Validate that SAML requests are originated from gitlab

If the request wasn't initiated by gitlab we shouldn't add the new
identity to the user, and instead show that we weren't able to link
the identity to the user.

This should fix: https://gitlab.com/gitlab-org/gitlab-ce/issues/56509

5 files changed, 191 insertions, 36 deletions

diff --git a/spec/controllers/omniauth_callbacks_controller_spec.rb b/spec/controllers/omniauth_callbacks_controller_spec.rb
index 6e374a8daa7..f41cd55ce8c 100644
--- a/spec/controllers/omniauth_callbacks_controller_spec.rb
+++ b/spec/controllers/omniauth_callbacks_controller_spec.rb
@@ -219,34 +219,70 @@ describe OmniauthCallbacksController, type: :controller do
   end
 
   describe '#saml' do
+    let(:last_request_id) { 'ONELOGIN_4fee3b046395c4e751011e97f8900b5273d56685' }
     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 }
 
+    def stub_last_request_id(id)
+      session['last_authn_request_id'] = id
+    end
+
     before do
+      stub_last_request_id(last_request_id)
       stub_omniauth_saml_config({ enabled: true, auto_link_saml_user: true, allow_single_sign_on: ['saml'],
                                   providers: [saml_config] })
       mock_auth_hash_with_saml_xml('saml', +'my-uid', user.email, mock_saml_response)
-      request.env["devise.mapping"] = Devise.mappings[:user]
+      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')
+    context 'with GitLab initiated request' do
+      before do
+        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
 
-      it 'expects user to be signed_in' do
-        expect(request.env['warden']).to be_authenticated
+      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
+        end
       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
+    context 'with IdP initiated request' do
+      let(:user) { create(:user) }
+      let(:last_request_id) { '99999' }
+
+      before do
+        sign_in user
+      end
+
+      it 'lets the user know their account isn\'t linked yet' do
+        post :saml, params: { SAMLResponse: mock_saml_response }
+
+        expect(flash[:notice]).to eq 'Request to link SAML account must be authorized'
+      end
+
+      it 'redirects to profile account page' do
+        post :saml, params: { SAMLResponse: mock_saml_response }
+
+        expect(response).to redirect_to(profile_account_path)
+      end
+
+      it 'doesn\'t link a new identity to the user' do
+        expect { post :saml, params: { SAMLResponse: mock_saml_response } }.not_to change { user.identities.count }
       end
     end
   end
diff --git a/spec/lib/gitlab/auth/saml/identity_linker_spec.rb b/spec/lib/gitlab/auth/saml/identity_linker_spec.rb
index 89118ff05ba..7912c8fb4b1 100644
--- a/spec/lib/gitlab/auth/saml/identity_linker_spec.rb
+++ b/spec/lib/gitlab/auth/saml/identity_linker_spec.rb
@@ -6,45 +6,61 @@ describe Gitlab::Auth::Saml::IdentityLinker do
   let(:user) { create(:user) }
   let(:provider) { 'saml' }
   let(:uid) { user.email }
-  let(:oauth) { { 'provider' => provider, 'uid' => uid } }
+  let(:in_response_to) { '12345' }
+  let(:saml_response) { instance_double(OneLogin::RubySaml::Response, in_response_to: in_response_to) }
+  let(:session) { { 'last_authn_request_id' => in_response_to } }
 
-  subject { described_class.new(user, oauth) }
+  let(:oauth) do
+    OmniAuth::AuthHash.new(provider: provider, uid: uid, extra: { response_object: saml_response })
+  end
 
-  context 'linked identity exists' do
-    let!(:identity) { user.identities.create!(provider: provider, extern_uid: uid) }
+  subject { described_class.new(user, oauth, session) }
 
-    it "doesn't create new identity" do
-      expect { subject.link }.not_to change { Identity.count }
-    end
+  context 'with valid GitLab initiated request' do
+    context 'linked identity exists' do
+      let!(:identity) { user.identities.create!(provider: provider, extern_uid: uid) }
 
-    it "sets #changed? to false" do
-      subject.link
+      it "doesn't create new identity" do
+        expect { subject.link }.not_to change { Identity.count }
+      end
 
-      expect(subject).not_to be_changed
-    end
-  end
+      it "sets #changed? to false" do
+        subject.link
 
-  context 'identity needs to be created' do
-    it 'creates linked identity' do
-      expect { subject.link }.to change { user.identities.count }
+        expect(subject).not_to be_changed
+      end
     end
 
-    it 'sets identity provider' do
-      subject.link
+    context 'identity needs to be created' do
+      it 'creates linked identity' do
+        expect { subject.link }.to change { user.identities.count }
+      end
 
-      expect(user.identities.last.provider).to eq provider
-    end
+      it 'sets identity provider' do
+        subject.link
 
-    it 'sets identity extern_uid' do
-      subject.link
+        expect(user.identities.last.provider).to eq provider
+      end
 
-      expect(user.identities.last.extern_uid).to eq uid
+      it 'sets identity extern_uid' do
+        subject.link
+
+        expect(user.identities.last.extern_uid).to eq uid
+      end
+
+      it 'sets #changed? to true' do
+        subject.link
+
+        expect(subject).to be_changed
+      end
     end
+  end
 
-    it 'sets #changed? to true' do
-      subject.link
+  context 'with identity provider initiated request' do
+    let(:session) { { 'last_authn_request_id' => nil } }
 
-      expect(subject).to be_changed
+    it 'attempting to link accounts raises an exception' do
+      expect { subject.link }.to raise_error(Gitlab::Auth::Saml::IdentityLinker::UnverifiedRequest)
     end
   end
 end
diff --git a/spec/lib/gitlab/auth/saml/origin_validator_spec.rb b/spec/lib/gitlab/auth/saml/origin_validator_spec.rb
new file mode 100644
index 00000000000..ae120b328ab
--- /dev/null
+++ b/spec/lib/gitlab/auth/saml/origin_validator_spec.rb
@@ -0,0 +1,42 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe Gitlab::Auth::Saml::OriginValidator do
+  let(:session) { instance_double(ActionDispatch::Request::Session) }
+
+  subject { described_class.new(session) }
+
+  describe '#store_origin' do
+    it 'stores the SAML request ID' do
+      request_id = double
+      authn_request = instance_double(OneLogin::RubySaml::Authrequest, uuid: request_id)
+
+      expect(session).to receive(:[]=).with('last_authn_request_id', request_id)
+
+      subject.store_origin(authn_request)
+    end
+  end
+
+  describe '#gitlab_initiated?' do
+    it 'returns false if InResponseTo is not present' do
+      saml_response = instance_double(OneLogin::RubySaml::Response, in_response_to: nil)
+
+      expect(subject.gitlab_initiated?(saml_response)).to eq(false)
+    end
+
+    it 'returns false if InResponseTo does not match stored value' do
+      saml_response = instance_double(OneLogin::RubySaml::Response, in_response_to: "abc")
+      allow(session).to receive(:[]).with('last_authn_request_id').and_return('123')
+
+      expect(subject.gitlab_initiated?(saml_response)).to eq(false)
+    end
+
+    it 'returns true if InResponseTo matches stored value' do
+      saml_response = instance_double(OneLogin::RubySaml::Response, in_response_to: "123")
+      allow(session).to receive(:[]).with('last_authn_request_id').and_return('123')
+
+      expect(subject.gitlab_initiated?(saml_response)).to eq(true)
+    end
+  end
+end
diff --git a/spec/lib/omni_auth/strategies/saml_spec.rb b/spec/lib/omni_auth/strategies/saml_spec.rb
new file mode 100644
index 00000000000..3c59de86d98
--- /dev/null
+++ b/spec/lib/omni_auth/strategies/saml_spec.rb
@@ -0,0 +1,22 @@
+require 'spec_helper'
+
+describe OmniAuth::Strategies::SAML, type: :strategy do
+  let(:idp_sso_target_url) { 'https://login.example.com/idp' }
+  let(:strategy) { [OmniAuth::Strategies::SAML, { idp_sso_target_url: idp_sso_target_url }] }
+
+  describe 'POST /users/auth/saml' do
+    it 'redirects to the provider login page' do
+      post '/users/auth/saml'
+
+      expect(last_response).to redirect_to(/\A#{Regexp.quote(idp_sso_target_url)}/)
+    end
+
+    it 'stores request ID during request phase' do
+      request_id = double
+      allow_any_instance_of(OneLogin::RubySaml::Authrequest).to receive(:uuid).and_return(request_id)
+
+      post '/users/auth/saml'
+      expect(session['last_authn_request_id']).to eq(request_id)
+    end
+  end
+end
diff --git a/spec/support/omniauth_strategy.rb b/spec/support/omniauth_strategy.rb
new file mode 100644
index 00000000000..eefa04bd9dd
--- /dev/null
+++ b/spec/support/omniauth_strategy.rb
@@ -0,0 +1,39 @@
+module StrategyHelpers
+  include Rack::Test::Methods
+  include ActionDispatch::Assertions::ResponseAssertions
+  include Shoulda::Matchers::ActionController
+  include OmniAuth::Test::StrategyTestCase
+
+  def post(*args)
+    super.tap do
+      @response = ActionDispatch::TestResponse.from_response(last_response)
+    end
+  end
+
+  def auth_hash
+    last_request.env['omniauth.auth']
+  end
+
+  def self.without_test_mode
+    original_mode = OmniAuth.config.test_mode
+    original_on_failure = OmniAuth.config.on_failure
+
+    OmniAuth.config.test_mode = false
+    OmniAuth.config.on_failure = OmniAuth::FailureEndpoint
+
+    yield
+  ensure
+    OmniAuth.config.test_mode = original_mode
+    OmniAuth.config.on_failure = original_on_failure
+  end
+end
+
+RSpec.configure do |config|
+  config.include StrategyHelpers, type: :strategy
+
+  config.around(:all, type: :strategy) do |example|
+    StrategyHelpers.without_test_mode do
+      example.run
+    end
+  end
+end