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540d72c3 | 1 | /* $OpenBSD: auth2-gss.c,v 1.7 2003/11/21 11:57:03 djm 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 | |
b59afbfe | 31 | #include "auth.h" |
32 | #include "ssh2.h" | |
b59afbfe | 33 | #include "xmalloc.h" |
34 | #include "log.h" | |
35 | #include "dispatch.h" | |
36 | #include "servconf.h" | |
37 | #include "compat.h" | |
38 | #include "packet.h" | |
39 | #include "monitor_wrap.h" | |
40 | ||
41 | #include "ssh-gss.h" | |
42 | ||
43 | extern ServerOptions options; | |
b59afbfe | 44 | |
45 | static int | |
46 | userauth_external(Authctxt *authctxt) | |
47 | { | |
48 | packet_check_eom(); | |
49 | ||
50 | return(PRIVSEP(ssh_gssapi_userok(authctxt->user))); | |
51 | } | |
52 | ||
23987cb8 | 53 | static void ssh_gssapi_userauth_error(Gssctxt *ctxt); |
b59afbfe | 54 | static void input_gssapi_token(int type, u_int32_t plen, void *ctxt); |
540d72c3 | 55 | static void input_gssapi_mic(int type, u_int32_t plen, void *ctxt); |
b59afbfe | 56 | static void input_gssapi_exchange_complete(int type, u_int32_t plen, void *ctxt); |
e23e524c | 57 | static void input_gssapi_errtok(int, u_int32_t, void *); |
b59afbfe | 58 | |
540d72c3 | 59 | static int gssapi_with_mic = 1; /* flag to toggle "gssapi-with-mic" vs. |
60 | "gssapi" */ | |
61 | ||
7cac2b65 | 62 | /* |
63 | * We only support those mechanisms that we know about (ie ones that we know | |
b59afbfe | 64 | * how to check local user kuserok and the like |
65 | */ | |
66 | static int | |
67 | userauth_gssapi(Authctxt *authctxt) | |
68 | { | |
7cac2b65 | 69 | gss_OID_desc oid = {0, NULL}; |
70 | Gssctxt *ctxt = NULL; | |
71 | int mechs; | |
72 | gss_OID_set supported; | |
73 | int present; | |
74 | OM_uint32 ms; | |
75 | u_int len; | |
76 | char *doid = NULL; | |
77 | ||
78 | if (!authctxt->valid || authctxt->user == NULL) | |
79 | return (0); | |
80 | ||
81 | mechs = packet_get_int(); | |
82 | if (mechs == 0) { | |
83 | debug("Mechanism negotiation is not supported"); | |
84 | return (0); | |
85 | } | |
86 | ||
87 | ssh_gssapi_supported_oids(&supported); | |
88 | do { | |
89 | mechs--; | |
90 | ||
91 | if (doid) | |
92 | xfree(doid); | |
93 | ||
540d72c3 | 94 | present = 0; |
7cac2b65 | 95 | doid = packet_get_string(&len); |
96 | ||
97 | if (doid[0] != SSH_GSS_OIDTYPE || doid[1] != len-2) { | |
98 | logit("Mechanism OID received using the old encoding form"); | |
99 | oid.elements = doid; | |
100 | oid.length = len; | |
101 | } else { | |
102 | oid.elements = doid + 2; | |
103 | oid.length = len - 2; | |
104 | } | |
105 | gss_test_oid_set_member(&ms, &oid, supported, &present); | |
106 | } while (mechs > 0 && !present); | |
107 | ||
108 | gss_release_oid_set(&ms, &supported); | |
109 | ||
110 | if (!present) { | |
111 | xfree(doid); | |
112 | return (0); | |
113 | } | |
114 | ||
115 | if (GSS_ERROR(PRIVSEP(ssh_gssapi_server_ctx(&ctxt, &oid)))) { | |
116 | xfree(doid); | |
117 | return (0); | |
23987cb8 | 118 | } |
b59afbfe | 119 | |
7cac2b65 | 120 | authctxt->methoddata=(void *)ctxt; |
b59afbfe | 121 | |
7cac2b65 | 122 | packet_start(SSH2_MSG_USERAUTH_GSSAPI_RESPONSE); |
23987cb8 | 123 | |
540d72c3 | 124 | /* Return the OID that we received */ |
7cac2b65 | 125 | packet_put_string(doid, len); |
23987cb8 | 126 | |
7cac2b65 | 127 | packet_send(); |
128 | xfree(doid); | |
b59afbfe | 129 | |
7cac2b65 | 130 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, &input_gssapi_token); |
131 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, &input_gssapi_errtok); | |
132 | authctxt->postponed = 1; | |
133 | ||
134 | return (0); | |
b59afbfe | 135 | } |
136 | ||
137 | static void | |
138 | input_gssapi_token(int type, u_int32_t plen, void *ctxt) | |
139 | { | |
7cac2b65 | 140 | Authctxt *authctxt = ctxt; |
141 | Gssctxt *gssctxt; | |
142 | gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER; | |
143 | gss_buffer_desc recv_tok; | |
147c00cc | 144 | OM_uint32 maj_status, min_status, flags=0; |
7cac2b65 | 145 | u_int len; |
146 | ||
147 | if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep)) | |
148 | fatal("No authentication or GSSAPI context"); | |
149 | ||
150 | gssctxt = authctxt->methoddata; | |
151 | recv_tok.value = packet_get_string(&len); | |
152 | recv_tok.length = len; /* u_int vs. size_t */ | |
153 | ||
154 | packet_check_eom(); | |
155 | ||
156 | maj_status = PRIVSEP(ssh_gssapi_accept_ctx(gssctxt, &recv_tok, | |
540d72c3 | 157 | &send_tok, &flags)); |
7cac2b65 | 158 | |
159 | xfree(recv_tok.value); | |
160 | ||
161 | if (GSS_ERROR(maj_status)) { | |
e23e524c | 162 | ssh_gssapi_userauth_error(gssctxt); |
163 | if (send_tok.length != 0) { | |
e23e524c | 164 | packet_start(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK); |
7cac2b65 | 165 | packet_put_string(send_tok.value, send_tok.length); |
166 | packet_send(); | |
167 | } | |
168 | authctxt->postponed = 0; | |
7cac2b65 | 169 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); |
540d72c3 | 170 | userauth_finish(authctxt, 0, |
171 | gssapi_with_mic ? "gssapi-with-mic" : | |
172 | "gssapi"); | |
7cac2b65 | 173 | } else { |
174 | if (send_tok.length != 0) { | |
7cac2b65 | 175 | packet_start(SSH2_MSG_USERAUTH_GSSAPI_TOKEN); |
176 | packet_put_string(send_tok.value, send_tok.length); | |
177 | packet_send(); | |
178 | } | |
179 | if (maj_status == GSS_S_COMPLETE) { | |
7cac2b65 | 180 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); |
540d72c3 | 181 | if (flags & GSS_C_INTEG_FLAG && gssapi_with_mic) |
182 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_MIC, | |
183 | &input_gssapi_mic); | |
184 | else | |
185 | dispatch_set( | |
186 | SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, | |
187 | &input_gssapi_exchange_complete); | |
7cac2b65 | 188 | } |
189 | } | |
190 | ||
191 | gss_release_buffer(&min_status, &send_tok); | |
e23e524c | 192 | } |
23987cb8 | 193 | |
e23e524c | 194 | static void |
195 | input_gssapi_errtok(int type, u_int32_t plen, void *ctxt) | |
196 | { | |
7cac2b65 | 197 | Authctxt *authctxt = ctxt; |
198 | Gssctxt *gssctxt; | |
199 | gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER; | |
200 | gss_buffer_desc recv_tok; | |
201 | OM_uint32 maj_status; | |
202 | u_int len; | |
203 | ||
204 | if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep)) | |
205 | fatal("No authentication or GSSAPI context"); | |
206 | ||
207 | gssctxt = authctxt->methoddata; | |
208 | recv_tok.value = packet_get_string(&len); | |
209 | recv_tok.length = len; | |
210 | ||
211 | packet_check_eom(); | |
212 | ||
213 | /* Push the error token into GSSAPI to see what it says */ | |
214 | maj_status = PRIVSEP(ssh_gssapi_accept_ctx(gssctxt, &recv_tok, | |
215 | &send_tok, NULL)); | |
216 | ||
217 | xfree(recv_tok.value); | |
e23e524c | 218 | |
219 | /* We can't return anything to the client, even if we wanted to */ | |
e23e524c | 220 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); |
7cac2b65 | 221 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL); |
e23e524c | 222 | |
223 | /* The client will have already moved on to the next auth */ | |
7cac2b65 | 224 | |
225 | gss_release_buffer(&maj_status, &send_tok); | |
b59afbfe | 226 | } |
227 | ||
540d72c3 | 228 | static void |
229 | gssapi_set_implicit_username(Authctxt *authctxt) | |
230 | { | |
231 | if ((strcmp(authctxt->user, "") == 0) && (authctxt->pw == NULL)) { | |
232 | char *lname = NULL; | |
233 | PRIVSEP(ssh_gssapi_localname(&lname)); | |
234 | if (lname && lname[0] != '\0') { | |
235 | xfree(authctxt->user); | |
236 | authctxt->user = lname; | |
237 | debug("set username to %s from gssapi context", lname); | |
238 | authctxt->pw = PRIVSEP(getpwnamallow(authctxt->user)); | |
239 | } else { | |
240 | debug("failed to set username from gssapi context"); | |
241 | } | |
242 | } | |
243 | if (authctxt->pw) { | |
244 | #ifdef USE_PAM | |
147c00cc | 245 | if (options.use_pam) |
246 | PRIVSEP(start_pam(authctxt->pw->pw_name)); | |
540d72c3 | 247 | #endif |
248 | } | |
249 | } | |
250 | ||
7cac2b65 | 251 | /* |
252 | * This is called when the client thinks we've completed authentication. | |
b59afbfe | 253 | * It should only be enabled in the dispatch handler by the function above, |
254 | * which only enables it once the GSSAPI exchange is complete. | |
255 | */ | |
7cac2b65 | 256 | |
b59afbfe | 257 | static void |
258 | input_gssapi_exchange_complete(int type, u_int32_t plen, void *ctxt) | |
259 | { | |
7cac2b65 | 260 | Authctxt *authctxt = ctxt; |
261 | Gssctxt *gssctxt; | |
262 | int authenticated; | |
263 | ||
b59afbfe | 264 | if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep)) |
7cac2b65 | 265 | fatal("No authentication or GSSAPI context"); |
266 | ||
540d72c3 | 267 | gssapi_set_implicit_username(authctxt); |
d13dfff4 | 268 | |
7cac2b65 | 269 | gssctxt = authctxt->methoddata; |
270 | ||
7cac2b65 | 271 | /* |
540d72c3 | 272 | * We don't need to check the status, because we're only enabled in |
273 | * the dispatcher once the exchange is complete | |
b59afbfe | 274 | */ |
275 | ||
7cac2b65 | 276 | packet_check_eom(); |
277 | ||
540d72c3 | 278 | if (strcmp(authctxt->user, "") != 0) { |
279 | authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user)); | |
280 | } else { | |
281 | authenticated = 0; | |
282 | } | |
b59afbfe | 283 | |
7cac2b65 | 284 | authctxt->postponed = 0; |
285 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); | |
286 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL); | |
540d72c3 | 287 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_MIC, NULL); |
7cac2b65 | 288 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL); |
540d72c3 | 289 | userauth_finish(authctxt, authenticated, |
290 | gssapi_with_mic ? "gssapi-with-mic" : "gssapi"); | |
291 | } | |
292 | ||
293 | static int | |
294 | userauth_gssapi_with_mic(Authctxt *authctxt) | |
295 | { | |
296 | gssapi_with_mic = 1; | |
297 | return userauth_gssapi(authctxt); | |
298 | } | |
299 | ||
300 | static int | |
301 | userauth_gssapi_without_mic(Authctxt *authctxt) | |
302 | { | |
303 | gssapi_with_mic = 0; | |
304 | return userauth_gssapi(authctxt); | |
305 | } | |
306 | ||
307 | static void | |
308 | input_gssapi_mic(int type, u_int32_t plen, void *ctxt) | |
309 | { | |
310 | Authctxt *authctxt = ctxt; | |
311 | Gssctxt *gssctxt; | |
312 | int authenticated = 0; | |
313 | Buffer b; | |
314 | gss_buffer_desc mic, gssbuf; | |
315 | u_int len; | |
316 | ||
317 | if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep)) | |
318 | fatal("No authentication or GSSAPI context"); | |
319 | ||
320 | gssapi_set_implicit_username(authctxt); | |
321 | ||
322 | gssctxt = authctxt->methoddata; | |
323 | ||
324 | mic.value = packet_get_string(&len); | |
325 | mic.length = len; | |
326 | ||
327 | ssh_gssapi_buildmic(&b, authctxt->user, authctxt->service, | |
328 | "gssapi-with-mic"); | |
329 | ||
330 | gssbuf.value = buffer_ptr(&b); | |
331 | gssbuf.length = buffer_len(&b); | |
332 | ||
333 | if (!GSS_ERROR(PRIVSEP(ssh_gssapi_checkmic(gssctxt, &gssbuf, &mic)))) | |
334 | if (strcmp(authctxt->user, "") != 0) { | |
335 | authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user)); | |
336 | } else { | |
337 | authenticated = 0; | |
338 | } | |
339 | else | |
340 | logit("GSSAPI MIC check failed"); | |
341 | ||
342 | buffer_free(&b); | |
343 | xfree(mic.value); | |
344 | ||
345 | authctxt->postponed = 0; | |
346 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); | |
347 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL); | |
348 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_MIC, NULL); | |
349 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL); | |
350 | userauth_finish(authctxt, authenticated, "gssapi-with-mic"); | |
b59afbfe | 351 | } |
352 | ||
23987cb8 | 353 | static void ssh_gssapi_userauth_error(Gssctxt *ctxt) { |
354 | char *errstr; | |
355 | OM_uint32 maj,min; | |
356 | ||
357 | errstr=PRIVSEP(ssh_gssapi_last_error(ctxt,&maj,&min)); | |
358 | if (errstr) { | |
359 | packet_start(SSH2_MSG_USERAUTH_GSSAPI_ERROR); | |
360 | packet_put_int(maj); | |
361 | packet_put_int(min); | |
362 | packet_put_cstring(errstr); | |
363 | packet_put_cstring(""); | |
364 | packet_send(); | |
365 | packet_write_wait(); | |
366 | xfree(errstr); | |
367 | } | |
368 | } | |
369 | ||
b59afbfe | 370 | Authmethod method_external = { |
371 | "external-keyx", | |
372 | userauth_external, | |
373 | &options.gss_authentication | |
374 | }; | |
375 | ||
376 | Authmethod method_gssapi = { | |
540d72c3 | 377 | "gssapi-with-mic", |
378 | userauth_gssapi_with_mic, | |
379 | &options.gss_authentication | |
380 | }; | |
381 | ||
382 | Authmethod method_gssapi_compat = { | |
7cac2b65 | 383 | "gssapi", |
540d72c3 | 384 | userauth_gssapi_without_mic, |
7cac2b65 | 385 | &options.gss_authentication |
b59afbfe | 386 | }; |
387 | ||
388 | #endif /* GSSAPI */ |