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1 | /* $OpenBSD: gss-serv.c,v 1.20 2006/08/03 03:34:42 deraadt Exp $ */ | |
2 | ||
3 | /* | |
4 | * Copyright (c) 2001-2006 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 | #include <string.h> | |
35 | #include <unistd.h> | |
36 | ||
37 | #include "xmalloc.h" | |
38 | #include "buffer.h" | |
39 | #include "key.h" | |
40 | #include "hostfile.h" | |
41 | #include "auth.h" | |
42 | #include "log.h" | |
43 | #include "channels.h" | |
44 | #include "session.h" | |
45 | #include "misc.h" | |
46 | #include "servconf.h" | |
47 | ||
48 | #include "xmalloc.h" | |
49 | #include "ssh-gss.h" | |
50 | #include "monitor_wrap.h" | |
51 | ||
52 | extern ServerOptions options; | |
53 | extern Authctxt *the_authctxt; | |
54 | ||
55 | static ssh_gssapi_client gssapi_client = | |
56 | { GSS_C_EMPTY_BUFFER, GSS_C_EMPTY_BUFFER, | |
57 | GSS_C_NO_CREDENTIAL, NULL, {NULL, NULL, NULL}}; | |
58 | ||
59 | ssh_gssapi_mech gssapi_null_mech = | |
60 | { NULL, NULL, {0, NULL}, NULL, NULL, NULL, NULL}; | |
61 | ||
62 | #ifdef KRB5 | |
63 | extern ssh_gssapi_mech gssapi_kerberos_mech; | |
64 | #endif | |
65 | #ifdef GSI | |
66 | extern ssh_gssapi_mech gssapi_gsi_mech; | |
67 | #endif | |
68 | ||
69 | ssh_gssapi_mech* supported_mechs[]= { | |
70 | #ifdef KRB5 | |
71 | &gssapi_kerberos_mech, | |
72 | #endif | |
73 | #ifdef GSI | |
74 | &gssapi_gsi_mech, | |
75 | #endif | |
76 | &gssapi_null_mech, | |
77 | }; | |
78 | ||
79 | #ifdef GSS_C_GLOBUS_LIMITED_PROXY_FLAG | |
80 | static int limited = 0; | |
81 | #endif | |
82 | ||
83 | /* Unprivileged */ | |
84 | char * | |
85 | ssh_gssapi_server_mechanisms() { | |
86 | gss_OID_set supported; | |
87 | ||
88 | ssh_gssapi_supported_oids(&supported); | |
89 | return (ssh_gssapi_kex_mechs(supported, &ssh_gssapi_server_check_mech, | |
90 | NULL)); | |
91 | } | |
92 | ||
93 | /* Unprivileged */ | |
94 | int | |
95 | ssh_gssapi_server_check_mech(Gssctxt **dum, gss_OID oid, const char *data) { | |
96 | Gssctxt *ctx = NULL; | |
97 | int res; | |
98 | ||
99 | res = !GSS_ERROR(PRIVSEP(ssh_gssapi_server_ctx(&ctx, oid))); | |
100 | ssh_gssapi_delete_ctx(&ctx); | |
101 | ||
102 | return (res); | |
103 | } | |
104 | ||
105 | /* Unprivileged */ | |
106 | void | |
107 | ssh_gssapi_supported_oids(gss_OID_set *oidset) | |
108 | { | |
109 | int i = 0; | |
110 | OM_uint32 min_status; | |
111 | int present; | |
112 | gss_OID_set supported; | |
113 | ||
114 | gss_create_empty_oid_set(&min_status, oidset); | |
115 | /* Ask priviledged process what mechanisms it supports. */ | |
116 | PRIVSEP(gss_indicate_mechs(&min_status, &supported)); | |
117 | ||
118 | while (supported_mechs[i]->name != NULL) { | |
119 | if (GSS_ERROR(gss_test_oid_set_member(&min_status, | |
120 | &supported_mechs[i]->oid, supported, &present))) | |
121 | present = 0; | |
122 | if (present) | |
123 | gss_add_oid_set_member(&min_status, | |
124 | &supported_mechs[i]->oid, oidset); | |
125 | i++; | |
126 | } | |
127 | ||
128 | gss_release_oid_set(&min_status, &supported); | |
129 | } | |
130 | ||
131 | OM_uint32 | |
132 | ssh_gssapi_server_ctx(Gssctxt **ctx, gss_OID oid) | |
133 | { | |
134 | if (*ctx) | |
135 | ssh_gssapi_delete_ctx(ctx); | |
136 | ssh_gssapi_build_ctx(ctx); | |
137 | ssh_gssapi_set_oid(*ctx, oid); | |
138 | return (ssh_gssapi_acquire_cred(*ctx)); | |
139 | } | |
140 | ||
141 | /* Acquire credentials for a server running on the current host. | |
142 | * Requires that the context structure contains a valid OID | |
143 | */ | |
144 | ||
145 | /* Returns a GSSAPI error code */ | |
146 | OM_uint32 | |
147 | ssh_gssapi_acquire_cred(Gssctxt *ctx) | |
148 | { | |
149 | OM_uint32 status; | |
150 | char lname[MAXHOSTNAMELEN]; | |
151 | gss_OID_set oidset; | |
152 | ||
153 | if (options.gss_strict_acceptor) { | |
154 | gss_create_empty_oid_set(&status, &oidset); | |
155 | gss_add_oid_set_member(&status, ctx->oid, &oidset); | |
156 | ||
157 | if (gethostname(lname, MAXHOSTNAMELEN)) { | |
158 | gss_release_oid_set(&status, &oidset); | |
159 | return (-1); | |
160 | } | |
161 | ||
162 | if (GSS_ERROR(ssh_gssapi_import_name(ctx, lname))) { | |
163 | gss_release_oid_set(&status, &oidset); | |
164 | return (ctx->major); | |
165 | } | |
166 | ||
167 | if ((ctx->major = gss_acquire_cred(&ctx->minor, | |
168 | ctx->name, 0, oidset, GSS_C_ACCEPT, &ctx->creds, | |
169 | NULL, NULL))) | |
170 | ssh_gssapi_error(ctx); | |
171 | ||
172 | gss_release_oid_set(&status, &oidset); | |
173 | return (ctx->major); | |
174 | } else { | |
175 | ctx->name = GSS_C_NO_NAME; | |
176 | ctx->creds = GSS_C_NO_CREDENTIAL; | |
177 | } | |
178 | return GSS_S_COMPLETE; | |
179 | } | |
180 | ||
181 | ||
182 | /* Wrapper around accept_sec_context | |
183 | * Requires that the context contains: | |
184 | * oid | |
185 | * credentials (from ssh_gssapi_acquire_cred) | |
186 | */ | |
187 | /* Privileged */ | |
188 | OM_uint32 | |
189 | ssh_gssapi_accept_ctx(Gssctxt *ctx, gss_buffer_desc *recv_tok, | |
190 | gss_buffer_desc *send_tok, OM_uint32 *flags) | |
191 | { | |
192 | OM_uint32 status; | |
193 | gss_OID mech; | |
194 | ||
195 | ctx->major = gss_accept_sec_context(&ctx->minor, | |
196 | &ctx->context, ctx->creds, recv_tok, | |
197 | GSS_C_NO_CHANNEL_BINDINGS, &ctx->client, &mech, | |
198 | send_tok, flags, NULL, &ctx->client_creds); | |
199 | ||
200 | if (GSS_ERROR(ctx->major)) | |
201 | ssh_gssapi_error(ctx); | |
202 | ||
203 | if (ctx->client_creds) | |
204 | debug("Received some client credentials"); | |
205 | else | |
206 | debug("Got no client credentials"); | |
207 | ||
208 | status = ctx->major; | |
209 | ||
210 | /* Now, if we're complete and we have the right flags, then | |
211 | * we flag the user as also having been authenticated | |
212 | */ | |
213 | ||
214 | if (((flags == NULL) || ((*flags & GSS_C_MUTUAL_FLAG) && | |
215 | (*flags & GSS_C_INTEG_FLAG))) && (ctx->major == GSS_S_COMPLETE)) { | |
216 | if (ssh_gssapi_getclient(ctx, &gssapi_client)) | |
217 | fatal("Couldn't convert client name"); | |
218 | #ifdef GSS_C_GLOBUS_LIMITED_PROXY_FLAG | |
219 | if (flags && (*flags & GSS_C_GLOBUS_LIMITED_PROXY_FLAG)) | |
220 | limited=1; | |
221 | #endif | |
222 | } | |
223 | ||
224 | return (status); | |
225 | } | |
226 | ||
227 | /* | |
228 | * This parses an exported name, extracting the mechanism specific portion | |
229 | * to use for ACL checking. It verifies that the name belongs the mechanism | |
230 | * originally selected. | |
231 | */ | |
232 | static OM_uint32 | |
233 | ssh_gssapi_parse_ename(Gssctxt *ctx, gss_buffer_t ename, gss_buffer_t name) | |
234 | { | |
235 | u_char *tok; | |
236 | OM_uint32 offset; | |
237 | OM_uint32 oidl; | |
238 | ||
239 | tok = ename->value; | |
240 | ||
241 | #ifdef GSI /* GSI gss_export_name() is broken. */ | |
242 | if ((ctx->oid->length == gssapi_gsi_mech.oid.length) && | |
243 | (memcmp(ctx->oid->elements, gssapi_gsi_mech.oid.elements, | |
244 | gssapi_gsi_mech.oid.length) == 0)) { | |
245 | name->length = ename->length; | |
246 | name->value = xmalloc(ename->length+1); | |
247 | memcpy(name->value, ename->value, ename->length); | |
248 | return GSS_S_COMPLETE; | |
249 | } | |
250 | #endif | |
251 | ||
252 | /* | |
253 | * Check that ename is long enough for all of the fixed length | |
254 | * header, and that the initial ID bytes are correct | |
255 | */ | |
256 | ||
257 | if (ename->length < 6 || memcmp(tok, "\x04\x01", 2) != 0) | |
258 | return GSS_S_FAILURE; | |
259 | ||
260 | /* | |
261 | * Extract the OID, and check it. Here GSSAPI breaks with tradition | |
262 | * and does use the OID type and length bytes. To confuse things | |
263 | * there are two lengths - the first including these, and the | |
264 | * second without. | |
265 | */ | |
266 | ||
267 | oidl = get_u16(tok+2); /* length including next two bytes */ | |
268 | oidl = oidl-2; /* turn it into the _real_ length of the variable OID */ | |
269 | ||
270 | /* | |
271 | * Check the BER encoding for correct type and length, that the | |
272 | * string is long enough and that the OID matches that in our context | |
273 | */ | |
274 | if (tok[4] != 0x06 || tok[5] != oidl || | |
275 | ename->length < oidl+6 || | |
276 | !ssh_gssapi_check_oid(ctx, tok+6, oidl)) | |
277 | return GSS_S_FAILURE; | |
278 | ||
279 | offset = oidl+6; | |
280 | ||
281 | if (ename->length < offset+4) | |
282 | return GSS_S_FAILURE; | |
283 | ||
284 | name->length = get_u32(tok+offset); | |
285 | offset += 4; | |
286 | ||
287 | if (ename->length < offset+name->length) | |
288 | return GSS_S_FAILURE; | |
289 | ||
290 | name->value = xmalloc(name->length+1); | |
291 | memcpy(name->value, tok+offset, name->length); | |
292 | ((char *)name->value)[name->length] = 0; | |
293 | ||
294 | return GSS_S_COMPLETE; | |
295 | } | |
296 | ||
297 | /* Extract the client details from a given context. This can only reliably | |
298 | * be called once for a context */ | |
299 | ||
300 | /* Privileged (called from accept_secure_ctx) */ | |
301 | OM_uint32 | |
302 | ssh_gssapi_getclient(Gssctxt *ctx, ssh_gssapi_client *client) | |
303 | { | |
304 | int i = 0; | |
305 | ||
306 | gss_buffer_desc ename; | |
307 | ||
308 | client->mech = NULL; | |
309 | ||
310 | while (supported_mechs[i]->name != NULL) { | |
311 | if (supported_mechs[i]->oid.length == ctx->oid->length && | |
312 | (memcmp(supported_mechs[i]->oid.elements, | |
313 | ctx->oid->elements, ctx->oid->length) == 0)) | |
314 | client->mech = supported_mechs[i]; | |
315 | i++; | |
316 | } | |
317 | ||
318 | if (client->mech == NULL) | |
319 | return GSS_S_FAILURE; | |
320 | ||
321 | if ((ctx->major = gss_display_name(&ctx->minor, ctx->client, | |
322 | &client->displayname, NULL))) { | |
323 | ssh_gssapi_error(ctx); | |
324 | return (ctx->major); | |
325 | } | |
326 | ||
327 | if ((ctx->major = gss_export_name(&ctx->minor, ctx->client, | |
328 | &ename))) { | |
329 | ssh_gssapi_error(ctx); | |
330 | return (ctx->major); | |
331 | } | |
332 | ||
333 | if ((ctx->major = ssh_gssapi_parse_ename(ctx,&ename, | |
334 | &client->exportedname))) { | |
335 | return (ctx->major); | |
336 | } | |
337 | ||
338 | /* We can't copy this structure, so we just move the pointer to it */ | |
339 | client->creds = ctx->client_creds; | |
340 | ctx->client_creds = GSS_C_NO_CREDENTIAL; | |
341 | ||
342 | /* needed for globus_gss_assist_map_and_authorize() */ | |
343 | client->context = ctx->context; | |
344 | ||
345 | return (ctx->major); | |
346 | } | |
347 | ||
348 | /* As user - called on fatal/exit */ | |
349 | void | |
350 | ssh_gssapi_cleanup_creds(void) | |
351 | { | |
352 | if (gssapi_client.store.filename != NULL) { | |
353 | /* Unlink probably isn't sufficient */ | |
354 | debug("removing gssapi cred file\"%s\"", | |
355 | gssapi_client.store.filename); | |
356 | unlink(gssapi_client.store.filename); | |
357 | } | |
358 | } | |
359 | ||
360 | /* As user */ | |
361 | void | |
362 | ssh_gssapi_storecreds(void) | |
363 | { | |
364 | if (gssapi_client.mech && gssapi_client.mech->storecreds) { | |
365 | if (options.gss_creds_path) { | |
366 | gssapi_client.store.filename = | |
367 | expand_authorized_keys(options.gss_creds_path, | |
368 | the_authctxt->pw); | |
369 | } | |
370 | (*gssapi_client.mech->storecreds)(&gssapi_client); | |
371 | } else | |
372 | debug("ssh_gssapi_storecreds: Not a GSSAPI mechanism"); | |
373 | } | |
374 | ||
375 | /* This allows GSSAPI methods to do things to the childs environment based | |
376 | * on the passed authentication process and credentials. | |
377 | */ | |
378 | /* As user */ | |
379 | void | |
380 | ssh_gssapi_do_child(char ***envp, u_int *envsizep) | |
381 | { | |
382 | ||
383 | if (gssapi_client.store.envvar != NULL && | |
384 | gssapi_client.store.envval != NULL) { | |
385 | debug("Setting %s to %s", gssapi_client.store.envvar, | |
386 | gssapi_client.store.envval); | |
387 | child_set_env(envp, envsizep, gssapi_client.store.envvar, | |
388 | gssapi_client.store.envval); | |
389 | } | |
390 | } | |
391 | ||
392 | /* Privileged */ | |
393 | int | |
394 | ssh_gssapi_userok(char *user) | |
395 | { | |
396 | OM_uint32 lmin; | |
397 | ||
398 | if (gssapi_client.exportedname.length == 0 || | |
399 | gssapi_client.exportedname.value == NULL) { | |
400 | debug("No suitable client data"); | |
401 | return 0; | |
402 | } | |
403 | #ifdef GSS_C_GLOBUS_LIMITED_PROXY_FLAG | |
404 | if (limited && options.gsi_allow_limited_proxy != 1) { | |
405 | debug("limited proxy not acceptable for remote login"); | |
406 | return 0; | |
407 | } | |
408 | #endif | |
409 | if (gssapi_client.mech && gssapi_client.mech->userok) | |
410 | if ((*gssapi_client.mech->userok)(&gssapi_client, user)) | |
411 | return 1; | |
412 | else { | |
413 | /* Destroy delegated credentials if userok fails */ | |
414 | gss_release_buffer(&lmin, &gssapi_client.displayname); | |
415 | gss_release_buffer(&lmin, &gssapi_client.exportedname); | |
416 | gss_release_cred(&lmin, &gssapi_client.creds); | |
417 | memset(&gssapi_client, 0, sizeof(ssh_gssapi_client)); | |
418 | return 0; | |
419 | } | |
420 | else | |
421 | debug("ssh_gssapi_userok: Unknown GSSAPI mechanism"); | |
422 | return (0); | |
423 | } | |
424 | ||
425 | /* Priviledged */ | |
426 | int | |
427 | ssh_gssapi_localname(char **user) | |
428 | { | |
429 | *user = NULL; | |
430 | if (gssapi_client.displayname.length==0 || | |
431 | gssapi_client.displayname.value==NULL) { | |
432 | debug("No suitable client data"); | |
433 | return(0);; | |
434 | } | |
435 | if (gssapi_client.mech && gssapi_client.mech->localname) { | |
436 | return((*gssapi_client.mech->localname)(&gssapi_client,user)); | |
437 | } else { | |
438 | debug("Unknown client authentication type"); | |
439 | } | |
440 | return(0); | |
441 | } | |
442 | ||
443 | #endif |