diff options
author | Billy Brumley <bbrumley@gmail.com> | 2018-06-20 10:56:37 +0300 |
---|---|---|
committer | Richard Levitte <levitte@openssl.org> | 2018-06-21 13:33:42 +0200 |
commit | a766aab93a282774e63ba918d0bb1c6680a5f292 (patch) | |
tree | 60a0658c4ad8129af5866de1606c91ebb8ff7597 /crypto/ec/ec_mult.c | |
parent | 27232cc3385260311e7fd2f6cd78db967cae650d (diff) |
[crypto/ec] don't assume points are of order group->order
Reviewed-by: Paul Dale <paul.dale@oracle.com>
Reviewed-by: Richard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/6535)
Diffstat (limited to 'crypto/ec/ec_mult.c')
-rw-r--r-- | crypto/ec/ec_mult.c | 29 |
1 files changed, 15 insertions, 14 deletions
diff --git a/crypto/ec/ec_mult.c b/crypto/ec/ec_mult.c index b668e87ff7..c821cb8250 100644 --- a/crypto/ec/ec_mult.c +++ b/crypto/ec/ec_mult.c @@ -132,10 +132,11 @@ static int ec_mul_consttime(const EC_GROUP *group, EC_POINT *r, const BIGNUM *scalar, const EC_POINT *point, BN_CTX *ctx) { - int i, order_bits, group_top, kbit, pbit, Z_is_one; + int i, cardinality_bits, group_top, kbit, pbit, Z_is_one; EC_POINT *s = NULL; BIGNUM *k = NULL; BIGNUM *lambda = NULL; + BIGNUM *cardinality = NULL; BN_CTX *new_ctx = NULL; int ret = 0; @@ -144,8 +145,6 @@ static int ec_mul_consttime(const EC_GROUP *group, EC_POINT *r, BN_CTX_start(ctx); - order_bits = BN_num_bits(group->order); - s = EC_POINT_new(group); if (s == NULL) goto err; @@ -160,18 +159,20 @@ static int ec_mul_consttime(const EC_GROUP *group, EC_POINT *r, EC_POINT_BN_set_flags(s, BN_FLG_CONSTTIME); + cardinality = BN_CTX_get(ctx); lambda = BN_CTX_get(ctx); k = BN_CTX_get(ctx); - if (k == NULL) + if (k == NULL || !BN_mul(cardinality, group->order, group->cofactor, ctx)) goto err; /* - * Group orders are often on a word boundary. + * Group cardinalities are often on a word boundary. * So when we pad the scalar, some timing diff might * pop if it needs to be expanded due to carries. * So expand ahead of time. */ - group_top = bn_get_top(group->order); + cardinality_bits = BN_num_bits(cardinality); + group_top = bn_get_top(cardinality); if ((bn_wexpand(k, group_top + 1) == NULL) || (bn_wexpand(lambda, group_top + 1) == NULL)) goto err; @@ -181,25 +182,25 @@ static int ec_mul_consttime(const EC_GROUP *group, EC_POINT *r, BN_set_flags(k, BN_FLG_CONSTTIME); - if ((BN_num_bits(k) > order_bits) || (BN_is_negative(k))) { + if ((BN_num_bits(k) > cardinality_bits) || (BN_is_negative(k))) { /*- * this is an unusual input, and we don't guarantee * constant-timeness */ - if (!BN_nnmod(k, k, group->order, ctx)) + if (!BN_nnmod(k, k, cardinality, ctx)) goto err; } - if (!BN_add(lambda, k, group->order)) + if (!BN_add(lambda, k, cardinality)) goto err; BN_set_flags(lambda, BN_FLG_CONSTTIME); - if (!BN_add(k, lambda, group->order)) + if (!BN_add(k, lambda, cardinality)) goto err; /* - * lambda := scalar + order - * k := scalar + 2*order + * lambda := scalar + cardinality + * k := scalar + 2*cardinality */ - kbit = BN_is_bit_set(lambda, order_bits); + kbit = BN_is_bit_set(lambda, cardinality_bits); BN_consttime_swap(kbit, k, lambda, group_top + 1); group_top = bn_get_top(group->field); @@ -300,7 +301,7 @@ static int ec_mul_consttime(const EC_GROUP *group, EC_POINT *r, * This is XOR. pbit tracks the previous bit of k. */ - for (i = order_bits - 1; i >= 0; i--) { + for (i = cardinality_bits - 1; i >= 0; i--) { kbit = BN_is_bit_set(k, i) ^ pbit; EC_POINT_CSWAP(kbit, r, s, group_top, Z_is_one); if (!EC_POINT_add(group, s, r, s, ctx)) |