ntfs: don't NULL i_op
[linux-2.6-block.git] / security / commoncap.c
CommitLineData
e338d263 1/* Common capabilities, needed by capability.o and root_plug.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
1da177e4
LT
31int cap_netlink_send(struct sock *sk, struct sk_buff *skb)
32{
b6dff3ec 33 NETLINK_CB(skb).eff_cap = current_cap();
1da177e4
LT
34 return 0;
35}
36
c7bdb545 37int cap_netlink_recv(struct sk_buff *skb, int cap)
1da177e4 38{
c7bdb545 39 if (!cap_raised(NETLINK_CB(skb).eff_cap, cap))
1da177e4
LT
40 return -EPERM;
41 return 0;
42}
1da177e4
LT
43EXPORT_SYMBOL(cap_netlink_recv);
44
1d045980
DH
45/**
46 * cap_capable - Determine whether a task has a particular effective capability
47 * @tsk: The task to query
48 * @cap: The capability to check for
49 * @audit: Whether to write an audit message or not
50 *
51 * Determine whether the nominated task has the specified capability amongst
52 * its effective set, returning 0 if it does, -ve if it does not.
53 *
a6dbb1ef 54 * NOTE WELL: cap_capable() cannot be used like the kernel's capable()
1d045980
DH
55 * function. That is, it has the reverse semantics: cap_capable() returns 0
56 * when a task has a capability, but the kernel's capable() returns 1 for this
57 * case.
a6dbb1ef 58 */
06112163 59int cap_capable(struct task_struct *tsk, int cap, int audit)
1da177e4 60{
c69e8d9c
DH
61 __u32 cap_raised;
62
1da177e4 63 /* Derived from include/linux/sched.h:capable. */
c69e8d9c
DH
64 rcu_read_lock();
65 cap_raised = cap_raised(__task_cred(tsk)->cap_effective, cap);
66 rcu_read_unlock();
67 return cap_raised ? 0 : -EPERM;
1da177e4
LT
68}
69
1d045980
DH
70/**
71 * cap_settime - Determine whether the current process may set the system clock
72 * @ts: The time to set
73 * @tz: The timezone to set
74 *
75 * Determine whether the current process may set the system clock and timezone
76 * information, returning 0 if permission granted, -ve if denied.
77 */
1da177e4
LT
78int cap_settime(struct timespec *ts, struct timezone *tz)
79{
80 if (!capable(CAP_SYS_TIME))
81 return -EPERM;
82 return 0;
83}
84
1d045980
DH
85/**
86 * cap_ptrace_may_access - Determine whether the current process may access
87 * another
88 * @child: The process to be accessed
89 * @mode: The mode of attachment.
90 *
91 * Determine whether a process may access another, returning 0 if permission
92 * granted, -ve if denied.
93 */
5cd9c58f 94int cap_ptrace_may_access(struct task_struct *child, unsigned int mode)
1da177e4 95{
c69e8d9c
DH
96 int ret = 0;
97
98 rcu_read_lock();
d84f4f99
DH
99 if (!cap_issubset(__task_cred(child)->cap_permitted,
100 current_cred()->cap_permitted) &&
c69e8d9c
DH
101 !capable(CAP_SYS_PTRACE))
102 ret = -EPERM;
103 rcu_read_unlock();
104 return ret;
5cd9c58f
DH
105}
106
1d045980
DH
107/**
108 * cap_ptrace_traceme - Determine whether another process may trace the current
109 * @parent: The task proposed to be the tracer
110 *
111 * Determine whether the nominated task is permitted to trace the current
112 * process, returning 0 if permission is granted, -ve if denied.
113 */
5cd9c58f
DH
114int cap_ptrace_traceme(struct task_struct *parent)
115{
c69e8d9c
DH
116 int ret = 0;
117
118 rcu_read_lock();
d84f4f99
DH
119 if (!cap_issubset(current_cred()->cap_permitted,
120 __task_cred(parent)->cap_permitted) &&
c69e8d9c
DH
121 !has_capability(parent, CAP_SYS_PTRACE))
122 ret = -EPERM;
123 rcu_read_unlock();
124 return ret;
1da177e4
LT
125}
126
1d045980
DH
127/**
128 * cap_capget - Retrieve a task's capability sets
129 * @target: The task from which to retrieve the capability sets
130 * @effective: The place to record the effective set
131 * @inheritable: The place to record the inheritable set
132 * @permitted: The place to record the permitted set
133 *
134 * This function retrieves the capabilities of the nominated task and returns
135 * them to the caller.
136 */
137int cap_capget(struct task_struct *target, kernel_cap_t *effective,
138 kernel_cap_t *inheritable, kernel_cap_t *permitted)
1da177e4 139{
c69e8d9c 140 const struct cred *cred;
b6dff3ec 141
1da177e4 142 /* Derived from kernel/capability.c:sys_capget. */
c69e8d9c
DH
143 rcu_read_lock();
144 cred = __task_cred(target);
b6dff3ec
DH
145 *effective = cred->cap_effective;
146 *inheritable = cred->cap_inheritable;
147 *permitted = cred->cap_permitted;
c69e8d9c 148 rcu_read_unlock();
1da177e4
LT
149 return 0;
150}
151
1d045980
DH
152/*
153 * Determine whether the inheritable capabilities are limited to the old
154 * permitted set. Returns 1 if they are limited, 0 if they are not.
155 */
72c2d582
AM
156static inline int cap_inh_is_capped(void)
157{
1d045980 158#ifdef CONFIG_SECURITY_FILE_CAPABILITIES
72c2d582 159
1d045980
DH
160 /* they are so limited unless the current task has the CAP_SETPCAP
161 * capability
162 */
163 if (cap_capable(current, CAP_SETPCAP, SECURITY_CAP_AUDIT) == 0)
164 return 0;
165#endif
166 return 1;
1209726c 167}
72c2d582 168
1d045980
DH
169/**
170 * cap_capset - Validate and apply proposed changes to current's capabilities
171 * @new: The proposed new credentials; alterations should be made here
172 * @old: The current task's current credentials
173 * @effective: A pointer to the proposed new effective capabilities set
174 * @inheritable: A pointer to the proposed new inheritable capabilities set
175 * @permitted: A pointer to the proposed new permitted capabilities set
176 *
177 * This function validates and applies a proposed mass change to the current
178 * process's capability sets. The changes are made to the proposed new
179 * credentials, and assuming no error, will be committed by the caller of LSM.
180 */
d84f4f99
DH
181int cap_capset(struct cred *new,
182 const struct cred *old,
183 const kernel_cap_t *effective,
184 const kernel_cap_t *inheritable,
185 const kernel_cap_t *permitted)
1da177e4 186{
d84f4f99
DH
187 if (cap_inh_is_capped() &&
188 !cap_issubset(*inheritable,
189 cap_combine(old->cap_inheritable,
190 old->cap_permitted)))
72c2d582 191 /* incapable of using this inheritable set */
1da177e4 192 return -EPERM;
d84f4f99 193
3b7391de 194 if (!cap_issubset(*inheritable,
d84f4f99
DH
195 cap_combine(old->cap_inheritable,
196 old->cap_bset)))
3b7391de
SH
197 /* no new pI capabilities outside bounding set */
198 return -EPERM;
1da177e4
LT
199
200 /* verify restrictions on target's new Permitted set */
d84f4f99 201 if (!cap_issubset(*permitted, old->cap_permitted))
1da177e4 202 return -EPERM;
1da177e4
LT
203
204 /* verify the _new_Effective_ is a subset of the _new_Permitted_ */
d84f4f99 205 if (!cap_issubset(*effective, *permitted))
1da177e4 206 return -EPERM;
1da177e4 207
d84f4f99
DH
208 new->cap_effective = *effective;
209 new->cap_inheritable = *inheritable;
210 new->cap_permitted = *permitted;
1da177e4
LT
211 return 0;
212}
213
1d045980
DH
214/*
215 * Clear proposed capability sets for execve().
216 */
b5376771
SH
217static inline void bprm_clear_caps(struct linux_binprm *bprm)
218{
a6f76f23 219 cap_clear(bprm->cred->cap_permitted);
b5376771
SH
220 bprm->cap_effective = false;
221}
222
223#ifdef CONFIG_SECURITY_FILE_CAPABILITIES
224
1d045980
DH
225/**
226 * cap_inode_need_killpriv - Determine if inode change affects privileges
227 * @dentry: The inode/dentry in being changed with change marked ATTR_KILL_PRIV
228 *
229 * Determine if an inode having a change applied that's marked ATTR_KILL_PRIV
230 * affects the security markings on that inode, and if it is, should
231 * inode_killpriv() be invoked or the change rejected?
232 *
233 * Returns 0 if granted; +ve if granted, but inode_killpriv() is required; and
234 * -ve to deny the change.
235 */
b5376771
SH
236int cap_inode_need_killpriv(struct dentry *dentry)
237{
238 struct inode *inode = dentry->d_inode;
239 int error;
240
241 if (!inode->i_op || !inode->i_op->getxattr)
242 return 0;
243
244 error = inode->i_op->getxattr(dentry, XATTR_NAME_CAPS, NULL, 0);
245 if (error <= 0)
246 return 0;
247 return 1;
248}
249
1d045980
DH
250/**
251 * cap_inode_killpriv - Erase the security markings on an inode
252 * @dentry: The inode/dentry to alter
253 *
254 * Erase the privilege-enhancing security markings on an inode.
255 *
256 * Returns 0 if successful, -ve on error.
257 */
b5376771
SH
258int cap_inode_killpriv(struct dentry *dentry)
259{
260 struct inode *inode = dentry->d_inode;
261
262 if (!inode->i_op || !inode->i_op->removexattr)
263 return 0;
264
265 return inode->i_op->removexattr(dentry, XATTR_NAME_CAPS);
266}
267
1d045980
DH
268/*
269 * Calculate the new process capability sets from the capability sets attached
270 * to a file.
271 */
c0b00441 272static inline int bprm_caps_from_vfs_caps(struct cpu_vfs_cap_data *caps,
a6f76f23
DH
273 struct linux_binprm *bprm,
274 bool *effective)
b5376771 275{
a6f76f23 276 struct cred *new = bprm->cred;
c0b00441
EP
277 unsigned i;
278 int ret = 0;
279
280 if (caps->magic_etc & VFS_CAP_FLAGS_EFFECTIVE)
a6f76f23 281 *effective = true;
c0b00441
EP
282
283 CAP_FOR_EACH_U32(i) {
284 __u32 permitted = caps->permitted.cap[i];
285 __u32 inheritable = caps->inheritable.cap[i];
286
287 /*
288 * pP' = (X & fP) | (pI & fI)
289 */
a6f76f23
DH
290 new->cap_permitted.cap[i] =
291 (new->cap_bset.cap[i] & permitted) |
292 (new->cap_inheritable.cap[i] & inheritable);
c0b00441 293
a6f76f23
DH
294 if (permitted & ~new->cap_permitted.cap[i])
295 /* insufficient to execute correctly */
c0b00441 296 ret = -EPERM;
c0b00441
EP
297 }
298
299 /*
300 * For legacy apps, with no internal support for recognizing they
301 * do not have enough capabilities, we return an error if they are
302 * missing some "forced" (aka file-permitted) capabilities.
303 */
a6f76f23 304 return *effective ? ret : 0;
c0b00441
EP
305}
306
1d045980
DH
307/*
308 * Extract the on-exec-apply capability sets for an executable file.
309 */
c0b00441
EP
310int get_vfs_caps_from_disk(const struct dentry *dentry, struct cpu_vfs_cap_data *cpu_caps)
311{
312 struct inode *inode = dentry->d_inode;
b5376771 313 __u32 magic_etc;
e338d263 314 unsigned tocopy, i;
c0b00441
EP
315 int size;
316 struct vfs_cap_data caps;
317
318 memset(cpu_caps, 0, sizeof(struct cpu_vfs_cap_data));
319
320 if (!inode || !inode->i_op || !inode->i_op->getxattr)
321 return -ENODATA;
322
323 size = inode->i_op->getxattr((struct dentry *)dentry, XATTR_NAME_CAPS, &caps,
324 XATTR_CAPS_SZ);
a6f76f23 325 if (size == -ENODATA || size == -EOPNOTSUPP)
c0b00441
EP
326 /* no data, that's ok */
327 return -ENODATA;
c0b00441
EP
328 if (size < 0)
329 return size;
b5376771 330
e338d263 331 if (size < sizeof(magic_etc))
b5376771
SH
332 return -EINVAL;
333
c0b00441 334 cpu_caps->magic_etc = magic_etc = le32_to_cpu(caps.magic_etc);
b5376771 335
a6f76f23 336 switch (magic_etc & VFS_CAP_REVISION_MASK) {
e338d263
AM
337 case VFS_CAP_REVISION_1:
338 if (size != XATTR_CAPS_SZ_1)
339 return -EINVAL;
340 tocopy = VFS_CAP_U32_1;
341 break;
342 case VFS_CAP_REVISION_2:
343 if (size != XATTR_CAPS_SZ_2)
344 return -EINVAL;
345 tocopy = VFS_CAP_U32_2;
346 break;
b5376771
SH
347 default:
348 return -EINVAL;
349 }
e338d263 350
5459c164 351 CAP_FOR_EACH_U32(i) {
c0b00441
EP
352 if (i >= tocopy)
353 break;
354 cpu_caps->permitted.cap[i] = le32_to_cpu(caps.data[i].permitted);
355 cpu_caps->inheritable.cap[i] = le32_to_cpu(caps.data[i].inheritable);
e338d263 356 }
a6f76f23 357
c0b00441 358 return 0;
b5376771
SH
359}
360
1d045980
DH
361/*
362 * Attempt to get the on-exec apply capability sets for an executable file from
363 * its xattrs and, if present, apply them to the proposed credentials being
364 * constructed by execve().
365 */
a6f76f23 366static int get_file_caps(struct linux_binprm *bprm, bool *effective)
b5376771
SH
367{
368 struct dentry *dentry;
369 int rc = 0;
c0b00441 370 struct cpu_vfs_cap_data vcaps;
b5376771 371
3318a386
SH
372 bprm_clear_caps(bprm);
373
1f29fae2
SH
374 if (!file_caps_enabled)
375 return 0;
376
3318a386 377 if (bprm->file->f_vfsmnt->mnt_flags & MNT_NOSUID)
b5376771 378 return 0;
b5376771
SH
379
380 dentry = dget(bprm->file->f_dentry);
b5376771 381
c0b00441
EP
382 rc = get_vfs_caps_from_disk(dentry, &vcaps);
383 if (rc < 0) {
384 if (rc == -EINVAL)
385 printk(KERN_NOTICE "%s: get_vfs_caps_from_disk returned %d for %s\n",
386 __func__, rc, bprm->filename);
387 else if (rc == -ENODATA)
388 rc = 0;
b5376771
SH
389 goto out;
390 }
b5376771 391
a6f76f23
DH
392 rc = bprm_caps_from_vfs_caps(&vcaps, bprm, effective);
393 if (rc == -EINVAL)
394 printk(KERN_NOTICE "%s: cap_from_disk returned %d for %s\n",
395 __func__, rc, bprm->filename);
b5376771
SH
396
397out:
398 dput(dentry);
399 if (rc)
400 bprm_clear_caps(bprm);
401
402 return rc;
403}
404
405#else
406int cap_inode_need_killpriv(struct dentry *dentry)
407{
408 return 0;
409}
410
411int cap_inode_killpriv(struct dentry *dentry)
412{
413 return 0;
414}
415
e50a906e
EP
416int get_vfs_caps_from_disk(const struct dentry *dentry, struct cpu_vfs_cap_data *cpu_caps)
417{
418 memset(cpu_caps, 0, sizeof(struct cpu_vfs_cap_data));
419 return -ENODATA;
420}
421
a6f76f23 422static inline int get_file_caps(struct linux_binprm *bprm, bool *effective)
b5376771
SH
423{
424 bprm_clear_caps(bprm);
425 return 0;
426}
427#endif
428
a6f76f23 429/*
1d045980
DH
430 * Determine whether a exec'ing process's new permitted capabilities should be
431 * limited to just what it already has.
432 *
433 * This prevents processes that are being ptraced from gaining access to
434 * CAP_SETPCAP, unless the process they're tracing already has it, and the
435 * binary they're executing has filecaps that elevate it.
436 *
437 * Returns 1 if they should be limited, 0 if they are not.
438 */
439static inline int cap_limit_ptraced_target(void)
440{
441#ifndef CONFIG_SECURITY_FILE_CAPABILITIES
442 if (capable(CAP_SETPCAP))
443 return 0;
444#endif
445 return 1;
446}
447
448/**
449 * cap_bprm_set_creds - Set up the proposed credentials for execve().
450 * @bprm: The execution parameters, including the proposed creds
451 *
452 * Set up the proposed credentials for a new execution context being
453 * constructed by execve(). The proposed creds in @bprm->cred is altered,
454 * which won't take effect immediately. Returns 0 if successful, -ve on error.
a6f76f23
DH
455 */
456int cap_bprm_set_creds(struct linux_binprm *bprm)
1da177e4 457{
a6f76f23
DH
458 const struct cred *old = current_cred();
459 struct cred *new = bprm->cred;
460 bool effective;
b5376771 461 int ret;
1da177e4 462
a6f76f23
DH
463 effective = false;
464 ret = get_file_caps(bprm, &effective);
465 if (ret < 0)
466 return ret;
1da177e4 467
5459c164
AM
468 if (!issecure(SECURE_NOROOT)) {
469 /*
470 * To support inheritance of root-permissions and suid-root
471 * executables under compatibility mode, we override the
472 * capability sets for the file.
473 *
a6f76f23 474 * If only the real uid is 0, we do not set the effective bit.
5459c164 475 */
a6f76f23 476 if (new->euid == 0 || new->uid == 0) {
5459c164 477 /* pP' = (cap_bset & ~0) | (pI & ~0) */
a6f76f23
DH
478 new->cap_permitted = cap_combine(old->cap_bset,
479 old->cap_inheritable);
1da177e4 480 }
a6f76f23
DH
481 if (new->euid == 0)
482 effective = true;
1da177e4 483 }
b5376771 484
a6f76f23
DH
485 /* Don't let someone trace a set[ug]id/setpcap binary with the revised
486 * credentials unless they have the appropriate permit
487 */
488 if ((new->euid != old->uid ||
489 new->egid != old->gid ||
490 !cap_issubset(new->cap_permitted, old->cap_permitted)) &&
491 bprm->unsafe & ~LSM_UNSAFE_PTRACE_CAP) {
492 /* downgrade; they get no more than they had, and maybe less */
493 if (!capable(CAP_SETUID)) {
494 new->euid = new->uid;
495 new->egid = new->gid;
1da177e4 496 }
a6f76f23
DH
497 if (cap_limit_ptraced_target())
498 new->cap_permitted = cap_intersect(new->cap_permitted,
499 old->cap_permitted);
1da177e4
LT
500 }
501
a6f76f23
DH
502 new->suid = new->fsuid = new->euid;
503 new->sgid = new->fsgid = new->egid;
1da177e4 504
a6f76f23
DH
505 /* For init, we want to retain the capabilities set in the initial
506 * task. Thus we skip the usual capability rules
507 */
b460cbc5 508 if (!is_global_init(current)) {
a6f76f23
DH
509 if (effective)
510 new->cap_effective = new->cap_permitted;
e338d263 511 else
d84f4f99 512 cap_clear(new->cap_effective);
1da177e4 513 }
a6f76f23 514 bprm->cap_effective = effective;
1da177e4 515
3fc689e9
EP
516 /*
517 * Audit candidate if current->cap_effective is set
518 *
519 * We do not bother to audit if 3 things are true:
520 * 1) cap_effective has all caps
521 * 2) we are root
522 * 3) root is supposed to have all caps (SECURE_NOROOT)
523 * Since this is just a normal root execing a process.
524 *
525 * Number 1 above might fail if you don't have a full bset, but I think
526 * that is interesting information to audit.
527 */
d84f4f99
DH
528 if (!cap_isclear(new->cap_effective)) {
529 if (!cap_issubset(CAP_FULL_SET, new->cap_effective) ||
a6f76f23
DH
530 new->euid != 0 || new->uid != 0 ||
531 issecure(SECURE_NOROOT)) {
532 ret = audit_log_bprm_fcaps(bprm, new, old);
533 if (ret < 0)
534 return ret;
535 }
3fc689e9 536 }
1da177e4 537
d84f4f99 538 new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS);
a6f76f23 539 return 0;
1da177e4
LT
540}
541
1d045980
DH
542/**
543 * cap_bprm_secureexec - Determine whether a secure execution is required
544 * @bprm: The execution parameters
545 *
546 * Determine whether a secure execution is required, return 1 if it is, and 0
547 * if it is not.
548 *
549 * The credentials have been committed by this point, and so are no longer
550 * available through @bprm->cred.
a6f76f23
DH
551 */
552int cap_bprm_secureexec(struct linux_binprm *bprm)
1da177e4 553{
c69e8d9c 554 const struct cred *cred = current_cred();
b6dff3ec
DH
555
556 if (cred->uid != 0) {
b5376771
SH
557 if (bprm->cap_effective)
558 return 1;
a6f76f23 559 if (!cap_isclear(cred->cap_permitted))
b5376771
SH
560 return 1;
561 }
562
b6dff3ec
DH
563 return (cred->euid != cred->uid ||
564 cred->egid != cred->gid);
1da177e4
LT
565}
566
1d045980
DH
567/**
568 * cap_inode_setxattr - Determine whether an xattr may be altered
569 * @dentry: The inode/dentry being altered
570 * @name: The name of the xattr to be changed
571 * @value: The value that the xattr will be changed to
572 * @size: The size of value
573 * @flags: The replacement flag
574 *
575 * Determine whether an xattr may be altered or set on an inode, returning 0 if
576 * permission is granted, -ve if denied.
577 *
578 * This is used to make sure security xattrs don't get updated or set by those
579 * who aren't privileged to do so.
580 */
8f0cfa52
DH
581int cap_inode_setxattr(struct dentry *dentry, const char *name,
582 const void *value, size_t size, int flags)
1da177e4 583{
b5376771
SH
584 if (!strcmp(name, XATTR_NAME_CAPS)) {
585 if (!capable(CAP_SETFCAP))
586 return -EPERM;
587 return 0;
1d045980
DH
588 }
589
590 if (!strncmp(name, XATTR_SECURITY_PREFIX,
1da177e4
LT
591 sizeof(XATTR_SECURITY_PREFIX) - 1) &&
592 !capable(CAP_SYS_ADMIN))
593 return -EPERM;
594 return 0;
595}
596
1d045980
DH
597/**
598 * cap_inode_removexattr - Determine whether an xattr may be removed
599 * @dentry: The inode/dentry being altered
600 * @name: The name of the xattr to be changed
601 *
602 * Determine whether an xattr may be removed from an inode, returning 0 if
603 * permission is granted, -ve if denied.
604 *
605 * This is used to make sure security xattrs don't get removed by those who
606 * aren't privileged to remove them.
607 */
8f0cfa52 608int cap_inode_removexattr(struct dentry *dentry, const char *name)
1da177e4 609{
b5376771
SH
610 if (!strcmp(name, XATTR_NAME_CAPS)) {
611 if (!capable(CAP_SETFCAP))
612 return -EPERM;
613 return 0;
1d045980
DH
614 }
615
616 if (!strncmp(name, XATTR_SECURITY_PREFIX,
1da177e4
LT
617 sizeof(XATTR_SECURITY_PREFIX) - 1) &&
618 !capable(CAP_SYS_ADMIN))
619 return -EPERM;
620 return 0;
621}
622
a6f76f23 623/*
1da177e4
LT
624 * cap_emulate_setxuid() fixes the effective / permitted capabilities of
625 * a process after a call to setuid, setreuid, or setresuid.
626 *
627 * 1) When set*uiding _from_ one of {r,e,s}uid == 0 _to_ all of
628 * {r,e,s}uid != 0, the permitted and effective capabilities are
629 * cleared.
630 *
631 * 2) When set*uiding _from_ euid == 0 _to_ euid != 0, the effective
632 * capabilities of the process are cleared.
633 *
634 * 3) When set*uiding _from_ euid != 0 _to_ euid == 0, the effective
635 * capabilities are set to the permitted capabilities.
636 *
a6f76f23 637 * fsuid is handled elsewhere. fsuid == 0 and {r,e,s}uid!= 0 should
1da177e4
LT
638 * never happen.
639 *
a6f76f23 640 * -astor
1da177e4
LT
641 *
642 * cevans - New behaviour, Oct '99
643 * A process may, via prctl(), elect to keep its capabilities when it
644 * calls setuid() and switches away from uid==0. Both permitted and
645 * effective sets will be retained.
646 * Without this change, it was impossible for a daemon to drop only some
647 * of its privilege. The call to setuid(!=0) would drop all privileges!
648 * Keeping uid 0 is not an option because uid 0 owns too many vital
649 * files..
650 * Thanks to Olaf Kirch and Peter Benie for spotting this.
651 */
d84f4f99 652static inline void cap_emulate_setxuid(struct cred *new, const struct cred *old)
1da177e4 653{
d84f4f99
DH
654 if ((old->uid == 0 || old->euid == 0 || old->suid == 0) &&
655 (new->uid != 0 && new->euid != 0 && new->suid != 0) &&
3898b1b4 656 !issecure(SECURE_KEEP_CAPS)) {
d84f4f99
DH
657 cap_clear(new->cap_permitted);
658 cap_clear(new->cap_effective);
1da177e4 659 }
d84f4f99
DH
660 if (old->euid == 0 && new->euid != 0)
661 cap_clear(new->cap_effective);
662 if (old->euid != 0 && new->euid == 0)
663 new->cap_effective = new->cap_permitted;
1da177e4
LT
664}
665
1d045980
DH
666/**
667 * cap_task_fix_setuid - Fix up the results of setuid() call
668 * @new: The proposed credentials
669 * @old: The current task's current credentials
670 * @flags: Indications of what has changed
671 *
672 * Fix up the results of setuid() call before the credential changes are
673 * actually applied, returning 0 to grant the changes, -ve to deny them.
674 */
d84f4f99 675int cap_task_fix_setuid(struct cred *new, const struct cred *old, int flags)
1da177e4
LT
676{
677 switch (flags) {
678 case LSM_SETID_RE:
679 case LSM_SETID_ID:
680 case LSM_SETID_RES:
1d045980
DH
681 /* juggle the capabilities to follow [RES]UID changes unless
682 * otherwise suppressed */
d84f4f99
DH
683 if (!issecure(SECURE_NO_SETUID_FIXUP))
684 cap_emulate_setxuid(new, old);
1da177e4 685 break;
1da177e4 686
1d045980
DH
687 case LSM_SETID_FS:
688 /* juggle the capabilties to follow FSUID changes, unless
689 * otherwise suppressed
690 *
d84f4f99
DH
691 * FIXME - is fsuser used for all CAP_FS_MASK capabilities?
692 * if not, we might be a bit too harsh here.
693 */
694 if (!issecure(SECURE_NO_SETUID_FIXUP)) {
1d045980 695 if (old->fsuid == 0 && new->fsuid != 0)
d84f4f99
DH
696 new->cap_effective =
697 cap_drop_fs_set(new->cap_effective);
1d045980
DH
698
699 if (old->fsuid != 0 && new->fsuid == 0)
d84f4f99
DH
700 new->cap_effective =
701 cap_raise_fs_set(new->cap_effective,
702 new->cap_permitted);
1da177e4 703 }
d84f4f99 704 break;
1d045980 705
1da177e4
LT
706 default:
707 return -EINVAL;
708 }
709
710 return 0;
711}
712
b5376771
SH
713#ifdef CONFIG_SECURITY_FILE_CAPABILITIES
714/*
715 * Rationale: code calling task_setscheduler, task_setioprio, and
716 * task_setnice, assumes that
717 * . if capable(cap_sys_nice), then those actions should be allowed
718 * . if not capable(cap_sys_nice), but acting on your own processes,
719 * then those actions should be allowed
720 * This is insufficient now since you can call code without suid, but
721 * yet with increased caps.
722 * So we check for increased caps on the target process.
723 */
de45e806 724static int cap_safe_nice(struct task_struct *p)
b5376771 725{
c69e8d9c
DH
726 int is_subset;
727
728 rcu_read_lock();
729 is_subset = cap_issubset(__task_cred(p)->cap_permitted,
730 current_cred()->cap_permitted);
731 rcu_read_unlock();
732
733 if (!is_subset && !capable(CAP_SYS_NICE))
b5376771
SH
734 return -EPERM;
735 return 0;
736}
737
1d045980
DH
738/**
739 * cap_task_setscheduler - Detemine if scheduler policy change is permitted
740 * @p: The task to affect
741 * @policy: The policy to effect
742 * @lp: The parameters to the scheduling policy
743 *
744 * Detemine if the requested scheduler policy change is permitted for the
745 * specified task, returning 0 if permission is granted, -ve if denied.
746 */
747int cap_task_setscheduler(struct task_struct *p, int policy,
b5376771
SH
748 struct sched_param *lp)
749{
750 return cap_safe_nice(p);
751}
752
1d045980
DH
753/**
754 * cap_task_ioprio - Detemine if I/O priority change is permitted
755 * @p: The task to affect
756 * @ioprio: The I/O priority to set
757 *
758 * Detemine if the requested I/O priority change is permitted for the specified
759 * task, returning 0 if permission is granted, -ve if denied.
760 */
761int cap_task_setioprio(struct task_struct *p, int ioprio)
b5376771
SH
762{
763 return cap_safe_nice(p);
764}
765
1d045980
DH
766/**
767 * cap_task_ioprio - Detemine if task priority change is permitted
768 * @p: The task to affect
769 * @nice: The nice value to set
770 *
771 * Detemine if the requested task priority change is permitted for the
772 * specified task, returning 0 if permission is granted, -ve if denied.
773 */
774int cap_task_setnice(struct task_struct *p, int nice)
b5376771
SH
775{
776 return cap_safe_nice(p);
777}
778
3b7391de 779/*
1d045980
DH
780 * Implement PR_CAPBSET_DROP. Attempt to remove the specified capability from
781 * the current task's bounding set. Returns 0 on success, -ve on error.
3b7391de 782 */
d84f4f99 783static long cap_prctl_drop(struct cred *new, unsigned long cap)
3b7391de
SH
784{
785 if (!capable(CAP_SETPCAP))
786 return -EPERM;
787 if (!cap_valid(cap))
788 return -EINVAL;
d84f4f99
DH
789
790 cap_lower(new->cap_bset, cap);
3b7391de
SH
791 return 0;
792}
3898b1b4 793
b5376771
SH
794#else
795int cap_task_setscheduler (struct task_struct *p, int policy,
796 struct sched_param *lp)
797{
798 return 0;
799}
800int cap_task_setioprio (struct task_struct *p, int ioprio)
801{
802 return 0;
803}
804int cap_task_setnice (struct task_struct *p, int nice)
805{
806 return 0;
807}
b5376771
SH
808#endif
809
1d045980
DH
810/**
811 * cap_task_prctl - Implement process control functions for this security module
812 * @option: The process control function requested
813 * @arg2, @arg3, @arg4, @arg5: The argument data for this function
814 *
815 * Allow process control functions (sys_prctl()) to alter capabilities; may
816 * also deny access to other functions not otherwise implemented here.
817 *
818 * Returns 0 or +ve on success, -ENOSYS if this function is not implemented
819 * here, other -ve on error. If -ENOSYS is returned, sys_prctl() and other LSM
820 * modules will consider performing the function.
821 */
3898b1b4 822int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3,
d84f4f99 823 unsigned long arg4, unsigned long arg5)
3898b1b4 824{
d84f4f99 825 struct cred *new;
3898b1b4
AM
826 long error = 0;
827
d84f4f99
DH
828 new = prepare_creds();
829 if (!new)
830 return -ENOMEM;
831
3898b1b4
AM
832 switch (option) {
833 case PR_CAPBSET_READ:
d84f4f99 834 error = -EINVAL;
3898b1b4 835 if (!cap_valid(arg2))
d84f4f99
DH
836 goto error;
837 error = !!cap_raised(new->cap_bset, arg2);
838 goto no_change;
839
3898b1b4
AM
840#ifdef CONFIG_SECURITY_FILE_CAPABILITIES
841 case PR_CAPBSET_DROP:
d84f4f99
DH
842 error = cap_prctl_drop(new, arg2);
843 if (error < 0)
844 goto error;
845 goto changed;
3898b1b4
AM
846
847 /*
848 * The next four prctl's remain to assist with transitioning a
849 * system from legacy UID=0 based privilege (when filesystem
850 * capabilities are not in use) to a system using filesystem
851 * capabilities only - as the POSIX.1e draft intended.
852 *
853 * Note:
854 *
855 * PR_SET_SECUREBITS =
856 * issecure_mask(SECURE_KEEP_CAPS_LOCKED)
857 * | issecure_mask(SECURE_NOROOT)
858 * | issecure_mask(SECURE_NOROOT_LOCKED)
859 * | issecure_mask(SECURE_NO_SETUID_FIXUP)
860 * | issecure_mask(SECURE_NO_SETUID_FIXUP_LOCKED)
861 *
862 * will ensure that the current process and all of its
863 * children will be locked into a pure
864 * capability-based-privilege environment.
865 */
866 case PR_SET_SECUREBITS:
d84f4f99
DH
867 error = -EPERM;
868 if ((((new->securebits & SECURE_ALL_LOCKS) >> 1)
869 & (new->securebits ^ arg2)) /*[1]*/
870 || ((new->securebits & SECURE_ALL_LOCKS & ~arg2)) /*[2]*/
871 || (arg2 & ~(SECURE_ALL_LOCKS | SECURE_ALL_BITS)) /*[3]*/
872 || (cap_capable(current, CAP_SETPCAP, SECURITY_CAP_AUDIT) != 0) /*[4]*/
3898b1b4
AM
873 /*
874 * [1] no changing of bits that are locked
875 * [2] no unlocking of locks
876 * [3] no setting of unsupported bits
877 * [4] doing anything requires privilege (go read about
878 * the "sendmail capabilities bug")
879 */
d84f4f99
DH
880 )
881 /* cannot change a locked bit */
882 goto error;
883 new->securebits = arg2;
884 goto changed;
885
3898b1b4 886 case PR_GET_SECUREBITS:
d84f4f99
DH
887 error = new->securebits;
888 goto no_change;
3898b1b4
AM
889
890#endif /* def CONFIG_SECURITY_FILE_CAPABILITIES */
891
892 case PR_GET_KEEPCAPS:
893 if (issecure(SECURE_KEEP_CAPS))
894 error = 1;
d84f4f99
DH
895 goto no_change;
896
3898b1b4 897 case PR_SET_KEEPCAPS:
d84f4f99 898 error = -EINVAL;
3898b1b4 899 if (arg2 > 1) /* Note, we rely on arg2 being unsigned here */
d84f4f99
DH
900 goto error;
901 error = -EPERM;
902 if (issecure(SECURE_KEEP_CAPS_LOCKED))
903 goto error;
904 if (arg2)
905 new->securebits |= issecure_mask(SECURE_KEEP_CAPS);
3898b1b4 906 else
d84f4f99
DH
907 new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS);
908 goto changed;
3898b1b4
AM
909
910 default:
911 /* No functionality available - continue with default */
d84f4f99
DH
912 error = -ENOSYS;
913 goto error;
3898b1b4
AM
914 }
915
916 /* Functionality provided */
d84f4f99
DH
917changed:
918 return commit_creds(new);
919
920no_change:
921 error = 0;
922error:
923 abort_creds(new);
924 return error;
1da177e4
LT
925}
926
1d045980
DH
927/**
928 * cap_syslog - Determine whether syslog function is permitted
929 * @type: Function requested
930 *
931 * Determine whether the current process is permitted to use a particular
932 * syslog function, returning 0 if permission is granted, -ve if not.
933 */
934int cap_syslog(int type)
1da177e4
LT
935{
936 if ((type != 3 && type != 10) && !capable(CAP_SYS_ADMIN))
937 return -EPERM;
938 return 0;
939}
940
1d045980
DH
941/**
942 * cap_vm_enough_memory - Determine whether a new virtual mapping is permitted
943 * @mm: The VM space in which the new mapping is to be made
944 * @pages: The size of the mapping
945 *
946 * Determine whether the allocation of a new virtual mapping by the current
947 * task is permitted, returning 0 if permission is granted, -ve if not.
948 */
34b4e4aa 949int cap_vm_enough_memory(struct mm_struct *mm, long pages)
1da177e4
LT
950{
951 int cap_sys_admin = 0;
952
06112163 953 if (cap_capable(current, CAP_SYS_ADMIN, SECURITY_CAP_NOAUDIT) == 0)
1da177e4 954 cap_sys_admin = 1;
34b4e4aa 955 return __vm_enough_memory(mm, pages, cap_sys_admin);
1da177e4 956}