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Damien Miller6fd6def2005-11-05 15:07:05 +11001/* $OpenBSD: auth2-gss.c,v 1.12 2005/10/13 22:24:31 stevesk Exp $ */
Darren Tucker0efd1552003-08-26 11:49:55 +10002
3/*
4 * Copyright (c) 2001-2003 Simon Wilkinson. 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#ifdef GSSAPI
30
31#include "auth.h"
32#include "ssh2.h"
33#include "xmalloc.h"
34#include "log.h"
35#include "dispatch.h"
36#include "servconf.h"
Darren Tucker0efd1552003-08-26 11:49:55 +100037#include "packet.h"
38#include "monitor_wrap.h"
39
40#include "ssh-gss.h"
41
42extern ServerOptions options;
43
44static void input_gssapi_token(int type, u_int32_t plen, void *ctxt);
Damien Miller0425d402003-11-17 22:18:21 +110045static void input_gssapi_mic(int type, u_int32_t plen, void *ctxt);
Darren Tucker0efd1552003-08-26 11:49:55 +100046static void input_gssapi_exchange_complete(int type, u_int32_t plen, void *ctxt);
47static void input_gssapi_errtok(int, u_int32_t, void *);
48
49/*
50 * We only support those mechanisms that we know about (ie ones that we know
Damien Miller6fd6def2005-11-05 15:07:05 +110051 * how to check local user kuserok and the like)
Darren Tucker0efd1552003-08-26 11:49:55 +100052 */
53static int
54userauth_gssapi(Authctxt *authctxt)
55{
Darren Tucker3f9fdc72004-06-22 12:56:01 +100056 gss_OID_desc goid = {0, NULL};
Darren Tucker0efd1552003-08-26 11:49:55 +100057 Gssctxt *ctxt = NULL;
58 int mechs;
59 gss_OID_set supported;
60 int present;
61 OM_uint32 ms;
62 u_int len;
Damien Millereccb9de2005-06-17 12:59:34 +100063 u_char *doid = NULL;
Darren Tucker0efd1552003-08-26 11:49:55 +100064
65 if (!authctxt->valid || authctxt->user == NULL)
66 return (0);
67
68 mechs = packet_get_int();
69 if (mechs == 0) {
70 debug("Mechanism negotiation is not supported");
71 return (0);
72 }
73
74 ssh_gssapi_supported_oids(&supported);
75 do {
76 mechs--;
77
78 if (doid)
79 xfree(doid);
80
Darren Tucker655a5e02003-11-03 20:09:03 +110081 present = 0;
Darren Tucker0efd1552003-08-26 11:49:55 +100082 doid = packet_get_string(&len);
83
Damien Miller0dc1bef2005-07-17 17:22:45 +100084 if (len > 2 && doid[0] == SSH_GSS_OIDTYPE &&
85 doid[1] == len - 2) {
Darren Tucker3f9fdc72004-06-22 12:56:01 +100086 goid.elements = doid + 2;
87 goid.length = len - 2;
88 gss_test_oid_set_member(&ms, &goid, supported,
Darren Tucker655a5e02003-11-03 20:09:03 +110089 &present);
Darren Tucker0efd1552003-08-26 11:49:55 +100090 } else {
Darren Tucker655a5e02003-11-03 20:09:03 +110091 logit("Badly formed OID received");
Darren Tucker0efd1552003-08-26 11:49:55 +100092 }
Darren Tucker0efd1552003-08-26 11:49:55 +100093 } while (mechs > 0 && !present);
94
95 gss_release_oid_set(&ms, &supported);
96
97 if (!present) {
98 xfree(doid);
99 return (0);
100 }
101
Darren Tucker3f9fdc72004-06-22 12:56:01 +1000102 if (GSS_ERROR(PRIVSEP(ssh_gssapi_server_ctx(&ctxt, &goid)))) {
Damien Miller982d3262003-09-02 22:59:01 +1000103 xfree(doid);
Darren Tucker0efd1552003-08-26 11:49:55 +1000104 return (0);
Damien Miller982d3262003-09-02 22:59:01 +1000105 }
Darren Tucker0efd1552003-08-26 11:49:55 +1000106
Damien Miller6fd6def2005-11-05 15:07:05 +1100107 authctxt->methoddata = (void *)ctxt;
Darren Tucker0efd1552003-08-26 11:49:55 +1000108
109 packet_start(SSH2_MSG_USERAUTH_GSSAPI_RESPONSE);
110
Darren Tucker655a5e02003-11-03 20:09:03 +1100111 /* Return the OID that we received */
Darren Tucker0efd1552003-08-26 11:49:55 +1000112 packet_put_string(doid, len);
113
114 packet_send();
115 xfree(doid);
116
117 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, &input_gssapi_token);
118 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, &input_gssapi_errtok);
119 authctxt->postponed = 1;
120
121 return (0);
122}
123
124static void
125input_gssapi_token(int type, u_int32_t plen, void *ctxt)
126{
127 Authctxt *authctxt = ctxt;
128 Gssctxt *gssctxt;
129 gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER;
130 gss_buffer_desc recv_tok;
Damien Miller0425d402003-11-17 22:18:21 +1100131 OM_uint32 maj_status, min_status, flags;
Darren Tucker0efd1552003-08-26 11:49:55 +1000132 u_int len;
133
134 if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep))
135 fatal("No authentication or GSSAPI context");
136
137 gssctxt = authctxt->methoddata;
138 recv_tok.value = packet_get_string(&len);
139 recv_tok.length = len; /* u_int vs. size_t */
140
141 packet_check_eom();
142
143 maj_status = PRIVSEP(ssh_gssapi_accept_ctx(gssctxt, &recv_tok,
Damien Miller0425d402003-11-17 22:18:21 +1100144 &send_tok, &flags));
Darren Tucker0efd1552003-08-26 11:49:55 +1000145
146 xfree(recv_tok.value);
147
148 if (GSS_ERROR(maj_status)) {
149 if (send_tok.length != 0) {
150 packet_start(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK);
151 packet_put_string(send_tok.value, send_tok.length);
152 packet_send();
153 }
154 authctxt->postponed = 0;
155 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
Damien Miller0425d402003-11-17 22:18:21 +1100156 userauth_finish(authctxt, 0, "gssapi-with-mic");
Darren Tucker0efd1552003-08-26 11:49:55 +1000157 } else {
158 if (send_tok.length != 0) {
159 packet_start(SSH2_MSG_USERAUTH_GSSAPI_TOKEN);
160 packet_put_string(send_tok.value, send_tok.length);
161 packet_send();
162 }
163 if (maj_status == GSS_S_COMPLETE) {
164 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
Damien Miller0425d402003-11-17 22:18:21 +1100165 if (flags & GSS_C_INTEG_FLAG)
166 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_MIC,
167 &input_gssapi_mic);
168 else
169 dispatch_set(
170 SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE,
171 &input_gssapi_exchange_complete);
Darren Tucker0efd1552003-08-26 11:49:55 +1000172 }
173 }
174
175 gss_release_buffer(&min_status, &send_tok);
176}
177
178static void
179input_gssapi_errtok(int type, u_int32_t plen, void *ctxt)
180{
181 Authctxt *authctxt = ctxt;
182 Gssctxt *gssctxt;
183 gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER;
184 gss_buffer_desc recv_tok;
185 OM_uint32 maj_status;
Damien Miller55c47ed2003-09-02 22:14:07 +1000186 u_int len;
Darren Tucker0efd1552003-08-26 11:49:55 +1000187
188 if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep))
189 fatal("No authentication or GSSAPI context");
190
191 gssctxt = authctxt->methoddata;
Damien Miller55c47ed2003-09-02 22:14:07 +1000192 recv_tok.value = packet_get_string(&len);
193 recv_tok.length = len;
Darren Tucker0efd1552003-08-26 11:49:55 +1000194
195 packet_check_eom();
196
197 /* Push the error token into GSSAPI to see what it says */
198 maj_status = PRIVSEP(ssh_gssapi_accept_ctx(gssctxt, &recv_tok,
199 &send_tok, NULL));
200
201 xfree(recv_tok.value);
202
203 /* We can't return anything to the client, even if we wanted to */
204 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
205 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL);
206
207 /* The client will have already moved on to the next auth */
208
209 gss_release_buffer(&maj_status, &send_tok);
210}
211
212/*
213 * This is called when the client thinks we've completed authentication.
214 * It should only be enabled in the dispatch handler by the function above,
215 * which only enables it once the GSSAPI exchange is complete.
216 */
217
218static void
219input_gssapi_exchange_complete(int type, u_int32_t plen, void *ctxt)
220{
221 Authctxt *authctxt = ctxt;
222 Gssctxt *gssctxt;
223 int authenticated;
224
225 if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep))
226 fatal("No authentication or GSSAPI context");
227
228 gssctxt = authctxt->methoddata;
229
230 /*
Damien Miller0425d402003-11-17 22:18:21 +1100231 * We don't need to check the status, because we're only enabled in
232 * the dispatcher once the exchange is complete
Darren Tucker0efd1552003-08-26 11:49:55 +1000233 */
234
235 packet_check_eom();
236
237 authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user));
238
239 authctxt->postponed = 0;
240 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
241 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL);
Damien Miller0425d402003-11-17 22:18:21 +1100242 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_MIC, NULL);
Darren Tucker0efd1552003-08-26 11:49:55 +1000243 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL);
Damien Miller0425d402003-11-17 22:18:21 +1100244 userauth_finish(authctxt, authenticated, "gssapi-with-mic");
245}
246
247static void
248input_gssapi_mic(int type, u_int32_t plen, void *ctxt)
249{
250 Authctxt *authctxt = ctxt;
251 Gssctxt *gssctxt;
252 int authenticated = 0;
253 Buffer b;
254 gss_buffer_desc mic, gssbuf;
255 u_int len;
Damien Miller787b2ec2003-11-21 23:56:47 +1100256
Damien Miller0425d402003-11-17 22:18:21 +1100257 if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep))
258 fatal("No authentication or GSSAPI context");
Damien Miller787b2ec2003-11-21 23:56:47 +1100259
Damien Miller0425d402003-11-17 22:18:21 +1100260 gssctxt = authctxt->methoddata;
Damien Miller787b2ec2003-11-21 23:56:47 +1100261
Damien Miller0425d402003-11-17 22:18:21 +1100262 mic.value = packet_get_string(&len);
263 mic.length = len;
Damien Miller787b2ec2003-11-21 23:56:47 +1100264
Damien Miller0425d402003-11-17 22:18:21 +1100265 ssh_gssapi_buildmic(&b, authctxt->user, authctxt->service,
266 "gssapi-with-mic");
Damien Miller787b2ec2003-11-21 23:56:47 +1100267
Damien Miller0425d402003-11-17 22:18:21 +1100268 gssbuf.value = buffer_ptr(&b);
269 gssbuf.length = buffer_len(&b);
Damien Miller787b2ec2003-11-21 23:56:47 +1100270
Damien Miller0425d402003-11-17 22:18:21 +1100271 if (!GSS_ERROR(PRIVSEP(ssh_gssapi_checkmic(gssctxt, &gssbuf, &mic))))
272 authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user));
273 else
274 logit("GSSAPI MIC check failed");
275
276 buffer_free(&b);
277 xfree(mic.value);
Damien Miller787b2ec2003-11-21 23:56:47 +1100278
Damien Miller0425d402003-11-17 22:18:21 +1100279 authctxt->postponed = 0;
280 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
281 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL);
282 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_MIC, NULL);
283 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL);
284 userauth_finish(authctxt, authenticated, "gssapi-with-mic");
Darren Tucker0efd1552003-08-26 11:49:55 +1000285}
286
287Authmethod method_gssapi = {
Damien Miller0425d402003-11-17 22:18:21 +1100288 "gssapi-with-mic",
Darren Tucker0efd1552003-08-26 11:49:55 +1000289 userauth_gssapi,
290 &options.gss_authentication
291};
292
293#endif /* GSSAPI */