Introduce State Container

- Introduced a feature to set a custom StoreContainer, enabling users to define custom mechanics for storing and managing state in the application.
- This change addresses the known issue reported here: omniauth#58 (comment)

Author: DmitriiBochkarev

lib/omniauth-oauth2.rb

@@ -1,2 +1,3 @@
 require "omniauth-oauth2/version"
+require "omniauth/strategies/oauth2/state_container"
 require "omniauth/strategies/oauth2"

lib/omniauth/strategies/oauth2.rb

@@ -40,6 +40,7 @@ def self.inherited(subclass)
         },
         :code_challenge_method => "S256",
       }
+      option :state_container, StateContainer.new
 
       attr_accessor :access_token
 
@@ -60,7 +61,7 @@ def request_phase
       end
 
       def authorize_params # rubocop:disable Metrics/AbcSize, Metrics/MethodLength
-        options.authorize_params[:state] = SecureRandom.hex(24)
+        options.authorize_params[:state] = new_state
 
         if OmniAuth.config.test_mode
           @env ||= {}
@@ -72,7 +73,7 @@ def authorize_params # rubocop:disable Metrics/AbcSize, Metrics/MethodLength
                         .merge(pkce_authorize_params)
 
         session["omniauth.pkce.verifier"] = options.pkce_verifier if options.pkce
-        session["omniauth.state"] = params[:state]
+        options.state_container.store(self, params[:state])
 
         params
       end
@@ -83,7 +84,7 @@ def token_params
 
       def callback_phase # rubocop:disable Metrics/AbcSize, Metrics/CyclomaticComplexity, Metrics/MethodLength, Metrics/PerceivedComplexity
         error = request.params["error_reason"] || request.params["error"]
-        if !options.provider_ignores_state && (request.params["state"].to_s.empty? || request.params["state"] != session.delete("omniauth.state"))
+        if !options.provider_ignores_state && (request.params["state"].to_s.empty? || request.params["state"] != options.state_container.take(self))
           fail!(:csrf_detected, CallbackError.new(:csrf_detected, "CSRF detected"))
         elsif error
           fail!(error, CallbackError.new(request.params["error"], request.params["error_description"] || request.params["error_reason"], request.params["error_uri"]))
@@ -100,6 +101,10 @@ def callback_phase # rubocop:disable Metrics/AbcSize, Metrics/CyclomaticComplexi
         fail!(:failed_to_connect, e)
       end
 
+      def new_state
+        SecureRandom.hex(24)
+      end
+
     protected
 
       def pkce_authorize_params

lib/omniauth/strategies/oauth2/state_container.rb

@@ -0,0 +1,15 @@
+module OmniAuth
+  module Strategies
+    class OAuth2
+      class StateContainer
+        def store(oauth2, state)
+          oauth2.session["omniauth.state"] = state
+        end
+
+        def take(oauth2)
+          oauth2.session.delete("omniauth.state")
+        end
+      end
+    end
+  end
+end

spec/omniauth/strategies/oauth2/state_container_spec.rb

@@ -0,0 +1,29 @@
+require "helper"
+
+describe OmniAuth::Strategies::OAuth2::StateContainer do
+  let(:state) { "random_state" }
+  let(:oauth2) { double("OAuth2", session: {}) }
+
+  describe "#save_state" do
+    it "saves the state in the session" do
+      subject.store(oauth2, state)
+
+      expect(oauth2.session["omniauth.state"]).to eq(state)
+    end
+  end
+
+  describe "#take_state" do
+    before do
+      subject.store(oauth2, state)
+    end
+
+    it "removes the state from the session" do
+      expect(oauth2.session).to include("omniauth.state")
+
+      taken_state = subject.take(oauth2)
+
+      expect(oauth2.session).not_to include("omniauth.state")
+      expect(taken_state).to eq(state)
+    end
+  end
+end