text: /* $OpenBSD: kexc25519c.c,v 1.7 2015/01/26 06:10:03 djm Exp $ */
  /*
   * Copyright (c) 2001 Markus Friedl.  All rights reserved.
   * Copyright (c) 2010 Damien Miller.  All rights reserved.
   * Copyright (c) 2013 Aris Adamantiadis.  All rights reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   * 1. Redistributions of source code must retain the above copyright
   *    notice, this list of conditions and the following disclaimer.
   * 2. Redistributions in binary form must reproduce the above copyright
   *    notice, this list of conditions and the following disclaimer in the
   *    documentation and/or other materials provided with the distribution.
   *
   * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
   * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
   * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
   * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
   * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
   * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
   * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
   * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
   * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   */
  
  #include "includes.h"
  
  #include <sys/types.h>
  
  #include <stdio.h>
  #include <string.h>
  #include <signal.h>
  
  #include "sshkey.h"
  #include "cipher.h"
  #include "kex.h"
  #include "log.h"
  #include "packet.h"
  #include "ssh2.h"
  #include "sshbuf.h"
  #include "digest.h"
  #include "ssherr.h"
  
  static int
  input_kex_c25519_reply(int type, u_int32_t seq, void *ctxt);
  
  int
  kexc25519_client(struct ssh *ssh)
  {
  	struct kex *kex = ssh->kex;
  	int r;
  
  	kexc25519_keygen(kex->c25519_client_key, kex->c25519_client_pubkey);
  #ifdef DEBUG_KEXECDH
  	dump_digest("client private key:", kex->c25519_client_key,
  	    sizeof(kex->c25519_client_key));
  #endif
  	if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_ECDH_INIT)) != 0 ||
  	    (r = sshpkt_put_string(ssh, kex->c25519_client_pubkey,
  	    sizeof(kex->c25519_client_pubkey))) != 0 ||
  	    (r = sshpkt_send(ssh)) != 0)
  		return r;
  
  	debug("expecting SSH2_MSG_KEX_ECDH_REPLY");
  	ssh_dispatch_set(ssh, SSH2_MSG_KEX_ECDH_REPLY, &input_kex_c25519_reply);
  	return 0;
  }
  
  static int
  input_kex_c25519_reply(int type, u_int32_t seq, void *ctxt)
  {
  	struct ssh *ssh = ctxt;
  	struct kex *kex = ssh->kex;
  	struct sshkey *server_host_key = NULL;
  	struct sshbuf *shared_secret = NULL;
  	u_char *server_pubkey = NULL;
  	u_char *server_host_key_blob = NULL, *signature = NULL;
  	u_char hash[SSH_DIGEST_MAX_LENGTH];
  	size_t slen, pklen, sbloblen, hashlen;
  	int r;
  
  	if (kex->verify_host_key == NULL) {
  		r = SSH_ERR_INVALID_ARGUMENT;
  		goto out;
  	}
  
  	/* 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 ((r = sshpkt_get_string(ssh, &server_pubkey, &pklen)) != 0 ||
  	    (r = sshpkt_get_string(ssh, &signature, &slen)) != 0 ||
  	    (r = sshpkt_get_end(ssh)) != 0)
  		goto out;
  	if (pklen != CURVE25519_SIZE) {
  		r = SSH_ERR_SIGNATURE_INVALID;
  		goto out;
  	}
  
  #ifdef DEBUG_KEXECDH
  	dump_digest("server public key:", server_pubkey, CURVE25519_SIZE);
  #endif
  
  	if ((shared_secret = sshbuf_new()) == NULL) {
  		r = SSH_ERR_ALLOC_FAIL;
  		goto out;
  	}
  	if ((r = kexc25519_shared_key(kex->c25519_client_key, server_pubkey,
  	    shared_secret)) < 0)
  		goto out;
  
  	/* calc and verify H */
  	hashlen = sizeof(hash);
  	if ((r = kex_c25519_hash(
  	    kex->hash_alg,
  	    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,
  	    kex->c25519_client_pubkey,
  	    server_pubkey,
  	    sshbuf_ptr(shared_secret), sshbuf_len(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(ssh, hash, hashlen, shared_secret)) == 0)
  		r = kex_send_newkeys(ssh);
  out:
  	explicit_bzero(hash, sizeof(hash));
  	explicit_bzero(kex->c25519_client_key, sizeof(kex->c25519_client_key));
  	free(server_host_key_blob);
  	free(server_pubkey);
  	free(signature);
  	sshkey_free(server_host_key);
  	sshbuf_free(shared_secret);
  	return r;
  }
  