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