1 files changed, 97 insertions, 0 deletions
diff --git a/lib/safe_zip/entry.rb b/lib/safe_zip/entry.rb
new file mode 100644
index 00000000000..664e2f52f91
--- /dev/null
+++ b/lib/safe_zip/entry.rb
@@ -0,0 +1,97 @@
+# frozen_string_literal: true
+
+module SafeZip
+  class Entry
+    attr_reader :zip_archive, :zip_entry
+    attr_reader :path, :params
+
+    def initialize(zip_archive, zip_entry, params)
+      @zip_archive = zip_archive
+      @zip_entry = zip_entry
+      @params = params
+      @path = ::File.expand_path(zip_entry.name, params.extract_path)
+    end
+
+    def path_dir
+      ::File.dirname(path)
+    end
+
+    def real_path_dir
+      ::File.realpath(path_dir)
+    end
+
+    def exist?
+      ::File.exist?(path)
+    end
+
+    def extract
+      # do not extract if file is not part of target directory
+      return false unless matching_target_directory
+
+      # do not overwrite existing file
+      raise SafeZip::Extract::AlreadyExistsError, "File already exists #{zip_entry.name}" if exist?
+
+      create_path_dir
+
+      if zip_entry.file?
+        extract_file
+      elsif zip_entry.directory?
+        extract_dir
+      elsif zip_entry.symlink?
+        extract_symlink
+      else
+        raise SafeZip::Extract::UnsupportedEntryError, "File #{zip_entry.name} cannot be extracted"
+      end
+    rescue SafeZip::Extract::Error
+      raise
+    rescue => e
+      raise SafeZip::Extract::ExtractError, e.message
+    end
+
+    private
+
+    def extract_file
+      zip_archive.extract(zip_entry, path)
+    end
+
+    def extract_dir
+      FileUtils.mkdir(path)
+    end
+
+    def extract_symlink
+      source_path = read_symlink
+      real_source_path = expand_symlink(source_path)
+
+      # ensure that source path of symlink is within target directories
+      unless real_source_path.start_with?(matching_target_directory)
+        raise SafeZip::Extract::PermissionDeniedError, "Symlink cannot be created targeting: #{source_path}"
+      end
+
+      ::File.symlink(source_path, path)
+    end
+
+    def create_path_dir
+      # Create all directories, but ignore permissions
+      FileUtils.mkdir_p(path_dir)
+
+      # disallow to make path dirs to point to another directories
+      unless path_dir == real_path_dir
+        raise SafeZip::Extract::PermissionDeniedError, "Directory of #{zip_entry.name} points to another directory"
+      end
+    end
+
+    def matching_target_directory
+      params.matching_target_directory(path)
+    end
+
+    def read_symlink
+      zip_archive.read(zip_entry)
+    end
+
+    def expand_symlink(source_path)
+      ::File.realpath(source_path, path_dir)
+    rescue
+      raise SafeZip::Extract::SymlinkSourceDoesNotExistError, "Symlink source #{source_path} does not exist"
+    end
+  end
+end