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30460aeb | 1 | /* $OpenBSD: auth2-gss.c,v 1.15 2006/08/03 03:34:41 deraadt Exp $ */ |
7cac2b65 | 2 | |
b59afbfe | 3 | /* |
23987cb8 | 4 | * Copyright (c) 2001-2003 Simon Wilkinson. All rights reserved. |
b59afbfe | 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 | |
7cac2b65 | 30 | |
30460aeb | 31 | #include <sys/types.h> |
32 | ||
33 | #include <stdarg.h> | |
34 | ||
35 | #include "xmalloc.h" | |
36 | #include "key.h" | |
37 | #include "hostfile.h" | |
b59afbfe | 38 | #include "auth.h" |
39 | #include "ssh2.h" | |
b59afbfe | 40 | #include "log.h" |
41 | #include "dispatch.h" | |
30460aeb | 42 | #include "buffer.h" |
b59afbfe | 43 | #include "servconf.h" |
b59afbfe | 44 | #include "packet.h" |
b59afbfe | 45 | #include "ssh-gss.h" |
30460aeb | 46 | #include "monitor_wrap.h" |
b59afbfe | 47 | |
48 | extern ServerOptions options; | |
b59afbfe | 49 | |
23987cb8 | 50 | static void ssh_gssapi_userauth_error(Gssctxt *ctxt); |
b59afbfe | 51 | static void input_gssapi_token(int type, u_int32_t plen, void *ctxt); |
540d72c3 | 52 | static void input_gssapi_mic(int type, u_int32_t plen, void *ctxt); |
b59afbfe | 53 | static void input_gssapi_exchange_complete(int type, u_int32_t plen, void *ctxt); |
e23e524c | 54 | static void input_gssapi_errtok(int, u_int32_t, void *); |
b59afbfe | 55 | |
540d72c3 | 56 | static int gssapi_with_mic = 1; /* flag to toggle "gssapi-with-mic" vs. |
57 | "gssapi" */ | |
58 | ||
5217e987 | 59 | static int |
60 | userauth_external(Authctxt *authctxt) | |
61 | { | |
62 | packet_check_eom(); | |
63 | ||
7a8e5702 | 64 | if (authctxt->valid && authctxt->user && authctxt->user[0]) { |
294206af | 65 | return(PRIVSEP(ssh_gssapi_userok(authctxt->user))); |
5217e987 | 66 | } |
67 | return 0; | |
68 | } | |
69 | ||
fe4ad273 | 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 | ||
7cac2b65 | 116 | /* |
117 | * We only support those mechanisms that we know about (ie ones that we know | |
08822d99 | 118 | * how to check local user kuserok and the like) |
b59afbfe | 119 | */ |
120 | static int | |
121 | userauth_gssapi(Authctxt *authctxt) | |
122 | { | |
7e82606e | 123 | gss_OID_desc goid = {0, NULL}; |
7cac2b65 | 124 | Gssctxt *ctxt = NULL; |
125 | int mechs; | |
126 | gss_OID_set supported; | |
127 | int present; | |
128 | OM_uint32 ms; | |
129 | u_int len; | |
2ce0bfe4 | 130 | u_char *doid = NULL; |
7cac2b65 | 131 | |
941f3f29 | 132 | /* authctxt->valid may be 0 if we haven't yet determined |
133 | username from gssapi context. */ | |
134 | ||
5217e987 | 135 | if (authctxt->user == NULL) |
7cac2b65 | 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 | ||
540d72c3 | 151 | present = 0; |
7cac2b65 | 152 | doid = packet_get_string(&len); |
153 | ||
2ce0bfe4 | 154 | if (len > 2 && doid[0] == SSH_GSS_OIDTYPE && |
155 | doid[1] == len - 2) { | |
7e82606e | 156 | goid.elements = doid + 2; |
157 | goid.length = len - 2; | |
6fc2ad02 | 158 | gss_test_oid_set_member(&ms, &goid, supported, |
159 | &present); | |
160 | } else { | |
161 | logit("Badly formed OID received"); | |
7cac2b65 | 162 | } |
7cac2b65 | 163 | } while (mechs > 0 && !present); |
164 | ||
165 | gss_release_oid_set(&ms, &supported); | |
166 | ||
167 | if (!present) { | |
168 | xfree(doid); | |
fe4ad273 | 169 | authctxt->server_caused_failure = 1; |
7cac2b65 | 170 | return (0); |
171 | } | |
172 | ||
7e82606e | 173 | if (GSS_ERROR(PRIVSEP(ssh_gssapi_server_ctx(&ctxt, &goid)))) { |
30460aeb | 174 | if (ctxt != NULL) |
175 | ssh_gssapi_delete_ctx(&ctxt); | |
7cac2b65 | 176 | xfree(doid); |
fe4ad273 | 177 | authctxt->server_caused_failure = 1; |
7cac2b65 | 178 | return (0); |
23987cb8 | 179 | } |
b59afbfe | 180 | |
08822d99 | 181 | authctxt->methoddata = (void *)ctxt; |
b59afbfe | 182 | |
7cac2b65 | 183 | packet_start(SSH2_MSG_USERAUTH_GSSAPI_RESPONSE); |
23987cb8 | 184 | |
540d72c3 | 185 | /* Return the OID that we received */ |
7cac2b65 | 186 | packet_put_string(doid, len); |
23987cb8 | 187 | |
7cac2b65 | 188 | packet_send(); |
189 | xfree(doid); | |
b59afbfe | 190 | |
7cac2b65 | 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); | |
b59afbfe | 196 | } |
197 | ||
198 | static void | |
199 | input_gssapi_token(int type, u_int32_t plen, void *ctxt) | |
200 | { | |
7cac2b65 | 201 | Authctxt *authctxt = ctxt; |
202 | Gssctxt *gssctxt; | |
203 | gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER; | |
204 | gss_buffer_desc recv_tok; | |
147c00cc | 205 | OM_uint32 maj_status, min_status, flags=0; |
7cac2b65 | 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, | |
540d72c3 | 218 | &send_tok, &flags)); |
7cac2b65 | 219 | |
220 | xfree(recv_tok.value); | |
221 | ||
222 | if (GSS_ERROR(maj_status)) { | |
e23e524c | 223 | ssh_gssapi_userauth_error(gssctxt); |
224 | if (send_tok.length != 0) { | |
e23e524c | 225 | packet_start(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK); |
7cac2b65 | 226 | packet_put_string(send_tok.value, send_tok.length); |
227 | packet_send(); | |
228 | } | |
229 | authctxt->postponed = 0; | |
7cac2b65 | 230 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); |
540d72c3 | 231 | userauth_finish(authctxt, 0, |
232 | gssapi_with_mic ? "gssapi-with-mic" : | |
233 | "gssapi"); | |
7cac2b65 | 234 | } else { |
235 | if (send_tok.length != 0) { | |
7cac2b65 | 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) { | |
7cac2b65 | 241 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); |
540d72c3 | 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); | |
7cac2b65 | 249 | } |
250 | } | |
251 | ||
252 | gss_release_buffer(&min_status, &send_tok); | |
e23e524c | 253 | } |
23987cb8 | 254 | |
e23e524c | 255 | static void |
256 | input_gssapi_errtok(int type, u_int32_t plen, void *ctxt) | |
257 | { | |
7cac2b65 | 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); | |
e23e524c | 279 | |
280 | /* We can't return anything to the client, even if we wanted to */ | |
e23e524c | 281 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); |
7cac2b65 | 282 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL); |
e23e524c | 283 | |
284 | /* The client will have already moved on to the next auth */ | |
7cac2b65 | 285 | |
286 | gss_release_buffer(&maj_status, &send_tok); | |
b59afbfe | 287 | } |
288 | ||
540d72c3 | 289 | static void |
290 | gssapi_set_implicit_username(Authctxt *authctxt) | |
291 | { | |
4f1e213f | 292 | if ((authctxt->user == NULL) || (authctxt->user[0] == '\0')) { |
540d72c3 | 293 | char *lname = NULL; |
294 | PRIVSEP(ssh_gssapi_localname(&lname)); | |
295 | if (lname && lname[0] != '\0') { | |
4f1e213f | 296 | if (authctxt->user) xfree(authctxt->user); |
540d72c3 | 297 | authctxt->user = lname; |
298 | debug("set username to %s from gssapi context", lname); | |
299 | authctxt->pw = PRIVSEP(getpwnamallow(authctxt->user)); | |
5217e987 | 300 | if (authctxt->pw) { |
301 | authctxt->valid = 1; | |
302 | } | |
540d72c3 | 303 | } else { |
304 | debug("failed to set username from gssapi context"); | |
d9e17760 | 305 | packet_send_debug("failed to set username from gssapi context"); |
540d72c3 | 306 | } |
307 | } | |
308 | if (authctxt->pw) { | |
309 | #ifdef USE_PAM | |
147c00cc | 310 | if (options.use_pam) |
5217e987 | 311 | PRIVSEP(start_pam(authctxt)); |
540d72c3 | 312 | #endif |
313 | } | |
314 | } | |
315 | ||
7cac2b65 | 316 | /* |
317 | * This is called when the client thinks we've completed authentication. | |
b59afbfe | 318 | * It should only be enabled in the dispatch handler by the function above, |
319 | * which only enables it once the GSSAPI exchange is complete. | |
320 | */ | |
7cac2b65 | 321 | |
b59afbfe | 322 | static void |
323 | input_gssapi_exchange_complete(int type, u_int32_t plen, void *ctxt) | |
324 | { | |
7cac2b65 | 325 | Authctxt *authctxt = ctxt; |
326 | Gssctxt *gssctxt; | |
327 | int authenticated; | |
328 | ||
b59afbfe | 329 | if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep)) |
7cac2b65 | 330 | fatal("No authentication or GSSAPI context"); |
331 | ||
540d72c3 | 332 | gssapi_set_implicit_username(authctxt); |
d13dfff4 | 333 | |
7cac2b65 | 334 | gssctxt = authctxt->methoddata; |
335 | ||
7cac2b65 | 336 | /* |
540d72c3 | 337 | * We don't need to check the status, because we're only enabled in |
338 | * the dispatcher once the exchange is complete | |
b59afbfe | 339 | */ |
340 | ||
7cac2b65 | 341 | packet_check_eom(); |
342 | ||
941f3f29 | 343 | /* user should be set if valid but we double-check here */ |
344 | if (authctxt->valid && authctxt->user && authctxt->user[0]) { | |
540d72c3 | 345 | authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user)); |
346 | } else { | |
347 | authenticated = 0; | |
348 | } | |
b59afbfe | 349 | |
7cac2b65 | 350 | authctxt->postponed = 0; |
351 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); | |
352 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL); | |
540d72c3 | 353 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_MIC, NULL); |
7cac2b65 | 354 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL); |
540d72c3 | 355 | userauth_finish(authctxt, authenticated, |
356 | gssapi_with_mic ? "gssapi-with-mic" : "gssapi"); | |
357 | } | |
358 | ||
359 | static int | |
360 | userauth_gssapi_with_mic(Authctxt *authctxt) | |
361 | { | |
362 | gssapi_with_mic = 1; | |
363 | return userauth_gssapi(authctxt); | |
364 | } | |
365 | ||
366 | static int | |
367 | userauth_gssapi_without_mic(Authctxt *authctxt) | |
368 | { | |
369 | gssapi_with_mic = 0; | |
370 | return userauth_gssapi(authctxt); | |
371 | } | |
372 | ||
373 | static void | |
374 | input_gssapi_mic(int type, u_int32_t plen, void *ctxt) | |
375 | { | |
376 | Authctxt *authctxt = ctxt; | |
377 | Gssctxt *gssctxt; | |
378 | int authenticated = 0; | |
379 | Buffer b; | |
380 | gss_buffer_desc mic, gssbuf; | |
381 | u_int len; | |
382 | ||
383 | if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep)) | |
384 | fatal("No authentication or GSSAPI context"); | |
385 | ||
386 | gssapi_set_implicit_username(authctxt); | |
387 | ||
388 | gssctxt = authctxt->methoddata; | |
389 | ||
390 | mic.value = packet_get_string(&len); | |
391 | mic.length = len; | |
392 | ||
393 | ssh_gssapi_buildmic(&b, authctxt->user, authctxt->service, | |
394 | "gssapi-with-mic"); | |
395 | ||
396 | gssbuf.value = buffer_ptr(&b); | |
397 | gssbuf.length = buffer_len(&b); | |
398 | ||
399 | if (!GSS_ERROR(PRIVSEP(ssh_gssapi_checkmic(gssctxt, &gssbuf, &mic)))) | |
941f3f29 | 400 | if (authctxt->valid && authctxt->user && authctxt->user[0]) { |
540d72c3 | 401 | authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user)); |
402 | } else { | |
403 | authenticated = 0; | |
404 | } | |
405 | else | |
406 | logit("GSSAPI MIC check failed"); | |
407 | ||
408 | buffer_free(&b); | |
409 | xfree(mic.value); | |
410 | ||
411 | authctxt->postponed = 0; | |
412 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); | |
413 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL); | |
414 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_MIC, NULL); | |
415 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL); | |
416 | userauth_finish(authctxt, authenticated, "gssapi-with-mic"); | |
b59afbfe | 417 | } |
418 | ||
23987cb8 | 419 | static void ssh_gssapi_userauth_error(Gssctxt *ctxt) { |
420 | char *errstr; | |
421 | OM_uint32 maj,min; | |
422 | ||
423 | errstr=PRIVSEP(ssh_gssapi_last_error(ctxt,&maj,&min)); | |
424 | if (errstr) { | |
425 | packet_start(SSH2_MSG_USERAUTH_GSSAPI_ERROR); | |
426 | packet_put_int(maj); | |
427 | packet_put_int(min); | |
428 | packet_put_cstring(errstr); | |
429 | packet_put_cstring(""); | |
430 | packet_send(); | |
431 | packet_write_wait(); | |
432 | xfree(errstr); | |
433 | } | |
434 | } | |
435 | ||
b59afbfe | 436 | Authmethod method_external = { |
437 | "external-keyx", | |
438 | userauth_external, | |
439 | &options.gss_authentication | |
440 | }; | |
441 | ||
fe4ad273 | 442 | Authmethod method_gsskeyex = { |
443 | "gssapi-keyex", | |
444 | userauth_gsskeyex, | |
445 | &options.gss_authentication | |
446 | }; | |
447 | ||
b59afbfe | 448 | Authmethod method_gssapi = { |
540d72c3 | 449 | "gssapi-with-mic", |
450 | userauth_gssapi_with_mic, | |
451 | &options.gss_authentication | |
452 | }; | |
453 | ||
454 | Authmethod method_gssapi_compat = { | |
7cac2b65 | 455 | "gssapi", |
540d72c3 | 456 | userauth_gssapi_without_mic, |
7cac2b65 | 457 | &options.gss_authentication |
b59afbfe | 458 | }; |
459 | ||
460 | #endif /* GSSAPI */ |