Decouple SAML authentication from the default Omniauth logic

CHANGELOG

@@ -64,6 +64,9 @@ v 8.5.0 (unreleased)
   - Fix broken link to project in build notification emails
   - Ability to see and sort on vote count from Issues and MR lists
   - Fix builds scheduler when first build in stage was allowed to fail
+  - Allow SAML users to login with no previous account without having to allow
+    all Omniauth providers to do so.
+  - Allow existing users to auto link their SAML credentials by logging in via SAML
 
 v 8.4.4
   - Update omniauth-saml gem to 1.4.2

app/controllers/omniauth_callbacks_controller.rb

@@ -42,6 +42,26 @@ class OmniauthCallbacksController < Devise::OmniauthCallbacksController
     end
   end
 
+  def saml
+    if current_user
+      log_audit_event(current_user, with: :saml)
+      # Update SAML identity if data has changed.
+      identity = current_user.identities.find_by(extern_uid: oauth['uid'], provider: :saml)
+      if identity.nil?
+        current_user.identities.create(extern_uid: oauth['uid'], provider: :saml)
+        redirect_to profile_account_path, notice: 'Authentication method updated'
+      else
+        redirect_to after_sign_in_path_for(current_user)
+      end
+    else
+      saml_user = Gitlab::Saml::User.new(oauth)
+      saml_user.save
+      @user = saml_user.gl_user
+
+      continue_login_process
+    end
+  end
+
   def omniauth_error
     @provider = params[:provider]
     @error = params[:error]
@@ -65,25 +85,11 @@ class OmniauthCallbacksController < Devise::OmniauthCallbacksController
       log_audit_event(current_user, with: oauth['provider'])
       redirect_to profile_account_path, notice: 'Authentication method updated'
     else
-      @user = Gitlab::OAuth::User.new(oauth)
-      @user.save
+      oauth_user = Gitlab::OAuth::User.new(oauth)
+      oauth_user.save
+      @user = oauth_user.gl_user
 
-      # Only allow properly saved users to login.
-      if @user.persisted? && @user.valid?
-        log_audit_event(@user.gl_user, with: oauth['provider'])
-        sign_in_and_redirect(@user.gl_user)
-      else
-        error_message =
-          if @user.gl_user.errors.any?
-            @user.gl_user.errors.map do |attribute, message|
-              "#{attribute} #{message}"
-            end.join(", ")
-          else
-            ''
-          end
-
-        redirect_to omniauth_error_path(oauth['provider'], error: error_message) and return
-      end
+      continue_login_process
     end
   rescue Gitlab::OAuth::SignupDisabledError
     label = Gitlab::OAuth::Provider.label_for(oauth['provider'])
@@ -104,6 +110,18 @@ class OmniauthCallbacksController < Devise::OmniauthCallbacksController
     session[:service_tickets][provider] = ticket
   end
 
+  def continue_login_process
+    # Only allow properly saved users to login.
+    if @user.persisted? && @user.valid?
+      log_audit_event(@user, with: oauth['provider'])
+      sign_in_and_redirect(@user)
+    else
+      error_message = @user.errors.full_messages.to_sentence
+
+      redirect_to omniauth_error_path(oauth['provider'], error: error_message) and return
+    end
+  end
+
   def oauth
     @oauth ||= request.env['omniauth.auth']
   end

config/gitlab.yml.example

@@ -288,15 +288,22 @@ production: &base
     # auto_sign_in_with_provider: saml
 
     # CAUTION!
-    # This allows users to login without having a user account first (default: false).
+    # This allows users to login without having a user account first. Define the allowed
+    # providers using an array, e.g. ["saml", "twitter"]
     # User accounts will be created automatically when authentication was successful.
-    allow_single_sign_on: false
+    allow_single_sign_on: ["saml"]
+
     # Locks down those users until they have been cleared by the admin (default: true).
     block_auto_created_users: true
     # Look up new users in LDAP servers. If a match is found (same uid), automatically
     # link the omniauth identity with the LDAP account. (default: false)
     auto_link_ldap_user: false
 
+    # Allow users with existing accounts to login and auto link their account via SAML
+    # login, without having to do a manual login first and manually add SAML
+    # (default: false)
+    auto_link_saml_user: false
+
     ## Auth providers
     # Uncomment the following lines and fill in the data of the auth provider you want to use
     # If your favorite auth provider is not listed you can use others:

lib/gitlab/ldap/user.rb

@@ -24,6 +24,10 @@ module Gitlab
         update_user_attributes
       end
 
+      def save
+        super('LDAP')
+      end
+
       # instance methods
       def gl_user
         @gl_user ||= find_by_uid_and_provider || find_by_email || build_new_user

lib/gitlab/o_auth/user.rb

@@ -26,7 +26,7 @@ module Gitlab
         gl_user.try(:valid?)
       end
 
-      def save
+      def save(provider = 'OAuth')
         unauthorized_to_create unless gl_user
 
         if needs_blocking?
@@ -36,10 +36,10 @@ module Gitlab
           gl_user.save!
         end
 
-        log.info "(OAuth) saving user #{auth_hash.email} from login with extern_uid => #{auth_hash.uid}"
+        log.info "(#{provider}) saving user #{auth_hash.email} from login with extern_uid => #{auth_hash.uid}"
         gl_user
       rescue ActiveRecord::RecordInvalid => e
-        log.info "(OAuth) Error saving user: #{gl_user.errors.full_messages}"
+        log.info "(#{provider}) Error saving user: #{gl_user.errors.full_messages}"
         return self, e.record.errors
       end
 
@@ -105,7 +105,8 @@ module Gitlab
       end
 
       def signup_enabled?
-        Gitlab.config.omniauth.allow_single_sign_on
+        providers = Gitlab.config.omniauth.allow_single_sign_on
+        providers.include?(auth_hash.provider)
       end
 
       def block_after_signup?

lib/gitlab/saml/user.rb

@@ -0,0 +1,47 @@
+# SAML extension for User model
+#
+# * Find GitLab user based on SAML uid and provider
+# * Create new user from SAML data
+#
+module Gitlab
+  module Saml
+    class User < Gitlab::OAuth::User
+
+      def save
+        super('SAML')
+      end
+
+      def gl_user
+        @user ||= find_by_uid_and_provider
+
+        if auto_link_ldap_user?
+          @user ||= find_or_create_ldap_user
+        end
+
+        if auto_link_saml_enabled?
+          @user ||= find_by_email
+        end
+
+        if signup_enabled?
+          @user ||= build_new_user
+        end
+
+        @user
+      end
+
+      def find_by_email
+        if auth_hash.has_email?
+          user = ::User.find_by(email: auth_hash.email.downcase)
+          user.identities.new(extern_uid: auth_hash.uid, provider: auth_hash.provider) if user
+          user
+        end
+      end
+
+      protected
+
+      def auto_link_saml_enabled?
+        Gitlab.config.omniauth.auto_link_saml_user
+      end
+    end
+  end
+end

spec/lib/gitlab/o_auth/user_spec.rb

@@ -42,7 +42,7 @@ describe Gitlab::OAuth::User, lib: true do
     describe 'signup' do
       shared_examples "to verify compliance with allow_single_sign_on" do
         context "with allow_single_sign_on enabled" do
-          before { stub_omniauth_config(allow_single_sign_on: true) }
+          before { stub_omniauth_config(allow_single_sign_on: ['twitter']) }
 
           it "creates a user from Omniauth" do
             oauth_user.save
@@ -55,7 +55,7 @@ describe Gitlab::OAuth::User, lib: true do
         end
 
         context "with allow_single_sign_on disabled (Default)" do
-          before { stub_omniauth_config(allow_single_sign_on: false) }
+          before { stub_omniauth_config(allow_single_sign_on: []) }
           it "throws an error" do
             expect{ oauth_user.save }.to raise_error StandardError
           end
@@ -135,7 +135,7 @@ describe Gitlab::OAuth::User, lib: true do
 
     describe 'blocking' do
       let(:provider) { 'twitter' }
-      before { stub_omniauth_config(allow_single_sign_on: true) }
+      before { stub_omniauth_config(allow_single_sign_on: ['twitter']) }
 
       context 'signup with omniauth only' do
         context 'dont block on create' do

spec/lib/gitlab/saml/user_spec.rb

@@ -0,0 +1,271 @@
+require 'spec_helper'
+
+describe Gitlab::Saml::User, lib: true do
+  let(:saml_user) { described_class.new(auth_hash) }
+  let(:gl_user) { saml_user.gl_user }
+  let(:uid) { 'my-uid' }
+  let(:provider) { 'saml' }
+  let(:auth_hash) { OmniAuth::AuthHash.new(uid: uid, provider: provider, info: info_hash) }
+  let(:info_hash) do
+    {
+      name: 'John',
+      email: 'john@mail.com'
+    }
+  end
+  let(:ldap_user) { Gitlab::LDAP::Person.new(Net::LDAP::Entry.new, 'ldapmain') }
+
+  describe '#save' do
+    def stub_omniauth_config(messages)
+      allow(Gitlab.config.omniauth).to receive_messages(messages)
+    end
+
+    def stub_ldap_config(messages)
+      allow(Gitlab::LDAP::Config).to receive_messages(messages)
+    end
+
+    describe 'account exists on server' do
+      before { stub_omniauth_config({ allow_single_sign_on: ['saml'], auto_link_saml_user: true }) }
+      context 'and should bind with SAML' do
+        let!(:existing_user) { create(:user, email: 'john@mail.com', username: 'john') }
+        it 'adds the SAML identity to the existing user' do
+          saml_user.save
+          expect(gl_user).to be_valid
+          expect(gl_user).to eq existing_user
+          identity = gl_user.identities.first
+          expect(identity.extern_uid).to eql uid
+          expect(identity.provider).to eql 'saml'
+        end
+      end
+    end
+
+    describe 'no account exists on server' do
+      shared_examples 'to verify compliance with allow_single_sign_on' do
+        context 'with allow_single_sign_on enabled' do
+          before { stub_omniauth_config(allow_single_sign_on: ['saml']) }
+
+          it 'creates a user from SAML' do
+            saml_user.save
+
+            expect(gl_user).to be_valid
+            identity = gl_user.identities.first
+            expect(identity.extern_uid).to eql uid
+            expect(identity.provider).to eql 'saml'
+          end
+        end
+
+        context 'with allow_single_sign_on default (["saml"])' do
+          before { stub_omniauth_config(allow_single_sign_on: ['saml']) }
+          it 'should not throw an error' do
+            expect{ saml_user.save }.not_to raise_error
+          end
+        end
+
+        context 'with allow_single_sign_on disabled' do
+          before { stub_omniauth_config(allow_single_sign_on: []) }
+          it 'should throw an error' do
+            expect{ saml_user.save }.to raise_error StandardError
+          end
+        end
+      end
+
+      context 'with auto_link_ldap_user disabled (default)' do
+        before { stub_omniauth_config({ auto_link_ldap_user: false, auto_link_saml_user: false, allow_single_sign_on: ['saml'] }) }
+        include_examples 'to verify compliance with allow_single_sign_on'
+      end
+
+      context 'with auto_link_ldap_user enabled' do
+        before { stub_omniauth_config({ auto_link_ldap_user: true, auto_link_saml_user: false }) }
+
+        context 'and no LDAP provider defined' do
+          before { stub_ldap_config(providers: []) }
+
+          include_examples 'to verify compliance with allow_single_sign_on'
+        end
+
+        context 'and at least one LDAP provider is defined' do
+          before { stub_ldap_config(providers: %w(ldapmain)) }
+
+          context 'and a corresponding LDAP person' do
+            before do
+              allow(ldap_user).to receive(:uid) { uid }
+              allow(ldap_user).to receive(:username) { uid }
+              allow(ldap_user).to receive(:email) { ['johndoe@example.com','john2@example.com'] }
+              allow(ldap_user).to receive(:dn) { 'uid=user1,ou=People,dc=example' }
+              allow(Gitlab::LDAP::Person).to receive(:find_by_uid).and_return(ldap_user)
+            end
+
+            context 'and no account for the LDAP user' do
+
+              it 'creates a user with dual LDAP and SAML identities' do
+                saml_user.save
+
+                expect(gl_user).to be_valid
+                expect(gl_user.username).to eql uid
+                expect(gl_user.email).to eql 'johndoe@example.com'
+                expect(gl_user.identities.length).to eql 2
+                identities_as_hash = gl_user.identities.map { |id| { provider: id.provider, extern_uid: id.extern_uid } }
+                expect(identities_as_hash).to match_array([ { provider: 'ldapmain', extern_uid: 'uid=user1,ou=People,dc=example' },
+                                                            { provider: 'saml', extern_uid: uid }
+                                                          ])
+              end
+            end
+
+            context 'and LDAP user has an account already' do
+              let!(:existing_user) { create(:omniauth_user, email: 'john@example.com', extern_uid: 'uid=user1,ou=People,dc=example', provider: 'ldapmain', username: 'john') }
+              it "adds the omniauth identity to the LDAP account" do
+                saml_user.save
+
+                expect(gl_user).to be_valid
+                expect(gl_user.username).to eql 'john'
+                expect(gl_user.email).to eql 'john@example.com'
+                expect(gl_user.identities.length).to eql 2
+                identities_as_hash = gl_user.identities.map { |id| { provider: id.provider, extern_uid: id.extern_uid } }
+                expect(identities_as_hash).to match_array([ { provider: 'ldapmain', extern_uid: 'uid=user1,ou=People,dc=example' },
+                                                            { provider: 'saml', extern_uid: uid }
+                                                          ])
+              end
+            end
+          end
+
+          context 'and no corresponding LDAP person' do
+            before { allow(Gitlab::LDAP::Person).to receive(:find_by_uid).and_return(nil) }
+
+            include_examples 'to verify compliance with allow_single_sign_on'
+          end
+        end
+      end
+
+    end
+
+    describe 'blocking' do
+      before { stub_omniauth_config({ allow_saml_sign_up: true, auto_link_saml_user: true }) }
+
+      context 'signup with SAML only' do
+        context 'dont block on create' do
+          before { stub_omniauth_config(block_auto_created_users: false) }
+
+          it 'should not block the user' do
+            saml_user.save
+            expect(gl_user).to be_valid
+            expect(gl_user).not_to be_blocked
+          end
+        end
+
+        context 'block on create' do
+          before { stub_omniauth_config(block_auto_created_users: true) }
+
+          it 'should block user' do
+            saml_user.save
+            expect(gl_user).to be_valid
+            expect(gl_user).to be_blocked
+          end
+        end
+      end
+
+      context 'signup with linked omniauth and LDAP account' do
+        before do
+          stub_omniauth_config(auto_link_ldap_user: true)
+          allow(ldap_user).to receive(:uid) { uid }
+          allow(ldap_user).to receive(:username) { uid }
+          allow(ldap_user).to receive(:email) { ['johndoe@example.com','john2@example.com'] }
+          allow(ldap_user).to receive(:dn) { 'uid=user1,ou=People,dc=example' }
+          allow(saml_user).to receive(:ldap_person).and_return(ldap_user)
+        end
+
+        context "and no account for the LDAP user" do
+          context 'dont block on create (LDAP)' do
+            before { allow_any_instance_of(Gitlab::LDAP::Config).to receive_messages(block_auto_created_users: false) }
+
+            it do
+              saml_user.save
+              expect(gl_user).to be_valid
+              expect(gl_user).not_to be_blocked
+            end
+          end
+
+          context 'block on create (LDAP)' do
+            before { allow_any_instance_of(Gitlab::LDAP::Config).to receive_messages(block_auto_created_users: true) }
+
+            it do
+              saml_user.save
+              expect(gl_user).to be_valid
+              expect(gl_user).to be_blocked
+            end
+          end
+        end
+
+        context 'and LDAP user has an account already' do
+          let!(:existing_user) { create(:omniauth_user, email: 'john@example.com', extern_uid: 'uid=user1,ou=People,dc=example', provider: 'ldapmain', username: 'john') }
+
+          context 'dont block on create (LDAP)' do
+            before { allow_any_instance_of(Gitlab::LDAP::Config).to receive_messages(block_auto_created_users: false) }
+
+            it do
+              saml_user.save
+              expect(gl_user).to be_valid
+              expect(gl_user).not_to be_blocked
+            end
+          end
+
+          context 'block on create (LDAP)' do
+            before { allow_any_instance_of(Gitlab::LDAP::Config).to receive_messages(block_auto_created_users: true) }
+
+            it do
+              saml_user.save
+              expect(gl_user).to be_valid
+              expect(gl_user).not_to be_blocked
+            end
+          end
+        end
+      end
+
+
+      context 'sign-in' do
+        before do
+          saml_user.save
+          saml_user.gl_user.activate
+        end
+
+        context 'dont block on create' do
+          before { stub_omniauth_config(block_auto_created_users: false) }
+
+          it do
+            saml_user.save
+            expect(gl_user).to be_valid
+            expect(gl_user).not_to be_blocked
+          end
+        end
+
+        context 'block on create' do
+          before { stub_omniauth_config(block_auto_created_users: true) }
+
+          it do
+            saml_user.save
+            expect(gl_user).to be_valid
+            expect(gl_user).not_to be_blocked
+          end
+        end
+
+        context 'dont block on create (LDAP)' do
+          before { allow_any_instance_of(Gitlab::LDAP::Config).to receive_messages(block_auto_created_users: false) }
+
+          it do
+            saml_user.save
+            expect(gl_user).to be_valid
+            expect(gl_user).not_to be_blocked
+          end
+        end
+
+        context 'block on create (LDAP)' do
+          before { allow_any_instance_of(Gitlab::LDAP::Config).to receive_messages(block_auto_created_users: true) }
+
+          it do
+            saml_user.save
+            expect(gl_user).to be_valid
+            expect(gl_user).not_to be_blocked
+          end
+        end
+      end
+    end
+  end
+end