v0.01
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Stéphane Lesimple
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README.md
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README.md
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# spectre-meltdown-checker
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Spectre & Meltdown vulnerability/mitigation checker for Linux
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Spectre & Meltdown Checker
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==========================
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A simple shell script to tell if your Linux installation is vulnerable
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against the 3 "speculative execution" CVEs:
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CVE-2017-5753 bounds check bypass (Spectre Variant 1)
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Impact: Kernel & all software
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Mitigation: recompile software *and* kernel with a modified compiler that introduces the LFENCE opcode at the proper positions in the resulting code
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Performance impact of the mitigation: negligible
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CVE-2017-5715: branch target injection (Spectre Variant 2)
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Impact: Kernel
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Mitigation 1: new opcode via microcode update that should be used by up to date compilers to protect the BTB (by flushing indirect branch predictors)
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Mitigation 2: introducing "retpoline" into compilers, and recompile software/OS with it
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Performance impact of the mitigation: high for mitigation 1, medium for mitigation 2, depending on your CPU
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CVE-2017-5754: rogue data cache load (Meltdown)
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Impact: Kernel
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Mitigation: updated kernel (with PTI/KPTI patches), updating the kernel is enough
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Performance impact of the mitigation: low to medium
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Example of the output of the script:
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Spectre and Meltdown mitigation detection tool v0.01
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CVE-2017-5753 [bounds check bypass] aka 'Spectre Variant 1'
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* Kernel recompiled with LFENCE opcode insertion: UNKNOWN (check not yet implemented)
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> STATUS: UNKNOWN (not implemented, but real answer is most probably VULNERABLE at this stage)
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CVE-2017-5715 [branch target injection] aka 'Spectre Variant 2'
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* Mitigation 1
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* Hardware (CPU microcode) support for mitigation: NO
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* Kernel support for IBRS: NO
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* IBRS enabled for Kernel space: NO
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* IBRS enabled for User space: NO
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* Mitigation 2
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* Kernel recompiled with retpoline: UNKNOWN (check not yet implemented)
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> STATUS: VULNERABLE (IBRS hardware + kernel support OR retpoline-compiled kernel are needed to mitigate the vulnerability)
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CVE-2017-5754 [rogue data cache load] aka 'Meltdown' aka 'Variant 3'
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* Kernel supports Page Table Isolation (PTI): YES
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* PTI enabled and active: YES
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> STATUS: NOT VULNERABLE (PTI mitigates the vulnerability)
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#! /bin/sh
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# Spectre & Meltdown checker
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# Stephane Lesimple, v0.00.01
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VERSION=0.01
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pstatus()
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{
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case "$1" in
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red) col="\033[101m\033[30m";;
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green) col="\033[102m\033[30m";;
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yellow) col="\033[103m\033[30m";;
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*) col="";;
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esac
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echo -n "$col$2\033[0m"
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[ -n "$3" ] && echo -n " ($3)"
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echo
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}
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echo "Spectre and Meltdown mitigation detection tool v$VERSION"
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echo
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# SPECTRE 1
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echo "\033[1;34mCVE-2017-5753 [bounds check bypass] aka 'Spectre Variant 1'\033[0m"
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echo -n "* Kernel recompiled with LFENCE opcode insertion: "
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pstatus yellow UNKNOWN "check not yet implemented"
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echo -n "> \033[46m\033[30mSTATUS:\033[0m "
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pstatus yellow UNKNOWN "not implemented, but real answer is most probably VULNERABLE at this stage"
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# VARIANT 2
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echo
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echo "\033[1;34mCVE-2017-5715 [branch target injection] aka 'Spectre Variant 2'\033[0m"
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echo "* Mitigation 1"
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echo -n "* Hardware (CPU microcode) support for mitigation: "
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if [ ! -e /dev/cpu/0/msr ]; then
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modprobe msr 2>/dev/null && insmod_msr=1
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fi
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if [ ! -e /dev/cpu/0/msr ]; then
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pstatus yellow UNKNOWN "couldn't read /dev/cpu/0/msr, is msr support enabled in your kernel?"
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else
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dd if=/dev/cpu/0/msr of=/dev/null bs=1 count=8 skip=72 2>/dev/null
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if [ $? -eq 0 ]; then
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pstatus green YES
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else
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pstatus red NO
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fi
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#dd if=/dev/cpu/0/msr of=/dev/null bs=1 count=8 skip=73 2>/dev/null
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#echo $?
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fi
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if [ "$insmod_msr" = 1 ]; then
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rmmod msr 2>/dev/null
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fi
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echo -n "* Kernel support for IBRS: "
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if [ -e /sys/kernel/debug/sched_features ]; then
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mount -t debugfs debugfs /sys/kernel/debug 2>/dev/null && mounted_debugfs=1
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fi
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if [ -e /sys/kernel/debug/ibrs_enabled ]; then
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pstatus green YES
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ibrs_supported=1
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else
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pstatus red NO
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fi
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ibrs_enabled=$(cat /sys/kernel/debug/ibrs_enabled 2>/dev/null)
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echo -n "* IBRS enabled for Kernel space: "
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case "$ibrs_enabled" in
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"") [ "$ibrs_supported" = 1 ] && pstatus yellow UNKNOWN || pstatus red NO;;
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0) pstatus red NO;;
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1 | 2) pstatus green YES;;
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*) pstatus yellow UNKNOWN;;
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esac
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echo -n "* IBRS enabled for User space: "
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case "$ibrs_enabled" in
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"") [ "$ibrs_supported" = 1 ] && pstatus yellow UNKNOWN || pstatus red NO;;
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0 | 1) pstatus red NO;;
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2) pstatus green YES;;
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*) pstatus yellow unknown;;
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esac
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if [ "$mounted_debugfs" = 1 ]; then
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umount /sys/kernel/debug
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fi
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echo "* Mitigation 2"
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echo -n "* Kernel recompiled with retpoline: "
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pstatus yellow UNKNOWN "check not yet implemented"
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echo -n "> \033[46m\033[30mSTATUS:\033[0m "
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if grep -q AMD /proc/cpuinfo; then
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pstatus green "NOT VULNERABLE" "your CPU is not vulnerable as per the vendor"
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elif [ "$ibrs_enabled" = 1 -o "$ibrs_enabled" = 2 ]; then
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pstatus green "NOT VULNERABLE" "IBRS mitigates the vulnerability"
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else
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pstatus red VULNERABLE "IBRS hardware + kernel support OR retpoline-compiled kernel are needed to mitigate the vulnerability"
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fi
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# MELTDOWN
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echo
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echo "\033[1;34mCVE-2017-5754 [rogue data cache load] aka 'Meltdown' aka 'Variant 3'\033[0m"
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echo -n "* Kernel supports Page Table Isolation (PTI): "
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if [ -e /proc/config.gz ]; then
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if zgrep -q '^CONFIG_PAGE_TABLE_ISOLATION=y' /proc/config.gz; then
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pstatus green YES
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kpti_support=1
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else
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pstatus red NO
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fi
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elif [ -e /boot/config-$(uname -r) ]; then
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if grep -q '^CONFIG_PAGE_TABLE_ISOLATION=y' /boot/config-$(uname -r); then
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pstatus green YES
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kpti_support=1
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else
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pstatus red NO
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fi
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else
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pstatus yellow UNKNOWN
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fi
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echo -n "* PTI enabled and active: "
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if grep ^flags /proc/cpuinfo | grep -qw pti; then
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pstatus green YES
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kpti_enabled=1
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elif dmesg | grep -q 'Kernel/User page tables isolation: enabled'; then
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pstatus green YES
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kpti_enabled=1
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else
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pstatus red NO
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fi
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echo -n "> \033[46m\033[30mSTATUS:\033[0m "
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if grep -q AMD /proc/cpuinfo; then
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pstatus green "NOT VULNERABLE" "your CPU is not vulnerable as per the vendor"
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elif [ "$kpti_enabled" = 1 ]; then
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pstatus green "NOT VULNERABLE" "PTI mitigates the vulnerability"
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else
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pstatus red "VULNERABLE" "PTI is needed to mitigate the vulnerability"
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fi
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echo
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if [ "$USER" != root ]; then
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echo "Note that you should launch this script with root privileges to get accurate information"
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echo "You can try the following command: sudo $0"
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fi
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