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c20db291 | 1 | /* |
2 | * Copyright (c) 2000 Niels Provos. All rights reserved. | |
3 | * Copyright (c) 2001 Markus Friedl. All rights reserved. | |
4 | * | |
5 | * Redistribution and use in source and binary forms, with or without | |
6 | * modification, are permitted provided that the following conditions | |
7 | * are met: | |
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. | |
13 | * | |
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. | |
24 | */ | |
25 | ||
26 | #include "includes.h" | |
08822d99 | 27 | RCSID("$OpenBSD: kexgexc.c,v 1.3 2005/11/04 05:15:59 djm Exp $"); |
c20db291 | 28 | |
29 | #include "xmalloc.h" | |
30 | #include "key.h" | |
31 | #include "kex.h" | |
32 | #include "log.h" | |
33 | #include "packet.h" | |
34 | #include "dh.h" | |
35 | #include "ssh2.h" | |
36 | #include "compat.h" | |
37 | ||
38 | void | |
39 | kexgex_client(Kex *kex) | |
40 | { | |
41 | BIGNUM *dh_server_pub = NULL, *shared_secret = NULL; | |
42 | BIGNUM *p = NULL, *g = NULL; | |
43 | Key *server_host_key; | |
44 | u_char *kbuf, *hash, *signature = NULL, *server_host_key_blob = NULL; | |
08822d99 | 45 | u_int klen, kout, slen, sbloblen, hashlen; |
c20db291 | 46 | int min, max, nbits; |
47 | DH *dh; | |
48 | ||
49 | nbits = dh_estimate(kex->we_need * 8); | |
50 | ||
51 | if (datafellows & SSH_OLD_DHGEX) { | |
c20db291 | 52 | /* Old GEX request */ |
53 | packet_start(SSH2_MSG_KEX_DH_GEX_REQUEST_OLD); | |
54 | packet_put_int(nbits); | |
55 | min = DH_GRP_MIN; | |
56 | max = DH_GRP_MAX; | |
c20db291 | 57 | |
540d72c3 | 58 | debug("SSH2_MSG_KEX_DH_GEX_REQUEST_OLD(%u) sent", nbits); |
59 | } else { | |
c20db291 | 60 | /* New GEX request */ |
61 | min = DH_GRP_MIN; | |
62 | max = DH_GRP_MAX; | |
63 | packet_start(SSH2_MSG_KEX_DH_GEX_REQUEST); | |
64 | packet_put_int(min); | |
65 | packet_put_int(nbits); | |
66 | packet_put_int(max); | |
540d72c3 | 67 | |
68 | debug("SSH2_MSG_KEX_DH_GEX_REQUEST(%u<%u<%u) sent", | |
69 | min, nbits, max); | |
c20db291 | 70 | } |
71 | #ifdef DEBUG_KEXDH | |
72 | fprintf(stderr, "\nmin = %d, nbits = %d, max = %d\n", | |
73 | min, nbits, max); | |
74 | #endif | |
75 | packet_send(); | |
76 | ||
77 | debug("expecting SSH2_MSG_KEX_DH_GEX_GROUP"); | |
78 | packet_read_expect(SSH2_MSG_KEX_DH_GEX_GROUP); | |
79 | ||
80 | if ((p = BN_new()) == NULL) | |
81 | fatal("BN_new"); | |
82 | packet_get_bignum2(p); | |
83 | if ((g = BN_new()) == NULL) | |
84 | fatal("BN_new"); | |
85 | packet_get_bignum2(g); | |
86 | packet_check_eom(); | |
87 | ||
88 | if (BN_num_bits(p) < min || BN_num_bits(p) > max) | |
89 | fatal("DH_GEX group out of range: %d !< %d !< %d", | |
90 | min, BN_num_bits(p), max); | |
91 | ||
92 | dh = dh_new_group(g, p); | |
93 | dh_gen_key(dh, kex->we_need * 8); | |
94 | ||
95 | #ifdef DEBUG_KEXDH | |
96 | DHparams_print_fp(stderr, dh); | |
97 | fprintf(stderr, "pub= "); | |
98 | BN_print_fp(stderr, dh->pub_key); | |
99 | fprintf(stderr, "\n"); | |
100 | #endif | |
101 | ||
102 | debug("SSH2_MSG_KEX_DH_GEX_INIT sent"); | |
103 | /* generate and send 'e', client DH public key */ | |
104 | packet_start(SSH2_MSG_KEX_DH_GEX_INIT); | |
105 | packet_put_bignum2(dh->pub_key); | |
106 | packet_send(); | |
107 | ||
108 | debug("expecting SSH2_MSG_KEX_DH_GEX_REPLY"); | |
109 | packet_read_expect(SSH2_MSG_KEX_DH_GEX_REPLY); | |
110 | ||
111 | /* key, cert */ | |
112 | server_host_key_blob = packet_get_string(&sbloblen); | |
113 | server_host_key = key_from_blob(server_host_key_blob, sbloblen); | |
114 | if (server_host_key == NULL) | |
115 | fatal("cannot decode server_host_key_blob"); | |
116 | if (server_host_key->type != kex->hostkey_type) | |
117 | fatal("type mismatch for decoded server_host_key_blob"); | |
118 | if (kex->verify_host_key == NULL) | |
119 | fatal("cannot verify server_host_key"); | |
120 | if (kex->verify_host_key(server_host_key) == -1) | |
121 | fatal("server_host_key verification failed"); | |
122 | ||
123 | /* DH paramter f, server public DH key */ | |
124 | if ((dh_server_pub = BN_new()) == NULL) | |
125 | fatal("dh_server_pub == NULL"); | |
126 | packet_get_bignum2(dh_server_pub); | |
127 | ||
128 | #ifdef DEBUG_KEXDH | |
129 | fprintf(stderr, "dh_server_pub= "); | |
130 | BN_print_fp(stderr, dh_server_pub); | |
131 | fprintf(stderr, "\n"); | |
132 | debug("bits %d", BN_num_bits(dh_server_pub)); | |
133 | #endif | |
134 | ||
135 | /* signed H */ | |
136 | signature = packet_get_string(&slen); | |
137 | packet_check_eom(); | |
138 | ||
139 | if (!dh_pub_is_valid(dh, dh_server_pub)) | |
140 | packet_disconnect("bad server public DH value"); | |
141 | ||
142 | klen = DH_size(dh); | |
143 | kbuf = xmalloc(klen); | |
144 | kout = DH_compute_key(kbuf, dh_server_pub, dh); | |
145 | #ifdef DEBUG_KEXDH | |
146 | dump_digest("shared secret", kbuf, kout); | |
147 | #endif | |
148 | if ((shared_secret = BN_new()) == NULL) | |
149 | fatal("kexgex_client: BN_new failed"); | |
150 | BN_bin2bn(kbuf, kout, shared_secret); | |
151 | memset(kbuf, 0, klen); | |
152 | xfree(kbuf); | |
153 | ||
154 | if (datafellows & SSH_OLD_DHGEX) | |
155 | min = max = -1; | |
156 | ||
157 | /* calc and verify H */ | |
08822d99 | 158 | kexgex_hash( |
159 | kex->evp_md, | |
c20db291 | 160 | kex->client_version_string, |
161 | kex->server_version_string, | |
162 | buffer_ptr(&kex->my), buffer_len(&kex->my), | |
163 | buffer_ptr(&kex->peer), buffer_len(&kex->peer), | |
164 | server_host_key_blob, sbloblen, | |
165 | min, nbits, max, | |
166 | dh->p, dh->g, | |
167 | dh->pub_key, | |
168 | dh_server_pub, | |
08822d99 | 169 | shared_secret, |
170 | &hash, &hashlen | |
c20db291 | 171 | ); |
08822d99 | 172 | |
c20db291 | 173 | /* have keys, free DH */ |
174 | DH_free(dh); | |
175 | xfree(server_host_key_blob); | |
176 | BN_clear_free(dh_server_pub); | |
177 | ||
08822d99 | 178 | if (key_verify(server_host_key, signature, slen, hash, hashlen) != 1) |
c20db291 | 179 | fatal("key_verify failed for server_host_key"); |
180 | key_free(server_host_key); | |
181 | xfree(signature); | |
182 | ||
183 | /* save session id */ | |
184 | if (kex->session_id == NULL) { | |
08822d99 | 185 | kex->session_id_len = hashlen; |
c20db291 | 186 | kex->session_id = xmalloc(kex->session_id_len); |
187 | memcpy(kex->session_id, hash, kex->session_id_len); | |
188 | } | |
08822d99 | 189 | kex_derive_keys(kex, hash, hashlen, shared_secret); |
c20db291 | 190 | BN_clear_free(shared_secret); |
191 | ||
192 | kex_finish(kex); | |
193 | } |