1 files changed, 169 insertions, 0 deletions
diff --git a/lib/rubygems/package/old.rb b/lib/rubygems/package/old.rb
new file mode 100644
index 0000000000..1a13ac3e29
--- /dev/null
+++ b/lib/rubygems/package/old.rb
@@ -0,0 +1,169 @@
+# frozen_string_literal: true
+
+#--
+# Copyright 2006 by Chad Fowler, Rich Kilmer, Jim Weirich and others.
+# All rights reserved.
+# See LICENSE.txt for permissions.
+#++
+
+##
+# The format class knows the guts of the ancient .gem file format and provides
+# the capability to read such ancient gems.
+#
+# Please pretend this doesn't exist.
+
+class Gem::Package::Old < Gem::Package
+  undef_method :spec=
+
+  ##
+  # Creates a new old-format package reader for +gem+.  Old-format packages
+  # cannot be written.
+
+  def initialize(gem, security_policy)
+    require "fileutils"
+    require "zlib"
+    Gem.load_yaml
+
+    @contents        = nil
+    @gem             = gem
+    @security_policy = security_policy
+    @spec            = nil
+  end
+
+  ##
+  # A list of file names contained in this gem
+
+  def contents
+    verify
+
+    return @contents if @contents
+
+    @gem.with_read_io do |io|
+      read_until_dashes io # spec
+      header = file_list io
+
+      @contents = header.map {|file| file["path"] }
+    end
+  end
+
+  ##
+  # Extracts the files in this package into +destination_dir+
+
+  def extract_files(destination_dir)
+    verify
+
+    errstr = "Error reading files from gem"
+
+    @gem.with_read_io do |io|
+      read_until_dashes io # spec
+      header = file_list io
+      raise Gem::Exception, errstr unless header
+
+      header.each do |entry|
+        full_name = entry["path"]
+
+        destination = install_location full_name, destination_dir
+
+        file_data = String.new
+
+        read_until_dashes io do |line|
+          file_data << line
+        end
+
+        file_data = file_data.strip.unpack1("m")
+        file_data = Zlib::Inflate.inflate file_data
+
+        raise Gem::Package::FormatError, "#{full_name} in #{@gem} is corrupt" if
+          file_data.length != entry["size"].to_i
+
+        FileUtils.rm_rf destination
+
+        FileUtils.mkdir_p File.dirname(destination), mode: dir_mode && 0o755
+
+        File.open destination, "wb", file_mode(entry["mode"]) do |out|
+          out.write file_data
+        end
+
+        verbose destination
+      end
+    end
+  rescue Zlib::DataError
+    raise Gem::Exception, errstr
+  end
+
+  ##
+  # Reads the file list section from the old-format gem +io+
+
+  def file_list(io) # :nodoc:
+    header = String.new
+
+    read_until_dashes io do |line|
+      header << line
+    end
+
+    Gem::SafeYAML.safe_load header
+  end
+
+  ##
+  # Reads lines until a "---" separator is found
+
+  def read_until_dashes(io) # :nodoc:
+    while (line = io.gets) && line.chomp.strip != "---" do
+      yield line if block_given?
+    end
+  end
+
+  ##
+  # Skips the Ruby self-install header in +io+.
+
+  def skip_ruby(io) # :nodoc:
+    loop do
+      line = io.gets
+
+      return if line.chomp == "__END__"
+      break unless line
+    end
+
+    raise Gem::Exception, "Failed to find end of Ruby script while reading gem"
+  end
+
+  ##
+  # The specification for this gem
+
+  def spec
+    verify
+
+    return @spec if @spec
+
+    yaml = String.new
+
+    @gem.with_read_io do |io|
+      skip_ruby io
+      read_until_dashes io do |line|
+        yaml << line
+      end
+    end
+
+    begin
+      @spec = Gem::Specification.from_yaml yaml
+    rescue Psych::SyntaxError
+      raise Gem::Exception, "Failed to parse gem specification out of gem file"
+    end
+  rescue ArgumentError
+    raise Gem::Exception, "Failed to parse gem specification out of gem file"
+  end
+
+  ##
+  # Raises an exception if a security policy that verifies data is active.
+  # Old format gems cannot be verified as signed.
+
+  def verify
+    return true unless @security_policy
+
+    raise Gem::Security::Exception,
+          "old format gems do not contain signatures and cannot be verified" if
+      @security_policy.verify_data
+
+    true
+  end
+end