xref: /freebsd/crypto/openssh/auth2-gss.c (revision 8d20be1e22095c27faf8fe8b2f0d089739cc742e)
1 /* $OpenBSD: auth2-gss.c,v 1.20 2013/05/17 00:13:13 djm 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 "servconf.h"
44 #include "packet.h"
45 #include "ssh-gss.h"
46 #include "monitor_wrap.h"
47 
48 extern ServerOptions options;
49 
50 static void input_gssapi_token(int type, u_int32_t plen, void *ctxt);
51 static void input_gssapi_mic(int type, u_int32_t plen, void *ctxt);
52 static void input_gssapi_exchange_complete(int type, u_int32_t plen, void *ctxt);
53 static void input_gssapi_errtok(int, u_int32_t, void *);
54 
55 /*
56  * We only support those mechanisms that we know about (ie ones that we know
57  * how to check local user kuserok and the like)
58  */
59 static int
60 userauth_gssapi(Authctxt *authctxt)
61 {
62 	gss_OID_desc goid = {0, NULL};
63 	Gssctxt *ctxt = NULL;
64 	int mechs;
65 	gss_OID_set supported;
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 	ssh_gssapi_supported_oids(&supported);
81 	do {
82 		mechs--;
83 
84 		free(doid);
85 
86 		present = 0;
87 		doid = packet_get_string(&len);
88 
89 		if (len > 2 && doid[0] == SSH_GSS_OIDTYPE &&
90 		    doid[1] == len - 2) {
91 			goid.elements = doid + 2;
92 			goid.length   = len - 2;
93 			gss_test_oid_set_member(&ms, &goid, supported,
94 			    &present);
95 		} else {
96 			logit("Badly formed OID received");
97 		}
98 	} while (mechs > 0 && !present);
99 
100 	gss_release_oid_set(&ms, &supported);
101 
102 	if (!present) {
103 		free(doid);
104 		authctxt->server_caused_failure = 1;
105 		return (0);
106 	}
107 
108 	if (GSS_ERROR(PRIVSEP(ssh_gssapi_server_ctx(&ctxt, &goid)))) {
109 		if (ctxt != NULL)
110 			ssh_gssapi_delete_ctx(&ctxt);
111 		free(doid);
112 		authctxt->server_caused_failure = 1;
113 		return (0);
114 	}
115 
116 	authctxt->methoddata = (void *)ctxt;
117 
118 	packet_start(SSH2_MSG_USERAUTH_GSSAPI_RESPONSE);
119 
120 	/* Return the OID that we received */
121 	packet_put_string(doid, len);
122 
123 	packet_send();
124 	free(doid);
125 
126 	dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, &input_gssapi_token);
127 	dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, &input_gssapi_errtok);
128 	authctxt->postponed = 1;
129 
130 	return (0);
131 }
132 
133 static void
134 input_gssapi_token(int type, u_int32_t plen, void *ctxt)
135 {
136 	Authctxt *authctxt = ctxt;
137 	Gssctxt *gssctxt;
138 	gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER;
139 	gss_buffer_desc recv_tok;
140 	OM_uint32 maj_status, min_status, flags;
141 	u_int len;
142 
143 	if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep))
144 		fatal("No authentication or GSSAPI context");
145 
146 	gssctxt = authctxt->methoddata;
147 	recv_tok.value = packet_get_string(&len);
148 	recv_tok.length = len; /* u_int vs. size_t */
149 
150 	packet_check_eom();
151 
152 	maj_status = PRIVSEP(ssh_gssapi_accept_ctx(gssctxt, &recv_tok,
153 	    &send_tok, &flags));
154 
155 	free(recv_tok.value);
156 
157 	if (GSS_ERROR(maj_status)) {
158 		if (send_tok.length != 0) {
159 			packet_start(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK);
160 			packet_put_string(send_tok.value, send_tok.length);
161 			packet_send();
162 		}
163 		authctxt->postponed = 0;
164 		dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
165 		userauth_finish(authctxt, 0, "gssapi-with-mic", NULL);
166 	} else {
167 		if (send_tok.length != 0) {
168 			packet_start(SSH2_MSG_USERAUTH_GSSAPI_TOKEN);
169 			packet_put_string(send_tok.value, send_tok.length);
170 			packet_send();
171 		}
172 		if (maj_status == GSS_S_COMPLETE) {
173 			dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
174 			if (flags & GSS_C_INTEG_FLAG)
175 				dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_MIC,
176 				    &input_gssapi_mic);
177 			else
178 				dispatch_set(
179 				    SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE,
180 				    &input_gssapi_exchange_complete);
181 		}
182 	}
183 
184 	gss_release_buffer(&min_status, &send_tok);
185 }
186 
187 static void
188 input_gssapi_errtok(int type, u_int32_t plen, void *ctxt)
189 {
190 	Authctxt *authctxt = ctxt;
191 	Gssctxt *gssctxt;
192 	gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER;
193 	gss_buffer_desc recv_tok;
194 	OM_uint32 maj_status;
195 	u_int len;
196 
197 	if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep))
198 		fatal("No authentication or GSSAPI context");
199 
200 	gssctxt = authctxt->methoddata;
201 	recv_tok.value = packet_get_string(&len);
202 	recv_tok.length = len;
203 
204 	packet_check_eom();
205 
206 	/* Push the error token into GSSAPI to see what it says */
207 	maj_status = PRIVSEP(ssh_gssapi_accept_ctx(gssctxt, &recv_tok,
208 	    &send_tok, NULL));
209 
210 	free(recv_tok.value);
211 
212 	/* We can't return anything to the client, even if we wanted to */
213 	dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
214 	dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL);
215 
216 	/* The client will have already moved on to the next auth */
217 
218 	gss_release_buffer(&maj_status, &send_tok);
219 }
220 
221 /*
222  * This is called when the client thinks we've completed authentication.
223  * It should only be enabled in the dispatch handler by the function above,
224  * which only enables it once the GSSAPI exchange is complete.
225  */
226 
227 static void
228 input_gssapi_exchange_complete(int type, u_int32_t plen, void *ctxt)
229 {
230 	Authctxt *authctxt = ctxt;
231 	int authenticated;
232 
233 	if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep))
234 		fatal("No authentication or GSSAPI context");
235 
236 	/*
237 	 * We don't need to check the status, because we're only enabled in
238 	 * the dispatcher once the exchange is complete
239 	 */
240 
241 	packet_check_eom();
242 
243 	authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user));
244 
245 	authctxt->postponed = 0;
246 	dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
247 	dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL);
248 	dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_MIC, NULL);
249 	dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL);
250 	userauth_finish(authctxt, authenticated, "gssapi-with-mic", NULL);
251 }
252 
253 static void
254 input_gssapi_mic(int type, u_int32_t plen, void *ctxt)
255 {
256 	Authctxt *authctxt = ctxt;
257 	Gssctxt *gssctxt;
258 	int authenticated = 0;
259 	Buffer b;
260 	gss_buffer_desc mic, gssbuf;
261 	u_int len;
262 
263 	if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep))
264 		fatal("No authentication or GSSAPI context");
265 
266 	gssctxt = authctxt->methoddata;
267 
268 	mic.value = packet_get_string(&len);
269 	mic.length = len;
270 
271 	ssh_gssapi_buildmic(&b, authctxt->user, authctxt->service,
272 	    "gssapi-with-mic");
273 
274 	gssbuf.value = buffer_ptr(&b);
275 	gssbuf.length = buffer_len(&b);
276 
277 	if (!GSS_ERROR(PRIVSEP(ssh_gssapi_checkmic(gssctxt, &gssbuf, &mic))))
278 		authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user));
279 	else
280 		logit("GSSAPI MIC check failed");
281 
282 	buffer_free(&b);
283 	free(mic.value);
284 
285 	authctxt->postponed = 0;
286 	dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
287 	dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL);
288 	dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_MIC, NULL);
289 	dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL);
290 	userauth_finish(authctxt, authenticated, "gssapi-with-mic", NULL);
291 }
292 
293 Authmethod method_gssapi = {
294 	"gssapi-with-mic",
295 	userauth_gssapi,
296 	&options.gss_authentication
297 };
298 
299 #endif /* GSSAPI */
300