summaryrefslogtreecommitdiff
path: root/security/selinux/xfrm.c
blob: 8f17f542a1160bc44ccff63f8a0fe07e756e86b5 (plain)
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
/*
 *  NSA Security-Enhanced Linux (SELinux) security module
 *
 *  This file contains the SELinux XFRM hook function implementations.
 *
 *  Authors:  Serge Hallyn <sergeh@us.ibm.com>
 *	      Trent Jaeger <jaegert@us.ibm.com>
 *
 *  Updated: Venkat Yekkirala <vyekkirala@TrustedCS.com>
 *
 *           Granular IPSec Associations for use in MLS environments.
 *
 *  Copyright (C) 2005 International Business Machines Corporation
 *  Copyright (C) 2006 Trusted Computer Solutions, Inc.
 *
 *	This program is free software; you can redistribute it and/or modify
 *	it under the terms of the GNU General Public License version 2,
 *	as published by the Free Software Foundation.
 */

/*
 * USAGE:
 * NOTES:
 *   1. Make sure to enable the following options in your kernel config:
 *	CONFIG_SECURITY=y
 *	CONFIG_SECURITY_NETWORK=y
 *	CONFIG_SECURITY_NETWORK_XFRM=y
 *	CONFIG_SECURITY_SELINUX=m/y
 * ISSUES:
 *   1. Caching packets, so they are not dropped during negotiation
 *   2. Emulating a reasonable SO_PEERSEC across machines
 *   3. Testing addition of sk_policy's with security context via setsockopt
 */
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/security.h>
#include <linux/types.h>
#include <linux/netfilter.h>
#include <linux/netfilter_ipv4.h>
#include <linux/netfilter_ipv6.h>
#include <linux/ip.h>
#include <linux/tcp.h>
#include <linux/skbuff.h>
#include <linux/xfrm.h>
#include <net/xfrm.h>
#include <net/checksum.h>
#include <net/udp.h>
#include <asm/atomic.h>

#include "avc.h"
#include "objsec.h"
#include "xfrm.h"

/* Labeled XFRM instance counter */
atomic_t selinux_xfrm_refcount = ATOMIC_INIT(0);

/*
 * Returns true if an LSM/SELinux context
 */
static inline int selinux_authorizable_ctx(struct xfrm_sec_ctx *ctx)
{
	return (ctx &&
		(ctx->ctx_doi == XFRM_SC_DOI_LSM) &&
		(ctx->ctx_alg == XFRM_SC_ALG_SELINUX));
}

/*
 * Returns true if the xfrm contains a security blob for SELinux
 */
static inline int selinux_authorizable_xfrm(struct xfrm_state *x)
{
	return selinux_authorizable_ctx(x->security);
}

/*
 * LSM hook implementation that authorizes that a flow can use
 * a xfrm policy rule.
 */
int selinux_xfrm_policy_lookup(struct xfrm_sec_ctx *ctx, u32 fl_secid, u8 dir)
{
	int rc;
	u32 sel_sid;

	/* Context sid is either set to label or ANY_ASSOC */
	if (ctx) {
		if (!selinux_authorizable_ctx(ctx))
			return -EINVAL;

		sel_sid = ctx->ctx_sid;
	} else
		/*
		 * All flows should be treated as polmatch'ing an
		 * otherwise applicable "non-labeled" policy. This
		 * would prevent inadvertent "leaks".
		 */
		return 0;

	rc = avc_has_perm(fl_secid, sel_sid, SECCLASS_ASSOCIATION,
			  ASSOCIATION__POLMATCH,
			  NULL);

	if (rc == -EACCES)
		return -ESRCH;

	return rc;
}

/*
 * LSM hook implementation that authorizes that a state matches
 * the given policy, flow combo.
 */

int selinux_xfrm_state_pol_flow_match(struct xfrm_state *x, struct xfrm_policy *xp,
			struct flowi *fl)
{
	u32 state_sid;
	int rc;

	if (!xp->security)
		if (x->security)
			/* unlabeled policy and labeled SA can't match */
			return 0;
		else
			/* unlabeled policy and unlabeled SA match all flows */
			return 1;
	else
		if (!x->security)
			/* unlabeled SA and labeled policy can't match */
			return 0;
		else
			if (!selinux_authorizable_xfrm(x))
				/* Not a SELinux-labeled SA */
				return 0;

	state_sid = x->security->ctx_sid;

	if (fl->secid != state_sid)
		return 0;

	rc = avc_has_perm(fl->secid, state_sid, SECCLASS_ASSOCIATION,
			  ASSOCIATION__SENDTO,
			  NULL)? 0:1;

	/*
	 * We don't need a separate SA Vs. policy polmatch check
	 * since the SA is now of the same label as the flow and
	 * a flow Vs. policy polmatch check had already happened
	 * in selinux_xfrm_policy_lookup() above.
	 */

	return rc;
}

/*
 * LSM hook implementation that checks and/or returns the xfrm sid for the
 * incoming packet.
 */

int selinux_xfrm_decode_session(struct sk_buff *skb, u32 *sid, int ckall)
{
	struct sec_path *sp;

	*sid = SECSID_NULL;

	if (skb == NULL)
		return 0;

	sp = skb->sp;
	if (sp) {
		int i, sid_set = 0;

		for (i = sp->len-1; i >= 0; i--) {
			struct xfrm_state *x = sp->xvec[i];
			if (selinux_authorizable_xfrm(x)) {
				struct xfrm_sec_ctx *ctx = x->security;

				if (!sid_set) {
					*sid = ctx->ctx_sid;
					sid_set = 1;

					if (!ckall)
						break;
				} else if (*sid != ctx->ctx_sid)
					return -EINVAL;
			}
		}
	}

	return 0;
}

/*
 * Security blob allocation for xfrm_policy and xfrm_state
 * CTX does not have a meaningful value on input
 */
static int selinux_xfrm_sec_ctx_alloc(struct xfrm_sec_ctx **ctxp,
	struct xfrm_user_sec_ctx *uctx, u32 sid)
{
	int rc = 0;
	struct task_security_struct *tsec = current->security;
	struct xfrm_sec_ctx *ctx = NULL;
	char *ctx_str = NULL;
	u32 str_len;

	BUG_ON(uctx && sid);

	if (!uctx)
		goto not_from_user;

	if (uctx->ctx_doi != XFRM_SC_ALG_SELINUX)
		return -EINVAL;

	str_len = uctx->ctx_len;
	if (str_len >= PAGE_SIZE)
		return -ENOMEM;

	*ctxp = ctx = kmalloc(sizeof(*ctx) +
			      str_len + 1,
			      GFP_KERNEL);

	if (!ctx)
		return -ENOMEM;

	ctx->ctx_doi = uctx->ctx_doi;
	ctx->ctx_len = str_len;
	ctx->ctx_alg = uctx->ctx_alg;

	memcpy(ctx->ctx_str,
	       uctx+1,
	       str_len);
	ctx->ctx_str[str_len] = 0;
	rc = security_context_to_sid(ctx->ctx_str,
				     str_len,
				     &ctx->ctx_sid);

	if (rc)
		goto out;

	/*
	 * Does the subject have permission to set security context?
	 */
	rc = avc_has_perm(tsec->sid, ctx->ctx_sid,
			  SECCLASS_ASSOCIATION,
			  ASSOCIATION__SETCONTEXT, NULL);
	if (rc)
		goto out;

	return rc;

not_from_user:
	rc = security_sid_to_context(sid, &ctx_str, &str_len);
	if (rc)
		goto out;

	*ctxp = ctx = kmalloc(sizeof(*ctx) +
			      str_len,
			      GFP_ATOMIC);

	if (!ctx) {
		rc = -ENOMEM;
		goto out;
	}

	ctx->ctx_doi = XFRM_SC_DOI_LSM;
	ctx->ctx_alg = XFRM_SC_ALG_SELINUX;
	ctx->ctx_sid = sid;
	ctx->ctx_len = str_len;
	memcpy(ctx->ctx_str,
	       ctx_str,
	       str_len);

	goto out2;

out:
	*ctxp = NULL;
	kfree(ctx);
out2:
	kfree(ctx_str);
	return rc;
}

/*
 * LSM hook implementation that allocs and transfers uctx spec to
 * xfrm_policy.
 */
int selinux_xfrm_policy_alloc(struct xfrm_sec_ctx **ctxp,
			      struct xfrm_user_sec_ctx *uctx)
{
	int err;

	BUG_ON(!uctx);

	err = selinux_xfrm_sec_ctx_alloc(ctxp, uctx, 0);
	if (err == 0)
		atomic_inc(&selinux_xfrm_refcount);

	return err;
}


/*
 * LSM hook implementation that copies security data structure from old to
 * new for policy cloning.
 */
int selinux_xfrm_policy_clone(struct xfrm_sec_ctx *old_ctx,
			      struct xfrm_sec_ctx **new_ctxp)
{
	struct xfrm_sec_ctx *new_ctx;

	if (old_ctx) {
		new_ctx = kmalloc(sizeof(*old_ctx) + old_ctx->ctx_len,
				  GFP_KERNEL);
		if (!new_ctx)
			return -ENOMEM;

		memcpy(new_ctx, old_ctx, sizeof(*new_ctx));
		memcpy(new_ctx->ctx_str, old_ctx->ctx_str, new_ctx->ctx_len);
		*new_ctxp = new_ctx;
	}
	return 0;
}

/*
 * LSM hook implementation that frees xfrm_sec_ctx security information.
 */
void selinux_xfrm_policy_free(struct xfrm_sec_ctx *ctx)
{
	kfree(ctx);
}

/*
 * LSM hook implementation that authorizes deletion of labeled policies.
 */
int selinux_xfrm_policy_delete(struct xfrm_sec_ctx *ctx)
{
	struct task_security_struct *tsec = current->security;
	int rc = 0;

	if (ctx) {
		rc = avc_has_perm(tsec->sid, ctx->ctx_sid,
				  SECCLASS_ASSOCIATION,
				  ASSOCIATION__SETCONTEXT, NULL);
		if (rc == 0)
			atomic_dec(&selinux_xfrm_refcount);
	}

	return rc;
}

/*
 * LSM hook implementation that allocs and transfers sec_ctx spec to
 * xfrm_state.
 */
int selinux_xfrm_state_alloc(struct xfrm_state *x, struct xfrm_user_sec_ctx *uctx,
		u32 secid)
{
	int err;

	BUG_ON(!x);

	err = selinux_xfrm_sec_ctx_alloc(&x->security, uctx, secid);
	if (err == 0)
		atomic_inc(&selinux_xfrm_refcount);
	return err;
}

/*
 * LSM hook implementation that frees xfrm_state security information.
 */
void selinux_xfrm_state_free(struct xfrm_state *x)
{
	struct xfrm_sec_ctx *ctx = x->security;
	kfree(ctx);
}

 /*
  * LSM hook implementation that authorizes deletion of labeled SAs.
  */
int selinux_xfrm_state_delete(struct xfrm_state *x)
{
	struct task_security_struct *tsec = current->security;
	struct xfrm_sec_ctx *ctx = x->security;
	int rc = 0;

	if (ctx) {
		rc = avc_has_perm(tsec->sid, ctx->ctx_sid,
				  SECCLASS_ASSOCIATION,
				  ASSOCIATION__SETCONTEXT, NULL);
		if (rc == 0)
			atomic_dec(&selinux_xfrm_refcount);
	}

	return rc;
}

/*
 * LSM hook that controls access to unlabelled packets.  If
 * a xfrm_state is authorizable (defined by macro) then it was
 * already authorized by the IPSec process.  If not, then
 * we need to check for unlabelled access since this may not have
 * gone thru the IPSec process.
 */
int selinux_xfrm_sock_rcv_skb(u32 isec_sid, struct sk_buff *skb,
				struct avc_audit_data *ad)
{
	int i, rc = 0;
	struct sec_path *sp;
	u32 sel_sid = SECINITSID_UNLABELED;

	sp = skb->sp;

	if (sp) {
		for (i = 0; i < sp->len; i++) {
			struct xfrm_state *x = sp->xvec[i];

			if (x && selinux_authorizable_xfrm(x)) {
				struct xfrm_sec_ctx *ctx = x->security;
				sel_sid = ctx->ctx_sid;
				break;
			}
		}
	}

	/*
	 * This check even when there's no association involved is
	 * intended, according to Trent Jaeger, to make sure a
	 * process can't engage in non-ipsec communication unless
	 * explicitly allowed by policy.
	 */

	rc = avc_has_perm(isec_sid, sel_sid, SECCLASS_ASSOCIATION,
			  ASSOCIATION__RECVFROM, ad);

	return rc;
}

/*
 * POSTROUTE_LAST hook's XFRM processing:
 * If we have no security association, then we need to determine
 * whether the socket is allowed to send to an unlabelled destination.
 * If we do have a authorizable security association, then it has already been
 * checked in the selinux_xfrm_state_pol_flow_match hook above.
 */
int selinux_xfrm_postroute_last(u32 isec_sid, struct sk_buff *skb,
					struct avc_audit_data *ad, u8 proto)
{
	struct dst_entry *dst;
	int rc = 0;

	dst = skb->dst;

	if (dst) {
		struct dst_entry *dst_test;

		for (dst_test = dst; dst_test != NULL;
		     dst_test = dst_test->child) {
			struct xfrm_state *x = dst_test->xfrm;

			if (x && selinux_authorizable_xfrm(x))
				goto out;
		}
	}

	switch (proto) {
	case IPPROTO_AH:
	case IPPROTO_ESP:
	case IPPROTO_COMP:
		/*
		 * We should have already seen this packet once before
		 * it underwent xfrm(s). No need to subject it to the
		 * unlabeled check.
		 */
		goto out;
	default:
		break;
	}

	/*
	 * This check even when there's no association involved is
	 * intended, according to Trent Jaeger, to make sure a
	 * process can't engage in non-ipsec communication unless
	 * explicitly allowed by policy.
	 */

	rc = avc_has_perm(isec_sid, SECINITSID_UNLABELED, SECCLASS_ASSOCIATION,
			  ASSOCIATION__SENDTO, ad);
out:
	return rc;
}