pqcrypto/test/crypto_kem/functest.c

#include "api.h"
#include "randombytes.h"
#include <stdio.h>
#include <string.h>

#define NTESTS 10

const unsigned char canary[8] = {
    0x01, 0x23, 0x45, 0x67, 0x89, 0xAB, 0xCD, 0xEF
};

/* allocate a bit more for all keys and messages and
 * make sure it is not touched by the implementations.
 */
static void write_canary(unsigned char *d) {
    for (int i = 0; i < 8; i++) {
        d[i] = canary[i];
    }
}

static int check_canary(const unsigned char *d) {
    for (int i = 0; i < 8; i++) {
        if (d[i] != canary[i])
            return -1;
    }
    return 0;
}

// https://stackoverflow.com/a/1489985/1711232
#define PASTER(x, y) x##_##y
#define EVALUATOR(x, y) PASTER(x, y)
#define NAMESPACE(fun) EVALUATOR(PQCLEAN_NAMESPACE, fun)

#define crypto_kem_keypair NAMESPACE(crypto_kem_keypair)
#define crypto_kem_enc NAMESPACE(crypto_kem_enc)
#define crypto_kem_dec NAMESPACE(crypto_kem_dec)

#define RETURNS_ZERO(f)                           \
    if ((f) != 0) {                               \
        puts(#f " returned non-zero returncode"); \
        return -1;                                \
    }

static int test_keys(void) {
    /*
     * This is most likely going to be aligned by the compiler.
     * 16 extra bytes for canary
     * 1 extra byte for unalignment
     */
    unsigned char key_a_aligned[CRYPTO_BYTES + 16 + 1];
    unsigned char key_b_aligned[CRYPTO_BYTES + 16 + 1];
    unsigned char pk_aligned[CRYPTO_PUBLICKEYBYTES + 16 + 1];
    unsigned char sendb_aligned[CRYPTO_CIPHERTEXTBYTES + 16 + 1];
    unsigned char sk_a_aligned[CRYPTO_SECRETKEYBYTES + 16 + 1];

    /*
     * Make sure all pointers are odd.
     * This ensures that the implementation does not assume anything about the
     * data alignment. For example this would catch if an implementation
     * directly uses these pointers to load into vector registers using movdqa.
     */
    unsigned char *key_a = (unsigned char *) ((uintptr_t) key_a_aligned|(uintptr_t) 1);
    unsigned char *key_b = (unsigned char *) ((uintptr_t) key_b_aligned|(uintptr_t) 1);
    unsigned char *pk    = (unsigned char *) ((uintptr_t) pk_aligned|(uintptr_t) 1);
    unsigned char *sendb = (unsigned char *) ((uintptr_t) sendb_aligned|(uintptr_t) 1);
    unsigned char *sk_a  = (unsigned char *) ((uintptr_t) sk_a_aligned|(uintptr_t) 1);

    /*
     * Write 8 byte canary before and after the actual memory regions.
     * This is used to validate that the implementation does not assume
     * anything about the placement of data in memory
     * (e.g., assuming that the pk is always behind the sk)
     */
    write_canary(key_a);
    write_canary(key_a + CRYPTO_BYTES + 8);
    write_canary(key_b);
    write_canary(key_b + CRYPTO_BYTES + 8);
    write_canary(pk);
    write_canary(pk +  CRYPTO_PUBLICKEYBYTES + 8);
    write_canary(sendb);
    write_canary(sendb + CRYPTO_CIPHERTEXTBYTES + 8);
    write_canary(sk_a);
    write_canary(sk_a + CRYPTO_SECRETKEYBYTES + 8);

    int i;

    for (i = 0; i < NTESTS; i++) {
        // Alice generates a public key
        RETURNS_ZERO(crypto_kem_keypair(pk + 8, sk_a + 8));

        // Bob derives a secret key and creates a response
        RETURNS_ZERO(crypto_kem_enc(sendb + 8, key_b + 8, pk + 8));

        // Alice uses Bobs response to get her secret key
        RETURNS_ZERO(crypto_kem_dec(key_a + 8, sendb + 8, sk_a + 8));

        if (memcmp(key_a + 8, key_b + 8, CRYPTO_BYTES) != 0) {
            printf("ERROR KEYS\n");
            return -1;
        }

        // Validate that the implementation did not touch the canary
        if (check_canary(key_a) || check_canary(key_a + CRYPTO_BYTES + 8) ||
            check_canary(key_b) || check_canary(key_b + CRYPTO_BYTES + 8 ) ||
            check_canary(pk) || check_canary(pk + CRYPTO_PUBLICKEYBYTES + 8 ) ||
            check_canary(sendb) || check_canary(sendb + CRYPTO_CIPHERTEXTBYTES + 8 ) ||
            check_canary(sk_a) || check_canary(sk_a + CRYPTO_SECRETKEYBYTES + 8 )) {
            printf("ERROR canary overwritten\n");
            return -1;
        }
    }

    return 0;
}

static int test_invalid_sk_a(void) {
    unsigned char sk_a[CRYPTO_SECRETKEYBYTES];
    unsigned char key_a[CRYPTO_BYTES], key_b[CRYPTO_BYTES];
    unsigned char pk[CRYPTO_PUBLICKEYBYTES];
    unsigned char sendb[CRYPTO_CIPHERTEXTBYTES];
    int i;
    int returncode;

    for (i = 0; i < NTESTS; i++) {
        // Alice generates a public key
        RETURNS_ZERO(crypto_kem_keypair(pk, sk_a));

        // Bob derives a secret key and creates a response
        RETURNS_ZERO(crypto_kem_enc(sendb, key_b, pk));

        // Replace secret key with random values
        randombytes(sk_a, CRYPTO_SECRETKEYBYTES);

        // Alice uses Bobs response to get her secret key
        if ((returncode = crypto_kem_dec(key_a, sendb, sk_a)) > 0) {
            printf("ERROR failing crypto_kem_dec returned %d instead of "
                   "negative or zero code\n",
                   returncode);
            return -1;
        }

        if (!memcmp(key_a, key_b, CRYPTO_BYTES)) {
            printf("ERROR invalid sk_a\n");
            return 1;
        }
    }

    return 0;
}

static int test_invalid_ciphertext(void) {
    unsigned char sk_a[CRYPTO_SECRETKEYBYTES];
    unsigned char key_a[CRYPTO_BYTES], key_b[CRYPTO_BYTES];
    unsigned char pk[CRYPTO_PUBLICKEYBYTES];
    unsigned char sendb[CRYPTO_CIPHERTEXTBYTES];
    int i;
    size_t pos;
    int returncode;

    for (i = 0; i < NTESTS; i++) {
        randombytes((unsigned char *)&pos, sizeof(size_t));

        // Alice generates a public key
        RETURNS_ZERO(crypto_kem_keypair(pk, sk_a));

        // Bob derives a secret key and creates a response
        RETURNS_ZERO(crypto_kem_enc(sendb, key_b, pk));

        // Change some byte in the ciphertext (i.e., encapsulated key)
        sendb[pos % CRYPTO_CIPHERTEXTBYTES] ^= 23;

        // Alice uses Bobs response to get her secret key
        if ((returncode = crypto_kem_dec(key_a, sendb, sk_a)) > 0) {
            printf("ERROR crypto_kem_dec should either fail (negative "
                   "returncode) or succeed (return 0) but returned %d\n",
                   returncode);
            return -1;
        }

        if (!memcmp(key_a, key_b, CRYPTO_BYTES)) {
            printf("ERROR invalid ciphertext\n");
            return 1;
        }
    }

    return 0;
}

int main(void) {
    int result = 0;
    result += test_keys();
    result += test_invalid_sk_a();
    result += test_invalid_ciphertext();

    if (result != 0) {
        puts("Errors occurred");
    }
    return result;
}