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https://github.com/trezor/trezor-firmware.git
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add check that pub.y != res.y
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3589cf5cbf
commit
8423c7abfd
8
bignum.c
8
bignum.c
@ -93,6 +93,14 @@ int bn_is_less(const bignum256 *a, const bignum256 *b)
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return 0;
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}
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int bn_is_equal(const bignum256 *a, const bignum256 *b) {
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int i;
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for (i = 0; i < 9; i++) {
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if (a->val[i] != b->val[i]) return 0;
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}
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return 1;
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}
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int bn_bitlen(const bignum256 *a) {
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int i = 8, j;
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while (i >= 0 && a->val[i] == 0) i--;
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2
bignum.h
2
bignum.h
@ -63,6 +63,8 @@ int bn_is_zero(const bignum256 *a);
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int bn_is_less(const bignum256 *a, const bignum256 *b);
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int bn_is_equal(const bignum256 *a, const bignum256 *b);
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int bn_bitlen(const bignum256 *a);
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void bn_lshift(bignum256 *a);
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11
ecdsa.c
11
ecdsa.c
@ -396,11 +396,18 @@ int ecdsa_verify(const uint8_t *pub_key, const uint8_t *sig, const uint8_t *msg,
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scalar_multiply(&z, &res);
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}
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// TODO both pub and res can be infinity, can have y = 0 OR can be equal
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// both pub and res can be infinity, can have y = 0 OR can be equal -> false negative
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for (i = 0; i < 9; i++) {
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for (j = 0; j < 30; j++) {
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if (i == 8 && (s.val[i] >> j) == 0) break;
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if (s.val[i] & (1u << j)) {
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bn_mod(&(pub.y), &prime256k1);
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bn_mod(&(res.y), &prime256k1);
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if (bn_is_equal(&(pub.y), &(res.y))) {
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// this is not a failure, but a very inprobable case
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// that we don't handle because of its inprobability
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return 4;
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}
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point_add(&pub, &res);
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}
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point_double(&pub);
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@ -413,7 +420,7 @@ int ecdsa_verify(const uint8_t *pub_key, const uint8_t *sig, const uint8_t *msg,
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// signature does not match
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for (i = 0; i < 9; i++) {
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if (res.x.val[i] != r.val[i]) {
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return 4;
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return 5;
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}
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}
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