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1 | /* $OpenBSD: gss-genr.c,v 1.6 2005/10/13 22:24:31 stevesk Exp $ */ | |
2 | ||
3 | /* | |
4 | * Copyright (c) 2001-2005 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 "xmalloc.h" | |
32 | #include "bufaux.h" | |
33 | #include "log.h" | |
34 | #include "canohost.h" | |
35 | #include "ssh2.h" | |
36 | #include <openssl/evp.h> | |
37 | ||
38 | #include "ssh-gss.h" | |
39 | ||
40 | extern u_char *session_id2; | |
41 | extern u_int session_id2_len; | |
42 | ||
43 | typedef struct { | |
44 | char *encoded; | |
45 | gss_OID oid; | |
46 | } ssh_gss_kex_mapping; | |
47 | ||
48 | /* | |
49 | * XXX - It would be nice to find a more elegant way of handling the | |
50 | * XXX passing of the key exchange context to the userauth routines | |
51 | */ | |
52 | ||
53 | Gssctxt *gss_kex_context = NULL; | |
54 | ||
55 | static ssh_gss_kex_mapping *gss_enc2oid = NULL; | |
56 | ||
57 | int | |
58 | ssh_gssapi_oid_table_ok() { | |
59 | return (gss_enc2oid != NULL); | |
60 | } | |
61 | ||
62 | /* | |
63 | * Return a list of the gss-group1-sha1 mechanisms supported by this program | |
64 | * | |
65 | * We test mechanisms to ensure that we can use them, to avoid starting | |
66 | * a key exchange with a bad mechanism | |
67 | */ | |
68 | ||
69 | ||
70 | char * | |
71 | ssh_gssapi_client_mechanisms(const char *host) { | |
72 | gss_OID_set gss_supported; | |
73 | OM_uint32 min_status; | |
74 | ||
75 | gss_indicate_mechs(&min_status, &gss_supported); | |
76 | ||
77 | return(ssh_gssapi_kex_mechs(gss_supported, ssh_gssapi_check_mechanism, | |
78 | (void *)host)); | |
79 | } | |
80 | ||
81 | char * | |
82 | ssh_gssapi_kex_mechs(gss_OID_set gss_supported, ssh_gssapi_check_fn *check, | |
83 | void *data) { | |
84 | Buffer buf; | |
85 | size_t i; | |
86 | int oidpos, enclen; | |
87 | char *mechs, *encoded; | |
88 | u_char digest[EVP_MAX_MD_SIZE]; | |
89 | char deroid[2]; | |
90 | const EVP_MD *evp_md = EVP_md5(); | |
91 | EVP_MD_CTX md; | |
92 | ||
93 | if (gss_enc2oid != NULL) { | |
94 | for (i=0;gss_enc2oid[i].encoded!=NULL;i++) | |
95 | xfree(gss_enc2oid[i].encoded); | |
96 | xfree(gss_enc2oid); | |
97 | } | |
98 | ||
99 | gss_enc2oid = xmalloc(sizeof(ssh_gss_kex_mapping)* | |
100 | (gss_supported->count+1)); | |
101 | ||
102 | buffer_init(&buf); | |
103 | ||
104 | oidpos = 0; | |
105 | for (i = 0;i < gss_supported->count;i++) { | |
106 | if (gss_supported->elements[i].length < 128 && | |
107 | (*check)(&(gss_supported->elements[i]), data)) { | |
108 | ||
109 | deroid[0] = SSH_GSS_OIDTYPE; | |
110 | deroid[1] = gss_supported->elements[i].length; | |
111 | ||
112 | EVP_DigestInit(&md, evp_md); | |
113 | EVP_DigestUpdate(&md, deroid, 2); | |
114 | EVP_DigestUpdate(&md, | |
115 | gss_supported->elements[i].elements, | |
116 | gss_supported->elements[i].length); | |
117 | EVP_DigestFinal(&md, digest, NULL); | |
118 | ||
119 | encoded = xmalloc(EVP_MD_size(evp_md)*2); | |
120 | enclen = __b64_ntop(digest, EVP_MD_size(evp_md), | |
121 | encoded, EVP_MD_size(evp_md)*2); | |
122 | ||
123 | if (oidpos != 0) | |
124 | buffer_put_char(&buf, ','); | |
125 | ||
126 | buffer_append(&buf, KEX_GSS_GEX_SHA1_ID, | |
127 | sizeof(KEX_GSS_GEX_SHA1_ID)-1); | |
128 | buffer_append(&buf, encoded, enclen); | |
129 | buffer_put_char(&buf,','); | |
130 | buffer_append(&buf, KEX_GSS_GRP1_SHA1_ID, | |
131 | sizeof(KEX_GSS_GRP1_SHA1_ID)-1); | |
132 | buffer_append(&buf, encoded, enclen); | |
133 | ||
134 | gss_enc2oid[oidpos].oid = &(gss_supported->elements[i]); | |
135 | gss_enc2oid[oidpos].encoded = encoded; | |
136 | oidpos++; | |
137 | } | |
138 | } | |
139 | gss_enc2oid[oidpos].oid = NULL; | |
140 | gss_enc2oid[oidpos].encoded = NULL; | |
141 | ||
142 | buffer_put_char(&buf, '\0'); | |
143 | ||
144 | mechs = xmalloc(buffer_len(&buf)); | |
145 | buffer_get(&buf, mechs, buffer_len(&buf)); | |
146 | buffer_free(&buf); | |
147 | ||
148 | if (strlen(mechs) == 0) { | |
149 | xfree(mechs); | |
150 | mechs = NULL; | |
151 | } | |
152 | ||
153 | return (mechs); | |
154 | } | |
155 | ||
156 | gss_OID | |
157 | ssh_gssapi_id_kex(Gssctxt *ctx, char *name, int *gex) { | |
158 | int i = 0; | |
159 | ||
160 | if (strncmp(name, KEX_GSS_GRP1_SHA1_ID, | |
161 | sizeof(KEX_GSS_GRP1_SHA1_ID)-1) == 0) { | |
162 | name+=sizeof(KEX_GSS_GRP1_SHA1_ID)-1; | |
163 | *gex = 0; | |
164 | } else if (strncmp(name, KEX_GSS_GEX_SHA1_ID, | |
165 | sizeof(KEX_GSS_GEX_SHA1_ID)-1) == 0) { | |
166 | name+=sizeof(KEX_GSS_GEX_SHA1_ID)-1; | |
167 | *gex = 1; | |
168 | } else { | |
169 | return NULL; | |
170 | } | |
171 | ||
172 | while (gss_enc2oid[i].encoded != NULL && | |
173 | strcmp(name, gss_enc2oid[i].encoded) != 0) { | |
174 | i++; | |
175 | } | |
176 | ||
177 | if (gss_enc2oid[i].oid != NULL && ctx != NULL) | |
178 | ssh_gssapi_set_oid(ctx, gss_enc2oid[i].oid); | |
179 | ||
180 | return gss_enc2oid[i].oid; | |
181 | } | |
182 | ||
183 | /* Check that the OID in a data stream matches that in the context */ | |
184 | int | |
185 | ssh_gssapi_check_oid(Gssctxt *ctx, void *data, size_t len) | |
186 | { | |
187 | return (ctx != NULL && ctx->oid != GSS_C_NO_OID && | |
188 | ctx->oid->length == len && | |
189 | memcmp(ctx->oid->elements, data, len) == 0); | |
190 | } | |
191 | ||
192 | /* Set the contexts OID from a data stream */ | |
193 | void | |
194 | ssh_gssapi_set_oid_data(Gssctxt *ctx, void *data, size_t len) | |
195 | { | |
196 | if (ctx->oid != GSS_C_NO_OID) { | |
197 | xfree(ctx->oid->elements); | |
198 | xfree(ctx->oid); | |
199 | } | |
200 | ctx->oid = xmalloc(sizeof(gss_OID_desc)); | |
201 | ctx->oid->length = len; | |
202 | ctx->oid->elements = xmalloc(len); | |
203 | memcpy(ctx->oid->elements, data, len); | |
204 | } | |
205 | ||
206 | /* Set the contexts OID */ | |
207 | void | |
208 | ssh_gssapi_set_oid(Gssctxt *ctx, gss_OID oid) | |
209 | { | |
210 | ssh_gssapi_set_oid_data(ctx, oid->elements, oid->length); | |
211 | } | |
212 | ||
213 | /* All this effort to report an error ... */ | |
214 | void | |
215 | ssh_gssapi_error(Gssctxt *ctxt) | |
216 | { | |
217 | debug("%s", ssh_gssapi_last_error(ctxt, NULL, NULL)); | |
218 | } | |
219 | ||
220 | char * | |
221 | ssh_gssapi_last_error(Gssctxt *ctxt, OM_uint32 *major_status, | |
222 | OM_uint32 *minor_status) | |
223 | { | |
224 | OM_uint32 lmin; | |
225 | gss_buffer_desc msg = GSS_C_EMPTY_BUFFER; | |
226 | OM_uint32 ctx; | |
227 | Buffer b; | |
228 | char *ret; | |
229 | ||
230 | buffer_init(&b); | |
231 | ||
232 | if (major_status != NULL) | |
233 | *major_status = ctxt->major; | |
234 | if (minor_status != NULL) | |
235 | *minor_status = ctxt->minor; | |
236 | ||
237 | ctx = 0; | |
238 | /* The GSSAPI error */ | |
239 | do { | |
240 | gss_display_status(&lmin, ctxt->major, | |
241 | GSS_C_GSS_CODE, ctxt->oid, &ctx, &msg); | |
242 | ||
243 | buffer_append(&b, msg.value, msg.length); | |
244 | buffer_put_char(&b, '\n'); | |
245 | ||
246 | gss_release_buffer(&lmin, &msg); | |
247 | } while (ctx != 0); | |
248 | ||
249 | /* The mechanism specific error */ | |
250 | do { | |
251 | gss_display_status(&lmin, ctxt->minor, | |
252 | GSS_C_MECH_CODE, ctxt->oid, &ctx, &msg); | |
253 | ||
254 | buffer_append(&b, msg.value, msg.length); | |
255 | buffer_put_char(&b, '\n'); | |
256 | ||
257 | gss_release_buffer(&lmin, &msg); | |
258 | } while (ctx != 0); | |
259 | ||
260 | buffer_put_char(&b, '\0'); | |
261 | ret = xmalloc(buffer_len(&b)); | |
262 | buffer_get(&b, ret, buffer_len(&b)); | |
263 | buffer_free(&b); | |
264 | return (ret); | |
265 | } | |
266 | ||
267 | /* | |
268 | * Initialise our GSSAPI context. We use this opaque structure to contain all | |
269 | * of the data which both the client and server need to persist across | |
270 | * {accept,init}_sec_context calls, so that when we do it from the userauth | |
271 | * stuff life is a little easier | |
272 | */ | |
273 | void | |
274 | ssh_gssapi_build_ctx(Gssctxt **ctx) | |
275 | { | |
276 | *ctx = xmalloc(sizeof (Gssctxt)); | |
277 | (*ctx)->major = 0; | |
278 | (*ctx)->minor = 0; | |
279 | (*ctx)->context = GSS_C_NO_CONTEXT; | |
280 | (*ctx)->name = GSS_C_NO_NAME; | |
281 | (*ctx)->oid = GSS_C_NO_OID; | |
282 | (*ctx)->creds = GSS_C_NO_CREDENTIAL; | |
283 | (*ctx)->client = GSS_C_NO_NAME; | |
284 | (*ctx)->client_creds = GSS_C_NO_CREDENTIAL; | |
285 | } | |
286 | ||
287 | /* Delete our context, providing it has been built correctly */ | |
288 | void | |
289 | ssh_gssapi_delete_ctx(Gssctxt **ctx) | |
290 | { | |
291 | #if !defined(MECHGLUE) | |
292 | OM_uint32 ms; | |
293 | #endif | |
294 | ||
295 | if ((*ctx) == NULL) | |
296 | return; | |
297 | #if !defined(MECHGLUE) /* mechglue has some memory management issues */ | |
298 | if ((*ctx)->context != GSS_C_NO_CONTEXT) | |
299 | gss_delete_sec_context(&ms, &(*ctx)->context, GSS_C_NO_BUFFER); | |
300 | if ((*ctx)->name != GSS_C_NO_NAME) | |
301 | gss_release_name(&ms, &(*ctx)->name); | |
302 | if ((*ctx)->oid != GSS_C_NO_OID) { | |
303 | xfree((*ctx)->oid->elements); | |
304 | xfree((*ctx)->oid); | |
305 | (*ctx)->oid = GSS_C_NO_OID; | |
306 | } | |
307 | if ((*ctx)->creds != GSS_C_NO_CREDENTIAL) | |
308 | gss_release_cred(&ms, &(*ctx)->creds); | |
309 | if ((*ctx)->client != GSS_C_NO_NAME) | |
310 | gss_release_name(&ms, &(*ctx)->client); | |
311 | if ((*ctx)->client_creds != GSS_C_NO_CREDENTIAL) | |
312 | gss_release_cred(&ms, &(*ctx)->client_creds); | |
313 | #endif | |
314 | ||
315 | xfree(*ctx); | |
316 | *ctx = NULL; | |
317 | } | |
318 | ||
319 | /* | |
320 | * Wrapper to init_sec_context | |
321 | * Requires that the context contains: | |
322 | * oid | |
323 | * server name (from ssh_gssapi_import_name) | |
324 | */ | |
325 | OM_uint32 | |
326 | ssh_gssapi_init_ctx(Gssctxt *ctx, int deleg_creds, gss_buffer_desc *recv_tok, | |
327 | gss_buffer_desc* send_tok, OM_uint32 *flags) | |
328 | { | |
329 | int deleg_flag = 0; | |
330 | ||
331 | if (deleg_creds) { | |
332 | deleg_flag = GSS_C_DELEG_FLAG; | |
333 | debug("Delegating credentials"); | |
334 | } | |
335 | ||
336 | ctx->major = gss_init_sec_context(&ctx->minor, | |
337 | GSS_C_NO_CREDENTIAL, &ctx->context, ctx->name, ctx->oid, | |
338 | GSS_C_MUTUAL_FLAG | GSS_C_INTEG_FLAG | deleg_flag, | |
339 | 0, NULL, recv_tok, NULL, send_tok, flags, NULL); | |
340 | ||
341 | if (GSS_ERROR(ctx->major)) | |
342 | ssh_gssapi_error(ctx); | |
343 | ||
344 | return (ctx->major); | |
345 | } | |
346 | ||
347 | /* Create a service name for the given host */ | |
348 | OM_uint32 | |
349 | ssh_gssapi_import_name(Gssctxt *ctx, const char *host) | |
350 | { | |
351 | gss_buffer_desc gssbuf; | |
352 | char *xhost; | |
353 | ||
354 | /* Make a copy of the host name, in case it was returned by a | |
355 | * previous call to gethostbyname(). */ | |
356 | xhost = xstrdup(host); | |
357 | ||
358 | /* Make sure we have the FQDN. Some GSSAPI implementations don't do | |
359 | * this for us themselves */ | |
360 | resolve_localhost(&xhost); | |
361 | ||
362 | gssbuf.length = sizeof("host@") + strlen(xhost); | |
363 | gssbuf.value = xmalloc(gssbuf.length); | |
364 | snprintf(gssbuf.value, gssbuf.length, "host@%s", xhost); | |
365 | ||
366 | if ((ctx->major = gss_import_name(&ctx->minor, | |
367 | &gssbuf, GSS_C_NT_HOSTBASED_SERVICE, &ctx->name))) | |
368 | ssh_gssapi_error(ctx); | |
369 | ||
370 | xfree(xhost); | |
371 | xfree(gssbuf.value); | |
372 | return (ctx->major); | |
373 | } | |
374 | ||
375 | /* Acquire credentials for a server running on the current host. | |
376 | * Requires that the context structure contains a valid OID | |
377 | */ | |
378 | ||
379 | /* Returns a GSSAPI error code */ | |
380 | OM_uint32 | |
381 | ssh_gssapi_acquire_cred(Gssctxt *ctx) | |
382 | { | |
383 | OM_uint32 status; | |
384 | char lname[MAXHOSTNAMELEN]; | |
385 | gss_OID_set oidset; | |
386 | ||
387 | gss_create_empty_oid_set(&status, &oidset); | |
388 | gss_add_oid_set_member(&status, ctx->oid, &oidset); | |
389 | ||
390 | if (gethostname(lname, MAXHOSTNAMELEN)) | |
391 | return (-1); | |
392 | ||
393 | if (GSS_ERROR(ssh_gssapi_import_name(ctx, lname))) | |
394 | return (ctx->major); | |
395 | ||
396 | if ((ctx->major = gss_acquire_cred(&ctx->minor, | |
397 | ctx->name, 0, oidset, GSS_C_ACCEPT, &ctx->creds, NULL, NULL))) | |
398 | ssh_gssapi_error(ctx); | |
399 | ||
400 | gss_release_oid_set(&status, &oidset); | |
401 | return (ctx->major); | |
402 | } | |
403 | ||
404 | OM_uint32 | |
405 | ssh_gssapi_sign(Gssctxt *ctx, gss_buffer_t buffer, gss_buffer_t hash) | |
406 | { | |
407 | if (ctx == NULL) | |
408 | return -1; | |
409 | ||
410 | if ((ctx->major = gss_get_mic(&ctx->minor, ctx->context, | |
411 | GSS_C_QOP_DEFAULT, buffer, hash))) | |
412 | ssh_gssapi_error(ctx); | |
413 | ||
414 | return (ctx->major); | |
415 | } | |
416 | ||
417 | /* Priviledged when used by server */ | |
418 | OM_uint32 | |
419 | ssh_gssapi_checkmic(Gssctxt *ctx, gss_buffer_t gssbuf, gss_buffer_t gssmic) | |
420 | { | |
421 | if (ctx == NULL) | |
422 | return -1; | |
423 | ||
424 | ctx->major = gss_verify_mic(&ctx->minor, ctx->context, | |
425 | gssbuf, gssmic, NULL); | |
426 | ||
427 | return (ctx->major); | |
428 | } | |
429 | ||
430 | void | |
431 | ssh_gssapi_buildmic(Buffer *b, const char *user, const char *service, | |
432 | const char *context) | |
433 | { | |
434 | buffer_init(b); | |
435 | buffer_put_string(b, session_id2, session_id2_len); | |
436 | buffer_put_char(b, SSH2_MSG_USERAUTH_REQUEST); | |
437 | buffer_put_cstring(b, user); | |
438 | buffer_put_cstring(b, service); | |
439 | buffer_put_cstring(b, context); | |
440 | } | |
441 | ||
442 | OM_uint32 | |
443 | ssh_gssapi_server_ctx(Gssctxt **ctx, gss_OID oid) | |
444 | { | |
445 | if (*ctx) | |
446 | ssh_gssapi_delete_ctx(ctx); | |
447 | ssh_gssapi_build_ctx(ctx); | |
448 | ssh_gssapi_set_oid(*ctx, oid); | |
449 | return (ssh_gssapi_acquire_cred(*ctx)); | |
450 | } | |
451 | ||
452 | int | |
453 | ssh_gssapi_check_mechanism(gss_OID oid, void *host) { | |
454 | Gssctxt * ctx = NULL; | |
455 | gss_buffer_desc token = GSS_C_EMPTY_BUFFER; | |
456 | OM_uint32 major, minor; | |
457 | ||
458 | ssh_gssapi_build_ctx(&ctx); | |
459 | ssh_gssapi_set_oid(ctx, oid); | |
460 | ssh_gssapi_import_name(ctx, host); | |
461 | major = ssh_gssapi_init_ctx(ctx, 0, GSS_C_NO_BUFFER, &token, NULL); | |
462 | gss_release_buffer(&minor, &token); | |
463 | ssh_gssapi_delete_ctx(&ctx); | |
464 | return (!GSS_ERROR(major)); | |
465 | } | |
466 | ||
467 | #endif /* GSSAPI */ |