Add decompressed archive size validation

- Validate Project/Group Import incoming compressed
  archive to make sure decompressed size is within
  acceptabe range

changelogs/unreleased/security-fix-import-decompr-issue.yml

+---
+title: Add decompressed archive size validation on Project/Group Import
+merge_request: 562
+author:
+type: security

doc/security/project_import_decompressed_archive_size_limits.md

+---
+type: reference, howto
+---
+
+# Project Import Decompressed Archive Size Limits
+
+> [Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/31564) in GitLab 13.2.
+
+When using [Project Import](../user/project/settings/import_export.md), the size of the decompressed project archive is limited to 10Gb.
+
+If decompressed size exceeds this limit, `Decompressed archive size validation failed` error is returned.
+
+## Enable/disable size validation
+
+Decompressed size validation is enabled by default.
+If you have a project with decompressed size exceeding this limit,
+it is possible to disable the validation by turning off the
+`validate_import_decompressed_archive_size` feature flag.
+
+Start a [Rails console](../administration/troubleshooting/debug.md#starting-a-rails-console-session).
+
+```ruby
+# Disable
+Feature.disable(:validate_import_decompressed_archive_size)
+
+# Enable
+Feature.enable(:validate_import_decompressed_archive_size)
+```

lib/gitlab/import_export/decompressed_archive_size_validator.rb

+# frozen_string_literal: true
+
+require 'zlib'
+
+module Gitlab
+  module ImportExport
+    class DecompressedArchiveSizeValidator
+      include Gitlab::Utils::StrongMemoize
+
+      DEFAULT_MAX_BYTES = 10.gigabytes.freeze
+      CHUNK_SIZE = 4096.freeze
+
+      attr_reader :error
+
+      def initialize(archive_path:, max_bytes: self.class.max_bytes)
+        @archive_path = archive_path
+        @max_bytes = max_bytes
+        @bytes_read = 0
+        @total_reads = 0
+        @denominator = 5
+        @error = nil
+      end
+
+      def valid?
+        strong_memoize(:valid) do
+          validate
+        end
+      end
+
+      def self.max_bytes
+        DEFAULT_MAX_BYTES
+      end
+
+      def archive_file
+        @archive_file ||= File.open(@archive_path)
+      end
+
+      private
+
+      def validate
+        until archive_file.eof?
+          compressed_chunk = archive_file.read(CHUNK_SIZE)
+
+          inflate_stream.inflate(compressed_chunk) do |chunk|
+            @bytes_read += chunk.size
+            @total_reads += 1
+          end
+
+          # Start garbage collection every 5 reads in order
+          # to prevent memory bloat during archive decompression
+          GC.start if gc_start?
+
+          if @bytes_read > @max_bytes
+            @error = error_message
+
+            return false
+          end
+        end
+
+        true
+      rescue => e
+        @error = error_message
+
+        Gitlab::ErrorTracking.track_exception(e)
+
+        Gitlab::Import::Logger.info(
+          message: @error,
+          error: e.message
+        )
+
+        false
+      ensure
+        inflate_stream.close
+        archive_file.close
+      end
+
+      def inflate_stream
+        @inflate_stream ||= Zlib::Inflate.new(Zlib::MAX_WBITS + 32)
+      end
+
+      def gc_start?
+        @total_reads % @denominator == 0
+      end
+
+      def error_message
+        _('Decompressed archive size validation failed.')
+      end
+    end
+  end
+end

lib/gitlab/import_export/file_importer.rb

@@ -28,6 +28,7 @@ module Gitlab
         copy_archive
 
         wait_for_archived_file do
+          validate_decompressed_archive_size if Feature.enabled?(:validate_import_decompressed_archive_size, default_enabled: true)
           decompress_archive
         end
       rescue => e
@@ -82,6 +83,14 @@ module Gitlab
       def extracted_files
         Dir.glob("#{@shared.export_path}/**/*", File::FNM_DOTMATCH).reject { |f| IGNORED_FILENAMES.include?(File.basename(f)) }
       end
+
+      def validate_decompressed_archive_size
+        raise ImporterError.new(size_validator.error) unless size_validator.valid?
+      end
+
+      def size_validator
+        @size_validator ||= DecompressedArchiveSizeValidator.new(archive_path: @archive_file)
+      end
     end
   end
 end

locale/gitlab.pot

@@ -7270,6 +7270,9 @@ msgstr ""
 msgid "Decline and sign out"
 msgstr ""
 
+msgid "Decompressed archive size validation failed."
+msgstr ""
+
 msgid "Default Branch"
 msgstr ""
 

spec/lib/gitlab/import_export/decompressed_archive_size_validator_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe Gitlab::ImportExport::DecompressedArchiveSizeValidator do
+  let_it_be(:filepath) { File.join(Dir.tmpdir, 'decompressed_archive_size_validator_spec.gz') }
+
+  before(:all) do
+    create_compressed_file
+  end
+
+  after(:all) do
+    FileUtils.rm(filepath)
+  end
+
+  subject { described_class.new(archive_path: filepath, max_bytes: max_bytes) }
+
+  describe '#valid?' do
+    let(:max_bytes) { 1 }
+
+    context 'when file does not exceed allowed decompressed size' do
+      let(:max_bytes) { 20 }
+
+      it 'returns true' do
+        expect(subject.valid?).to eq(true)
+      end
+    end
+
+    context 'when file exceeds allowed decompressed size' do
+      it 'returns false' do
+        expect(subject.valid?).to eq(false)
+      end
+    end
+
+    context 'when something goes wrong during decompression' do
+      before do
+        allow(subject.archive_file).to receive(:eof?).and_raise(StandardError)
+      end
+
+      it 'logs and tracks raised exception' do
+        expect(Gitlab::ErrorTracking).to receive(:track_exception).with(instance_of(StandardError))
+        expect(Gitlab::Import::Logger).to receive(:info).with(hash_including(message: 'Decompressed archive size validation failed.'))
+
+        subject.valid?
+      end
+
+      it 'returns false' do
+        expect(subject.valid?).to eq(false)
+      end
+    end
+  end
+
+  def create_compressed_file
+    Zlib::GzipWriter.open(filepath) do |gz|
+      gz.write('Hello World!')
+    end
+  end
+end

spec/lib/gitlab/import_export/file_importer_spec.rb

@@ -98,6 +98,45 @@ RSpec.describe Gitlab::ImportExport::FileImporter do
     end
   end
 
+  context 'when file exceeds acceptable decompressed size' do
+    let(:project) { create(:project) }
+    let(:shared) { Gitlab::ImportExport::Shared.new(project) }
+    let(:filepath) { File.join(Dir.tmpdir, 'file_importer_spec.gz') }
+
+    subject { described_class.new(importable: project, archive_file: filepath, shared: shared) }
+
+    before do
+      Zlib::GzipWriter.open(filepath) do |gz|
+        gz.write('Hello World!')
+      end
+    end
+
+    context 'when validate_import_decompressed_archive_size feature flag is enabled' do
+      before do
+        stub_feature_flags(validate_import_decompressed_archive_size: true)
+
+        allow(Gitlab::ImportExport::DecompressedArchiveSizeValidator).to receive(:max_bytes).and_return(1)
+      end
+
+      it 'returns false' do
+        expect(subject.import).to eq(false)
+        expect(shared.errors.join).to eq('Decompressed archive size validation failed.')
+      end
+    end
+
+    context 'when validate_import_decompressed_archive_size feature flag is disabled' do
+      before do
+        stub_feature_flags(validate_import_decompressed_archive_size: false)
+      end
+
+      it 'skips validation' do
+        expect(subject).to receive(:validate_decompressed_archive_size).never
+
+        subject.import
+      end
+    end
+  end
+
   def setup_files
     FileUtils.mkdir_p("#{shared.export_path}/subfolder/")
     FileUtils.touch(valid_file)