OpenSSL: Add wrapper functions for ECDH

These allow ECDH to be used with compressed public key encoding (only
x-coordinate). This is needed for FILS PFS and OWE.

Signed-off-by: Jouni Malinen <j@w1.fi>

src/crypto/crypto.h

@@ -1,6 +1,6 @@
 /*
  * Wrapper functions for crypto libraries
- * Copyright (c) 2004-2013, Jouni Malinen <j@w1.fi>
+ * Copyright (c) 2004-2017, Jouni Malinen <j@w1.fi>
  *
  * This software may be distributed under the terms of the BSD license.
  * See README for more details.
@@ -832,4 +832,12 @@ int crypto_ec_point_cmp(const struct crypto_ec *e,
 			const struct crypto_ec_point *a,
 			const struct crypto_ec_point *b);
 
+struct crypto_ecdh;
+
+struct crypto_ecdh * crypto_ecdh_init(int group);
+struct wpabuf * crypto_ecdh_get_pubkey(struct crypto_ecdh *ecdh, int inc_y);
+struct wpabuf * crypto_ecdh_set_peerkey(struct crypto_ecdh *ecdh, int inc_y,
+					const u8 *key, size_t len);
+void crypto_ecdh_deinit(struct crypto_ecdh *ecdh);
+
 #endif /* CRYPTO_H */

src/crypto/crypto_openssl.c

@@ -1,6 +1,6 @@
 /*
  * Wrapper functions for OpenSSL libcrypto
- * Copyright (c) 2004-2015, Jouni Malinen <j@w1.fi>
+ * Copyright (c) 2004-2017, Jouni Malinen <j@w1.fi>
  *
  * This software may be distributed under the terms of the BSD license.
  * See README for more details.
@@ -1363,6 +1363,7 @@ fail:
 
 struct crypto_ec {
 	EC_GROUP *group;
+	int nid;
 	BN_CTX *bnctx;
 	BIGNUM *prime;
 	BIGNUM *order;
@@ -1420,6 +1421,7 @@ struct crypto_ec * crypto_ec_init(int group)
 	if (e == NULL)
 		return NULL;
 
+	e->nid = nid;
 	e->bnctx = BN_CTX_new();
 	e->group = EC_GROUP_new_by_curve_name(nid);
 	e->prime = BN_new();
@@ -1660,4 +1662,239 @@ int crypto_ec_point_cmp(const struct crypto_ec *e,
 			    (const EC_POINT *) b, e->bnctx);
 }
 
+
+struct crypto_ecdh {
+	struct crypto_ec *ec;
+	EVP_PKEY *pkey;
+};
+
+struct crypto_ecdh * crypto_ecdh_init(int group)
+{
+	struct crypto_ecdh *ecdh;
+	EVP_PKEY *params = NULL;
+	EVP_PKEY_CTX *pctx = NULL;
+	EVP_PKEY_CTX *kctx = NULL;
+
+	ecdh = os_zalloc(sizeof(*ecdh));
+	if (!ecdh)
+		goto fail;
+
+	ecdh->ec = crypto_ec_init(group);
+	if (!ecdh->ec)
+		goto fail;
+
+	pctx = EVP_PKEY_CTX_new_id(EVP_PKEY_EC, NULL);
+	if (!pctx)
+		goto fail;
+
+	if (EVP_PKEY_paramgen_init(pctx) != 1) {
+		wpa_printf(MSG_ERROR,
+			   "OpenSSL: EVP_PKEY_paramgen_init failed: %s",
+			   ERR_error_string(ERR_get_error(), NULL));
+		goto fail;
+	}
+
+	if (EVP_PKEY_CTX_set_ec_paramgen_curve_nid(pctx, ecdh->ec->nid) != 1) {
+		wpa_printf(MSG_ERROR,
+			   "OpenSSL: EVP_PKEY_CTX_set_ec_paramgen_curve_nid failed: %s",
+			   ERR_error_string(ERR_get_error(), NULL));
+		goto fail;
+	}
+
+	if (EVP_PKEY_paramgen(pctx, &params) != 1) {
+		wpa_printf(MSG_ERROR, "OpenSSL: EVP_PKEY_paramgen failed: %s",
+			   ERR_error_string(ERR_get_error(), NULL));
+		goto fail;
+	}
+
+	kctx = EVP_PKEY_CTX_new(params, NULL);
+	if (!kctx)
+		goto fail;
+
+	if (EVP_PKEY_keygen_init(kctx) != 1) {
+		wpa_printf(MSG_ERROR,
+			   "OpenSSL: EVP_PKEY_keygen_init failed: %s",
+			   ERR_error_string(ERR_get_error(), NULL));
+		goto fail;
+	}
+
+	if (EVP_PKEY_keygen(kctx, &ecdh->pkey) != 1) {
+		wpa_printf(MSG_ERROR, "OpenSSL: EVP_PKEY_keygen failed: %s",
+			   ERR_error_string(ERR_get_error(), NULL));
+		goto fail;
+	}
+
+done:
+	EVP_PKEY_free(params);
+	EVP_PKEY_CTX_free(pctx);
+	EVP_PKEY_CTX_free(kctx);
+
+	return ecdh;
+fail:
+	crypto_ecdh_deinit(ecdh);
+	ecdh = NULL;
+	goto done;
+}
+
+
+struct wpabuf * crypto_ecdh_get_pubkey(struct crypto_ecdh *ecdh, int inc_y)
+{
+	struct wpabuf *buf = NULL;
+	EC_KEY *eckey;
+	const EC_POINT *pubkey;
+	BIGNUM *x, *y = NULL;
+	int len = BN_num_bytes(ecdh->ec->prime);
+	int res;
+
+	eckey = EVP_PKEY_get1_EC_KEY(ecdh->pkey);
+	if (!eckey)
+		return NULL;
+
+	pubkey = EC_KEY_get0_public_key(eckey);
+	if (!pubkey)
+		return NULL;
+
+	x = BN_new();
+	if (inc_y) {
+		y = BN_new();
+		if (!y)
+			goto fail;
+	}
+	buf = wpabuf_alloc(inc_y ? 2 * len : len);
+	if (!x || !buf)
+		goto fail;
+
+	if (EC_POINT_get_affine_coordinates_GFp(ecdh->ec->group, pubkey,
+						x, y, ecdh->ec->bnctx) != 1) {
+		wpa_printf(MSG_ERROR,
+			   "OpenSSL: EC_POINT_get_affine_coordinates_GFp failed: %s",
+			   ERR_error_string(ERR_get_error(), NULL));
+		goto fail;
+	}
+
+	res = crypto_bignum_to_bin((struct crypto_bignum *) x,
+				   wpabuf_put(buf, len), len, len);
+	if (res < 0)
+		goto fail;
+
+	if (inc_y) {
+		res = crypto_bignum_to_bin((struct crypto_bignum *) y,
+					   wpabuf_put(buf, len), len, len);
+		if (res < 0)
+			goto fail;
+	}
+
+done:
+	BN_clear_free(x);
+	BN_clear_free(y);
+	EC_KEY_free(eckey);
+
+	return buf;
+fail:
+	wpabuf_free(buf);
+	buf = NULL;
+	goto done;
+}
+
+
+struct wpabuf * crypto_ecdh_set_peerkey(struct crypto_ecdh *ecdh, int inc_y,
+					const u8 *key, size_t len)
+{
+	BIGNUM *x, *y = NULL;
+	EVP_PKEY_CTX *ctx = NULL;
+	EVP_PKEY *peerkey = NULL;
+	struct wpabuf *secret = NULL;
+	size_t secret_len;
+	EC_POINT *pub;
+	EC_KEY *eckey = NULL;
+
+	x = BN_bin2bn(key, inc_y ? len / 2 : len, NULL);
+	pub = EC_POINT_new(ecdh->ec->group);
+	if (!x || !pub)
+		goto fail;
+
+	if (inc_y) {
+		y = BN_bin2bn(key + len / 2, len / 2, NULL);
+		if (!y)
+			goto fail;
+		if (!EC_POINT_set_affine_coordinates_GFp(ecdh->ec->group, pub,
+							 x, y,
+							 ecdh->ec->bnctx)) {
+			wpa_printf(MSG_ERROR,
+				   "OpenSSL: EC_POINT_set_affine_coordinates_GFp failed: %s",
+				   ERR_error_string(ERR_get_error(), NULL));
+			goto fail;
+		}
+	} else if (!EC_POINT_set_compressed_coordinates_GFp(ecdh->ec->group,
+							    pub, x, 0,
+							    ecdh->ec->bnctx)) {
+		wpa_printf(MSG_ERROR,
+			   "OpenSSL: EC_POINT_set_compressed_coordinates_GFp failed: %s",
+			   ERR_error_string(ERR_get_error(), NULL));
+		goto fail;
+	}
+
+	if (!EC_POINT_is_on_curve(ecdh->ec->group, pub, ecdh->ec->bnctx)) {
+		wpa_printf(MSG_ERROR,
+			   "OpenSSL: ECDH peer public key is not on curve");
+		goto fail;
+	}
+
+	eckey = EC_KEY_new_by_curve_name(ecdh->ec->nid);
+	if (!eckey || EC_KEY_set_public_key(eckey, pub) != 1) {
+		wpa_printf(MSG_ERROR,
+			   "OpenSSL: EC_KEY_set_public_key failed: %s",
+			   ERR_error_string(ERR_get_error(), NULL));
+		goto fail;
+	}
+
+	peerkey = EVP_PKEY_new();
+	if (!peerkey || EVP_PKEY_set1_EC_KEY(peerkey, eckey) != 1)
+		goto fail;
+
+	ctx = EVP_PKEY_CTX_new(ecdh->pkey, NULL);
+	if (!ctx || EVP_PKEY_derive_init(ctx) != 1 ||
+	    EVP_PKEY_derive_set_peer(ctx, peerkey) != 1 ||
+	    EVP_PKEY_derive(ctx, NULL, &secret_len) != 1) {
+		wpa_printf(MSG_ERROR,
+			   "OpenSSL: EVP_PKEY_derive(1) failed: %s",
+			   ERR_error_string(ERR_get_error(), NULL));
+		goto fail;
+	}
+
+	secret = wpabuf_alloc(secret_len);
+	if (!secret)
+		goto fail;
+	if (EVP_PKEY_derive(ctx, wpabuf_put(secret, secret_len),
+			    &secret_len) != 1) {
+		wpa_printf(MSG_ERROR,
+			   "OpenSSL: EVP_PKEY_derive(2) failed: %s",
+			   ERR_error_string(ERR_get_error(), NULL));
+		goto fail;
+	}
+
+done:
+	BN_free(x);
+	BN_free(y);
+	EC_KEY_free(eckey);
+	EC_POINT_free(pub);
+	EVP_PKEY_CTX_free(ctx);
+	EVP_PKEY_free(peerkey);
+	return secret;
+fail:
+	wpabuf_free(secret);
+	secret = NULL;
+	goto done;
+}
+
+
+void crypto_ecdh_deinit(struct crypto_ecdh *ecdh)
+{
+	if (ecdh) {
+		crypto_ec_deinit(ecdh->ec);
+		EVP_PKEY_free(ecdh->pkey);
+		os_free(ecdh);
+	}
+}
+
 #endif /* CONFIG_ECC */