1 /* $OpenBSD: kexgexs.c,v 1.19 2014/02/02 03:44:31 djm Exp $ */
3 * Copyright (c) 2000 Niels Provos. All rights reserved.
4 * Copyright (c) 2001 Markus Friedl. All rights reserved.
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
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.
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.
29 #include <sys/param.h>
36 #include <openssl/dh.h>
51 #include "monitor_wrap.h"
54 kexgex_server(Kex *kex)
56 BIGNUM *shared_secret = NULL, *dh_client_pub = NULL;
57 Key *server_host_public, *server_host_private;
59 u_char *kbuf, *hash, *signature = NULL, *server_host_key_blob = NULL;
60 u_int sbloblen, klen, slen, hashlen;
61 int omin = -1, min = -1, omax = -1, max = -1, onbits = -1, nbits = -1;
64 if (kex->load_host_public_key == NULL ||
65 kex->load_host_private_key == NULL)
66 fatal("Cannot load hostkey");
67 server_host_public = kex->load_host_public_key(kex->hostkey_type);
68 if (server_host_public == NULL)
69 fatal("Unsupported hostkey type %d", kex->hostkey_type);
70 server_host_private = kex->load_host_private_key(kex->hostkey_type);
74 case SSH2_MSG_KEX_DH_GEX_REQUEST:
75 debug("SSH2_MSG_KEX_DH_GEX_REQUEST received");
76 omin = min = packet_get_int();
77 onbits = nbits = packet_get_int();
78 omax = max = packet_get_int();
79 min = MAX(DH_GRP_MIN, min);
80 max = MIN(DH_GRP_MAX, max);
81 nbits = MAX(DH_GRP_MIN, nbits);
82 nbits = MIN(DH_GRP_MAX, nbits);
84 case SSH2_MSG_KEX_DH_GEX_REQUEST_OLD:
85 debug("SSH2_MSG_KEX_DH_GEX_REQUEST_OLD received");
86 onbits = nbits = packet_get_int();
87 /* unused for old GEX */
88 omin = min = DH_GRP_MIN;
89 omax = max = DH_GRP_MAX;
92 fatal("protocol error during kex, no DH_GEX_REQUEST: %d", type);
96 if (omax < omin || onbits < omin || omax < onbits)
97 fatal("DH_GEX_REQUEST, bad parameters: %d !< %d !< %d",
100 /* Contact privileged parent */
101 dh = PRIVSEP(choose_dh(min, nbits, max));
103 packet_disconnect("Protocol error: no matching DH grp found");
105 debug("SSH2_MSG_KEX_DH_GEX_GROUP sent");
106 packet_start(SSH2_MSG_KEX_DH_GEX_GROUP);
107 packet_put_bignum2(dh->p);
108 packet_put_bignum2(dh->g);
114 /* Compute our exchange value in parallel with the client */
115 dh_gen_key(dh, kex->we_need * 8);
117 debug("expecting SSH2_MSG_KEX_DH_GEX_INIT");
118 packet_read_expect(SSH2_MSG_KEX_DH_GEX_INIT);
121 if ((dh_client_pub = BN_new()) == NULL)
122 fatal("dh_client_pub == NULL");
123 packet_get_bignum2(dh_client_pub);
127 fprintf(stderr, "dh_client_pub= ");
128 BN_print_fp(stderr, dh_client_pub);
129 fprintf(stderr, "\n");
130 debug("bits %d", BN_num_bits(dh_client_pub));
134 DHparams_print_fp(stderr, dh);
135 fprintf(stderr, "pub= ");
136 BN_print_fp(stderr, dh->pub_key);
137 fprintf(stderr, "\n");
139 if (!dh_pub_is_valid(dh, dh_client_pub))
140 packet_disconnect("bad client public DH value");
143 kbuf = xmalloc(klen);
144 if ((kout = DH_compute_key(kbuf, dh_client_pub, dh)) < 0)
145 fatal("DH_compute_key: failed");
147 dump_digest("shared secret", kbuf, kout);
149 if ((shared_secret = BN_new()) == NULL)
150 fatal("kexgex_server: BN_new failed");
151 if (BN_bin2bn(kbuf, kout, shared_secret) == NULL)
152 fatal("kexgex_server: BN_bin2bn failed");
153 explicit_bzero(kbuf, klen);
156 key_to_blob(server_host_public, &server_host_key_blob, &sbloblen);
158 if (type == SSH2_MSG_KEX_DH_GEX_REQUEST_OLD)
159 omin = min = omax = max = -1;
164 kex->client_version_string,
165 kex->server_version_string,
166 buffer_ptr(&kex->peer), buffer_len(&kex->peer),
167 buffer_ptr(&kex->my), buffer_len(&kex->my),
168 server_host_key_blob, sbloblen,
176 BN_clear_free(dh_client_pub);
178 /* save session id := H */
179 if (kex->session_id == NULL) {
180 kex->session_id_len = hashlen;
181 kex->session_id = xmalloc(kex->session_id_len);
182 memcpy(kex->session_id, hash, kex->session_id_len);
186 kex->sign(server_host_private, server_host_public, &signature, &slen,
189 /* destroy_sensitive_data(); */
191 /* send server hostkey, DH pubkey 'f' and singed H */
192 debug("SSH2_MSG_KEX_DH_GEX_REPLY sent");
193 packet_start(SSH2_MSG_KEX_DH_GEX_REPLY);
194 packet_put_string(server_host_key_blob, sbloblen);
195 packet_put_bignum2(dh->pub_key); /* f */
196 packet_put_string(signature, slen);
200 free(server_host_key_blob);
201 /* have keys, free DH */
204 kex_derive_keys_bn(kex, hash, hashlen, shared_secret);
205 BN_clear_free(shared_secret);