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1 | /* $OpenBSD: auth2-gss.c,v 1.16 2007/10/29 00:52:45 dtucker 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 ssh_gssapi_userauth_error(Gssctxt *ctxt); | |
51 | static void input_gssapi_token(int type, u_int32_t plen, void *ctxt); | |
52 | static void input_gssapi_mic(int type, u_int32_t plen, void *ctxt); | |
53 | static void input_gssapi_exchange_complete(int type, u_int32_t plen, void *ctxt); | |
54 | static void input_gssapi_errtok(int, u_int32_t, void *); | |
55 | ||
56 | static int gssapi_with_mic = 1; /* flag to toggle "gssapi-with-mic" vs. | |
57 | "gssapi" */ | |
58 | ||
59 | static int | |
60 | userauth_external(Authctxt *authctxt) | |
61 | { | |
62 | packet_check_eom(); | |
63 | ||
64 | if (authctxt->valid && authctxt->user && authctxt->user[0]) { | |
65 | return(PRIVSEP(ssh_gssapi_userok(authctxt->user))); | |
66 | } | |
67 | return 0; | |
68 | } | |
69 | ||
70 | /* | |
71 | * The 'gssapi_keyex' userauth mechanism. | |
72 | */ | |
73 | static int | |
74 | userauth_gsskeyex(Authctxt *authctxt) | |
75 | { | |
76 | int authenticated = 0; | |
77 | Buffer b, b2; | |
78 | gss_buffer_desc mic, gssbuf, gssbuf2; | |
79 | u_int len; | |
80 | ||
81 | mic.value = packet_get_string(&len); | |
82 | mic.length = len; | |
83 | ||
84 | packet_check_eom(); | |
85 | ||
86 | ssh_gssapi_buildmic(&b, authctxt->user, authctxt->service, | |
87 | "gssapi-keyex"); | |
88 | ||
89 | gssbuf.value = buffer_ptr(&b); | |
90 | gssbuf.length = buffer_len(&b); | |
91 | ||
92 | /* client may have used empty username to determine target | |
93 | name from GSSAPI context */ | |
94 | ssh_gssapi_buildmic(&b2, "", authctxt->service, "gssapi-keyex"); | |
95 | ||
96 | gssbuf2.value = buffer_ptr(&b2); | |
97 | gssbuf2.length = buffer_len(&b2); | |
98 | ||
99 | /* gss_kex_context is NULL with privsep, so we can't check it here */ | |
100 | if (!GSS_ERROR(PRIVSEP(ssh_gssapi_checkmic(gss_kex_context, | |
101 | &gssbuf, &mic))) || | |
102 | !GSS_ERROR(PRIVSEP(ssh_gssapi_checkmic(gss_kex_context, | |
103 | &gssbuf2, &mic)))) { | |
104 | if (authctxt->valid && authctxt->user && authctxt->user[0]) { | |
105 | authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user)); | |
106 | } | |
107 | } | |
108 | ||
109 | buffer_free(&b); | |
110 | buffer_free(&b2); | |
111 | xfree(mic.value); | |
112 | ||
113 | return (authenticated); | |
114 | } | |
115 | ||
116 | /* | |
117 | * We only support those mechanisms that we know about (ie ones that we know | |
118 | * how to check local user kuserok and the like) | |
119 | */ | |
120 | static int | |
121 | userauth_gssapi(Authctxt *authctxt) | |
122 | { | |
123 | gss_OID_desc goid = {0, NULL}; | |
124 | Gssctxt *ctxt = NULL; | |
125 | int mechs; | |
126 | gss_OID_set supported; | |
127 | int present; | |
128 | OM_uint32 ms; | |
129 | u_int len; | |
130 | u_char *doid = NULL; | |
131 | ||
132 | /* authctxt->valid may be 0 if we haven't yet determined | |
133 | username from gssapi context. */ | |
134 | ||
135 | if (authctxt->user == NULL) | |
136 | return (0); | |
137 | ||
138 | mechs = packet_get_int(); | |
139 | if (mechs == 0) { | |
140 | debug("Mechanism negotiation is not supported"); | |
141 | return (0); | |
142 | } | |
143 | ||
144 | ssh_gssapi_supported_oids(&supported); | |
145 | do { | |
146 | mechs--; | |
147 | ||
148 | if (doid) | |
149 | xfree(doid); | |
150 | ||
151 | present = 0; | |
152 | doid = packet_get_string(&len); | |
153 | ||
154 | if (len > 2 && doid[0] == SSH_GSS_OIDTYPE && | |
155 | doid[1] == len - 2) { | |
156 | goid.elements = doid + 2; | |
157 | goid.length = len - 2; | |
158 | gss_test_oid_set_member(&ms, &goid, supported, | |
159 | &present); | |
160 | } else { | |
161 | logit("Badly formed OID received"); | |
162 | } | |
163 | } while (mechs > 0 && !present); | |
164 | ||
165 | gss_release_oid_set(&ms, &supported); | |
166 | ||
167 | if (!present) { | |
168 | xfree(doid); | |
169 | authctxt->server_caused_failure = 1; | |
170 | return (0); | |
171 | } | |
172 | ||
173 | if (GSS_ERROR(PRIVSEP(ssh_gssapi_server_ctx(&ctxt, &goid)))) { | |
174 | if (ctxt != NULL) | |
175 | ssh_gssapi_delete_ctx(&ctxt); | |
176 | xfree(doid); | |
177 | authctxt->server_caused_failure = 1; | |
178 | return (0); | |
179 | } | |
180 | ||
181 | authctxt->methoddata = (void *)ctxt; | |
182 | ||
183 | packet_start(SSH2_MSG_USERAUTH_GSSAPI_RESPONSE); | |
184 | ||
185 | /* Return the OID that we received */ | |
186 | packet_put_string(doid, len); | |
187 | ||
188 | packet_send(); | |
189 | xfree(doid); | |
190 | ||
191 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, &input_gssapi_token); | |
192 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, &input_gssapi_errtok); | |
193 | authctxt->postponed = 1; | |
194 | ||
195 | return (0); | |
196 | } | |
197 | ||
198 | static void | |
199 | input_gssapi_token(int type, u_int32_t plen, void *ctxt) | |
200 | { | |
201 | Authctxt *authctxt = ctxt; | |
202 | Gssctxt *gssctxt; | |
203 | gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER; | |
204 | gss_buffer_desc recv_tok; | |
205 | OM_uint32 maj_status, min_status, flags=0; | |
206 | u_int len; | |
207 | ||
208 | if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep)) | |
209 | fatal("No authentication or GSSAPI context"); | |
210 | ||
211 | gssctxt = authctxt->methoddata; | |
212 | recv_tok.value = packet_get_string(&len); | |
213 | recv_tok.length = len; /* u_int vs. size_t */ | |
214 | ||
215 | packet_check_eom(); | |
216 | ||
217 | maj_status = PRIVSEP(ssh_gssapi_accept_ctx(gssctxt, &recv_tok, | |
218 | &send_tok, &flags)); | |
219 | ||
220 | xfree(recv_tok.value); | |
221 | ||
222 | if (GSS_ERROR(maj_status)) { | |
223 | ssh_gssapi_userauth_error(gssctxt); | |
224 | if (send_tok.length != 0) { | |
225 | packet_start(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK); | |
226 | packet_put_string(send_tok.value, send_tok.length); | |
227 | packet_send(); | |
228 | } | |
229 | authctxt->postponed = 0; | |
230 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); | |
231 | userauth_finish(authctxt, 0, | |
232 | gssapi_with_mic ? "gssapi-with-mic" : | |
233 | "gssapi"); | |
234 | } else { | |
235 | if (send_tok.length != 0) { | |
236 | packet_start(SSH2_MSG_USERAUTH_GSSAPI_TOKEN); | |
237 | packet_put_string(send_tok.value, send_tok.length); | |
238 | packet_send(); | |
239 | } | |
240 | if (maj_status == GSS_S_COMPLETE) { | |
241 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); | |
242 | if (flags & GSS_C_INTEG_FLAG && gssapi_with_mic) | |
243 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_MIC, | |
244 | &input_gssapi_mic); | |
245 | else | |
246 | dispatch_set( | |
247 | SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, | |
248 | &input_gssapi_exchange_complete); | |
249 | } | |
250 | } | |
251 | ||
252 | gss_release_buffer(&min_status, &send_tok); | |
253 | } | |
254 | ||
255 | static void | |
256 | input_gssapi_errtok(int type, u_int32_t plen, void *ctxt) | |
257 | { | |
258 | Authctxt *authctxt = ctxt; | |
259 | Gssctxt *gssctxt; | |
260 | gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER; | |
261 | gss_buffer_desc recv_tok; | |
262 | OM_uint32 maj_status; | |
263 | u_int len; | |
264 | ||
265 | if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep)) | |
266 | fatal("No authentication or GSSAPI context"); | |
267 | ||
268 | gssctxt = authctxt->methoddata; | |
269 | recv_tok.value = packet_get_string(&len); | |
270 | recv_tok.length = len; | |
271 | ||
272 | packet_check_eom(); | |
273 | ||
274 | /* Push the error token into GSSAPI to see what it says */ | |
275 | maj_status = PRIVSEP(ssh_gssapi_accept_ctx(gssctxt, &recv_tok, | |
276 | &send_tok, NULL)); | |
277 | ||
278 | xfree(recv_tok.value); | |
279 | ||
280 | /* We can't return anything to the client, even if we wanted to */ | |
281 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); | |
282 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL); | |
283 | ||
284 | /* The client will have already moved on to the next auth */ | |
285 | ||
286 | gss_release_buffer(&maj_status, &send_tok); | |
287 | } | |
288 | ||
289 | static void | |
290 | gssapi_set_username(Authctxt *authctxt) | |
291 | { | |
292 | char *lname = NULL; | |
293 | ||
294 | if ((authctxt->user == NULL) || (authctxt->user[0] == '\0')) { | |
295 | PRIVSEP(ssh_gssapi_localname(&lname)); | |
296 | if (lname && lname[0] != '\0') { | |
297 | if (authctxt->user) xfree(authctxt->user); | |
298 | authctxt->user = lname; | |
299 | debug("set username to %s from gssapi context", lname); | |
300 | authctxt->pw = PRIVSEP(getpwnamallow(authctxt->user)); | |
301 | if (authctxt->pw) { | |
302 | authctxt->valid = 1; | |
303 | #ifdef USE_PAM | |
304 | if (options.use_pam) | |
305 | PRIVSEP(start_pam(authctxt)); | |
306 | #endif | |
307 | } | |
308 | } else { | |
309 | debug("failed to set username from gssapi context"); | |
310 | packet_send_debug("failed to set username from gssapi context"); | |
311 | } | |
312 | } | |
313 | } | |
314 | ||
315 | /* | |
316 | * This is called when the client thinks we've completed authentication. | |
317 | * It should only be enabled in the dispatch handler by the function above, | |
318 | * which only enables it once the GSSAPI exchange is complete. | |
319 | */ | |
320 | ||
321 | static void | |
322 | input_gssapi_exchange_complete(int type, u_int32_t plen, void *ctxt) | |
323 | { | |
324 | Authctxt *authctxt = ctxt; | |
325 | Gssctxt *gssctxt; | |
326 | int authenticated; | |
327 | ||
328 | if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep)) | |
329 | fatal("No authentication or GSSAPI context"); | |
330 | ||
331 | gssapi_set_username(authctxt); | |
332 | ||
333 | gssctxt = authctxt->methoddata; | |
334 | ||
335 | /* | |
336 | * We don't need to check the status, because we're only enabled in | |
337 | * the dispatcher once the exchange is complete | |
338 | */ | |
339 | ||
340 | packet_check_eom(); | |
341 | ||
342 | /* user should be set if valid but we double-check here */ | |
343 | if (authctxt->valid && authctxt->user && authctxt->user[0]) { | |
344 | authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user)); | |
345 | } else { | |
346 | authenticated = 0; | |
347 | } | |
348 | ||
349 | authctxt->postponed = 0; | |
350 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); | |
351 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL); | |
352 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_MIC, NULL); | |
353 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL); | |
354 | userauth_finish(authctxt, authenticated, | |
355 | gssapi_with_mic ? "gssapi-with-mic" : "gssapi"); | |
356 | } | |
357 | ||
358 | static int | |
359 | userauth_gssapi_with_mic(Authctxt *authctxt) | |
360 | { | |
361 | gssapi_with_mic = 1; | |
362 | return userauth_gssapi(authctxt); | |
363 | } | |
364 | ||
365 | static int | |
366 | userauth_gssapi_without_mic(Authctxt *authctxt) | |
367 | { | |
368 | gssapi_with_mic = 0; | |
369 | return userauth_gssapi(authctxt); | |
370 | } | |
371 | ||
372 | static void | |
373 | input_gssapi_mic(int type, u_int32_t plen, void *ctxt) | |
374 | { | |
375 | Authctxt *authctxt = ctxt; | |
376 | Gssctxt *gssctxt; | |
377 | int authenticated = 0; | |
378 | Buffer b; | |
379 | gss_buffer_desc mic, gssbuf; | |
380 | u_int len; | |
381 | ||
382 | if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep)) | |
383 | fatal("No authentication or GSSAPI context"); | |
384 | ||
385 | gssctxt = authctxt->methoddata; | |
386 | ||
387 | mic.value = packet_get_string(&len); | |
388 | mic.length = len; | |
389 | ||
390 | ssh_gssapi_buildmic(&b, authctxt->user, authctxt->service, | |
391 | "gssapi-with-mic"); | |
392 | ||
393 | gssbuf.value = buffer_ptr(&b); | |
394 | gssbuf.length = buffer_len(&b); | |
395 | ||
396 | gssapi_set_username(authctxt); | |
397 | ||
398 | if (!GSS_ERROR(PRIVSEP(ssh_gssapi_checkmic(gssctxt, &gssbuf, &mic)))) | |
399 | if (authctxt->valid && authctxt->user && authctxt->user[0]) { | |
400 | authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user)); | |
401 | } else { | |
402 | authenticated = 0; | |
403 | } | |
404 | else | |
405 | logit("GSSAPI MIC check failed"); | |
406 | ||
407 | buffer_free(&b); | |
408 | xfree(mic.value); | |
409 | ||
410 | authctxt->postponed = 0; | |
411 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); | |
412 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL); | |
413 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_MIC, NULL); | |
414 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL); | |
415 | userauth_finish(authctxt, authenticated, "gssapi-with-mic"); | |
416 | } | |
417 | ||
418 | static void ssh_gssapi_userauth_error(Gssctxt *ctxt) { | |
419 | char *errstr; | |
420 | OM_uint32 maj,min; | |
421 | ||
422 | errstr=PRIVSEP(ssh_gssapi_last_error(ctxt,&maj,&min)); | |
423 | if (errstr) { | |
424 | packet_start(SSH2_MSG_USERAUTH_GSSAPI_ERROR); | |
425 | packet_put_int(maj); | |
426 | packet_put_int(min); | |
427 | packet_put_cstring(errstr); | |
428 | packet_put_cstring(""); | |
429 | packet_send(); | |
430 | packet_write_wait(); | |
431 | xfree(errstr); | |
432 | } | |
433 | } | |
434 | ||
435 | Authmethod method_external = { | |
436 | "external-keyx", | |
437 | userauth_external, | |
438 | &options.gss_authentication | |
439 | }; | |
440 | ||
441 | Authmethod method_gsskeyex = { | |
442 | "gssapi-keyex", | |
443 | userauth_gsskeyex, | |
444 | &options.gss_authentication | |
445 | }; | |
446 | ||
447 | Authmethod method_gssapi = { | |
448 | "gssapi-with-mic", | |
449 | userauth_gssapi_with_mic, | |
450 | &options.gss_authentication | |
451 | }; | |
452 | ||
453 | Authmethod method_gssapi_compat = { | |
454 | "gssapi", | |
455 | userauth_gssapi_without_mic, | |
456 | &options.gss_authentication | |
457 | }; | |
458 | ||
459 | #endif /* GSSAPI */ |