Restrict /proc/cpuinfo, /proc/bus, /proc/scsi and /sys to root

debian/control

@@ -84,6 +84,13 @@ Description: enhances misc security settings
   * Bluetooth is blacklisted to reduce attack surface. Bluetooth also has
  a history of security concerns.
  https://en.wikipedia.org/wiki/Bluetooth#History_of_security_concerns
+ .
+  * A systemd service restricts /proc/cpuinfo, /proc/bus, /proc/scsi and
+ /sys to the root user only. This hides a lot of hardware identifiers from
+ unprivileged users and increases security as /sys exposes a lot of information
+ that shouldn't be accessible to unprivileged users. As this will break many
+ things, it is disabled by default and can optionally be enabled by running
+ `systemctl enable hide-hardware-info.service` as root.
  .
  Uncommon network protocols are blacklisted:
  These are rarely used and may have unknown vulnerabilities.

lib/systemd/system-preset/50-security-misc.preset

@@ -0,0 +1,4 @@
+## Copyright (C) 2012 - 2018 ENCRYPTED SUPPORT LP <adrelanos@riseup.net>
+## See the file COPYING for copying conditions.
+
+disable hide-hardware-info.service

lib/systemd/system/hide-hardware-info.service

@@ -0,0 +1,17 @@
+## Copyright (C) 2012 - 2018 ENCRYPTED SUPPORT LP <adrelanos@riseup.net>
+## See the file COPYING for copying conditions.
+
+[Unit]
+Description=Hide hardware information to unprivileged users
+Documentation=https://github.com/Whonix/security-misc
+DefaultDependencies=no
+Before=sysinit.target
+Requires=local-fs.target
+After=local-fs.target
+
+[Service]
+Type=oneshot
+ExecStart=/usr/lib/security-misc/hide-hardware-info
+
+[Install]
+WantedBy=sysinit.target

usr/lib/security-misc/hide-hardware-info

@@ -0,0 +1,24 @@
+#!/bin/bash
+
+## Copyright (C) 2012 - 2018 ENCRYPTED SUPPORT LP <adrelanos@riseup.net>
+## See the file COPYING for copying conditions.
+
+## sysfs and debugfs expose a lot of information
+## that should not be accessible by an unprivileged
+## user which includes hardware info, debug info and
+## more. This restricts /sys, /proc/cpuinfo, /proc/bus
+## and /proc/scsi to the root user only. This hides
+## many hardware identifiers from ordinary users
+## and increases security.
+for i in /proc/cpuinfo /proc/bus /proc/scsi /sys
+do
+  if [ -e "${i}" ]; then
+    chmod og-rwx "${i}"
+  else
+    ## /proc/scsi doesn't exist on Debian so errors
+    ## are expected here.
+    if ! [ "${i}" = "/proc/scsi" ]; then
+      echo "ERROR: ${i} could not be found."
+    fi
+  fi
+done