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@ -25,32 +25,37 @@ static const secp256k1_fe_t secp256k1_ecdsa_const_p_minus_order = SECP256K1_FE_C
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static int secp256k1_ecdsa_sig_parse(secp256k1_ecdsa_sig_t *r, const unsigned char *sig, int size) {
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unsigned char ra[32] = {0}, sa[32] = {0};
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const unsigned char *rp;
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const unsigned char *sp;
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int lenr;
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int lens;
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int overflow;
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if (sig[0] != 0x30) return 0;
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int lenr = sig[3];
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lenr = sig[3];
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if (5+lenr >= size) return 0;
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int lens = sig[lenr+5];
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lens = sig[lenr+5];
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if (sig[1] != lenr+lens+4) return 0;
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if (lenr+lens+6 > size) return 0;
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if (sig[2] != 0x02) return 0;
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if (lenr == 0) return 0;
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if (sig[lenr+4] != 0x02) return 0;
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if (lens == 0) return 0;
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const unsigned char *sp = sig + 6 + lenr;
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sp = sig + 6 + lenr;
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while (lens > 0 && sp[0] == 0) {
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lens--;
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sp++;
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}
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if (lens > 32) return 0;
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const unsigned char *rp = sig + 4;
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rp = sig + 4;
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while (lenr > 0 && rp[0] == 0) {
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lenr--;
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rp++;
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}
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if (lenr > 32) return 0;
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unsigned char ra[32] = {0}, sa[32] = {0};
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memcpy(ra + 32 - lenr, rp, lenr);
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memcpy(sa + 32 - lens, sp, lens);
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int overflow = 0;
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overflow = 0;
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secp256k1_scalar_set_b32(&r->r, ra, &overflow);
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if (overflow) return 0;
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secp256k1_scalar_set_b32(&r->s, sa, &overflow);
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@ -60,10 +65,10 @@ static int secp256k1_ecdsa_sig_parse(secp256k1_ecdsa_sig_t *r, const unsigned ch
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static int secp256k1_ecdsa_sig_serialize(unsigned char *sig, int *size, const secp256k1_ecdsa_sig_t *a) {
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unsigned char r[33] = {0}, s[33] = {0};
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secp256k1_scalar_get_b32(&r[1], &a->r);
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secp256k1_scalar_get_b32(&s[1], &a->s);
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unsigned char *rp = r, *sp = s;
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int lenR = 33, lenS = 33;
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secp256k1_scalar_get_b32(&r[1], &a->r);
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secp256k1_scalar_get_b32(&s[1], &a->s);
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while (lenR > 1 && rp[0] == 0 && rp[1] < 0x80) { lenR--; rp++; }
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while (lenS > 1 && sp[0] == 0 && sp[1] < 0x80) { lenS--; sp++; }
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if (*size < 6+lenS+lenR)
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@ -81,21 +86,24 @@ static int secp256k1_ecdsa_sig_serialize(unsigned char *sig, int *size, const se
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}
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static int secp256k1_ecdsa_sig_verify(const secp256k1_ecdsa_sig_t *sig, const secp256k1_ge_t *pubkey, const secp256k1_scalar_t *message) {
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unsigned char c[32];
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secp256k1_scalar_t sn, u1, u2;
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secp256k1_fe_t xr;
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secp256k1_gej_t pubkeyj;
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secp256k1_gej_t pr;
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if (secp256k1_scalar_is_zero(&sig->r) || secp256k1_scalar_is_zero(&sig->s))
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return 0;
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secp256k1_scalar_t sn, u1, u2;
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secp256k1_scalar_inverse_var(&sn, &sig->s);
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secp256k1_scalar_mul(&u1, &sn, message);
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secp256k1_scalar_mul(&u2, &sn, &sig->r);
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secp256k1_gej_t pubkeyj; secp256k1_gej_set_ge(&pubkeyj, pubkey);
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secp256k1_gej_t pr; secp256k1_ecmult(&pr, &pubkeyj, &u2, &u1);
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secp256k1_gej_set_ge(&pubkeyj, pubkey);
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secp256k1_ecmult(&pr, &pubkeyj, &u2, &u1);
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if (secp256k1_gej_is_infinity(&pr)) {
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return 0;
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}
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unsigned char c[32];
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secp256k1_scalar_get_b32(c, &sig->r);
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secp256k1_fe_t xr;
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secp256k1_fe_set_b32(&xr, c);
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/** We now have the recomputed R point in pr, and its claimed x coordinate (modulo n)
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@ -131,44 +139,47 @@ static int secp256k1_ecdsa_sig_verify(const secp256k1_ecdsa_sig_t *sig, const se
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}
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static int secp256k1_ecdsa_sig_recover(const secp256k1_ecdsa_sig_t *sig, secp256k1_ge_t *pubkey, const secp256k1_scalar_t *message, int recid) {
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unsigned char brx[32];
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secp256k1_fe_t fx;
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secp256k1_ge_t x;
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secp256k1_gej_t xj;
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secp256k1_scalar_t rn, u1, u2;
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secp256k1_gej_t qj;
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if (secp256k1_scalar_is_zero(&sig->r) || secp256k1_scalar_is_zero(&sig->s))
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return 0;
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unsigned char brx[32];
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secp256k1_scalar_get_b32(brx, &sig->r);
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secp256k1_fe_t fx;
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VERIFY_CHECK(secp256k1_fe_set_b32(&fx, brx)); /* brx comes from a scalar, so is less than the order; certainly less than p */
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if (recid & 2) {
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if (secp256k1_fe_cmp_var(&fx, &secp256k1_ecdsa_const_p_minus_order) >= 0)
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return 0;
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secp256k1_fe_add(&fx, &secp256k1_ecdsa_const_order_as_fe);
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}
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secp256k1_ge_t x;
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if (!secp256k1_ge_set_xo_var(&x, &fx, recid & 1))
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return 0;
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secp256k1_gej_t xj;
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secp256k1_gej_set_ge(&xj, &x);
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secp256k1_scalar_t rn, u1, u2;
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secp256k1_scalar_inverse_var(&rn, &sig->r);
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secp256k1_scalar_mul(&u1, &rn, message);
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secp256k1_scalar_negate(&u1, &u1);
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secp256k1_scalar_mul(&u2, &rn, &sig->s);
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secp256k1_gej_t qj;
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secp256k1_ecmult(&qj, &xj, &u2, &u1);
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secp256k1_ge_set_gej_var(pubkey, &qj);
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return !secp256k1_gej_is_infinity(&qj);
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}
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static int secp256k1_ecdsa_sig_sign(secp256k1_ecdsa_sig_t *sig, const secp256k1_scalar_t *seckey, const secp256k1_scalar_t *message, const secp256k1_scalar_t *nonce, int *recid) {
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unsigned char b[32];
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secp256k1_gej_t rp;
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secp256k1_ecmult_gen(&rp, nonce);
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secp256k1_ge_t r;
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secp256k1_scalar_t n;
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int overflow = 0;
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secp256k1_ecmult_gen(&rp, nonce);
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secp256k1_ge_set_gej(&r, &rp);
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unsigned char b[32];
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secp256k1_fe_normalize(&r.x);
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secp256k1_fe_normalize(&r.y);
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secp256k1_fe_get_b32(b, &r.x);
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int overflow = 0;
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secp256k1_scalar_set_b32(&sig->r, b, &overflow);
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if (secp256k1_scalar_is_zero(&sig->r)) {
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/* P.x = order is on the curve, so technically sig->r could end up zero, which would be an invalid signature. */
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@ -178,7 +189,6 @@ static int secp256k1_ecdsa_sig_sign(secp256k1_ecdsa_sig_t *sig, const secp256k1_
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}
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if (recid)
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*recid = (overflow ? 2 : 0) | (secp256k1_fe_is_odd(&r.y) ? 1 : 0);
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secp256k1_scalar_t n;
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secp256k1_scalar_mul(&n, &sig->r, seckey);
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secp256k1_scalar_add(&n, &n, message);
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secp256k1_scalar_inverse(&sig->s, nonce);
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