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1/*
2 * Copyright (c) 2001-2009 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 "sshbuf.h"
38#include "ssh2.h"
39#include "sshkey.h"
40#include "cipher.h"
41#include "kex.h"
42#include "log.h"
43#include "packet.h"
44#include "dh.h"
45#include "digest.h"
46
47#include "ssh-gss.h"
48
49int
50kexgss_client(struct ssh *ssh) {
51 gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER;
52 gss_buffer_desc recv_tok, gssbuf, msg_tok, *token_ptr;
53 Gssctxt *ctxt;
54 OM_uint32 maj_status, min_status, ret_flags;
55 u_int klen, kout, slen = 0, strlen;
56 DH *dh;
57 BIGNUM *dh_server_pub = NULL;
58 BIGNUM *shared_secret = NULL;
59 BIGNUM *p = NULL;
60 BIGNUM *g = NULL;
61 u_char *kbuf;
62 u_char *serverhostkey = NULL;
63 u_char *empty = "";
64 char *msg;
65 int type = 0;
66 int first = 1;
67 int nbits = 0, min = DH_GRP_MIN, max = DH_GRP_MAX;
68 u_char hash[SSH_DIGEST_MAX_LENGTH];
69 size_t hashlen;
70
71 /* Initialise our GSSAPI world */
72 ssh_gssapi_build_ctx(&ctxt);
73 if (ssh_gssapi_id_kex(ctxt, ssh->kex->name, ssh->kex->kex_type)
74 == GSS_C_NO_OID)
75 fatal("Couldn't identify host exchange");
76
77 if (ssh_gssapi_import_name(ctxt, ssh->kex->gss_host))
78 fatal("Couldn't import hostname");
79
80 if (ssh->kex->gss_client &&
81 ssh_gssapi_client_identity(ctxt, ssh->kex->gss_client))
82 fatal("Couldn't acquire client credentials");
83
84 switch (ssh->kex->kex_type) {
85 case KEX_GSS_GRP1_SHA1:
86 dh = dh_new_group1();
87 break;
88 case KEX_GSS_GRP14_SHA1:
89 dh = dh_new_group14();
90 break;
91 case KEX_GSS_GEX_SHA1:
92 debug("Doing group exchange\n");
93 nbits = dh_estimate(ssh->kex->we_need * 8);
94 packet_start(SSH2_MSG_KEXGSS_GROUPREQ);
95 packet_put_int(min);
96 packet_put_int(nbits);
97 packet_put_int(max);
98
99 packet_send();
100
101 packet_read_expect(SSH2_MSG_KEXGSS_GROUP);
102
103 if ((p = BN_new()) == NULL)
104 fatal("BN_new() failed");
105 packet_get_bignum2(p);
106 if ((g = BN_new()) == NULL)
107 fatal("BN_new() failed");
108 packet_get_bignum2(g);
109 packet_check_eom();
110
111 if (BN_num_bits(p) < min || BN_num_bits(p) > max)
112 fatal("GSSGRP_GEX group out of range: %d !< %d !< %d",
113 min, BN_num_bits(p), max);
114
115 dh = dh_new_group(g, p);
116 break;
117 default:
118 fatal("%s: Unexpected KEX type %d", __func__, ssh->kex->kex_type);
119 }
120
121 /* Step 1 - e is dh->pub_key */
122 dh_gen_key(dh, ssh->kex->we_need * 8);
123
124 /* This is f, we initialise it now to make life easier */
125 dh_server_pub = BN_new();
126 if (dh_server_pub == NULL)
127 fatal("dh_server_pub == NULL");
128
129 token_ptr = GSS_C_NO_BUFFER;
130
131 do {
132 debug("Calling gss_init_sec_context");
133
134 maj_status = ssh_gssapi_init_ctx(ctxt,
135 ssh->kex->gss_deleg_creds, token_ptr, &send_tok,
136 &ret_flags);
137
138 if (GSS_ERROR(maj_status)) {
139 if (send_tok.length != 0) {
140 packet_start(SSH2_MSG_KEXGSS_CONTINUE);
141 packet_put_string(send_tok.value,
142 send_tok.length);
143 }
144 fatal("gss_init_context failed");
145 }
146
147 /* If we've got an old receive buffer get rid of it */
148 if (token_ptr != GSS_C_NO_BUFFER)
149 free(recv_tok.value);
150
151 if (maj_status == GSS_S_COMPLETE) {
152 /* If mutual state flag is not true, kex fails */
153 if (!(ret_flags & GSS_C_MUTUAL_FLAG))
154 fatal("Mutual authentication failed");
155
156 /* If integ avail flag is not true kex fails */
157 if (!(ret_flags & GSS_C_INTEG_FLAG))
158 fatal("Integrity check failed");
159 }
160
161 /*
162 * If we have data to send, then the last message that we
163 * received cannot have been a 'complete'.
164 */
165 if (send_tok.length != 0) {
166 if (first) {
167 packet_start(SSH2_MSG_KEXGSS_INIT);
168 packet_put_string(send_tok.value,
169 send_tok.length);
170 packet_put_bignum2(dh->pub_key);
171 first = 0;
172 } else {
173 packet_start(SSH2_MSG_KEXGSS_CONTINUE);
174 packet_put_string(send_tok.value,
175 send_tok.length);
176 }
177 packet_send();
178 gss_release_buffer(&min_status, &send_tok);
179
180 /* If we've sent them data, they should reply */
181 do {
182 type = packet_read();
183 if (type == SSH2_MSG_KEXGSS_HOSTKEY) {
184 debug("Received KEXGSS_HOSTKEY");
185 if (serverhostkey)
186 fatal("Server host key received more than once");
187 serverhostkey =
188 packet_get_string(&slen);
189 }
190 } while (type == SSH2_MSG_KEXGSS_HOSTKEY);
191
192 switch (type) {
193 case SSH2_MSG_KEXGSS_CONTINUE:
194 debug("Received GSSAPI_CONTINUE");
195 if (maj_status == GSS_S_COMPLETE)
196 fatal("GSSAPI Continue received from server when complete");
197 recv_tok.value = packet_get_string(&strlen);
198 recv_tok.length = strlen;
199 break;
200 case SSH2_MSG_KEXGSS_COMPLETE:
201 debug("Received GSSAPI_COMPLETE");
202 packet_get_bignum2(dh_server_pub);
203 msg_tok.value = packet_get_string(&strlen);
204 msg_tok.length = strlen;
205
206 /* Is there a token included? */
207 if (packet_get_char()) {
208 recv_tok.value=
209 packet_get_string(&strlen);
210 recv_tok.length = strlen;
211 /* If we're already complete - protocol error */
212 if (maj_status == GSS_S_COMPLETE)
213 packet_disconnect("Protocol error: received token when complete");
214 } else {
215 /* No token included */
216 if (maj_status != GSS_S_COMPLETE)
217 packet_disconnect("Protocol error: did not receive final token");
218 }
219 break;
220 case SSH2_MSG_KEXGSS_ERROR:
221 debug("Received Error");
222 maj_status = packet_get_int();
223 min_status = packet_get_int();
224 msg = packet_get_string(NULL);
225 (void) packet_get_string_ptr(NULL);
226 fatal("GSSAPI Error: \n%.400s",msg);
227 default:
228 packet_disconnect("Protocol error: didn't expect packet type %d",
229 type);
230 }
231 token_ptr = &recv_tok;
232 } else {
233 /* No data, and not complete */
234 if (maj_status != GSS_S_COMPLETE)
235 fatal("Not complete, and no token output");
236 }
237 } while (maj_status & GSS_S_CONTINUE_NEEDED);
238
239 /*
240 * We _must_ have received a COMPLETE message in reply from the
241 * server, which will have set dh_server_pub and msg_tok
242 */
243
244 if (type != SSH2_MSG_KEXGSS_COMPLETE)
245 fatal("Didn't receive a SSH2_MSG_KEXGSS_COMPLETE when I expected it");
246
247 /* Check f in range [1, p-1] */
248 if (!dh_pub_is_valid(dh, dh_server_pub))
249 packet_disconnect("bad server public DH value");
250
251 /* compute K=f^x mod p */
252 klen = DH_size(dh);
253 kbuf = xmalloc(klen);
254 kout = DH_compute_key(kbuf, dh_server_pub, dh);
255 if (kout < 0)
256 fatal("DH_compute_key: failed");
257
258 shared_secret = BN_new();
259 if (shared_secret == NULL)
260 fatal("kexgss_client: BN_new failed");
261
262 if (BN_bin2bn(kbuf, kout, shared_secret) == NULL)
263 fatal("kexdh_client: BN_bin2bn failed");
264
265 memset(kbuf, 0, klen);
266 free(kbuf);
267
268 hashlen = sizeof(hash);
269 switch (ssh->kex->kex_type) {
270 case KEX_GSS_GRP1_SHA1:
271 case KEX_GSS_GRP14_SHA1:
272 kex_dh_hash(
273 ssh->kex->hash_alg,
274 ssh->kex->client_version_string,
275 ssh->kex->server_version_string,
276 sshbuf_ptr(ssh->kex->my), sshbuf_len(ssh->kex->my),
277 sshbuf_ptr(ssh->kex->peer), sshbuf_len(ssh->kex->peer),
278 (serverhostkey ? serverhostkey : empty), slen,
279 dh->pub_key, /* e */
280 dh_server_pub, /* f */
281 shared_secret, /* K */
282 hash, &hashlen
283 );
284 break;
285 case KEX_GSS_GEX_SHA1:
286 kexgex_hash(
287 ssh->kex->hash_alg,
288 ssh->kex->client_version_string,
289 ssh->kex->server_version_string,
290 sshbuf_ptr(ssh->kex->my), sshbuf_len(ssh->kex->my),
291 sshbuf_ptr(ssh->kex->peer), sshbuf_len(ssh->kex->peer),
292 (serverhostkey ? serverhostkey : empty), slen,
293 min, nbits, max,
294 dh->p, dh->g,
295 dh->pub_key,
296 dh_server_pub,
297 shared_secret,
298 hash, &hashlen
299 );
300 break;
301 default:
302 fatal("%s: Unexpected KEX type %d", __func__, ssh->kex->kex_type);
303 }
304
305 gssbuf.value = hash;
306 gssbuf.length = hashlen;
307
308 /* Verify that the hash matches the MIC we just got. */
309 if (GSS_ERROR(ssh_gssapi_checkmic(ctxt, &gssbuf, &msg_tok)))
310 packet_disconnect("Hash's MIC didn't verify");
311
312 free(msg_tok.value);
313
314 DH_free(dh);
315 free(serverhostkey);
316 BN_clear_free(dh_server_pub);
317
318 /* save session id */
319 if (ssh->kex->session_id == NULL) {
320 ssh->kex->session_id_len = hashlen;
321 ssh->kex->session_id = xmalloc(ssh->kex->session_id_len);
322 memcpy(ssh->kex->session_id, hash, ssh->kex->session_id_len);
323 }
324
325 if (ssh->kex->gss_deleg_creds)
326 ssh_gssapi_credentials_updated(ctxt);
327
328 if (gss_kex_context == NULL)
329 gss_kex_context = ctxt;
330 else
331 ssh_gssapi_delete_ctx(&ctxt);
332
333 kex_derive_keys_bn(ssh, hash, hashlen, shared_secret);
334 BN_clear_free(shared_secret);
335 return kex_send_newkeys(ssh);
336}
337
338#endif /* GSSAPI */