Honor saml assurance level to allow 2FA bypassing

app/controllers/omniauth_callbacks_controller.rb

@@ -119,7 +119,7 @@ class OmniauthCallbacksController < Devise::OmniauthCallbacksController
       set_remember_me(user)
-      if user.two_factor_enabled?
+      if user.two_factor_enabled? && !auth_user.bypass_two_factor?
         prompt_for_two_factor(user)
       else
         sign_in_and_redirect(user)

doc/integration/saml.md

@@ -179,6 +179,81 @@ tell GitLab which groups are external via the `external_groups:` element:
         } }
 ```
+## Bypass two factor authentication
+
+If you want some SAML authentication methods to count as 2FA on a per session basis, you can register them in the
+`upstream_two_factor_authn_contexts` list:
+
+**For Omnibus installations:**
+
+1. Edit `/etc/gitlab/gitlab.rb`:
+
+    ```ruby
+      gitlab_rails['omniauth_providers'] = [
+        {
+          name: 'saml',
+          args: {
+                   assertion_consumer_service_url: 'https://gitlab.example.com/users/auth/saml/callback',
+                   idp_cert_fingerprint: '43:51:43:a1:b5:fc:8b:b7:0a:3a:a9:b1:0f:66:73:a8',
+                   idp_sso_target_url: 'https://login.example.com/idp',
+                   issuer: 'https://gitlab.example.com',
+                   name_identifier_format: 'urn:oasis:names:tc:SAML:2.0:nameid-format:persistent',
+                   upstream_two_factor_authn_contexts:
+                     %w(
+                       urn:oasis:names:tc:SAML:2.0:ac:classes:CertificateProtectedTransport
+                       urn:oasis:names:tc:SAML:2.0:ac:classes:SecondFactorOTPSMS
+                       urn:oasis:names:tc:SAML:2.0:ac:classes:SecondFactorIGTOKEN
+                     )
+    
+                 },
+          label: 'Company Login' # optional label for SAML login button, defaults to "Saml"
+        }
+      ]
+    ```
+    
+1. Save the file and [reconfigure][] GitLab for the changes to take effect.
+
+---
+
+**For installations from source:**
+
+1. Edit `config/gitlab.yml`:
+    
+     ```yaml
+          - {
+              name: 'saml',
+              args: {
+                     assertion_consumer_service_url: 'https://gitlab.example.com/users/auth/saml/callback',
+                     idp_cert_fingerprint: '43:51:43:a1:b5:fc:8b:b7:0a:3a:a9:b1:0f:66:73:a8',
+                     idp_sso_target_url: 'https://login.example.com/idp',
+                     issuer: 'https://gitlab.example.com',
+                     name_identifier_format: 'urn:oasis:names:tc:SAML:2.0:nameid-format:persistent',
+                     upstream_two_factor_authn_contexts:
+                       [
+                         'urn:oasis:names:tc:SAML:2.0:ac:classes:CertificateProtectedTransport',
+                         'urn:oasis:names:tc:SAML:2.0:ac:classes:SecondFactorOTPSMS',
+                         'urn:oasis:names:tc:SAML:2.0:ac:classes:SecondFactorIGTOKEN'
+                       ]
+    
+                   },
+              label: 'Company Login' # optional label for SAML login button, defaults to "Saml"
+            }
+    ```
+    
+1. Save the file and [restart GitLab][] for the changes ot take effect
+    
+
+In addition to the changes in GitLab, make sure that your Idp is returning the
+`AuthnContext`. For example:
+
+```xml
+    <saml:AuthnStatement> 
+        <saml:AuthnContext> 
+            <saml:AuthnContextClassRef>urn:oasis:names:tc:SAML:2.0:ac:classes:MediumStrongCertificateProtectedTransport</saml:AuthnContextClassRef> 
+        </saml:AuthnContext>
+    </saml:AuthnStatement>
+```
+
 ## Customization
 ### `auto_sign_in_with_provider`

lib/gitlab/auth/o_auth/user.rb

@@ -74,6 +74,10 @@ module Gitlab
           gl_user
         end
+        def bypass_two_factor?
+          false
+        end
+
         protected
         def should_save?

lib/gitlab/auth/saml/auth_hash.rb

@@ -6,6 +6,17 @@ module Gitlab
           Array.wrap(get_raw(Gitlab::Auth::Saml::Config.groups))
         end
+        def authn_context
+          response_object = auth_hash.extra[:response_object]
+          return nil if response_object.blank?
+
+          document = response_object.decrypted_document
+          document ||= response_object.document
+          return nil if document.blank?
+
+          extract_authn_context(document)
+        end
+
         private
         def get_raw(key)
@@ -13,6 +24,10 @@ module Gitlab
           # otherwise just the first value is returned
           auth_hash.extra[:raw_info].all[key]
         end
+
+        def extract_authn_context(document)
+          REXML::XPath.first(document, "//saml:AuthnStatement/saml:AuthnContext/saml:AuthnContextClassRef/text()").to_s
+        end
       end
     end
   end

lib/gitlab/auth/saml/config.rb

@@ -7,6 +7,10 @@ module Gitlab
             Gitlab::Auth::OAuth::Provider.config_for('saml')
           end
+          def upstream_two_factor_authn_contexts
+            options.args[:upstream_two_factor_authn_contexts]
+          end
+
           def groups
             options[:groups_attribute]
           end

lib/gitlab/auth/saml/user.rb

@@ -34,6 +34,10 @@ module Gitlab
           gl_user.changed? || gl_user.identities.any?(&:changed?)
         end
+        def bypass_two_factor?
+          saml_config.upstream_two_factor_authn_contexts&.include?(auth_hash.authn_context)
+        end
+
         protected
         def saml_config

spec/controllers/omniauth_callbacks_controller_spec.rb

 require 'spec_helper'
-describe OmniauthCallbacksController do
+describe OmniauthCallbacksController, type: :controller do
   include LoginHelpers
-  let(:user) { create(:omniauth_user, extern_uid: extern_uid, provider: provider) }
-
-  before do
-    mock_auth_hash(provider.to_s, extern_uid, user.email)
-    stub_omniauth_provider(provider, context: request)
-  end
-
-  context 'when the user is on the last sign in attempt' do
-    let(:extern_uid) { 'my-uid' }
+  describe 'omniauth' do
+    let(:user) { create(:omniauth_user, extern_uid: extern_uid, provider: provider) }
     before do
-      user.update(failed_attempts: User.maximum_attempts.pred)
-      subject.response = ActionDispatch::Response.new
+      mock_auth_hash(provider.to_s, extern_uid, user.email)
+      stub_omniauth_provider(provider, context: request)
     end
-    context 'when using a form based provider' do
-      let(:provider) { :ldap }
-
-      it 'locks the user when sign in fails' do
-        allow(subject).to receive(:params).and_return(ActionController::Parameters.new(username: user.username))
-        request.env['omniauth.error.strategy'] = OmniAuth::Strategies::LDAP.new(nil)
-
-        subject.send(:failure)
-        expect(user.reload).to be_access_locked
+    context 'when the user is on the last sign in attempt' do
+      let(:extern_uid) { 'my-uid' }
+      before do
+        user.update(failed_attempts: User.maximum_attempts.pred)
+        subject.response = ActionDispatch::Response.new
       end
-    end
-    context 'when using a button based provider' do
-      let(:provider) { :github }
-      it 'does not lock the user when sign in fails' do
-        request.env['omniauth.error.strategy'] = OmniAuth::Strategies::GitHub.new(nil)
-        subject.send(:failure)
-        expect(user.reload).not_to be_access_locked
+      context 'when using a form based provider' do
+        let(:provider) { :ldap }
+        it 'locks the user when sign in fails' do
+          allow(subject).to receive(:params).and_return(ActionController::Parameters.new(username: user.username))
+          request.env['omniauth.error.strategy'] = OmniAuth::Strategies::LDAP.new(nil)
+          subject.send(:failure)
+          expect(user.reload).to be_access_locked
+        end
       end
-    end
-  end
-  context 'strategies' do
-    context 'github' do
-      let(:extern_uid) { 'my-uid' }
-      let(:provider) { :github }
-      it 'allows sign in' do
-        post provider
-        expect(request.env['warden']).to be_authenticated
-      end
-
-      shared_context 'sign_up' do
-        let(:user) { double(email: 'new@example.com') }
-        before do
-          stub_omniauth_setting(block_auto_created_users: false)
+      context 'when using a button based provider' do
+        let(:provider) { :github }
+        it 'does not lock the user when sign in fails' do
+          request.env['omniauth.error.strategy'] = OmniAuth::Strategies::GitHub.new(nil)
+          subject.send(:failure)
+          expect(user.reload).not_to be_access_locked
         end
       end
-      context 'sign up' do
-        include_context 'sign_up'
-        it 'is allowed' do
+    end
+    context 'strategies' do
+      context 'github' do
+        let(:extern_uid) { 'my-uid' }
+        let(:provider) { :github }
+        it 'allows sign in' do
           post provider
           expect(request.env['warden']).to be_authenticated
         end
-      end
-
-      context 'when OAuth is disabled' do
-        before do
-          stub_env('IN_MEMORY_APPLICATION_SETTINGS', 'false')
-          settings = Gitlab::CurrentSettings.current_application_settings
-          settings.update(disabled_oauth_sign_in_sources: [provider.to_s])
-        end
-        it 'prevents login via POST' do
-          post provider
-          expect(request.env['warden']).not_to be_authenticated
+        shared_context 'sign_up' do
+          let(:user) { double(email: 'new@example.com') }
+          before do
+            stub_omniauth_setting(block_auto_created_users: false)
+          end
         end
-        it 'shows warning when attempting login' do
-          post provider
-
-          expect(response).to redirect_to new_user_session_path
-          expect(flash[:alert]).to eq('Signing in using GitHub has been disabled')
-        end
-        it 'allows linking the disabled provider' do
-          user.identities.destroy_all
-          sign_in(user)
-          expect { post provider }.to change { user.reload.identities.count }.by(1)
+        context 'sign up' do
+          include_context 'sign_up'
+          it 'is allowed' do
+            post provider
+            expect(request.env['warden']).to be_authenticated
+          end
         end
-        context 'sign up' do
-          include_context 'sign_up'
-          it 'is prevented' do
+        context 'when OAuth is disabled' do
+          before do
+            stub_env('IN_MEMORY_APPLICATION_SETTINGS', 'false')
+            settings = Gitlab::CurrentSettings.current_application_settings
+            settings.update(disabled_oauth_sign_in_sources: [provider.to_s])
+          end
+          it 'prevents login via POST' do
             post provider
             expect(request.env['warden']).not_to be_authenticated
           end
+
+          it 'shows warning when attempting login' do
+            post provider
+
+            expect(response).to redirect_to new_user_session_path
+            expect(flash[:alert]).to eq('Signing in using GitHub has been disabled')
+          end
+
+          it 'allows linking the disabled provider' do
+            user.identities.destroy_all
+            sign_in(user)
+
+            expect { post provider }.to change { user.reload.identities.count }.by(1)
+          end
+
+          context 'sign up' do
+            include_context 'sign_up'
+
+            it 'is prevented' do
+              post provider
+
+              expect(request.env['warden']).not_to be_authenticated
+            end
+          end
+        end
+      end
+
+      context 'auth0' do
+        let(:extern_uid) { '' }
+        let(:provider) { :auth0 }
+
+        it 'does not allow sign in without extern_uid' do
+          post 'auth0'
+
+          expect(request.env['warden']).not_to be_authenticated
+          expect(response.status).to eq(302)
+          expect(controller).to set_flash[:alert].to('Wrong extern UID provided. Make sure Auth0 is configured correctly.')
         end
       end
     end
-    context 'auth0' do
-      let(:extern_uid) { '' }
-      let(:provider) { :auth0 }
-      it 'does not allow sign in without extern_uid' do
-        post 'auth0'
+  end
+
+  describe '#saml' do
+    let(:user) { create(:omniauth_user, :two_factor, extern_uid: 'my-uid', provider: 'saml') }
+    let(:mock_saml_response) { File.read('spec/fixtures/authentication/saml_response.xml') }
+    let(:saml_config) { mock_saml_config_with_upstream_two_factor_authn_contexts }
+
+    before do
+      stub_omniauth_saml_config({ enabled: true, auto_link_saml_user: true, allow_single_sign_on: ['saml'],
+                                  providers: [saml_config] })
+      mock_auth_hash('saml', 'my-uid', user.email, mock_saml_response)
+      request.env["devise.mapping"] = Devise.mappings[:user]
+      request.env['omniauth.auth'] = Rails.application.env_config['omniauth.auth']
+      post :saml, params: { SAMLResponse: mock_saml_response }
+    end
+    context 'when worth two factors' do
+      let(:mock_saml_response) do
+        File.read('spec/fixtures/authentication/saml_response.xml')
+            .gsub('urn:oasis:names:tc:SAML:2.0:ac:classes:Password', 'urn:oasis:names:tc:SAML:2.0:ac:classes:SecondFactorIGTOKEN')
+      end
+      it 'expects user to be signed_in' do
+        expect(request.env['warden']).to be_authenticated
+      end
+    end
+    context 'when not worth two factors' do
+      it 'expects user to provide second factor' do
+        expect(response).to render_template('devise/sessions/two_factor')
         expect(request.env['warden']).not_to be_authenticated
-        expect(response.status).to eq(302)
-        expect(controller).to set_flash[:alert].to('Wrong extern UID provided. Make sure Auth0 is configured correctly.')
       end
     end
   end

spec/dependencies/omniauth_saml_spec.rb

+require 'spec_helper'
+require 'omniauth/strategies/saml'
+
+describe 'processing of SAMLResponse in dependencies' do
+  let(:mock_saml_response) { File.read('spec/fixtures/authentication/saml_response.xml') }
+  let(:saml_strategy) { OmniAuth::Strategies::SAML.new({}) }
+  let(:session_mock) { {} }
+  let(:settings) { OpenStruct.new({ soft: false, idp_cert_fingerprint: 'something' }) }
+  let(:auth_hash) { Gitlab::Auth::Saml::AuthHash.new(saml_strategy) }
+
+  subject { auth_hash.authn_context }
+
+  before do
+    allow(saml_strategy).to receive(:session).and_return(session_mock)
+    allow_any_instance_of(OneLogin::RubySaml::Response).to receive(:is_valid?).and_return(true)
+    saml_strategy.send(:handle_response, mock_saml_response, {}, settings ) { }
+  end
+
+  it 'can extract AuthnContextClassRef from SAMLResponse param' do
+    is_expected.to eq 'urn:oasis:names:tc:SAML:2.0:ac:classes:Password'
+  end
+end

spec/features/users/login_spec.rb

@@ -177,14 +177,35 @@ feature 'Login' do
     end
     context 'logging in via OAuth' do
-      it 'shows 2FA prompt after OAuth login' do
-        stub_omniauth_saml_config(enabled: true, auto_link_saml_user: true, allow_single_sign_on: ['saml'], providers: [mock_saml_config])
-        user = create(:omniauth_user, :two_factor, extern_uid: 'my-uid', provider: 'saml')
-        gitlab_sign_in_via('saml', user, 'my-uid')
-        expect(page).to have_content('Two-Factor Authentication')
-        enter_code(user.current_otp)
-        expect(current_path).to eq root_path
+      let(:user) { create(:omniauth_user, :two_factor, extern_uid: 'my-uid', provider: 'saml')}
+      let(:mock_saml_response) do
+        File.read('spec/fixtures/authentication/saml_response.xml')
+      end
+      before do
+        stub_omniauth_saml_config(enabled: true, auto_link_saml_user: true, allow_single_sign_on: ['saml'],
+                                  providers: [mock_saml_config_with_upstream_two_factor_authn_contexts])
+        gitlab_sign_in_via('saml', user, 'my-uid', mock_saml_response)
+      end
+
+      context 'when authn_context is worth two factors' do
+        let(:mock_saml_response) do
+          File.read('spec/fixtures/authentication/saml_response.xml')
+              .gsub('urn:oasis:names:tc:SAML:2.0:ac:classes:Password', 'urn:oasis:names:tc:SAML:2.0:ac:classes:SecondFactorOTPSMS')
+        end
+
+        it 'signs user in without prompting for second factor' do
+          expect(page).not_to have_content('Two-Factor Authentication')
+          expect(current_path).to eq root_path
+        end
+      end
+
+      context 'when authn_context is not worth two factors' do
+        it 'shows 2FA prompt after OAuth login' do
+          expect(page).to have_content('Two-Factor Authentication')
+          enter_code(user.current_otp)
+          expect(current_path).to eq root_path
+        end
       end
     end
   end

spec/fixtures/authentication/saml_response.xml

+<?xml version='1.0'?>
+<samlp:Response xmlns:samlp='urn:oasis:names:tc:SAML:2.0:protocol' xmlns:saml='urn:oasis:names:tc:SAML:2.0:assertion' ID='pfxb9b71715-2202-9a51-8ae5-689d5b9dd25a' Version='2.0' IssueInstant='2014-07-17T01:01:48Z' Destination='http://sp.example.com/demo1/index.php?acs' InResponseTo='ONELOGIN_4fee3b046395c4e751011e97f8900b5273d56685'>
+  <saml:Issuer>http://idp.example.com/metadata.php</saml:Issuer><ds:Signature xmlns:ds='http://www.w3.org/2000/09/xmldsig#'>
+  <ds:SignedInfo><ds:CanonicalizationMethod Algorithm='http://www.w3.org/2001/10/xml-exc-c14n#'/>
+    <ds:SignatureMethod Algorithm='http://www.w3.org/2000/09/xmldsig#rsa-sha1'/>
+    <ds:Reference URI='#pfxb9b71715-2202-9a51-8ae5-689d5b9dd25a'><ds:Transforms><ds:Transform Algorithm='http://www.w3.org/2000/09/xmldsig#enveloped-signature'/><ds:Transform Algorithm='http://www.w3.org/2001/10/xml-exc-c14n#'/></ds:Transforms><ds:DigestMethod Algorithm='http://www.w3.org/2000/09/xmldsig#sha1'/><ds:DigestValue>z0Y25hsUHVJJnYhgB5LzPVjqbgM=</ds:DigestValue></ds:Reference></ds:SignedInfo><ds:SignatureValue>NSdsZopzNX4kJETipLNbU+7dG4GPTj5e40iSBaUeUMc1UUSX4UCe9Qx6R9ADEkEQgNekgYaCFOuY90kLNh9Ky0Czq8gd4w7ykQJEVJ7VF7LakmG8dPedHAKyAMAuZ8y3mNGye31vtR9frYaznCVoxB3eAi9rbVOXkQtdOTRMHec=</ds:SignatureValue>
+  <ds:KeyInfo><ds:X509Data><ds:X509Certificate>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</ds:X509Certificate></ds:X509Data></ds:KeyInfo></ds:Signature>
+  <samlp:Status>
+    <samlp:StatusCode Value='urn:oasis:names:tc:SAML:2.0:status:Success'/>
+  </samlp:Status>
+  <saml:Assertion xmlns:xsi='http://www.w3.org/2001/XMLSchema-instance' xmlns:xs='http://www.w3.org/2001/XMLSchema' ID='_d71a3a8e9fcc45c9e9d248ef7049393fc8f04e5f75' Version='2.0' IssueInstant='2014-07-17T01:01:48Z'>
+    <saml:Issuer>http://idp.example.com/metadata.php</saml:Issuer>
+    <saml:Subject>
+      <saml:NameID SPNameQualifier='http://sp.example.com/demo1/metadata.php' Format='urn:oasis:names:tc:SAML:2.0:nameid-format:transient'>_ce3d2948b4cf20146dee0a0b3dd6f69b6cf86f62d7</saml:NameID>
+      <saml:SubjectConfirmation Method='urn:oasis:names:tc:SAML:2.0:cm:bearer'>
+        <saml:SubjectConfirmationData NotOnOrAfter='2024-01-18T06:21:48Z' Recipient='http://sp.example.com/demo1/index.php?acs' InResponseTo='ONELOGIN_4fee3b046395c4e751011e97f8900b5273d56685'/>
+      </saml:SubjectConfirmation>
+    </saml:Subject>
+    <saml:Conditions NotBefore='2014-07-17T01:01:18Z' NotOnOrAfter='2024-01-18T06:21:48Z'>
+      <saml:AudienceRestriction>
+        <saml:Audience>http://sp.example.com/demo1/metadata.php</saml:Audience>
+      </saml:AudienceRestriction>
+    </saml:Conditions>
+    <saml:AuthnStatement AuthnInstant='2014-07-17T01:01:48Z' SessionNotOnOrAfter='2024-07-17T09:01:48Z' SessionIndex='_be9967abd904ddcae3c0eb4189adbe3f71e327cf93'>
+      <saml:AuthnContext>
+        <saml:AuthnContextClassRef>urn:oasis:names:tc:SAML:2.0:ac:classes:Password</saml:AuthnContextClassRef>
+      </saml:AuthnContext>
+    </saml:AuthnStatement>
+    <saml:AttributeStatement>
+      <saml:Attribute Name='uid' NameFormat='urn:oasis:names:tc:SAML:2.0:attrname-format:basic'>
+        <saml:AttributeValue xsi:type='xs:string'>test</saml:AttributeValue>
+      </saml:Attribute>
+      <saml:Attribute Name='mail' NameFormat='urn:oasis:names:tc:SAML:2.0:attrname-format:basic'>
+        <saml:AttributeValue xsi:type='xs:string'>test@example.com</saml:AttributeValue>
+      </saml:Attribute>
+      <saml:Attribute Name='eduPersonAffiliation' NameFormat='urn:oasis:names:tc:SAML:2.0:attrname-format:basic'>
+        <saml:AttributeValue xsi:type='xs:string'>users</saml:AttributeValue>
+        <saml:AttributeValue xsi:type='xs:string'>examplerole1</saml:AttributeValue>
+      </saml:Attribute>
+    </saml:AttributeStatement>
+  </saml:Assertion>
+</samlp:Response>

spec/lib/gitlab/auth/o_auth/user_spec.rb

@@ -779,4 +779,12 @@ describe Gitlab::Auth::OAuth::User do
       end
     end
   end
+
+  describe '#bypass_two_factor?' do
+    subject { oauth_user.bypass_two_factor? }
+
+    it 'returns always false' do
+      is_expected.to be_falsey
+    end
+  end
 end

spec/lib/gitlab/auth/saml/auth_hash_spec.rb

@@ -37,4 +37,55 @@ describe Gitlab::Auth::Saml::AuthHash do
       end
     end
   end
+
+  describe '#authn_context' do
+    let(:auth_hash_data) do
+      {
+        provider: 'saml',
+        uid: 'some_uid',
+        info:
+          {
+            name: 'mockuser',
+            email: 'mock@email.ch',
+            image: 'mock_user_thumbnail_url'
+          },
+        credentials:
+          {
+            token: 'mock_token',
+            secret: 'mock_secret'
+          },
+        extra:
+          {
+            raw_info:
+              {
+                info:
+                  {
+                    name: 'mockuser',
+                    email: 'mock@email.ch',
+                    image: 'mock_user_thumbnail_url'
+                  }
+              }
+          }
+      }
+    end
+
+    subject(:saml_auth_hash) { described_class.new(OmniAuth::AuthHash.new(auth_hash_data)) }
+
+    context 'with response_object' do
+      before do
+        auth_hash_data[:extra][:response_object] = { document:
+                                                         saml_xml(File.read('spec/fixtures/authentication/saml_response.xml')) }
+      end
+
+      it 'can extract authn_context' do
+        expect(saml_auth_hash.authn_context).to eq 'urn:oasis:names:tc:SAML:2.0:ac:classes:Password'
+      end
+    end
+
+    context 'without response_object' do
+      it 'returns an empty string' do
+        expect(saml_auth_hash.authn_context).to be_nil
+      end
+    end
+  end
 end

spec/lib/gitlab/auth/saml/user_spec.rb

@@ -400,4 +400,45 @@ describe Gitlab::Auth::Saml::User do
       end
     end
   end
+
+  describe '#bypass_two_factor?' do
+    let(:saml_config) { mock_saml_config_with_upstream_two_factor_authn_contexts }
+
+    subject { saml_user.bypass_two_factor? }
+
+    context 'with authn_contexts_worth_two_factors configured' do
+      before do
+        stub_omniauth_saml_config(enabled: true, auto_link_saml_user: true, allow_single_sign_on: ['saml'], providers: [saml_config])
+      end
+
+      it 'returns true when authn_context is worth two factors' do
+        allow(saml_user.auth_hash).to receive(:authn_context).and_return('urn:oasis:names:tc:SAML:2.0:ac:classes:SecondFactorOTPSMS')
+        is_expected.to be_truthy
+      end
+
+      it 'returns false when authn_context is not worth two factors' do
+        allow(saml_user.auth_hash).to receive(:authn_context).and_return('urn:oasis:names:tc:SAML:2.0:ac:classes:Password')
+        is_expected.to be_falsey
+      end
+
+      it 'returns false when authn_context is blank' do
+        is_expected.to be_falsey
+      end
+    end
+
+    context 'without auth_contexts_worth_two_factors_configured' do
+      before do
+        stub_omniauth_saml_config(enabled: true, auto_link_saml_user: true, allow_single_sign_on: ['saml'], providers: [mock_saml_config])
+      end
+
+      it 'returns false when authn_context is present' do
+        allow(saml_user.auth_hash).to receive(:authn_context).and_return('urn:oasis:names:tc:SAML:2.0:ac:classes:SecondFactorOTPSMS')
+        is_expected.to be_falsey
+      end
+
+      it 'returns false when authn_context is blank' do
+        is_expected.to be_falsey
+      end
+    end
+  end
 end

spec/support/helpers/login_helpers.rb

@@ -46,8 +46,8 @@ module LoginHelpers
     @current_user = user
   end
-  def gitlab_sign_in_via(provider, user, uid)
-    mock_auth_hash(provider, uid, user.email)
+  def gitlab_sign_in_via(provider, user, uid, saml_response = nil)
+    mock_auth_hash(provider, uid, user.email, saml_response)
     visit new_user_session_path
     click_link provider
   end
@@ -87,7 +87,7 @@ module LoginHelpers
     click_link "oauth-login-#{provider}"
   end
-  def mock_auth_hash(provider, uid, email)
+  def mock_auth_hash(provider, uid, email, saml_response = nil)
     # The mock_auth configuration allows you to set per-provider (or default)
     # authentication hashes to return during integration testing.
     OmniAuth.config.mock_auth[provider.to_sym] = OmniAuth::AuthHash.new({
@@ -109,12 +109,21 @@ module LoginHelpers
             email: email,
             image: 'mock_user_thumbnail_url'
           }
+        },
+        response_object: {
+          document: saml_xml(saml_response)
         }
       }
     })
     Rails.application.env_config['omniauth.auth'] = OmniAuth.config.mock_auth[provider.to_sym]
   end
+  def saml_xml(raw_saml_response)
+    return '' if raw_saml_response.blank?
+
+    XMLSecurity::SignedDocument.new(raw_saml_response, [])
+  end
+
   def mock_saml_config
     OpenStruct.new(name: 'saml', label: 'saml', args: {
       assertion_consumer_service_url: 'https://localhost:3443/users/auth/saml/callback',
@@ -125,6 +134,14 @@ module LoginHelpers
     })
   end
+  def mock_saml_config_with_upstream_two_factor_authn_contexts
+    config = mock_saml_config
+    config.args[:upstream_two_factor_authn_contexts] = %w(urn:oasis:names:tc:SAML:2.0:ac:classes:CertificateProtectedTransport
+                                                          urn:oasis:names:tc:SAML:2.0:ac:classes:SecondFactorOTPSMS
+                                                          urn:oasis:names:tc:SAML:2.0:ac:classes:SecondFactorIGTOKEN)
+    config
+  end
+
   def stub_omniauth_provider(provider, context: Rails.application)
     env = env_from_context(context)
@@ -140,13 +157,16 @@ module LoginHelpers
     env['omniauth.error.strategy'] = strategy
   end
-  def stub_omniauth_saml_config(messages)
-    set_devise_mapping(context: Rails.application)
-    Rails.application.routes.disable_clear_and_finalize = true
-    Rails.application.routes.draw do
+  def stub_omniauth_saml_config(messages,  context: Rails.application)
+    set_devise_mapping(context: context)
+    routes = Rails.application.routes
+    routes.disable_clear_and_finalize = true
+    routes.formatter.clear
+    routes.draw do
       post '/users/auth/saml' => 'omniauth_callbacks#saml'
     end
-    allow(Gitlab::Auth::OAuth::Provider).to receive_messages(providers: [:saml], config_for: mock_saml_config)
+    saml_config = messages.key?(:providers) ? messages[:providers].first : mock_saml_config
+    allow(Gitlab::Auth::OAuth::Provider).to receive_messages(providers: [:saml], config_for: saml_config)
     stub_omniauth_setting(messages)
     stub_saml_authorize_path_helpers
   end