HTTP signatures (#4146)

* Add Request class with HTTP signature generator

Spec: https://tools.ietf.org/html/draft-cavage-http-signatures-06

* Add HTTP signature verification concern

* Add test for SignatureVerification concern

* Add basic test for Request class

* Make PuSH subscribe/unsubscribe requests use new Request class

Accidentally fix lease_seconds not being set and sent properly, and
change the new minimum subscription duration to 1 day

* Make all PuSH workers use new Request class

* Make Salmon sender use new Request class

* Make FetchLinkService use new Request class

* Make FetchAtomService use the new Request class

* Make Remotable use the new Request class

* Make ResolveRemoteAccountService use the new Request class

* Add more tests

* Allow +-30 seconds window for signed request to remain valid

* Disable time window validation for signed requests, restore 7 days
as PuSH subscription duration (which was previous default due to a bug)

spec/controllers/concerns/signature_verification_spec.rb

@@ -0,0 +1,74 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+describe ApplicationController, type: :controller do
+  controller do
+    include SignatureVerification
+
+    def success
+      head 200
+    end
+
+    def alternative_success
+      head 200
+    end
+  end
+
+  before do
+    routes.draw { get 'success' => 'anonymous#success' }
+  end
+
+  context 'without signature header' do
+    before do
+      get :success
+    end
+
+    describe '#signed_request?' do
+      it 'returns false' do
+        expect(controller.signed_request?).to be false
+      end
+    end
+
+    describe '#signed_request_account' do
+      it 'returns nil' do
+        expect(controller.signed_request_account).to be_nil
+      end
+    end
+  end
+
+  context 'with signature header' do
+    let!(:author) { Fabricate(:account) }
+
+    before do
+      get :success
+
+      fake_request = Request.new(:get, request.url)
+      fake_request.on_behalf_of(author)
+
+      request.headers.merge!(fake_request.headers)
+    end
+
+    describe '#signed_request?' do
+      it 'returns true' do
+        expect(controller.signed_request?).to be true
+      end
+    end
+
+    describe '#signed_request_account' do
+      it 'returns an account' do
+        expect(controller.signed_request_account).to eq author
+      end
+
+      it 'returns nil when path does not match' do
+        request.path = '/alternative-path'
+        expect(controller.signed_request_account).to be_nil
+      end
+
+      it 'returns nil when method does not match' do
+        post :success
+        expect(controller.signed_request_account).to be_nil
+      end
+    end
+  end
+end