From 606c46fb6f65424ac6eac456f4390a7d87a492b4 Mon Sep 17 00:00:00 2001
From: "Dr. Stephen Henson" <steve@openssl.org>
Date: Tue, 1 Dec 2009 17:32:44 +0000
Subject: [PATCH] PR: 1432 Submitted by: "Andrzej Chmielowiec"
<achmielowiec@enigma.com.pl>, steve@openssl.org Approved by:
steve@openssl.org
Truncate hash if it is too large: as required by FIPS 186-3.
---
crypto/ecdsa/ecs_ossl.c | 54 ++++++++++++++++++-----------------------
1 file changed, 24 insertions(+), 30 deletions(-)
diff --git a/crypto/ecdsa/ecs_ossl.c b/crypto/ecdsa/ecs_ossl.c
index 3ead1af94e..551cf5068f 100644
--- a/crypto/ecdsa/ecs_ossl.c
+++ b/crypto/ecdsa/ecs_ossl.c
@@ -212,7 +212,7 @@ 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 +251,19 @@ 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 +343,7 @@ 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 +381,6 @@ 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 +397,23 @@ 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))
{
--
2.25.1