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diff --git a/kexgssc.c b/kexgssc.c
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1/*
2 * Copyright (c) 2001-2006 Simon Wilkinson. All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 * 1. Redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 * notice, this list of conditions and the following disclaimer in the
11 * documentation and/or other materials provided with the distribution.
12 *
13 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR `AS IS'' AND ANY EXPRESS OR
14 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
15 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
16 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
17 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
18 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
19 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
20 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
21 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
22 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
23 */
24
25#include "includes.h"
26
27#ifdef GSSAPI
28
29#include "includes.h"
30
31#include <openssl/crypto.h>
32#include <openssl/bn.h>
33
34#include <string.h>
35
36#include "xmalloc.h"
37#include "buffer.h"
38#include "ssh2.h"
39#include "key.h"
40#include "cipher.h"
41#include "kex.h"
42#include "log.h"
43#include "packet.h"
44#include "dh.h"
45
46#include "ssh-gss.h"
47
48void
49kexgss_client(Kex *kex) {
50 gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER;
51 gss_buffer_desc recv_tok, gssbuf, msg_tok, *token_ptr;
52 Gssctxt *ctxt;
53 OM_uint32 maj_status, min_status, ret_flags;
54 u_int klen, kout, slen = 0, hashlen, strlen;
55 DH *dh;
56 BIGNUM *dh_server_pub = NULL;
57 BIGNUM *shared_secret = NULL;
58 BIGNUM *p = NULL;
59 BIGNUM *g = NULL;
60 u_char *kbuf, *hash;
61 u_char *serverhostkey = NULL;
62 char *msg;
63 char *lang;
64 int type = 0;
65 int first = 1;
66 int nbits = 0, min = DH_GRP_MIN, max = DH_GRP_MAX;
67
68 /* Initialise our GSSAPI world */
69 ssh_gssapi_build_ctx(&ctxt);
70 if (ssh_gssapi_id_kex(ctxt, kex->name, kex->kex_type)
71 == GSS_C_NO_OID)
72 fatal("Couldn't identify host exchange");
73
74 if (ssh_gssapi_import_name(ctxt, kex->gss_host))
75 fatal("Couldn't import hostname");
76
77 switch (kex->kex_type) {
78 case KEX_GSS_GRP1_SHA1:
79 dh = dh_new_group1();
80 break;
81 case KEX_GSS_GRP14_SHA1:
82 dh = dh_new_group14();
83 break;
84 case KEX_GSS_GEX_SHA1:
85 debug("Doing group exchange\n");
86 nbits = dh_estimate(kex->we_need * 8);
87 packet_start(SSH2_MSG_KEXGSS_GROUPREQ);
88 packet_put_int(min);
89 packet_put_int(nbits);
90 packet_put_int(max);
91
92 packet_send();
93
94 packet_read_expect(SSH2_MSG_KEXGSS_GROUP);
95
96 if ((p = BN_new()) == NULL)
97 fatal("BN_new() failed");
98 packet_get_bignum2(p);
99 if ((g = BN_new()) == NULL)
100 fatal("BN_new() failed");
101 packet_get_bignum2(g);
102 packet_check_eom();
103
104 if (BN_num_bits(p) < min || BN_num_bits(p) > max)
105 fatal("GSSGRP_GEX group out of range: %d !< %d !< %d",
106 min, BN_num_bits(p), max);
107
108 dh = dh_new_group(g, p);
109 break;
110 default:
111 fatal("%s: Unexpected KEX type %d", __func__, kex->kex_type);
112 }
113
114 /* Step 1 - e is dh->pub_key */
115 dh_gen_key(dh, kex->we_need * 8);
116
117 /* This is f, we initialise it now to make life easier */
118 dh_server_pub = BN_new();
119 if (dh_server_pub == NULL)
120 fatal("dh_server_pub == NULL");
121
122 token_ptr = GSS_C_NO_BUFFER;
123
124 do {
125 debug("Calling gss_init_sec_context");
126
127 maj_status = ssh_gssapi_init_ctx(ctxt,
128 kex->gss_deleg_creds, token_ptr, &send_tok,
129 &ret_flags);
130
131 if (GSS_ERROR(maj_status)) {
132 if (send_tok.length != 0) {
133 packet_start(SSH2_MSG_KEXGSS_CONTINUE);
134 packet_put_string(send_tok.value,
135 send_tok.length);
136 }
137 fatal("gss_init_context failed");
138 }
139
140 /* If we've got an old receive buffer get rid of it */
141 if (token_ptr != GSS_C_NO_BUFFER)
142 xfree(recv_tok.value);
143
144 if (maj_status == GSS_S_COMPLETE) {
145 /* If mutual state flag is not true, kex fails */
146 if (!(ret_flags & GSS_C_MUTUAL_FLAG))
147 fatal("Mutual authentication failed");
148
149 /* If integ avail flag is not true kex fails */
150 if (!(ret_flags & GSS_C_INTEG_FLAG))
151 fatal("Integrity check failed");
152 }
153
154 /*
155 * If we have data to send, then the last message that we
156 * received cannot have been a 'complete'.
157 */
158 if (send_tok.length != 0) {
159 if (first) {
160 packet_start(SSH2_MSG_KEXGSS_INIT);
161 packet_put_string(send_tok.value,
162 send_tok.length);
163 packet_put_bignum2(dh->pub_key);
164 first = 0;
165 } else {
166 packet_start(SSH2_MSG_KEXGSS_CONTINUE);
167 packet_put_string(send_tok.value,
168 send_tok.length);
169 }
170 packet_send();
171 gss_release_buffer(&min_status, &send_tok);
172
173 /* If we've sent them data, they should reply */
174 do {
175 type = packet_read();
176 if (type == SSH2_MSG_KEXGSS_HOSTKEY) {
177 debug("Received KEXGSS_HOSTKEY");
178 if (serverhostkey)
179 fatal("Server host key received more than once");
180 serverhostkey =
181 packet_get_string(&slen);
182 }
183 } while (type == SSH2_MSG_KEXGSS_HOSTKEY);
184
185 switch (type) {
186 case SSH2_MSG_KEXGSS_CONTINUE:
187 debug("Received GSSAPI_CONTINUE");
188 if (maj_status == GSS_S_COMPLETE)
189 fatal("GSSAPI Continue received from server when complete");
190 recv_tok.value = packet_get_string(&strlen);
191 recv_tok.length = strlen;
192 break;
193 case SSH2_MSG_KEXGSS_COMPLETE:
194 debug("Received GSSAPI_COMPLETE");
195 packet_get_bignum2(dh_server_pub);
196 msg_tok.value = packet_get_string(&strlen);
197 msg_tok.length = strlen;
198
199 /* Is there a token included? */
200 if (packet_get_char()) {
201 recv_tok.value=
202 packet_get_string(&strlen);
203 recv_tok.length = strlen;
204 /* If we're already complete - protocol error */
205 if (maj_status == GSS_S_COMPLETE)
206 packet_disconnect("Protocol error: received token when complete");
207 } else {
208 /* No token included */
209 if (maj_status != GSS_S_COMPLETE)
210 packet_disconnect("Protocol error: did not receive final token");
211 }
212 break;
213 case SSH2_MSG_KEXGSS_ERROR:
214 debug("Received Error");
215 maj_status = packet_get_int();
216 min_status = packet_get_int();
217 msg = packet_get_string(NULL);
218 lang = packet_get_string(NULL);
219 fatal("GSSAPI Error: \n%.400s",msg);
220 default:
221 packet_disconnect("Protocol error: didn't expect packet type %d",
222 type);
223 }
224 token_ptr = &recv_tok;
225 } else {
226 /* No data, and not complete */
227 if (maj_status != GSS_S_COMPLETE)
228 fatal("Not complete, and no token output");
229 }
230 } while (maj_status & GSS_S_CONTINUE_NEEDED);
231
232 /*
233 * We _must_ have received a COMPLETE message in reply from the
234 * server, which will have set dh_server_pub and msg_tok
235 */
236
237 if (type != SSH2_MSG_KEXGSS_COMPLETE)
238 fatal("Didn't receive a SSH2_MSG_KEXGSS_COMPLETE when I expected it");
239
240 /* Check f in range [1, p-1] */
241 if (!dh_pub_is_valid(dh, dh_server_pub))
242 packet_disconnect("bad server public DH value");
243
244 /* compute K=f^x mod p */
245 klen = DH_size(dh);
246 kbuf = xmalloc(klen);
247 kout = DH_compute_key(kbuf, dh_server_pub, dh);
248
249 shared_secret = BN_new();
250 BN_bin2bn(kbuf,kout, shared_secret);
251 memset(kbuf, 0, klen);
252 xfree(kbuf);
253
254 switch (kex->kex_type) {
255 case KEX_GSS_GRP1_SHA1:
256 case KEX_GSS_GRP14_SHA1:
257 kex_dh_hash( kex->client_version_string,
258 kex->server_version_string,
259 buffer_ptr(&kex->my), buffer_len(&kex->my),
260 buffer_ptr(&kex->peer), buffer_len(&kex->peer),
261 serverhostkey, slen, /* server host key */
262 dh->pub_key, /* e */
263 dh_server_pub, /* f */
264 shared_secret, /* K */
265 &hash, &hashlen
266 );
267 break;
268 case KEX_GSS_GEX_SHA1:
269 kexgex_hash(
270 kex->evp_md,
271 kex->client_version_string,
272 kex->server_version_string,
273 buffer_ptr(&kex->my), buffer_len(&kex->my),
274 buffer_ptr(&kex->peer), buffer_len(&kex->peer),
275 serverhostkey, slen,
276 min, nbits, max,
277 dh->p, dh->g,
278 dh->pub_key,
279 dh_server_pub,
280 shared_secret,
281 &hash, &hashlen
282 );
283 break;
284 default:
285 fatal("%s: Unexpected KEX type %d", __func__, kex->kex_type);
286 }
287
288 gssbuf.value = hash;
289 gssbuf.length = hashlen;
290
291 /* Verify that the hash matches the MIC we just got. */
292 if (GSS_ERROR(ssh_gssapi_checkmic(ctxt, &gssbuf, &msg_tok)))
293 packet_disconnect("Hash's MIC didn't verify");
294
295 xfree(msg_tok.value);
296
297 DH_free(dh);
298 if (serverhostkey)
299 xfree(serverhostkey);
300 BN_clear_free(dh_server_pub);
301
302 /* save session id */
303 if (kex->session_id == NULL) {
304 kex->session_id_len = hashlen;
305 kex->session_id = xmalloc(kex->session_id_len);
306 memcpy(kex->session_id, hash, kex->session_id_len);
307 }
308
309 if (gss_kex_context == NULL)
310 gss_kex_context = ctxt;
311 else
312 ssh_gssapi_delete_ctx(&ctxt);
313
314 kex_derive_keys(kex, hash, hashlen, shared_secret);
315 BN_clear_free(shared_secret);
316 kex_finish(kex);
317}
318
319#endif /* GSSAPI */
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