Enforce the fork_project permission in Projects::CreateService

Projects::ForkService delegates to this service almost entirely, but needed
one small change so it would propagate create errors correctly.

CreateService#execute needs significant refactoring; it is now right at the
complexity limit set by Rubocop. I avoided doing so in this commit to keep the
diff as small as possible.

Several tests depend on the insecure behaviour of ForkService, so fi them up at
the same time.

2 files changed, 14 insertions, 0 deletions

diff --git a/app/services/projects/create_service.rb b/app/services/projects/create_service.rb
index be749ba4a1c..696fe3efe8f 100644
--- a/app/services/projects/create_service.rb
+++ b/app/services/projects/create_service.rb
@@ -15,6 +15,11 @@ module Projects
         return @project
       end
 
+      unless allowed_fork?(forked_from_project_id)
+        @project.errors.add(:forked_from_project_id, 'is forbidden')
+        return @project
+      end
+
       # Set project name from path
       if @project.name.present? && @project.path.present?
         # if both name and path set - everything is ok
@@ -71,6 +76,13 @@ module Projects
       @project.errors.add(:namespace, "is not valid")
     end
 
+    def allowed_fork?(source_project_id)
+      return true if source_project_id.nil?
+
+      source_project = Project.find_by(id: source_project_id)
+      current_user.can?(:fork_project, source_project)
+    end
+
     def allowed_namespace?(user, namespace_id)
       namespace = Namespace.find_by(id: namespace_id)
       current_user.can?(:create_projects, namespace)
diff --git a/app/services/projects/fork_service.rb b/app/services/projects/fork_service.rb
index a2de4dccece..a2b23ea6171 100644
--- a/app/services/projects/fork_service.rb
+++ b/app/services/projects/fork_service.rb
@@ -16,6 +16,8 @@ module Projects
       end
 
       new_project = CreateService.new(current_user, new_params).execute
+      return new_project unless new_project.persisted?
+
       builds_access_level = @project.project_feature.builds_access_level
       new_project.project_feature.update_attributes(builds_access_level: builds_access_level)