Implement CoreOS compatibility mode (#84)

* Add special CoreOS compatibility mode
* CoreOS: refuse --coreos if we're not under CoreOS
* CoreOS: warn if launched without --coreos option
* is_coreos: make stderr silent
* CoreOS: tiny adjustments
This commit is contained in:
Stéphane Lesimple 2018-01-16 10:33:01 +01:00 committed by GitHub
parent bd18323d79
commit 7a88aec95f
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@ -24,7 +24,7 @@ show_usage()
To run under this mode, just start the script without any option (you can also use --live explicitly)
Second mode is the "offline" mode, where you can inspect a non-running kernel.
You'll need to specify the location of the vmlinux file, and if possible, the corresponding config and System.map files:
You'll need to specify the location of the vmlinux file, config and System.map files:
--kernel vmlinux_file Specify a (possibly compressed) vmlinux file
--config kernel_config Specify a kernel config file
@ -34,12 +34,15 @@ show_usage()
--no-color Don't use color codes
--verbose, -v Increase verbosity level
--no-sysfs Don't use the /sys interface even if present
--coreos Special mode for CoreOS (use an ephemeral toolbox to inspect kernel)
--batch text Produce machine readable output, this is the default if --batch is specified alone
--batch json Produce JSON output formatted for Puppet, Ansible, Chef...
--batch nrpe Produce machine readable output formatted for NRPE
--variant [1,2,3] Specify which variant you'd like to check, by default all variants are checked
Can be specified multiple times (e.g. --variant 2 --variant 3)
Return codes:
0 (not vulnerable), 2 (vulnerable), 3 (unknown), 255 (error)
IMPORTANT:
A false sense of security is worse than no security at all.
@ -88,6 +91,7 @@ opt_variant2=0
opt_variant3=0
opt_allvariants=1
opt_no_sysfs=0
opt_coreos=0
global_critical=0
global_unknown=0
@ -269,6 +273,13 @@ while [ -n "$1" ]; do
elif [ "$1" = "--no-sysfs" ]; then
opt_no_sysfs=1
shift
elif [ "$1" = "--coreos" ]; then
opt_coreos=1
shift
elif [ "$1" = "--coreos-within-toolbox" ]; then
# don't use directly: used internally by --coreos
opt_coreos=0
shift
elif [ "$1" = "--batch" ]; then
opt_batch=1
opt_verbose=0
@ -461,6 +472,58 @@ extract_vmlinux()
# end of extract-vmlinux functions
mount_debugfs()
{
if [ ! -e /sys/kernel/debug/sched_features ]; then
# try to mount the debugfs hierarchy ourselves and remember it to umount afterwards
mount -t debugfs debugfs /sys/kernel/debug 2>/dev/null && mounted_debugfs=1
fi
}
umount_debugfs()
{
if [ "$mounted_debugfs" = 1 ]; then
# umount debugfs if we did mount it ourselves
umount /sys/kernel/debug
fi
}
load_msr()
{
modprobe msr 2>/dev/null && insmod_msr=1
_debug "attempted to load module msr, insmod_msr=$insmod_msr"
}
unload_msr()
{
if [ "$insmod_msr" = 1 ]; then
# if we used modprobe ourselves, rmmod the module
rmmod msr 2>/dev/null
_debug "attempted to unload module msr, ret=$?"
fi
}
load_cpuid()
{
modprobe cpuid 2>/dev/null && insmod_cpuid=1
_debug "attempted to load module cpuid, insmod_cpuid=$insmod_cpuid"
}
unload_cpuid()
{
if [ "$insmod_cpuid" = 1 ]; then
# if we used modprobe ourselves, rmmod the module
rmmod cpuid 2>/dev/null
_debug "attempted to unload module cpuid, ret=$?"
fi
}
is_coreos()
{
which coreos-install >/dev/null 2>&1 && which toolbox >/dev/null 2>&1 && return 0
return 1
}
# check for mode selection inconsistency
if [ "$opt_live_explicit" = 1 ]; then
if [ -n "$opt_kernel" -o -n "$opt_config" -o -n "$opt_map" ]; then
@ -470,6 +533,29 @@ if [ "$opt_live_explicit" = 1 ]; then
fi
fi
# coreos mode
if [ "$opt_coreos" = 1 ]; then
if ! is_coreos; then
_warn "CoreOS mode asked, but we're not under CoreOS!"
exit 255
fi
_warn "CoreOS mode, starting an ephemeral toolbox to launch the script"
load_msr
load_cpuid
mount_debugfs
toolbox --ephemeral --bind-ro /dev/cpu:/dev/cpu -- sh -c "dnf install -y binutils curl which && /media/root$PWD/$0 $@ --coreos-within-toolbox"
exitcode=$?
mount_debugfs
unload_cpuid
unload_msr
exit $exitcode
else
if is_coreos; then
_warn "You seem to be running CoreOS, you might want to use the --coreos option for better results"
_warn
fi
fi
# root check (only for live mode, for offline mode, we already checked if we could read the files)
if [ "$opt_live" = 1 ]; then
@ -490,6 +576,8 @@ if [ "$opt_live" = 1 ]; then
# if we have a dedicated /boot partition, our bootloader might have just called it /
# so try to prepend /boot and see if we find anything
[ -e "/boot/$opt_kernel" ] && opt_kernel="/boot/$opt_kernel"
# special case for CoreOS if we're inside the toolbox
[ -e "/media/root/boot/$opt_kernel" ] && opt_kernel="/media/root/boot/$opt_kernel"
_debug "opt_kernel is now $opt_kernel"
# else, the full path is already there (most probably /boot/something)
fi
@ -551,11 +639,13 @@ fi
if [ -e "$opt_kernel" ]; then
if ! which readelf >/dev/null 2>&1; then
_debug "readelf not found"
vmlinux_err="missing 'readelf' tool, please install it, usually it's in the 'binutils' package"
else
extract_vmlinux "$opt_kernel"
fi
else
_debug "no opt_kernel defined"
vmlinux_err="couldn't find your kernel image in /boot, if you used netboot, this is normal"
fi
if [ -z "$vmlinux" -o ! -r "$vmlinux" ]; then
@ -569,22 +659,6 @@ _info
# now we define some util functions and the check_*() funcs, as
# the user can choose to execute only some of those
mount_debugfs()
{
if [ ! -e /sys/kernel/debug/sched_features ]; then
# try to mount the debugfs hierarchy ourselves and remember it to umount afterwards
mount -t debugfs debugfs /sys/kernel/debug 2>/dev/null && mounted_debugfs=1
fi
}
umount_debugfs()
{
if [ "$mounted_debugfs" = 1 ]; then
# umount debugfs if we did mount it ourselves
umount /sys/kernel/debug
fi
}
sys_interface_check()
{
[ "$opt_live" = 1 -a "$opt_no_sysfs" = 0 -a -r "$1" ] || return 1
@ -683,8 +757,7 @@ check_variant2()
_info_nol "* The SPEC_CTRL MSR is available: "
if [ ! -e /dev/cpu/0/msr ]; then
# try to load the module ourselves (and remember it so we can rmmod it afterwards)
modprobe msr 2>/dev/null && insmod_msr=1
_debug "attempted to load module msr, insmod_msr=$insmod_msr"
load_msr
fi
if [ ! -e /dev/cpu/0/msr ]; then
pstatus yellow UNKNOWN "couldn't read /dev/cpu/0/msr, is msr support enabled in your kernel?"
@ -700,18 +773,13 @@ check_variant2()
fi
fi
if [ "$insmod_msr" = 1 ]; then
# if we used modprobe ourselves, rmmod the module
rmmod msr 2>/dev/null
_debug "attempted to unload module msr, ret=$?"
fi
unload_msr
# CPUID test
_info_nol "* The SPEC_CTRL CPUID feature bit is set: "
if [ ! -e /dev/cpu/0/cpuid ]; then
# try to load the module ourselves (and remember it so we can rmmod it afterwards)
modprobe cpuid 2>/dev/null && insmod_cpuid=1
_debug "attempted to load module cpuid, insmod_cpuid=$insmod_cpuid"
load_cpuid
fi
if [ ! -e /dev/cpu/0/cpuid ]; then
pstatus yellow UNKNOWN "couldn't read /dev/cpu/0/cpuidr, is cpuid support enabled in your kernel?"
@ -734,6 +802,7 @@ check_variant2()
pstatus red NO
fi
fi
unload_cpuid
# hardware support according to kernel
if [ "$opt_verbose" -ge 2 ]; then