File: gss-genr.c

package info (click to toggle)
openssh 1:6.6p1-4~bpo70+1
  • links: PTS, VCS
  • area: main
  • in suites: wheezy-backports
  • size: 11,944 kB
  • sloc: ansic: 82,376; sh: 9,860; makefile: 857; awk: 339; perl: 53; python: 37; csh: 1
file content (548 lines) | stat: -rw-r--r-- 13,731 bytes parent folder | download | duplicates (3)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
/* $OpenBSD: gss-genr.c,v 1.22 2013/11/08 00:39:15 djm Exp $ */

/*
 * Copyright (c) 2001-2009 Simon Wilkinson. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR `AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include "includes.h"

#ifdef GSSAPI

#include <sys/types.h>
#include <sys/param.h>

#include <stdarg.h>
#include <string.h>
#include <unistd.h>

#include "xmalloc.h"
#include "buffer.h"
#include "log.h"
#include "ssh2.h"
#include "cipher.h"
#include "key.h"
#include "kex.h"
#include <openssl/evp.h>

#include "ssh-gss.h"

extern u_char *session_id2;
extern u_int session_id2_len;

typedef struct {
	char *encoded;
	gss_OID oid;
} ssh_gss_kex_mapping;

/*
 * XXX - It would be nice to find a more elegant way of handling the
 * XXX   passing of the key exchange context to the userauth routines
 */

Gssctxt *gss_kex_context = NULL;

static ssh_gss_kex_mapping *gss_enc2oid = NULL;

int 
ssh_gssapi_oid_table_ok(void) {
	return (gss_enc2oid != NULL);
}

/*
 * Return a list of the gss-group1-sha1 mechanisms supported by this program
 *
 * We test mechanisms to ensure that we can use them, to avoid starting
 * a key exchange with a bad mechanism
 */

char *
ssh_gssapi_client_mechanisms(const char *host, const char *client) {
	gss_OID_set gss_supported;
	OM_uint32 min_status;

	if (GSS_ERROR(gss_indicate_mechs(&min_status, &gss_supported)))
		return NULL;

	return(ssh_gssapi_kex_mechs(gss_supported, ssh_gssapi_check_mechanism,
	    host, client));
}

char *
ssh_gssapi_kex_mechs(gss_OID_set gss_supported, ssh_gssapi_check_fn *check,
    const char *host, const char *client) {
	Buffer buf;
	size_t i;
	int oidpos, enclen;
	char *mechs, *encoded;
	u_char digest[EVP_MAX_MD_SIZE];
	char deroid[2];
	const EVP_MD *evp_md = EVP_md5();
	EVP_MD_CTX md;

	if (gss_enc2oid != NULL) {
		for (i = 0; gss_enc2oid[i].encoded != NULL; i++)
			free(gss_enc2oid[i].encoded);
		free(gss_enc2oid);
	}

	gss_enc2oid = xmalloc(sizeof(ssh_gss_kex_mapping) *
	    (gss_supported->count + 1));

	buffer_init(&buf);

	oidpos = 0;
	for (i = 0; i < gss_supported->count; i++) {
		if (gss_supported->elements[i].length < 128 &&
		    (*check)(NULL, &(gss_supported->elements[i]), host, client)) {

			deroid[0] = SSH_GSS_OIDTYPE;
			deroid[1] = gss_supported->elements[i].length;

			EVP_DigestInit(&md, evp_md);
			EVP_DigestUpdate(&md, deroid, 2);
			EVP_DigestUpdate(&md,
			    gss_supported->elements[i].elements,
			    gss_supported->elements[i].length);
			EVP_DigestFinal(&md, digest, NULL);

			encoded = xmalloc(EVP_MD_size(evp_md) * 2);
			enclen = __b64_ntop(digest, EVP_MD_size(evp_md),
			    encoded, EVP_MD_size(evp_md) * 2);

			if (oidpos != 0)
				buffer_put_char(&buf, ',');

			buffer_append(&buf, KEX_GSS_GEX_SHA1_ID,
			    sizeof(KEX_GSS_GEX_SHA1_ID) - 1);
			buffer_append(&buf, encoded, enclen);
			buffer_put_char(&buf, ',');
			buffer_append(&buf, KEX_GSS_GRP1_SHA1_ID, 
			    sizeof(KEX_GSS_GRP1_SHA1_ID) - 1);
			buffer_append(&buf, encoded, enclen);
			buffer_put_char(&buf, ',');
			buffer_append(&buf, KEX_GSS_GRP14_SHA1_ID,
			    sizeof(KEX_GSS_GRP14_SHA1_ID) - 1);
			buffer_append(&buf, encoded, enclen);

			gss_enc2oid[oidpos].oid = &(gss_supported->elements[i]);
			gss_enc2oid[oidpos].encoded = encoded;
			oidpos++;
		}
	}
	gss_enc2oid[oidpos].oid = NULL;
	gss_enc2oid[oidpos].encoded = NULL;

	buffer_put_char(&buf, '\0');

	mechs = xmalloc(buffer_len(&buf));
	buffer_get(&buf, mechs, buffer_len(&buf));
	buffer_free(&buf);

	if (strlen(mechs) == 0) {
		free(mechs);
		mechs = NULL;
	}
	
	return (mechs);
}

gss_OID
ssh_gssapi_id_kex(Gssctxt *ctx, char *name, int kex_type) {
	int i = 0;
	
	switch (kex_type) {
	case KEX_GSS_GRP1_SHA1:
		if (strlen(name) < sizeof(KEX_GSS_GRP1_SHA1_ID))
			return GSS_C_NO_OID;
		name += sizeof(KEX_GSS_GRP1_SHA1_ID) - 1;
		break;
	case KEX_GSS_GRP14_SHA1:
		if (strlen(name) < sizeof(KEX_GSS_GRP14_SHA1_ID))
			return GSS_C_NO_OID;
		name += sizeof(KEX_GSS_GRP14_SHA1_ID) - 1;
		break;
	case KEX_GSS_GEX_SHA1:
		if (strlen(name) < sizeof(KEX_GSS_GEX_SHA1_ID))
			return GSS_C_NO_OID;
		name += sizeof(KEX_GSS_GEX_SHA1_ID) - 1;
		break;
	default:
		return GSS_C_NO_OID;
	}

	while (gss_enc2oid[i].encoded != NULL &&
	    strcmp(name, gss_enc2oid[i].encoded) != 0)
		i++;

	if (gss_enc2oid[i].oid != NULL && ctx != NULL)
		ssh_gssapi_set_oid(ctx, gss_enc2oid[i].oid);

	return gss_enc2oid[i].oid;
}

/* Check that the OID in a data stream matches that in the context */
int
ssh_gssapi_check_oid(Gssctxt *ctx, void *data, size_t len)
{
	return (ctx != NULL && ctx->oid != GSS_C_NO_OID &&
	    ctx->oid->length == len &&
	    memcmp(ctx->oid->elements, data, len) == 0);
}

/* Set the contexts OID from a data stream */
void
ssh_gssapi_set_oid_data(Gssctxt *ctx, void *data, size_t len)
{
	if (ctx->oid != GSS_C_NO_OID) {
		free(ctx->oid->elements);
		free(ctx->oid);
	}
	ctx->oid = xcalloc(1, sizeof(gss_OID_desc));
	ctx->oid->length = len;
	ctx->oid->elements = xmalloc(len);
	memcpy(ctx->oid->elements, data, len);
}

/* Set the contexts OID */
void
ssh_gssapi_set_oid(Gssctxt *ctx, gss_OID oid)
{
	ssh_gssapi_set_oid_data(ctx, oid->elements, oid->length);
}

/* All this effort to report an error ... */
void
ssh_gssapi_error(Gssctxt *ctxt)
{
	char *s;

	s = ssh_gssapi_last_error(ctxt, NULL, NULL);
	debug("%s", s);
	free(s);
}

char *
ssh_gssapi_last_error(Gssctxt *ctxt, OM_uint32 *major_status,
    OM_uint32 *minor_status)
{
	OM_uint32 lmin;
	gss_buffer_desc msg = GSS_C_EMPTY_BUFFER;
	OM_uint32 ctx;
	Buffer b;
	char *ret;

	buffer_init(&b);

	if (major_status != NULL)
		*major_status = ctxt->major;
	if (minor_status != NULL)
		*minor_status = ctxt->minor;

	ctx = 0;
	/* The GSSAPI error */
	do {
		gss_display_status(&lmin, ctxt->major,
		    GSS_C_GSS_CODE, ctxt->oid, &ctx, &msg);

		buffer_append(&b, msg.value, msg.length);
		buffer_put_char(&b, '\n');

		gss_release_buffer(&lmin, &msg);
	} while (ctx != 0);

	/* The mechanism specific error */
	do {
		gss_display_status(&lmin, ctxt->minor,
		    GSS_C_MECH_CODE, ctxt->oid, &ctx, &msg);

		buffer_append(&b, msg.value, msg.length);
		buffer_put_char(&b, '\n');

		gss_release_buffer(&lmin, &msg);
	} while (ctx != 0);

	buffer_put_char(&b, '\0');
	ret = xmalloc(buffer_len(&b));
	buffer_get(&b, ret, buffer_len(&b));
	buffer_free(&b);
	return (ret);
}

/*
 * Initialise our GSSAPI context. We use this opaque structure to contain all
 * of the data which both the client and server need to persist across
 * {accept,init}_sec_context calls, so that when we do it from the userauth
 * stuff life is a little easier
 */
void
ssh_gssapi_build_ctx(Gssctxt **ctx)
{
	*ctx = xcalloc(1, sizeof (Gssctxt));
	(*ctx)->context = GSS_C_NO_CONTEXT;
	(*ctx)->name = GSS_C_NO_NAME;
	(*ctx)->oid = GSS_C_NO_OID;
	(*ctx)->creds = GSS_C_NO_CREDENTIAL;
	(*ctx)->client = GSS_C_NO_NAME;
	(*ctx)->client_creds = GSS_C_NO_CREDENTIAL;
}

/* Delete our context, providing it has been built correctly */
void
ssh_gssapi_delete_ctx(Gssctxt **ctx)
{
	OM_uint32 ms;

	if ((*ctx) == NULL)
		return;
	if ((*ctx)->context != GSS_C_NO_CONTEXT)
		gss_delete_sec_context(&ms, &(*ctx)->context, GSS_C_NO_BUFFER);
	if ((*ctx)->name != GSS_C_NO_NAME)
		gss_release_name(&ms, &(*ctx)->name);
	if ((*ctx)->oid != GSS_C_NO_OID) {
		free((*ctx)->oid->elements);
		free((*ctx)->oid);
		(*ctx)->oid = GSS_C_NO_OID;
	}
	if ((*ctx)->creds != GSS_C_NO_CREDENTIAL)
		gss_release_cred(&ms, &(*ctx)->creds);
	if ((*ctx)->client != GSS_C_NO_NAME)
		gss_release_name(&ms, &(*ctx)->client);
	if ((*ctx)->client_creds != GSS_C_NO_CREDENTIAL)
		gss_release_cred(&ms, &(*ctx)->client_creds);

	free(*ctx);
	*ctx = NULL;
}

/*
 * Wrapper to init_sec_context
 * Requires that the context contains:
 *	oid
 *	server name (from ssh_gssapi_import_name)
 */
OM_uint32
ssh_gssapi_init_ctx(Gssctxt *ctx, int deleg_creds, gss_buffer_desc *recv_tok,
    gss_buffer_desc* send_tok, OM_uint32 *flags)
{
	int deleg_flag = 0;

	if (deleg_creds) {
		deleg_flag = GSS_C_DELEG_FLAG;
		debug("Delegating credentials");
	}

	ctx->major = gss_init_sec_context(&ctx->minor,
	    ctx->client_creds, &ctx->context, ctx->name, ctx->oid,
	    GSS_C_MUTUAL_FLAG | GSS_C_INTEG_FLAG | deleg_flag,
	    0, NULL, recv_tok, NULL, send_tok, flags, NULL);

	if (GSS_ERROR(ctx->major))
		ssh_gssapi_error(ctx);

	return (ctx->major);
}

/* Create a service name for the given host */
OM_uint32
ssh_gssapi_import_name(Gssctxt *ctx, const char *host)
{
	gss_buffer_desc gssbuf;
	char *val;

	xasprintf(&val, "host@%s", host);
	gssbuf.value = val;
	gssbuf.length = strlen(gssbuf.value);

	if ((ctx->major = gss_import_name(&ctx->minor,
	    &gssbuf, GSS_C_NT_HOSTBASED_SERVICE, &ctx->name)))
		ssh_gssapi_error(ctx);

	free(gssbuf.value);
	return (ctx->major);
}

OM_uint32
ssh_gssapi_client_identity(Gssctxt *ctx, const char *name)
{
	gss_buffer_desc gssbuf;
	gss_name_t gssname;
	OM_uint32 status;
	gss_OID_set oidset;

	gssbuf.value = (void *) name;
	gssbuf.length = strlen(gssbuf.value);

	gss_create_empty_oid_set(&status, &oidset);
	gss_add_oid_set_member(&status, ctx->oid, &oidset);

	ctx->major = gss_import_name(&ctx->minor, &gssbuf,
	    GSS_C_NT_USER_NAME, &gssname);

	if (!ctx->major)
		ctx->major = gss_acquire_cred(&ctx->minor, 
		    gssname, 0, oidset, GSS_C_INITIATE, 
		    &ctx->client_creds, NULL, NULL);

	gss_release_name(&status, &gssname);
	gss_release_oid_set(&status, &oidset);

	if (ctx->major)
		ssh_gssapi_error(ctx);

	return(ctx->major);
}

OM_uint32
ssh_gssapi_sign(Gssctxt *ctx, gss_buffer_t buffer, gss_buffer_t hash)
{
	if (ctx == NULL) 
		return -1;

	if ((ctx->major = gss_get_mic(&ctx->minor, ctx->context,
	    GSS_C_QOP_DEFAULT, buffer, hash)))
		ssh_gssapi_error(ctx);

	return (ctx->major);
}

/* Priviledged when used by server */
OM_uint32
ssh_gssapi_checkmic(Gssctxt *ctx, gss_buffer_t gssbuf, gss_buffer_t gssmic)
{
	if (ctx == NULL)
		return -1;

	ctx->major = gss_verify_mic(&ctx->minor, ctx->context,
	    gssbuf, gssmic, NULL);

	return (ctx->major);
}

void
ssh_gssapi_buildmic(Buffer *b, const char *user, const char *service,
    const char *context)
{
	buffer_init(b);
	buffer_put_string(b, session_id2, session_id2_len);
	buffer_put_char(b, SSH2_MSG_USERAUTH_REQUEST);
	buffer_put_cstring(b, user);
	buffer_put_cstring(b, service);
	buffer_put_cstring(b, context);
}

int
ssh_gssapi_check_mechanism(Gssctxt **ctx, gss_OID oid, const char *host, 
    const char *client)
{
	gss_buffer_desc token = GSS_C_EMPTY_BUFFER;
	OM_uint32 major, minor;
	gss_OID_desc spnego_oid = {6, (void *)"\x2B\x06\x01\x05\x05\x02"};
	Gssctxt *intctx = NULL;

	if (ctx == NULL)
		ctx = &intctx;

	/* RFC 4462 says we MUST NOT do SPNEGO */
	if (oid->length == spnego_oid.length && 
	    (memcmp(oid->elements, spnego_oid.elements, oid->length) == 0))
		return 0; /* false */

	ssh_gssapi_build_ctx(ctx);
	ssh_gssapi_set_oid(*ctx, oid);
	major = ssh_gssapi_import_name(*ctx, host);

	if (!GSS_ERROR(major) && client)
		major = ssh_gssapi_client_identity(*ctx, client);

	if (!GSS_ERROR(major)) {
		major = ssh_gssapi_init_ctx(*ctx, 0, GSS_C_NO_BUFFER, &token, 
		    NULL);
		gss_release_buffer(&minor, &token);
		if ((*ctx)->context != GSS_C_NO_CONTEXT)
			gss_delete_sec_context(&minor, &(*ctx)->context,
			    GSS_C_NO_BUFFER);
	}

	if (GSS_ERROR(major) || intctx != NULL) 
		ssh_gssapi_delete_ctx(ctx);

	return (!GSS_ERROR(major));
}

int
ssh_gssapi_credentials_updated(Gssctxt *ctxt) {
	static gss_name_t saved_name = GSS_C_NO_NAME;
	static OM_uint32 saved_lifetime = 0;
	static gss_OID saved_mech = GSS_C_NO_OID;
	static gss_name_t name;
	static OM_uint32 last_call = 0;
	OM_uint32 lifetime, now, major, minor;
	int equal;
	
	now = time(NULL);

	if (ctxt) {
		debug("Rekey has happened - updating saved versions");

		if (saved_name != GSS_C_NO_NAME)
			gss_release_name(&minor, &saved_name);

		major = gss_inquire_cred(&minor, GSS_C_NO_CREDENTIAL,
		    &saved_name, &saved_lifetime, NULL, NULL);

		if (!GSS_ERROR(major)) {
			saved_mech = ctxt->oid;
		        saved_lifetime+= now;
		} else {
			/* Handle the error */
		}
		return 0;
	}

	if (now - last_call < 10)
		return 0;

	last_call = now;

	if (saved_mech == GSS_C_NO_OID)
		return 0;
	
	major = gss_inquire_cred(&minor, GSS_C_NO_CREDENTIAL, 
	    &name, &lifetime, NULL, NULL);
	if (major == GSS_S_CREDENTIALS_EXPIRED)
		return 0;
	else if (GSS_ERROR(major))
		return 0;

	major = gss_compare_name(&minor, saved_name, name, &equal);
	gss_release_name(&minor, &name);
	if (GSS_ERROR(major))
		return 0;

	if (equal && (saved_lifetime < lifetime + now - 10))
		return 1;

	return 0;
}

#endif /* GSSAPI */