1/* $OpenBSD: auth2-gss.c,v 1.22 2015/01/19 20:07:45 markus Exp $ */
2
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 <sys/types.h>
32
33#include <stdarg.h>
34
35#include "xmalloc.h"
36#include "key.h"
37#include "hostfile.h"
38#include "auth.h"
39#include "ssh2.h"
40#include "log.h"
41#include "dispatch.h"
42#include "buffer.h"
43#include "misc.h"
44#include "servconf.h"
45#include "packet.h"
46#include "ssh-gss.h"
47#include "monitor_wrap.h"
48
49extern ServerOptions options;
50
51static int input_gssapi_token(int type, u_int32_t plen, void *ctxt);
52static int input_gssapi_mic(int type, u_int32_t plen, void *ctxt);
53static int input_gssapi_exchange_complete(int type, u_int32_t plen, void *ctxt);
54static int input_gssapi_errtok(int, u_int32_t, void *);
55
56/*
57 * We only support those mechanisms that we know about (ie ones that we know
58 * how to check local user kuserok and the like)
59 */
60static int
61userauth_gssapi(Authctxt *authctxt)
62{
63	gss_OID_desc goid = {0, NULL};
64	Gssctxt *ctxt = NULL;
65	int mechs;
66	int present;
67	OM_uint32 ms;
68	u_int len;
69	u_char *doid = NULL;
70
71	if (!authctxt->valid || authctxt->user == NULL)
72		return (0);
73
74	mechs = packet_get_int();
75	if (mechs == 0) {
76		debug("Mechanism negotiation is not supported");
77		return (0);
78	}
79
80	do {
81		mechs--;
82
83		free(doid);
84
85		present = 0;
86		doid = packet_get_string(&len);
87
88		if (len > 2 && doid[0] == SSH_GSS_OIDTYPE &&
89		    doid[1] == len - 2) {
90			goid.elements = doid + 2;
91			goid.length   = len - 2;
92			ssh_gssapi_test_oid_supported(&ms, &goid, &present);
93		} else {
94			logit("Badly formed OID received");
95		}
96	} while (mechs > 0 && !present);
97
98	if (!present) {
99		free(doid);
100		authctxt->server_caused_failure = 1;
101		return (0);
102	}
103
104	if (GSS_ERROR(PRIVSEP(ssh_gssapi_server_ctx(&ctxt, &goid)))) {
105		if (ctxt != NULL)
106			ssh_gssapi_delete_ctx(&ctxt);
107		free(doid);
108		authctxt->server_caused_failure = 1;
109		return (0);
110	}
111
112	authctxt->methoddata = (void *)ctxt;
113
114	packet_start(SSH2_MSG_USERAUTH_GSSAPI_RESPONSE);
115
116	/* Return the OID that we received */
117	packet_put_string(doid, len);
118
119	packet_send();
120	free(doid);
121
122	dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, &input_gssapi_token);
123	dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, &input_gssapi_errtok);
124	authctxt->postponed = 1;
125
126	return (0);
127}
128
129static int
130input_gssapi_token(int type, u_int32_t plen, void *ctxt)
131{
132	Authctxt *authctxt = ctxt;
133	Gssctxt *gssctxt;
134	gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER;
135	gss_buffer_desc recv_tok;
136	OM_uint32 maj_status, min_status, flags;
137	u_int len;
138
139	if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep))
140		fatal("No authentication or GSSAPI context");
141
142	gssctxt = authctxt->methoddata;
143	recv_tok.value = packet_get_string(&len);
144	recv_tok.length = len; /* u_int vs. size_t */
145
146	packet_check_eom();
147
148	maj_status = PRIVSEP(ssh_gssapi_accept_ctx(gssctxt, &recv_tok,
149	    &send_tok, &flags));
150
151	free(recv_tok.value);
152
153	if (GSS_ERROR(maj_status)) {
154		if (send_tok.length != 0) {
155			packet_start(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK);
156			packet_put_string(send_tok.value, send_tok.length);
157			packet_send();
158		}
159		authctxt->postponed = 0;
160		dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
161		userauth_finish(authctxt, 0, "gssapi-with-mic", NULL);
162	} else {
163		if (send_tok.length != 0) {
164			packet_start(SSH2_MSG_USERAUTH_GSSAPI_TOKEN);
165			packet_put_string(send_tok.value, send_tok.length);
166			packet_send();
167		}
168		if (maj_status == GSS_S_COMPLETE) {
169			dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
170			if (flags & GSS_C_INTEG_FLAG)
171				dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_MIC,
172				    &input_gssapi_mic);
173			else
174				dispatch_set(
175				    SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE,
176				    &input_gssapi_exchange_complete);
177		}
178	}
179
180	gss_release_buffer(&min_status, &send_tok);
181	return 0;
182}
183
184static int
185input_gssapi_errtok(int type, u_int32_t plen, void *ctxt)
186{
187	Authctxt *authctxt = ctxt;
188	Gssctxt *gssctxt;
189	gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER;
190	gss_buffer_desc recv_tok;
191	OM_uint32 maj_status;
192	u_int len;
193
194	if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep))
195		fatal("No authentication or GSSAPI context");
196
197	gssctxt = authctxt->methoddata;
198	recv_tok.value = packet_get_string(&len);
199	recv_tok.length = len;
200
201	packet_check_eom();
202
203	/* Push the error token into GSSAPI to see what it says */
204	maj_status = PRIVSEP(ssh_gssapi_accept_ctx(gssctxt, &recv_tok,
205	    &send_tok, NULL));
206
207	free(recv_tok.value);
208
209	/* We can't return anything to the client, even if we wanted to */
210	dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
211	dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL);
212
213	/* The client will have already moved on to the next auth */
214
215	gss_release_buffer(&maj_status, &send_tok);
216	return 0;
217}
218
219/*
220 * This is called when the client thinks we've completed authentication.
221 * It should only be enabled in the dispatch handler by the function above,
222 * which only enables it once the GSSAPI exchange is complete.
223 */
224
225static int
226input_gssapi_exchange_complete(int type, u_int32_t plen, void *ctxt)
227{
228	Authctxt *authctxt = ctxt;
229	int authenticated;
230
231	if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep))
232		fatal("No authentication or GSSAPI context");
233
234	/*
235	 * We don't need to check the status, because we're only enabled in
236	 * the dispatcher once the exchange is complete
237	 */
238
239	packet_check_eom();
240
241	authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user));
242
243	authctxt->postponed = 0;
244	dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
245	dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL);
246	dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_MIC, NULL);
247	dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL);
248	userauth_finish(authctxt, authenticated, "gssapi-with-mic", NULL);
249	return 0;
250}
251
252static int
253input_gssapi_mic(int type, u_int32_t plen, void *ctxt)
254{
255	Authctxt *authctxt = ctxt;
256	Gssctxt *gssctxt;
257	int authenticated = 0;
258	Buffer b;
259	gss_buffer_desc mic, gssbuf;
260	u_int len;
261
262	if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep))
263		fatal("No authentication or GSSAPI context");
264
265	gssctxt = authctxt->methoddata;
266
267	mic.value = packet_get_string(&len);
268	mic.length = len;
269
270	ssh_gssapi_buildmic(&b, authctxt->user, authctxt->service,
271	    "gssapi-with-mic");
272
273	gssbuf.value = buffer_ptr(&b);
274	gssbuf.length = buffer_len(&b);
275
276	if (!GSS_ERROR(PRIVSEP(ssh_gssapi_checkmic(gssctxt, &gssbuf, &mic))))
277		authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user));
278	else
279		logit("GSSAPI MIC check failed");
280
281	buffer_free(&b);
282	free(mic.value);
283
284	authctxt->postponed = 0;
285	dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
286	dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL);
287	dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_MIC, NULL);
288	dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL);
289	userauth_finish(authctxt, authenticated, "gssapi-with-mic", NULL);
290	return 0;
291}
292
293Authmethod method_gssapi = {
294	"gssapi-with-mic",
295	userauth_gssapi,
296	&options.gss_authentication
297};
298
299#endif /* GSSAPI */
300