Exemplo n.º 1
0
static int
input_kex_ecdh_init(int type, u_int32_t seq, struct ssh *ssh)
{
	struct kex *kex = ssh->kex;
	EC_POINT *client_public;
	EC_KEY *server_key = NULL;
	const EC_GROUP *group;
	const EC_POINT *public_key;
	BIGNUM *shared_secret = NULL;
	struct sshkey *server_host_private, *server_host_public;
	u_char *server_host_key_blob = NULL, *signature = NULL;
	u_char *kbuf = NULL;
	u_char hash[SSH_DIGEST_MAX_LENGTH];
	size_t slen, sbloblen;
	size_t klen = 0, hashlen;
	int r;

	if ((server_key = EC_KEY_new_by_curve_name(kex->ec_nid)) == NULL) {
		r = SSH_ERR_ALLOC_FAIL;
		goto out;
	}
	if (EC_KEY_generate_key(server_key) != 1) {
		r = SSH_ERR_LIBCRYPTO_ERROR;
		goto out;
	}
	group = EC_KEY_get0_group(server_key);

#ifdef DEBUG_KEXECDH
	fputs("server private key:\n", stderr);
	sshkey_dump_ec_key(server_key);
#endif

	if (kex->load_host_public_key == NULL ||
	    kex->load_host_private_key == NULL) {
		r = SSH_ERR_INVALID_ARGUMENT;
		goto out;
	}
	server_host_public = kex->load_host_public_key(kex->hostkey_type,
	    kex->hostkey_nid, ssh);
	server_host_private = kex->load_host_private_key(kex->hostkey_type,
	    kex->hostkey_nid, ssh);
	if (server_host_public == NULL) {
		r = SSH_ERR_NO_HOSTKEY_LOADED;
		goto out;
	}
	if ((client_public = EC_POINT_new(group)) == NULL) {
		r = SSH_ERR_ALLOC_FAIL;
		goto out;
	}
	if ((r = sshpkt_get_ec(ssh, client_public, group)) != 0 ||
	    (r = sshpkt_get_end(ssh)) != 0)
		goto out;

#ifdef DEBUG_KEXECDH
	fputs("client public key:\n", stderr);
	sshkey_dump_ec_point(group, client_public);
#endif
	if (sshkey_ec_validate_public(group, client_public) != 0) {
		sshpkt_disconnect(ssh, "invalid client public key");
		r = SSH_ERR_MESSAGE_INCOMPLETE;
		goto out;
	}

	/* Calculate shared_secret */
	klen = (EC_GROUP_get_degree(group) + 7) / 8;
	if ((kbuf = malloc(klen)) == NULL ||
	    (shared_secret = BN_new()) == NULL) {
		r = SSH_ERR_ALLOC_FAIL;
		goto out;
	}
	if (ECDH_compute_key(kbuf, klen, client_public,
	    server_key, NULL) != (int)klen ||
	    BN_bin2bn(kbuf, klen, shared_secret) == NULL) {
		r = SSH_ERR_LIBCRYPTO_ERROR;
		goto out;
	}

#ifdef DEBUG_KEXECDH
	dump_digest("shared secret", kbuf, klen);
#endif
	/* calc H */
	if ((r = sshkey_to_blob(server_host_public, &server_host_key_blob,
	    &sbloblen)) != 0)
		goto out;
	hashlen = sizeof(hash);
	if ((r = kex_ecdh_hash(
	    kex->hash_alg,
	    group,
	    kex->client_version_string,
	    kex->server_version_string,
	    sshbuf_ptr(kex->peer), sshbuf_len(kex->peer),
	    sshbuf_ptr(kex->my), sshbuf_len(kex->my),
	    server_host_key_blob, sbloblen,
	    client_public,
	    EC_KEY_get0_public_key(server_key),
	    shared_secret,
	    hash, &hashlen)) != 0)
		goto out;

	/* save session id := H */
	if (kex->session_id == NULL) {
		kex->session_id_len = hashlen;
		kex->session_id = malloc(kex->session_id_len);
		if (kex->session_id == NULL) {
			r = SSH_ERR_ALLOC_FAIL;
			goto out;
		}
		memcpy(kex->session_id, hash, kex->session_id_len);
	}

	/* sign H */
	if ((r = kex->sign(server_host_private, server_host_public, &signature,
	     &slen, hash, hashlen, kex->hostkey_alg, ssh->compat)) < 0)
		goto out;

	/* destroy_sensitive_data(); */

	public_key = EC_KEY_get0_public_key(server_key);
	/* send server hostkey, ECDH pubkey 'Q_S' and signed H */
	if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_ECDH_REPLY)) != 0 ||
	    (r = sshpkt_put_string(ssh, server_host_key_blob, sbloblen)) != 0 ||
	    (r = sshpkt_put_ec(ssh, public_key, group)) != 0 ||
	    (r = sshpkt_put_string(ssh, signature, slen)) != 0 ||
	    (r = sshpkt_send(ssh)) != 0)
		goto out;

	if ((r = kex_derive_keys_bn(ssh, hash, hashlen, shared_secret)) == 0)
		r = kex_send_newkeys(ssh);
 out:
	explicit_bzero(hash, sizeof(hash));
	if (kex->ec_client_key) {
		EC_KEY_free(kex->ec_client_key);
		kex->ec_client_key = NULL;
	}
	if (server_key)
		EC_KEY_free(server_key);
	if (kbuf) {
		explicit_bzero(kbuf, klen);
		free(kbuf);
	}
	if (shared_secret)
		BN_clear_free(shared_secret);
	free(server_host_key_blob);
	free(signature);
	return r;
}
Exemplo n.º 2
0
void
kexecdh_client(Kex *kex)
{
	EC_KEY *client_key;
	EC_POINT *server_public;
	const EC_GROUP *group;
	BIGNUM *shared_secret;
	Key *server_host_key;
	u_char *server_host_key_blob = NULL, *signature = NULL;
	u_char *kbuf, *hash;
	u_int klen, slen, sbloblen, hashlen;

	if ((client_key = EC_KEY_new_by_curve_name(kex->ec_nid)) == NULL)
		fatal("%s: EC_KEY_new_by_curve_name failed", __func__);
	if (EC_KEY_generate_key(client_key) != 1)
		fatal("%s: EC_KEY_generate_key failed", __func__);
	group = EC_KEY_get0_group(client_key);

	packet_start(SSH2_MSG_KEX_ECDH_INIT);
	packet_put_ecpoint(group, EC_KEY_get0_public_key(client_key));
	packet_send();
	debug("sending SSH2_MSG_KEX_ECDH_INIT");

#ifdef DEBUG_KEXECDH
	fputs("client private key:\n", stderr);
	key_dump_ec_key(client_key);
#endif

	debug("expecting SSH2_MSG_KEX_ECDH_REPLY");
	packet_read_expect(SSH2_MSG_KEX_ECDH_REPLY);

	/* hostkey */
	server_host_key_blob = packet_get_string(&sbloblen);
	server_host_key = key_from_blob(server_host_key_blob, sbloblen);
	if (server_host_key == NULL)
		fatal("cannot decode server_host_key_blob");
	if (server_host_key->type != kex->hostkey_type)
		fatal("type mismatch for decoded server_host_key_blob");
	if (kex->verify_host_key == NULL)
		fatal("cannot verify server_host_key");
	if (kex->verify_host_key(server_host_key) == -1)
		fatal("server_host_key verification failed");

	/* Q_S, server public key */
	if ((server_public = EC_POINT_new(group)) == NULL)
		fatal("%s: EC_POINT_new failed", __func__);
	packet_get_ecpoint(group, server_public);

	if (key_ec_validate_public(group, server_public) != 0)
		fatal("%s: invalid server public key", __func__);

#ifdef DEBUG_KEXECDH
	fputs("server public key:\n", stderr);
	key_dump_ec_point(group, server_public);
#endif

	/* signed H */
	signature = packet_get_string(&slen);
	packet_check_eom();

	klen = (EC_GROUP_get_degree(group) + 7) / 8;
	kbuf = xmalloc(klen);
	if (ECDH_compute_key(kbuf, klen, server_public,
	    client_key, NULL) != (int)klen)
		fatal("%s: ECDH_compute_key failed", __func__);

#ifdef DEBUG_KEXECDH
	dump_digest("shared secret", kbuf, klen);
#endif
	if ((shared_secret = BN_new()) == NULL)
		fatal("%s: BN_new failed", __func__);
	if (BN_bin2bn(kbuf, klen, shared_secret) == NULL)
		fatal("%s: BN_bin2bn failed", __func__);
	memset(kbuf, 0, klen);
	free(kbuf);

	/* calc and verify H */
	kex_ecdh_hash(
	    kex->evp_md,
	    group,
	    kex->client_version_string,
	    kex->server_version_string,
	    buffer_ptr(&kex->my), buffer_len(&kex->my),
	    buffer_ptr(&kex->peer), buffer_len(&kex->peer),
	    server_host_key_blob, sbloblen,
	    EC_KEY_get0_public_key(client_key),
	    server_public,
	    shared_secret,
	    &hash, &hashlen
	);
	free(server_host_key_blob);
	EC_POINT_clear_free(server_public);
	EC_KEY_free(client_key);

	if (key_verify(server_host_key, signature, slen, hash, hashlen) != 1)
		fatal("key_verify failed for server_host_key");
	key_free(server_host_key);
	free(signature);

	/* save session id */
	if (kex->session_id == NULL) {
		kex->session_id_len = hashlen;
		kex->session_id = xmalloc(kex->session_id_len);
		memcpy(kex->session_id, hash, kex->session_id_len);
	}

	kex_derive_keys(kex, hash, hashlen, shared_secret);
	BN_clear_free(shared_secret);
	kex_finish(kex);
}
Exemplo n.º 3
0
static int
input_kex_ecdh_reply(int type, u_int32_t seq, void *ctxt)
{
	struct ssh *ssh = ctxt;
	struct kex *kex = ssh->kex;
	const EC_GROUP *group;
	EC_POINT *server_public = NULL;
	EC_KEY *client_key;
	BIGNUM *shared_secret = NULL;
	struct sshkey *server_host_key = NULL;
	u_char *server_host_key_blob = NULL, *signature = NULL;
	u_char *kbuf = NULL;
	u_char hash[SSH_DIGEST_MAX_LENGTH];
	size_t slen, sbloblen;
	size_t klen = 0, hashlen;
	int r;

	if (kex->verify_host_key == NULL) {
		r = SSH_ERR_INVALID_ARGUMENT;
		goto out;
	}
	group = kex->ec_group;
	client_key = kex->ec_client_key;

	/* hostkey */
	if ((r = sshpkt_get_string(ssh, &server_host_key_blob,
	    &sbloblen)) != 0 ||
	    (r = sshkey_from_blob(server_host_key_blob, sbloblen,
	    &server_host_key)) != 0)
		goto out;
	if (server_host_key->type != kex->hostkey_type ||
	    (kex->hostkey_type == KEY_ECDSA &&
	    server_host_key->ecdsa_nid != kex->hostkey_nid)) {
		r = SSH_ERR_KEY_TYPE_MISMATCH;
		goto out;
	}
	if (kex->verify_host_key(server_host_key, ssh) == -1) {
		r = SSH_ERR_SIGNATURE_INVALID;
		goto out;
	}

	/* Q_S, server public key */
	/* signed H */
	if ((server_public = EC_POINT_new(group)) == NULL) {
		r = SSH_ERR_ALLOC_FAIL;
		goto out;
	}
	if ((r = sshpkt_get_ec(ssh, server_public, group)) != 0 ||
	    (r = sshpkt_get_string(ssh, &signature, &slen)) != 0 ||
	    (r = sshpkt_get_end(ssh)) != 0)
		goto out;

#ifdef DEBUG_KEXECDH
	fputs("server public key:\n", stderr);
	sshkey_dump_ec_point(group, server_public);
#endif
	if (sshkey_ec_validate_public(group, server_public) != 0) {
		sshpkt_disconnect(ssh, "invalid server public key");
		r = SSH_ERR_MESSAGE_INCOMPLETE;
		goto out;
	}

	klen = (EC_GROUP_get_degree(group) + 7) / 8;
	if ((kbuf = malloc(klen)) == NULL ||
	    (shared_secret = BN_new()) == NULL) {
		r = SSH_ERR_ALLOC_FAIL;
		goto out;
	}
	if (ECDH_compute_key(kbuf, klen, server_public,
	    client_key, NULL) != (int)klen ||
	    BN_bin2bn(kbuf, klen, shared_secret) == NULL) {
		r = SSH_ERR_LIBCRYPTO_ERROR;
		goto out;
	}

#ifdef DEBUG_KEXECDH
	dump_digest("shared secret", kbuf, klen);
#endif
	/* calc and verify H */
	hashlen = sizeof(hash);
	if ((r = kex_ecdh_hash(
	    kex->hash_alg,
	    group,
	    kex->client_version_string,
	    kex->server_version_string,
	    sshbuf_ptr(kex->my), sshbuf_len(kex->my),
	    sshbuf_ptr(kex->peer), sshbuf_len(kex->peer),
	    server_host_key_blob, sbloblen,
	    EC_KEY_get0_public_key(client_key),
	    server_public,
	    shared_secret,
	    hash, &hashlen)) != 0)
		goto out;

	if ((r = sshkey_verify(server_host_key, signature, slen, hash,
	    hashlen, ssh->compat)) != 0)
		goto out;

	/* save session id */
	if (kex->session_id == NULL) {
		kex->session_id_len = hashlen;
		kex->session_id = malloc(kex->session_id_len);
		if (kex->session_id == NULL) {
			r = SSH_ERR_ALLOC_FAIL;
			goto out;
		}
		memcpy(kex->session_id, hash, kex->session_id_len);
	}

	if ((r = kex_derive_keys_bn(ssh, hash, hashlen, shared_secret)) == 0)
		r = kex_send_newkeys(ssh);
 out:
	explicit_bzero(hash, sizeof(hash));
	if (kex->ec_client_key) {
		EC_KEY_free(kex->ec_client_key);
		kex->ec_client_key = NULL;
	}
	if (server_public)
		EC_POINT_clear_free(server_public);
	if (kbuf) {
		explicit_bzero(kbuf, klen);
		free(kbuf);
	}
	if (shared_secret)
		BN_clear_free(shared_secret);
	sshkey_free(server_host_key);
	free(server_host_key_blob);
	free(signature);
	return r;
}
Exemplo n.º 4
0
void
kexecdh_server(Kex *kex)
{
	EC_POINT *client_public;
	EC_KEY *server_key;
	const EC_GROUP *group;
	BIGNUM *shared_secret;
	Key *server_host_private, *server_host_public;
	u_char *server_host_key_blob = NULL, *signature = NULL;
	u_char *kbuf, *hash;
	u_int klen, slen, sbloblen, hashlen;
	int curve_nid;

	if ((curve_nid = kex_ecdh_name_to_nid(kex->name)) == -1)
		fatal("%s: unsupported ECDH curve \"%s\"", __func__, kex->name);
	if ((server_key = EC_KEY_new_by_curve_name(curve_nid)) == NULL)
		fatal("%s: EC_KEY_new_by_curve_name failed", __func__);
	if (EC_KEY_generate_key(server_key) != 1)
		fatal("%s: EC_KEY_generate_key failed", __func__);
	group = EC_KEY_get0_group(server_key);

#ifdef DEBUG_KEXECDH
	fputs("server private key:\n", stderr);
	key_dump_ec_key(server_key);
#endif

	if (kex->load_host_public_key == NULL ||
	    kex->load_host_private_key == NULL)
		fatal("Cannot load hostkey");
	server_host_public = kex->load_host_public_key(kex->hostkey_type);
	if (server_host_public == NULL)
		fatal("Unsupported hostkey type %d", kex->hostkey_type);
	server_host_private = kex->load_host_private_key(kex->hostkey_type);
	if (server_host_private == NULL)
		fatal("Missing private key for hostkey type %d",
		    kex->hostkey_type);

	debug("expecting SSH2_MSG_KEX_ECDH_INIT");
	packet_read_expect(SSH2_MSG_KEX_ECDH_INIT);
	if ((client_public = EC_POINT_new(group)) == NULL)
		fatal("%s: EC_POINT_new failed", __func__);
	packet_get_ecpoint(group, client_public);
	packet_check_eom();

	if (key_ec_validate_public(group, client_public) != 0)
		fatal("%s: invalid client public key", __func__);

#ifdef DEBUG_KEXECDH
	fputs("client public key:\n", stderr);
	key_dump_ec_point(group, client_public);
#endif

	/* Calculate shared_secret */
	klen = (EC_GROUP_get_degree(group) + 7) / 8;
	kbuf = xmalloc(klen);
	if (ECDH_compute_key(kbuf, klen, client_public,
	    server_key, NULL) != (int)klen)
		fatal("%s: ECDH_compute_key failed", __func__);

#ifdef DEBUG_KEXDH
	dump_digest("shared secret", kbuf, klen);
#endif
	if ((shared_secret = BN_new()) == NULL)
		fatal("%s: BN_new failed", __func__);
	if (BN_bin2bn(kbuf, klen, shared_secret) == NULL)
		fatal("%s: BN_bin2bn failed", __func__);
	memset(kbuf, 0, klen);
	xfree(kbuf);

	/* calc H */
	key_to_blob(server_host_public, &server_host_key_blob, &sbloblen);
	kex_ecdh_hash(
	    kex->evp_md,
	    group,
	    kex->client_version_string,
	    kex->server_version_string,
	    buffer_ptr(&kex->peer), buffer_len(&kex->peer),
	    buffer_ptr(&kex->my), buffer_len(&kex->my),
	    server_host_key_blob, sbloblen,
	    client_public,
	    EC_KEY_get0_public_key(server_key),
	    shared_secret,
	    &hash, &hashlen
	);
	EC_POINT_clear_free(client_public);

	/* save session id := H */
	if (kex->session_id == NULL) {
		kex->session_id_len = hashlen;
		kex->session_id = xmalloc(kex->session_id_len);
		memcpy(kex->session_id, hash, kex->session_id_len);
	}

	/* sign H */
	if (PRIVSEP(key_sign(server_host_private, &signature, &slen,
	    hash, hashlen)) < 0)
		fatal("kexdh_server: key_sign failed");

	/* destroy_sensitive_data(); */

	/* send server hostkey, ECDH pubkey 'Q_S' and signed H */
	packet_start(SSH2_MSG_KEX_ECDH_REPLY);
	packet_put_string(server_host_key_blob, sbloblen);
	packet_put_ecpoint(group, EC_KEY_get0_public_key(server_key));
	packet_put_string(signature, slen);
	packet_send();

	xfree(signature);
	xfree(server_host_key_blob);
	/* have keys, free server key */
	EC_KEY_free(server_key);

	kex_derive_keys(kex, hash, hashlen, shared_secret);
	BN_clear_free(shared_secret);
	kex_finish(kex);
}