1 /* $OpenBSD: kexdhc.c,v 1.9 2006/08/03 03:34:42 deraadt Exp $ */
3 * Copyright (c) 2001 Markus Friedl. All rights reserved.
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
15 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
16 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
17 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
18 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
19 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
20 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
21 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
23 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
28 #include <sys/types.h>
46 kexdh_client(Kex *kex)
48 BIGNUM *dh_server_pub = NULL, *shared_secret = NULL;
51 u_char *server_host_key_blob = NULL, *signature = NULL;
53 u_int klen, kout, slen, sbloblen, hashlen;
55 /* generate and send 'e', client DH public key */
56 switch (kex->kex_type) {
57 case KEX_DH_GRP1_SHA1:
60 case KEX_DH_GRP14_SHA1:
61 dh = dh_new_group14();
64 fatal("%s: Unexpected KEX type %d", __func__, kex->kex_type);
66 dh_gen_key(dh, kex->we_need * 8);
67 packet_start(SSH2_MSG_KEXDH_INIT);
68 packet_put_bignum2(dh->pub_key);
71 debug("sending SSH2_MSG_KEXDH_INIT");
73 DHparams_print_fp(stderr, dh);
74 fprintf(stderr, "pub= ");
75 BN_print_fp(stderr, dh->pub_key);
76 fprintf(stderr, "\n");
79 debug("expecting SSH2_MSG_KEXDH_REPLY");
80 packet_read_expect(SSH2_MSG_KEXDH_REPLY);
83 server_host_key_blob = packet_get_string(&sbloblen);
84 server_host_key = key_from_blob(server_host_key_blob, sbloblen);
85 if (server_host_key == NULL)
86 fatal("cannot decode server_host_key_blob");
87 if (server_host_key->type != kex->hostkey_type)
88 fatal("type mismatch for decoded server_host_key_blob");
89 if (kex->verify_host_key == NULL)
90 fatal("cannot verify server_host_key");
91 if (kex->verify_host_key(server_host_key) == -1)
92 fatal("server_host_key verification failed");
94 /* DH parameter f, server public DH key */
95 if ((dh_server_pub = BN_new()) == NULL)
96 fatal("dh_server_pub == NULL");
97 packet_get_bignum2(dh_server_pub);
100 fprintf(stderr, "dh_server_pub= ");
101 BN_print_fp(stderr, dh_server_pub);
102 fprintf(stderr, "\n");
103 debug("bits %d", BN_num_bits(dh_server_pub));
107 signature = packet_get_string(&slen);
110 if (!dh_pub_is_valid(dh, dh_server_pub))
111 packet_disconnect("bad server public DH value");
114 kbuf = xmalloc(klen);
115 kout = DH_compute_key(kbuf, dh_server_pub, dh);
117 dump_digest("shared secret", kbuf, kout);
119 if ((shared_secret = BN_new()) == NULL)
120 fatal("kexdh_client: BN_new failed");
121 BN_bin2bn(kbuf, kout, shared_secret);
122 memset(kbuf, 0, klen);
125 /* calc and verify H */
127 kex->client_version_string,
128 kex->server_version_string,
129 buffer_ptr(&kex->my), buffer_len(&kex->my),
130 buffer_ptr(&kex->peer), buffer_len(&kex->peer),
131 server_host_key_blob, sbloblen,
137 xfree(server_host_key_blob);
138 BN_clear_free(dh_server_pub);
141 if (key_verify(server_host_key, signature, slen, hash, hashlen) != 1)
142 fatal("key_verify failed for server_host_key");
143 key_free(server_host_key);
146 /* save session id */
147 if (kex->session_id == NULL) {
148 kex->session_id_len = hashlen;
149 kex->session_id = xmalloc(kex->session_id_len);
150 memcpy(kex->session_id, hash, kex->session_id_len);
153 kex_derive_keys(kex, hash, hashlen, shared_secret);
154 BN_clear_free(shared_secret);