Helpers.AuthHelper do
+  alias Pleroma.Web.Plugs.OAuthScopesPlug
+
+  @doc """
+  Skips OAuth permissions (scopes) checks, assigns nil `:token`.
+  Intended to be used with explicit authentication and only when OAuth token cannot be determined.
+  """
+  def skip_oauth(conn) do
+    conn
+    |> Plug.Conn.assign(:token, nil)
+    |> OAuthScopesPlug.skip_plug()
+  end
+end

lib/pleroma/web/plugs/admin_secret_authentication_plug.ex

@@ -5,8 +5,8 @@
 defmodule Pleroma.Web.Plugs.AdminSecretAuthenticationPlug do
   import Plug.Conn
 
+  alias Pleroma.Helpers.AuthHelper
   alias Pleroma.User
-  alias Pleroma.Web.Plugs.OAuthScopesPlug
   alias Pleroma.Web.Plugs.RateLimiter
 
   def init(options) do
@@ -51,7 +51,7 @@ defmodule Pleroma.Web.Plugs.AdminSecretAuthenticationPlug do
   defp assign_admin_user(conn) do
     conn
     |> assign(:user, %User{is_admin: true})
-    |> OAuthScopesPlug.skip_plug()
+    |> AuthHelper.skip_oauth()
   end
 
   defp handle_bad_token(conn) do

lib/pleroma/web/plugs/authentication_plug.ex

@@ -3,6 +3,9 @@
 # SPDX-License-Identifier: AGPL-3.0-only
 
 defmodule Pleroma.Web.Plugs.AuthenticationPlug do
+  @moduledoc "Password authentication plug."
+
+  alias Pleroma.Helpers.AuthHelper
   alias Pleroma.User
 
   import Plug.Conn
@@ -11,6 +14,30 @@ defmodule Pleroma.Web.Plugs.AuthenticationPlug do
 
   def init(options), do: options
 
+  def call(%{assigns: %{user: %User{}}} = conn, _), do: conn
+
+  def call(
+        %{
+          assigns: %{
+            auth_user: %{password_hash: password_hash} = auth_user,
+            auth_credentials: %{password: password}
+          }
+        } = conn,
+        _
+      ) do
+    if checkpw(password, password_hash) do
+      {:ok, auth_user} = maybe_update_password(auth_user, password)
+
+      conn
+      |> assign(:user, auth_user)
+      |> AuthHelper.skip_oauth()
+    else
+      conn
+    end
+  end
+
+  def call(conn, _), do: conn
+
   def checkpw(password, "$6" <> _ = password_hash) do
     :crypt.crypt(password, password_hash) == password_hash
   end
@@ -40,40 +67,6 @@ defmodule Pleroma.Web.Plugs.AuthenticationPlug do
   def maybe_update_password(user, _), do: {:ok, user}
 
   defp do_update_password(user, password) do
-    user
-    |> User.password_update_changeset(%{
-      "password" => password,
-      "password_confirmation" => password
-    })
-    |> Pleroma.Repo.update()
-  end
-
-  def call(%{assigns: %{user: %User{}}} = conn, _), do: conn
-
-  def call(
-        %{
-          assigns: %{
-            auth_user: %{password_hash: password_hash} = auth_user,
-            auth_credentials: %{password: password}
-          }
-        } = conn,
-        _
-      ) do
-    if checkpw(password, password_hash) do
-      {:ok, auth_user} = maybe_update_password(auth_user, password)
-
-      conn
-      |> assign(:user, auth_user)
-      |> Pleroma.Web.Plugs.OAuthScopesPlug.skip_plug()
-    else
-      conn
+    User.reset_password(user, %{password: password, password_confirmation: password})
   end
 end
-
-  def call(%{assigns: %{auth_credentials: %{password: _}}} = conn, _) do
-    Pbkdf2.no_user_verify()
-    conn
-  end
-
-  def call(conn, _), do: conn
-end

lib/pleroma/web/plugs/basic_auth_decoder_plug.ex

@@ -3,6 +3,12 @@
 # SPDX-License-Identifier: AGPL-3.0-only
 
 defmodule Pleroma.Web.Plugs.BasicAuthDecoderPlug do
+  @moduledoc """
+  Decodes HTTP Basic Auth information and assigns `:auth_credentials`.
+
+  NOTE: no checks are performed at this step, auth_credentials/username could be easily faked.
+  """
+
   import Plug.Conn
 
   def init(options) do

lib/pleroma/web/plugs/ensure_user_key_plug.ex

@@ -5,6 +5,8 @@
 defmodule Pleroma.Web.Plugs.EnsureUserKeyPlug do
   import Plug.Conn
 
+  @moduledoc "Ensures `conn.assigns.user` is initialized."
+
   def init(opts) do
     opts
   end
@@ -12,7 +14,6 @@ defmodule Pleroma.Web.Plugs.EnsureUserKeyPlug do
   def call(%{assigns: %{user: _}} = conn, _), do: conn
 
   def call(conn, _) do
-    conn
-    |> assign(:user, nil)
+    assign(conn, :user, nil)
   end
 end

lib/pleroma/web/plugs/legacy_authentication_plug.ex

@@ -1,41 +0,0 @@
-# Pleroma: A lightweight social networking server
-# Copyright © 2017-2020 Pleroma Authors <https://pleroma.social/>
-# SPDX-License-Identifier: AGPL-3.0-only
-
-defmodule Pleroma.Web.Plugs.LegacyAuthenticationPlug do
-  import Plug.Conn
-
-  alias Pleroma.User
-
-  def init(options) do
-    options
-  end
-
-  def call(%{assigns: %{user: %User{}}} = conn, _), do: conn
-
-  def call(
-        %{
-          assigns: %{
-            auth_user: %{password_hash: "$6$" <> _ = password_hash} = auth_user,
-            auth_credentials: %{password: password}
-          }
-        } = conn,
-        _
-      ) do
-    with ^password_hash <- :crypt.crypt(password, password_hash),
-         {:ok, user} <-
-           User.reset_password(auth_user, %{password: password, password_confirmation: password}) do
-      conn
-      |> assign(:auth_user, user)
-      |> assign(:user, user)
-      |> Pleroma.Web.Plugs.OAuthScopesPlug.skip_plug()
-    else
-      _ ->
-        conn
-    end
-  end
-
-  def call(conn, _) do
-    conn
-  end
-end

lib/pleroma/web/plugs/session_authentication_plug.ex

@@ -3,17 +3,27 @@
 # SPDX-License-Identifier: AGPL-3.0-only
 
 defmodule Pleroma.Web.Plugs.SessionAuthenticationPlug do
+  @moduledoc """
+  Authenticates user by session-stored `:user_id` and request-contained username.
+  Username can be provided via HTTP Basic Auth (the password is not checked and can be anything).
+  """
+
   import Plug.Conn
 
+  alias Pleroma.Helpers.AuthHelper
+
   def init(options) do
     options
   end
 
+  def call(%{assigns: %{user: %Pleroma.User{}}} = conn, _), do: conn
+
   def call(conn, _) do
     with saved_user_id <- get_session(conn, :user_id),
          %{auth_user: %{id: ^saved_user_id}} <- conn.assigns do
       conn
       |> assign(:user, conn.assigns.auth_user)
+      |> AuthHelper.skip_oauth()
     else
       _ -> conn
     end

lib/pleroma/web/plugs/set_user_session_id_plug.ex

@@ -11,8 +11,7 @@ defmodule Pleroma.Web.Plugs.SetUserSessionIdPlug do
   end
 
   def call(%{assigns: %{user: %User{id: id}}} = conn, _) do
-    conn
-    |> put_session(:user_id, id)
+    put_session(conn, :user_id, id)
   end
 
   def call(conn, _), do: conn

lib/pleroma/web/plugs/user_fetcher_plug.ex

@@ -3,6 +3,12 @@
 # SPDX-License-Identifier: AGPL-3.0-only
 
 defmodule Pleroma.Web.Plugs.UserFetcherPlug do
+  @moduledoc """
+  Assigns `:auth_user` basing on `:auth_credentials`.
+
+  NOTE: no checks are performed at this step, auth_credentials/username could be easily faked.
+  """
+
   alias Pleroma.User
   import Plug.Conn
 

lib/pleroma/web/router.ex

@@ -49,7 +49,6 @@ defmodule Pleroma.Web.Router do
     plug(Pleroma.Web.Plugs.BasicAuthDecoderPlug)
     plug(Pleroma.Web.Plugs.UserFetcherPlug)
     plug(Pleroma.Web.Plugs.SessionAuthenticationPlug)
-    plug(Pleroma.Web.Plugs.LegacyAuthenticationPlug)
     plug(Pleroma.Web.Plugs.AuthenticationPlug)
   end
 

test/pleroma/web/plugs/admin_secret_authentication_plug_test.exs

@@ -49,6 +49,7 @@ defmodule Pleroma.Web.Plugs.AdminSecretAuthenticationPlugTest do
         |> AdminSecretAuthenticationPlug.call(%{})
 
       assert conn.assigns[:user].is_admin
+      assert conn.assigns[:token] == nil
       assert PlugHelper.plug_skipped?(conn, OAuthScopesPlug)
     end
 
@@ -69,6 +70,7 @@ defmodule Pleroma.Web.Plugs.AdminSecretAuthenticationPlugTest do
         |> AdminSecretAuthenticationPlug.call(%{})
 
       assert conn.assigns[:user].is_admin
+      assert conn.assigns[:token] == nil
       assert PlugHelper.plug_skipped?(conn, OAuthScopesPlug)
     end
   end

test/pleroma/web/plugs/authentication_plug_test.exs

@@ -48,6 +48,7 @@ defmodule Pleroma.Web.Plugs.AuthenticationPlugTest do
       |> AuthenticationPlug.call(%{})
 
     assert conn.assigns.user == conn.assigns.auth_user
+    assert conn.assigns.token == nil
     assert PlugHelper.plug_skipped?(conn, OAuthScopesPlug)
   end
 
@@ -62,6 +63,7 @@ defmodule Pleroma.Web.Plugs.AuthenticationPlugTest do
       |> AuthenticationPlug.call(%{})
 
     assert conn.assigns.user.id == conn.assigns.auth_user.id
+    assert conn.assigns.token == nil
     assert PlugHelper.plug_skipped?(conn, OAuthScopesPlug)
 
     user = User.get_by_id(user.id)
@@ -83,6 +85,7 @@ defmodule Pleroma.Web.Plugs.AuthenticationPlugTest do
       |> AuthenticationPlug.call(%{})
 
     assert conn.assigns.user.id == conn.assigns.auth_user.id
+    assert conn.assigns.token == nil
     assert PlugHelper.plug_skipped?(conn, OAuthScopesPlug)
 
     user = User.get_by_id(user.id)

test/pleroma/web/plugs/legacy_authentication_plug_test.exs

@@ -1,82 +0,0 @@
-# Pleroma: A lightweight social networking server
-# Copyright © 2017-2020 Pleroma Authors <https://pleroma.social/>
-# SPDX-License-Identifier: AGPL-3.0-only
-
-defmodule Pleroma.Web.Plugs.LegacyAuthenticationPlugTest do
-  use Pleroma.Web.ConnCase
-
-  import Pleroma.Factory
-
-  alias Pleroma.User
-  alias Pleroma.Web.Plugs.LegacyAuthenticationPlug
-  alias Pleroma.Web.Plugs.OAuthScopesPlug
-  alias Pleroma.Web.Plugs.PlugHelper
-
-  setup do
-    user =
-      insert(:user,
-        password: "password",
-        password_hash:
-          "$6$9psBWV8gxkGOZWBz$PmfCycChoxeJ3GgGzwvhlgacb9mUoZ.KUXNCssekER4SJ7bOK53uXrHNb2e4i8yPFgSKyzaW9CcmrDXWIEMtD1"
-      )
-
-    %{user: user}
-  end
-
-  test "it does nothing if a user is assigned", %{conn: conn, user: user} do
-    conn =
-      conn
-      |> assign(:auth_credentials, %{username: "dude", password: "password"})
-      |> assign(:auth_user, user)
-      |> assign(:user, %User{})
-
-    ret_conn =
-      conn
-      |> LegacyAuthenticationPlug.call(%{})
-
-    assert ret_conn == conn
-  end
-
-  @tag :skip_on_mac
-  test "if `auth_user` is present and password is correct, " <>
-         "it authenticates the user, resets the password, marks OAuthScopesPlug as skipped",
-       %{
-         conn: conn,
-         user: user
-       } do
-    conn =
-      conn
-      |> assign(:auth_credentials, %{username: "dude", password: "password"})
-      |> assign(:auth_user, user)
-
-    conn = LegacyAuthenticationPlug.call(conn, %{})
-
-    assert conn.assigns.user.id == user.id
-    assert PlugHelper.plug_skipped?(conn, OAuthScopesPlug)
-  end
-
-  @tag :skip_on_mac
-  test "it does nothing if the password is wrong", %{
-    conn: conn,
-    user: user
-  } do
-    conn =
-      conn
-      |> assign(:auth_credentials, %{username: "dude", password: "wrong_password"})
-      |> assign(:auth_user, user)
-
-    ret_conn =
-      conn
-      |> LegacyAuthenticationPlug.call(%{})
-
-    assert conn == ret_conn
-  end
-
-  test "with no credentials or user it does nothing", %{conn: conn} do
-    ret_conn =
-      conn
-      |> LegacyAuthenticationPlug.call(%{})
-
-    assert ret_conn == conn
-  end
-end

test/pleroma/web/plugs/session_authentication_plug_test.exs

@@ -6,6 +6,8 @@ defmodule Pleroma.Web.Plugs.SessionAuthenticationPlugTest do
   use Pleroma.Web.ConnCase, async: true
 
   alias Pleroma.User
+  alias Pleroma.Web.Plugs.OAuthScopesPlug
+  alias Pleroma.Web.Plugs.PlugHelper
   alias Pleroma.Web.Plugs.SessionAuthenticationPlug
 
   setup %{conn: conn} do
@@ -18,24 +20,20 @@ defmodule Pleroma.Web.Plugs.SessionAuthenticationPlugTest do
     conn =
       conn
       |> Plug.Session.call(Plug.Session.init(session_opts))
-      |> fetch_session
+      |> fetch_session()
       |> assign(:auth_user, %User{id: 1})
 
     %{conn: conn}
   end
 
   test "it does nothing if a user is assigned", %{conn: conn} do
-    conn =
-      conn
-      |> assign(:user, %User{})
-
-    ret_conn =
-      conn
-      |> SessionAuthenticationPlug.call(%{})
+    conn = assign(conn, :user, %User{})
+    ret_conn = SessionAuthenticationPlug.call(conn, %{})
 
     assert ret_conn == conn
   end
 
+  # Scenario: requester has the cookie and knows the username (not necessarily knows the password)
   test "if the auth_user has the same id as the user_id in the session, it assigns the user", %{
     conn: conn
   } do
@@ -45,19 +43,23 @@ defmodule Pleroma.Web.Plugs.SessionAuthenticationPlugTest do
       |> SessionAuthenticationPlug.call(%{})
 
     assert conn.assigns.user == conn.assigns.auth_user
+    assert conn.assigns.token == nil
+    assert PlugHelper.plug_skipped?(conn, OAuthScopesPlug)
   end
 
+  # Scenario: requester has the cookie but doesn't know the username
   test "if the auth_user has a different id as the user_id in the session, it does nothing", %{
     conn: conn
   } do
-    conn =
-      conn
-      |> put_session(:user_id, -1)
-
-    ret_conn =
-      conn
-      |> SessionAuthenticationPlug.call(%{})
+    conn = put_session(conn, :user_id, -1)
+    ret_conn = SessionAuthenticationPlug.call(conn, %{})
 
     assert ret_conn == conn
   end
+
+  test "if the session does not contain user_id, it does nothing", %{
+    conn: conn
+  } do
+    assert conn == SessionAuthenticationPlug.call(conn, %{})
+  end
 end