2 * NSA Security-Enhanced Linux (SELinux) security module
4 * This file contains the SELinux XFRM hook function implementations.
6 * Authors: Serge Hallyn <sergeh@us.ibm.com>
7 * Trent Jaeger <jaegert@us.ibm.com>
9 * Updated: Venkat Yekkirala <vyekkirala@TrustedCS.com>
11 * Granular IPSec Associations for use in MLS environments.
13 * Copyright (C) 2005 International Business Machines Corporation
14 * Copyright (C) 2006 Trusted Computer Solutions, Inc.
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.
24 * 1. Make sure to enable the following options in your kernel config:
26 * CONFIG_SECURITY_NETWORK=y
27 * CONFIG_SECURITY_NETWORK_XFRM=y
28 * CONFIG_SECURITY_SELINUX=m/y
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
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>
43 #include <linux/tcp.h>
44 #include <linux/skbuff.h>
45 #include <linux/xfrm.h>
47 #include <net/checksum.h>
49 #include <linux/atomic.h>
55 /* Labeled XFRM instance counter */
56 atomic_t selinux_xfrm_refcount = ATOMIC_INIT(0);
59 * Returns true if the context is an LSM/SELinux context.
61 static inline int selinux_authorizable_ctx(struct xfrm_sec_ctx *ctx)
64 (ctx->ctx_doi == XFRM_SC_DOI_LSM) &&
65 (ctx->ctx_alg == XFRM_SC_ALG_SELINUX));
69 * Returns true if the xfrm contains a security blob for SELinux.
71 static inline int selinux_authorizable_xfrm(struct xfrm_state *x)
73 return selinux_authorizable_ctx(x->security);
77 * Allocates a xfrm_sec_state and populates it using the supplied security
78 * xfrm_user_sec_ctx context.
80 static int selinux_xfrm_alloc_user(struct xfrm_sec_ctx **ctxp,
81 struct xfrm_user_sec_ctx *uctx)
84 const struct task_security_struct *tsec = current_security();
85 struct xfrm_sec_ctx *ctx = NULL;
88 if (ctxp == NULL || uctx == NULL ||
89 uctx->ctx_doi != XFRM_SC_DOI_LSM ||
90 uctx->ctx_alg != XFRM_SC_ALG_SELINUX)
93 str_len = uctx->ctx_len;
94 if (str_len >= PAGE_SIZE)
97 ctx = kmalloc(sizeof(*ctx) + str_len + 1, GFP_KERNEL);
101 ctx->ctx_doi = XFRM_SC_DOI_LSM;
102 ctx->ctx_alg = XFRM_SC_ALG_SELINUX;
103 ctx->ctx_len = str_len;
104 memcpy(ctx->ctx_str, &uctx[1], str_len);
105 ctx->ctx_str[str_len] = '\0';
106 rc = security_context_to_sid(ctx->ctx_str, str_len, &ctx->ctx_sid);
110 rc = avc_has_perm(tsec->sid, ctx->ctx_sid,
111 SECCLASS_ASSOCIATION, ASSOCIATION__SETCONTEXT, NULL);
116 atomic_inc(&selinux_xfrm_refcount);
125 * Free the xfrm_sec_ctx structure.
127 static void selinux_xfrm_free(struct xfrm_sec_ctx *ctx)
132 atomic_dec(&selinux_xfrm_refcount);
137 * Authorize the deletion of a labeled SA or policy rule.
139 static int selinux_xfrm_delete(struct xfrm_sec_ctx *ctx)
141 const struct task_security_struct *tsec = current_security();
146 return avc_has_perm(tsec->sid, ctx->ctx_sid,
147 SECCLASS_ASSOCIATION, ASSOCIATION__SETCONTEXT,
152 * LSM hook implementation that authorizes that a flow can use a xfrm policy
155 int selinux_xfrm_policy_lookup(struct xfrm_sec_ctx *ctx, u32 fl_secid, u8 dir)
159 /* All flows should be treated as polmatch'ing an otherwise applicable
160 * "non-labeled" policy. This would prevent inadvertent "leaks". */
164 /* Context sid is either set to label or ANY_ASSOC */
165 if (!selinux_authorizable_ctx(ctx))
168 rc = avc_has_perm(fl_secid, ctx->ctx_sid,
169 SECCLASS_ASSOCIATION, ASSOCIATION__POLMATCH, NULL);
170 return (rc == -EACCES ? -ESRCH : rc);
174 * LSM hook implementation that authorizes that a state matches
175 * the given policy, flow combo.
177 int selinux_xfrm_state_pol_flow_match(struct xfrm_state *x,
178 struct xfrm_policy *xp,
179 const struct flowi *fl)
185 /* unlabeled policy and labeled SA can't match */
188 /* unlabeled policy and unlabeled SA match all flows */
192 /* unlabeled SA and labeled policy can't match */
195 if (!selinux_authorizable_xfrm(x))
196 /* Not a SELinux-labeled SA */
199 state_sid = x->security->ctx_sid;
201 if (fl->flowi_secid != state_sid)
204 /* We don't need a separate SA Vs. policy polmatch check since the SA
205 * is now of the same label as the flow and a flow Vs. policy polmatch
206 * check had already happened in selinux_xfrm_policy_lookup() above. */
207 return (avc_has_perm(fl->flowi_secid, state_sid,
208 SECCLASS_ASSOCIATION, ASSOCIATION__SENDTO,
213 * LSM hook implementation that checks and/or returns the xfrm sid for the
216 int selinux_xfrm_decode_session(struct sk_buff *skb, u32 *sid, int ckall)
218 u32 sid_session = SECSID_NULL;
228 for (i = sp->len - 1; i >= 0; i--) {
229 struct xfrm_state *x = sp->xvec[i];
230 if (selinux_authorizable_xfrm(x)) {
231 struct xfrm_sec_ctx *ctx = x->security;
233 if (sid_session == SECSID_NULL) {
234 sid_session = ctx->ctx_sid;
237 } else if (sid_session != ctx->ctx_sid) {
251 * LSM hook implementation that allocs and transfers uctx spec to xfrm_policy.
253 int selinux_xfrm_policy_alloc(struct xfrm_sec_ctx **ctxp,
254 struct xfrm_user_sec_ctx *uctx)
256 return selinux_xfrm_alloc_user(ctxp, uctx);
260 * LSM hook implementation that copies security data structure from old to new
261 * for policy cloning.
263 int selinux_xfrm_policy_clone(struct xfrm_sec_ctx *old_ctx,
264 struct xfrm_sec_ctx **new_ctxp)
266 struct xfrm_sec_ctx *new_ctx;
271 new_ctx = kmemdup(old_ctx, sizeof(*old_ctx) + old_ctx->ctx_len,
275 atomic_inc(&selinux_xfrm_refcount);
282 * LSM hook implementation that frees xfrm_sec_ctx security information.
284 void selinux_xfrm_policy_free(struct xfrm_sec_ctx *ctx)
286 selinux_xfrm_free(ctx);
290 * LSM hook implementation that authorizes deletion of labeled policies.
292 int selinux_xfrm_policy_delete(struct xfrm_sec_ctx *ctx)
294 return selinux_xfrm_delete(ctx);
298 * LSM hook implementation that allocates a xfrm_sec_state, populates it using
299 * the supplied security context, and assigns it to the xfrm_state.
301 int selinux_xfrm_state_alloc(struct xfrm_state *x,
302 struct xfrm_user_sec_ctx *uctx)
304 return selinux_xfrm_alloc_user(&x->security, uctx);
308 * LSM hook implementation that allocates a xfrm_sec_state and populates based
311 int selinux_xfrm_state_alloc_acquire(struct xfrm_state *x,
312 struct xfrm_sec_ctx *polsec, u32 secid)
315 struct xfrm_sec_ctx *ctx;
316 char *ctx_str = NULL;
325 rc = security_sid_to_context(secid, &ctx_str, &str_len);
329 ctx = kmalloc(sizeof(*ctx) + str_len, GFP_ATOMIC);
333 ctx->ctx_doi = XFRM_SC_DOI_LSM;
334 ctx->ctx_alg = XFRM_SC_ALG_SELINUX;
335 ctx->ctx_sid = secid;
336 ctx->ctx_len = str_len;
337 memcpy(ctx->ctx_str, ctx_str, str_len);
341 atomic_inc(&selinux_xfrm_refcount);
346 * LSM hook implementation that frees xfrm_state security information.
348 void selinux_xfrm_state_free(struct xfrm_state *x)
350 selinux_xfrm_free(x->security);
354 * LSM hook implementation that authorizes deletion of labeled SAs.
356 int selinux_xfrm_state_delete(struct xfrm_state *x)
358 return selinux_xfrm_delete(x->security);
362 * LSM hook that controls access to unlabelled packets. If
363 * a xfrm_state is authorizable (defined by macro) then it was
364 * already authorized by the IPSec process. If not, then
365 * we need to check for unlabelled access since this may not have
366 * gone thru the IPSec process.
368 int selinux_xfrm_sock_rcv_skb(u32 sk_sid, struct sk_buff *skb,
369 struct common_audit_data *ad)
372 struct sec_path *sp = skb->sp;
373 u32 peer_sid = SECINITSID_UNLABELED;
376 for (i = 0; i < sp->len; i++) {
377 struct xfrm_state *x = sp->xvec[i];
379 if (x && selinux_authorizable_xfrm(x)) {
380 struct xfrm_sec_ctx *ctx = x->security;
381 peer_sid = ctx->ctx_sid;
387 /* This check even when there's no association involved is intended,
388 * according to Trent Jaeger, to make sure a process can't engage in
389 * non-IPsec communication unless explicitly allowed by policy. */
390 return avc_has_perm(sk_sid, peer_sid,
391 SECCLASS_ASSOCIATION, ASSOCIATION__RECVFROM, ad);
395 * POSTROUTE_LAST hook's XFRM processing:
396 * If we have no security association, then we need to determine
397 * whether the socket is allowed to send to an unlabelled destination.
398 * If we do have a authorizable security association, then it has already been
399 * checked in the selinux_xfrm_state_pol_flow_match hook above.
401 int selinux_xfrm_postroute_last(u32 sk_sid, struct sk_buff *skb,
402 struct common_audit_data *ad, u8 proto)
404 struct dst_entry *dst;
410 /* We should have already seen this packet once before it
411 * underwent xfrm(s). No need to subject it to the unlabeled
420 struct dst_entry *iter;
422 for (iter = dst; iter != NULL; iter = iter->child) {
423 struct xfrm_state *x = iter->xfrm;
425 if (x && selinux_authorizable_xfrm(x))
430 /* This check even when there's no association involved is intended,
431 * according to Trent Jaeger, to make sure a process can't engage in
432 * non-IPsec communication unless explicitly allowed by policy. */
433 return avc_has_perm(sk_sid, SECINITSID_UNLABELED,
434 SECCLASS_ASSOCIATION, ASSOCIATION__SENDTO, ad);