1 /*
2 * Copyright (c) 2001-2003 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 * Copyright 2008 Sun Microsystems, Inc. All rights reserved.
26 * Use is subject to license terms.
27 */
28
29 #pragma ident "%Z%%M% %I% %E% SMI"
30
31
32 #include "includes.h"
33
34 #ifdef GSSAPI
35
36 #include <openssl/opensslconf.h>
37 #include <openssl/crypto.h>
38 #include <openssl/bn.h>
39
40 #include "xmalloc.h"
41 #include "buffer.h"
42 #include "bufaux.h"
43 #include "kex.h"
44 #include "log.h"
45 #include "packet.h"
46 #include "dh.h"
47 #include "canohost.h"
48 #include "ssh2.h"
49 #include "ssh-gss.h"
50
51 extern char *xxx_host;
52
53 Gssctxt *xxx_gssctxt;
54
55 static void kexgss_verbose_cleanup(void *arg);
56
57 void
58 kexgss_client(Kex *kex)
59 {
60 gss_buffer_desc gssbuf, send_tok, recv_tok, msg_tok;
61 gss_buffer_t token_ptr;
62 gss_OID mech = GSS_C_NULL_OID;
63 Gssctxt *ctxt = NULL;
64 OM_uint32 maj_status, min_status, smaj_status, smin_status;
65 unsigned int klen, kout;
66 DH *dh;
67 BIGNUM *dh_server_pub = 0;
68 BIGNUM *shared_secret = 0;
69 Key *server_host_key = NULL;
70 unsigned char *kbuf;
71 unsigned char *hash;
72 unsigned char *server_host_key_blob = NULL;
73 char *msg, *lang;
74 int type = 0;
75 int first = 1;
76 uint_t sbloblen = 0;
77 uint_t strlen;
78
79 /* Map the negotiated kex name to a mech OID */
80 ssh_gssapi_oid_of_kexname(kex->name, &mech);
81 if (mech == GSS_C_NULL_OID)
82 fatal("Couldn't match the negotiated GSS key exchange");
83
84 ssh_gssapi_build_ctx(&ctxt, 1, mech);
85
86 /* This code should match that in ssh_dh1_client */
87
88 /* Step 1 - e is dh->pub_key */
89 dh = dh_new_group1();
90 dh_gen_key(dh, kex->we_need * 8);
91
92 /* This is f, we initialise it now to make life easier */
93 dh_server_pub = BN_new();
94 if (dh_server_pub == NULL) {
95 fatal("dh_server_pub == NULL");
96 }
97
98 token_ptr = GSS_C_NO_BUFFER;
99
100 recv_tok.value = NULL;
101 recv_tok.length = 0;
102
103 do {
104 debug("Calling gss_init_sec_context");
105
106 maj_status = ssh_gssapi_init_ctx(ctxt, xxx_host,
107 kex->options.gss_deleg_creds, token_ptr, &send_tok);
108
109 if (GSS_ERROR(maj_status)) {
110 ssh_gssapi_error(ctxt, "performing GSS-API protected "
111 "SSHv2 key exchange");
112 (void) gss_release_buffer(&min_status, &send_tok);
113 packet_disconnect("A GSS-API error occurred during "
114 "GSS-API protected SSHv2 key exchange\n");
115 }
116
117 /* If we've got an old receive buffer get rid of it */
118 if (token_ptr != GSS_C_NO_BUFFER) {
119 /* We allocated recv_tok */
120 xfree(recv_tok.value);
121 recv_tok.value = NULL;
122 recv_tok.length = 0;
123 token_ptr = GSS_C_NO_BUFFER;
124 }
125
126 if (maj_status == GSS_S_COMPLETE) {
127 /* If mutual state flag is not true, kex fails */
128 if (!(ctxt->flags & GSS_C_MUTUAL_FLAG)) {
129 fatal("Mutual authentication failed");
130 }
131 /* If integ avail flag is not true kex fails */
132 if (!(ctxt->flags & GSS_C_INTEG_FLAG)) {
133 fatal("Integrity check failed");
134 }
135 }
136
137 /*
138 * If we have data to send, then the last message that we
139 * received cannot have been a 'complete'.
140 */
141 if (send_tok.length != 0) {
142 if (first) {
143 packet_start(SSH2_MSG_KEXGSS_INIT);
144 packet_put_string(send_tok.value,
145 send_tok.length);
146 packet_put_bignum2(dh->pub_key);
147 first = 0;
148 } else {
149 packet_start(SSH2_MSG_KEXGSS_CONTINUE);
150 packet_put_string(send_tok.value,
151 send_tok.length);
152 }
153 (void) gss_release_buffer(&min_status, &send_tok);
154 packet_send();
155 packet_write_wait();
156
157
158 /*
159 * If we've sent them data, they'd better be polite and
160 * reply.
161 */
162
163 next_packet:
164 /*
165 * We need to catch connection closing w/o error
166 * tokens or messages so we can tell the user
167 * _something_ more useful than "Connection
168 * closed by ..."
169 *
170 * We use a fatal cleanup function as that's
171 * all, really, that we can do for now.
172 */
173 fatal_add_cleanup(kexgss_verbose_cleanup, NULL);
174 type = packet_read();
175 fatal_remove_cleanup(kexgss_verbose_cleanup, NULL);
176 switch (type) {
177 case SSH2_MSG_KEXGSS_HOSTKEY:
178 debug("Received KEXGSS_HOSTKEY");
179 server_host_key_blob =
180 packet_get_string(&sbloblen);
181 server_host_key =
182 key_from_blob(server_host_key_blob,
183 sbloblen);
184 goto next_packet; /* there MUSt be another */
185 break;
186 case SSH2_MSG_KEXGSS_CONTINUE:
187 debug("Received GSSAPI_CONTINUE");
188 if (maj_status == GSS_S_COMPLETE)
189 packet_disconnect("Protocol error: "
190 "received GSS-API context token "
191 "though the context was already "
192 "established");
193 recv_tok.value = packet_get_string(&strlen);
194 recv_tok.length = strlen; /* u_int vs. size_t */
195 break;
196 case SSH2_MSG_KEXGSS_COMPLETE:
197 debug("Received GSSAPI_COMPLETE");
198 packet_get_bignum2(dh_server_pub);
199 msg_tok.value = packet_get_string(&strlen);
200 msg_tok.length = strlen; /* u_int vs. size_t */
201
202 /* Is there a token included? */
203 if (packet_get_char()) {
204 recv_tok.value =
205 packet_get_string(&strlen);
206 /* u_int/size_t */
207 recv_tok.length = strlen;
208 }
209 if (recv_tok.length > 0 &&
210 maj_status == GSS_S_COMPLETE) {
211 packet_disconnect("Protocol error: "
212 "received GSS-API context token "
213 "though the context was already "
214 "established");
215 } else if (recv_tok.length == 0 &&
216 maj_status == GSS_S_CONTINUE_NEEDED) {
217 /* No token included */
218 packet_disconnect("Protocol error: "
219 "did not receive expected "
220 "GSS-API context token");
221 }
222 break;
223 case SSH2_MSG_KEXGSS_ERROR:
224 smaj_status = packet_get_int();
225 smin_status = packet_get_int();
226 msg = packet_get_string(NULL);
227 lang = packet_get_string(NULL);
228 xfree(lang);
229 error("Server had a GSS-API error; the "
230 "connection will close (%d/%d):\n%s",
231 smaj_status, smin_status, msg);
232 error("Use the GssKeyEx option to disable "
233 "GSS-API key exchange and try again.");
234 packet_disconnect("The server had a GSS-API "
235 "error during GSS-API protected SSHv2 "
236 "key exchange\n");
237 break;
238 default:
239 packet_disconnect("Protocol error: "
240 "didn't expect packet type %d", type);
241 }
242 if (recv_tok.value)
243 token_ptr = &recv_tok;
244 } else {
245 /* No data, and not complete */
246 if (maj_status != GSS_S_COMPLETE) {
247 fatal("Not complete, and no token output");
248 }
249 }
250 } while (maj_status == GSS_S_CONTINUE_NEEDED);
251
252 /*
253 * We _must_ have received a COMPLETE message in reply from the
254 * server, which will have set dh_server_pub and msg_tok.
255 */
256 if (type != SSH2_MSG_KEXGSS_COMPLETE)
257 fatal("Expected SSH2_MSG_KEXGSS_COMPLETE never arrived");
258 if (maj_status != GSS_S_COMPLETE)
259 fatal("Internal error in GSS-API protected SSHv2 key exchange");
260
261 /* Check f in range [1, p-1] */
262 if (!dh_pub_is_valid(dh, dh_server_pub))
263 packet_disconnect("bad server public DH value");
264
265 /* compute K=f^x mod p */
266 klen = DH_size(dh);
267 kbuf = xmalloc(klen);
268 kout = DH_compute_key(kbuf, dh_server_pub, dh);
269
270 shared_secret = BN_new();
271 BN_bin2bn(kbuf, kout, shared_secret);
272 (void) memset(kbuf, 0, klen);
273 xfree(kbuf);
274
275 /* The GSS hash is identical to the DH one */
276 hash = kex_dh_hash(
277 kex->client_version_string,
278 kex->server_version_string,
279 buffer_ptr(&kex->my), buffer_len(&kex->my),
280 buffer_ptr(&kex->peer), buffer_len(&kex->peer),
281 server_host_key_blob, sbloblen, /* server host key */
282 dh->pub_key, /* e */
283 dh_server_pub, /* f */
284 shared_secret); /* K */
285
286 gssbuf.value = hash;
287 gssbuf.length = 20;
288
289 /* Verify that H matches the token we just got. */
290 if ((maj_status = gss_verify_mic(&min_status, ctxt->context, &gssbuf,
291 &msg_tok, NULL))) {
292 packet_disconnect("Hash's MIC didn't verify");
293 }
294
295 if (server_host_key && kex->accept_host_key != NULL)
296 (void) kex->accept_host_key(server_host_key);
297
298 DH_free(dh);
299
300 xxx_gssctxt = ctxt; /* for gss keyex w/ mic userauth */
301
302 /* save session id */
303 if (kex->session_id == NULL) {
304 kex->session_id_len = 20;
305 kex->session_id = xmalloc(kex->session_id_len);
306 (void) memcpy(kex->session_id, hash, kex->session_id_len);
307 }
308
309 kex_derive_keys(kex, hash, shared_secret);
310 BN_clear_free(shared_secret);
311 kex_finish(kex);
312 }
313
314 /* ARGSUSED */
315 static
316 void
317 kexgss_verbose_cleanup(void *arg)
318 {
319 error("The GSS-API protected key exchange has failed without "
320 "indication\nfrom the server, possibly due to misconfiguration "
321 "of the server.");
322 error("Use the GssKeyEx option to disable GSS-API key exchange "
323 "and try again.");
324 }
325
326 #endif /* GSSAPI */