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2e437378 | 1 | /* $OpenBSD: kexgexc.c,v 1.11 2006/11/06 21:25:28 markus Exp $ */ |
1c14df9e | 2 | /* |
3 | * Copyright (c) 2000 Niels Provos. All rights reserved. | |
4 | * Copyright (c) 2001 Markus Friedl. All rights reserved. | |
5 | * | |
6 | * Redistribution and use in source and binary forms, with or without | |
7 | * modification, are permitted provided that the following conditions | |
8 | * are met: | |
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. | |
14 | * | |
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. | |
25 | */ | |
26 | ||
27 | #include "includes.h" | |
2e437378 | 28 | |
29 | #include <sys/types.h> | |
30 | ||
31 | #include <stdarg.h> | |
32 | #include <stdio.h> | |
33 | #include <string.h> | |
34 | #include <signal.h> | |
1c14df9e | 35 | |
36 | #include "xmalloc.h" | |
2e437378 | 37 | #include "buffer.h" |
1c14df9e | 38 | #include "key.h" |
2e437378 | 39 | #include "cipher.h" |
1c14df9e | 40 | #include "kex.h" |
41 | #include "log.h" | |
42 | #include "packet.h" | |
43 | #include "dh.h" | |
44 | #include "ssh2.h" | |
45 | #include "compat.h" | |
46 | ||
47 | void | |
48 | kexgex_client(Kex *kex) | |
49 | { | |
50 | BIGNUM *dh_server_pub = NULL, *shared_secret = NULL; | |
51 | BIGNUM *p = NULL, *g = NULL; | |
52 | Key *server_host_key; | |
53 | u_char *kbuf, *hash, *signature = NULL, *server_host_key_blob = NULL; | |
2e437378 | 54 | u_int klen, slen, sbloblen, hashlen; |
55 | int kout; | |
1c14df9e | 56 | int min, max, nbits; |
57 | DH *dh; | |
58 | ||
59 | nbits = dh_estimate(kex->we_need * 8); | |
60 | ||
61 | if (datafellows & SSH_OLD_DHGEX) { | |
1c14df9e | 62 | /* Old GEX request */ |
63 | packet_start(SSH2_MSG_KEX_DH_GEX_REQUEST_OLD); | |
64 | packet_put_int(nbits); | |
65 | min = DH_GRP_MIN; | |
66 | max = DH_GRP_MAX; | |
1c14df9e | 67 | |
416fd2a8 | 68 | debug("SSH2_MSG_KEX_DH_GEX_REQUEST_OLD(%u) sent", nbits); |
69 | } else { | |
1c14df9e | 70 | /* New GEX request */ |
71 | min = DH_GRP_MIN; | |
72 | max = DH_GRP_MAX; | |
73 | packet_start(SSH2_MSG_KEX_DH_GEX_REQUEST); | |
74 | packet_put_int(min); | |
75 | packet_put_int(nbits); | |
76 | packet_put_int(max); | |
416fd2a8 | 77 | |
78 | debug("SSH2_MSG_KEX_DH_GEX_REQUEST(%u<%u<%u) sent", | |
79 | min, nbits, max); | |
1c14df9e | 80 | } |
81 | #ifdef DEBUG_KEXDH | |
82 | fprintf(stderr, "\nmin = %d, nbits = %d, max = %d\n", | |
83 | min, nbits, max); | |
84 | #endif | |
85 | packet_send(); | |
86 | ||
87 | debug("expecting SSH2_MSG_KEX_DH_GEX_GROUP"); | |
88 | packet_read_expect(SSH2_MSG_KEX_DH_GEX_GROUP); | |
89 | ||
90 | if ((p = BN_new()) == NULL) | |
91 | fatal("BN_new"); | |
92 | packet_get_bignum2(p); | |
93 | if ((g = BN_new()) == NULL) | |
94 | fatal("BN_new"); | |
95 | packet_get_bignum2(g); | |
96 | packet_check_eom(); | |
97 | ||
98 | if (BN_num_bits(p) < min || BN_num_bits(p) > max) | |
99 | fatal("DH_GEX group out of range: %d !< %d !< %d", | |
100 | min, BN_num_bits(p), max); | |
101 | ||
102 | dh = dh_new_group(g, p); | |
103 | dh_gen_key(dh, kex->we_need * 8); | |
104 | ||
105 | #ifdef DEBUG_KEXDH | |
106 | DHparams_print_fp(stderr, dh); | |
107 | fprintf(stderr, "pub= "); | |
108 | BN_print_fp(stderr, dh->pub_key); | |
109 | fprintf(stderr, "\n"); | |
110 | #endif | |
111 | ||
112 | debug("SSH2_MSG_KEX_DH_GEX_INIT sent"); | |
113 | /* generate and send 'e', client DH public key */ | |
114 | packet_start(SSH2_MSG_KEX_DH_GEX_INIT); | |
115 | packet_put_bignum2(dh->pub_key); | |
116 | packet_send(); | |
117 | ||
118 | debug("expecting SSH2_MSG_KEX_DH_GEX_REPLY"); | |
119 | packet_read_expect(SSH2_MSG_KEX_DH_GEX_REPLY); | |
120 | ||
121 | /* key, cert */ | |
122 | server_host_key_blob = packet_get_string(&sbloblen); | |
123 | server_host_key = key_from_blob(server_host_key_blob, sbloblen); | |
124 | if (server_host_key == NULL) | |
125 | fatal("cannot decode server_host_key_blob"); | |
126 | if (server_host_key->type != kex->hostkey_type) | |
127 | fatal("type mismatch for decoded server_host_key_blob"); | |
128 | if (kex->verify_host_key == NULL) | |
129 | fatal("cannot verify server_host_key"); | |
130 | if (kex->verify_host_key(server_host_key) == -1) | |
131 | fatal("server_host_key verification failed"); | |
132 | ||
2e437378 | 133 | /* DH parameter f, server public DH key */ |
1c14df9e | 134 | if ((dh_server_pub = BN_new()) == NULL) |
135 | fatal("dh_server_pub == NULL"); | |
136 | packet_get_bignum2(dh_server_pub); | |
137 | ||
138 | #ifdef DEBUG_KEXDH | |
139 | fprintf(stderr, "dh_server_pub= "); | |
140 | BN_print_fp(stderr, dh_server_pub); | |
141 | fprintf(stderr, "\n"); | |
142 | debug("bits %d", BN_num_bits(dh_server_pub)); | |
143 | #endif | |
144 | ||
145 | /* signed H */ | |
146 | signature = packet_get_string(&slen); | |
147 | packet_check_eom(); | |
148 | ||
149 | if (!dh_pub_is_valid(dh, dh_server_pub)) | |
150 | packet_disconnect("bad server public DH value"); | |
151 | ||
152 | klen = DH_size(dh); | |
153 | kbuf = xmalloc(klen); | |
2e437378 | 154 | if ((kout = DH_compute_key(kbuf, dh_server_pub, dh)) < 0) |
155 | fatal("DH_compute_key: failed"); | |
1c14df9e | 156 | #ifdef DEBUG_KEXDH |
157 | dump_digest("shared secret", kbuf, kout); | |
158 | #endif | |
159 | if ((shared_secret = BN_new()) == NULL) | |
160 | fatal("kexgex_client: BN_new failed"); | |
2e437378 | 161 | if (BN_bin2bn(kbuf, kout, shared_secret) == NULL) |
162 | fatal("kexgex_client: BN_bin2bn failed"); | |
1c14df9e | 163 | memset(kbuf, 0, klen); |
164 | xfree(kbuf); | |
165 | ||
166 | if (datafellows & SSH_OLD_DHGEX) | |
167 | min = max = -1; | |
168 | ||
169 | /* calc and verify H */ | |
e00da40d | 170 | kexgex_hash( |
171 | kex->evp_md, | |
1c14df9e | 172 | kex->client_version_string, |
173 | kex->server_version_string, | |
174 | buffer_ptr(&kex->my), buffer_len(&kex->my), | |
175 | buffer_ptr(&kex->peer), buffer_len(&kex->peer), | |
176 | server_host_key_blob, sbloblen, | |
177 | min, nbits, max, | |
178 | dh->p, dh->g, | |
179 | dh->pub_key, | |
180 | dh_server_pub, | |
e00da40d | 181 | shared_secret, |
182 | &hash, &hashlen | |
1c14df9e | 183 | ); |
e00da40d | 184 | |
1c14df9e | 185 | /* have keys, free DH */ |
186 | DH_free(dh); | |
187 | xfree(server_host_key_blob); | |
188 | BN_clear_free(dh_server_pub); | |
189 | ||
e00da40d | 190 | if (key_verify(server_host_key, signature, slen, hash, hashlen) != 1) |
1c14df9e | 191 | fatal("key_verify failed for server_host_key"); |
192 | key_free(server_host_key); | |
193 | xfree(signature); | |
194 | ||
195 | /* save session id */ | |
196 | if (kex->session_id == NULL) { | |
e00da40d | 197 | kex->session_id_len = hashlen; |
1c14df9e | 198 | kex->session_id = xmalloc(kex->session_id_len); |
199 | memcpy(kex->session_id, hash, kex->session_id_len); | |
200 | } | |
e00da40d | 201 | kex_derive_keys(kex, hash, hashlen, shared_secret); |
1c14df9e | 202 | BN_clear_free(shared_secret); |
203 | ||
204 | kex_finish(kex); | |
205 | } |