diff --git a/.github/dependabot.yml b/.github/dependabot.yml
new file mode 100644
index 0000000..ca79ca5
--- /dev/null
+++ b/.github/dependabot.yml
@@ -0,0 +1,6 @@
+version: 2
+updates:
+  - package-ecosystem: github-actions
+    directory: /
+    schedule:
+      interval: weekly
diff --git a/.github/workflows/legacy_ruby.yml b/.github/workflows/legacy_ruby.yml
new file mode 100644
index 0000000..39ae42c
--- /dev/null
+++ b/.github/workflows/legacy_ruby.yml
@@ -0,0 +1,28 @@
+name: Legacy Ruby specs
+
+on:
+  push:
+    branches: [ master, develop ]
+  pull_request:
+    branches: [ master, develop ]
+
+permissions:
+  contents: read
+
+jobs:
+  test:
+    name: Specs
+    runs-on: ubuntu-20.04
+    strategy:
+      matrix:
+        ruby-version: ['2.1', '2.2', '2.3', '2.4', '2.5', '2.6']
+
+    steps:
+    - uses: actions/checkout@v4
+    - name: Set up Ruby
+      uses: ruby/setup-ruby@v1
+      with:
+        ruby-version: ${{ matrix.ruby-version }}
+        bundler-cache: true
+    - name: Run specs
+      run: bundle exec rake
diff --git a/.github/workflows/ruby.yml b/.github/workflows/ruby.yml
new file mode 100644
index 0000000..297bc39
--- /dev/null
+++ b/.github/workflows/ruby.yml
@@ -0,0 +1,35 @@
+name: Ruby specs
+
+on:
+  push:
+    branches: [ master, develop ]
+  pull_request:
+    branches: [ master, develop ]
+
+permissions:
+  contents: read
+
+jobs:
+  test:
+    name: Specs
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        ruby-version: ['2.7', '3.0', '3.1', '3.2']
+        channel: ['stable']
+
+        include:
+          - ruby-version: 'head'
+            channel: ['experimental']
+
+    continue-on-error: ${{ matrix.channel != 'stable' }}
+
+    steps:
+    - uses: actions/checkout@v4
+    - name: Set up Ruby
+      uses: ruby/setup-ruby@v1
+      with:
+        ruby-version: ${{ matrix.ruby-version }}
+        bundler-cache: true
+    - name: Run specs
+      run: bundle exec rake
diff --git a/.travis.yml b/.travis.yml
deleted file mode 100644
index 58d55a8..0000000
--- a/.travis.yml
+++ /dev/null
@@ -1,21 +0,0 @@
-dist: xenial
-os: linux
-language: ruby
-rvm:
-  - 2.1
-  - 2.2
-  - 2.3
-  - 2.4
-  - 2.5
-  - 2.6
-  - 2.7
-  - ruby-edge
-branches:
-  only:
-    - master
-before_install:
-  - gem uninstall -v '>= 2' -i $(rvm gemdir)@global -ax bundler || true
-  - gem install bundler -v '< 2'
-jobs:
-  allow_failures:
-  - rvm: ruby-edge
diff --git a/CHANGELOG.md b/CHANGELOG.md
index a5ddaaf..682d477 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,8 +2,8 @@
 
 All notable changes to this project will be documented in this file.
 
-The format is based on [Keep a Changelog](http://keepachangelog.com/) and this
-project adheres to [Semantic Versioning](http://semver.org/)
+The format is based on [Keep a Changelog](https://keepachangelog.com/) and this
+project adheres to [Semantic Versioning](https://semver.org/)
 
 ## 2.0.0 - 2010-11-14
 
@@ -17,6 +17,19 @@ project adheres to [Semantic Versioning](http://semver.org/)
 * Forward success response to `fetch_raw_info` callback ([#51](https://github.com/dlindahl/omniauth-cas/pull/51))
 * Relax development dependencies to the latest versions
 
+## 1.2.1 (IFAD) - 2018-11-27
+
+### Changed
+
+* Safer request.host call
+
+## 1.2.0 (IFAD) - 2018-11-27
+
+### Added
+
+* service_validator: use custom callback_url if provided
+* Add url_by_request_host option
+
 ## 1.1.1 - 2016-09-19
 
 ### Changed
diff --git a/Gemfile b/Gemfile
index 1c04832..d4295d7 100644
--- a/Gemfile
+++ b/Gemfile
@@ -1,4 +1,5 @@
 source 'https://rubygems.org'
+gem 'byebug'
 
 # Specify your gem's dependencies in omniauth-cas.gemspec
 gemspec
diff --git a/README.md b/README.md
index d291d40..da38f64 100644
--- a/README.md
+++ b/README.md
@@ -1,9 +1,10 @@
-# OmniAuth CAS Strategy [![Gem Version][version_badge]][version] [![Build Status][travis_status]][travis]
+# OmniAuth CAS Strategy [![Gem Version][version_badge]][version] [![Build Status][github_actions_status]][github_actions] [![Build Status][github_legacy_actions_status]][github_actions]
 
 [version_badge]: https://badge.fury.io/rb/omniauth-cas.svg
 [version]: https://badge.fury.io/rb/omniauth-cas
-[travis]: https://travis-ci.org/dlindahl/omniauth-cas
-[travis_status]: https://secure.travis-ci.org/dlindahl/omniauth-cas.svg
+[github_actions]: https://github.com/ifad/omniauth-cas/actions
+[github_actions_status]: https://github.com/ifad/omniauth-cas/actions/workflows/ruby.yml/badge.svg
+[github_actions_legacy_status]: https://github.com/ifad/omniauth-cas/actions/workflows/legacy_ruby.yml/badge.svg
 [releases]: https://github.com/dlindahl/omniauth-cas/releases
 
 This is a OmniAuth 1.0 compatible port of the previously available
@@ -74,6 +75,19 @@ Other configuration options:
         extra_info
       }
     ```
+  * `url_by_request_host` - Optional. Hash keyed by request host, to use
+    different CAS Server URLs depending on the request host. *Requires* `url`
+    or `host` to be set anyway, that'll be used as defaults if no host
+    matches.
+
+    ```ruby
+    provider :cas,
+             url: 'https://cas.example.org',
+             url_by_request_host: {
+               'host1.example.org' => 'https://host1.cas.example.org',
+               'host2.example.org' => 'https://host2.cas.example.org',
+             }
+    ```
 
 Configurable options for values returned by CAS:
 
diff --git a/lib/omniauth/strategies/cas.rb b/lib/omniauth/strategies/cas.rb
index 3b00a0b..19a866d 100644
--- a/lib/omniauth/strategies/cas.rb
+++ b/lib/omniauth/strategies/cas.rb
@@ -9,6 +9,8 @@ class CAS
       # Custom Exceptions
       class MissingCASTicket < StandardError; end
       class InvalidCASTicket < StandardError; end
+      class MissingReturnURL < StandardError; end
+      class InvalidReturnURL < StandardError; end
 
       autoload :ServiceTicketValidator, 'omniauth/strategies/cas/service_ticket_validator'
       autoload :LogoutRequest, 'omniauth/strategies/cas/logout_request'
@@ -91,14 +93,18 @@ def callback_phase
       def request_phase
         service_url = append_params(callback_url, return_url)
 
-        [
-          302,
-          {
-            'Location' => login_url(service_url),
-            'Content-Type' => 'text/plain'
-          },
-          ["You are being redirected to CAS for sign-in."]
-        ]
+        if validate_service_url!(service_url)
+          [
+            302,
+            {
+              'Location' => login_url(service_url),
+              'Content-Type' => 'text/plain'
+            },
+            ["You are being redirected to CAS for sign-in."]
+          ]
+        else
+          [ 400, {}, [ "Bad request" ] ]
+        end
       end
 
       def on_sso_path?
@@ -115,14 +121,30 @@ def single_sign_out_phase
       def cas_url
         extract_url if options['url']
         validate_cas_setup
-        @cas_url ||= begin
-          uri = Addressable::URI.new
-          uri.host = options.host
-          uri.scheme = options.ssl ? 'https' : 'http'
-          uri.port = options.port
-          uri.path = options.path
-          uri.to_s
-        end
+
+        by_host_cas_url || static_cas_url
+      end
+
+      def by_host_cas_url
+        return unless options.url_by_request_host && \
+          options.url_by_request_host.respond_to?(:fetch)
+
+        uri = options.url_by_request_host.fetch(request.host)
+
+        Addressable::URI.parse(uri).to_s
+      rescue
+        nil # When request.host is not defined or it raises,
+            # or when Addressable raises, we can only resort
+            # to the default.
+      end
+
+      def static_cas_url
+        uri = Addressable::URI.new
+        uri.host = options.host
+        uri.scheme = options.ssl ? 'https' : 'http'
+        uri.port = options.port
+        uri.path = options.path
+        uri.to_s
       end
 
       def extract_url
@@ -141,6 +163,33 @@ def validate_cas_setup
         end
       end
 
+      # Checks that the callback URL is within the scope of the target
+      # service url, to protect against redirects to phishing pages.
+      #
+      def validate_service_url!(service_url)
+        service_url = Addressable::URI.parse(service_url)
+
+        return_url = service_url.query_values['url']
+
+        if return_url.nil? || return_url.empty?
+          fail!(:missing_return_url, MissingReturnURL.new('Missing Return URL'))
+          return false
+        end
+
+        return_url = Addressable::URI.parse(return_url)
+
+        # Check that the return URL host, if present, is equal to the service
+        # URL host. If the return_url host is nil, it means this is a relative
+        # url - and we can accept it.
+        #
+        if !return_url.host.nil? && (return_url.host != service_url.host)
+          fail!(:invalid_return_url, InvalidReturnURL.new('Invalid Return URL'))
+          return false
+        end
+
+        return true
+      end
+
       # Build a service-validation URL from +service+ and +ticket+.
       # If +service+ has a ticket param, first remove it. URL-encode
       # +service+ and add it and the +ticket+ as paraemters to the
diff --git a/spec/omniauth/strategies/cas_spec.rb b/spec/omniauth/strategies/cas_spec.rb
index 422f932..3efe7e4 100644
--- a/spec/omniauth/strategies/cas_spec.rb
+++ b/spec/omniauth/strategies/cas_spec.rb
@@ -80,6 +80,42 @@
         expect(provider.options).to include path:'/a/path'
       end
     end
+
+    context 'with a URL by host mapping' do
+      let(:params) { super().merge(
+        url: 'https://default.cas.host',
+        url_by_request_host: {
+          'host1.example.org' => 'https://host1.cas.host',
+          'host2.example.org' => 'https://host2.cas.host',
+        })
+      }
+
+      let(:request_host) { nil }
+
+      before do
+        allow_any_instance_of(MyCasProvider)
+          .to receive(:request)
+          .and_return(Rack::Request.new('HTTP_HOST' => request_host))
+      end
+
+      it { true }
+
+      context 'and an host in the map' do
+        let(:request_host) { 'host1.example.org' }
+
+        it 'returns the corresponding CAS host in the map' do
+          expect(subject).to eq('https://host1.cas.host')
+        end
+      end
+
+      context 'and an host not in the map' do
+        let(:request_host) { 'foo.bar' }
+
+        it 'returns the default CAS host' do
+          expect(subject).to eq('https://default.cas.host')
+        end
+      end
+    end
   end
 
   describe 'defaults' do
@@ -89,7 +125,15 @@
   end
 
   describe 'GET /auth/cas' do
-    let(:return_url) { 'http://myapp.com/admin/foo' }
+    let(:return_url) { 'http://example.org/admin/foo' }
+
+    context 'with a return url on a different host than the service url' do
+      before { get '/auth/cas?url=http://attack.example.org/' }
+
+      subject { last_response }
+
+      it { should be_bad_request }
+    end
 
     context 'with a referer' do
       let(:url) { '/auth/cas' }