]>
Commit | Line | Data |
---|---|---|
2e437378 | 1 | /* $OpenBSD: kexgexs.c,v 1.10 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/param.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" | |
2e437378 | 46 | #ifdef GSSAPI |
47 | #include "ssh-gss.h" | |
48 | #endif | |
1c14df9e | 49 | #include "monitor_wrap.h" |
50 | ||
51 | void | |
52 | kexgex_server(Kex *kex) | |
53 | { | |
54 | BIGNUM *shared_secret = NULL, *dh_client_pub = NULL; | |
55 | Key *server_host_key; | |
56 | DH *dh; | |
57 | u_char *kbuf, *hash, *signature = NULL, *server_host_key_blob = NULL; | |
2e437378 | 58 | u_int sbloblen, klen, slen, hashlen; |
59 | int min = -1, max = -1, nbits = -1, type, kout; | |
1c14df9e | 60 | |
61 | if (kex->load_host_key == NULL) | |
62 | fatal("Cannot load hostkey"); | |
63 | server_host_key = kex->load_host_key(kex->hostkey_type); | |
64 | if (server_host_key == NULL) | |
65 | fatal("Unsupported hostkey type %d", kex->hostkey_type); | |
66 | ||
67 | type = packet_read(); | |
68 | switch (type) { | |
69 | case SSH2_MSG_KEX_DH_GEX_REQUEST: | |
70 | debug("SSH2_MSG_KEX_DH_GEX_REQUEST received"); | |
71 | min = packet_get_int(); | |
72 | nbits = packet_get_int(); | |
73 | max = packet_get_int(); | |
74 | min = MAX(DH_GRP_MIN, min); | |
75 | max = MIN(DH_GRP_MAX, max); | |
76 | break; | |
77 | case SSH2_MSG_KEX_DH_GEX_REQUEST_OLD: | |
78 | debug("SSH2_MSG_KEX_DH_GEX_REQUEST_OLD received"); | |
79 | nbits = packet_get_int(); | |
80 | min = DH_GRP_MIN; | |
81 | max = DH_GRP_MAX; | |
82 | /* unused for old GEX */ | |
83 | break; | |
84 | default: | |
85 | fatal("protocol error during kex, no DH_GEX_REQUEST: %d", type); | |
86 | } | |
87 | packet_check_eom(); | |
88 | ||
89 | if (max < min || nbits < min || max < nbits) | |
90 | fatal("DH_GEX_REQUEST, bad parameters: %d !< %d !< %d", | |
91 | min, nbits, max); | |
92 | ||
93 | /* Contact privileged parent */ | |
94 | dh = PRIVSEP(choose_dh(min, nbits, max)); | |
95 | if (dh == NULL) | |
96 | packet_disconnect("Protocol error: no matching DH grp found"); | |
97 | ||
98 | debug("SSH2_MSG_KEX_DH_GEX_GROUP sent"); | |
99 | packet_start(SSH2_MSG_KEX_DH_GEX_GROUP); | |
100 | packet_put_bignum2(dh->p); | |
101 | packet_put_bignum2(dh->g); | |
102 | packet_send(); | |
103 | ||
104 | /* flush */ | |
105 | packet_write_wait(); | |
106 | ||
107 | /* Compute our exchange value in parallel with the client */ | |
108 | dh_gen_key(dh, kex->we_need * 8); | |
109 | ||
110 | debug("expecting SSH2_MSG_KEX_DH_GEX_INIT"); | |
111 | packet_read_expect(SSH2_MSG_KEX_DH_GEX_INIT); | |
112 | ||
113 | /* key, cert */ | |
114 | if ((dh_client_pub = BN_new()) == NULL) | |
115 | fatal("dh_client_pub == NULL"); | |
116 | packet_get_bignum2(dh_client_pub); | |
117 | packet_check_eom(); | |
118 | ||
119 | #ifdef DEBUG_KEXDH | |
120 | fprintf(stderr, "dh_client_pub= "); | |
121 | BN_print_fp(stderr, dh_client_pub); | |
122 | fprintf(stderr, "\n"); | |
123 | debug("bits %d", BN_num_bits(dh_client_pub)); | |
124 | #endif | |
125 | ||
126 | #ifdef DEBUG_KEXDH | |
127 | DHparams_print_fp(stderr, dh); | |
128 | fprintf(stderr, "pub= "); | |
129 | BN_print_fp(stderr, dh->pub_key); | |
130 | fprintf(stderr, "\n"); | |
131 | #endif | |
132 | if (!dh_pub_is_valid(dh, dh_client_pub)) | |
133 | packet_disconnect("bad client public DH value"); | |
134 | ||
135 | klen = DH_size(dh); | |
136 | kbuf = xmalloc(klen); | |
2e437378 | 137 | if ((kout = DH_compute_key(kbuf, dh_client_pub, dh)) < 0) |
138 | fatal("DH_compute_key: failed"); | |
1c14df9e | 139 | #ifdef DEBUG_KEXDH |
140 | dump_digest("shared secret", kbuf, kout); | |
141 | #endif | |
142 | if ((shared_secret = BN_new()) == NULL) | |
143 | fatal("kexgex_server: BN_new failed"); | |
2e437378 | 144 | if (BN_bin2bn(kbuf, kout, shared_secret) == NULL) |
145 | fatal("kexgex_server: BN_bin2bn failed"); | |
1c14df9e | 146 | memset(kbuf, 0, klen); |
147 | xfree(kbuf); | |
148 | ||
149 | key_to_blob(server_host_key, &server_host_key_blob, &sbloblen); | |
150 | ||
151 | if (type == SSH2_MSG_KEX_DH_GEX_REQUEST_OLD) | |
152 | min = max = -1; | |
153 | ||
e00da40d | 154 | /* calc H */ |
155 | kexgex_hash( | |
156 | kex->evp_md, | |
1c14df9e | 157 | kex->client_version_string, |
158 | kex->server_version_string, | |
159 | buffer_ptr(&kex->peer), buffer_len(&kex->peer), | |
160 | buffer_ptr(&kex->my), buffer_len(&kex->my), | |
161 | server_host_key_blob, sbloblen, | |
162 | min, nbits, max, | |
163 | dh->p, dh->g, | |
164 | dh_client_pub, | |
165 | dh->pub_key, | |
e00da40d | 166 | shared_secret, |
167 | &hash, &hashlen | |
1c14df9e | 168 | ); |
169 | BN_clear_free(dh_client_pub); | |
170 | ||
171 | /* save session id := H */ | |
1c14df9e | 172 | if (kex->session_id == NULL) { |
e00da40d | 173 | kex->session_id_len = hashlen; |
1c14df9e | 174 | kex->session_id = xmalloc(kex->session_id_len); |
175 | memcpy(kex->session_id, hash, kex->session_id_len); | |
176 | } | |
177 | ||
178 | /* sign H */ | |
e00da40d | 179 | PRIVSEP(key_sign(server_host_key, &signature, &slen, hash, hashlen)); |
1c14df9e | 180 | |
181 | /* destroy_sensitive_data(); */ | |
182 | ||
183 | /* send server hostkey, DH pubkey 'f' and singed H */ | |
184 | debug("SSH2_MSG_KEX_DH_GEX_REPLY sent"); | |
185 | packet_start(SSH2_MSG_KEX_DH_GEX_REPLY); | |
186 | packet_put_string(server_host_key_blob, sbloblen); | |
187 | packet_put_bignum2(dh->pub_key); /* f */ | |
188 | packet_put_string(signature, slen); | |
189 | packet_send(); | |
190 | ||
191 | xfree(signature); | |
192 | xfree(server_host_key_blob); | |
193 | /* have keys, free DH */ | |
194 | DH_free(dh); | |
195 | ||
e00da40d | 196 | kex_derive_keys(kex, hash, hashlen, shared_secret); |
1c14df9e | 197 | BN_clear_free(shared_secret); |
198 | ||
199 | kex_finish(kex); | |
200 | } |