create own sign-logic for SignedRetraction and RelayableRetraction

this is a small code-duplication, but will be removed when
SignedRetraction and RelayableRetraction will be removed.

lib/diaspora_federation/entities/relayable_retraction.rb

@@ -78,6 +78,12 @@ module DiasporaFederation
         end
       end
 
+      # use only {Retraction} for receive
+      # @return [Retraction] instance as normal retraction
+      def to_retraction
+        Retraction.new(diaspora_id: diaspora_id, target_guid: target_guid, target_type: target_type)
+      end
+
       private
 
       # @param [String] target_author the author of the entity to retract
@@ -85,11 +91,9 @@ module DiasporaFederation
       # @param [Hash] hash hash given for a signing
       def fill_required_signature(target_author, privkey, hash)
         if target_author == diaspora_id && target_author_signature.nil?
-          hash[:target_author_signature] =
-            Signing.sign_with_key(SignedRetraction.apply_signable_exceptions(hash), privkey)
+          hash[:target_author_signature] = SignedRetraction.sign_with_key(privkey, self)
         elsif target_author != diaspora_id && parent_author_signature.nil?
-          hash[:parent_author_signature] =
-            Signing.sign_with_key(SignedRetraction.apply_signable_exceptions(hash), privkey)
+          hash[:parent_author_signature] = SignedRetraction.sign_with_key(privkey, self)
         end
       end
     end

lib/diaspora_federation/entities/signed_retraction.rb

@@ -48,21 +48,23 @@ module DiasporaFederation
         super.tap do |hash|
           if target_author_signature.nil?
             privkey = DiasporaFederation.callbacks.trigger(:fetch_private_key_by_diaspora_id, diaspora_id)
-            unless privkey.nil?
-              hash[:target_author_signature] =
-                Signing.sign_with_key(SignedRetraction.apply_signable_exceptions(hash), privkey)
-            end
+            hash[:target_author_signature] = SignedRetraction.sign_with_key(privkey, self) unless privkey.nil?
           end
         end
       end
 
-      # Deletes :diaspora_id (xml_name: sender_handle) from the hash in order to compute
-      # a signature since it is included from signable_string for SignedRetraction and RelayableRetraction
-      #
-      # @param [Hash] data hash of the retraction properties
-      # @return [Hash] hash copy without :diaspora_id member
-      def self.apply_signable_exceptions(data)
-        data.dup.tap {|data| data.delete(:diaspora_id) }
+      # use only {Retraction} for receive
+      # @return [Retraction] instance as normal retraction
+      def to_retraction
+        Retraction.new(diaspora_id: diaspora_id, target_guid: target_guid, target_type: target_type)
+      end
+
+      # Create signature for a retraction
+      # @param [OpenSSL::PKey::RSA] privkey private key of sender
+      # @param [SignedRetraction, RelayableRetraction] ret the retraction to sign
+      # @return [String] a Base64 encoded signature of the retraction with the key
+      def self.sign_with_key(privkey, ret)
+        Base64.strict_encode64(privkey.sign(OpenSSL::Digest::SHA256.new, [ret.target_guid, ret.target_type].join(";")))
       end
     end
   end

spec/lib/diaspora_federation/entities/relayable_retraction_spec.rb

@@ -75,5 +75,17 @@ XML
         expect(signed_hash[:target_author_signature]).to eq(nil)
       end
     end
+
+    describe "#to_retraction" do
+      it "copies the attributes to a Retraction" do
+        relayable_retraction = FactoryGirl.build(:relayable_retraction_entity)
+        retraction = relayable_retraction.to_retraction
+
+        expect(retraction).to be_a(Entities::Retraction)
+        expect(retraction.diaspora_id).to eq(relayable_retraction.diaspora_id)
+        expect(retraction.target_guid).to eq(relayable_retraction.target_guid)
+        expect(retraction.target_type).to eq(relayable_retraction.target_type)
+      end
+    end
   end
 end

spec/lib/diaspora_federation/entities/signed_retraction_spec.rb

@@ -50,5 +50,17 @@ XML
         expect(signed_hash[:author_signature]).to eq(nil)
       end
     end
+
+    describe "#to_retraction" do
+      it "copies the attributes to a Retraction" do
+        signed_retraction = FactoryGirl.build(:signed_retraction_entity)
+        retraction = signed_retraction.to_retraction
+
+        expect(retraction).to be_a(Entities::Retraction)
+        expect(retraction.diaspora_id).to eq(signed_retraction.diaspora_id)
+        expect(retraction.target_guid).to eq(signed_retraction.target_guid)
+        expect(retraction.target_type).to eq(signed_retraction.target_type)
+      end
+    end
   end
 end