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-rw-r--r--crypto/secp256k1/libsecp256k1/src/ecdsa_impl.h211
1 files changed, 131 insertions, 80 deletions
diff --git a/crypto/secp256k1/libsecp256k1/src/ecdsa_impl.h b/crypto/secp256k1/libsecp256k1/src/ecdsa_impl.h
index 4a172b3c5..453bb1188 100644
--- a/crypto/secp256k1/libsecp256k1/src/ecdsa_impl.h
+++ b/crypto/secp256k1/libsecp256k1/src/ecdsa_impl.h
@@ -1,5 +1,5 @@
/**********************************************************************
- * Copyright (c) 2013, 2014 Pieter Wuille *
+ * Copyright (c) 2013-2015 Pieter Wuille *
* Distributed under the MIT software license, see the accompanying *
* file COPYING or http://www.opensource.org/licenses/mit-license.php.*
**********************************************************************/
@@ -46,66 +46,133 @@ static const secp256k1_fe secp256k1_ecdsa_const_p_minus_order = SECP256K1_FE_CON
0, 0, 0, 1, 0x45512319UL, 0x50B75FC4UL, 0x402DA172UL, 0x2FC9BAEEUL
);
-static int secp256k1_ecdsa_sig_parse(secp256k1_scalar *rr, secp256k1_scalar *rs, const unsigned char *sig, size_t size) {
- unsigned char ra[32] = {0}, sa[32] = {0};
- const unsigned char *rp;
- const unsigned char *sp;
- size_t lenr;
- size_t lens;
- int overflow;
- if (sig[0] != 0x30) {
- return 0;
+static int secp256k1_der_read_len(const unsigned char **sigp, const unsigned char *sigend) {
+ int lenleft, b1;
+ size_t ret = 0;
+ if (*sigp >= sigend) {
+ return -1;
}
- lenr = sig[3];
- if (5+lenr >= size) {
- return 0;
+ b1 = *((*sigp)++);
+ if (b1 == 0xFF) {
+ /* X.690-0207 8.1.3.5.c the value 0xFF shall not be used. */
+ return -1;
}
- lens = sig[lenr+5];
- if (sig[1] != lenr+lens+4) {
- return 0;
+ if ((b1 & 0x80) == 0) {
+ /* X.690-0207 8.1.3.4 short form length octets */
+ return b1;
}
- if (lenr+lens+6 > size) {
- return 0;
+ if (b1 == 0x80) {
+ /* Indefinite length is not allowed in DER. */
+ return -1;
+ }
+ /* X.690-207 8.1.3.5 long form length octets */
+ lenleft = b1 & 0x7F;
+ if (lenleft > sigend - *sigp) {
+ return -1;
+ }
+ if (**sigp == 0) {
+ /* Not the shortest possible length encoding. */
+ return -1;
}
- if (sig[2] != 0x02) {
+ if ((size_t)lenleft > sizeof(size_t)) {
+ /* The resulting length would exceed the range of a size_t, so
+ * certainly longer than the passed array size.
+ */
+ return -1;
+ }
+ while (lenleft > 0) {
+ if ((ret >> ((sizeof(size_t) - 1) * 8)) != 0) {
+ }
+ ret = (ret << 8) | **sigp;
+ if (ret + lenleft > (size_t)(sigend - *sigp)) {
+ /* Result exceeds the length of the passed array. */
+ return -1;
+ }
+ (*sigp)++;
+ lenleft--;
+ }
+ if (ret < 128) {
+ /* Not the shortest possible length encoding. */
+ return -1;
+ }
+ return ret;
+}
+
+static int secp256k1_der_parse_integer(secp256k1_scalar *r, const unsigned char **sig, const unsigned char *sigend) {
+ int overflow = 0;
+ unsigned char ra[32] = {0};
+ int rlen;
+
+ if (*sig == sigend || **sig != 0x02) {
+ /* Not a primitive integer (X.690-0207 8.3.1). */
return 0;
}
- if (lenr == 0) {
+ (*sig)++;
+ rlen = secp256k1_der_read_len(sig, sigend);
+ if (rlen <= 0 || (*sig) + rlen > sigend) {
+ /* Exceeds bounds or not at least length 1 (X.690-0207 8.3.1). */
return 0;
}
- if (sig[lenr+4] != 0x02) {
+ if (**sig == 0x00 && rlen > 1 && (((*sig)[1]) & 0x80) == 0x00) {
+ /* Excessive 0x00 padding. */
return 0;
}
- if (lens == 0) {
+ if (**sig == 0xFF && rlen > 1 && (((*sig)[1]) & 0x80) == 0x80) {
+ /* Excessive 0xFF padding. */
return 0;
}
- sp = sig + 6 + lenr;
- while (lens > 0 && sp[0] == 0) {
- lens--;
- sp++;
+ if ((**sig & 0x80) == 0x80) {
+ /* Negative. */
+ overflow = 1;
+ }
+ while (rlen > 0 && **sig == 0) {
+ /* Skip leading zero bytes */
+ rlen--;
+ (*sig)++;
+ }
+ if (rlen > 32) {
+ overflow = 1;
+ }
+ if (!overflow) {
+ memcpy(ra + 32 - rlen, *sig, rlen);
+ secp256k1_scalar_set_b32(r, ra, &overflow);
+ }
+ if (overflow) {
+ secp256k1_scalar_set_int(r, 0);
+ }
+ (*sig) += rlen;
+ return 1;
+}
+
+static int secp256k1_ecdsa_sig_parse(secp256k1_scalar *rr, secp256k1_scalar *rs, const unsigned char *sig, size_t size) {
+ const unsigned char *sigend = sig + size;
+ int rlen;
+ if (sig == sigend || *(sig++) != 0x30) {
+ /* The encoding doesn't start with a constructed sequence (X.690-0207 8.9.1). */
+ return 0;
}
- if (lens > 32) {
+ rlen = secp256k1_der_read_len(&sig, sigend);
+ if (rlen < 0 || sig + rlen > sigend) {
+ /* Tuple exceeds bounds */
return 0;
}
- rp = sig + 4;
- while (lenr > 0 && rp[0] == 0) {
- lenr--;
- rp++;
+ if (sig + rlen != sigend) {
+ /* Garbage after tuple. */
+ return 0;
}
- if (lenr > 32) {
+
+ if (!secp256k1_der_parse_integer(rr, &sig, sigend)) {
return 0;
}
- memcpy(ra + 32 - lenr, rp, lenr);
- memcpy(sa + 32 - lens, sp, lens);
- overflow = 0;
- secp256k1_scalar_set_b32(rr, ra, &overflow);
- if (overflow) {
+ if (!secp256k1_der_parse_integer(rs, &sig, sigend)) {
return 0;
}
- secp256k1_scalar_set_b32(rs, sa, &overflow);
- if (overflow) {
+
+ if (sig != sigend) {
+ /* Trailing garbage inside tuple. */
return 0;
}
+
return 1;
}
@@ -136,7 +203,9 @@ static int secp256k1_ecdsa_sig_serialize(unsigned char *sig, size_t *size, const
static int secp256k1_ecdsa_sig_verify(const secp256k1_ecmult_context *ctx, const secp256k1_scalar *sigr, const secp256k1_scalar *sigs, const secp256k1_ge *pubkey, const secp256k1_scalar *message) {
unsigned char c[32];
secp256k1_scalar sn, u1, u2;
+#if !defined(EXHAUSTIVE_TEST_ORDER)
secp256k1_fe xr;
+#endif
secp256k1_gej pubkeyj;
secp256k1_gej pr;
@@ -152,6 +221,19 @@ static int secp256k1_ecdsa_sig_verify(const secp256k1_ecmult_context *ctx, const
if (secp256k1_gej_is_infinity(&pr)) {
return 0;
}
+
+#if defined(EXHAUSTIVE_TEST_ORDER)
+{
+ secp256k1_scalar computed_r;
+ secp256k1_ge pr_ge;
+ secp256k1_ge_set_gej(&pr_ge, &pr);
+ secp256k1_fe_normalize(&pr_ge.x);
+
+ secp256k1_fe_get_b32(c, &pr_ge.x);
+ secp256k1_scalar_set_b32(&computed_r, c, NULL);
+ return secp256k1_scalar_eq(sigr, &computed_r);
+}
+#else
secp256k1_scalar_get_b32(c, sigr);
secp256k1_fe_set_b32(&xr, c);
@@ -172,11 +254,11 @@ static int secp256k1_ecdsa_sig_verify(const secp256k1_ecmult_context *ctx, const
* secp256k1_gej_eq_x implements the (xr * pr.z^2 mod p == pr.x) test.
*/
if (secp256k1_gej_eq_x_var(&xr, &pr)) {
- /* xr.x == xr * xr.z^2 mod p, so the signature is valid. */
+ /* xr * pr.z^2 mod p == pr.x, so the signature is valid. */
return 1;
}
if (secp256k1_fe_cmp_var(&xr, &secp256k1_ecdsa_const_p_minus_order) >= 0) {
- /* xr + p >= n, so we can skip testing the second case. */
+ /* xr + n >= p, so we can skip testing the second case. */
return 0;
}
secp256k1_fe_add(&xr, &secp256k1_ecdsa_const_order_as_fe);
@@ -185,39 +267,7 @@ static int secp256k1_ecdsa_sig_verify(const secp256k1_ecmult_context *ctx, const
return 1;
}
return 0;
-}
-
-static int secp256k1_ecdsa_sig_recover(const secp256k1_ecmult_context *ctx, const secp256k1_scalar *sigr, const secp256k1_scalar* sigs, secp256k1_ge *pubkey, const secp256k1_scalar *message, int recid) {
- unsigned char brx[32];
- secp256k1_fe fx;
- secp256k1_ge x;
- secp256k1_gej xj;
- secp256k1_scalar rn, u1, u2;
- secp256k1_gej qj;
-
- if (secp256k1_scalar_is_zero(sigr) || secp256k1_scalar_is_zero(sigs)) {
- return 0;
- }
-
- secp256k1_scalar_get_b32(brx, sigr);
- VERIFY_CHECK(secp256k1_fe_set_b32(&fx, brx)); /* brx comes from a scalar, so is less than the order; certainly less than p */
- if (recid & 2) {
- if (secp256k1_fe_cmp_var(&fx, &secp256k1_ecdsa_const_p_minus_order) >= 0) {
- return 0;
- }
- secp256k1_fe_add(&fx, &secp256k1_ecdsa_const_order_as_fe);
- }
- if (!secp256k1_ge_set_xo_var(&x, &fx, recid & 1)) {
- return 0;
- }
- secp256k1_gej_set_ge(&xj, &x);
- secp256k1_scalar_inverse_var(&rn, sigr);
- secp256k1_scalar_mul(&u1, &rn, message);
- secp256k1_scalar_negate(&u1, &u1);
- secp256k1_scalar_mul(&u2, &rn, sigs);
- secp256k1_ecmult(ctx, &qj, &xj, &u2, &u1);
- secp256k1_ge_set_gej_var(pubkey, &qj);
- return !secp256k1_gej_is_infinity(&qj);
+#endif
}
static int secp256k1_ecdsa_sig_sign(const secp256k1_ecmult_gen_context *ctx, secp256k1_scalar *sigr, secp256k1_scalar *sigs, const secp256k1_scalar *seckey, const secp256k1_scalar *message, const secp256k1_scalar *nonce, int *recid) {
@@ -233,13 +283,14 @@ static int secp256k1_ecdsa_sig_sign(const secp256k1_ecmult_gen_context *ctx, sec
secp256k1_fe_normalize(&r.y);
secp256k1_fe_get_b32(b, &r.x);
secp256k1_scalar_set_b32(sigr, b, &overflow);
- if (secp256k1_scalar_is_zero(sigr)) {
- /* P.x = order is on the curve, so technically sig->r could end up zero, which would be an invalid signature. */
- secp256k1_gej_clear(&rp);
- secp256k1_ge_clear(&r);
- return 0;
- }
+ /* These two conditions should be checked before calling */
+ VERIFY_CHECK(!secp256k1_scalar_is_zero(sigr));
+ VERIFY_CHECK(overflow == 0);
+
if (recid) {
+ /* The overflow condition is cryptographically unreachable as hitting it requires finding the discrete log
+ * of some P where P.x >= order, and only 1 in about 2^127 points meet this criteria.
+ */
*recid = (overflow ? 2 : 0) | (secp256k1_fe_is_odd(&r.y) ? 1 : 0);
}
secp256k1_scalar_mul(&n, sigr, seckey);