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ECC, TFM: constant time point arithmetic, signing and modexp #12109

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ECC, TFM: constant time point arithmetic, signing and modexp #12109

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63 changes: 63 additions & 0 deletions tests/api/test_wolfmath.c
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Original file line number Diff line number Diff line change
Expand Up @@ -217,6 +217,69 @@ int test_mp_exptmod_even_2k(void)
return EXPECT_RESULT();
}

/*
* Testing TFM exponentiation with a modulus of FP_SIZE / 2 digits - the largest
* accepted. Constant time exponentiation keeps working values at the length of
* the modulus so products use all FP_SIZE digits.
*/
int test_mp_exptmod_fp_size_boundary(void)
{
EXPECT_DECLS;
#if defined(USE_FAST_MATH) && defined(WOLFSSL_PUBLIC_MP) && \
defined(TFM_TIMING_RESISTANT) && !defined(WC_NO_MODEXP_TIMING_RESISTANT)
mp_int g, x, p, y, e;
int k = (FP_SIZE / 2) * DIGIT_BIT;

XMEMSET(&g, 0, sizeof(g));
XMEMSET(&x, 0, sizeof(x));
XMEMSET(&p, 0, sizeof(p));
XMEMSET(&y, 0, sizeof(y));
XMEMSET(&e, 0, sizeof(e));
ExpectIntEQ(mp_init_multi(&g, &x, &p, &y, &e, NULL), MP_OKAY);

/* p = 2^k - 1: odd and all FP_SIZE / 2 digits set. */
ExpectIntEQ(mp_set(&p, 1), MP_OKAY);
ExpectIntEQ(mp_mul_2d(&p, k, &p), MP_OKAY);
ExpectIntEQ(mp_sub_d(&p, 1, &p), MP_OKAY);
ExpectIntEQ(p.used, FP_SIZE / 2);

/* Base 2: 2^(k.2^64 + 7) mod (2^k - 1) = 2^7 as 2^k = 1 mod p. */
ExpectIntEQ(mp_set(&g, 2), MP_OKAY);
ExpectIntEQ(mp_set_int(&x, (unsigned long)k), MP_OKAY);
ExpectIntEQ(mp_mul_2d(&x, 64, &x), MP_OKAY);
ExpectIntEQ(mp_add_d(&x, 7, &x), MP_OKAY);
ExpectIntEQ(mp_exptmod(&g, &x, &p, &y), MP_OKAY);
ExpectIntEQ(mp_cmp_d(&y, 128), MP_EQ);

/* General base: (p - 1)^x mod p = p - 1 when x odd and 1 when x even.
* Full width base and exponent. */
ExpectIntEQ(mp_sub_d(&p, 1, &g), MP_OKAY);
ExpectIntEQ(mp_sub_d(&p, 2, &x), MP_OKAY);
ExpectIntEQ(mp_exptmod(&g, &x, &p, &y), MP_OKAY);
ExpectIntEQ(mp_cmp(&y, &g), MP_EQ);
ExpectIntEQ(mp_sub_d(&p, 3, &x), MP_OKAY);
ExpectIntEQ(mp_exptmod(&g, &x, &p, &y), MP_OKAY);
ExpectIntEQ(mp_cmp_d(&y, 1), MP_EQ);

/* Exponent processed as a fixed number of digits. */
ExpectIntEQ(mp_sub_d(&p, 2, &x), MP_OKAY);
ExpectIntEQ(mp_exptmod_ex(&g, &x, x.used, &p, &y), MP_OKAY);
ExpectIntEQ(mp_cmp(&y, &g), MP_EQ);

/* One digit more than the boundary is rejected. */
ExpectIntEQ(mp_mul_2d(&p, DIGIT_BIT, &e), MP_OKAY);
ExpectIntEQ(mp_add_d(&e, 1, &e), MP_OKAY);
ExpectIntEQ(mp_exptmod(&g, &x, &e, &y), WC_NO_ERR_TRACE(MP_VAL));

mp_clear(&g);
mp_clear(&x);
mp_clear(&p);
mp_clear(&y);
mp_clear(&e);
#endif
return EXPECT_RESULT();
}

/*
* Testing wc_export_int
*/
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2 changes: 2 additions & 0 deletions tests/api/test_wolfmath.h
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Original file line number Diff line number Diff line change
Expand Up @@ -30,6 +30,7 @@ int test_mp_get_rand_digit(void);
int test_mp_cond_copy(void);
int test_mp_rand(void);
int test_mp_exptmod_even_2k(void);
int test_mp_exptmod_fp_size_boundary(void);
int test_wc_export_int(void);
int test_wc_SpIntSizeDecisionCoverage(void);
int test_wc_SpIntShiftDecisionCoverage(void);
Expand All @@ -45,6 +46,7 @@ int test_wc_SpIntExptGcdDecisionCoverage(void);
TEST_DECL_GROUP("wolfmath", test_mp_cond_copy), \
TEST_DECL_GROUP("wolfmath", test_mp_rand), \
TEST_DECL_GROUP("wolfmath", test_mp_exptmod_even_2k), \
TEST_DECL_GROUP("wolfmath", test_mp_exptmod_fp_size_boundary), \
TEST_DECL_GROUP("wolfmath", test_wc_export_int), \
TEST_DECL_GROUP("wolfmath", test_wc_SpIntSizeDecisionCoverage), \
TEST_DECL_GROUP("wolfmath", test_wc_SpIntShiftDecisionCoverage), \
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18 changes: 9 additions & 9 deletions tests/unit-mcdc/test_ecc_fault_whitebox.c
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Original file line number Diff line number Diff line change
Expand Up @@ -794,38 +794,38 @@ static void wb_degenerate_points(void)
wb_fail = 1;
goto out;
}
(void)_ecc_projective_add_point(P, Q, R, &a, &prime, mp);
(void)_ecc_projective_add_point(P, Q, R, &a, &prime, mp, 0);

/* Q = -P: x and z equal, y differs -> the general add gives Z == 0 */
(void)mp_sub(&prime, P->y, Q->y);
(void)_ecc_projective_add_point(P, Q, R, &a, &prime, mp);
(void)_ecc_projective_add_point(P, Q, R, &a, &prime, mp, 0);

/* Q->z == 0: the digit-count operand FALSE with x still equal */
(void)wc_ecc_copy_point(P, Q);
(void)mp_set(Q->z, 0);
(void)_ecc_projective_add_point(P, Q, R, &a, &prime, mp);
(void)_ecc_projective_add_point(P, Q, R, &a, &prime, mp, 0);

/* Q->z differs (non-zero): the z comparison FALSE */
(void)mp_set(Q->z, 2);
(void)_ecc_projective_add_point(P, Q, R, &a, &prime, mp);
(void)_ecc_projective_add_point(P, Q, R, &a, &prime, mp, 0);

/* Q->x differs: the first operand FALSE */
(void)wc_ecc_copy_point(P, Q);
(void)mp_set(Q->x, 3);
(void)_ecc_projective_add_point(P, Q, R, &a, &prime, mp);
(void)_ecc_projective_add_point(P, Q, R, &a, &prime, mp, 0);

/* y differs and Q is not -P either: the last operand FALSE */
(void)wc_ecc_copy_point(P, Q);
(void)mp_set(Q->y, 5);
(void)_ecc_projective_add_point(P, Q, R, &a, &prime, mp);
(void)_ecc_projective_add_point(P, Q, R, &a, &prime, mp, 0);

/* curve coefficient zero -> "modulus - a is zero" TRUE in the doubling
* formula's coefficient selection; the real a gives the FALSE row. */
(void)_ecc_projective_dbl_point(P, R, &zero, &prime, mp);
(void)_ecc_projective_dbl_point(P, R, &a, &prime, mp);
(void)_ecc_projective_dbl_point(P, R, &zero, &prime, mp, 0);
(void)_ecc_projective_dbl_point(P, R, &a, &prime, mp, 0);
for (n = 1; n <= 10; n++) {
mcdc_fm_arm(n);
(void)_ecc_projective_dbl_point(P, R, &zero, &prime, mp);
(void)_ecc_projective_dbl_point(P, R, &zero, &prime, mp, 0);
mcdc_fm_disarm();
}

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