Fix RelyingParty#origin returning always nil

CHANGELOG.md

@@ -1,5 +1,11 @@
 # Changelog
 
+## Unreleased
+
+### Fixed
+
+- Update `RelyingParty#origin` and `WebAuthn.configuration.origin` to return the allowed origin if allowed origins has only one element.
+
 ## [v3.4.2] - 2025-09-22
 
 ### Added

lib/webauthn/relying_party.rb

@@ -54,7 +54,7 @@ def initialize(
                   :acceptable_attestation_types,
                   :legacy_u2f_appid
 
-    attr_reader :attestation_root_certificates_finders, :origin
+    attr_reader :attestation_root_certificates_finders
 
     # This is the user-data encoder.
     # Used to decode user input and to encode data provided to the user.
@@ -121,6 +121,17 @@ def verify_authentication(
       end
     end
 
+    # DEPRECATED: This method will be removed in future.
+    def origin
+      warn(
+        "DEPRECATION WARNING: `WebAuthn.origin` is deprecated and will be removed in future. "\
+        "Please use `WebAuthn.allowed_origins` instead "\
+        "that also allows configuring multiple origins per Relying Party"
+      )
+
+      allowed_origins.first if allowed_origins&.size == 1
+    end
+
     # DEPRECATED: This method will be removed in future.
     def origin=(new_origin)
       return if new_origin.nil?

spec/webauthn/relying_party_spec.rb

@@ -135,6 +135,42 @@
     end
   end
 
+  describe '#origin' do
+    subject do
+      old_verbose, $VERBOSE = $VERBOSE, nil # Silence warnings to avoid deprecation warnings
+
+      rp.origin
+    ensure
+      $VERBOSE = old_verbose
+    end
+
+    context 'when relying party has only one allowed origin' do
+      let(:rp) do
+        WebAuthn::RelyingParty.new(allowed_origins: ["https://admin.example.test"])
+      end
+
+      it 'returns that allowed origin' do
+        is_expected.to eq("https://admin.example.test")
+      end
+    end
+
+    context 'when relying party has multiple allowed origins' do
+      let(:rp) do
+        WebAuthn::RelyingParty.new(allowed_origins: ["https://admin.example.test", "https://newadmin.example.test"])
+      end
+
+      it { is_expected.to be_nil }
+    end
+
+    context 'when relying party has not set its allowed origins' do
+      let(:rp) do
+        WebAuthn::RelyingParty.new(allowed_origins: nil)
+      end
+
+      it { is_expected.to be_nil }
+    end
+  end
+
   context "without having any global configuration" do
     let(:consumer_rp) do
       WebAuthn::RelyingParty.new(