security-misc/etc/default/grub.d/40_kernel_hardening.cfg
2021-08-22 05:23:24 -04:00

74 lines
3.1 KiB
INI

## Copyright (C) 2019 - 2021 ENCRYPTED SUPPORT LP <adrelanos@whonix.org>
## See the file COPYING for copying conditions.
kpkg="linux-image-$(dpkg --print-architecture)" || true
kver="$(dpkg-query --show --showformat='${Version}' "$kpkg")" 2>/dev/null || true
#echo "## kver: $kver"
## Disables the merging of slabs of similar sizes.
## Sometimes a slab can be used in a vulnerable way which an attacker can exploit.
GRUB_CMDLINE_LINUX="$GRUB_CMDLINE_LINUX slab_nomerge"
if dpkg --compare-versions "$kver" ge "5.3"; then
## Enables sanity checks (F) and redzoning (Z).
GRUB_CMDLINE_LINUX="$GRUB_CMDLINE_LINUX slub_debug=FZ"
#echo "## $kver grater or equal 5.3: yes"
## Zero memory at allocation and free time.
GRUB_CMDLINE_LINUX="$GRUB_CMDLINE_LINUX init_on_alloc=1 init_on_free=1"
else
#echo "## $kver grater or equal 5.3: no"
## SLUB poisoning and page poisoning is used if the kernel
## does not yet support init_on_{,alloc,free}.
GRUB_CMDLINE_LINUX="$GRUB_CMDLINE_LINUX slub_debug=FZP"
if command -v "qubesdb-read" >/dev/null 2>&1 ; then
## https://github.com/QubesOS/qubes-issues/issues/5212#issuecomment-533873012
true "skip adding page_poison=1 in Qubes"
else
GRUB_CMDLINE_LINUX="$GRUB_CMDLINE_LINUX page_poison=1"
fi
fi
## Makes the kernel panic on uncorrectable errors in ECC memory that an attacker could exploit.
GRUB_CMDLINE_LINUX="$GRUB_CMDLINE_LINUX mce=0"
## Enables Kernel Page Table Isolation which mitigates Meltdown and improves KASLR.
GRUB_CMDLINE_LINUX="$GRUB_CMDLINE_LINUX pti=on"
## Vsyscalls are obsolete, are at fixed addresses and are a target for ROP.
GRUB_CMDLINE_LINUX="$GRUB_CMDLINE_LINUX vsyscall=none"
## Enables page allocator freelist randomization.
if dpkg --compare-versions "${kver}" ge "5.2"; then
GRUB_CMDLINE_LINUX="$GRUB_CMDLINE_LINUX page_alloc.shuffle=1"
fi
## Enables kernel lockdown.
##
## Disabled for now as it enforces module signature verification which breaks
## too many things.
## https://forums.whonix.org/t/enforce-kernel-module-software-signature-verification-module-signing-disallow-kernel-module-loading-by-default/7880
##
#if dpkg --compare-versions "${kver}" ge "5.4"; then
# GRUB_CMDLINE_LINUX="$GRUB_CMDLINE_LINUX lockdown=confidentiality"
#fi
## Gather more entropy during boot.
##
## Requires linux-hardened kernel patch.
## https://github.com/anthraxx/linux-hardened
GRUB_CMDLINE_LINUX="$GRUB_CMDLINE_LINUX extra_latent_entropy"
## Prevent kernel info leaks in console during boot.
## https://phabricator.whonix.org/T950
## LANG=C str_replace is provided by package helper-scripts.
## Remove "quiet" from GRUB_CMDLINE_LINUX_DEFAULT because "quiet" must be first.
GRUB_CMDLINE_LINUX_DEFAULT="$(echo "$GRUB_CMDLINE_LINUX_DEFAULT" | LANG=C str_replace "quiet" "")"
GRUB_CMDLINE_LINUX="$GRUB_CMDLINE_LINUX quiet loglevel=0"
## Restrict access to debugfs since it can contain a lot of sensitive information.
## https://lkml.org/lkml/2020/7/16/122
## https://github.com/torvalds/linux/blob/fb1201aececc59990b75ef59fca93ae4aa1e1444/Documentation/admin-guide/kernel-parameters.txt#L835-L848
GRUB_CMDLINE_LINUX="$GRUB_CMDLINE_LINUX debugfs=off"