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[dragonfly.git] / crypto / openssh / kexgexs.c
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40c002af 1/* $OpenBSD: kexgexs.c,v 1.12 2009/06/21 07:37:15 dtucker Exp $ */
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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"
28
29#include <sys/param.h>
30
31#include <stdarg.h>
32#include <stdio.h>
33#include <string.h>
34#include <signal.h>
35
36#include "xmalloc.h"
37#include "buffer.h"
38#include "key.h"
39#include "cipher.h"
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#ifdef GSSAPI
47#include "ssh-gss.h"
48#endif
49#include "monitor_wrap.h"
50
51void
52kexgex_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;
58 u_int sbloblen, klen, slen, hashlen;
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59 int omin = -1, min = -1, omax = -1, max = -1, onbits = -1, nbits = -1;
60 int type, kout;
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61
62 if (kex->load_host_key == NULL)
63 fatal("Cannot load hostkey");
64 server_host_key = kex->load_host_key(kex->hostkey_type);
65 if (server_host_key == NULL)
66 fatal("Unsupported hostkey type %d", kex->hostkey_type);
67
68 type = packet_read();
69 switch (type) {
70 case SSH2_MSG_KEX_DH_GEX_REQUEST:
71 debug("SSH2_MSG_KEX_DH_GEX_REQUEST received");
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72 omin = min = packet_get_int();
73 onbits = nbits = packet_get_int();
74 omax = max = packet_get_int();
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75 min = MAX(DH_GRP_MIN, min);
76 max = MIN(DH_GRP_MAX, max);
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77 nbits = MAX(DH_GRP_MIN, nbits);
78 nbits = MIN(DH_GRP_MAX, nbits);
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79 break;
80 case SSH2_MSG_KEX_DH_GEX_REQUEST_OLD:
81 debug("SSH2_MSG_KEX_DH_GEX_REQUEST_OLD received");
cb5eb4f1 82 onbits = nbits = packet_get_int();
16c343f1 83 /* unused for old GEX */
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84 omin = min = DH_GRP_MIN;
85 omax = max = DH_GRP_MAX;
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86 break;
87 default:
88 fatal("protocol error during kex, no DH_GEX_REQUEST: %d", type);
89 }
90 packet_check_eom();
91
cb5eb4f1 92 if (omax < omin || onbits < omin || omax < onbits)
16c343f1 93 fatal("DH_GEX_REQUEST, bad parameters: %d !< %d !< %d",
cb5eb4f1 94 omin, onbits, omax);
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95
96 /* Contact privileged parent */
97 dh = PRIVSEP(choose_dh(min, nbits, max));
98 if (dh == NULL)
99 packet_disconnect("Protocol error: no matching DH grp found");
100
101 debug("SSH2_MSG_KEX_DH_GEX_GROUP sent");
102 packet_start(SSH2_MSG_KEX_DH_GEX_GROUP);
103 packet_put_bignum2(dh->p);
104 packet_put_bignum2(dh->g);
105 packet_send();
106
107 /* flush */
108 packet_write_wait();
109
110 /* Compute our exchange value in parallel with the client */
111 dh_gen_key(dh, kex->we_need * 8);
112
113 debug("expecting SSH2_MSG_KEX_DH_GEX_INIT");
114 packet_read_expect(SSH2_MSG_KEX_DH_GEX_INIT);
115
116 /* key, cert */
117 if ((dh_client_pub = BN_new()) == NULL)
118 fatal("dh_client_pub == NULL");
119 packet_get_bignum2(dh_client_pub);
120 packet_check_eom();
121
122#ifdef DEBUG_KEXDH
123 fprintf(stderr, "dh_client_pub= ");
124 BN_print_fp(stderr, dh_client_pub);
125 fprintf(stderr, "\n");
126 debug("bits %d", BN_num_bits(dh_client_pub));
127#endif
128
129#ifdef DEBUG_KEXDH
130 DHparams_print_fp(stderr, dh);
131 fprintf(stderr, "pub= ");
132 BN_print_fp(stderr, dh->pub_key);
133 fprintf(stderr, "\n");
134#endif
135 if (!dh_pub_is_valid(dh, dh_client_pub))
136 packet_disconnect("bad client public DH value");
137
138 klen = DH_size(dh);
139 kbuf = xmalloc(klen);
140 if ((kout = DH_compute_key(kbuf, dh_client_pub, dh)) < 0)
141 fatal("DH_compute_key: failed");
142#ifdef DEBUG_KEXDH
143 dump_digest("shared secret", kbuf, kout);
144#endif
145 if ((shared_secret = BN_new()) == NULL)
146 fatal("kexgex_server: BN_new failed");
147 if (BN_bin2bn(kbuf, kout, shared_secret) == NULL)
148 fatal("kexgex_server: BN_bin2bn failed");
149 memset(kbuf, 0, klen);
150 xfree(kbuf);
151
152 key_to_blob(server_host_key, &server_host_key_blob, &sbloblen);
153
154 if (type == SSH2_MSG_KEX_DH_GEX_REQUEST_OLD)
cb5eb4f1 155 omin = min = omax = max = -1;
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156
157 /* calc H */
158 kexgex_hash(
159 kex->evp_md,
160 kex->client_version_string,
161 kex->server_version_string,
162 buffer_ptr(&kex->peer), buffer_len(&kex->peer),
163 buffer_ptr(&kex->my), buffer_len(&kex->my),
164 server_host_key_blob, sbloblen,
cb5eb4f1 165 omin, onbits, omax,
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166 dh->p, dh->g,
167 dh_client_pub,
168 dh->pub_key,
169 shared_secret,
170 &hash, &hashlen
171 );
172 BN_clear_free(dh_client_pub);
173
174 /* save session id := H */
175 if (kex->session_id == NULL) {
176 kex->session_id_len = hashlen;
177 kex->session_id = xmalloc(kex->session_id_len);
178 memcpy(kex->session_id, hash, kex->session_id_len);
179 }
180
181 /* sign H */
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182 if (PRIVSEP(key_sign(server_host_key, &signature, &slen, hash,
183 hashlen)) < 0)
184 fatal("kexgex_server: key_sign failed");
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185
186 /* destroy_sensitive_data(); */
187
188 /* send server hostkey, DH pubkey 'f' and singed H */
189 debug("SSH2_MSG_KEX_DH_GEX_REPLY sent");
190 packet_start(SSH2_MSG_KEX_DH_GEX_REPLY);
191 packet_put_string(server_host_key_blob, sbloblen);
192 packet_put_bignum2(dh->pub_key); /* f */
193 packet_put_string(signature, slen);
194 packet_send();
195
196 xfree(signature);
197 xfree(server_host_key_blob);
198 /* have keys, free DH */
199 DH_free(dh);
200
201 kex_derive_keys(kex, hash, hashlen, shared_secret);
202 BN_clear_free(shared_secret);
203
204 kex_finish(kex);
205}