1 /* $OpenBSD: kexgexc.c,v 1.17 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/types.h>
31 #include <openssl/dh.h>
50 kexgex_client(Kex
*kex
)
52 BIGNUM
*dh_server_pub
= NULL
, *shared_secret
= NULL
;
53 BIGNUM
*p
= NULL
, *g
= NULL
;
55 u_char
*kbuf
, *hash
, *signature
= NULL
, *server_host_key_blob
= NULL
;
56 u_int klen
, slen
, sbloblen
, hashlen
;
61 nbits
= dh_estimate(kex
->dh_need
* 8);
63 if (datafellows
& SSH_OLD_DHGEX
) {
65 packet_start(SSH2_MSG_KEX_DH_GEX_REQUEST_OLD
);
66 packet_put_int(nbits
);
70 debug("SSH2_MSG_KEX_DH_GEX_REQUEST_OLD(%u) sent", nbits
);
75 packet_start(SSH2_MSG_KEX_DH_GEX_REQUEST
);
77 packet_put_int(nbits
);
80 debug("SSH2_MSG_KEX_DH_GEX_REQUEST(%u<%u<%u) sent",
84 fprintf(stderr
, "\nmin = %d, nbits = %d, max = %d\n",
89 debug("expecting SSH2_MSG_KEX_DH_GEX_GROUP");
90 packet_read_expect(SSH2_MSG_KEX_DH_GEX_GROUP
);
92 if ((p
= BN_new()) == NULL
)
94 packet_get_bignum2(p
);
95 if ((g
= BN_new()) == NULL
)
97 packet_get_bignum2(g
);
100 if (BN_num_bits(p
) < min
|| BN_num_bits(p
) > max
)
101 fatal("DH_GEX group out of range: %d !< %d !< %d",
102 min
, BN_num_bits(p
), max
);
104 dh
= dh_new_group(g
, p
);
105 dh_gen_key(dh
, kex
->we_need
* 8);
108 DHparams_print_fp(stderr
, dh
);
109 fprintf(stderr
, "pub= ");
110 BN_print_fp(stderr
, dh
->pub_key
);
111 fprintf(stderr
, "\n");
114 debug("SSH2_MSG_KEX_DH_GEX_INIT sent");
115 /* generate and send 'e', client DH public key */
116 packet_start(SSH2_MSG_KEX_DH_GEX_INIT
);
117 packet_put_bignum2(dh
->pub_key
);
120 debug("expecting SSH2_MSG_KEX_DH_GEX_REPLY");
121 packet_read_expect(SSH2_MSG_KEX_DH_GEX_REPLY
);
124 server_host_key_blob
= packet_get_string(&sbloblen
);
125 server_host_key
= key_from_blob(server_host_key_blob
, sbloblen
);
126 if (server_host_key
== NULL
)
127 fatal("cannot decode server_host_key_blob");
128 if (server_host_key
->type
!= kex
->hostkey_type
)
129 fatal("type mismatch for decoded server_host_key_blob");
130 if (kex
->verify_host_key
== NULL
)
131 fatal("cannot verify server_host_key");
132 if (kex
->verify_host_key(server_host_key
) == -1)
133 fatal("server_host_key verification failed");
135 /* DH parameter f, server public DH key */
136 if ((dh_server_pub
= BN_new()) == NULL
)
137 fatal("dh_server_pub == NULL");
138 packet_get_bignum2(dh_server_pub
);
141 fprintf(stderr
, "dh_server_pub= ");
142 BN_print_fp(stderr
, dh_server_pub
);
143 fprintf(stderr
, "\n");
144 debug("bits %d", BN_num_bits(dh_server_pub
));
148 signature
= packet_get_string(&slen
);
151 if (!dh_pub_is_valid(dh
, dh_server_pub
))
152 packet_disconnect("bad server public DH value");
155 kbuf
= xmalloc(klen
);
156 if ((kout
= DH_compute_key(kbuf
, dh_server_pub
, dh
)) < 0)
157 fatal("DH_compute_key: failed");
159 dump_digest("shared secret", kbuf
, kout
);
161 if ((shared_secret
= BN_new()) == NULL
)
162 fatal("kexgex_client: BN_new failed");
163 if (BN_bin2bn(kbuf
, kout
, shared_secret
) == NULL
)
164 fatal("kexgex_client: BN_bin2bn failed");
165 explicit_bzero(kbuf
, klen
);
168 if (datafellows
& SSH_OLD_DHGEX
)
171 /* calc and verify H */
174 kex
->client_version_string
,
175 kex
->server_version_string
,
176 buffer_ptr(&kex
->my
), buffer_len(&kex
->my
),
177 buffer_ptr(&kex
->peer
), buffer_len(&kex
->peer
),
178 server_host_key_blob
, sbloblen
,
187 /* have keys, free DH */
189 free(server_host_key_blob
);
190 BN_clear_free(dh_server_pub
);
192 if (key_verify(server_host_key
, signature
, slen
, hash
, hashlen
) != 1)
193 fatal("key_verify failed for server_host_key");
194 key_free(server_host_key
);
197 /* save session id */
198 if (kex
->session_id
== NULL
) {
199 kex
->session_id_len
= hashlen
;
200 kex
->session_id
= xmalloc(kex
->session_id_len
);
201 memcpy(kex
->session_id
, hash
, kex
->session_id_len
);
203 kex_derive_keys_bn(kex
, hash
, hashlen
, shared_secret
);
204 BN_clear_free(shared_secret
);