projects/linux·blob v2.6.21 · refs

345 lines · 9.4 KiB

1/* Common capabilities, needed by capability.o and root_plug.o
2 *
3 * This program is free software; you can redistribute it and/or modify
4 * it under the terms of the GNU General Public License as published by
5 * the Free Software Foundation; either version 2 of the License, or
6 * (at your option) any later version.
7 *
8 */
9
10#include <linux/capability.h>
11#include <linux/module.h>
12#include <linux/init.h>
13#include <linux/kernel.h>
14#include <linux/security.h>
15#include <linux/file.h>
16#include <linux/mm.h>
17#include <linux/mman.h>
18#include <linux/pagemap.h>
19#include <linux/swap.h>
20#include <linux/smp_lock.h>
21#include <linux/skbuff.h>
22#include <linux/netlink.h>
23#include <linux/ptrace.h>
24#include <linux/xattr.h>
25#include <linux/hugetlb.h>
26
27int cap_netlink_send(struct sock *sk, struct sk_buff *skb)
28{
29 NETLINK_CB(skb).eff_cap = current->cap_effective;
30 return 0;
31}
32
33EXPORT_SYMBOL(cap_netlink_send);
34
35int cap_netlink_recv(struct sk_buff *skb, int cap)
36{
37 if (!cap_raised(NETLINK_CB(skb).eff_cap, cap))
38 return -EPERM;
39 return 0;
40}
41
42EXPORT_SYMBOL(cap_netlink_recv);
43
44int cap_capable (struct task_struct *tsk, int cap)
45{
46 /* Derived from include/linux/sched.h:capable. */
47 if (cap_raised(tsk->cap_effective, cap))
48 return 0;
49 return -EPERM;
50}
51
52int cap_settime(struct timespec *ts, struct timezone *tz)
53{
54 if (!capable(CAP_SYS_TIME))
55 return -EPERM;
56 return 0;
57}
58
59int cap_ptrace (struct task_struct *parent, struct task_struct *child)
60{
61 /* Derived from arch/i386/kernel/ptrace.c:sys_ptrace. */
62 if (!cap_issubset(child->cap_permitted, parent->cap_permitted) &&
63 !__capable(parent, CAP_SYS_PTRACE))
64 return -EPERM;
65 return 0;
66}
67
68int cap_capget (struct task_struct *target, kernel_cap_t *effective,
69 kernel_cap_t *inheritable, kernel_cap_t *permitted)
70{
71 /* Derived from kernel/capability.c:sys_capget. */
72 *effective = cap_t (target->cap_effective);
73 *inheritable = cap_t (target->cap_inheritable);
74 *permitted = cap_t (target->cap_permitted);
75 return 0;
76}
77
78int cap_capset_check (struct task_struct *target, kernel_cap_t *effective,
79 kernel_cap_t *inheritable, kernel_cap_t *permitted)
80{
81 /* Derived from kernel/capability.c:sys_capset. */
82 /* verify restrictions on target's new Inheritable set */
83 if (!cap_issubset (*inheritable,
84 cap_combine (target->cap_inheritable,
85 current->cap_permitted))) {
86 return -EPERM;
87 }
88
89 /* verify restrictions on target's new Permitted set */
90 if (!cap_issubset (*permitted,
91 cap_combine (target->cap_permitted,
92 current->cap_permitted))) {
93 return -EPERM;
94 }
95
96 /* verify the _new_Effective_ is a subset of the _new_Permitted_ */
97 if (!cap_issubset (*effective, *permitted)) {
98 return -EPERM;
99 }
100
101 return 0;
102}
103
104void cap_capset_set (struct task_struct *target, kernel_cap_t *effective,
105 kernel_cap_t *inheritable, kernel_cap_t *permitted)
106{
107 target->cap_effective = *effective;
108 target->cap_inheritable = *inheritable;
109 target->cap_permitted = *permitted;
110}
111
112int cap_bprm_set_security (struct linux_binprm *bprm)
113{
114 /* Copied from fs/exec.c:prepare_binprm. */
115
116 /* We don't have VFS support for capabilities yet */
117 cap_clear (bprm->cap_inheritable);
118 cap_clear (bprm->cap_permitted);
119 cap_clear (bprm->cap_effective);
120
121 /* To support inheritance of root-permissions and suid-root
122 * executables under compatibility mode, we raise all three
123 * capability sets for the file.
124 *
125 * If only the real uid is 0, we only raise the inheritable
126 * and permitted sets of the executable file.
127 */
128
129 if (!issecure (SECURE_NOROOT)) {
130 if (bprm->e_uid == 0 || current->uid == 0) {
131 cap_set_full (bprm->cap_inheritable);
132 cap_set_full (bprm->cap_permitted);
133 }
134 if (bprm->e_uid == 0)
135 cap_set_full (bprm->cap_effective);
136 }
137 return 0;
138}
139
140void cap_bprm_apply_creds (struct linux_binprm *bprm, int unsafe)
141{
142 /* Derived from fs/exec.c:compute_creds. */
143 kernel_cap_t new_permitted, working;
144
145 new_permitted = cap_intersect (bprm->cap_permitted, cap_bset);
146 working = cap_intersect (bprm->cap_inheritable,
147 current->cap_inheritable);
148 new_permitted = cap_combine (new_permitted, working);
149
150 if (bprm->e_uid != current->uid || bprm->e_gid != current->gid ||
151 !cap_issubset (new_permitted, current->cap_permitted)) {
152 current->mm->dumpable = suid_dumpable;
153
154 if (unsafe & ~LSM_UNSAFE_PTRACE_CAP) {
155 if (!capable(CAP_SETUID)) {
156 bprm->e_uid = current->uid;
157 bprm->e_gid = current->gid;
158 }
159 if (!capable (CAP_SETPCAP)) {
160 new_permitted = cap_intersect (new_permitted,
161 current->cap_permitted);
162 }
163 }
164 }
165
166 current->suid = current->euid = current->fsuid = bprm->e_uid;
167 current->sgid = current->egid = current->fsgid = bprm->e_gid;
168
169 /* For init, we want to retain the capabilities set
170 * in the init_task struct. Thus we skip the usual
171 * capability rules */
172 if (!is_init(current)) {
173 current->cap_permitted = new_permitted;
174 current->cap_effective =
175 cap_intersect (new_permitted, bprm->cap_effective);
176 }
177
178 /* AUD: Audit candidate if current->cap_effective is set */
179
180 current->keep_capabilities = 0;
181}
182
183int cap_bprm_secureexec (struct linux_binprm *bprm)
184{
185 /* If/when this module is enhanced to incorporate capability
186 bits on files, the test below should be extended to also perform a
187 test between the old and new capability sets. For now,
188 it simply preserves the legacy decision algorithm used by
189 the old userland. */
190 return (current->euid != current->uid ||
191 current->egid != current->gid);
192}
193
194int cap_inode_setxattr(struct dentry *dentry, char *name, void *value,
195 size_t size, int flags)
196{
197 if (!strncmp(name, XATTR_SECURITY_PREFIX,
198 sizeof(XATTR_SECURITY_PREFIX) - 1) &&
199 !capable(CAP_SYS_ADMIN))
200 return -EPERM;
201 return 0;
202}
203
204int cap_inode_removexattr(struct dentry *dentry, char *name)
205{
206 if (!strncmp(name, XATTR_SECURITY_PREFIX,
207 sizeof(XATTR_SECURITY_PREFIX) - 1) &&
208 !capable(CAP_SYS_ADMIN))
209 return -EPERM;
210 return 0;
211}
212
213/* moved from kernel/sys.c. */
214/*
215 * cap_emulate_setxuid() fixes the effective / permitted capabilities of
216 * a process after a call to setuid, setreuid, or setresuid.
217 *
218 * 1) When set*uiding _from_ one of {r,e,s}uid == 0 _to_ all of
219 * {r,e,s}uid != 0, the permitted and effective capabilities are
220 * cleared.
221 *
222 * 2) When set*uiding _from_ euid == 0 _to_ euid != 0, the effective
223 * capabilities of the process are cleared.
224 *
225 * 3) When set*uiding _from_ euid != 0 _to_ euid == 0, the effective
226 * capabilities are set to the permitted capabilities.
227 *
228 * fsuid is handled elsewhere. fsuid == 0 and {r,e,s}uid!= 0 should
229 * never happen.
230 *
231 * -astor
232 *
233 * cevans - New behaviour, Oct '99
234 * A process may, via prctl(), elect to keep its capabilities when it
235 * calls setuid() and switches away from uid==0. Both permitted and
236 * effective sets will be retained.
237 * Without this change, it was impossible for a daemon to drop only some
238 * of its privilege. The call to setuid(!=0) would drop all privileges!
239 * Keeping uid 0 is not an option because uid 0 owns too many vital
240 * files..
241 * Thanks to Olaf Kirch and Peter Benie for spotting this.
242 */
243static inline void cap_emulate_setxuid (int old_ruid, int old_euid,
244 int old_suid)
245{
246 if ((old_ruid == 0 || old_euid == 0 || old_suid == 0) &&
247 (current->uid != 0 && current->euid != 0 && current->suid != 0) &&
248 !current->keep_capabilities) {
249 cap_clear (current->cap_permitted);
250 cap_clear (current->cap_effective);
251 }
252 if (old_euid == 0 && current->euid != 0) {
253 cap_clear (current->cap_effective);
254 }
255 if (old_euid != 0 && current->euid == 0) {
256 current->cap_effective = current->cap_permitted;
257 }
258}
259
260int cap_task_post_setuid (uid_t old_ruid, uid_t old_euid, uid_t old_suid,
261 int flags)
262{
263 switch (flags) {
264 case LSM_SETID_RE:
265 case LSM_SETID_ID:
266 case LSM_SETID_RES:
267 /* Copied from kernel/sys.c:setreuid/setuid/setresuid. */
268 if (!issecure (SECURE_NO_SETUID_FIXUP)) {
269 cap_emulate_setxuid (old_ruid, old_euid, old_suid);
270 }
271 break;
272 case LSM_SETID_FS:
273 {
274 uid_t old_fsuid = old_ruid;
275
276 /* Copied from kernel/sys.c:setfsuid. */
277
278 /*
279 * FIXME - is fsuser used for all CAP_FS_MASK capabilities?
280 * if not, we might be a bit too harsh here.
281 */
282
283 if (!issecure (SECURE_NO_SETUID_FIXUP)) {
284 if (old_fsuid == 0 && current->fsuid != 0) {
285 cap_t (current->cap_effective) &=
286 ~CAP_FS_MASK;
287 }
288 if (old_fsuid != 0 && current->fsuid == 0) {
289 cap_t (current->cap_effective) |=
290 (cap_t (current->cap_permitted) &
291 CAP_FS_MASK);
292 }
293 }
294 break;
295 }
296 default:
297 return -EINVAL;
298 }
299
300 return 0;
301}
302
303void cap_task_reparent_to_init (struct task_struct *p)
304{
305 p->cap_effective = CAP_INIT_EFF_SET;
306 p->cap_inheritable = CAP_INIT_INH_SET;
307 p->cap_permitted = CAP_FULL_SET;
308 p->keep_capabilities = 0;
309 return;
310}
311
312int cap_syslog (int type)
313{
314 if ((type != 3 && type != 10) && !capable(CAP_SYS_ADMIN))
315 return -EPERM;
316 return 0;
317}
318
319int cap_vm_enough_memory(long pages)
320{
321 int cap_sys_admin = 0;
322
323 if (cap_capable(current, CAP_SYS_ADMIN) == 0)
324 cap_sys_admin = 1;
325 return __vm_enough_memory(pages, cap_sys_admin);
326}
327
328EXPORT_SYMBOL(cap_capable);
329EXPORT_SYMBOL(cap_settime);
330EXPORT_SYMBOL(cap_ptrace);
331EXPORT_SYMBOL(cap_capget);
332EXPORT_SYMBOL(cap_capset_check);
333EXPORT_SYMBOL(cap_capset_set);
334EXPORT_SYMBOL(cap_bprm_set_security);
335EXPORT_SYMBOL(cap_bprm_apply_creds);
336EXPORT_SYMBOL(cap_bprm_secureexec);
337EXPORT_SYMBOL(cap_inode_setxattr);
338EXPORT_SYMBOL(cap_inode_removexattr);
339EXPORT_SYMBOL(cap_task_post_setuid);
340EXPORT_SYMBOL(cap_task_reparent_to_init);
341EXPORT_SYMBOL(cap_syslog);
342EXPORT_SYMBOL(cap_vm_enough_memory);
343
344MODULE_DESCRIPTION("Standard Linux Common Capabilities Security Module");
345MODULE_LICENSE("GPL");