OpenSSL: Use EC_POINT_clear_free instead of EC_POINT_free

This changes OpenSSL calls to explicitly clear the EC_POINT memory
allocations when freeing them. This adds an extra layer of security by
avoiding leaving potentially private keys into local memory after they
are not needed anymore. While some of these variables are not really
private (e.g., they are sent in clear anyway), the extra cost of
clearing them is not significant and it is simpler to just clear these
explicitly rather than review each possible code path to confirm where
this does not help.

Signed-off-by: Florent Daigniere <nextgens@freenetproject.org>

src/crypto/crypto_openssl.c

@@ -1157,13 +1157,13 @@ struct crypto_ec_point * crypto_ec_point_from_bin(struct crypto_ec *e,
 	if (x == NULL || y == NULL || elem == NULL) {
 		BN_clear_free(x);
 		BN_clear_free(y);
-		EC_POINT_free(elem);
+		EC_POINT_clear_free(elem);
 		return NULL;
 	}
 
 	if (!EC_POINT_set_affine_coordinates_GFp(e->group, elem, x, y,
 						 e->bnctx)) {
-		EC_POINT_free(elem);
+		EC_POINT_clear_free(elem);
 		elem = NULL;
 	}
 

src/eap_common/eap_pwd_common.c

@@ -263,7 +263,7 @@ int compute_password_element(EAP_PWD_group *grp, u16 num,
  fail:
 		EC_GROUP_free(grp->group);
 		grp->group = NULL;
-		EC_POINT_free(grp->pwe);
+		EC_POINT_clear_free(grp->pwe);
 		grp->pwe = NULL;
 		BN_clear_free(grp->order);
 		grp->order = NULL;

src/eap_peer/eap_pwd.c

@@ -153,14 +153,14 @@ static void eap_pwd_deinit(struct eap_sm *sm, void *priv)
 	BN_clear_free(data->my_scalar);
 	BN_clear_free(data->k);
 	BN_CTX_free(data->bnctx);
-	EC_POINT_free(data->my_element);
-	EC_POINT_free(data->server_element);
+	EC_POINT_clear_free(data->my_element);
+	EC_POINT_clear_free(data->server_element);
 	os_free(data->id_peer);
 	os_free(data->id_server);
 	bin_clear_free(data->password, data->password_len);
 	if (data->grp) {
 		EC_GROUP_free(data->grp->group);
-		EC_POINT_free(data->grp->pwe);
+		EC_POINT_clear_free(data->grp->pwe);
 		BN_clear_free(data->grp->order);
 		BN_clear_free(data->grp->prime);
 		os_free(data->grp);
@@ -474,8 +474,8 @@ fin:
 	BN_clear_free(x);
 	BN_clear_free(y);
 	BN_clear_free(cofactor);
-	EC_POINT_free(K);
-	EC_POINT_free(point);
+	EC_POINT_clear_free(K);
+	EC_POINT_clear_free(point);
 	if (data->outbuf == NULL)
 		eap_pwd_state(data, FAILURE);
 	else

src/eap_server/eap_server_pwd.c

@@ -140,14 +140,14 @@ static void eap_pwd_reset(struct eap_sm *sm, void *priv)
 	BN_clear_free(data->my_scalar);
 	BN_clear_free(data->k);
 	BN_CTX_free(data->bnctx);
-	EC_POINT_free(data->my_element);
-	EC_POINT_free(data->peer_element);
+	EC_POINT_clear_free(data->my_element);
+	EC_POINT_clear_free(data->peer_element);
 	os_free(data->id_peer);
 	os_free(data->id_server);
 	bin_clear_free(data->password, data->password_len);
 	if (data->grp) {
 		EC_GROUP_free(data->grp->group);
-		EC_POINT_free(data->grp->pwe);
+		EC_POINT_clear_free(data->grp->pwe);
 		BN_clear_free(data->grp->order);
 		BN_clear_free(data->grp->prime);
 		os_free(data->grp);
@@ -724,8 +724,8 @@ eap_pwd_process_commit_resp(struct eap_sm *sm, struct eap_pwd_data *data,
 	res = 1;
 
 fin:
-	EC_POINT_free(K);
-	EC_POINT_free(point);
+	EC_POINT_clear_free(K);
+	EC_POINT_clear_free(point);
 	BN_clear_free(cofactor);
 	BN_clear_free(x);
 	BN_clear_free(y);