ec/ecdsa_ossl.c: switch to fixed-length Montgomery multiplication.
#include <string.h>
#include <openssl/err.h>
#include <openssl/obj_mac.h>
-#include <openssl/bn.h>
#include <openssl/rand.h>
-#include <openssl/ec.h>
+#include "internal/bn_int.h"
#include "ec_lcl.h"
int ossl_ecdsa_sign(int type, const unsigned char *dgst, int dlen,
@@ -164,7 +163,7 @@ ECDSA_SIG *ossl_ecdsa_sign_sig(const unsigned char *dgst, int dgst_len,
EC_KEY *eckey)
{
int ok = 0, i;
- BIGNUM *kinv = NULL, *s, *m = NULL, *tmp = NULL;
+ BIGNUM *kinv = NULL, *s, *m = NULL;
const BIGNUM *order, *ckinv;
BN_CTX *ctx = NULL;
const EC_GROUP *group;
@@ -197,8 +196,8 @@ ECDSA_SIG *ossl_ecdsa_sign_sig(const unsigned char *dgst, int dgst_len,
}
s = ret->s;
- if ((ctx = BN_CTX_new()) == NULL ||
- (tmp = BN_new()) == NULL || (m = BN_new()) == NULL) {
+ if ((ctx = BN_CTX_new()) == NULL
+ || (m = BN_new()) == NULL) {
ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_MALLOC_FAILURE);
goto err;
}
@@ -234,18 +233,32 @@ ECDSA_SIG *ossl_ecdsa_sign_sig(const unsigned char *dgst, int dgst_len,
}
}
- if (!BN_mod_mul(tmp, priv_key, ret->r, order, ctx)) {
+ /*
+ * With only one multiplicant being in Montgomery domain
+ * multiplication yields real result without post-conversion.
+ * Also note that all operations but last are performed with
+ * zero-padded vectors. Last operation, BN_mod_mul_montgomery
+ * below, returns user-visible value with removed zero padding.
+ */
+ if (!bn_to_mont_fixed_top(s, ret->r, group->mont_data, ctx)
+ || !bn_mul_mont_fixed_top(s, s, priv_key, group->mont_data, ctx)) {
ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_BN_LIB);
goto err;
}
- if (!BN_mod_add_quick(s, tmp, m, order)) {
+ if (!bn_mod_add_fixed_top(s, s, m, order)) {
ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_BN_LIB);
goto err;
}
- if (!BN_mod_mul(s, s, ckinv, order, ctx)) {
+ /*
+ * |s| can still be larger than modulus, because |m| can be. In
+ * such case we count on Montgomery reduction to tie it up.
+ */
+ if (!bn_to_mont_fixed_top(s, s, group->mont_data, ctx)
+ || !BN_mod_mul_montgomery(s, s, ckinv, group->mont_data, ctx)) {
ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_BN_LIB);
goto err;
}
+
if (BN_is_zero(s)) {
/*
* if kinv and r have been supplied by the caller, don't
@@ -269,7 +282,6 @@ ECDSA_SIG *ossl_ecdsa_sign_sig(const unsigned char *dgst, int dgst_len,
}
BN_CTX_free(ctx);
BN_clear_free(m);
- BN_clear_free(tmp);
BN_clear_free(kinv);
return ret;
}
