Better error messages

app/controllers/concerns/authentication.rb

@@ -52,12 +52,24 @@ module Authentication
       # Extract root domain for cross-subdomain cookies (required for forward auth)
       domain = extract_root_domain(request.host)
 
-      cookie_options = {
-        value: session.id,
-        httponly: true,
-        same_site: :lax,
-        secure: Rails.env.production?
-      }
+      # Set cookie options based on environment
+      # Production: Use SameSite=None to allow cross-site cookies (needed for OIDC conformance testing)
+      # Development: Use SameSite=Lax since HTTPS might not be available
+      cookie_options = if Rails.env.production?
+        {
+          value: session.id,
+          httponly: true,
+          same_site: :none,  # Allow cross-site cookies for OIDC testing
+          secure: true        # Required for SameSite=None
+        }
+      else
+        {
+          value: session.id,
+          httponly: true,
+          same_site: :lax,
+          secure: false
+        }
+      end
 
       # Set domain for cross-subdomain authentication if we can extract it
       cookie_options[:domain] = domain if domain.present?

app/controllers/oidc_controller.rb

@@ -1,7 +1,8 @@
 class OidcController < ApplicationController
   # Discovery and JWKS endpoints are public
-  allow_unauthenticated_access only: [:discovery, :jwks, :token, :revoke, :userinfo, :logout]
-  skip_before_action :verify_authenticity_token, only: [:token, :revoke, :userinfo, :logout]
+  # authorize is also unauthenticated to handle prompt=none and prompt=login specially
+  allow_unauthenticated_access only: [:discovery, :jwks, :token, :revoke, :userinfo, :logout, :authorize]
+  skip_before_action :verify_authenticity_token, only: [:token, :revoke, :userinfo, :logout, :authorize, :consent]
 
   # Rate limiting to prevent brute force and abuse
   rate_limit to: 60, within: 1.minute, only: [:token, :revoke], with: -> {
@@ -43,7 +44,8 @@ class OidcController < ApplicationController
       ],
       code_challenge_methods_supported: ["plain", "S256"],
       backchannel_logout_supported: true,
-      backchannel_logout_session_supported: true
+      backchannel_logout_session_supported: true,
+      request_parameter_supported: false
     }
 
     render json: config
@@ -119,6 +121,18 @@ class OidcController < ApplicationController
     # per OAuth2 RFC 6749 Section 4.1.2.1
     # ============================================================================
 
+    # Reject request objects (JWT-encoded authorization parameters)
+    # Per OIDC Core §3.1.2.6: If request parameter is present and not supported,
+    # return request_not_supported error
+    if params[:request].present? || params[:request_uri].present?
+      Rails.logger.error "OAuth: Request object not supported"
+      error_uri = "#{redirect_uri}?error=request_not_supported"
+      error_uri += "&error_description=#{CGI.escape("Request objects are not supported")}"
+      error_uri += "&state=#{CGI.escape(state)}" if state.present?
+      redirect_to error_uri, allow_other_host: true
+      return
+    end
+
     # Validate response_type (now we can safely redirect with error)
     unless response_type == "code"
       Rails.logger.error "OAuth: Invalid response_type: #{response_type}"
@@ -162,7 +176,17 @@ class OidcController < ApplicationController
 
     # Check if user is authenticated
     unless authenticated?
-      # Store OAuth parameters in session and redirect to sign in
+      # Handle prompt=none - no UI allowed, return error immediately
+      # Per OIDC Core spec §3.1.2.6: If prompt=none and user not authenticated,
+      # return login_required error without showing any UI
+      if params[:prompt] == "none"
+        error_uri = "#{redirect_uri}?error=login_required"
+        error_uri += "&state=#{CGI.escape(state)}" if state.present?
+        redirect_to error_uri, allow_other_host: true
+        return
+      end
+
+      # Normal flow: store OAuth parameters and redirect to sign in
       session[:oauth_params] = {
         client_id: client_id,
         redirect_uri: redirect_uri,
@@ -172,10 +196,57 @@ class OidcController < ApplicationController
         code_challenge: code_challenge,
         code_challenge_method: code_challenge_method
       }
+      # Store the current URL (with all OAuth params) for redirect after authentication
+      session[:return_to_after_authenticating] = request.url
       redirect_to signin_path, alert: "Please sign in to continue"
       return
     end
 
+    # Handle prompt=login - force re-authentication
+    # Per OIDC Core spec §3.1.2.1: If prompt=login, the Authorization Server MUST prompt
+    # the End-User for reauthentication, even if the End-User is currently authenticated
+    if params[:prompt] == "login"
+      # Destroy current session to force re-authentication
+      # This creates a fresh authentication event with a new auth_time
+      Current.session&.destroy!
+
+      # Clear the session cookie so the user is truly logged out
+      cookies.delete(:session_id)
+
+      # Store the current URL (which contains all OAuth params) for redirect after login
+      # Remove prompt=login to prevent infinite re-auth loop
+      return_url = request.url.sub(/&prompt=login(?=&|$)|\?prompt=login&?/, '\1')
+      # Fix any resulting URL issues (like ?& or & at end)
+      return_url = return_url.gsub("?&", "?").gsub(/[?&]$/, "")
+      session[:return_to_after_authenticating] = return_url
+
+      redirect_to signin_path, alert: "Please sign in to continue"
+      return
+    end
+
+    # Handle max_age - require re-authentication if session is too old
+    # Per OIDC Core spec §3.1.2.1: If max_age is provided and the auth time is older,
+    # the Authorization Server MUST prompt for reauthentication
+    if params[:max_age].present?
+      max_age_seconds = params[:max_age].to_i
+      # Calculate session age
+      session_age_seconds = Time.current.to_i - Current.session.created_at.to_i
+
+      if session_age_seconds > max_age_seconds
+        # Session is too old - require re-authentication
+        # Store return URL in session (creates new session cookie)
+
+        # Destroy session and clear cookie to force fresh login
+        Current.session&.destroy!
+        cookies.delete(:session_id)
+
+        session[:return_to_after_authenticating] = request.url
+
+        redirect_to signin_path, alert: "Please sign in to continue"
+        return
+      end
+    end
+
     # Get the authenticated user
     user = Current.session.user
 
@@ -468,6 +539,10 @@ class OidcController < ApplicationController
           scopes: auth_code.scope
         )
 
+        # RFC6749-5.1: Token endpoint MUST return Cache-Control: no-store
+        response.headers["Cache-Control"] = "no-store"
+        response.headers["Pragma"] = "no-cache"
+
         # Return tokens
         render json: {
           access_token: access_token_record.plaintext_token,  # Opaque token
@@ -597,6 +672,10 @@ class OidcController < ApplicationController
       scopes: refresh_token_record.scope
     )
 
+    # RFC6749-5.1: Token endpoint MUST return Cache-Control: no-store
+    response.headers["Cache-Control"] = "no-store"
+    response.headers["Pragma"] = "no-cache"
+
     # Return new tokens
     render json: {
       access_token: new_access_token.plaintext_token,  # Opaque token
@@ -695,6 +774,10 @@ class OidcController < ApplicationController
     application = access_token.application
     claims.merge!(application.custom_claims_for_user(user))
 
+    # Security: Don't cache user data responses
+    response.headers["Cache-Control"] = "no-store"
+    response.headers["Pragma"] = "no-cache"
+
     render json: claims
   end
 
@@ -839,12 +922,12 @@ class OidcController < ApplicationController
       }
     end
 
-    # Validate code verifier format (base64url-encoded, 43-128 characters)
-    unless code_verifier.match?(/\A[A-Za-z0-9\-_]{43,128}\z/)
+    # Validate code verifier format (per RFC 7636: [A-Za-z0-9\-._~], 43-128 characters)
+    unless code_verifier.match?(/\A[A-Za-z0-9\.\-_~]{43,128}\z/)
       return {
         valid: false,
         error: "invalid_request",
-        error_description: "Invalid code_verifier format. Must be 43-128 characters of base64url encoding",
+        error_description: "Invalid code_verifier format. Must be 43-128 characters [A-Z/a-z/0-9/-/./_/~]",
         status: :bad_request
       }
     end

app/controllers/sessions_controller.rb

@@ -14,6 +14,20 @@ class SessionsController < ApplicationController
       return
     end
 
+    # Extract login_hint from the return URL for pre-filling the email field (OIDC spec)
+    @login_hint = nil
+    if session[:return_to_after_authenticating].present?
+      begin
+        uri = URI.parse(session[:return_to_after_authenticating])
+        if uri.query.present?
+          query_params = CGI.parse(uri.query)
+          @login_hint = query_params["login_hint"]&.first
+        end
+      rescue URI::InvalidURIError
+        # Ignore parsing errors
+      end
+    end
+
     respond_to do |format|
       format.html # render HTML login page
       format.json { render json: {error: "Authentication required"}, status: :unauthorized }
@@ -73,7 +87,10 @@ class SessionsController < ApplicationController
 
     # Sign in successful (password only)
     start_new_session_for user, acr: "1"
-    redirect_to after_authentication_url, notice: "Signed in successfully.", allow_other_host: true
+
+    # Use status: :see_other to ensure browser makes a GET request
+    # This prevents Turbo from converting it to a TURBO_STREAM request
+    redirect_to after_authentication_url, notice: "Signed in successfully.", allow_other_host: true, status: :see_other
   end
 
   def verify_totp

app/views/sessions/new.html.erb

@@ -12,7 +12,7 @@
           autofocus: true,
           autocomplete: "username",
           placeholder: "your@email.com",
-          value: params[:email_address],
+          value: @login_hint || params[:email_address],
           data: { action: "blur->webauthn#checkWebAuthnSupport change->webauthn#checkWebAuthnSupport" },
           class: "block shadow-sm rounded-md border border-gray-400 focus:outline-blue-600 px-3 py-2 mt-2 w-full" %>
     </div>

config/routes.rb

@@ -26,7 +26,7 @@ Rails.application.routes.draw do
   # OIDC (OpenID Connect) routes
   get "/.well-known/openid-configuration", to: "oidc#discovery"
   get "/.well-known/jwks.json", to: "oidc#jwks"
-  get "/oauth/authorize", to: "oidc#authorize"
+  match "/oauth/authorize", to: "oidc#authorize", via: [:get, :post]
   post "/oauth/authorize/consent", to: "oidc#consent", as: :oauth_consent
   post "/oauth/token", to: "oidc#token"
   post "/oauth/revoke", to: "oidc#revoke"