Branch data Line data Source code
1 : : /* $OpenBSD: kexc25519s.c,v 1.4 2014/01/12 08:13:13 djm Exp $ */
2 : : /*
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 : : * modification, are permitted provided that the following conditions
8 : : * are met:
9 : : * 1. Redistributions of source code must retain the above copyright
10 : : * notice, this list of conditions and the following disclaimer.
11 : : * 2. Redistributions in binary form must reproduce the above copyright
12 : : * notice, this list of conditions and the following disclaimer in the
13 : : * documentation and/or other materials provided with the distribution.
14 : : *
15 : : * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
16 : : * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
17 : : * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
18 : : * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
19 : : * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
20 : : * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
21 : : * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
22 : : * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
23 : : * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
24 : : * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
25 : : */
26 : :
27 : : #include "includes.h"
28 : :
29 : : #include <sys/types.h>
30 : : #include <string.h>
31 : : #include <signal.h>
32 : :
33 : : #include "xmalloc.h"
34 : : #include "buffer.h"
35 : : #include "key.h"
36 : : #include "cipher.h"
37 : : #include "kex.h"
38 : : #include "log.h"
39 : : #include "packet.h"
40 : : #include "ssh2.h"
41 : :
42 : : void
43 : 663 : kexc25519_server(Kex *kex)
44 : : {
45 : : Key *server_host_private, *server_host_public;
46 : 663 : u_char *server_host_key_blob = NULL, *signature = NULL;
47 : : u_char server_key[CURVE25519_SIZE];
48 : 663 : u_char *client_pubkey = NULL;
49 : : u_char server_pubkey[CURVE25519_SIZE];
50 : : u_char *hash;
51 : : u_int slen, sbloblen, hashlen;
52 : : Buffer shared_secret;
53 : :
54 : : /* generate private key */
55 : 663 : kexc25519_keygen(server_key, server_pubkey);
56 : : #ifdef DEBUG_KEXECDH
57 : : dump_digest("server private key:", server_key, sizeof(server_key));
58 : : #endif
59 : :
60 [ + - ][ - + ]: 663 : if (kex->load_host_public_key == NULL ||
61 : 663 : kex->load_host_private_key == NULL)
62 : 0 : fatal("Cannot load hostkey");
63 : 663 : server_host_public = kex->load_host_public_key(kex->hostkey_type);
64 [ - + ]: 663 : if (server_host_public == NULL)
65 : 0 : fatal("Unsupported hostkey type %d", kex->hostkey_type);
66 : 663 : server_host_private = kex->load_host_private_key(kex->hostkey_type);
67 : :
68 : 663 : debug("expecting SSH2_MSG_KEX_ECDH_INIT");
69 : 663 : packet_read_expect(SSH2_MSG_KEX_ECDH_INIT);
70 : 663 : client_pubkey = packet_get_string(&slen);
71 [ - + ]: 663 : if (slen != CURVE25519_SIZE)
72 : 0 : fatal("Incorrect size for server Curve25519 pubkey: %d", slen);
73 [ - + ]: 663 : packet_check_eom();
74 : :
75 : : #ifdef DEBUG_KEXECDH
76 : : dump_digest("client public key:", client_pubkey, CURVE25519_SIZE);
77 : : #endif
78 : :
79 : 663 : buffer_init(&shared_secret);
80 : 663 : kexc25519_shared_key(server_key, client_pubkey, &shared_secret);
81 : :
82 : : /* calc H */
83 : 663 : key_to_blob(server_host_public, &server_host_key_blob, &sbloblen);
84 : 1326 : kex_c25519_hash(
85 : : kex->hash_alg,
86 : : kex->client_version_string,
87 : : kex->server_version_string,
88 : 663 : buffer_ptr(&kex->peer), buffer_len(&kex->peer),
89 : 663 : buffer_ptr(&kex->my), buffer_len(&kex->my),
90 : : server_host_key_blob, sbloblen,
91 : : client_pubkey,
92 : : server_pubkey,
93 : 663 : buffer_ptr(&shared_secret), buffer_len(&shared_secret),
94 : : &hash, &hashlen
95 : : );
96 : :
97 : : /* save session id := H */
98 [ + + ]: 663 : if (kex->session_id == NULL) {
99 : 661 : kex->session_id_len = hashlen;
100 : 661 : kex->session_id = xmalloc(kex->session_id_len);
101 : 661 : memcpy(kex->session_id, hash, kex->session_id_len);
102 : : }
103 : :
104 : : /* sign H */
105 : 663 : kex->sign(server_host_private, server_host_public, &signature, &slen,
106 : : hash, hashlen);
107 : :
108 : : /* destroy_sensitive_data(); */
109 : :
110 : : /* send server hostkey, ECDH pubkey 'Q_S' and signed H */
111 : 663 : packet_start(SSH2_MSG_KEX_ECDH_REPLY);
112 : 663 : packet_put_string(server_host_key_blob, sbloblen);
113 : 663 : packet_put_string(server_pubkey, sizeof(server_pubkey));
114 : 663 : packet_put_string(signature, slen);
115 : 663 : packet_send();
116 : :
117 : 663 : free(signature);
118 : 663 : free(server_host_key_blob);
119 : : /* have keys, free server key */
120 : 663 : free(client_pubkey);
121 : :
122 : 1326 : kex_derive_keys(kex, hash, hashlen,
123 : 663 : buffer_ptr(&shared_secret), buffer_len(&shared_secret));
124 : 663 : buffer_free(&shared_secret);
125 : 663 : kex_finish(kex);
126 : 663 : }
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