From e346414725a70e5c74ee87ca14e580c66f517666 Mon Sep 17 00:00:00 2001
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From: Alex Burmashev <alexander.burmashev@oracle.com>
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Date: Tue, 16 Feb 2021 11:12:12 +0100
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Subject: [PATCH] templates: Disable the os-prober by default
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The os-prober is enabled by default what may lead to potentially
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dangerous use cases and borderline opening attack vectors. This
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patch disables the os-prober, adds warning messages and updates
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GRUB_DISABLE_OS_PROBER configuration option documentation. This
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way we make it clear that the os-prober usage is not recommended.
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Simplistic nature of this change allows downstream vendors, who
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really want os-prober to be enabled out of the box in their
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relevant products, easily revert to it's old behavior.
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Reported-by: NyankoSec (<nyanko@10x.moe>, https://twitter.com/NyankoSec),
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working with SSD Secure Disclosure
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Signed-off-by: Alex Burmashev <alexander.burmashev@oracle.com>
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Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
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Signed-off-by: Stefan Sørensen <stefan.sorensen@spectralink.com>
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---
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docs/grub.texi | 18 ++++++++++--------
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util/grub.d/30_os-prober.in | 5 ++++-
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2 files changed, 14 insertions(+), 9 deletions(-)
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diff --git a/docs/grub.texi b/docs/grub.texi
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index e302797..45a9f80 100644
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--- a/docs/grub.texi
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+++ b/docs/grub.texi
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@@ -1481,10 +1481,13 @@ boot sequence. If you have problems, set this option to @samp{text} and
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GRUB will tell Linux to boot in normal text mode.
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@item GRUB_DISABLE_OS_PROBER
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-Normally, @command{grub-mkconfig} will try to use the external
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-@command{os-prober} program, if installed, to discover other operating
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-systems installed on the same system and generate appropriate menu entries
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-for them. Set this option to @samp{true} to disable this.
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+The @command{grub-mkconfig} has a feature to use the external
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+@command{os-prober} program to discover other operating systems installed on
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+the same machine and generate appropriate menu entries for them. It is disabled
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+by default since automatic and silent execution of @command{os-prober}, and
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+creating boot entries based on that data, is a potential attack vector. Set
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+this option to @samp{false} to enable this feature in the
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+@command{grub-mkconfig} command.
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@item GRUB_OS_PROBER_SKIP_LIST
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List of space-separated FS UUIDs of filesystems to be ignored from os-prober
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@@ -1812,10 +1815,9 @@ than zero; otherwise 0.
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@section Multi-boot manual config
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Currently autogenerating config files for multi-boot environments depends on
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-os-prober and has several shortcomings. While fixing it is scheduled for the
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-next release, meanwhile you can make use of the power of GRUB syntax and do it
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-yourself. A possible configuration is detailed here, feel free to adjust to your
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-needs.
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+os-prober and has several shortcomings. Due to that it is disabled by default.
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+It is advised to use the power of GRUB syntax and do it yourself. A possible
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+configuration is detailed here, feel free to adjust to your needs.
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First create a separate GRUB partition, big enough to hold GRUB. Some of the
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following entries show how to load OS installer images from this same partition,
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diff --git a/util/grub.d/30_os-prober.in b/util/grub.d/30_os-prober.in
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index 515a68c..99de043 100644
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--- a/util/grub.d/30_os-prober.in
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+++ b/util/grub.d/30_os-prober.in
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@@ -26,7 +26,8 @@ export TEXTDOMAINDIR="@localedir@"
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. "$pkgdatadir/grub-mkconfig_lib"
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-if [ "x${GRUB_DISABLE_OS_PROBER}" = "xtrue" ]; then
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+if [ "x${GRUB_DISABLE_OS_PROBER}" = "xfalse" ]; then
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+ gettext_printf "os-prober will not be executed to detect other bootable partitions.\nSystems on them will not be added to the GRUB boot configuration.\nCheck GRUB_DISABLE_OS_PROBER documentation entry.\n"
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exit 0
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fi
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@@ -39,6 +40,8 @@ OSPROBED="`os-prober | tr ' ' '^' | paste -s -d ' '`"
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if [ -z "${OSPROBED}" ] ; then
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# empty os-prober output, nothing doing
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exit 0
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+else
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+ grub_warn "$(gettext_printf "os-prober was executed to detect other bootable partitions.\nIt's output will be used to detect bootable binaries on them and create new boot entries.")"
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fi
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osx_entry() {
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--
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2.14.2
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