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
49 extern ServerOptions options;
50
51 static int input_gssapi_token(int type, u_int32_t plen, void *ctxt);
52 static int input_gssapi_mic(int type, u_int32_t plen, void *ctxt);
53 static int input_gssapi_exchange_complete(int type, u_int32_t plen, void *ctxt);
54 static 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 */
60 static int
userauth_gssapi(Authctxt * authctxt)61 userauth_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
129 static int
input_gssapi_token(int type,u_int32_t plen,void * ctxt)130 input_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
184 static int
input_gssapi_errtok(int type,u_int32_t plen,void * ctxt)185 input_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
225 static int
input_gssapi_exchange_complete(int type,u_int32_t plen,void * ctxt)226 input_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
252 static int
input_gssapi_mic(int type,u_int32_t plen,void * ctxt)253 input_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
293 Authmethod method_gssapi = {
294 "gssapi-with-mic",
295 userauth_gssapi,
296 &options.gss_authentication
297 };
298
299 #endif /* GSSAPI */
300