X-Git-Url: https://git.openssl.org/?p=openssl.git;a=blobdiff_plain;f=crypto%2Fecdsa%2Fecs_ossl.c;h=c23343b64d885c3e9a7e4852c6ce21574737f9c0;hp=3ead1af94e7351c5e4bf76aefe146e61b1e636a5;hb=8aed2a7548362e88e84a7feb795a3a97e8395008;hpb=3d11b8f89617edc81d01329dbb5bf134fcda3303

diff --git a/crypto/ecdsa/ecs_ossl.c b/crypto/ecdsa/ecs_ossl.c
index 3ead1af94e..c23343b64d 100644
--- a/crypto/ecdsa/ecs_ossl.c
+++ b/crypto/ecdsa/ecs_ossl.c
@@ -144,6 +144,14 @@ static int ecdsa_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in, BIGNUM **kinvp,
 			}
 		while (BN_is_zero(k));
 
+		/* We do not want timing information to leak the length of k,
+		 * so we compute G*k using an equivalent scalar of fixed
+		 * bit-length. */
+
+		if (!BN_add(k, k, order)) goto err;
+		if (BN_num_bits(k) <= BN_num_bits(order))
+			if (!BN_add(k, k, order)) goto err;
+
 		/* compute r the x-coordinate of generator * k */
 		if (!EC_POINT_mul(group, tmp_point, k, NULL, NULL, ctx))
 		{
@@ -159,6 +167,7 @@ static int ecdsa_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in, BIGNUM **kinvp,
 				goto err;
 			}
 		}
+#ifndef OPENSSL_NO_EC2M
 		else /* NID_X9_62_characteristic_two_field */
 		{
 			if (!EC_POINT_get_affine_coordinates_GF2m(group,
@@ -168,6 +177,7 @@ static int ecdsa_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in, BIGNUM **kinvp,
 				goto err;
 			}
 		}
+#endif
 		if (!BN_nnmod(r, X, order, ctx))
 		{
 			ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
@@ -177,11 +187,37 @@ static int ecdsa_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in, BIGNUM **kinvp,
 	while (BN_is_zero(r));
 
 	/* compute the inverse of k */
-	if (!BN_mod_inverse(k, k, order, ctx))
-	{
-		ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
-		goto err;	
-	}
+	if (EC_GROUP_get_mont_data(group) != NULL)
+		{
+		/* We want inverse in constant time, therefore we utilize the
+		 * fact order must be prime and use Fermats Little Theorem
+		 * instead. */
+		if (!BN_set_word(X, 2) )
+			{
+			ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
+			goto err;
+			}
+		if (!BN_mod_sub(X, order, X, order, ctx))
+			{
+			ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
+			goto err;
+			}
+		BN_set_flags(X, BN_FLG_CONSTTIME);
+		if (!BN_mod_exp_mont_consttime(k, k, X, order, ctx, EC_GROUP_get_mont_data(group)))
+			{
+			ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
+			goto err;
+			}
+		}
+	else
+		{
+		if (!BN_mod_inverse(k, k, order, ctx))
+			{
+			ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
+			goto err;	
+			}
+		}
+
 	/* clear old values if necessary */
 	if (*rp != NULL)
 		BN_clear_free(*rp);
@@ -212,7 +248,7 @@ err:
 static ECDSA_SIG *ecdsa_do_sign(const unsigned char *dgst, int dgst_len, 
 		const BIGNUM *in_kinv, const BIGNUM *in_r, EC_KEY *eckey)
 {
-	int     ok = 0;
+	int     ok = 0, i;
 	BIGNUM *kinv=NULL, *s, *m=NULL,*tmp=NULL,*order=NULL;
 	const BIGNUM *ckinv;
 	BN_CTX     *ctx = NULL;
@@ -251,22 +287,19 @@ static ECDSA_SIG *ecdsa_do_sign(const unsigned char *dgst, int dgst_len,
 		ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_EC_LIB);
 		goto err;
 	}
-	if (8 * dgst_len > BN_num_bits(order))
+	i = BN_num_bits(order);
+	/* Need to truncate digest if it is too long: first truncate whole
+	 * bytes.
+	 */
+	if (8 * dgst_len > i)
+		dgst_len = (i + 7)/8;
+	if (!BN_bin2bn(dgst, dgst_len, m))
 	{
-		/* XXX
-		 * 
-		 * Should provide for optional hash truncation:
-		 * Keep the BN_num_bits(order) leftmost bits of dgst
-		 * (see March 2006 FIPS 186-3 draft, which has a few
-		 * confusing errors in this part though)
-		 */
-
-		ECDSAerr(ECDSA_F_ECDSA_DO_SIGN,
-			ECDSA_R_DATA_TOO_LARGE_FOR_KEY_SIZE);
+		ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB);
 		goto err;
 	}
-
-	if (!BN_bin2bn(dgst, dgst_len, m))
+	/* If still too long truncate remaining bits with a shift */
+	if ((8 * dgst_len > i) && !BN_rshift(m, m, 8 - (i & 0x7)))
 	{
 		ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB);
 		goto err;
@@ -346,7 +379,7 @@ err:
 static int ecdsa_do_verify(const unsigned char *dgst, int dgst_len,
 		const ECDSA_SIG *sig, EC_KEY *eckey)
 {
-	int ret = -1;
+	int ret = -1, i;
 	BN_CTX   *ctx;
 	BIGNUM   *order, *u1, *u2, *m, *X;
 	EC_POINT *point = NULL;
@@ -384,21 +417,6 @@ static int ecdsa_do_verify(const unsigned char *dgst, int dgst_len,
 		ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_EC_LIB);
 		goto err;
 	}
-	if (8 * dgst_len > BN_num_bits(order))
-	{
-		/* XXX
-		 * 
-		 * Should provide for optional hash truncation:
-		 * Keep the BN_num_bits(order) leftmost bits of dgst
-		 * (see March 2006 FIPS 186-3 draft, which has a few
-		 * confusing errors in this part though)
-		 */
-
-		ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY,
-			ECDSA_R_DATA_TOO_LARGE_FOR_KEY_SIZE);
-		ret = 0;
-		goto err;
-	}
 
 	if (BN_is_zero(sig->r)          || BN_is_negative(sig->r) || 
 	    BN_ucmp(sig->r, order) >= 0 || BN_is_zero(sig->s)  ||
@@ -415,11 +433,23 @@ static int ecdsa_do_verify(const unsigned char *dgst, int dgst_len,
 		goto err;
 	}
 	/* digest -> m */
+	i = BN_num_bits(order);
+	/* Need to truncate digest if it is too long: first truncate whole
+	 * bytes.
+	 */
+	if (8 * dgst_len > i)
+		dgst_len = (i + 7)/8;
 	if (!BN_bin2bn(dgst, dgst_len, m))
 	{
 		ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB);
 		goto err;
 	}
+	/* If still too long truncate remaining bits with a shift */
+	if ((8 * dgst_len > i) && !BN_rshift(m, m, 8 - (i & 0x7)))
+	{
+		ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB);
+		goto err;
+	}
 	/* u1 = m * tmp mod order */
 	if (!BN_mod_mul(u1, m, u2, order, ctx))
 	{
@@ -452,6 +482,7 @@ static int ecdsa_do_verify(const unsigned char *dgst, int dgst_len,
 			goto err;
 		}
 	}
+#ifndef OPENSSL_NO_EC2M
 	else /* NID_X9_62_characteristic_two_field */
 	{
 		if (!EC_POINT_get_affine_coordinates_GF2m(group,
@@ -461,7 +492,7 @@ static int ecdsa_do_verify(const unsigned char *dgst, int dgst_len,
 			goto err;
 		}
 	}
-	
+#endif	
 	if (!BN_nnmod(u1, X, order, ctx))
 	{
 		ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB);