99 lines
4.2 KiB
Diff
99 lines
4.2 KiB
Diff
From ba4d612892bf6e3aae9cca7edce2a6d6b43e3e22 Mon Sep 17 00:00:00 2001
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From: Sean Parkinson <sean@wolfssl.com>
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Date: Wed, 17 Jul 2019 08:26:02 +1000
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Subject: [PATCH] Improve nonce use in ECC mulmod
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(cherry picked from commit 483f6a5acd9808b405306661c121aa6407464dc2)
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--- a/wolfcrypt/src/ecc.c
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+++ b/wolfcrypt/src/ecc.c
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@@ -2039,7 +2039,7 @@ int wc_ecc_mulmod_ex(mp_int* k, ecc_poin
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#define M_POINTS 8
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int first = 1, bitbuf = 0, bitcpy = 0, j;
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#else
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- #define M_POINTS 3
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+ #define M_POINTS 4
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#endif
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ecc_point *tG, *M[M_POINTS];
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@@ -2253,7 +2253,9 @@ int wc_ecc_mulmod_ex(mp_int* k, ecc_poin
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mode = 0;
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bitcnt = 1;
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buf = 0;
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- digidx = get_digit_count(k) - 1;
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+ digidx = get_digit_count(modulus) - 1;
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+ /* The order MAY be 1 bit longer than the modulus. */
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+ digidx += (modulus->dp[digidx] >> (DIGIT_BIT-1));
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/* perform ops */
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if (err == MP_OKAY) {
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@@ -2272,25 +2274,53 @@ int wc_ecc_mulmod_ex(mp_int* k, ecc_poin
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i = (buf >> (DIGIT_BIT - 1)) & 1;
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buf <<= 1;
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- if (mode == 0 && i == 0) {
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+ if (mode == 0) {
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+ mode = i;
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/* timing resistant - dummy operations */
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if (err == MP_OKAY)
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- err = ecc_projective_add_point(M[0], M[1], M[2], a, modulus,
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+ err = ecc_projective_add_point(M[1], M[2], M[2], a, modulus,
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mp);
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+#ifdef WC_NO_CACHE_RESISTANT
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if (err == MP_OKAY)
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- err = ecc_projective_dbl_point(M[1], M[2], a, modulus, mp);
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- if (err == MP_OKAY)
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- continue;
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- }
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-
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- if (mode == 0 && i == 1) {
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- mode = 1;
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- /* timing resistant - dummy operations */
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- if (err == MP_OKAY)
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- err = ecc_projective_add_point(M[0], M[1], M[2], a, modulus,
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- mp);
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- if (err == MP_OKAY)
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- err = ecc_projective_dbl_point(M[1], M[2], a, modulus, mp);
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+ err = ecc_projective_dbl_point(M[2], M[3], a, modulus, mp);
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+#else
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+ /* instead of using M[i] for double, which leaks key bit to cache
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+ * monitor, use M[2] as temp, make sure address calc is constant,
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+ * keep M[0] and M[1] in cache */
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+ if (err == MP_OKAY)
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+ err = mp_copy((mp_int*)
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+ ( ((wolfssl_word)M[0]->x & wc_off_on_addr[i^1]) +
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+ ((wolfssl_word)M[1]->x & wc_off_on_addr[i])),
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+ M[2]->x);
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+ if (err == MP_OKAY)
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+ err = mp_copy((mp_int*)
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+ ( ((wolfssl_word)M[0]->y & wc_off_on_addr[i^1]) +
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+ ((wolfssl_word)M[1]->y & wc_off_on_addr[i])),
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+ M[2]->y);
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+ if (err == MP_OKAY)
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+ err = mp_copy((mp_int*)
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+ ( ((wolfssl_word)M[0]->z & wc_off_on_addr[i^1]) +
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+ ((wolfssl_word)M[1]->z & wc_off_on_addr[i])),
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+ M[2]->z);
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+ if (err == MP_OKAY)
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+ err = ecc_projective_dbl_point(M[2], M[3], a, modulus, mp);
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+ /* copy M[2] back to M[i] */
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+ if (err == MP_OKAY)
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+ err = mp_copy(M[2]->x,
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+ (mp_int*)
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+ ( ((wolfssl_word)M[0]->x & wc_off_on_addr[i^1]) +
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+ ((wolfssl_word)M[1]->x & wc_off_on_addr[i])) );
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+ if (err == MP_OKAY)
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+ err = mp_copy(M[2]->y,
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+ (mp_int*)
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+ ( ((wolfssl_word)M[0]->y & wc_off_on_addr[i^1]) +
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+ ((wolfssl_word)M[1]->y & wc_off_on_addr[i])) );
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+ if (err == MP_OKAY)
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+ err = mp_copy(M[2]->z,
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+ (mp_int*)
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+ ( ((wolfssl_word)M[0]->z & wc_off_on_addr[i^1]) +
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+ ((wolfssl_word)M[1]->z & wc_off_on_addr[i])) );
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+#endif
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if (err == MP_OKAY)
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continue;
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}
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