add ld-system-preload-disable

http://forums.whonix.org/t/hardened-malloc-hardened-memory-allocator/7474/116

Thanks to @madaidan for the suggestion!

debian/control

@@ -14,7 +14,7 @@ Standards-Version: 4.3.0
 Package: helper-scripts
 Architecture: all
 Depends: sudo, python3, python3-stem, python3-scapy, python3-yaml,
- ${misc:Depends}
+ bubblewrap, ${misc:Depends}
 Replaces: anon-shared-helper-scripts, curl-scripts, anon-ws-leaktest,
  python-guimessages, python3-guimessages
 Description: Helper scripts useful for Linux Distributions
@@ -35,3 +35,7 @@ Description: Helper scripts useful for Linux Distributions
  Generic modules guimessage.py and translations.py.
  Called with two parameters: .yaml file path and yaml section. Return
  translations according to distribution local language (Python 'locale').
+ .
+ Provides the ld-system-preload-disable wrapper to disable /etc/ld.so.preload
+ per application via bubblewrap. Useful if hardened_malloc is being globally
+ preloaded and needs to be disabled for some applications.

man/ld-system-preload-disable.8.ronn

@@ -0,0 +1,28 @@
+ld-system-preload-disable(8) -- disable /etc/ld.so.preload per application
+=============================================
+
+<span class="comment">
+# Copyright (C) 2020 - 2020 ENCRYPTED SUPPORT LP <adrelanos@riseup.net>
+# See the file COPYING for copying conditions.
+</span>
+
+## SYNOPSIS
+
+ld-system-preload-disable command
+
+## DESCRIPTION
+
+Uses brwap to hide /etc/ld.so.preload from application so it will be ignored.
+
+Does not modify LD_PRELOAD environment variable.
+
+Prepend ld-system-preload-disable in front of the actual application / command
+intended to be run.
+
+## RETURN VALUES
+
+Returns what application returns.
+
+## AUTHOR
+
+This man page has been written by Patrick Schleizer (adrelanos@riseup.net).

usr/bin/ld-system-preload-disable

@@ -0,0 +1,8 @@
+#!/bin/bash
+
+## Copyright (C) 2020 - 2020 ENCRYPTED SUPPORT LP <adrelanos@riseup.net>
+## See the file COPYING for copying conditions.
+
+## This fails if file /etc/ld.so.preload does not exists.
+## bwrap: Can't create file at /etc/ld.so.preload: Permission denied
+bwrap --dev-bind / / --ro-bind /dev/null /etc/ld.so.preload "${@}"