Skip LFS fragment on redirect

Fixes issue #335495 : LFS download service not skipping body fragment on redirect

Changelog: fixed
MR: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/65751

app/services/projects/lfs_pointers/lfs_download_service.rb

@@ -61,8 +61,10 @@ module Projects
       def download_and_save_file!(file)
         digester = Digest::SHA256.new
         fetch_file do |fragment|
-          digester << fragment
-          file.write(fragment)
+          if digest_fragment?(fragment)
+            digester << fragment
+            file.write(fragment)
+          end
 
           raise_size_error! if file.size > lfs_size
         end
@@ -71,6 +73,10 @@ module Projects
         raise_oid_error! if digester.hexdigest != lfs_oid
       end
 
+      def digest_fragment?(fragment)
+        fragment.http_response.is_a?(Net::HTTPSuccess)
+      end
+
       def download_options
         http_options = { headers: lfs_headers, stream_body: true }
 

spec/services/projects/lfs_pointers/lfs_download_service_spec.rb

@@ -106,6 +106,26 @@ RSpec.describe Projects::LfsPointers::LfsDownloadService do
       end
     end
 
+    context 'when file download returns a redirect' do
+      let(:redirect_link) { 'http://external-link' }
+
+      before do
+        stub_full_request(download_link).to_return(status: 301, body: 'You are being redirected', headers: { 'Location' => redirect_link } )
+        stub_full_request(redirect_link).to_return(body: lfs_content)
+      end
+
+      it_behaves_like 'lfs object is created'
+
+      it 'correctly stores lfs object' do
+        subject.execute
+
+        new_lfs_object = LfsObject.first
+
+        expect(new_lfs_object).to have_attributes(oid: oid, size: size)
+        expect(File.binread(new_lfs_object.file.file.file)).to eq lfs_content
+      end
+    end
+
     context 'when downloaded lfs file has a different size' do
       let(:size) { 1 }