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Damien Miller91b580e2014-01-12 19:21:22 +11001/* $OpenBSD: kexc25519c.c,v 1.4 2014/01/12 08:13:13 djm Exp $ */
Damien Miller094003f2013-11-04 22:59:27 +11002/*
3 * Copyright (c) 2001 Markus Friedl. All rights reserved.
4 * Copyright (c) 2010 Damien Miller. All rights reserved.
5 * Copyright (c) 2013 Aris Adamantiadis. All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 * notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
17 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
18 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
19 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
21 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
22 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
23 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
24 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
25 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
26 */
27
28#include "includes.h"
29
30#include <sys/types.h>
31
32#include <stdio.h>
33#include <string.h>
34#include <signal.h>
35
36#include "xmalloc.h"
37#include "buffer.h"
38#include "key.h"
39#include "cipher.h"
40#include "kex.h"
41#include "log.h"
42#include "packet.h"
43#include "ssh2.h"
44
45void
46kexc25519_client(Kex *kex)
47{
Damien Miller094003f2013-11-04 22:59:27 +110048 Key *server_host_key;
49 u_char client_key[CURVE25519_SIZE];
50 u_char client_pubkey[CURVE25519_SIZE];
51 u_char *server_pubkey = NULL;
52 u_char *server_host_key_blob = NULL, *signature = NULL;
53 u_char *hash;
54 u_int slen, sbloblen, hashlen;
Damien Miller91b580e2014-01-12 19:21:22 +110055 Buffer shared_secret;
Damien Miller094003f2013-11-04 22:59:27 +110056
57 kexc25519_keygen(client_key, client_pubkey);
58
59 packet_start(SSH2_MSG_KEX_ECDH_INIT);
60 packet_put_string(client_pubkey, sizeof(client_pubkey));
61 packet_send();
62 debug("sending SSH2_MSG_KEX_ECDH_INIT");
63
64#ifdef DEBUG_KEXECDH
65 dump_digest("client private key:", client_key, sizeof(client_key));
66#endif
67
68 debug("expecting SSH2_MSG_KEX_ECDH_REPLY");
69 packet_read_expect(SSH2_MSG_KEX_ECDH_REPLY);
70
71 /* hostkey */
72 server_host_key_blob = packet_get_string(&sbloblen);
73 server_host_key = key_from_blob(server_host_key_blob, sbloblen);
74 if (server_host_key == NULL)
75 fatal("cannot decode server_host_key_blob");
76 if (server_host_key->type != kex->hostkey_type)
77 fatal("type mismatch for decoded server_host_key_blob");
78 if (kex->verify_host_key == NULL)
79 fatal("cannot verify server_host_key");
80 if (kex->verify_host_key(server_host_key) == -1)
81 fatal("server_host_key verification failed");
82
83 /* Q_S, server public key */
84 server_pubkey = packet_get_string(&slen);
85 if (slen != CURVE25519_SIZE)
86 fatal("Incorrect size for server Curve25519 pubkey: %d", slen);
87
88#ifdef DEBUG_KEXECDH
89 dump_digest("server public key:", server_pubkey, CURVE25519_SIZE);
90#endif
91
92 /* signed H */
93 signature = packet_get_string(&slen);
94 packet_check_eom();
95
Damien Miller91b580e2014-01-12 19:21:22 +110096 buffer_init(&shared_secret);
97 kexc25519_shared_key(client_key, server_pubkey, &shared_secret);
Damien Miller094003f2013-11-04 22:59:27 +110098
99 /* calc and verify H */
100 kex_c25519_hash(
Damien Millerb3051d02014-01-10 10:58:53 +1100101 kex->hash_alg,
Damien Miller094003f2013-11-04 22:59:27 +1100102 kex->client_version_string,
103 kex->server_version_string,
104 buffer_ptr(&kex->my), buffer_len(&kex->my),
105 buffer_ptr(&kex->peer), buffer_len(&kex->peer),
106 server_host_key_blob, sbloblen,
107 client_pubkey,
108 server_pubkey,
Damien Miller91b580e2014-01-12 19:21:22 +1100109 buffer_ptr(&shared_secret), buffer_len(&shared_secret),
Damien Miller094003f2013-11-04 22:59:27 +1100110 &hash, &hashlen
111 );
112 free(server_host_key_blob);
113 free(server_pubkey);
114 if (key_verify(server_host_key, signature, slen, hash, hashlen) != 1)
115 fatal("key_verify failed for server_host_key");
116 key_free(server_host_key);
117 free(signature);
118
119 /* save session id */
120 if (kex->session_id == NULL) {
121 kex->session_id_len = hashlen;
122 kex->session_id = xmalloc(kex->session_id_len);
123 memcpy(kex->session_id, hash, kex->session_id_len);
124 }
Damien Miller91b580e2014-01-12 19:21:22 +1100125 kex_derive_keys(kex, hash, hashlen,
126 buffer_ptr(&shared_secret), buffer_len(&shared_secret));
127 buffer_free(&shared_secret);
Damien Miller094003f2013-11-04 22:59:27 +1100128 kex_finish(kex);
129}