Patch bundler to not use temp directory as home

Patch for CVE-2019-3881

changelogs/unreleased/secuirty-bundler-secure-tmp-home.yml

+---
+title: Patch bundler to not use insecure temp directory as home
+merge_request:
+author:
+type: security

config/patches/bundler/secure-temporary-dir-as-home.patch

+diff --git a/lib/bundler.rb b/lib/bundler.rb
+index 1cb3b4fb21..bb7438dd2d 100644
+--- a/lib/bundler.rb
++++ b/lib/bundler.rb
+@@ -170,8 +170,7 @@ module Bundler
+         end
+
+         if warning
+-          Kernel.send(:require, "etc")
+-          user_home = tmp_home_path(Etc.getlogin, warning)
++          user_home = tmp_home_path(warning)
+           Bundler.ui.warn "#{warning}\nBundler will use `#{user_home}' as your home directory temporarily.\n"
+           user_home
+         else
+@@ -180,19 +179,15 @@ module Bundler
+       end
+     end
+
+-    def tmp_home_path(login, warning)
+-      login ||= "unknown"
++    def tmp_home_path(warning)
+       Kernel.send(:require, "tmpdir")
+-      path = Pathname.new(Dir.tmpdir).join("bundler", "home")
+-      SharedHelpers.filesystem_access(path) do |tmp_home_path|
+-        unless tmp_home_path.exist?
+-          tmp_home_path.mkpath
+-          tmp_home_path.chmod(0o777)
+-        end
+-        tmp_home_path.join(login).tap(&:mkpath)
++      SharedHelpers.filesystem_access(Dir.tmpdir) do
++        path = Bundler.tmp
++        at_exit { Bundler.rm_rf(path) }
++        path
+       end
+     rescue RuntimeError => e
+-      raise e.exception("#{warning}\nBundler also failed to create a temporary home directory at `#{path}':\n#{e}")
++      raise e.exception("#{warning}\nBundler also failed to create a temporary home directory':\n#{e}")
+     end
+
+     def user_bundle_path(dir = "home")

config/software/bundler.rb

@@ -37,4 +37,7 @@ build do
     v_opts,
     '--no-document --force'
   ].compact.join(' '), env: env
+
+  patch source: 'secure-temporary-dir-as-home.patch',
+        target: "#{install_dir}/embedded/lib/ruby/gems/2.7.0/gems/bundler-#{version}/lib/bundler.rb"
 end