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1 | /* | |
2 | * NSA Security-Enhanced Linux (SELinux) security module | |
3 | * | |
4 | * This file contains the SELinux XFRM hook function implementations. | |
5 | * | |
6 | * Authors: Serge Hallyn <sergeh@us.ibm.com> | |
7 | * Trent Jaeger <jaegert@us.ibm.com> | |
8 | * | |
9 | * Updated: Venkat Yekkirala <vyekkirala@TrustedCS.com> | |
10 | * | |
11 | * Granular IPSec Associations for use in MLS environments. | |
12 | * | |
13 | * Copyright (C) 2005 International Business Machines Corporation | |
14 | * Copyright (C) 2006 Trusted Computer Solutions, Inc. | |
15 | * | |
16 | * This program is free software; you can redistribute it and/or modify | |
17 | * it under the terms of the GNU General Public License version 2, | |
18 | * as published by the Free Software Foundation. | |
19 | */ | |
20 | ||
21 | /* | |
22 | * USAGE: | |
23 | * NOTES: | |
24 | * 1. Make sure to enable the following options in your kernel config: | |
25 | * CONFIG_SECURITY=y | |
26 | * CONFIG_SECURITY_NETWORK=y | |
27 | * CONFIG_SECURITY_NETWORK_XFRM=y | |
28 | * CONFIG_SECURITY_SELINUX=m/y | |
29 | * ISSUES: | |
30 | * 1. Caching packets, so they are not dropped during negotiation | |
31 | * 2. Emulating a reasonable SO_PEERSEC across machines | |
32 | * 3. Testing addition of sk_policy's with security context via setsockopt | |
33 | */ | |
34 | #include <linux/kernel.h> | |
35 | #include <linux/init.h> | |
36 | #include <linux/security.h> | |
37 | #include <linux/types.h> | |
38 | #include <linux/netfilter.h> | |
39 | #include <linux/netfilter_ipv4.h> | |
40 | #include <linux/netfilter_ipv6.h> | |
41 | #include <linux/slab.h> | |
42 | #include <linux/ip.h> | |
43 | #include <linux/tcp.h> | |
44 | #include <linux/skbuff.h> | |
45 | #include <linux/xfrm.h> | |
46 | #include <net/xfrm.h> | |
47 | #include <net/checksum.h> | |
48 | #include <net/udp.h> | |
49 | #include <asm/atomic.h> | |
50 | ||
51 | #include "avc.h" | |
52 | #include "objsec.h" | |
53 | #include "xfrm.h" | |
54 | ||
55 | /* Labeled XFRM instance counter */ | |
56 | atomic_t selinux_xfrm_refcount = ATOMIC_INIT(0); | |
57 | ||
58 | /* | |
59 | * Returns true if an LSM/SELinux context | |
60 | */ | |
61 | static inline int selinux_authorizable_ctx(struct xfrm_sec_ctx *ctx) | |
62 | { | |
63 | return (ctx && | |
64 | (ctx->ctx_doi == XFRM_SC_DOI_LSM) && | |
65 | (ctx->ctx_alg == XFRM_SC_ALG_SELINUX)); | |
66 | } | |
67 | ||
68 | /* | |
69 | * Returns true if the xfrm contains a security blob for SELinux | |
70 | */ | |
71 | static inline int selinux_authorizable_xfrm(struct xfrm_state *x) | |
72 | { | |
73 | return selinux_authorizable_ctx(x->security); | |
74 | } | |
75 | ||
76 | /* | |
77 | * LSM hook implementation that authorizes that a flow can use | |
78 | * a xfrm policy rule. | |
79 | */ | |
80 | int selinux_xfrm_policy_lookup(struct xfrm_sec_ctx *ctx, u32 fl_secid, u8 dir) | |
81 | { | |
82 | int rc; | |
83 | u32 sel_sid; | |
84 | ||
85 | /* Context sid is either set to label or ANY_ASSOC */ | |
86 | if (ctx) { | |
87 | if (!selinux_authorizable_ctx(ctx)) | |
88 | return -EINVAL; | |
89 | ||
90 | sel_sid = ctx->ctx_sid; | |
91 | } else | |
92 | /* | |
93 | * All flows should be treated as polmatch'ing an | |
94 | * otherwise applicable "non-labeled" policy. This | |
95 | * would prevent inadvertent "leaks". | |
96 | */ | |
97 | return 0; | |
98 | ||
99 | rc = avc_has_perm(fl_secid, sel_sid, SECCLASS_ASSOCIATION, | |
100 | ASSOCIATION__POLMATCH, | |
101 | NULL); | |
102 | ||
103 | if (rc == -EACCES) | |
104 | return -ESRCH; | |
105 | ||
106 | return rc; | |
107 | } | |
108 | ||
109 | /* | |
110 | * LSM hook implementation that authorizes that a state matches | |
111 | * the given policy, flow combo. | |
112 | */ | |
113 | ||
114 | int selinux_xfrm_state_pol_flow_match(struct xfrm_state *x, struct xfrm_policy *xp, | |
115 | struct flowi *fl) | |
116 | { | |
117 | u32 state_sid; | |
118 | int rc; | |
119 | ||
120 | if (!xp->security) | |
121 | if (x->security) | |
122 | /* unlabeled policy and labeled SA can't match */ | |
123 | return 0; | |
124 | else | |
125 | /* unlabeled policy and unlabeled SA match all flows */ | |
126 | return 1; | |
127 | else | |
128 | if (!x->security) | |
129 | /* unlabeled SA and labeled policy can't match */ | |
130 | return 0; | |
131 | else | |
132 | if (!selinux_authorizable_xfrm(x)) | |
133 | /* Not a SELinux-labeled SA */ | |
134 | return 0; | |
135 | ||
136 | state_sid = x->security->ctx_sid; | |
137 | ||
138 | if (fl->secid != state_sid) | |
139 | return 0; | |
140 | ||
141 | rc = avc_has_perm(fl->secid, state_sid, SECCLASS_ASSOCIATION, | |
142 | ASSOCIATION__SENDTO, | |
143 | NULL)? 0:1; | |
144 | ||
145 | /* | |
146 | * We don't need a separate SA Vs. policy polmatch check | |
147 | * since the SA is now of the same label as the flow and | |
148 | * a flow Vs. policy polmatch check had already happened | |
149 | * in selinux_xfrm_policy_lookup() above. | |
150 | */ | |
151 | ||
152 | return rc; | |
153 | } | |
154 | ||
155 | /* | |
156 | * LSM hook implementation that checks and/or returns the xfrm sid for the | |
157 | * incoming packet. | |
158 | */ | |
159 | ||
160 | int selinux_xfrm_decode_session(struct sk_buff *skb, u32 *sid, int ckall) | |
161 | { | |
162 | struct sec_path *sp; | |
163 | ||
164 | *sid = SECSID_NULL; | |
165 | ||
166 | if (skb == NULL) | |
167 | return 0; | |
168 | ||
169 | sp = skb->sp; | |
170 | if (sp) { | |
171 | int i, sid_set = 0; | |
172 | ||
173 | for (i = sp->len-1; i >= 0; i--) { | |
174 | struct xfrm_state *x = sp->xvec[i]; | |
175 | if (selinux_authorizable_xfrm(x)) { | |
176 | struct xfrm_sec_ctx *ctx = x->security; | |
177 | ||
178 | if (!sid_set) { | |
179 | *sid = ctx->ctx_sid; | |
180 | sid_set = 1; | |
181 | ||
182 | if (!ckall) | |
183 | break; | |
184 | } else if (*sid != ctx->ctx_sid) | |
185 | return -EINVAL; | |
186 | } | |
187 | } | |
188 | } | |
189 | ||
190 | return 0; | |
191 | } | |
192 | ||
193 | /* | |
194 | * Security blob allocation for xfrm_policy and xfrm_state | |
195 | * CTX does not have a meaningful value on input | |
196 | */ | |
197 | static int selinux_xfrm_sec_ctx_alloc(struct xfrm_sec_ctx **ctxp, | |
198 | struct xfrm_user_sec_ctx *uctx, u32 sid) | |
199 | { | |
200 | int rc = 0; | |
201 | const struct task_security_struct *tsec = current_security(); | |
202 | struct xfrm_sec_ctx *ctx = NULL; | |
203 | char *ctx_str = NULL; | |
204 | u32 str_len; | |
205 | ||
206 | BUG_ON(uctx && sid); | |
207 | ||
208 | if (!uctx) | |
209 | goto not_from_user; | |
210 | ||
211 | if (uctx->ctx_doi != XFRM_SC_ALG_SELINUX) | |
212 | return -EINVAL; | |
213 | ||
214 | str_len = uctx->ctx_len; | |
215 | if (str_len >= PAGE_SIZE) | |
216 | return -ENOMEM; | |
217 | ||
218 | *ctxp = ctx = kmalloc(sizeof(*ctx) + | |
219 | str_len + 1, | |
220 | GFP_KERNEL); | |
221 | ||
222 | if (!ctx) | |
223 | return -ENOMEM; | |
224 | ||
225 | ctx->ctx_doi = uctx->ctx_doi; | |
226 | ctx->ctx_len = str_len; | |
227 | ctx->ctx_alg = uctx->ctx_alg; | |
228 | ||
229 | memcpy(ctx->ctx_str, | |
230 | uctx+1, | |
231 | str_len); | |
232 | ctx->ctx_str[str_len] = 0; | |
233 | rc = security_context_to_sid(ctx->ctx_str, | |
234 | str_len, | |
235 | &ctx->ctx_sid); | |
236 | ||
237 | if (rc) | |
238 | goto out; | |
239 | ||
240 | /* | |
241 | * Does the subject have permission to set security context? | |
242 | */ | |
243 | rc = avc_has_perm(tsec->sid, ctx->ctx_sid, | |
244 | SECCLASS_ASSOCIATION, | |
245 | ASSOCIATION__SETCONTEXT, NULL); | |
246 | if (rc) | |
247 | goto out; | |
248 | ||
249 | return rc; | |
250 | ||
251 | not_from_user: | |
252 | rc = security_sid_to_context(sid, &ctx_str, &str_len); | |
253 | if (rc) | |
254 | goto out; | |
255 | ||
256 | *ctxp = ctx = kmalloc(sizeof(*ctx) + | |
257 | str_len, | |
258 | GFP_ATOMIC); | |
259 | ||
260 | if (!ctx) { | |
261 | rc = -ENOMEM; | |
262 | goto out; | |
263 | } | |
264 | ||
265 | ctx->ctx_doi = XFRM_SC_DOI_LSM; | |
266 | ctx->ctx_alg = XFRM_SC_ALG_SELINUX; | |
267 | ctx->ctx_sid = sid; | |
268 | ctx->ctx_len = str_len; | |
269 | memcpy(ctx->ctx_str, | |
270 | ctx_str, | |
271 | str_len); | |
272 | ||
273 | goto out2; | |
274 | ||
275 | out: | |
276 | *ctxp = NULL; | |
277 | kfree(ctx); | |
278 | out2: | |
279 | kfree(ctx_str); | |
280 | return rc; | |
281 | } | |
282 | ||
283 | /* | |
284 | * LSM hook implementation that allocs and transfers uctx spec to | |
285 | * xfrm_policy. | |
286 | */ | |
287 | int selinux_xfrm_policy_alloc(struct xfrm_sec_ctx **ctxp, | |
288 | struct xfrm_user_sec_ctx *uctx) | |
289 | { | |
290 | int err; | |
291 | ||
292 | BUG_ON(!uctx); | |
293 | ||
294 | err = selinux_xfrm_sec_ctx_alloc(ctxp, uctx, 0); | |
295 | if (err == 0) | |
296 | atomic_inc(&selinux_xfrm_refcount); | |
297 | ||
298 | return err; | |
299 | } | |
300 | ||
301 | ||
302 | /* | |
303 | * LSM hook implementation that copies security data structure from old to | |
304 | * new for policy cloning. | |
305 | */ | |
306 | int selinux_xfrm_policy_clone(struct xfrm_sec_ctx *old_ctx, | |
307 | struct xfrm_sec_ctx **new_ctxp) | |
308 | { | |
309 | struct xfrm_sec_ctx *new_ctx; | |
310 | ||
311 | if (old_ctx) { | |
312 | new_ctx = kmalloc(sizeof(*old_ctx) + old_ctx->ctx_len, | |
313 | GFP_KERNEL); | |
314 | if (!new_ctx) | |
315 | return -ENOMEM; | |
316 | ||
317 | memcpy(new_ctx, old_ctx, sizeof(*new_ctx)); | |
318 | memcpy(new_ctx->ctx_str, old_ctx->ctx_str, new_ctx->ctx_len); | |
319 | *new_ctxp = new_ctx; | |
320 | } | |
321 | return 0; | |
322 | } | |
323 | ||
324 | /* | |
325 | * LSM hook implementation that frees xfrm_sec_ctx security information. | |
326 | */ | |
327 | void selinux_xfrm_policy_free(struct xfrm_sec_ctx *ctx) | |
328 | { | |
329 | kfree(ctx); | |
330 | } | |
331 | ||
332 | /* | |
333 | * LSM hook implementation that authorizes deletion of labeled policies. | |
334 | */ | |
335 | int selinux_xfrm_policy_delete(struct xfrm_sec_ctx *ctx) | |
336 | { | |
337 | const struct task_security_struct *tsec = current_security(); | |
338 | int rc = 0; | |
339 | ||
340 | if (ctx) { | |
341 | rc = avc_has_perm(tsec->sid, ctx->ctx_sid, | |
342 | SECCLASS_ASSOCIATION, | |
343 | ASSOCIATION__SETCONTEXT, NULL); | |
344 | if (rc == 0) | |
345 | atomic_dec(&selinux_xfrm_refcount); | |
346 | } | |
347 | ||
348 | return rc; | |
349 | } | |
350 | ||
351 | /* | |
352 | * LSM hook implementation that allocs and transfers sec_ctx spec to | |
353 | * xfrm_state. | |
354 | */ | |
355 | int selinux_xfrm_state_alloc(struct xfrm_state *x, struct xfrm_user_sec_ctx *uctx, | |
356 | u32 secid) | |
357 | { | |
358 | int err; | |
359 | ||
360 | BUG_ON(!x); | |
361 | ||
362 | err = selinux_xfrm_sec_ctx_alloc(&x->security, uctx, secid); | |
363 | if (err == 0) | |
364 | atomic_inc(&selinux_xfrm_refcount); | |
365 | return err; | |
366 | } | |
367 | ||
368 | /* | |
369 | * LSM hook implementation that frees xfrm_state security information. | |
370 | */ | |
371 | void selinux_xfrm_state_free(struct xfrm_state *x) | |
372 | { | |
373 | struct xfrm_sec_ctx *ctx = x->security; | |
374 | kfree(ctx); | |
375 | } | |
376 | ||
377 | /* | |
378 | * LSM hook implementation that authorizes deletion of labeled SAs. | |
379 | */ | |
380 | int selinux_xfrm_state_delete(struct xfrm_state *x) | |
381 | { | |
382 | const struct task_security_struct *tsec = current_security(); | |
383 | struct xfrm_sec_ctx *ctx = x->security; | |
384 | int rc = 0; | |
385 | ||
386 | if (ctx) { | |
387 | rc = avc_has_perm(tsec->sid, ctx->ctx_sid, | |
388 | SECCLASS_ASSOCIATION, | |
389 | ASSOCIATION__SETCONTEXT, NULL); | |
390 | if (rc == 0) | |
391 | atomic_dec(&selinux_xfrm_refcount); | |
392 | } | |
393 | ||
394 | return rc; | |
395 | } | |
396 | ||
397 | /* | |
398 | * LSM hook that controls access to unlabelled packets. If | |
399 | * a xfrm_state is authorizable (defined by macro) then it was | |
400 | * already authorized by the IPSec process. If not, then | |
401 | * we need to check for unlabelled access since this may not have | |
402 | * gone thru the IPSec process. | |
403 | */ | |
404 | int selinux_xfrm_sock_rcv_skb(u32 isec_sid, struct sk_buff *skb, | |
405 | struct common_audit_data *ad) | |
406 | { | |
407 | int i, rc = 0; | |
408 | struct sec_path *sp; | |
409 | u32 sel_sid = SECINITSID_UNLABELED; | |
410 | ||
411 | sp = skb->sp; | |
412 | ||
413 | if (sp) { | |
414 | for (i = 0; i < sp->len; i++) { | |
415 | struct xfrm_state *x = sp->xvec[i]; | |
416 | ||
417 | if (x && selinux_authorizable_xfrm(x)) { | |
418 | struct xfrm_sec_ctx *ctx = x->security; | |
419 | sel_sid = ctx->ctx_sid; | |
420 | break; | |
421 | } | |
422 | } | |
423 | } | |
424 | ||
425 | /* | |
426 | * This check even when there's no association involved is | |
427 | * intended, according to Trent Jaeger, to make sure a | |
428 | * process can't engage in non-ipsec communication unless | |
429 | * explicitly allowed by policy. | |
430 | */ | |
431 | ||
432 | rc = avc_has_perm(isec_sid, sel_sid, SECCLASS_ASSOCIATION, | |
433 | ASSOCIATION__RECVFROM, ad); | |
434 | ||
435 | return rc; | |
436 | } | |
437 | ||
438 | /* | |
439 | * POSTROUTE_LAST hook's XFRM processing: | |
440 | * If we have no security association, then we need to determine | |
441 | * whether the socket is allowed to send to an unlabelled destination. | |
442 | * If we do have a authorizable security association, then it has already been | |
443 | * checked in the selinux_xfrm_state_pol_flow_match hook above. | |
444 | */ | |
445 | int selinux_xfrm_postroute_last(u32 isec_sid, struct sk_buff *skb, | |
446 | struct common_audit_data *ad, u8 proto) | |
447 | { | |
448 | struct dst_entry *dst; | |
449 | int rc = 0; | |
450 | ||
451 | dst = skb_dst(skb); | |
452 | ||
453 | if (dst) { | |
454 | struct dst_entry *dst_test; | |
455 | ||
456 | for (dst_test = dst; dst_test != NULL; | |
457 | dst_test = dst_test->child) { | |
458 | struct xfrm_state *x = dst_test->xfrm; | |
459 | ||
460 | if (x && selinux_authorizable_xfrm(x)) | |
461 | goto out; | |
462 | } | |
463 | } | |
464 | ||
465 | switch (proto) { | |
466 | case IPPROTO_AH: | |
467 | case IPPROTO_ESP: | |
468 | case IPPROTO_COMP: | |
469 | /* | |
470 | * We should have already seen this packet once before | |
471 | * it underwent xfrm(s). No need to subject it to the | |
472 | * unlabeled check. | |
473 | */ | |
474 | goto out; | |
475 | default: | |
476 | break; | |
477 | } | |
478 | ||
479 | /* | |
480 | * This check even when there's no association involved is | |
481 | * intended, according to Trent Jaeger, to make sure a | |
482 | * process can't engage in non-ipsec communication unless | |
483 | * explicitly allowed by policy. | |
484 | */ | |
485 | ||
486 | rc = avc_has_perm(isec_sid, SECINITSID_UNLABELED, SECCLASS_ASSOCIATION, | |
487 | ASSOCIATION__SENDTO, ad); | |
488 | out: | |
489 | return rc; | |
490 | } |