Update BulkImports UploadsPipeline to filter & ignore file symlinks

app/services/bulk_imports/archive_extraction_service.rb

+# frozen_string_literal: true
+
+# Archive Extraction Service allows extraction of contents
+# from `tar` archives with an additional handling (removal)
+# of file symlinks.
+#
+# @param tmpdir [String] A path where archive is located
+# and where its contents are extracted.
+# Tmpdir directory must be located under `Dir.tmpdir`.
+# `BulkImports::Error` is raised if any other directory path is used.
+#
+# @param filename [String] Name of the file to extract contents from.
+#
+# @example
+#   dir = Dir.mktmpdir
+#   filename = 'things.tar'
+#   BulkImports::ArchiveExtractionService.new(tmpdir: dir, filename: filename).execute
+#   Dir.glob(File.join(dir, '**', '*'))
+#   => ['/path/to/tmp/dir/extracted_file_1', '/path/to/tmp/dir/extracted_file_2', '/path/to/tmp/dir/extracted_file_3']
+module BulkImports
+  class ArchiveExtractionService
+    include Gitlab::ImportExport::CommandLineUtil
+
+    def initialize(tmpdir:, filename:)
+      @tmpdir = tmpdir
+      @filename = filename
+      @filepath = File.join(@tmpdir, @filename)
+    end
+
+    def execute
+      validate_filepath
+      validate_tmpdir
+      validate_symlink
+
+      extract_archive
+      remove_symlinks
+      tmpdir
+    end
+
+    private
+
+    attr_reader :tmpdir, :filename, :filepath
+
+    def validate_filepath
+      Gitlab::Utils.check_path_traversal!(filepath)
+    end
+
+    def validate_tmpdir
+      raise(BulkImports::Error, 'Invalid target directory') unless File.expand_path(tmpdir).start_with?(Dir.tmpdir)
+    end
+
+    def validate_symlink
+      raise(BulkImports::Error, 'Invalid file') if symlink?(filepath)
+    end
+
+    def symlink?(filepath)
+      File.lstat(filepath).symlink?
+    end
+
+    def extract_archive
+      untar_xf(archive: filepath, dir: tmpdir)
+    end
+
+    def extracted_files
+      Dir.glob(File.join(tmpdir, '**', '*'))
+    end
+
+    def remove_symlinks
+      extracted_files.each do |path|
+        FileUtils.rm(path) if symlink?(path)
+      end
+    end
+  end
+end

lib/bulk_imports/common/pipelines/uploads_pipeline.rb

@@ -5,16 +5,16 @@ module BulkImports
     module Pipelines
       class UploadsPipeline
         include Pipeline
-        include Gitlab::ImportExport::CommandLineUtil
 
-        FILENAME = 'uploads.tar.gz'
         AVATAR_PATTERN = %r{.*\/#{BulkImports::UploadsExportService::AVATAR_PATH}\/(?<identifier>.*)}.freeze
 
         AvatarLoadingError = Class.new(StandardError)
 
-        def extract(context)
-          download_service(tmp_dir, context).execute
-          untar_zxf(archive: File.join(tmp_dir, FILENAME), dir: tmp_dir)
+        def extract(_context)
+          download_service.execute
+          decompression_service.execute
+          extraction_service.execute
+
           upload_file_paths = Dir.glob(File.join(tmp_dir, '**', '*'))
 
           BulkImports::Pipeline::ExtractedData.new(data: upload_file_paths)
@@ -29,6 +29,7 @@ module BulkImports
 
           return unless dynamic_path
           return if File.directory?(file_path)
+          return if File.lstat(file_path).symlink?
 
           named_captures = dynamic_path.named_captures.symbolize_keys
 
@@ -36,20 +37,40 @@ module BulkImports
         end
 
         def after_run(_)
-          FileUtils.remove_entry(tmp_dir)
+          FileUtils.remove_entry(tmp_dir) if Dir.exist?(tmp_dir)
         end
 
         private
 
-        def download_service(tmp_dir, context)
+        def download_service
           BulkImports::FileDownloadService.new(
             configuration: context.configuration,
-            relative_url: context.entity.relation_download_url_path('uploads'),
+            relative_url: context.entity.relation_download_url_path(relation),
             dir: tmp_dir,
-            filename: FILENAME
+            filename: targz_filename
           )
         end
 
+        def decompression_service
+          BulkImports::FileDecompressionService.new(dir: tmp_dir, filename: targz_filename)
+        end
+
+        def extraction_service
+          BulkImports::ArchiveExtractionService.new(tmpdir: tmp_dir, filename: tar_filename)
+        end
+
+        def relation
+          BulkImports::FileTransfer::BaseConfig::UPLOADS_RELATION
+        end
+
+        def tar_filename
+          "#{relation}.tar"
+        end
+
+        def targz_filename
+          "#{tar_filename}.gz"
+        end
+
         def tmp_dir
           @tmp_dir ||= Dir.mktmpdir('bulk_imports')
         end

lib/gitlab/import_export/command_line_util.rb

@@ -18,6 +18,10 @@ module Gitlab
         tar_with_options(archive: archive, dir: dir, options: 'cf')
       end
 
+      def untar_xf(archive:, dir:)
+        untar_with_options(archive: archive, dir: dir, options: 'xf')
+      end
+
       def gzip(dir:, filename:)
         gzip_with_options(dir: dir, filename: filename)
       end

spec/initializers/action_cable_subscription_adapter_identifier_spec.rb

@@ -4,6 +4,12 @@ require 'spec_helper'
 
 RSpec.describe 'ActionCableSubscriptionAdapterIdentifier override' do
   describe '#identifier' do
+    let!(:original_config) { ::ActionCable::Server::Base.config.cable }
+
+    after do
+      ::ActionCable::Server::Base.config.cable = original_config
+    end
+
     context 'when id key is nil on cable.yml' do
       it 'does not override server config id with action cable pid' do
         config = {

spec/lib/bulk_imports/common/pipelines/uploads_pipeline_spec.rb

@@ -70,8 +70,10 @@ RSpec.describe BulkImports::Common::Pipelines::UploadsPipeline do
     describe '#extract' do
       it 'downloads & extracts upload paths' do
         allow(Dir).to receive(:mktmpdir).and_return(tmpdir)
-        expect(pipeline).to receive(:untar_zxf)
-        file_download_service = instance_double("BulkImports::FileDownloadService")
+
+        download_service = instance_double("BulkImports::FileDownloadService")
+        decompression_service = instance_double("BulkImports::FileDecompressionService")
+        extraction_service = instance_double("BulkImports::ArchiveExtractionService")
 
         expect(BulkImports::FileDownloadService)
           .to receive(:new)
@@ -80,9 +82,13 @@ RSpec.describe BulkImports::Common::Pipelines::UploadsPipeline do
             relative_url: "/#{entity.pluralized_name}/test/export_relations/download?relation=uploads",
             dir: tmpdir,
             filename: 'uploads.tar.gz')
-          .and_return(file_download_service)
+          .and_return(download_service)
+        expect(BulkImports::FileDecompressionService).to receive(:new).with(dir: tmpdir, filename: 'uploads.tar.gz').and_return(decompression_service)
+        expect(BulkImports::ArchiveExtractionService).to receive(:new).with(tmpdir: tmpdir, filename: 'uploads.tar').and_return(extraction_service)
 
-        expect(file_download_service).to receive(:execute)
+        expect(download_service).to receive(:execute)
+        expect(decompression_service).to receive(:execute)
+        expect(extraction_service).to receive(:execute)
 
         extracted_data = pipeline.extract(context)
 
@@ -106,6 +112,16 @@ RSpec.describe BulkImports::Common::Pipelines::UploadsPipeline do
           expect { pipeline.load(context, uploads_dir_path) }.not_to change { portable.uploads.count }
         end
       end
+
+      context 'when path is a symlink' do
+        it 'does not upload the file' do
+          symlink = File.join(tmpdir, 'symlink')
+
+          FileUtils.ln_s(File.join(tmpdir, upload_file_path), symlink)
+
+          expect { pipeline.load(context, symlink) }.not_to change { portable.uploads.count }
+        end
+      end
     end
   end
 

spec/lib/gitlab/import_export/command_line_util_spec.rb

@@ -101,4 +101,39 @@ RSpec.describe Gitlab::ImportExport::CommandLineUtil do
       end
     end
   end
+
+  describe '#untar_xf' do
+    let(:archive_dir) { Dir.mktmpdir }
+
+    after do
+      FileUtils.remove_entry(archive_dir)
+    end
+
+    it 'extracts archive without decompression' do
+      filename = 'archive.tar.gz'
+      archive_file = File.join(archive_dir, 'archive.tar')
+
+      FileUtils.copy_file(archive, File.join(archive_dir, filename))
+      subject.gunzip(dir: archive_dir, filename: filename)
+
+      result = subject.untar_xf(archive: archive_file, dir: archive_dir)
+
+      expect(result).to eq(true)
+      expect(File.exist?(archive_file)).to eq(true)
+      expect(File.exist?(File.join(archive_dir, 'project.json'))).to eq(true)
+      expect(Dir.exist?(File.join(archive_dir, 'uploads'))).to eq(true)
+    end
+
+    context 'when something goes wrong' do
+      it 'raises an error' do
+        expect(Gitlab::Popen).to receive(:popen).and_return(['Error', 1])
+
+        klass = Class.new do
+          include Gitlab::ImportExport::CommandLineUtil
+        end.new
+
+        expect { klass.untar_xf(archive: 'test', dir: 'test') }.to raise_error(Gitlab::ImportExport::Error, 'System call failed')
+      end
+    end
+  end
 end

spec/services/bulk_imports/archive_extraction_service_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe BulkImports::ArchiveExtractionService do
+  let_it_be(:tmpdir) { Dir.mktmpdir }
+  let_it_be(:filename) { 'symlink_export.tar' }
+  let_it_be(:filepath) { File.join(tmpdir, filename) }
+
+  before do
+    FileUtils.copy_file(File.join('spec', 'fixtures', filename), filepath)
+  end
+
+  after(:all) do
+    FileUtils.remove_entry(tmpdir)
+  end
+
+  subject(:service) { described_class.new(tmpdir: tmpdir, filename: filename) }
+
+  describe '#execute' do
+    it 'extracts files from archive and removes symlinks' do
+      file = File.join(tmpdir, 'project.json')
+      folder = File.join(tmpdir, 'uploads')
+      symlink = File.join(tmpdir, 'uploads', 'link.gitignore')
+
+      expect(service).to receive(:untar_xf).with(archive: filepath, dir: tmpdir).and_call_original
+
+      service.execute
+
+      expect(File.exist?(file)).to eq(true)
+      expect(Dir.exist?(folder)).to eq(true)
+      expect(File.exist?(symlink)).to eq(false)
+    end
+
+    context 'when dir is not in tmpdir' do
+      it 'raises an error' do
+        ['/etc', '/usr', '/', '/home', '', '/some/other/path', Rails.root].each do |path|
+          expect { described_class.new(tmpdir: path, filename: 'filename').execute }
+            .to raise_error(BulkImports::Error, 'Invalid target directory')
+        end
+      end
+    end
+
+    context 'when archive file is a symlink' do
+      it 'raises an error' do
+        FileUtils.ln_s(File.join(tmpdir, filename), File.join(tmpdir, 'symlink'))
+
+        expect { described_class.new(tmpdir: tmpdir, filename: 'symlink').execute }
+          .to raise_error(BulkImports::Error, 'Invalid file')
+      end
+    end
+
+    context 'when filepath is being traversed' do
+      it 'raises an error' do
+        expect { described_class.new(tmpdir: File.join(tmpdir, '../../../'), filename: 'name').execute }
+          .to raise_error(Gitlab::Utils::PathTraversalAttackError, 'Invalid path')
+      end
+    end
+  end
+end