selinux: allow MLS->non-MLS and vice versa upon policy reload
[linux-2.6-block.git] / security / commoncap.c
CommitLineData
3e1c2515 1/* Common capabilities, needed by capability.o.
1da177e4
LT
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
c59ede7b 10#include <linux/capability.h>
3fc689e9 11#include <linux/audit.h>
1da177e4
LT
12#include <linux/module.h>
13#include <linux/init.h>
14#include <linux/kernel.h>
15#include <linux/security.h>
16#include <linux/file.h>
17#include <linux/mm.h>
18#include <linux/mman.h>
19#include <linux/pagemap.h>
20#include <linux/swap.h>
1da177e4
LT
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>
b5376771 26#include <linux/mount.h>
b460cbc5 27#include <linux/sched.h>
3898b1b4
AM
28#include <linux/prctl.h>
29#include <linux/securebits.h>
72c2d582 30
b5f22a59
SH
31/*
32 * If a non-root user executes a setuid-root binary in
33 * !secure(SECURE_NOROOT) mode, then we raise capabilities.
34 * However if fE is also set, then the intent is for only
35 * the file capabilities to be applied, and the setuid-root
36 * bit is left on either to change the uid (plausible) or
37 * to get full privilege on a kernel without file capabilities
38 * support. So in that case we do not raise capabilities.
39 *
40 * Warn if that happens, once per boot.
41 */
42static void warn_setuid_and_fcaps_mixed(char *fname)
43{
44 static int warned;
45 if (!warned) {
46 printk(KERN_INFO "warning: `%s' has both setuid-root and"
47 " effective capabilities. Therefore not raising all"
48 " capabilities.\n", fname);
49 warned = 1;
50 }
51}
52
1da177e4
LT
53int cap_netlink_send(struct sock *sk, struct sk_buff *skb)
54{
b6dff3ec 55 NETLINK_CB(skb).eff_cap = current_cap();
1da177e4
LT
56 return 0;
57}
58
c7bdb545 59int cap_netlink_recv(struct sk_buff *skb, int cap)
1da177e4 60{
c7bdb545 61 if (!cap_raised(NETLINK_CB(skb).eff_cap, cap))
1da177e4
LT
62 return -EPERM;
63 return 0;
64}
1da177e4
LT
65EXPORT_SYMBOL(cap_netlink_recv);
66
1d045980
DH
67/**
68 * cap_capable - Determine whether a task has a particular effective capability
69 * @tsk: The task to query
3699c53c 70 * @cred: The credentials to use
1d045980
DH
71 * @cap: The capability to check for
72 * @audit: Whether to write an audit message or not
73 *
74 * Determine whether the nominated task has the specified capability amongst
75 * its effective set, returning 0 if it does, -ve if it does not.
76 *
3699c53c
DH
77 * NOTE WELL: cap_has_capability() cannot be used like the kernel's capable()
78 * and has_capability() functions. That is, it has the reverse semantics:
79 * cap_has_capability() returns 0 when a task has a capability, but the
80 * kernel's capable() and has_capability() returns 1 for this case.
a6dbb1ef 81 */
3699c53c
DH
82int cap_capable(struct task_struct *tsk, const struct cred *cred, int cap,
83 int audit)
1da177e4 84{
3699c53c 85 return cap_raised(cred->cap_effective, cap) ? 0 : -EPERM;
1da177e4
LT
86}
87
1d045980
DH
88/**
89 * cap_settime - Determine whether the current process may set the system clock
90 * @ts: The time to set
91 * @tz: The timezone to set
92 *
93 * Determine whether the current process may set the system clock and timezone
94 * information, returning 0 if permission granted, -ve if denied.
95 */
1da177e4
LT
96int cap_settime(struct timespec *ts, struct timezone *tz)
97{
98 if (!capable(CAP_SYS_TIME))
99 return -EPERM;
100 return 0;
101}
102
1d045980 103/**
9e48858f 104 * cap_ptrace_access_check - Determine whether the current process may access
1d045980
DH
105 * another
106 * @child: The process to be accessed
107 * @mode: The mode of attachment.
108 *
109 * Determine whether a process may access another, returning 0 if permission
110 * granted, -ve if denied.
111 */
9e48858f 112int cap_ptrace_access_check(struct task_struct *child, unsigned int mode)
1da177e4 113{
c69e8d9c
DH
114 int ret = 0;
115
116 rcu_read_lock();
d84f4f99
DH
117 if (!cap_issubset(__task_cred(child)->cap_permitted,
118 current_cred()->cap_permitted) &&
c69e8d9c
DH
119 !capable(CAP_SYS_PTRACE))
120 ret = -EPERM;
121 rcu_read_unlock();
122 return ret;
5cd9c58f
DH
123}
124
1d045980
DH
125/**
126 * cap_ptrace_traceme - Determine whether another process may trace the current
127 * @parent: The task proposed to be the tracer
128 *
129 * Determine whether the nominated task is permitted to trace the current
130 * process, returning 0 if permission is granted, -ve if denied.
131 */
5cd9c58f
DH
132int cap_ptrace_traceme(struct task_struct *parent)
133{
c69e8d9c
DH
134 int ret = 0;
135
136 rcu_read_lock();
d84f4f99
DH
137 if (!cap_issubset(current_cred()->cap_permitted,
138 __task_cred(parent)->cap_permitted) &&
c69e8d9c
DH
139 !has_capability(parent, CAP_SYS_PTRACE))
140 ret = -EPERM;
141 rcu_read_unlock();
142 return ret;
1da177e4
LT
143}
144
1d045980
DH
145/**
146 * cap_capget - Retrieve a task's capability sets
147 * @target: The task from which to retrieve the capability sets
148 * @effective: The place to record the effective set
149 * @inheritable: The place to record the inheritable set
150 * @permitted: The place to record the permitted set
151 *
152 * This function retrieves the capabilities of the nominated task and returns
153 * them to the caller.
154 */
155int cap_capget(struct task_struct *target, kernel_cap_t *effective,
156 kernel_cap_t *inheritable, kernel_cap_t *permitted)
1da177e4 157{
c69e8d9c 158 const struct cred *cred;
b6dff3ec 159
1da177e4 160 /* Derived from kernel/capability.c:sys_capget. */
c69e8d9c
DH
161 rcu_read_lock();
162 cred = __task_cred(target);
b6dff3ec
DH
163 *effective = cred->cap_effective;
164 *inheritable = cred->cap_inheritable;
165 *permitted = cred->cap_permitted;
c69e8d9c 166 rcu_read_unlock();
1da177e4
LT
167 return 0;
168}
169
1d045980
DH
170/*
171 * Determine whether the inheritable capabilities are limited to the old
172 * permitted set. Returns 1 if they are limited, 0 if they are not.
173 */
72c2d582
AM
174static inline int cap_inh_is_capped(void)
175{
72c2d582 176
1d045980
DH
177 /* they are so limited unless the current task has the CAP_SETPCAP
178 * capability
179 */
3699c53c
DH
180 if (cap_capable(current, current_cred(), CAP_SETPCAP,
181 SECURITY_CAP_AUDIT) == 0)
1d045980 182 return 0;
1d045980 183 return 1;
1209726c 184}
72c2d582 185
1d045980
DH
186/**
187 * cap_capset - Validate and apply proposed changes to current's capabilities
188 * @new: The proposed new credentials; alterations should be made here
189 * @old: The current task's current credentials
190 * @effective: A pointer to the proposed new effective capabilities set
191 * @inheritable: A pointer to the proposed new inheritable capabilities set
192 * @permitted: A pointer to the proposed new permitted capabilities set
193 *
194 * This function validates and applies a proposed mass change to the current
195 * process's capability sets. The changes are made to the proposed new
196 * credentials, and assuming no error, will be committed by the caller of LSM.
197 */
d84f4f99
DH
198int cap_capset(struct cred *new,
199 const struct cred *old,
200 const kernel_cap_t *effective,
201 const kernel_cap_t *inheritable,
202 const kernel_cap_t *permitted)
1da177e4 203{
d84f4f99
DH
204 if (cap_inh_is_capped() &&
205 !cap_issubset(*inheritable,
206 cap_combine(old->cap_inheritable,
207 old->cap_permitted)))
72c2d582 208 /* incapable of using this inheritable set */
1da177e4 209 return -EPERM;
d84f4f99 210
3b7391de 211 if (!cap_issubset(*inheritable,
d84f4f99
DH
212 cap_combine(old->cap_inheritable,
213 old->cap_bset)))
3b7391de
SH
214 /* no new pI capabilities outside bounding set */
215 return -EPERM;
1da177e4
LT
216
217 /* verify restrictions on target's new Permitted set */
d84f4f99 218 if (!cap_issubset(*permitted, old->cap_permitted))
1da177e4 219 return -EPERM;
1da177e4
LT
220
221 /* verify the _new_Effective_ is a subset of the _new_Permitted_ */
d84f4f99 222 if (!cap_issubset(*effective, *permitted))
1da177e4 223 return -EPERM;
1da177e4 224
d84f4f99
DH
225 new->cap_effective = *effective;
226 new->cap_inheritable = *inheritable;
227 new->cap_permitted = *permitted;
1da177e4
LT
228 return 0;
229}
230
1d045980
DH
231/*
232 * Clear proposed capability sets for execve().
233 */
b5376771
SH
234static inline void bprm_clear_caps(struct linux_binprm *bprm)
235{
a6f76f23 236 cap_clear(bprm->cred->cap_permitted);
b5376771
SH
237 bprm->cap_effective = false;
238}
239
1d045980
DH
240/**
241 * cap_inode_need_killpriv - Determine if inode change affects privileges
242 * @dentry: The inode/dentry in being changed with change marked ATTR_KILL_PRIV
243 *
244 * Determine if an inode having a change applied that's marked ATTR_KILL_PRIV
245 * affects the security markings on that inode, and if it is, should
246 * inode_killpriv() be invoked or the change rejected?
247 *
248 * Returns 0 if granted; +ve if granted, but inode_killpriv() is required; and
249 * -ve to deny the change.
250 */
b5376771
SH
251int cap_inode_need_killpriv(struct dentry *dentry)
252{
253 struct inode *inode = dentry->d_inode;
254 int error;
255
acfa4380 256 if (!inode->i_op->getxattr)
b5376771
SH
257 return 0;
258
259 error = inode->i_op->getxattr(dentry, XATTR_NAME_CAPS, NULL, 0);
260 if (error <= 0)
261 return 0;
262 return 1;
263}
264
1d045980
DH
265/**
266 * cap_inode_killpriv - Erase the security markings on an inode
267 * @dentry: The inode/dentry to alter
268 *
269 * Erase the privilege-enhancing security markings on an inode.
270 *
271 * Returns 0 if successful, -ve on error.
272 */
b5376771
SH
273int cap_inode_killpriv(struct dentry *dentry)
274{
275 struct inode *inode = dentry->d_inode;
276
acfa4380 277 if (!inode->i_op->removexattr)
b5376771
SH
278 return 0;
279
280 return inode->i_op->removexattr(dentry, XATTR_NAME_CAPS);
281}
282
1d045980
DH
283/*
284 * Calculate the new process capability sets from the capability sets attached
285 * to a file.
286 */
c0b00441 287static inline int bprm_caps_from_vfs_caps(struct cpu_vfs_cap_data *caps,
a6f76f23
DH
288 struct linux_binprm *bprm,
289 bool *effective)
b5376771 290{
a6f76f23 291 struct cred *new = bprm->cred;
c0b00441
EP
292 unsigned i;
293 int ret = 0;
294
295 if (caps->magic_etc & VFS_CAP_FLAGS_EFFECTIVE)
a6f76f23 296 *effective = true;
c0b00441
EP
297
298 CAP_FOR_EACH_U32(i) {
299 __u32 permitted = caps->permitted.cap[i];
300 __u32 inheritable = caps->inheritable.cap[i];
301
302 /*
303 * pP' = (X & fP) | (pI & fI)
304 */
a6f76f23
DH
305 new->cap_permitted.cap[i] =
306 (new->cap_bset.cap[i] & permitted) |
307 (new->cap_inheritable.cap[i] & inheritable);
c0b00441 308
a6f76f23
DH
309 if (permitted & ~new->cap_permitted.cap[i])
310 /* insufficient to execute correctly */
c0b00441 311 ret = -EPERM;
c0b00441
EP
312 }
313
314 /*
315 * For legacy apps, with no internal support for recognizing they
316 * do not have enough capabilities, we return an error if they are
317 * missing some "forced" (aka file-permitted) capabilities.
318 */
a6f76f23 319 return *effective ? ret : 0;
c0b00441
EP
320}
321
1d045980
DH
322/*
323 * Extract the on-exec-apply capability sets for an executable file.
324 */
c0b00441
EP
325int get_vfs_caps_from_disk(const struct dentry *dentry, struct cpu_vfs_cap_data *cpu_caps)
326{
327 struct inode *inode = dentry->d_inode;
b5376771 328 __u32 magic_etc;
e338d263 329 unsigned tocopy, i;
c0b00441
EP
330 int size;
331 struct vfs_cap_data caps;
332
333 memset(cpu_caps, 0, sizeof(struct cpu_vfs_cap_data));
334
acfa4380 335 if (!inode || !inode->i_op->getxattr)
c0b00441
EP
336 return -ENODATA;
337
338 size = inode->i_op->getxattr((struct dentry *)dentry, XATTR_NAME_CAPS, &caps,
339 XATTR_CAPS_SZ);
a6f76f23 340 if (size == -ENODATA || size == -EOPNOTSUPP)
c0b00441
EP
341 /* no data, that's ok */
342 return -ENODATA;
c0b00441
EP
343 if (size < 0)
344 return size;
b5376771 345
e338d263 346 if (size < sizeof(magic_etc))
b5376771
SH
347 return -EINVAL;
348
c0b00441 349 cpu_caps->magic_etc = magic_etc = le32_to_cpu(caps.magic_etc);
b5376771 350
a6f76f23 351 switch (magic_etc & VFS_CAP_REVISION_MASK) {
e338d263
AM
352 case VFS_CAP_REVISION_1:
353 if (size != XATTR_CAPS_SZ_1)
354 return -EINVAL;
355 tocopy = VFS_CAP_U32_1;
356 break;
357 case VFS_CAP_REVISION_2:
358 if (size != XATTR_CAPS_SZ_2)
359 return -EINVAL;
360 tocopy = VFS_CAP_U32_2;
361 break;
b5376771
SH
362 default:
363 return -EINVAL;
364 }
e338d263 365
5459c164 366 CAP_FOR_EACH_U32(i) {
c0b00441
EP
367 if (i >= tocopy)
368 break;
369 cpu_caps->permitted.cap[i] = le32_to_cpu(caps.data[i].permitted);
370 cpu_caps->inheritable.cap[i] = le32_to_cpu(caps.data[i].inheritable);
e338d263 371 }
a6f76f23 372
c0b00441 373 return 0;
b5376771
SH
374}
375
1d045980
DH
376/*
377 * Attempt to get the on-exec apply capability sets for an executable file from
378 * its xattrs and, if present, apply them to the proposed credentials being
379 * constructed by execve().
380 */
a6f76f23 381static int get_file_caps(struct linux_binprm *bprm, bool *effective)
b5376771
SH
382{
383 struct dentry *dentry;
384 int rc = 0;
c0b00441 385 struct cpu_vfs_cap_data vcaps;
b5376771 386
3318a386
SH
387 bprm_clear_caps(bprm);
388
1f29fae2
SH
389 if (!file_caps_enabled)
390 return 0;
391
3318a386 392 if (bprm->file->f_vfsmnt->mnt_flags & MNT_NOSUID)
b5376771 393 return 0;
b5376771
SH
394
395 dentry = dget(bprm->file->f_dentry);
b5376771 396
c0b00441
EP
397 rc = get_vfs_caps_from_disk(dentry, &vcaps);
398 if (rc < 0) {
399 if (rc == -EINVAL)
400 printk(KERN_NOTICE "%s: get_vfs_caps_from_disk returned %d for %s\n",
401 __func__, rc, bprm->filename);
402 else if (rc == -ENODATA)
403 rc = 0;
b5376771
SH
404 goto out;
405 }
b5376771 406
a6f76f23
DH
407 rc = bprm_caps_from_vfs_caps(&vcaps, bprm, effective);
408 if (rc == -EINVAL)
409 printk(KERN_NOTICE "%s: cap_from_disk returned %d for %s\n",
410 __func__, rc, bprm->filename);
b5376771
SH
411
412out:
413 dput(dentry);
414 if (rc)
415 bprm_clear_caps(bprm);
416
417 return rc;
418}
419
1d045980
DH
420/**
421 * cap_bprm_set_creds - Set up the proposed credentials for execve().
422 * @bprm: The execution parameters, including the proposed creds
423 *
424 * Set up the proposed credentials for a new execution context being
425 * constructed by execve(). The proposed creds in @bprm->cred is altered,
426 * which won't take effect immediately. Returns 0 if successful, -ve on error.
a6f76f23
DH
427 */
428int cap_bprm_set_creds(struct linux_binprm *bprm)
1da177e4 429{
a6f76f23
DH
430 const struct cred *old = current_cred();
431 struct cred *new = bprm->cred;
432 bool effective;
b5376771 433 int ret;
1da177e4 434
a6f76f23
DH
435 effective = false;
436 ret = get_file_caps(bprm, &effective);
437 if (ret < 0)
438 return ret;
1da177e4 439
5459c164 440 if (!issecure(SECURE_NOROOT)) {
b5f22a59
SH
441 /*
442 * If the legacy file capability is set, then don't set privs
443 * for a setuid root binary run by a non-root user. Do set it
444 * for a root user just to cause least surprise to an admin.
445 */
446 if (effective && new->uid != 0 && new->euid == 0) {
447 warn_setuid_and_fcaps_mixed(bprm->filename);
448 goto skip;
449 }
5459c164
AM
450 /*
451 * To support inheritance of root-permissions and suid-root
452 * executables under compatibility mode, we override the
453 * capability sets for the file.
454 *
a6f76f23 455 * If only the real uid is 0, we do not set the effective bit.
5459c164 456 */
a6f76f23 457 if (new->euid == 0 || new->uid == 0) {
5459c164 458 /* pP' = (cap_bset & ~0) | (pI & ~0) */
a6f76f23
DH
459 new->cap_permitted = cap_combine(old->cap_bset,
460 old->cap_inheritable);
1da177e4 461 }
a6f76f23
DH
462 if (new->euid == 0)
463 effective = true;
1da177e4 464 }
b5f22a59 465skip:
b5376771 466
a6f76f23
DH
467 /* Don't let someone trace a set[ug]id/setpcap binary with the revised
468 * credentials unless they have the appropriate permit
469 */
470 if ((new->euid != old->uid ||
471 new->egid != old->gid ||
472 !cap_issubset(new->cap_permitted, old->cap_permitted)) &&
473 bprm->unsafe & ~LSM_UNSAFE_PTRACE_CAP) {
474 /* downgrade; they get no more than they had, and maybe less */
475 if (!capable(CAP_SETUID)) {
476 new->euid = new->uid;
477 new->egid = new->gid;
1da177e4 478 }
b3a222e5
SH
479 new->cap_permitted = cap_intersect(new->cap_permitted,
480 old->cap_permitted);
1da177e4
LT
481 }
482
a6f76f23
DH
483 new->suid = new->fsuid = new->euid;
484 new->sgid = new->fsgid = new->egid;
1da177e4 485
a6f76f23
DH
486 /* For init, we want to retain the capabilities set in the initial
487 * task. Thus we skip the usual capability rules
488 */
b460cbc5 489 if (!is_global_init(current)) {
a6f76f23
DH
490 if (effective)
491 new->cap_effective = new->cap_permitted;
e338d263 492 else
d84f4f99 493 cap_clear(new->cap_effective);
1da177e4 494 }
a6f76f23 495 bprm->cap_effective = effective;
1da177e4 496
3fc689e9
EP
497 /*
498 * Audit candidate if current->cap_effective is set
499 *
500 * We do not bother to audit if 3 things are true:
501 * 1) cap_effective has all caps
502 * 2) we are root
503 * 3) root is supposed to have all caps (SECURE_NOROOT)
504 * Since this is just a normal root execing a process.
505 *
506 * Number 1 above might fail if you don't have a full bset, but I think
507 * that is interesting information to audit.
508 */
d84f4f99
DH
509 if (!cap_isclear(new->cap_effective)) {
510 if (!cap_issubset(CAP_FULL_SET, new->cap_effective) ||
a6f76f23
DH
511 new->euid != 0 || new->uid != 0 ||
512 issecure(SECURE_NOROOT)) {
513 ret = audit_log_bprm_fcaps(bprm, new, old);
514 if (ret < 0)
515 return ret;
516 }
3fc689e9 517 }
1da177e4 518
d84f4f99 519 new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS);
a6f76f23 520 return 0;
1da177e4
LT
521}
522
1d045980
DH
523/**
524 * cap_bprm_secureexec - Determine whether a secure execution is required
525 * @bprm: The execution parameters
526 *
527 * Determine whether a secure execution is required, return 1 if it is, and 0
528 * if it is not.
529 *
530 * The credentials have been committed by this point, and so are no longer
531 * available through @bprm->cred.
a6f76f23
DH
532 */
533int cap_bprm_secureexec(struct linux_binprm *bprm)
1da177e4 534{
c69e8d9c 535 const struct cred *cred = current_cred();
b6dff3ec
DH
536
537 if (cred->uid != 0) {
b5376771
SH
538 if (bprm->cap_effective)
539 return 1;
a6f76f23 540 if (!cap_isclear(cred->cap_permitted))
b5376771
SH
541 return 1;
542 }
543
b6dff3ec
DH
544 return (cred->euid != cred->uid ||
545 cred->egid != cred->gid);
1da177e4
LT
546}
547
1d045980
DH
548/**
549 * cap_inode_setxattr - Determine whether an xattr may be altered
550 * @dentry: The inode/dentry being altered
551 * @name: The name of the xattr to be changed
552 * @value: The value that the xattr will be changed to
553 * @size: The size of value
554 * @flags: The replacement flag
555 *
556 * Determine whether an xattr may be altered or set on an inode, returning 0 if
557 * permission is granted, -ve if denied.
558 *
559 * This is used to make sure security xattrs don't get updated or set by those
560 * who aren't privileged to do so.
561 */
8f0cfa52
DH
562int cap_inode_setxattr(struct dentry *dentry, const char *name,
563 const void *value, size_t size, int flags)
1da177e4 564{
b5376771
SH
565 if (!strcmp(name, XATTR_NAME_CAPS)) {
566 if (!capable(CAP_SETFCAP))
567 return -EPERM;
568 return 0;
1d045980
DH
569 }
570
571 if (!strncmp(name, XATTR_SECURITY_PREFIX,
1da177e4
LT
572 sizeof(XATTR_SECURITY_PREFIX) - 1) &&
573 !capable(CAP_SYS_ADMIN))
574 return -EPERM;
575 return 0;
576}
577
1d045980
DH
578/**
579 * cap_inode_removexattr - Determine whether an xattr may be removed
580 * @dentry: The inode/dentry being altered
581 * @name: The name of the xattr to be changed
582 *
583 * Determine whether an xattr may be removed from an inode, returning 0 if
584 * permission is granted, -ve if denied.
585 *
586 * This is used to make sure security xattrs don't get removed by those who
587 * aren't privileged to remove them.
588 */
8f0cfa52 589int cap_inode_removexattr(struct dentry *dentry, const char *name)
1da177e4 590{
b5376771
SH
591 if (!strcmp(name, XATTR_NAME_CAPS)) {
592 if (!capable(CAP_SETFCAP))
593 return -EPERM;
594 return 0;
1d045980
DH
595 }
596
597 if (!strncmp(name, XATTR_SECURITY_PREFIX,
1da177e4
LT
598 sizeof(XATTR_SECURITY_PREFIX) - 1) &&
599 !capable(CAP_SYS_ADMIN))
600 return -EPERM;
601 return 0;
602}
603
a6f76f23 604/*
1da177e4
LT
605 * cap_emulate_setxuid() fixes the effective / permitted capabilities of
606 * a process after a call to setuid, setreuid, or setresuid.
607 *
608 * 1) When set*uiding _from_ one of {r,e,s}uid == 0 _to_ all of
609 * {r,e,s}uid != 0, the permitted and effective capabilities are
610 * cleared.
611 *
612 * 2) When set*uiding _from_ euid == 0 _to_ euid != 0, the effective
613 * capabilities of the process are cleared.
614 *
615 * 3) When set*uiding _from_ euid != 0 _to_ euid == 0, the effective
616 * capabilities are set to the permitted capabilities.
617 *
a6f76f23 618 * fsuid is handled elsewhere. fsuid == 0 and {r,e,s}uid!= 0 should
1da177e4
LT
619 * never happen.
620 *
a6f76f23 621 * -astor
1da177e4
LT
622 *
623 * cevans - New behaviour, Oct '99
624 * A process may, via prctl(), elect to keep its capabilities when it
625 * calls setuid() and switches away from uid==0. Both permitted and
626 * effective sets will be retained.
627 * Without this change, it was impossible for a daemon to drop only some
628 * of its privilege. The call to setuid(!=0) would drop all privileges!
629 * Keeping uid 0 is not an option because uid 0 owns too many vital
630 * files..
631 * Thanks to Olaf Kirch and Peter Benie for spotting this.
632 */
d84f4f99 633static inline void cap_emulate_setxuid(struct cred *new, const struct cred *old)
1da177e4 634{
d84f4f99
DH
635 if ((old->uid == 0 || old->euid == 0 || old->suid == 0) &&
636 (new->uid != 0 && new->euid != 0 && new->suid != 0) &&
3898b1b4 637 !issecure(SECURE_KEEP_CAPS)) {
d84f4f99
DH
638 cap_clear(new->cap_permitted);
639 cap_clear(new->cap_effective);
1da177e4 640 }
d84f4f99
DH
641 if (old->euid == 0 && new->euid != 0)
642 cap_clear(new->cap_effective);
643 if (old->euid != 0 && new->euid == 0)
644 new->cap_effective = new->cap_permitted;
1da177e4
LT
645}
646
1d045980
DH
647/**
648 * cap_task_fix_setuid - Fix up the results of setuid() call
649 * @new: The proposed credentials
650 * @old: The current task's current credentials
651 * @flags: Indications of what has changed
652 *
653 * Fix up the results of setuid() call before the credential changes are
654 * actually applied, returning 0 to grant the changes, -ve to deny them.
655 */
d84f4f99 656int cap_task_fix_setuid(struct cred *new, const struct cred *old, int flags)
1da177e4
LT
657{
658 switch (flags) {
659 case LSM_SETID_RE:
660 case LSM_SETID_ID:
661 case LSM_SETID_RES:
1d045980
DH
662 /* juggle the capabilities to follow [RES]UID changes unless
663 * otherwise suppressed */
d84f4f99
DH
664 if (!issecure(SECURE_NO_SETUID_FIXUP))
665 cap_emulate_setxuid(new, old);
1da177e4 666 break;
1da177e4 667
1d045980
DH
668 case LSM_SETID_FS:
669 /* juggle the capabilties to follow FSUID changes, unless
670 * otherwise suppressed
671 *
d84f4f99
DH
672 * FIXME - is fsuser used for all CAP_FS_MASK capabilities?
673 * if not, we might be a bit too harsh here.
674 */
675 if (!issecure(SECURE_NO_SETUID_FIXUP)) {
1d045980 676 if (old->fsuid == 0 && new->fsuid != 0)
d84f4f99
DH
677 new->cap_effective =
678 cap_drop_fs_set(new->cap_effective);
1d045980
DH
679
680 if (old->fsuid != 0 && new->fsuid == 0)
d84f4f99
DH
681 new->cap_effective =
682 cap_raise_fs_set(new->cap_effective,
683 new->cap_permitted);
1da177e4 684 }
d84f4f99 685 break;
1d045980 686
1da177e4
LT
687 default:
688 return -EINVAL;
689 }
690
691 return 0;
692}
693
b5376771
SH
694/*
695 * Rationale: code calling task_setscheduler, task_setioprio, and
696 * task_setnice, assumes that
697 * . if capable(cap_sys_nice), then those actions should be allowed
698 * . if not capable(cap_sys_nice), but acting on your own processes,
699 * then those actions should be allowed
700 * This is insufficient now since you can call code without suid, but
701 * yet with increased caps.
702 * So we check for increased caps on the target process.
703 */
de45e806 704static int cap_safe_nice(struct task_struct *p)
b5376771 705{
c69e8d9c
DH
706 int is_subset;
707
708 rcu_read_lock();
709 is_subset = cap_issubset(__task_cred(p)->cap_permitted,
710 current_cred()->cap_permitted);
711 rcu_read_unlock();
712
713 if (!is_subset && !capable(CAP_SYS_NICE))
b5376771
SH
714 return -EPERM;
715 return 0;
716}
717
1d045980
DH
718/**
719 * cap_task_setscheduler - Detemine if scheduler policy change is permitted
720 * @p: The task to affect
721 * @policy: The policy to effect
722 * @lp: The parameters to the scheduling policy
723 *
724 * Detemine if the requested scheduler policy change is permitted for the
725 * specified task, returning 0 if permission is granted, -ve if denied.
726 */
727int cap_task_setscheduler(struct task_struct *p, int policy,
b5376771
SH
728 struct sched_param *lp)
729{
730 return cap_safe_nice(p);
731}
732
1d045980
DH
733/**
734 * cap_task_ioprio - Detemine if I/O priority change is permitted
735 * @p: The task to affect
736 * @ioprio: The I/O priority to set
737 *
738 * Detemine if the requested I/O priority change is permitted for the specified
739 * task, returning 0 if permission is granted, -ve if denied.
740 */
741int cap_task_setioprio(struct task_struct *p, int ioprio)
b5376771
SH
742{
743 return cap_safe_nice(p);
744}
745
1d045980
DH
746/**
747 * cap_task_ioprio - Detemine if task priority change is permitted
748 * @p: The task to affect
749 * @nice: The nice value to set
750 *
751 * Detemine if the requested task priority change is permitted for the
752 * specified task, returning 0 if permission is granted, -ve if denied.
753 */
754int cap_task_setnice(struct task_struct *p, int nice)
b5376771
SH
755{
756 return cap_safe_nice(p);
757}
758
3b7391de 759/*
1d045980
DH
760 * Implement PR_CAPBSET_DROP. Attempt to remove the specified capability from
761 * the current task's bounding set. Returns 0 on success, -ve on error.
3b7391de 762 */
d84f4f99 763static long cap_prctl_drop(struct cred *new, unsigned long cap)
3b7391de
SH
764{
765 if (!capable(CAP_SETPCAP))
766 return -EPERM;
767 if (!cap_valid(cap))
768 return -EINVAL;
d84f4f99
DH
769
770 cap_lower(new->cap_bset, cap);
3b7391de
SH
771 return 0;
772}
3898b1b4 773
1d045980
DH
774/**
775 * cap_task_prctl - Implement process control functions for this security module
776 * @option: The process control function requested
777 * @arg2, @arg3, @arg4, @arg5: The argument data for this function
778 *
779 * Allow process control functions (sys_prctl()) to alter capabilities; may
780 * also deny access to other functions not otherwise implemented here.
781 *
782 * Returns 0 or +ve on success, -ENOSYS if this function is not implemented
783 * here, other -ve on error. If -ENOSYS is returned, sys_prctl() and other LSM
784 * modules will consider performing the function.
785 */
3898b1b4 786int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3,
d84f4f99 787 unsigned long arg4, unsigned long arg5)
3898b1b4 788{
d84f4f99 789 struct cred *new;
3898b1b4
AM
790 long error = 0;
791
d84f4f99
DH
792 new = prepare_creds();
793 if (!new)
794 return -ENOMEM;
795
3898b1b4
AM
796 switch (option) {
797 case PR_CAPBSET_READ:
d84f4f99 798 error = -EINVAL;
3898b1b4 799 if (!cap_valid(arg2))
d84f4f99
DH
800 goto error;
801 error = !!cap_raised(new->cap_bset, arg2);
802 goto no_change;
803
3898b1b4 804 case PR_CAPBSET_DROP:
d84f4f99
DH
805 error = cap_prctl_drop(new, arg2);
806 if (error < 0)
807 goto error;
808 goto changed;
3898b1b4
AM
809
810 /*
811 * The next four prctl's remain to assist with transitioning a
812 * system from legacy UID=0 based privilege (when filesystem
813 * capabilities are not in use) to a system using filesystem
814 * capabilities only - as the POSIX.1e draft intended.
815 *
816 * Note:
817 *
818 * PR_SET_SECUREBITS =
819 * issecure_mask(SECURE_KEEP_CAPS_LOCKED)
820 * | issecure_mask(SECURE_NOROOT)
821 * | issecure_mask(SECURE_NOROOT_LOCKED)
822 * | issecure_mask(SECURE_NO_SETUID_FIXUP)
823 * | issecure_mask(SECURE_NO_SETUID_FIXUP_LOCKED)
824 *
825 * will ensure that the current process and all of its
826 * children will be locked into a pure
827 * capability-based-privilege environment.
828 */
829 case PR_SET_SECUREBITS:
d84f4f99
DH
830 error = -EPERM;
831 if ((((new->securebits & SECURE_ALL_LOCKS) >> 1)
832 & (new->securebits ^ arg2)) /*[1]*/
833 || ((new->securebits & SECURE_ALL_LOCKS & ~arg2)) /*[2]*/
834 || (arg2 & ~(SECURE_ALL_LOCKS | SECURE_ALL_BITS)) /*[3]*/
3699c53c
DH
835 || (cap_capable(current, current_cred(), CAP_SETPCAP,
836 SECURITY_CAP_AUDIT) != 0) /*[4]*/
3898b1b4
AM
837 /*
838 * [1] no changing of bits that are locked
839 * [2] no unlocking of locks
840 * [3] no setting of unsupported bits
841 * [4] doing anything requires privilege (go read about
842 * the "sendmail capabilities bug")
843 */
d84f4f99
DH
844 )
845 /* cannot change a locked bit */
846 goto error;
847 new->securebits = arg2;
848 goto changed;
849
3898b1b4 850 case PR_GET_SECUREBITS:
d84f4f99
DH
851 error = new->securebits;
852 goto no_change;
3898b1b4 853
3898b1b4
AM
854 case PR_GET_KEEPCAPS:
855 if (issecure(SECURE_KEEP_CAPS))
856 error = 1;
d84f4f99
DH
857 goto no_change;
858
3898b1b4 859 case PR_SET_KEEPCAPS:
d84f4f99 860 error = -EINVAL;
3898b1b4 861 if (arg2 > 1) /* Note, we rely on arg2 being unsigned here */
d84f4f99
DH
862 goto error;
863 error = -EPERM;
864 if (issecure(SECURE_KEEP_CAPS_LOCKED))
865 goto error;
866 if (arg2)
867 new->securebits |= issecure_mask(SECURE_KEEP_CAPS);
3898b1b4 868 else
d84f4f99
DH
869 new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS);
870 goto changed;
3898b1b4
AM
871
872 default:
873 /* No functionality available - continue with default */
d84f4f99
DH
874 error = -ENOSYS;
875 goto error;
3898b1b4
AM
876 }
877
878 /* Functionality provided */
d84f4f99
DH
879changed:
880 return commit_creds(new);
881
882no_change:
d84f4f99
DH
883error:
884 abort_creds(new);
885 return error;
1da177e4
LT
886}
887
1d045980
DH
888/**
889 * cap_syslog - Determine whether syslog function is permitted
890 * @type: Function requested
891 *
892 * Determine whether the current process is permitted to use a particular
893 * syslog function, returning 0 if permission is granted, -ve if not.
894 */
895int cap_syslog(int type)
1da177e4
LT
896{
897 if ((type != 3 && type != 10) && !capable(CAP_SYS_ADMIN))
898 return -EPERM;
899 return 0;
900}
901
1d045980
DH
902/**
903 * cap_vm_enough_memory - Determine whether a new virtual mapping is permitted
904 * @mm: The VM space in which the new mapping is to be made
905 * @pages: The size of the mapping
906 *
907 * Determine whether the allocation of a new virtual mapping by the current
908 * task is permitted, returning 0 if permission is granted, -ve if not.
909 */
34b4e4aa 910int cap_vm_enough_memory(struct mm_struct *mm, long pages)
1da177e4
LT
911{
912 int cap_sys_admin = 0;
913
3699c53c
DH
914 if (cap_capable(current, current_cred(), CAP_SYS_ADMIN,
915 SECURITY_CAP_NOAUDIT) == 0)
1da177e4 916 cap_sys_admin = 1;
34b4e4aa 917 return __vm_enough_memory(mm, pages, cap_sys_admin);
1da177e4 918}
7c73875e
EP
919
920/*
921 * cap_file_mmap - check if able to map given addr
922 * @file: unused
923 * @reqprot: unused
924 * @prot: unused
925 * @flags: unused
926 * @addr: address attempting to be mapped
927 * @addr_only: unused
928 *
929 * If the process is attempting to map memory below mmap_min_addr they need
930 * CAP_SYS_RAWIO. The other parameters to this function are unused by the
931 * capability security module. Returns 0 if this mapping should be allowed
932 * -EPERM if not.
933 */
934int cap_file_mmap(struct file *file, unsigned long reqprot,
935 unsigned long prot, unsigned long flags,
936 unsigned long addr, unsigned long addr_only)
937{
938 int ret = 0;
939
a2551df7 940 if (addr < dac_mmap_min_addr) {
7c73875e
EP
941 ret = cap_capable(current, current_cred(), CAP_SYS_RAWIO,
942 SECURITY_CAP_AUDIT);
943 /* set PF_SUPERPRIV if it turns out we allow the low mmap */
944 if (ret == 0)
945 current->flags |= PF_SUPERPRIV;
946 }
947 return ret;
948}