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d28d1e08 TJ |
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 | * Copyright (C) 2005 International Business Machines Corporation | |
10 | * | |
11 | * This program is free software; you can redistribute it and/or modify | |
12 | * it under the terms of the GNU General Public License version 2, | |
13 | * as published by the Free Software Foundation. | |
14 | */ | |
15 | ||
16 | /* | |
17 | * USAGE: | |
18 | * NOTES: | |
19 | * 1. Make sure to enable the following options in your kernel config: | |
20 | * CONFIG_SECURITY=y | |
21 | * CONFIG_SECURITY_NETWORK=y | |
22 | * CONFIG_SECURITY_NETWORK_XFRM=y | |
23 | * CONFIG_SECURITY_SELINUX=m/y | |
24 | * ISSUES: | |
25 | * 1. Caching packets, so they are not dropped during negotiation | |
26 | * 2. Emulating a reasonable SO_PEERSEC across machines | |
27 | * 3. Testing addition of sk_policy's with security context via setsockopt | |
28 | */ | |
29 | #include <linux/config.h> | |
30 | #include <linux/module.h> | |
31 | #include <linux/kernel.h> | |
32 | #include <linux/init.h> | |
33 | #include <linux/security.h> | |
34 | #include <linux/types.h> | |
35 | #include <linux/netfilter.h> | |
36 | #include <linux/netfilter_ipv4.h> | |
37 | #include <linux/netfilter_ipv6.h> | |
38 | #include <linux/ip.h> | |
39 | #include <linux/tcp.h> | |
40 | #include <linux/skbuff.h> | |
41 | #include <linux/xfrm.h> | |
42 | #include <net/xfrm.h> | |
43 | #include <net/checksum.h> | |
44 | #include <net/udp.h> | |
45 | #include <asm/semaphore.h> | |
46 | ||
47 | #include "avc.h" | |
48 | #include "objsec.h" | |
49 | #include "xfrm.h" | |
50 | ||
51 | ||
52 | /* | |
53 | * Returns true if an LSM/SELinux context | |
54 | */ | |
55 | static inline int selinux_authorizable_ctx(struct xfrm_sec_ctx *ctx) | |
56 | { | |
57 | return (ctx && | |
58 | (ctx->ctx_doi == XFRM_SC_DOI_LSM) && | |
59 | (ctx->ctx_alg == XFRM_SC_ALG_SELINUX)); | |
60 | } | |
61 | ||
62 | /* | |
63 | * Returns true if the xfrm contains a security blob for SELinux | |
64 | */ | |
65 | static inline int selinux_authorizable_xfrm(struct xfrm_state *x) | |
66 | { | |
67 | return selinux_authorizable_ctx(x->security); | |
68 | } | |
69 | ||
70 | /* | |
71 | * LSM hook implementation that authorizes that a socket can be used | |
72 | * with the corresponding xfrm_sec_ctx and direction. | |
73 | */ | |
74 | int selinux_xfrm_policy_lookup(struct xfrm_policy *xp, u32 sk_sid, u8 dir) | |
75 | { | |
76 | int rc = 0; | |
77 | u32 sel_sid = SECINITSID_UNLABELED; | |
78 | struct xfrm_sec_ctx *ctx; | |
79 | ||
80 | /* Context sid is either set to label or ANY_ASSOC */ | |
81 | if ((ctx = xp->security)) { | |
82 | if (!selinux_authorizable_ctx(ctx)) | |
83 | return -EINVAL; | |
84 | ||
85 | sel_sid = ctx->ctx_sid; | |
86 | } | |
87 | ||
88 | rc = avc_has_perm(sk_sid, sel_sid, SECCLASS_ASSOCIATION, | |
89 | ((dir == FLOW_DIR_IN) ? ASSOCIATION__RECVFROM : | |
90 | ((dir == FLOW_DIR_OUT) ? ASSOCIATION__SENDTO : | |
91 | (ASSOCIATION__SENDTO | ASSOCIATION__RECVFROM))), | |
92 | NULL); | |
93 | ||
94 | return rc; | |
95 | } | |
96 | ||
97 | /* | |
98 | * Security blob allocation for xfrm_policy and xfrm_state | |
99 | * CTX does not have a meaningful value on input | |
100 | */ | |
101 | static int selinux_xfrm_sec_ctx_alloc(struct xfrm_sec_ctx **ctxp, struct xfrm_user_sec_ctx *uctx) | |
102 | { | |
103 | int rc = 0; | |
104 | struct task_security_struct *tsec = current->security; | |
105 | struct xfrm_sec_ctx *ctx; | |
106 | ||
107 | BUG_ON(!uctx); | |
108 | BUG_ON(uctx->ctx_doi != XFRM_SC_ALG_SELINUX); | |
109 | ||
110 | if (uctx->ctx_len >= PAGE_SIZE) | |
111 | return -ENOMEM; | |
112 | ||
113 | *ctxp = ctx = kmalloc(sizeof(*ctx) + | |
114 | uctx->ctx_len, | |
115 | GFP_KERNEL); | |
116 | ||
117 | if (!ctx) | |
118 | return -ENOMEM; | |
119 | ||
120 | ctx->ctx_doi = uctx->ctx_doi; | |
121 | ctx->ctx_len = uctx->ctx_len; | |
122 | ctx->ctx_alg = uctx->ctx_alg; | |
123 | ||
124 | memcpy(ctx->ctx_str, | |
125 | uctx+1, | |
126 | ctx->ctx_len); | |
127 | rc = security_context_to_sid(ctx->ctx_str, | |
128 | ctx->ctx_len, | |
129 | &ctx->ctx_sid); | |
130 | ||
131 | if (rc) | |
132 | goto out; | |
133 | ||
134 | /* | |
135 | * Does the subject have permission to set security or permission to | |
136 | * do the relabel? | |
137 | * Must be permitted to relabel from default socket type (process type) | |
138 | * to specified context | |
139 | */ | |
d28d1e08 TJ |
140 | rc = avc_has_perm(tsec->sid, ctx->ctx_sid, |
141 | SECCLASS_ASSOCIATION, | |
5f8ac64b | 142 | ASSOCIATION__SETCONTEXT, NULL); |
d28d1e08 TJ |
143 | if (rc) |
144 | goto out; | |
145 | ||
146 | return rc; | |
147 | ||
148 | out: | |
ee2e6841 | 149 | *ctxp = NULL; |
d28d1e08 TJ |
150 | kfree(ctx); |
151 | return rc; | |
152 | } | |
153 | ||
154 | /* | |
155 | * LSM hook implementation that allocs and transfers uctx spec to | |
156 | * xfrm_policy. | |
157 | */ | |
158 | int selinux_xfrm_policy_alloc(struct xfrm_policy *xp, struct xfrm_user_sec_ctx *uctx) | |
159 | { | |
160 | int err; | |
161 | ||
162 | BUG_ON(!xp); | |
163 | ||
164 | err = selinux_xfrm_sec_ctx_alloc(&xp->security, uctx); | |
165 | return err; | |
166 | } | |
167 | ||
168 | ||
169 | /* | |
170 | * LSM hook implementation that copies security data structure from old to | |
171 | * new for policy cloning. | |
172 | */ | |
173 | int selinux_xfrm_policy_clone(struct xfrm_policy *old, struct xfrm_policy *new) | |
174 | { | |
175 | struct xfrm_sec_ctx *old_ctx, *new_ctx; | |
176 | ||
177 | old_ctx = old->security; | |
178 | ||
179 | if (old_ctx) { | |
180 | new_ctx = new->security = kmalloc(sizeof(*new_ctx) + | |
181 | old_ctx->ctx_len, | |
182 | GFP_KERNEL); | |
183 | ||
184 | if (!new_ctx) | |
185 | return -ENOMEM; | |
186 | ||
187 | memcpy(new_ctx, old_ctx, sizeof(*new_ctx)); | |
188 | memcpy(new_ctx->ctx_str, old_ctx->ctx_str, new_ctx->ctx_len); | |
189 | } | |
190 | return 0; | |
191 | } | |
192 | ||
193 | /* | |
194 | * LSM hook implementation that frees xfrm_policy security information. | |
195 | */ | |
196 | void selinux_xfrm_policy_free(struct xfrm_policy *xp) | |
197 | { | |
198 | struct xfrm_sec_ctx *ctx = xp->security; | |
199 | if (ctx) | |
200 | kfree(ctx); | |
201 | } | |
202 | ||
203 | /* | |
204 | * LSM hook implementation that allocs and transfers sec_ctx spec to | |
205 | * xfrm_state. | |
206 | */ | |
207 | int selinux_xfrm_state_alloc(struct xfrm_state *x, struct xfrm_user_sec_ctx *uctx) | |
208 | { | |
209 | int err; | |
210 | ||
211 | BUG_ON(!x); | |
212 | ||
213 | err = selinux_xfrm_sec_ctx_alloc(&x->security, uctx); | |
214 | return err; | |
215 | } | |
216 | ||
217 | /* | |
218 | * LSM hook implementation that frees xfrm_state security information. | |
219 | */ | |
220 | void selinux_xfrm_state_free(struct xfrm_state *x) | |
221 | { | |
222 | struct xfrm_sec_ctx *ctx = x->security; | |
223 | if (ctx) | |
224 | kfree(ctx); | |
225 | } | |
226 | ||
227 | /* | |
228 | * LSM hook that controls access to unlabelled packets. If | |
229 | * a xfrm_state is authorizable (defined by macro) then it was | |
230 | * already authorized by the IPSec process. If not, then | |
231 | * we need to check for unlabelled access since this may not have | |
232 | * gone thru the IPSec process. | |
233 | */ | |
234 | int selinux_xfrm_sock_rcv_skb(u32 isec_sid, struct sk_buff *skb) | |
235 | { | |
236 | int i, rc = 0; | |
237 | struct sec_path *sp; | |
238 | ||
239 | sp = skb->sp; | |
240 | ||
241 | if (sp) { | |
242 | /* | |
243 | * __xfrm_policy_check does not approve unless xfrm_policy_ok | |
244 | * says that spi's match for policy and the socket. | |
245 | * | |
246 | * Only need to verify the existence of an authorizable sp. | |
247 | */ | |
248 | for (i = 0; i < sp->len; i++) { | |
249 | struct xfrm_state *x = sp->x[i].xvec; | |
250 | ||
251 | if (x && selinux_authorizable_xfrm(x)) | |
252 | goto accept; | |
253 | } | |
254 | } | |
255 | ||
256 | /* check SELinux sock for unlabelled access */ | |
257 | rc = avc_has_perm(isec_sid, SECINITSID_UNLABELED, SECCLASS_ASSOCIATION, | |
258 | ASSOCIATION__RECVFROM, NULL); | |
259 | if (rc) | |
260 | goto drop; | |
261 | ||
262 | accept: | |
263 | return 0; | |
264 | ||
265 | drop: | |
266 | return rc; | |
267 | } | |
268 | ||
269 | /* | |
270 | * POSTROUTE_LAST hook's XFRM processing: | |
271 | * If we have no security association, then we need to determine | |
272 | * whether the socket is allowed to send to an unlabelled destination. | |
273 | * If we do have a authorizable security association, then it has already been | |
274 | * checked in xfrm_policy_lookup hook. | |
275 | */ | |
276 | int selinux_xfrm_postroute_last(u32 isec_sid, struct sk_buff *skb) | |
277 | { | |
278 | struct dst_entry *dst; | |
279 | int rc = 0; | |
280 | ||
281 | dst = skb->dst; | |
282 | ||
283 | if (dst) { | |
284 | struct dst_entry *dst_test; | |
285 | ||
286 | for (dst_test = dst; dst_test != 0; | |
287 | dst_test = dst_test->child) { | |
288 | struct xfrm_state *x = dst_test->xfrm; | |
289 | ||
290 | if (x && selinux_authorizable_xfrm(x)) | |
291 | goto accept; | |
292 | } | |
293 | } | |
294 | ||
295 | rc = avc_has_perm(isec_sid, SECINITSID_UNLABELED, SECCLASS_ASSOCIATION, | |
296 | ASSOCIATION__SENDTO, NULL); | |
297 | if (rc) | |
298 | goto drop; | |
299 | ||
300 | accept: | |
301 | return NF_ACCEPT; | |
302 | ||
303 | drop: | |
304 | return NF_DROP; | |
305 | } |