add SwWebhookAuthentication middleware

lib/rack/signalwire_webhook_authentication.rb

@@ -0,0 +1,53 @@
+# frozen_string_literal: true
+
+require 'rack/media_type'
+
+module Rack
+
+  class SwWebhookAuthentication
+
+    FORM_URLENCODED_MEDIA_TYPE = Rack::MediaType.type('application/x-www-form-urlencoded')
+
+    def initialize(app, private_key, *paths, &private_key_lookup)
+      @app = app
+      @private_key = private_key
+      define_singleton_method(:get_private_key, private_key_lookup) if block_given?
+      @path_regex = Regexp.union(paths)
+    end
+
+    def call(env)
+      return @app.call(env) unless env['PATH_INFO'].match(@path_regex)
+      request = Rack::Request.new(env)
+      original_url = request.url
+      params = extract_params!(request)
+      private_key = @private_key || get_private_key(params['AccountSid'])
+      validator = Signalwire::Webhook::ValidateRequest.new(private_key)
+      signature = env['HTTP_X_SIGNALWIRE_SIGNATURE'] || env['HTTP_X_TWILIO_SIGNATURE'] || ''
+      if validator.validate(original_url, params, signature)
+        @app.call(env)
+      else
+        [
+          403,
+          { 'Content-Type' => 'text/plain' },
+          ['Signalwire Request Validation Failed.']
+        ]
+      end
+    end
+
+    def extract_params!(request)
+      return {} unless request.post?
+
+      if request.media_type == FORM_URLENCODED_MEDIA_TYPE
+        request.POST
+      else
+        request.body.rewind
+        body = request.body.read
+        request.body.rewind
+        body
+      end
+    end
+
+    private :extract_params!
+
+  end
+end

signalwire.gemspec

@@ -27,6 +27,7 @@ Gem::Specification.new do |spec|
   spec.add_development_dependency 'bundler', '~> 2.1'
   spec.add_development_dependency 'bundler-audit', '~> 0.6'
   spec.add_development_dependency 'guard-rspec', '~> 4.7'
+  spec.add_development_dependency 'rack', '~> 2.0'
   spec.add_development_dependency 'rake', '~> 13.0'
   spec.add_development_dependency 'rdoc', '~> 6.1'
   spec.add_development_dependency 'rspec', '~> 3.0'

spec/rack/signalwire_webhook_authentication_spec.rb

@@ -0,0 +1,197 @@
+require 'spec_helper'
+require 'rack/mock'
+require 'rack/signalwire_webhook_authentication'
+
+describe Rack::SwWebhookAuthentication do
+  before do
+    @app = ->(_env) { [200, { 'Content-Type' => 'text/plain' }, ['Hello']] }
+  end
+
+  describe 'new' do
+    it 'should initialize with an app, auth token and a path' do
+      expect do
+        Rack::SwWebhookAuthentication.new(@app, 'ABC', /\/voice/)
+      end.not_to raise_error
+    end
+
+    it 'should initialize with an app, auth token and paths' do
+      expect do
+        Rack::SwWebhookAuthentication.new(@app, 'ABC', /\/voice/, /\/sms/)
+      end.not_to raise_error
+    end
+
+    it 'should initialize with an app, dynamic token and paths' do
+      expect do
+        Rack::SwWebhookAuthentication.new(@app, nil, /\/voice/, /\/sms/)
+      end.not_to raise_error
+    end
+  end
+
+  describe 'calling against one path with dynamic auth token' do
+    it 'should allow a request through if it validates' do
+      auth_token = 'qwerty'
+      account_sid = 12_345
+      expect_any_instance_of(Rack::Request).to receive(:post?).and_return(true)
+      expect_any_instance_of(Rack::Request).to receive(:media_type).and_return(Rack::MediaType.type('application/x-www-form-urlencoded'))
+      expect_any_instance_of(Rack::Request).to receive(:POST).and_return({ 'AccountSid' => account_sid })
+      @middleware = Rack::SwWebhookAuthentication.new(@app, nil, /\/voice/) { |asid| auth_token }
+      request_validator = double('RequestValidator')
+      expect(Twilio::Security::RequestValidator).to receive(:new).with(auth_token).and_return(request_validator)
+      expect(request_validator).to receive(:validate).and_return(true)
+      request = Rack::MockRequest.env_for('/voice')
+      status, headers, body = @middleware.call(request)
+      expect(status).to be(200)
+    end
+  end
+
+  describe 'calling against one path' do
+    before do
+      @middleware = Rack::SwWebhookAuthentication.new(@app, 'ABC', /\/voice/)
+    end
+
+    it 'should not intercept when the path doesn\'t match' do
+      expect_any_instance_of(Twilio::Security::RequestValidator).to_not receive(:validate)
+      request = Rack::MockRequest.env_for('/sms')
+      status, headers, body = @middleware.call(request)
+      expect(status).to be(200)
+    end
+
+    it 'should allow a request through if it validates' do
+      expect_any_instance_of(Twilio::Security::RequestValidator).to(
+        receive(:validate).and_return(true)
+      )
+      request = Rack::MockRequest.env_for('/voice')
+      status, headers, body = @middleware.call(request)
+      expect(status).to be(200)
+    end
+
+    it 'should short circuit a request to 403 if it does not validate' do
+      expect_any_instance_of(Twilio::Security::RequestValidator).to(
+        receive(:validate).and_return(false)
+      )
+      request = Rack::MockRequest.env_for('/voice')
+      status, headers, body = @middleware.call(request)
+      expect(status).to be(403)
+    end
+  end
+
+  describe 'calling against many paths' do
+    before do
+      @middleware = Rack::SwWebhookAuthentication.new(@app, 'ABC', /\/voice/, /\/sms/)
+    end
+
+    it 'should not intercept when the path doesn\'t match' do
+      expect_any_instance_of(Twilio::Security::RequestValidator).to_not receive(:validate)
+      request = Rack::MockRequest.env_for('icesms')
+      status, headers, body = @middleware.call(request)
+      expect(status).to be(200)
+    end
+
+    it 'shold allow a request through if it validates' do
+      expect_any_instance_of(Twilio::Security::RequestValidator).to(
+        receive(:validate).and_return(true)
+      )
+      request = Rack::MockRequest.env_for('/sms')
+      status, headers, body = @middleware.call(request)
+      expect(status).to be(200)
+    end
+
+    it 'should short circuit a request to 403 if it does not validate' do
+      expect_any_instance_of(Twilio::Security::RequestValidator).to(
+        receive(:validate).and_return(false)
+      )
+      request = Rack::MockRequest.env_for('/sms')
+      status, headers, body = @middleware.call(request)
+      expect(status).to be(403)
+    end
+  end
+
+  describe 'validating non-form-data POST payloads' do
+    it 'should fail if the body does not validate' do
+      middleware = Rack::SwWebhookAuthentication.new(@app, 'qwerty', /\/test/)
+      input = StringIO.new('{"message": "a post body that does not match the bodySHA256"}')
+
+      request = Rack::MockRequest.env_for(
+        'https://example.com/test?bodySHA256=79bfb0acaf0045fd30f13d48d4fe296b393d85a3bfbee881a0172b2bd574b11e',
+        method: 'POST',
+        input: input
+      )
+      request['HTTP_X_TWILIO_SIGNATURE'] = '+LYlbGr/VmN84YPJQCuWs+9UA7E='
+      request['CONTENT_TYPE'] = 'application/json'
+
+      status, headers, body = middleware.call(request)
+
+      expect(status).not_to be(200)
+    end
+
+    it 'should validate if the body signature is correct' do
+      middleware = Rack::SwWebhookAuthentication.new(@app, 'qwerty', /\/test/)
+      input = StringIO.new('{"message": "a post body"}')
+
+      request = Rack::MockRequest.env_for(
+        'https://example.com/test?bodySHA256=8d90d640c6ba47d595ac56203d7f5c6b511be80fdf44a2055acca75a119b9fd2',
+        method: 'POST',
+        input: input
+      )
+      request['HTTP_X_SIGNALWIRE_SIGNATURE'] = 'zR5Oq4f6cijN5oz5bisiVuxYnTU='
+      request['CONTENT_TYPE'] = 'application/json'
+
+      status, headers, body = middleware.call(request)
+
+      expect(status).to be(200)
+    end
+
+    it 'should validate even if a previous middleware read the body first' do
+      middleware = Rack::SwWebhookAuthentication.new(@app, 'qwerty', /\/test/)
+      input = StringIO.new('{"message": "a post body"}')
+
+      request = Rack::MockRequest.env_for(
+        'https://example.com/test?bodySHA256=8d90d640c6ba47d595ac56203d7f5c6b511be80fdf44a2055acca75a119b9fd2',
+        method: 'POST',
+        input: input
+      )
+      request['HTTP_X_SIGNALWIRE_SIGNATURE'] = 'zR5Oq4f6cijN5oz5bisiVuxYnTU='
+      request['CONTENT_TYPE'] = 'application/json'
+      request['rack.input'].read
+
+      status, headers, body = middleware.call(request)
+
+      expect(status).to be(200)
+    end
+  end
+
+  describe 'validating application/x-www-form-urlencoded POST payloads' do
+    it 'should fail if the body does not validate' do
+      middleware = Rack::SwWebhookAuthentication.new(@app, 'qwerty', /\/test/)
+
+      request = Rack::MockRequest.env_for(
+        'https://example.com/test',
+        method: 'POST',
+        params: { 'foo' => 'bar' }
+      )
+      request['HTTP_X_SIGNALWIRE_SIGNATURE'] = 'foobarbaz'
+      expect(request['CONTENT_TYPE']).to eq('application/x-www-form-urlencoded')
+
+      status, headers, body = middleware.call(request)
+
+      expect(status).not_to be(200)
+    end
+
+    it 'should validate if the body signature is correct' do
+      middleware = Rack::SwWebhookAuthentication.new(@app, 'qwerty', /\/test/)
+
+      request = Rack::MockRequest.env_for(
+        'https://example.com/test',
+        method: 'POST',
+        params: { 'foo' => 'bar' }
+      )
+      request['HTTP_X_SIGNALWIRE_SIGNATURE'] = 'TR9Skm9jiF4WVRJznU5glK5I83k='
+      expect(request['CONTENT_TYPE']).to eq('application/x-www-form-urlencoded')
+
+      status, headers, body = middleware.call(request)
+
+      expect(status).to be(200)
+    end
+
+  end
+end

spec/spec_helper.rb

@@ -5,6 +5,7 @@
 
 %w[
   bundler/setup
+  rack
   signalwire
   webmock/rspec
   vcr