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djm@openbsd.org8f574952017-06-24 06:34:38 +00001/* $OpenBSD: gss-serv.c,v 1.30 2017/06/24 06:34:38 djm Exp $ */
Darren Tucker0efd1552003-08-26 11:49:55 +10002
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
Damien Millerd7834352006-08-05 12:39:39 +100031#include <sys/types.h>
32
Damien Millerded319c2006-09-01 15:38:36 +100033#include <stdarg.h>
Damien Millere3476ed2006-07-24 14:13:33 +100034#include <string.h>
Damien Millerb8fe89c2006-07-24 14:51:00 +100035#include <unistd.h>
Damien Millere3476ed2006-07-24 14:13:33 +100036
Damien Millerb84886b2008-05-19 15:05:07 +100037#include "openbsd-compat/sys-queue.h"
Damien Millerd7834352006-08-05 12:39:39 +100038#include "xmalloc.h"
39#include "buffer.h"
40#include "key.h"
41#include "hostfile.h"
Darren Tucker0efd1552003-08-26 11:49:55 +100042#include "auth.h"
43#include "log.h"
44#include "channels.h"
45#include "session.h"
Damien Miller3f941882006-03-31 23:13:02 +110046#include "misc.h"
djm@openbsd.orgd7c31da2015-05-22 03:50:02 +000047#include "servconf.h"
Darren Tucker0efd1552003-08-26 11:49:55 +100048
49#include "ssh-gss.h"
50
djm@openbsd.orgd7c31da2015-05-22 03:50:02 +000051extern ServerOptions options;
52
Darren Tucker0efd1552003-08-26 11:49:55 +100053static ssh_gssapi_client gssapi_client =
54 { GSS_C_EMPTY_BUFFER, GSS_C_EMPTY_BUFFER,
Damien Miller63ddc892013-07-20 13:35:45 +100055 GSS_C_NO_CREDENTIAL, NULL, {NULL, NULL, NULL, NULL}};
Darren Tucker0efd1552003-08-26 11:49:55 +100056
57ssh_gssapi_mech gssapi_null_mech =
58 { NULL, NULL, {0, NULL}, NULL, NULL, NULL, NULL};
59
60#ifdef KRB5
61extern ssh_gssapi_mech gssapi_kerberos_mech;
62#endif
63
64ssh_gssapi_mech* supported_mechs[]= {
65#ifdef KRB5
66 &gssapi_kerberos_mech,
67#endif
68 &gssapi_null_mech,
69};
70
Damien Millere6a74ae2014-02-27 10:17:49 +110071/*
72 * ssh_gssapi_supported_oids() can cause sandbox violations, so prepare the
73 * list of supported mechanisms before privsep is set up.
74 */
75static gss_OID_set supported_oids;
76
77void
78ssh_gssapi_prepare_supported_oids(void)
79{
80 ssh_gssapi_supported_oids(&supported_oids);
81}
82
83OM_uint32
84ssh_gssapi_test_oid_supported(OM_uint32 *ms, gss_OID member, int *present)
85{
86 if (supported_oids == NULL)
87 ssh_gssapi_prepare_supported_oids();
88 return gss_test_oid_set_member(ms, member, supported_oids, present);
89}
Darren Tucker8f6d0ed2007-06-12 23:40:39 +100090
91/*
92 * Acquire credentials for a server running on the current host.
93 * Requires that the context structure contains a valid OID
94 */
95
96/* Returns a GSSAPI error code */
97/* Privileged (called from ssh_gssapi_server_ctx) */
98static OM_uint32
99ssh_gssapi_acquire_cred(Gssctxt *ctx)
100{
101 OM_uint32 status;
Damien Millere5c0d522014-07-03 21:24:19 +1000102 char lname[NI_MAXHOST];
Darren Tucker8f6d0ed2007-06-12 23:40:39 +1000103 gss_OID_set oidset;
104
djm@openbsd.orgd7c31da2015-05-22 03:50:02 +0000105 if (options.gss_strict_acceptor) {
106 gss_create_empty_oid_set(&status, &oidset);
107 gss_add_oid_set_member(&status, ctx->oid, &oidset);
Darren Tucker8f6d0ed2007-06-12 23:40:39 +1000108
djm@openbsd.orgd7c31da2015-05-22 03:50:02 +0000109 if (gethostname(lname, MAXHOSTNAMELEN)) {
110 gss_release_oid_set(&status, &oidset);
111 return (-1);
112 }
Darren Tucker8f6d0ed2007-06-12 23:40:39 +1000113
djm@openbsd.orgd7c31da2015-05-22 03:50:02 +0000114 if (GSS_ERROR(ssh_gssapi_import_name(ctx, lname))) {
115 gss_release_oid_set(&status, &oidset);
116 return (ctx->major);
117 }
118
119 if ((ctx->major = gss_acquire_cred(&ctx->minor,
120 ctx->name, 0, oidset, GSS_C_ACCEPT, &ctx->creds,
121 NULL, NULL)))
122 ssh_gssapi_error(ctx);
123
Darren Tucker8f6d0ed2007-06-12 23:40:39 +1000124 gss_release_oid_set(&status, &oidset);
125 return (ctx->major);
djm@openbsd.orgd7c31da2015-05-22 03:50:02 +0000126 } else {
127 ctx->name = GSS_C_NO_NAME;
128 ctx->creds = GSS_C_NO_CREDENTIAL;
Darren Tucker8f6d0ed2007-06-12 23:40:39 +1000129 }
djm@openbsd.orgd7c31da2015-05-22 03:50:02 +0000130 return GSS_S_COMPLETE;
Darren Tucker8f6d0ed2007-06-12 23:40:39 +1000131}
132
133/* Privileged */
134OM_uint32
135ssh_gssapi_server_ctx(Gssctxt **ctx, gss_OID oid)
136{
137 if (*ctx)
138 ssh_gssapi_delete_ctx(ctx);
139 ssh_gssapi_build_ctx(ctx);
140 ssh_gssapi_set_oid(*ctx, oid);
141 return (ssh_gssapi_acquire_cred(*ctx));
142}
143
Damien Miller9fac2632005-11-05 15:03:48 +1100144/* Unprivileged */
Darren Tucker0efd1552003-08-26 11:49:55 +1000145void
146ssh_gssapi_supported_oids(gss_OID_set *oidset)
147{
148 int i = 0;
149 OM_uint32 min_status;
150 int present;
151 gss_OID_set supported;
152
153 gss_create_empty_oid_set(&min_status, oidset);
154 gss_indicate_mechs(&min_status, &supported);
155
156 while (supported_mechs[i]->name != NULL) {
157 if (GSS_ERROR(gss_test_oid_set_member(&min_status,
158 &supported_mechs[i]->oid, supported, &present)))
159 present = 0;
160 if (present)
161 gss_add_oid_set_member(&min_status,
162 &supported_mechs[i]->oid, oidset);
163 i++;
164 }
Damien Miller91a2d972006-03-26 00:05:44 +1100165
166 gss_release_oid_set(&min_status, &supported);
Darren Tucker0efd1552003-08-26 11:49:55 +1000167}
168
169
170/* Wrapper around accept_sec_context
171 * Requires that the context contains:
172 * oid
173 * credentials (from ssh_gssapi_acquire_cred)
174 */
Damien Miller9fac2632005-11-05 15:03:48 +1100175/* Privileged */
Darren Tucker0efd1552003-08-26 11:49:55 +1000176OM_uint32
177ssh_gssapi_accept_ctx(Gssctxt *ctx, gss_buffer_desc *recv_tok,
178 gss_buffer_desc *send_tok, OM_uint32 *flags)
179{
180 OM_uint32 status;
181 gss_OID mech;
182
183 ctx->major = gss_accept_sec_context(&ctx->minor,
184 &ctx->context, ctx->creds, recv_tok,
185 GSS_C_NO_CHANNEL_BINDINGS, &ctx->client, &mech,
186 send_tok, flags, NULL, &ctx->client_creds);
187
188 if (GSS_ERROR(ctx->major))
189 ssh_gssapi_error(ctx);
190
191 if (ctx->client_creds)
192 debug("Received some client credentials");
193 else
194 debug("Got no client credentials");
195
196 status = ctx->major;
197
198 /* Now, if we're complete and we have the right flags, then
199 * we flag the user as also having been authenticated
200 */
201
202 if (((flags == NULL) || ((*flags & GSS_C_MUTUAL_FLAG) &&
203 (*flags & GSS_C_INTEG_FLAG))) && (ctx->major == GSS_S_COMPLETE)) {
204 if (ssh_gssapi_getclient(ctx, &gssapi_client))
205 fatal("Couldn't convert client name");
206 }
207
208 return (status);
209}
210
211/*
212 * This parses an exported name, extracting the mechanism specific portion
213 * to use for ACL checking. It verifies that the name belongs the mechanism
214 * originally selected.
215 */
216static OM_uint32
217ssh_gssapi_parse_ename(Gssctxt *ctx, gss_buffer_t ename, gss_buffer_t name)
218{
Damien Millereccb9de2005-06-17 12:59:34 +1000219 u_char *tok;
Darren Tucker0efd1552003-08-26 11:49:55 +1000220 OM_uint32 offset;
221 OM_uint32 oidl;
Damien Miller134350c2003-09-02 22:56:42 +1000222
Damien Miller6fd6def2005-11-05 15:07:05 +1100223 tok = ename->value;
Damien Miller134350c2003-09-02 22:56:42 +1000224
225 /*
226 * Check that ename is long enough for all of the fixed length
Darren Tucker0efd1552003-08-26 11:49:55 +1000227 * header, and that the initial ID bytes are correct
228 */
229
Damien Miller6fd6def2005-11-05 15:07:05 +1100230 if (ename->length < 6 || memcmp(tok, "\x04\x01", 2) != 0)
Darren Tucker0efd1552003-08-26 11:49:55 +1000231 return GSS_S_FAILURE;
232
233 /*
234 * Extract the OID, and check it. Here GSSAPI breaks with tradition
235 * and does use the OID type and length bytes. To confuse things
236 * there are two lengths - the first including these, and the
237 * second without.
238 */
239
Damien Miller3f941882006-03-31 23:13:02 +1100240 oidl = get_u16(tok+2); /* length including next two bytes */
Darren Tucker0efd1552003-08-26 11:49:55 +1000241 oidl = oidl-2; /* turn it into the _real_ length of the variable OID */
242
243 /*
244 * Check the BER encoding for correct type and length, that the
245 * string is long enough and that the OID matches that in our context
246 */
247 if (tok[4] != 0x06 || tok[5] != oidl ||
Damien Miller134350c2003-09-02 22:56:42 +1000248 ename->length < oidl+6 ||
Damien Miller6fd6def2005-11-05 15:07:05 +1100249 !ssh_gssapi_check_oid(ctx, tok+6, oidl))
Darren Tucker0efd1552003-08-26 11:49:55 +1000250 return GSS_S_FAILURE;
251
252 offset = oidl+6;
Damien Miller134350c2003-09-02 22:56:42 +1000253
Darren Tucker0efd1552003-08-26 11:49:55 +1000254 if (ename->length < offset+4)
255 return GSS_S_FAILURE;
Damien Miller134350c2003-09-02 22:56:42 +1000256
Damien Miller3f941882006-03-31 23:13:02 +1100257 name->length = get_u32(tok+offset);
Darren Tucker0efd1552003-08-26 11:49:55 +1000258 offset += 4;
Damien Miller134350c2003-09-02 22:56:42 +1000259
Damien Milleradb467f2011-08-06 06:16:46 +1000260 if (UINT_MAX - offset < name->length)
261 return GSS_S_FAILURE;
Darren Tucker0efd1552003-08-26 11:49:55 +1000262 if (ename->length < offset+name->length)
Damien Miller134350c2003-09-02 22:56:42 +1000263 return GSS_S_FAILURE;
264
Damien Millera0c4ad22003-09-02 22:56:18 +1000265 name->value = xmalloc(name->length+1);
Damien Miller0b70b542006-03-15 11:20:03 +1100266 memcpy(name->value, tok+offset, name->length);
Damien Millera0c4ad22003-09-02 22:56:18 +1000267 ((char *)name->value)[name->length] = 0;
268
Darren Tucker0efd1552003-08-26 11:49:55 +1000269 return GSS_S_COMPLETE;
Damien Miller134350c2003-09-02 22:56:42 +1000270}
Darren Tucker0efd1552003-08-26 11:49:55 +1000271
272/* Extract the client details from a given context. This can only reliably
273 * be called once for a context */
274
Damien Miller9fac2632005-11-05 15:03:48 +1100275/* Privileged (called from accept_secure_ctx) */
Darren Tucker0efd1552003-08-26 11:49:55 +1000276OM_uint32
277ssh_gssapi_getclient(Gssctxt *ctx, ssh_gssapi_client *client)
278{
279 int i = 0;
280
281 gss_buffer_desc ename;
Damien Miller134350c2003-09-02 22:56:42 +1000282
Darren Tucker0efd1552003-08-26 11:49:55 +1000283 client->mech = NULL;
284
285 while (supported_mechs[i]->name != NULL) {
286 if (supported_mechs[i]->oid.length == ctx->oid->length &&
287 (memcmp(supported_mechs[i]->oid.elements,
288 ctx->oid->elements, ctx->oid->length) == 0))
289 client->mech = supported_mechs[i];
290 i++;
291 }
292
Damien Miller134350c2003-09-02 22:56:42 +1000293 if (client->mech == NULL)
Darren Tucker0efd1552003-08-26 11:49:55 +1000294 return GSS_S_FAILURE;
Damien Miller134350c2003-09-02 22:56:42 +1000295
296 if ((ctx->major = gss_display_name(&ctx->minor, ctx->client,
Darren Tucker0efd1552003-08-26 11:49:55 +1000297 &client->displayname, NULL))) {
Damien Miller134350c2003-09-02 22:56:42 +1000298 ssh_gssapi_error(ctx);
299 return (ctx->major);
Darren Tucker0efd1552003-08-26 11:49:55 +1000300 }
Damien Miller134350c2003-09-02 22:56:42 +1000301
302 if ((ctx->major = gss_export_name(&ctx->minor, ctx->client,
Darren Tucker0efd1552003-08-26 11:49:55 +1000303 &ename))) {
304 ssh_gssapi_error(ctx);
305 return (ctx->major);
306 }
Damien Miller134350c2003-09-02 22:56:42 +1000307
Darren Tucker0efd1552003-08-26 11:49:55 +1000308 if ((ctx->major = ssh_gssapi_parse_ename(ctx,&ename,
309 &client->exportedname))) {
310 return (ctx->major);
311 }
312
313 /* We can't copy this structure, so we just move the pointer to it */
314 client->creds = ctx->client_creds;
315 ctx->client_creds = GSS_C_NO_CREDENTIAL;
316 return (ctx->major);
317}
318
Darren Tucker3e33cec2003-10-02 16:12:36 +1000319/* As user - called on fatal/exit */
Darren Tucker0efd1552003-08-26 11:49:55 +1000320void
Darren Tucker3e33cec2003-10-02 16:12:36 +1000321ssh_gssapi_cleanup_creds(void)
Darren Tucker0efd1552003-08-26 11:49:55 +1000322{
323 if (gssapi_client.store.filename != NULL) {
324 /* Unlink probably isn't sufficient */
Damien Miller0b70b542006-03-15 11:20:03 +1100325 debug("removing gssapi cred file\"%s\"",
326 gssapi_client.store.filename);
Darren Tucker0efd1552003-08-26 11:49:55 +1000327 unlink(gssapi_client.store.filename);
328 }
329}
330
331/* As user */
332void
333ssh_gssapi_storecreds(void)
334{
335 if (gssapi_client.mech && gssapi_client.mech->storecreds) {
336 (*gssapi_client.mech->storecreds)(&gssapi_client);
Darren Tucker0efd1552003-08-26 11:49:55 +1000337 } else
338 debug("ssh_gssapi_storecreds: Not a GSSAPI mechanism");
339}
340
341/* This allows GSSAPI methods to do things to the childs environment based
342 * on the passed authentication process and credentials.
343 */
344/* As user */
345void
346ssh_gssapi_do_child(char ***envp, u_int *envsizep)
347{
348
349 if (gssapi_client.store.envvar != NULL &&
350 gssapi_client.store.envval != NULL) {
Darren Tucker0efd1552003-08-26 11:49:55 +1000351 debug("Setting %s to %s", gssapi_client.store.envvar,
Damien Miller6fd6def2005-11-05 15:07:05 +1100352 gssapi_client.store.envval);
Darren Tucker0efd1552003-08-26 11:49:55 +1000353 child_set_env(envp, envsizep, gssapi_client.store.envvar,
Damien Miller0dc1bef2005-07-17 17:22:45 +1000354 gssapi_client.store.envval);
Darren Tucker0efd1552003-08-26 11:49:55 +1000355 }
356}
357
Darren Tucker8813bbb2005-10-03 18:17:02 +1000358/* Privileged */
Darren Tucker0efd1552003-08-26 11:49:55 +1000359int
360ssh_gssapi_userok(char *user)
361{
Damien Millerda9984f2005-08-31 19:46:26 +1000362 OM_uint32 lmin;
363
Darren Tucker0efd1552003-08-26 11:49:55 +1000364 if (gssapi_client.exportedname.length == 0 ||
365 gssapi_client.exportedname.value == NULL) {
366 debug("No suitable client data");
367 return 0;
368 }
369 if (gssapi_client.mech && gssapi_client.mech->userok)
Damien Millerda9984f2005-08-31 19:46:26 +1000370 if ((*gssapi_client.mech->userok)(&gssapi_client, user))
371 return 1;
372 else {
373 /* Destroy delegated credentials if userok fails */
374 gss_release_buffer(&lmin, &gssapi_client.displayname);
375 gss_release_buffer(&lmin, &gssapi_client.exportedname);
376 gss_release_cred(&lmin, &gssapi_client.creds);
Damien Millera5103f42014-02-04 11:20:14 +1100377 explicit_bzero(&gssapi_client,
378 sizeof(ssh_gssapi_client));
Damien Millerda9984f2005-08-31 19:46:26 +1000379 return 0;
380 }
Darren Tucker0efd1552003-08-26 11:49:55 +1000381 else
382 debug("ssh_gssapi_userok: Unknown GSSAPI mechanism");
383 return (0);
384}
385
Damien Miller9fac2632005-11-05 15:03:48 +1100386/* Privileged */
Damien Miller0425d402003-11-17 22:18:21 +1100387OM_uint32
388ssh_gssapi_checkmic(Gssctxt *ctx, gss_buffer_t gssbuf, gss_buffer_t gssmic)
389{
390 ctx->major = gss_verify_mic(&ctx->minor, ctx->context,
391 gssbuf, gssmic, NULL);
392
393 return (ctx->major);
394}
395
djm@openbsd.org8f574952017-06-24 06:34:38 +0000396/* Privileged */
397const char *ssh_gssapi_displayname(void)
398{
399 if (gssapi_client.displayname.length == 0 ||
400 gssapi_client.displayname.value == NULL)
401 return NULL;
402 return (char *)gssapi_client.displayname.value;
403}
404
Darren Tucker0efd1552003-08-26 11:49:55 +1000405#endif