Enforce file size limits for direct uploads on S3 [SCI-3681]

app/controllers/users/registrations_controller.rb

@@ -31,7 +31,7 @@ class Users::RegistrationsController < Devise::RegistrationsController
       end
     elsif params.include? :change_avatar
       params.delete(:change_avatar)
-      if !params.include?(:avatar)
+      if !params.include?(:avatar) || (params[:avatar].length > Constants::AVATAR_MAX_SIZE_MB.megabytes * 2)
         resource.errors.add(:avatar, :blank)
         false
       else

app/services/active_storage/service/custom_s3_service.rb

@@ -113,6 +113,8 @@ module ActiveStorage
     end
 
     def url_for_direct_upload(key, expires_in:, content_type:, content_length:, checksum:)
+      raise ActiveStorage::IntegrityError if content_length > Rails.configuration.x.file_max_size_mb.megabytes
+
       instrument :url, key: key do |payload|
         generated_url = object_for(key).presigned_url :put, expires_in: expires_in.to_i,
           content_type: content_type, content_length: content_length, content_md5: checksum
@@ -169,4 +171,16 @@ module ActiveStorage
       end
     end
   end
+
+  module S3SignerModifier
+    def build_signer(cfg)
+      signer = super(cfg)
+      signer.unsigned_headers.delete('content-length')
+      signer
+    end
+  end
+
+  Aws::S3::Presigner.class_eval do
+    prepend S3SignerModifier
+  end
 end