1 /* $OpenBSD: kexc25519c.c,v 1.7 2015/01/26 06:10:03 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 * 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 "sshkey.h"
37 #include "cipher.h"
38 #include "kex.h"
39 #include "log.h"
40 #include "packet.h"
41 #include "ssh2.h"
42 #include "sshbuf.h"
43 #include "digest.h"
44 #include "ssherr.h"
45
46 static int
47 input_kex_c25519_reply(int type, u_int32_t seq, void *ctxt);
48
49 int
kexc25519_client(struct ssh * ssh)50 kexc25519_client(struct ssh *ssh)
51 {
52 struct kex *kex = ssh->kex;
53 int r;
54
55 kexc25519_keygen(kex->c25519_client_key, kex->c25519_client_pubkey);
56 #ifdef DEBUG_KEXECDH
57 dump_digest("client private key:", kex->c25519_client_key,
58 sizeof(kex->c25519_client_key));
59 #endif
60 if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_ECDH_INIT)) != 0 ||
61 (r = sshpkt_put_string(ssh, kex->c25519_client_pubkey,
62 sizeof(kex->c25519_client_pubkey))) != 0 ||
63 (r = sshpkt_send(ssh)) != 0)
64 return r;
65
66 debug("expecting SSH2_MSG_KEX_ECDH_REPLY");
67 ssh_dispatch_set(ssh, SSH2_MSG_KEX_ECDH_REPLY, &input_kex_c25519_reply);
68 return 0;
69 }
70
71 static int
input_kex_c25519_reply(int type,u_int32_t seq,void * ctxt)72 input_kex_c25519_reply(int type, u_int32_t seq, void *ctxt)
73 {
74 struct ssh *ssh = ctxt;
75 struct kex *kex = ssh->kex;
76 struct sshkey *server_host_key = NULL;
77 struct sshbuf *shared_secret = NULL;
78 u_char *server_pubkey = NULL;
79 u_char *server_host_key_blob = NULL, *signature = NULL;
80 u_char hash[SSH_DIGEST_MAX_LENGTH];
81 size_t slen, pklen, sbloblen, hashlen;
82 int r;
83
84 if (kex->verify_host_key == NULL) {
85 r = SSH_ERR_INVALID_ARGUMENT;
86 goto out;
87 }
88
89 /* hostkey */
90 if ((r = sshpkt_get_string(ssh, &server_host_key_blob,
91 &sbloblen)) != 0 ||
92 (r = sshkey_from_blob(server_host_key_blob, sbloblen,
93 &server_host_key)) != 0)
94 goto out;
95 if (server_host_key->type != kex->hostkey_type ||
96 (kex->hostkey_type == KEY_ECDSA &&
97 server_host_key->ecdsa_nid != kex->hostkey_nid)) {
98 r = SSH_ERR_KEY_TYPE_MISMATCH;
99 goto out;
100 }
101 if (kex->verify_host_key(server_host_key, ssh) == -1) {
102 r = SSH_ERR_SIGNATURE_INVALID;
103 goto out;
104 }
105
106 /* Q_S, server public key */
107 /* signed H */
108 if ((r = sshpkt_get_string(ssh, &server_pubkey, &pklen)) != 0 ||
109 (r = sshpkt_get_string(ssh, &signature, &slen)) != 0 ||
110 (r = sshpkt_get_end(ssh)) != 0)
111 goto out;
112 if (pklen != CURVE25519_SIZE) {
113 r = SSH_ERR_SIGNATURE_INVALID;
114 goto out;
115 }
116
117 #ifdef DEBUG_KEXECDH
118 dump_digest("server public key:", server_pubkey, CURVE25519_SIZE);
119 #endif
120
121 if ((shared_secret = sshbuf_new()) == NULL) {
122 r = SSH_ERR_ALLOC_FAIL;
123 goto out;
124 }
125 if ((r = kexc25519_shared_key(kex->c25519_client_key, server_pubkey,
126 shared_secret)) < 0)
127 goto out;
128
129 /* calc and verify H */
130 hashlen = sizeof(hash);
131 if ((r = kex_c25519_hash(
132 kex->hash_alg,
133 kex->client_version_string,
134 kex->server_version_string,
135 sshbuf_ptr(kex->my), sshbuf_len(kex->my),
136 sshbuf_ptr(kex->peer), sshbuf_len(kex->peer),
137 server_host_key_blob, sbloblen,
138 kex->c25519_client_pubkey,
139 server_pubkey,
140 sshbuf_ptr(shared_secret), sshbuf_len(shared_secret),
141 hash, &hashlen)) < 0)
142 goto out;
143
144 if ((r = sshkey_verify(server_host_key, signature, slen, hash, hashlen,
145 ssh->compat)) != 0)
146 goto out;
147
148 /* save session id */
149 if (kex->session_id == NULL) {
150 kex->session_id_len = hashlen;
151 kex->session_id = malloc(kex->session_id_len);
152 if (kex->session_id == NULL) {
153 r = SSH_ERR_ALLOC_FAIL;
154 goto out;
155 }
156 memcpy(kex->session_id, hash, kex->session_id_len);
157 }
158
159 if ((r = kex_derive_keys(ssh, hash, hashlen, shared_secret)) == 0)
160 r = kex_send_newkeys(ssh);
161 out:
162 explicit_bzero(hash, sizeof(hash));
163 explicit_bzero(kex->c25519_client_key, sizeof(kex->c25519_client_key));
164 free(server_host_key_blob);
165 free(server_pubkey);
166 free(signature);
167 sshkey_free(server_host_key);
168 sshbuf_free(shared_secret);
169 return r;
170 }
171