users: refactor login and authentication logic.

* Make authentication methods into User instance methods instead of
  class methods.
* Fix API key authentication to use a secure string comparison. Fixes a
  hypothetical (unlikely to be exploitable) timing attack.
* Move login logic from SessionCreator to SessionLoader.

test/functional/passwords_controller_test.rb

@@ -18,8 +18,8 @@ class PasswordsControllerTest < ActionDispatch::IntegrationTest
         put_auth user_password_path(@user), @user, params: { user: { old_password: "12345", password: "abcde", password_confirmation: "abcde" } }
 
         assert_redirected_to @user
-        assert_equal(nil, User.authenticate(@user.name, "12345"))
-        assert_equal(@user, User.authenticate(@user.name, "abcde"))
+        assert_equal(false, @user.reload.authenticate_password("12345"))
+        assert_equal(@user, @user.authenticate_password("abcde"))
       end
 
       should "update the password when given a valid login key" do
@@ -27,24 +27,24 @@ class PasswordsControllerTest < ActionDispatch::IntegrationTest
         put_auth user_password_path(@user), @user, params: { user: { password: "abcde", password_confirmation: "abcde", signed_user_id: signed_user_id } }
 
         assert_redirected_to @user
-        assert_equal(nil, User.authenticate(@user.name, "12345"))
-        assert_equal(@user, User.authenticate(@user.name, "abcde"))
+        assert_equal(false, @user.reload.authenticate_password("12345"))
+        assert_equal(@user, @user.authenticate_password("abcde"))
       end
 
       should "not update the password when given an invalid old password" do
         put_auth user_password_path(@user), @user, params: { user: { old_password: "3qoirjqe", password: "abcde", password_confirmation: "abcde" } }
 
         assert_response :success
-        assert_equal(@user, User.authenticate(@user.name, "12345"))
-        assert_equal(nil, User.authenticate(@user.name, "abcde"))
+        assert_equal(@user, @user.reload.authenticate_password("12345"))
+        assert_equal(false, @user.authenticate_password("abcde"))
       end
 
       should "not update the password when password confirmation fails for the new password" do
         put_auth user_password_path(@user), @user, params: { user: { old_password: "12345", password: "abcde", password_confirmation: "qerogijqe" } }
 
         assert_response :success
-        assert_equal(@user, User.authenticate(@user.name, "12345"))
-        assert_equal(nil, User.authenticate(@user.name, "abcde"))
+        assert_equal(@user, @user.reload.authenticate_password("12345"))
+        assert_equal(false, @user.authenticate_password("abcde"))
       end
     end
   end

test/functional/sessions_controller_test.rb

@@ -3,7 +3,7 @@ require 'test_helper'
 class SessionsControllerTest < ActionDispatch::IntegrationTest
   context "the sessions controller" do
     setup do
-      @user = create(:user)
+      @user = create(:user, password: "password")
     end
 
     context "new action" do
@@ -14,15 +14,27 @@ class SessionsControllerTest < ActionDispatch::IntegrationTest
     end
 
     context "create action" do
-      should "create a new session" do
-        post session_path, params: {:name => @user.name, :password => "password"}
+      should "log the user in when given the correct password" do
+        post session_path, params: { name: @user.name, password: "password" }
 
         assert_redirected_to posts_path
         assert_equal(@user.id, session[:user_id])
         assert_not_nil(@user.reload.last_ip_addr)
       end
 
-      should "not allow IP banned users to create a new session" do
+      should "not log the user in when given an incorrect password" do
+        post session_path, params: { name: @user.name, password: "wrong"}
+
+        assert_response 401
+        assert_nil(nil, session[:user_id])
+      end
+
+      should "redirect the user when given an url param" do
+        post session_path, params: { name: @user.name, password: "password", url: tags_path }
+        assert_redirected_to tags_path
+      end
+
+      should "not allow IP banned users to login" do
         create(:ip_ban, ip_addr: "1.2.3.4")
         post session_path, params: { name: @user.name, password: "password" }, headers: { REMOTE_ADDR: "1.2.3.4" }
 

test/functional/users_controller_test.rb

@@ -118,7 +118,7 @@ class UsersControllerTest < ActionDispatch::IntegrationTest
 
         assert_redirected_to User.last
         assert_equal("xxx", User.last.name)
-        assert_equal(User.last, User.authenticate("xxx", "xxxxx1"))
+        assert_equal(User.last, User.last.authenticate_password("xxxxx1"))
         assert_equal(nil, User.last.email_address)
         assert_no_enqueued_emails
       end
@@ -128,7 +128,7 @@ class UsersControllerTest < ActionDispatch::IntegrationTest
 
         assert_redirected_to User.last
         assert_equal("xxx", User.last.name)
-        assert_equal(User.last, User.authenticate("xxx", "xxxxx1"))
+        assert_equal(User.last, User.last.authenticate_password("xxxxx1"))
         assert_equal("webmaster@danbooru.donmai.us", User.last.email_address.address)
         assert_enqueued_email_with UserMailer, :welcome_user, args: [User.last]
       end

test/unit/api_key_test.rb

@@ -18,15 +18,15 @@ class ApiKeyTest < ActiveSupport::TestCase
     end
 
     should "authenticate via api key" do
-      assert_not_nil(User.authenticate_api_key(@user.name, @api_key.key))
+      assert_equal(@user, @user.authenticate_api_key(@api_key.key))
     end
 
     should "not authenticate with the wrong api key" do
-      assert_nil(User.authenticate_api_key(@user.name, "xxx"))
+      assert_equal(false, @user.authenticate_api_key("xxx"))
     end
 
     should "not authenticate with the wrong name" do
-      assert_nil(User.authenticate_api_key("xxx", @api_key.key))
+      assert_equal(false, create(:user).authenticate_api_key(@api_key.key))
     end
 
     should "have the same limits whether or not they have an api key" do

test/unit/user_deletion_test.rb

@@ -43,7 +43,7 @@ class UserDeletionTest < ActiveSupport::TestCase
 
     should "reset the password" do
       @deletion.delete!
-      assert_nil(User.authenticate(@user.name, "password"))
+      assert_equal(false, @user.authenticate_password("password"))
     end
 
     should "remove any favorites" do

test/unit/user_test.rb

@@ -39,11 +39,9 @@ class UserTest < ActiveSupport::TestCase
       end
     end
 
-    should "authenticate" do
-      assert(User.authenticate(@user.name, "password"), "Authentication should have succeeded")
-      assert(!User.authenticate(@user.name, "password2"), "Authentication should not have succeeded")
-      assert(User.authenticate_hash(@user.name, User.sha1("password")), "Authentication should have succeeded")
-      assert(!User.authenticate_hash(@user.name, User.sha1("xxx")), "Authentication should not have succeeded")
+    should "authenticate password" do
+      assert_equal(@user, @user.authenticate_password("password"))
+      assert_equal(false, @user.authenticate_password("password2"))
     end
 
     should "normalize its level" do