Add latest changes from gitlab-org/security/gitlab@16-1-stable-ee

34 files changed, 591 insertions, 142 deletions

diff --git a/app/services/bulk_imports/archive_extraction_service.rb b/app/services/bulk_imports/archive_extraction_service.rb
index 4485b19035b..bce2a67218a 100644
--- a/app/services/bulk_imports/archive_extraction_service.rb
+++ b/app/services/bulk_imports/archive_extraction_service.rb
@@ -49,11 +49,7 @@ module BulkImports
     end
 
     def validate_symlink
-      raise(BulkImports::Error, 'Invalid file') if symlink?(filepath)
-    end
-
-    def symlink?(filepath)
-      File.lstat(filepath).symlink?
+      raise(BulkImports::Error, 'Invalid file') if Gitlab::Utils::FileInfo.linked?(filepath)
     end
 
     def extract_archive
diff --git a/app/services/bulk_imports/file_decompression_service.rb b/app/services/bulk_imports/file_decompression_service.rb
index 94573f6bb13..77638f10f54 100644
--- a/app/services/bulk_imports/file_decompression_service.rb
+++ b/app/services/bulk_imports/file_decompression_service.rb
@@ -53,7 +53,7 @@ module BulkImports
     end
 
     def validate_symlink(filepath)
-      raise(ServiceError, 'Invalid file') if File.lstat(filepath).symlink?
+      raise(ServiceError, 'Invalid file') if Gitlab::Utils::FileInfo.linked?(filepath)
     end
 
     def decompress_file
diff --git a/config/application.rb b/config/application.rb
index 7eeb75a73cd..757d62c72ad 100644
--- a/config/application.rb
+++ b/config/application.rb
@@ -172,6 +172,7 @@ module Gitlab
     # - Any parameter containing `password`
     # - Any parameter containing `secret`
     # - Any parameter ending with `key`
+    # - Any parameter named `redirect`, filtered for security concerns of exposing sensitive information
     # - Two-factor tokens (:otp_attempt)
     # - Repo/Project Import URLs (:import_url)
     # - Build traces (:trace)
@@ -214,6 +215,7 @@ module Gitlab
       variables
       content
       sharedSecret
+      redirect
     )
 
     # Enable escaping HTML in JSON.
diff --git a/lib/banzai/filter/plantuml_filter.rb b/lib/banzai/filter/plantuml_filter.rb
index 2e5f1b29c52..7e6535b86fd 100644
--- a/lib/banzai/filter/plantuml_filter.rb
+++ b/lib/banzai/filter/plantuml_filter.rb
@@ -11,7 +11,7 @@ module Banzai
       def call
         return doc unless settings.plantuml_enabled? && doc.at_xpath(lang_tag)
 
-        plantuml_setup
+        Gitlab::Plantuml.configure
 
         doc.xpath(lang_tag).each do |node|
           img_tag = Nokogiri::HTML::DocumentFragment.parse(
@@ -38,15 +38,6 @@ module Banzai
       def settings
         Gitlab::CurrentSettings.current_application_settings
       end
-
-      def plantuml_setup
-        Asciidoctor::PlantUml.configure do |conf|
-          conf.url = settings.plantuml_url
-          conf.png_enable = settings.plantuml_enabled
-          conf.svg_enable = false
-          conf.txt_enable = false
-        end
-      end
     end
   end
 end
diff --git a/lib/bulk_imports/common/pipelines/lfs_objects_pipeline.rb b/lib/bulk_imports/common/pipelines/lfs_objects_pipeline.rb
index 68bd64dc2ff..9a22d211ba1 100644
--- a/lib/bulk_imports/common/pipelines/lfs_objects_pipeline.rb
+++ b/lib/bulk_imports/common/pipelines/lfs_objects_pipeline.rb
@@ -24,7 +24,7 @@ module BulkImports
           return if tar_filepath?(file_path)
           return if lfs_json_filepath?(file_path)
           return if File.directory?(file_path)
-          return if File.lstat(file_path).symlink?
+          return if Gitlab::Utils::FileInfo.linked?(file_path)
 
           size = File.size(file_path)
           oid = LfsObject.calculate_oid(file_path)
diff --git a/lib/bulk_imports/common/pipelines/uploads_pipeline.rb b/lib/bulk_imports/common/pipelines/uploads_pipeline.rb
index 06132791ea6..b1eeccf96f7 100644
--- a/lib/bulk_imports/common/pipelines/uploads_pipeline.rb
+++ b/lib/bulk_imports/common/pipelines/uploads_pipeline.rb
@@ -24,7 +24,7 @@ module BulkImports
           # Validate that the path is OK to load
           Gitlab::PathTraversal.check_allowed_absolute_path_and_path_traversal!(file_path, [Dir.tmpdir])
           return if File.directory?(file_path)
-          return if File.lstat(file_path).symlink?
+          return if Gitlab::Utils::FileInfo.linked?(file_path)
 
           avatar_path = AVATAR_PATTERN.match(file_path)
           return save_avatar(file_path) if avatar_path
diff --git a/lib/bulk_imports/file_downloads/validations.rb b/lib/bulk_imports/file_downloads/validations.rb
index b852a50c888..e1844843408 100644
--- a/lib/bulk_imports/file_downloads/validations.rb
+++ b/lib/bulk_imports/file_downloads/validations.rb
@@ -32,7 +32,7 @@ module BulkImports
       end
 
       def validate_symlink
-        return unless File.lstat(filepath).symlink?
+        return unless Gitlab::Utils::FileInfo.linked?(filepath)
 
         File.delete(filepath)
         raise_error 'Invalid downloaded file'
diff --git a/lib/bulk_imports/projects/pipelines/design_bundle_pipeline.rb b/lib/bulk_imports/projects/pipelines/design_bundle_pipeline.rb
index 373cd2bd75a..235d2629b9e 100644
--- a/lib/bulk_imports/projects/pipelines/design_bundle_pipeline.rb
+++ b/lib/bulk_imports/projects/pipelines/design_bundle_pipeline.rb
@@ -26,7 +26,7 @@ module BulkImports
           return unless portable.lfs_enabled?
           return unless File.exist?(bundle_path)
           return if File.directory?(bundle_path)
-          return if File.lstat(bundle_path).symlink?
+          return if Gitlab::Utils::FileInfo.linked?(bundle_path)
 
           portable.design_repository.create_from_bundle(bundle_path)
         end
diff --git a/lib/bulk_imports/projects/pipelines/repository_bundle_pipeline.rb b/lib/bulk_imports/projects/pipelines/repository_bundle_pipeline.rb
index f19d8931f4a..4307cb2bafd 100644
--- a/lib/bulk_imports/projects/pipelines/repository_bundle_pipeline.rb
+++ b/lib/bulk_imports/projects/pipelines/repository_bundle_pipeline.rb
@@ -26,7 +26,7 @@ module BulkImports
 
           return unless File.exist?(bundle_path)
           return if File.directory?(bundle_path)
-          return if File.lstat(bundle_path).symlink?
+          return if Gitlab::Utils::FileInfo.linked?(bundle_path)
 
           portable.repository.create_from_bundle(bundle_path)
         end
diff --git a/lib/gitlab/asciidoc.rb b/lib/gitlab/asciidoc.rb
index 955cb14594f..31e8dcd84b7 100644
--- a/lib/gitlab/asciidoc.rb
+++ b/lib/gitlab/asciidoc.rb
@@ -78,20 +78,11 @@ module Gitlab
       context[:pipeline] = :ascii_doc
       context[:max_includes] = [MAX_INCLUDES, context[:max_includes]].compact.min
 
-      plantuml_setup
+      Gitlab::Plantuml.configure
 
       html = ::Asciidoctor.convert(input, asciidoc_opts)
       html = Banzai.render(html, context)
       html.html_safe
     end
-
-    def self.plantuml_setup
-      Asciidoctor::PlantUml.configure do |conf|
-        conf.url = Gitlab::CurrentSettings.plantuml_url
-        conf.svg_enable = Gitlab::CurrentSettings.plantuml_enabled
-        conf.png_enable = Gitlab::CurrentSettings.plantuml_enabled
-        conf.txt_enable = false
-      end
-    end
   end
 end
diff --git a/lib/gitlab/ci/decompressed_gzip_size_validator.rb b/lib/gitlab/ci/decompressed_gzip_size_validator.rb
index 9b7b5f0dd66..b386e400423 100644
--- a/lib/gitlab/ci/decompressed_gzip_size_validator.rb
+++ b/lib/gitlab/ci/decompressed_gzip_size_validator.rb
@@ -65,7 +65,7 @@ module Gitlab
       def validate_archive_path
         Gitlab::PathTraversal.check_path_traversal!(archive_path)
 
-        raise(ServiceError, 'Archive path is a symlink') if File.lstat(archive_path).symlink?
+        raise(ServiceError, 'Archive path is a symlink or hard link') if Gitlab::Utils::FileInfo.linked?(archive_path)
         raise(ServiceError, 'Archive path is not a file') unless File.file?(archive_path)
       end
 
diff --git a/lib/gitlab/import_export/command_line_util.rb b/lib/gitlab/import_export/command_line_util.rb
index d681f39f00b..e2f365fcbf8 100644
--- a/lib/gitlab/import_export/command_line_util.rb
+++ b/lib/gitlab/import_export/command_line_util.rb
@@ -5,8 +5,11 @@ module Gitlab
     module CommandLineUtil
       UNTAR_MASK = 'u+rwX,go+rX,go-w'
       DEFAULT_DIR_MODE = 0700
+      CLEAN_DIR_IGNORE_FILE_NAMES = %w[. ..].freeze
 
-      FileOversizedError = Class.new(StandardError)
+      CommandLineUtilError = Class.new(StandardError)
+      FileOversizedError = Class.new(CommandLineUtilError)
+      HardLinkError = Class.new(CommandLineUtilError)
 
       def tar_czf(archive:, dir:)
         tar_with_options(archive: archive, dir: dir, options: 'czf')
@@ -90,7 +93,7 @@ module Gitlab
       def untar_with_options(archive:, dir:, options:)
         execute_cmd(%W(tar -#{options} #{archive} -C #{dir}))
         execute_cmd(%W(chmod -R #{UNTAR_MASK} #{dir}))
-        remove_symlinks(dir)
+        clean_extraction_dir!(dir)
       end
 
       # rubocop:disable Gitlab/ModuleWithInstanceVariables
@@ -122,17 +125,27 @@ module Gitlab
         true
       end
 
-      def remove_symlinks(dir)
-        ignore_file_names = %w[. ..]
-
+      # Scans and cleans the directory tree.
+      # Symlinks are considered legal but are removed.
+      # Files sharing hard links are considered illegal and the directory will be removed
+      # and a `HardLinkError` exception will be raised.
+      #
+      # @raise [HardLinkError] if there multiple hard links to the same file detected.
+      # @return [Boolean] true
+      def clean_extraction_dir!(dir)
         # Using File::FNM_DOTMATCH to also delete symlinks starting with "."
-        Dir.glob("#{dir}/**/*", File::FNM_DOTMATCH)
-          .reject { |f| ignore_file_names.include?(File.basename(f)) }
-          .each do |filepath|
-            FileUtils.rm(filepath) if File.lstat(filepath).symlink?
-          end
+        Dir.glob("#{dir}/**/*", File::FNM_DOTMATCH).each do |filepath|
+          next if CLEAN_DIR_IGNORE_FILE_NAMES.include?(File.basename(filepath))
+
+          raise HardLinkError, 'File shares hard link' if Gitlab::Utils::FileInfo.shares_hard_link?(filepath)
+
+          FileUtils.rm(filepath) if Gitlab::Utils::FileInfo.linked?(filepath)
+        end
 
         true
+      rescue HardLinkError
+        FileUtils.remove_dir(dir)
+        raise
       end
     end
   end
diff --git a/lib/gitlab/import_export/decompressed_archive_size_validator.rb b/lib/gitlab/import_export/decompressed_archive_size_validator.rb
index 104c9e6c456..2e39f3f38c2 100644
--- a/lib/gitlab/import_export/decompressed_archive_size_validator.rb
+++ b/lib/gitlab/import_export/decompressed_archive_size_validator.rb
@@ -87,7 +87,7 @@ module Gitlab
       def validate_archive_path
         Gitlab::PathTraversal.check_path_traversal!(@archive_path)
 
-        raise(ServiceError, 'Archive path is a symlink') if File.lstat(@archive_path).symlink?
+        raise(ServiceError, 'Archive path is a symlink or hard link') if Gitlab::Utils::FileInfo.linked?(@archive_path)
         raise(ServiceError, 'Archive path is not a file') unless File.file?(@archive_path)
       end
 
diff --git a/lib/gitlab/import_export/file_importer.rb b/lib/gitlab/import_export/file_importer.rb
index d2593289c23..37c83e88ef2 100644
--- a/lib/gitlab/import_export/file_importer.rb
+++ b/lib/gitlab/import_export/file_importer.rb
@@ -23,7 +23,7 @@ module Gitlab
         mkdir_p(@shared.export_path)
         mkdir_p(@shared.archive_path)
 
-        remove_symlinks(@shared.export_path)
+        clean_extraction_dir!(@shared.export_path)
         copy_archive
 
         wait_for_archived_file do
@@ -35,7 +35,7 @@ module Gitlab
         false
       ensure
         remove_import_file
-        remove_symlinks(@shared.export_path)
+        clean_extraction_dir!(@shared.export_path)
       end
 
       private
diff --git a/lib/gitlab/import_export/json/ndjson_reader.rb b/lib/gitlab/import_export/json/ndjson_reader.rb
index 3de56aacf18..93a94716f8d 100644
--- a/lib/gitlab/import_export/json/ndjson_reader.rb
+++ b/lib/gitlab/import_export/json/ndjson_reader.rb
@@ -21,7 +21,9 @@ module Gitlab
           # This reads from `tree/project.json`
           path = file_path("#{importable_path}.json")
 
-          raise Gitlab::ImportExport::Error, 'Invalid file' if !File.exist?(path) || File.symlink?(path)
+          if !File.exist?(path) || Gitlab::Utils::FileInfo.linked?(path)
+            raise Gitlab::ImportExport::Error, 'Invalid file'
+          end
 
           data = File.read(path, MAX_JSON_DOCUMENT_SIZE)
           json_decode(data)
@@ -34,7 +36,7 @@ module Gitlab
             # This reads from `tree/project/merge_requests.ndjson`
             path = file_path(importable_path, "#{key}.ndjson")
 
-            next if !File.exist?(path) || File.symlink?(path)
+            next if !File.exist?(path) || Gitlab::Utils::FileInfo.linked?(path)
 
             File.foreach(path, MAX_JSON_DOCUMENT_SIZE).with_index do |line, line_num|
               documents << [json_decode(line), line_num]
diff --git a/lib/gitlab/import_export/recursive_merge_folders.rb b/lib/gitlab/import_export/recursive_merge_folders.rb
index 827385d4daf..e6eba60db93 100644
--- a/lib/gitlab/import_export/recursive_merge_folders.rb
+++ b/lib/gitlab/import_export/recursive_merge_folders.rb
@@ -57,7 +57,7 @@ module Gitlab
           source_child = File.join(source_path, child)
           target_child = File.join(target_path, child)
 
-          next if File.lstat(source_child).symlink?
+          next if Gitlab::Utils::FileInfo.linked?(source_child)
 
           if File.directory?(source_child)
             FileUtils.mkdir_p(target_child, mode: DEFAULT_DIR_MODE) unless File.exist?(target_child)
diff --git a/lib/gitlab/plantuml.rb b/lib/gitlab/plantuml.rb
new file mode 100644
index 00000000000..9ec544452fd
--- /dev/null
+++ b/lib/gitlab/plantuml.rb
@@ -0,0 +1,20 @@
+# frozen_string_literal: true
+
+require "asciidoctor_plantuml/plantuml"
+
+module Gitlab
+  module Plantuml
+    class << self
+      def configure
+        Asciidoctor::PlantUml.configure do |conf|
+          conf.url        = Gitlab::CurrentSettings.plantuml_url
+          conf.png_enable = Gitlab::CurrentSettings.plantuml_enabled
+          conf.svg_enable = false
+          conf.txt_enable = false
+
+          conf
+        end
+      end
+    end
+  end
+end
diff --git a/lib/gitlab/utils/file_info.rb b/lib/gitlab/utils/file_info.rb
new file mode 100644
index 00000000000..a0ec370e225
--- /dev/null
+++ b/lib/gitlab/utils/file_info.rb
@@ -0,0 +1,35 @@
+# frozen_string_literal: true
+
+module Gitlab
+  module Utils
+    module FileInfo
+      class << self
+        # Returns true if:
+        # - File or directory is a symlink.
+        # - File shares a hard link.
+        def linked?(file)
+          stat = to_file_stat(file)
+
+          stat.symlink? || shares_hard_link?(stat)
+        end
+
+        # Returns:
+        # - true if file shares a hard link with another file.
+        # - false if file is a directory, as directories cannot be hard linked.
+        def shares_hard_link?(file)
+          stat = to_file_stat(file)
+
+          stat.file? && stat.nlink > 1
+        end
+
+        private
+
+        def to_file_stat(filepath_or_stat)
+          return filepath_or_stat if filepath_or_stat.is_a?(File::Stat)
+
+          File.lstat(filepath_or_stat)
+        end
+      end
+    end
+  end
+end
diff --git a/spec/lib/bulk_imports/common/pipelines/lfs_objects_pipeline_spec.rb b/spec/lib/bulk_imports/common/pipelines/lfs_objects_pipeline_spec.rb
index 297ac0ca0ba..50640e1e4ba 100644
--- a/spec/lib/bulk_imports/common/pipelines/lfs_objects_pipeline_spec.rb
+++ b/spec/lib/bulk_imports/common/pipelines/lfs_objects_pipeline_spec.rb
@@ -2,7 +2,7 @@
 
 require 'spec_helper'
 
-RSpec.describe BulkImports::Common::Pipelines::LfsObjectsPipeline do
+RSpec.describe BulkImports::Common::Pipelines::LfsObjectsPipeline, feature_category: :importers do
   let_it_be(:portable) { create(:project) }
   let_it_be(:oid) { 'e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855' }
 
@@ -118,13 +118,22 @@ RSpec.describe BulkImports::Common::Pipelines::LfsObjectsPipeline do
     context 'when file path is symlink' do
       it 'returns' do
         symlink = File.join(tmpdir, 'symlink')
+        FileUtils.ln_s(lfs_file_path, symlink)
 
-        FileUtils.ln_s(File.join(tmpdir, lfs_file_path), symlink)
-
+        expect(Gitlab::Utils::FileInfo).to receive(:linked?).with(symlink).and_call_original
         expect { pipeline.load(context, symlink) }.not_to change { portable.lfs_objects.count }
       end
     end
 
+    context 'when file path shares multiple hard links' do
+      it 'returns' do
+        FileUtils.link(lfs_file_path, File.join(tmpdir, 'hard_link'))
+
+        expect(Gitlab::Utils::FileInfo).to receive(:linked?).with(lfs_file_path).and_call_original
+        expect { pipeline.load(context, lfs_file_path) }.not_to change { portable.lfs_objects.count }
+      end
+    end
+
     context 'when path is a directory' do
       it 'returns' do
         expect { pipeline.load(context, Dir.tmpdir) }.not_to change { portable.lfs_objects.count }
diff --git a/spec/lib/bulk_imports/common/pipelines/uploads_pipeline_spec.rb b/spec/lib/bulk_imports/common/pipelines/uploads_pipeline_spec.rb
index bc6d36452b4..09c8c7b92c2 100644
--- a/spec/lib/bulk_imports/common/pipelines/uploads_pipeline_spec.rb
+++ b/spec/lib/bulk_imports/common/pipelines/uploads_pipeline_spec.rb
@@ -105,6 +105,7 @@ RSpec.describe BulkImports::Common::Pipelines::UploadsPipeline, feature_category
         it 'returns' do
           path = File.join(tmpdir, 'test')
           FileUtils.touch(path)
+
           expect { pipeline.load(context, path) }.not_to change { portable.uploads.count }
         end
       end
@@ -118,13 +119,22 @@ RSpec.describe BulkImports::Common::Pipelines::UploadsPipeline, feature_category
       context 'when path is a symlink' do
         it 'does not upload the file' do
           symlink = File.join(tmpdir, 'symlink')
+          FileUtils.ln_s(upload_file_path, symlink)
 
-          FileUtils.ln_s(File.join(tmpdir, upload_file_path), symlink)
-
+          expect(Gitlab::Utils::FileInfo).to receive(:linked?).with(symlink).and_call_original
           expect { pipeline.load(context, symlink) }.not_to change { portable.uploads.count }
         end
       end
 
+      context 'when path has multiple hard links' do
+        it 'does not upload the file' do
+          FileUtils.link(upload_file_path, File.join(tmpdir, 'hard_link'))
+
+          expect(Gitlab::Utils::FileInfo).to receive(:linked?).with(upload_file_path).and_call_original
+          expect { pipeline.load(context, upload_file_path) }.not_to change { portable.uploads.count }
+        end
+      end
+
       context 'when path traverses' do
         it 'does not upload the file' do
           path_traversal = "#{uploads_dir_path}/avatar/../../../../etc/passwd"
diff --git a/spec/lib/bulk_imports/projects/pipelines/design_bundle_pipeline_spec.rb b/spec/lib/bulk_imports/projects/pipelines/design_bundle_pipeline_spec.rb
index 5b7309b09f5..87efad92131 100644
--- a/spec/lib/bulk_imports/projects/pipelines/design_bundle_pipeline_spec.rb
+++ b/spec/lib/bulk_imports/projects/pipelines/design_bundle_pipeline_spec.rb
@@ -2,7 +2,7 @@
 
 require 'spec_helper'
 
-RSpec.describe BulkImports::Projects::Pipelines::DesignBundlePipeline do
+RSpec.describe BulkImports::Projects::Pipelines::DesignBundlePipeline, feature_category: :importers do
   let_it_be(:design) { create(:design, :with_file) }
 
   let(:portable) { create(:project) }
@@ -125,9 +125,9 @@ RSpec.describe BulkImports::Projects::Pipelines::DesignBundlePipeline do
     context 'when path is symlink' do
       it 'returns' do
         symlink = File.join(tmpdir, 'symlink')
+        FileUtils.ln_s(design_bundle_path, symlink)
 
-        FileUtils.ln_s(File.join(tmpdir, design_bundle_path), symlink)
-
+        expect(Gitlab::Utils::FileInfo).to receive(:linked?).with(symlink).and_call_original
         expect(portable.design_repository).not_to receive(:create_from_bundle)
 
         pipeline.load(context, symlink)
@@ -136,6 +136,19 @@ RSpec.describe BulkImports::Projects::Pipelines::DesignBundlePipeline do
       end
     end
 
+    context 'when path has multiple hard links' do
+      it 'returns' do
+        FileUtils.link(design_bundle_path, File.join(tmpdir, 'hard_link'))
+
+        expect(Gitlab::Utils::FileInfo).to receive(:linked?).with(design_bundle_path).and_call_original
+        expect(portable.design_repository).not_to receive(:create_from_bundle)
+
+        pipeline.load(context, design_bundle_path)
+
+        expect(portable.design_repository.exists?).to eq(false)
+      end
+    end
+
     context 'when path is not under tmpdir' do
       it 'returns' do
         expect { pipeline.load(context, '/home/test.txt') }
diff --git a/spec/lib/bulk_imports/projects/pipelines/repository_bundle_pipeline_spec.rb b/spec/lib/bulk_imports/projects/pipelines/repository_bundle_pipeline_spec.rb
index 07fafc19026..5aae8c959fa 100644
--- a/spec/lib/bulk_imports/projects/pipelines/repository_bundle_pipeline_spec.rb
+++ b/spec/lib/bulk_imports/projects/pipelines/repository_bundle_pipeline_spec.rb
@@ -2,7 +2,7 @@
 
 require 'spec_helper'
 
-RSpec.describe BulkImports::Projects::Pipelines::RepositoryBundlePipeline do
+RSpec.describe BulkImports::Projects::Pipelines::RepositoryBundlePipeline, feature_category: :importers do
   let_it_be(:source) { create(:project, :repository) }
 
   let(:portable) { create(:project) }
@@ -123,9 +123,9 @@ RSpec.describe BulkImports::Projects::Pipelines::RepositoryBundlePipeline do
     context 'when path is symlink' do
       it 'returns' do
         symlink = File.join(tmpdir, 'symlink')
+        FileUtils.ln_s(bundle_path, symlink)
 
-        FileUtils.ln_s(File.join(tmpdir, bundle_path), symlink)
-
+        expect(Gitlab::Utils::FileInfo).to receive(:linked?).with(symlink).and_call_original
         expect(portable.repository).not_to receive(:create_from_bundle)
 
         pipeline.load(context, symlink)
@@ -134,6 +134,19 @@ RSpec.describe BulkImports::Projects::Pipelines::RepositoryBundlePipeline do
       end
     end
 
+    context 'when path has mutiple hard links' do
+      it 'returns' do
+        FileUtils.link(bundle_path, File.join(tmpdir, 'hard_link'))
+
+        expect(Gitlab::Utils::FileInfo).to receive(:linked?).with(bundle_path).and_call_original
+        expect(portable.repository).not_to receive(:create_from_bundle)
+
+        pipeline.load(context, bundle_path)
+
+        expect(portable.repository.exists?).to eq(false)
+      end
+    end
+
     context 'when path is not under tmpdir' do
       it 'returns' do
         expect { pipeline.load(context, '/home/test.txt') }
diff --git a/spec/lib/gitlab/ci/decompressed_gzip_size_validator_spec.rb b/spec/lib/gitlab/ci/decompressed_gzip_size_validator_spec.rb
index 6ca3f4d415e..dad5bd2548b 100644
--- a/spec/lib/gitlab/ci/decompressed_gzip_size_validator_spec.rb
+++ b/spec/lib/gitlab/ci/decompressed_gzip_size_validator_spec.rb
@@ -105,6 +105,16 @@ RSpec.describe Gitlab::Ci::DecompressedGzipSizeValidator, feature_category: :imp
       end
     end
 
+    context 'when archive path has multiple hard links' do
+      before do
+        FileUtils.link(filepath, File.join(Dir.mktmpdir, 'hard_link'))
+      end
+
+      it 'returns false' do
+        expect(subject).not_to be_valid
+      end
+    end
+
     context 'when archive path is not a file' do
       let(:filepath) { Dir.mktmpdir }
       let(:filesize) { File.size(filepath) }
diff --git a/spec/lib/gitlab/github_import/attachments_downloader_spec.rb b/spec/lib/gitlab/github_import/attachments_downloader_spec.rb
index 84d6713efdb..086aa4be17e 100644
--- a/spec/lib/gitlab/github_import/attachments_downloader_spec.rb
+++ b/spec/lib/gitlab/github_import/attachments_downloader_spec.rb
@@ -2,7 +2,7 @@
 
 require 'spec_helper'
 
-RSpec.describe Gitlab::GithubImport::AttachmentsDownloader do
+RSpec.describe Gitlab::GithubImport::AttachmentsDownloader, feature_category: :importers do
   subject(:downloader) { described_class.new(file_url) }
 
   let_it_be(:file_url) { 'https://example.com/avatar.png' }
@@ -39,6 +39,26 @@ RSpec.describe Gitlab::GithubImport::AttachmentsDownloader do
       end
     end
 
+    context 'when file shares multiple hard links' do
+      let(:tmpdir) { Dir.mktmpdir }
+      let(:hard_link) { File.join(tmpdir, 'hard_link') }
+
+      before do
+        existing_file = File.join(tmpdir, 'file.txt')
+        FileUtils.touch(existing_file)
+        FileUtils.link(existing_file, hard_link)
+        allow(downloader).to receive(:filepath).and_return(hard_link)
+      end
+
+      it 'raises expected exception' do
+        expect(Gitlab::Utils::FileInfo).to receive(:linked?).with(hard_link).and_call_original
+        expect { downloader.perform }.to raise_exception(
+          described_class::DownloadError,
+          'Invalid downloaded file'
+        )
+      end
+    end
+
     context 'when filename is malicious' do
       let_it_be(:file_url) { 'https://example.com/ava%2F..%2Ftar.png' }
 
diff --git a/spec/lib/gitlab/import_export/command_line_util_spec.rb b/spec/lib/gitlab/import_export/command_line_util_spec.rb
index 91cfab1688a..b2e047f5621 100644
--- a/spec/lib/gitlab/import_export/command_line_util_spec.rb
+++ b/spec/lib/gitlab/import_export/command_line_util_spec.rb
@@ -5,13 +5,16 @@ require 'spec_helper'
 RSpec.describe Gitlab::ImportExport::CommandLineUtil, feature_category: :importers do
   include ExportFileHelper
 
-  let(:path) { "#{Dir.tmpdir}/symlink_test" }
-  let(:archive) { 'spec/fixtures/symlink_export.tar.gz' }
   let(:shared) { Gitlab::ImportExport::Shared.new(nil) }
-  let(:tmpdir) { Dir.mktmpdir }
+  # Separate where files are written during this test by their kind, to avoid them interfering with each other:
+  # - `source_dir` Dir to compress files from.
+  # - `target_dir` Dir to decompress archived files into.
+  # - `archive_dir` Dir to write any archive files to.
+  let(:source_dir) { Dir.mktmpdir }
+  let(:target_dir) { Dir.mktmpdir }
   let(:archive_dir) { Dir.mktmpdir }
 
-  subject do
+  subject(:mock_class) do
     Class.new do
       include Gitlab::ImportExport::CommandLineUtil
 
@@ -25,38 +28,59 @@ RSpec.describe Gitlab::ImportExport::CommandLineUtil, feature_category: :importe
   end
 
   before do
-    FileUtils.mkdir_p(path)
+    FileUtils.mkdir_p(source_dir)
   end
 
   after do
-    FileUtils.rm_rf(path)
+    FileUtils.rm_rf(source_dir)
+    FileUtils.rm_rf(target_dir)
     FileUtils.rm_rf(archive_dir)
-    FileUtils.remove_entry(tmpdir)
   end
 
   shared_examples 'deletes symlinks' do |compression, decompression|
     it 'deletes the symlinks', :aggregate_failures do
-      Dir.mkdir("#{tmpdir}/.git")
-      Dir.mkdir("#{tmpdir}/folder")
-      FileUtils.touch("#{tmpdir}/file.txt")
-      FileUtils.touch("#{tmpdir}/folder/file.txt")
-      FileUtils.touch("#{tmpdir}/.gitignore")
-      FileUtils.touch("#{tmpdir}/.git/config")
-      File.symlink('file.txt', "#{tmpdir}/.symlink")
-      File.symlink('file.txt', "#{tmpdir}/.git/.symlink")
-      File.symlink('file.txt', "#{tmpdir}/folder/.symlink")
-      archive = File.join(archive_dir, 'archive')
-      subject.public_send(compression, archive: archive, dir: tmpdir)
-
-      subject.public_send(decompression, archive: archive, dir: archive_dir)
-
-      expect(File.exist?("#{archive_dir}/file.txt")).to eq(true)
-      expect(File.exist?("#{archive_dir}/folder/file.txt")).to eq(true)
-      expect(File.exist?("#{archive_dir}/.gitignore")).to eq(true)
-      expect(File.exist?("#{archive_dir}/.git/config")).to eq(true)
-      expect(File.exist?("#{archive_dir}/.symlink")).to eq(false)
-      expect(File.exist?("#{archive_dir}/.git/.symlink")).to eq(false)
-      expect(File.exist?("#{archive_dir}/folder/.symlink")).to eq(false)
+      Dir.mkdir("#{source_dir}/.git")
+      Dir.mkdir("#{source_dir}/folder")
+      FileUtils.touch("#{source_dir}/file.txt")
+      FileUtils.touch("#{source_dir}/folder/file.txt")
+      FileUtils.touch("#{source_dir}/.gitignore")
+      FileUtils.touch("#{source_dir}/.git/config")
+      File.symlink('file.txt', "#{source_dir}/.symlink")
+      File.symlink('file.txt', "#{source_dir}/.git/.symlink")
+      File.symlink('file.txt', "#{source_dir}/folder/.symlink")
+      archive_file = File.join(archive_dir, 'symlink_archive.tar.gz')
+      subject.public_send(compression, archive: archive_file, dir: source_dir)
+      subject.public_send(decompression, archive: archive_file, dir: target_dir)
+
+      expect(File).to exist("#{target_dir}/file.txt")
+      expect(File).to exist("#{target_dir}/folder/file.txt")
+      expect(File).to exist("#{target_dir}/.gitignore")
+      expect(File).to exist("#{target_dir}/.git/config")
+      expect(File).not_to exist("#{target_dir}/.symlink")
+      expect(File).not_to exist("#{target_dir}/.git/.symlink")
+      expect(File).not_to exist("#{target_dir}/folder/.symlink")
+    end
+  end
+
+  shared_examples 'handles shared hard links' do |compression, decompression|
+    let(:archive_file) { File.join(archive_dir, 'hard_link_archive.tar.gz') }
+
+    subject(:decompress) { mock_class.public_send(decompression, archive: archive_file, dir: target_dir) }
+
+    before do
+      Dir.mkdir("#{source_dir}/dir")
+      FileUtils.touch("#{source_dir}/file.txt")
+      FileUtils.touch("#{source_dir}/dir/.file.txt")
+      FileUtils.link("#{source_dir}/file.txt", "#{source_dir}/.hard_linked_file.txt")
+
+      mock_class.public_send(compression, archive: archive_file, dir: source_dir)
+    end
+
+    it 'raises an exception and deletes the extraction dir', :aggregate_failures do
+      expect(FileUtils).to receive(:remove_dir).with(target_dir).and_call_original
+      expect(Dir).to exist(target_dir)
+      expect { decompress }.to raise_error(described_class::HardLinkError)
+      expect(Dir).not_to exist(target_dir)
     end
   end
 
@@ -212,6 +236,8 @@ RSpec.describe Gitlab::ImportExport::CommandLineUtil, feature_category: :importe
   end
 
   describe '#gzip' do
+    let(:path) { source_dir }
+
     it 'compresses specified file' do
       tempfile = Tempfile.new('test', path)
       filename = File.basename(tempfile.path)
@@ -229,14 +255,16 @@ RSpec.describe Gitlab::ImportExport::CommandLineUtil, feature_category: :importe
   end
 
   describe '#gunzip' do
+    let(:path) { source_dir }
+
     it 'decompresses specified file' do
       filename = 'labels.ndjson.gz'
       gz_filepath = "spec/fixtures/bulk_imports/gz/#{filename}"
-      FileUtils.copy_file(gz_filepath, File.join(tmpdir, filename))
+      FileUtils.copy_file(gz_filepath, File.join(path, filename))
 
-      subject.gunzip(dir: tmpdir, filename: filename)
+      subject.gunzip(dir: path, filename: filename)
 
-      expect(File.exist?(File.join(tmpdir, 'labels.ndjson'))).to eq(true)
+      expect(File.exist?(File.join(path, 'labels.ndjson'))).to eq(true)
     end
 
     context 'when exception occurs' do
@@ -250,7 +278,7 @@ RSpec.describe Gitlab::ImportExport::CommandLineUtil, feature_category: :importe
     it 'archives a folder without compression' do
       archive_file = File.join(archive_dir, 'archive.tar')
 
-      result = subject.tar_cf(archive: archive_file, dir: tmpdir)
+      result = subject.tar_cf(archive: archive_file, dir: source_dir)
 
       expect(result).to eq(true)
       expect(File.exist?(archive_file)).to eq(true)
@@ -270,29 +298,35 @@ RSpec.describe Gitlab::ImportExport::CommandLineUtil, feature_category: :importe
   end
 
   describe '#untar_zxf' do
+    let(:tar_archive_fixture) { 'spec/fixtures/symlink_export.tar.gz' }
+
     it_behaves_like 'deletes symlinks', :tar_czf, :untar_zxf
+    it_behaves_like 'handles shared hard links', :tar_czf, :untar_zxf
 
     it 'has the right mask for project.json' do
-      subject.untar_zxf(archive: archive, dir: path)
+      subject.untar_zxf(archive: tar_archive_fixture, dir: target_dir)
 
-      expect(file_permissions("#{path}/project.json")).to eq(0755) # originally 777
+      expect(file_permissions("#{target_dir}/project.json")).to eq(0755) # originally 777
     end
 
     it 'has the right mask for uploads' do
-      subject.untar_zxf(archive: archive, dir: path)
+      subject.untar_zxf(archive: tar_archive_fixture, dir: target_dir)
 
-      expect(file_permissions("#{path}/uploads")).to eq(0755) # originally 555
+      expect(file_permissions("#{target_dir}/uploads")).to eq(0755) # originally 555
     end
   end
 
   describe '#untar_xf' do
+    let(:tar_archive_fixture) { 'spec/fixtures/symlink_export.tar.gz' }
+
     it_behaves_like 'deletes symlinks', :tar_cf, :untar_xf
+    it_behaves_like 'handles shared hard links', :tar_cf, :untar_xf
 
     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))
+      FileUtils.copy_file(tar_archive_fixture, File.join(archive_dir, filename))
       subject.gunzip(dir: archive_dir, filename: filename)
 
       result = subject.untar_xf(archive: archive_file, dir: archive_dir)
diff --git a/spec/lib/gitlab/import_export/decompressed_archive_size_validator_spec.rb b/spec/lib/gitlab/import_export/decompressed_archive_size_validator_spec.rb
index a6cb74c3c9f..8c5823edc51 100644
--- a/spec/lib/gitlab/import_export/decompressed_archive_size_validator_spec.rb
+++ b/spec/lib/gitlab/import_export/decompressed_archive_size_validator_spec.rb
@@ -2,7 +2,7 @@
 
 require 'spec_helper'
 
-RSpec.describe Gitlab::ImportExport::DecompressedArchiveSizeValidator do
+RSpec.describe Gitlab::ImportExport::DecompressedArchiveSizeValidator, feature_category: :importers do
   let_it_be(:filepath) { File.join(Dir.tmpdir, 'decompressed_archive_size_validator_spec.gz') }
 
   before(:all) do
@@ -121,7 +121,7 @@ RSpec.describe Gitlab::ImportExport::DecompressedArchiveSizeValidator do
 
       context 'which archive path is a symlink' do
         let(:filepath) { File.join(Dir.tmpdir, 'symlink') }
-        let(:error_message) { 'Archive path is a symlink' }
+        let(:error_message) { 'Archive path is a symlink or hard link' }
 
         before do
           FileUtils.ln_s(filepath, filepath, force: true)
@@ -132,6 +132,19 @@ RSpec.describe Gitlab::ImportExport::DecompressedArchiveSizeValidator do
         end
       end
 
+      context 'when archive path shares multiple hard links' do
+        let(:filesize) { 32 }
+        let(:error_message) { 'Archive path is a symlink or hard link' }
+
+        before do
+          FileUtils.link(filepath, File.join(Dir.mktmpdir, 'hard_link'))
+        end
+
+        it 'returns false' do
+          expect(subject).not_to be_valid
+        end
+      end
+
       context 'when archive path is not a file' do
         let(:filepath) { Dir.mktmpdir }
         let(:filesize) { File.size(filepath) }
diff --git a/spec/lib/gitlab/import_export/file_importer_spec.rb b/spec/lib/gitlab/import_export/file_importer_spec.rb
index 5a75631ec4d..aff11f7ac30 100644
--- a/spec/lib/gitlab/import_export/file_importer_spec.rb
+++ b/spec/lib/gitlab/import_export/file_importer_spec.rb
@@ -2,7 +2,7 @@
 
 require 'spec_helper'
 
-RSpec.describe Gitlab::ImportExport::FileImporter do
+RSpec.describe Gitlab::ImportExport::FileImporter, feature_category: :importers do
   include ExportFileHelper
 
   let(:shared) { Gitlab::ImportExport::Shared.new(nil) }
@@ -113,28 +113,73 @@ RSpec.describe Gitlab::ImportExport::FileImporter do
   end
 
   context 'error' do
+    subject(:import) { described_class.import(importable: build(:project), archive_file: '', shared: shared) }
+
     before do
       allow_next_instance_of(described_class) do |instance|
-        allow(instance).to receive(:wait_for_archived_file).and_raise(StandardError)
+        allow(instance).to receive(:wait_for_archived_file).and_raise(StandardError, 'foo')
       end
-      described_class.import(importable: build(:project), archive_file: '', shared: shared)
     end
 
     it 'removes symlinks in root folder' do
+      import
+
       expect(File.exist?(symlink_file)).to be false
     end
 
     it 'removes hidden symlinks in root folder' do
+      import
+
       expect(File.exist?(hidden_symlink_file)).to be false
     end
 
     it 'removes symlinks in subfolders' do
+      import
+
       expect(File.exist?(subfolder_symlink_file)).to be false
     end
 
     it 'does not remove a valid file' do
+      import
+
       expect(File.exist?(valid_file)).to be true
     end
+
+    it 'returns false and sets an error on shared' do
+      result = import
+
+      expect(result).to eq(false)
+      expect(shared.errors.join).to eq('foo')
+    end
+
+    context 'when files in the archive share hard links' do
+      let(:hard_link_file) { "#{shared.export_path}/hard_link_file.txt" }
+
+      before do
+        FileUtils.link(valid_file, hard_link_file)
+      end
+
+      it 'returns false and sets an error on shared' do
+        result = import
+
+        expect(result).to eq(false)
+        expect(shared.errors.join).to eq('File shares hard link')
+      end
+
+      it 'removes all files in export path' do
+        expect(Dir).to exist(shared.export_path)
+        expect(File).to exist(symlink_file)
+        expect(File).to exist(hard_link_file)
+        expect(File).to exist(valid_file)
+
+        import
+
+        expect(File).not_to exist(symlink_file)
+        expect(File).not_to exist(hard_link_file)
+        expect(File).not_to exist(valid_file)
+        expect(Dir).not_to exist(shared.export_path)
+      end
+    end
   end
 
   context 'when file exceeds acceptable decompressed size' do
@@ -157,8 +202,10 @@ RSpec.describe Gitlab::ImportExport::FileImporter do
         allow(Gitlab::ImportExport::DecompressedArchiveSizeValidator).to receive(:max_bytes).and_return(1)
       end
 
-      it 'returns false' do
-        expect(subject.import).to eq(false)
+      it 'returns false and sets an error on shared' do
+        result = subject.import
+
+        expect(result).to eq(false)
         expect(shared.errors.join).to eq('Decompressed archive size validation failed.')
       end
     end
diff --git a/spec/lib/gitlab/import_export/json/ndjson_reader_spec.rb b/spec/lib/gitlab/import_export/json/ndjson_reader_spec.rb
index 98afe01c08b..1f98a9efb7d 100644
--- a/spec/lib/gitlab/import_export/json/ndjson_reader_spec.rb
+++ b/spec/lib/gitlab/import_export/json/ndjson_reader_spec.rb
@@ -35,16 +35,22 @@ RSpec.describe Gitlab::ImportExport::Json::NdjsonReader, feature_category: :impo
       expect(subject).to eq(root_tree)
     end
 
-    context 'when project.json is symlink' do
-      it 'raises error an error' do
-        Dir.mktmpdir do |tmpdir|
-          FileUtils.touch(File.join(tmpdir, 'passwd'))
-          File.symlink(File.join(tmpdir, 'passwd'), File.join(tmpdir, 'project.json'))
+    context 'when project.json is symlink or hard link' do
+      using RSpec::Parameterized::TableSyntax
 
-          ndjson_reader = described_class.new(tmpdir)
+      where(:link_method) { [:link, :symlink] }
 
-          expect { ndjson_reader.consume_attributes(importable_path) }
-            .to raise_error(Gitlab::ImportExport::Error, 'Invalid file')
+      with_them do
+        it 'raises an error' do
+          Dir.mktmpdir do |tmpdir|
+            FileUtils.touch(File.join(tmpdir, 'passwd'))
+            FileUtils.send(link_method, File.join(tmpdir, 'passwd'), File.join(tmpdir, 'project.json'))
+
+            ndjson_reader = described_class.new(tmpdir)
+
+            expect { ndjson_reader.consume_attributes(importable_path) }
+              .to raise_error(Gitlab::ImportExport::Error, 'Invalid file')
+          end
         end
       end
     end
@@ -97,18 +103,24 @@ RSpec.describe Gitlab::ImportExport::Json::NdjsonReader, feature_category: :impo
         end
       end
 
-      context 'when relation file is a symlink' do
-        it 'yields nothing to the Enumerator' do
-          Dir.mktmpdir do |tmpdir|
-            Dir.mkdir(File.join(tmpdir, 'project'))
-            File.write(File.join(tmpdir, 'passwd'), "{}\n{}")
-            File.symlink(File.join(tmpdir, 'passwd'), File.join(tmpdir, 'project', 'issues.ndjson'))
+      context 'when relation file is a symlink or hard link' do
+        using RSpec::Parameterized::TableSyntax
 
-            ndjson_reader = described_class.new(tmpdir)
+        where(:link_method) { [:link, :symlink] }
+
+        with_them do
+          it 'yields nothing to the Enumerator' do
+            Dir.mktmpdir do |tmpdir|
+              Dir.mkdir(File.join(tmpdir, 'project'))
+              File.write(File.join(tmpdir, 'passwd'), "{}\n{}")
+              FileUtils.send(link_method, File.join(tmpdir, 'passwd'), File.join(tmpdir, 'project', 'issues.ndjson'))
+
+              ndjson_reader = described_class.new(tmpdir)
 
-            result = ndjson_reader.consume_relation(importable_path, 'issues')
+              result = ndjson_reader.consume_relation(importable_path, 'issues')
 
-            expect(result.to_a).to eq([])
+              expect(result.to_a).to eq([])
+            end
           end
         end
       end
diff --git a/spec/lib/gitlab/import_export/recursive_merge_folders_spec.rb b/spec/lib/gitlab/import_export/recursive_merge_folders_spec.rb
index cb8ac088493..2b9590da421 100644
--- a/spec/lib/gitlab/import_export/recursive_merge_folders_spec.rb
+++ b/spec/lib/gitlab/import_export/recursive_merge_folders_spec.rb
@@ -4,15 +4,17 @@ require 'spec_helper'
 
 RSpec.describe Gitlab::ImportExport::RecursiveMergeFolders do
   describe '.merge' do
-    it 'merge folder and ignore symlinks' do
+    it 'merges folder and ignores symlinks and files that share hard links' do
       Dir.mktmpdir do |tmpdir|
         source = "#{tmpdir}/source"
         FileUtils.mkdir_p("#{source}/folder/folder")
         FileUtils.touch("#{source}/file1.txt")
+        FileUtils.touch("#{source}/file_that_shares_hard_links.txt")
         FileUtils.touch("#{source}/folder/file2.txt")
         FileUtils.touch("#{source}/folder/folder/file3.txt")
         FileUtils.ln_s("#{source}/file1.txt", "#{source}/symlink-file1.txt")
         FileUtils.ln_s("#{source}/folder", "#{source}/symlink-folder")
+        FileUtils.link("#{source}/file_that_shares_hard_links.txt", "#{source}/hard_link.txt")
 
         target = "#{tmpdir}/target"
         FileUtils.mkdir_p("#{target}/folder/folder")
diff --git a/spec/lib/gitlab/plantuml_spec.rb b/spec/lib/gitlab/plantuml_spec.rb
new file mode 100644
index 00000000000..c783dd66c48
--- /dev/null
+++ b/spec/lib/gitlab/plantuml_spec.rb
@@ -0,0 +1,59 @@
+# frozen_string_literal: true
+
+require "spec_helper"
+
+RSpec.describe Gitlab::Plantuml, feature_category: :shared do
+  describe ".configure" do
+    subject { described_class.configure }
+
+    let(:plantuml_url) { "http://plantuml.foo.bar" }
+
+    before do
+      allow(Gitlab::CurrentSettings).to receive(:plantuml_url).and_return(plantuml_url)
+    end
+
+    context "when PlantUML is enabled" do
+      before do
+        allow(Gitlab::CurrentSettings).to receive(:plantuml_enabled).and_return(true)
+      end
+
+      it "configures the endpoint URL" do
+        expect(subject.url).to eq(plantuml_url)
+      end
+
+      it "enables PNG support" do
+        expect(subject.png_enable).to be_truthy
+      end
+
+      it "disables SVG support" do
+        expect(subject.svg_enable).to be_falsey
+      end
+
+      it "disables TXT support" do
+        expect(subject.txt_enable).to be_falsey
+      end
+    end
+
+    context "when PlantUML is disabled" do
+      before do
+        allow(Gitlab::CurrentSettings).to receive(:plantuml_enabled).and_return(false)
+      end
+
+      it "configures the endpoint URL" do
+        expect(subject.url).to eq(plantuml_url)
+      end
+
+      it "enables PNG support" do
+        expect(subject.png_enable).to be_falsey
+      end
+
+      it "disables SVG support" do
+        expect(subject.svg_enable).to be_falsey
+      end
+
+      it "disables TXT support" do
+        expect(subject.txt_enable).to be_falsey
+      end
+    end
+  end
+end
diff --git a/spec/lib/gitlab/utils/file_info_spec.rb b/spec/lib/gitlab/utils/file_info_spec.rb
new file mode 100644
index 00000000000..480036b2fd0
--- /dev/null
+++ b/spec/lib/gitlab/utils/file_info_spec.rb
@@ -0,0 +1,88 @@
+# frozen_string_literal: true
+
+require 'fast_spec_helper'
+
+RSpec.describe Gitlab::Utils::FileInfo, feature_category: :shared do
+  let(:tmpdir) { Dir.mktmpdir }
+  let(:file_path) { "#{tmpdir}/test.txt" }
+
+  before do
+    FileUtils.touch(file_path)
+  end
+
+  after do
+    FileUtils.rm_rf(tmpdir)
+  end
+
+  describe '.linked?' do
+    it 'raises an error when file does not exist' do
+      expect { subject.linked?('foo') }.to raise_error(Errno::ENOENT)
+    end
+
+    shared_examples 'identifies a linked file' do
+      it 'returns false when file or dir is not a link' do
+        expect(subject.linked?(tmpdir)).to eq(false)
+        expect(subject.linked?(file)).to eq(false)
+      end
+
+      it 'returns true when file or dir is symlinked' do
+        FileUtils.symlink(tmpdir, "#{tmpdir}/symlinked_dir")
+        FileUtils.symlink(file_path, "#{tmpdir}/symlinked_file.txt")
+
+        expect(subject.linked?("#{tmpdir}/symlinked_dir")).to eq(true)
+        expect(subject.linked?("#{tmpdir}/symlinked_file.txt")).to eq(true)
+      end
+
+      it 'returns true when file has more than one hard link' do
+        FileUtils.link(file_path, "#{tmpdir}/hardlinked_file.txt")
+
+        expect(subject.linked?(file)).to eq(true)
+        expect(subject.linked?("#{tmpdir}/hardlinked_file.txt")).to eq(true)
+      end
+    end
+
+    context 'when file is a File::Stat' do
+      let(:file) { File.lstat(file_path) }
+
+      it_behaves_like 'identifies a linked file'
+    end
+
+    context 'when file is path' do
+      let(:file) { file_path }
+
+      it_behaves_like 'identifies a linked file'
+    end
+  end
+
+  describe '.shares_hard_link?' do
+    it 'raises an error when file does not exist' do
+      expect { subject.shares_hard_link?('foo') }.to raise_error(Errno::ENOENT)
+    end
+
+    shared_examples 'identifies a file that shares a hard link' do
+      it 'returns false when file or dir does not share hard links' do
+        expect(subject.shares_hard_link?(tmpdir)).to eq(false)
+        expect(subject.shares_hard_link?(file)).to eq(false)
+      end
+
+      it 'returns true when file has more than one hard link' do
+        FileUtils.link(file_path, "#{tmpdir}/hardlinked_file.txt")
+
+        expect(subject.shares_hard_link?(file)).to eq(true)
+        expect(subject.shares_hard_link?("#{tmpdir}/hardlinked_file.txt")).to eq(true)
+      end
+    end
+
+    context 'when file is a File::Stat' do
+      let(:file) { File.lstat(file_path) }
+
+      it_behaves_like 'identifies a file that shares a hard link'
+    end
+
+    context 'when file is path' do
+      let(:file) { file_path }
+
+      it_behaves_like 'identifies a file that shares a hard link'
+    end
+  end
+end
diff --git a/spec/services/bulk_imports/archive_extraction_service_spec.rb b/spec/services/bulk_imports/archive_extraction_service_spec.rb
index 5593218c259..f76ac722ad7 100644
--- a/spec/services/bulk_imports/archive_extraction_service_spec.rb
+++ b/spec/services/bulk_imports/archive_extraction_service_spec.rb
@@ -43,13 +43,21 @@ RSpec.describe BulkImports::ArchiveExtractionService, feature_category: :importe
 
     context 'when archive file is a symlink' do
       it 'raises an error' do
-        FileUtils.ln_s(File.join(tmpdir, filename), File.join(tmpdir, 'symlink'))
+        FileUtils.ln_s(filepath, File.join(tmpdir, 'symlink'))
 
         expect { described_class.new(tmpdir: tmpdir, filename: 'symlink').execute }
           .to raise_error(BulkImports::Error, 'Invalid file')
       end
     end
 
+    context 'when archive file shares multiple hard links' do
+      it 'raises an error' do
+        FileUtils.link(filepath, File.join(tmpdir, 'hard_link'))
+
+        expect { subject.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(Dir.mktmpdir, 'test', '..'), filename: 'name').execute }
diff --git a/spec/services/bulk_imports/file_decompression_service_spec.rb b/spec/services/bulk_imports/file_decompression_service_spec.rb
index 9d80ab3cd8f..e6d919c3499 100644
--- a/spec/services/bulk_imports/file_decompression_service_spec.rb
+++ b/spec/services/bulk_imports/file_decompression_service_spec.rb
@@ -3,6 +3,8 @@
 require 'spec_helper'
 
 RSpec.describe BulkImports::FileDecompressionService, feature_category: :importers do
+  using RSpec::Parameterized::TableSyntax
+
   let_it_be(:tmpdir) { Dir.mktmpdir }
   let_it_be(:ndjson_filename) { 'labels.ndjson' }
   let_it_be(:ndjson_filepath) { File.join(tmpdir, ndjson_filename) }
@@ -70,39 +72,68 @@ RSpec.describe BulkImports::FileDecompressionService, feature_category: :importe
       end
     end
 
-    context 'when compressed file is a symlink' do
-      let_it_be(:symlink) { File.join(tmpdir, 'symlink.gz') }
+    shared_examples 'raises an error and removes the file' do |error_message:|
+      specify do
+        expect { subject.execute }
+          .to raise_error(BulkImports::FileDecompressionService::ServiceError, error_message)
+        expect(File).not_to exist(file)
+      end
+    end
+
+    shared_context 'when compressed file' do
+      let_it_be(:file) { File.join(tmpdir, 'file.gz') }
+
+      subject { described_class.new(tmpdir: tmpdir, filename: 'file.gz') }
 
       before do
-        FileUtils.ln_s(File.join(tmpdir, gz_filename), symlink)
+        FileUtils.send(link_method, File.join(tmpdir, gz_filename), file)
       end
+    end
 
-      subject { described_class.new(tmpdir: tmpdir, filename: 'symlink.gz') }
+    shared_context 'when decompressed file' do
+      let_it_be(:file) { File.join(tmpdir, 'file.txt') }
 
-      it 'raises an error and removes the file' do
-        expect { subject.execute }
-          .to raise_error(BulkImports::FileDecompressionService::ServiceError, 'File decompression error')
+      subject { described_class.new(tmpdir: tmpdir, filename: gz_filename) }
 
-        expect(File.exist?(symlink)).to eq(false)
+      before do
+        original_file = File.join(tmpdir, 'original_file.txt')
+        FileUtils.touch(original_file)
+        FileUtils.send(link_method, original_file, file)
+
+        subject.instance_variable_set(:@decompressed_filepath, file)
       end
     end
 
+    context 'when compressed file is a symlink' do
+      let(:link_method) { :symlink }
+
+      include_context 'when compressed file'
+
+      include_examples 'raises an error and removes the file', error_message: 'File decompression error'
+    end
+
+    context 'when compressed file shares multiple hard links' do
+      let(:link_method) { :link }
+
+      include_context 'when compressed file'
+
+      include_examples 'raises an error and removes the file', error_message: 'File decompression error'
+    end
+
     context 'when decompressed file is a symlink' do
-      let_it_be(:symlink) { File.join(tmpdir, 'symlink') }
+      let(:link_method) { :symlink }
 
-      before do
-        FileUtils.ln_s(File.join(tmpdir, ndjson_filename), symlink)
+      include_context 'when decompressed file'
 
-        subject.instance_variable_set(:@decompressed_filepath, symlink)
-      end
+      include_examples 'raises an error and removes the file', error_message: 'Invalid file'
+    end
 
-      subject { described_class.new(tmpdir: tmpdir, filename: gz_filename) }
+    context 'when decompressed file shares multiple hard links' do
+      let(:link_method) { :link }
 
-      it 'raises an error and removes the file' do
-        expect { subject.execute }.to raise_error(described_class::ServiceError, 'Invalid file')
+      include_context 'when decompressed file'
 
-        expect(File.exist?(symlink)).to eq(false)
-      end
+      include_examples 'raises an error and removes the file', error_message: 'Invalid file'
     end
   end
 end
diff --git a/spec/services/bulk_imports/file_download_service_spec.rb b/spec/services/bulk_imports/file_download_service_spec.rb
index cbeea5b0f46..c035eabf767 100644
--- a/spec/services/bulk_imports/file_download_service_spec.rb
+++ b/spec/services/bulk_imports/file_download_service_spec.rb
@@ -10,7 +10,7 @@ RSpec.describe BulkImports::FileDownloadService, feature_category: :importers do
     let_it_be(:content_type) { 'application/octet-stream' }
     let_it_be(:content_disposition) { nil }
     let_it_be(:filename) { 'file_download_service_spec' }
-    let_it_be(:tmpdir) { Dir.tmpdir }
+    let_it_be(:tmpdir) { Dir.mktmpdir }
     let_it_be(:filepath) { File.join(tmpdir, filename) }
     let_it_be(:content_length) { 1000 }
 
@@ -247,6 +247,36 @@ RSpec.describe BulkImports::FileDownloadService, feature_category: :importers do
       end
     end
 
+    context 'when file shares multiple hard links' do
+      let_it_be(:hard_link) { File.join(tmpdir, 'hard_link') }
+
+      before do
+        existing_file = File.join(Dir.mktmpdir, filename)
+        FileUtils.touch(existing_file)
+        FileUtils.link(existing_file, hard_link)
+      end
+
+      subject do
+        described_class.new(
+          configuration: config,
+          relative_url: '/test',
+          tmpdir: tmpdir,
+          filename: 'hard_link',
+          file_size_limit: file_size_limit,
+          allowed_content_types: allowed_content_types
+        )
+      end
+
+      it 'raises an error and removes the file' do
+        expect { subject.execute }.to raise_error(
+          described_class::ServiceError,
+          'Invalid downloaded file'
+        )
+
+        expect(File.exist?(hard_link)).to eq(false)
+      end
+    end
+
     context 'when dir is not in tmpdir' do
       subject do
         described_class.new(