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1/* Common capabilities, needed by capability.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/audit.h>
12#include <linux/module.h>
13#include <linux/init.h>
14#include <linux/kernel.h>
15#include <linux/lsm_hooks.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>
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#include <linux/mount.h>
27#include <linux/sched.h>
28#include <linux/prctl.h>
29#include <linux/securebits.h>
30#include <linux/user_namespace.h>
31#include <linux/binfmts.h>
32#include <linux/personality.h>
33
34/*
35 * If a non-root user executes a setuid-root binary in
36 * !secure(SECURE_NOROOT) mode, then we raise capabilities.
37 * However if fE is also set, then the intent is for only
38 * the file capabilities to be applied, and the setuid-root
39 * bit is left on either to change the uid (plausible) or
40 * to get full privilege on a kernel without file capabilities
41 * support. So in that case we do not raise capabilities.
42 *
43 * Warn if that happens, once per boot.
44 */
45static void warn_setuid_and_fcaps_mixed(const char *fname)
46{
47 static int warned;
48 if (!warned) {
49 printk(KERN_INFO "warning: `%s' has both setuid-root and"
50 " effective capabilities. Therefore not raising all"
51 " capabilities.\n", fname);
52 warned = 1;
53 }
54}
55
56/**
57 * cap_capable - Determine whether a task has a particular effective capability
58 * @cred: The credentials to use
59 * @ns: The user namespace in which we need the capability
60 * @cap: The capability to check for
61 * @audit: Whether to write an audit message or not
62 *
63 * Determine whether the nominated task has the specified capability amongst
64 * its effective set, returning 0 if it does, -ve if it does not.
65 *
66 * NOTE WELL: cap_has_capability() cannot be used like the kernel's capable()
67 * and has_capability() functions. That is, it has the reverse semantics:
68 * cap_has_capability() returns 0 when a task has a capability, but the
69 * kernel's capable() and has_capability() returns 1 for this case.
70 */
71int cap_capable(const struct cred *cred, struct user_namespace *targ_ns,
72 int cap, int audit)
73{
74 struct user_namespace *ns = targ_ns;
75
76 /* See if cred has the capability in the target user namespace
77 * by examining the target user namespace and all of the target
78 * user namespace's parents.
79 */
80 for (;;) {
81 /* Do we have the necessary capabilities? */
82 if (ns == cred->user_ns)
83 return cap_raised(cred->cap_effective, cap) ? 0 : -EPERM;
84
85 /* Have we tried all of the parent namespaces? */
86 if (ns == &init_user_ns)
87 return -EPERM;
88
89 /*
90 * The owner of the user namespace in the parent of the
91 * user namespace has all caps.
92 */
93 if ((ns->parent == cred->user_ns) && uid_eq(ns->owner, cred->euid))
94 return 0;
95
96 /*
97 * If you have a capability in a parent user ns, then you have
98 * it over all children user namespaces as well.
99 */
100 ns = ns->parent;
101 }
102
103 /* We never get here */
104}
105
106/**
107 * cap_settime - Determine whether the current process may set the system clock
108 * @ts: The time to set
109 * @tz: The timezone to set
110 *
111 * Determine whether the current process may set the system clock and timezone
112 * information, returning 0 if permission granted, -ve if denied.
113 */
114int cap_settime(const struct timespec *ts, const struct timezone *tz)
115{
116 if (!capable(CAP_SYS_TIME))
117 return -EPERM;
118 return 0;
119}
120
121/**
122 * cap_ptrace_access_check - Determine whether the current process may access
123 * another
124 * @child: The process to be accessed
125 * @mode: The mode of attachment.
126 *
127 * If we are in the same or an ancestor user_ns and have all the target
128 * task's capabilities, then ptrace access is allowed.
129 * If we have the ptrace capability to the target user_ns, then ptrace
130 * access is allowed.
131 * Else denied.
132 *
133 * Determine whether a process may access another, returning 0 if permission
134 * granted, -ve if denied.
135 */
136int cap_ptrace_access_check(struct task_struct *child, unsigned int mode)
137{
138 int ret = 0;
139 const struct cred *cred, *child_cred;
140 const kernel_cap_t *caller_caps;
141
142 rcu_read_lock();
143 cred = current_cred();
144 child_cred = __task_cred(child);
145 if (mode & PTRACE_MODE_FSCREDS)
146 caller_caps = &cred->cap_effective;
147 else
148 caller_caps = &cred->cap_permitted;
149 if (cred->user_ns == child_cred->user_ns &&
150 cap_issubset(child_cred->cap_permitted, *caller_caps))
151 goto out;
152 if (ns_capable(child_cred->user_ns, CAP_SYS_PTRACE))
153 goto out;
154 ret = -EPERM;
155out:
156 rcu_read_unlock();
157 return ret;
158}
159
160/**
161 * cap_ptrace_traceme - Determine whether another process may trace the current
162 * @parent: The task proposed to be the tracer
163 *
164 * If parent is in the same or an ancestor user_ns and has all current's
165 * capabilities, then ptrace access is allowed.
166 * If parent has the ptrace capability to current's user_ns, then ptrace
167 * access is allowed.
168 * Else denied.
169 *
170 * Determine whether the nominated task is permitted to trace the current
171 * process, returning 0 if permission is granted, -ve if denied.
172 */
173int cap_ptrace_traceme(struct task_struct *parent)
174{
175 int ret = 0;
176 const struct cred *cred, *child_cred;
177
178 rcu_read_lock();
179 cred = __task_cred(parent);
180 child_cred = current_cred();
181 if (cred->user_ns == child_cred->user_ns &&
182 cap_issubset(child_cred->cap_permitted, cred->cap_permitted))
183 goto out;
184 if (has_ns_capability(parent, child_cred->user_ns, CAP_SYS_PTRACE))
185 goto out;
186 ret = -EPERM;
187out:
188 rcu_read_unlock();
189 return ret;
190}
191
192/**
193 * cap_capget - Retrieve a task's capability sets
194 * @target: The task from which to retrieve the capability sets
195 * @effective: The place to record the effective set
196 * @inheritable: The place to record the inheritable set
197 * @permitted: The place to record the permitted set
198 *
199 * This function retrieves the capabilities of the nominated task and returns
200 * them to the caller.
201 */
202int cap_capget(struct task_struct *target, kernel_cap_t *effective,
203 kernel_cap_t *inheritable, kernel_cap_t *permitted)
204{
205 const struct cred *cred;
206
207 /* Derived from kernel/capability.c:sys_capget. */
208 rcu_read_lock();
209 cred = __task_cred(target);
210 *effective = cred->cap_effective;
211 *inheritable = cred->cap_inheritable;
212 *permitted = cred->cap_permitted;
213 rcu_read_unlock();
214 return 0;
215}
216
217/*
218 * Determine whether the inheritable capabilities are limited to the old
219 * permitted set. Returns 1 if they are limited, 0 if they are not.
220 */
221static inline int cap_inh_is_capped(void)
222{
223
224 /* they are so limited unless the current task has the CAP_SETPCAP
225 * capability
226 */
227 if (cap_capable(current_cred(), current_cred()->user_ns,
228 CAP_SETPCAP, SECURITY_CAP_AUDIT) == 0)
229 return 0;
230 return 1;
231}
232
233/**
234 * cap_capset - Validate and apply proposed changes to current's capabilities
235 * @new: The proposed new credentials; alterations should be made here
236 * @old: The current task's current credentials
237 * @effective: A pointer to the proposed new effective capabilities set
238 * @inheritable: A pointer to the proposed new inheritable capabilities set
239 * @permitted: A pointer to the proposed new permitted capabilities set
240 *
241 * This function validates and applies a proposed mass change to the current
242 * process's capability sets. The changes are made to the proposed new
243 * credentials, and assuming no error, will be committed by the caller of LSM.
244 */
245int cap_capset(struct cred *new,
246 const struct cred *old,
247 const kernel_cap_t *effective,
248 const kernel_cap_t *inheritable,
249 const kernel_cap_t *permitted)
250{
251 if (cap_inh_is_capped() &&
252 !cap_issubset(*inheritable,
253 cap_combine(old->cap_inheritable,
254 old->cap_permitted)))
255 /* incapable of using this inheritable set */
256 return -EPERM;
257
258 if (!cap_issubset(*inheritable,
259 cap_combine(old->cap_inheritable,
260 old->cap_bset)))
261 /* no new pI capabilities outside bounding set */
262 return -EPERM;
263
264 /* verify restrictions on target's new Permitted set */
265 if (!cap_issubset(*permitted, old->cap_permitted))
266 return -EPERM;
267
268 /* verify the _new_Effective_ is a subset of the _new_Permitted_ */
269 if (!cap_issubset(*effective, *permitted))
270 return -EPERM;
271
272 new->cap_effective = *effective;
273 new->cap_inheritable = *inheritable;
274 new->cap_permitted = *permitted;
275
276 /*
277 * Mask off ambient bits that are no longer both permitted and
278 * inheritable.
279 */
280 new->cap_ambient = cap_intersect(new->cap_ambient,
281 cap_intersect(*permitted,
282 *inheritable));
283 if (WARN_ON(!cap_ambient_invariant_ok(new)))
284 return -EINVAL;
285 return 0;
286}
287
288/*
289 * Clear proposed capability sets for execve().
290 */
291static inline void bprm_clear_caps(struct linux_binprm *bprm)
292{
293 cap_clear(bprm->cred->cap_permitted);
294 bprm->cap_effective = false;
295}
296
297/**
298 * cap_inode_need_killpriv - Determine if inode change affects privileges
299 * @dentry: The inode/dentry in being changed with change marked ATTR_KILL_PRIV
300 *
301 * Determine if an inode having a change applied that's marked ATTR_KILL_PRIV
302 * affects the security markings on that inode, and if it is, should
303 * inode_killpriv() be invoked or the change rejected?
304 *
305 * Returns 0 if granted; +ve if granted, but inode_killpriv() is required; and
306 * -ve to deny the change.
307 */
308int cap_inode_need_killpriv(struct dentry *dentry)
309{
310 struct inode *inode = d_backing_inode(dentry);
311 int error;
312
313 if (!inode->i_op->getxattr)
314 return 0;
315
316 error = inode->i_op->getxattr(dentry, XATTR_NAME_CAPS, NULL, 0);
317 if (error <= 0)
318 return 0;
319 return 1;
320}
321
322/**
323 * cap_inode_killpriv - Erase the security markings on an inode
324 * @dentry: The inode/dentry to alter
325 *
326 * Erase the privilege-enhancing security markings on an inode.
327 *
328 * Returns 0 if successful, -ve on error.
329 */
330int cap_inode_killpriv(struct dentry *dentry)
331{
332 struct inode *inode = d_backing_inode(dentry);
333
334 if (!inode->i_op->removexattr)
335 return 0;
336
337 return inode->i_op->removexattr(dentry, XATTR_NAME_CAPS);
338}
339
340/*
341 * Calculate the new process capability sets from the capability sets attached
342 * to a file.
343 */
344static inline int bprm_caps_from_vfs_caps(struct cpu_vfs_cap_data *caps,
345 struct linux_binprm *bprm,
346 bool *effective,
347 bool *has_cap)
348{
349 struct cred *new = bprm->cred;
350 unsigned i;
351 int ret = 0;
352
353 if (caps->magic_etc & VFS_CAP_FLAGS_EFFECTIVE)
354 *effective = true;
355
356 if (caps->magic_etc & VFS_CAP_REVISION_MASK)
357 *has_cap = true;
358
359 CAP_FOR_EACH_U32(i) {
360 __u32 permitted = caps->permitted.cap[i];
361 __u32 inheritable = caps->inheritable.cap[i];
362
363 /*
364 * pP' = (X & fP) | (pI & fI)
365 * The addition of pA' is handled later.
366 */
367 new->cap_permitted.cap[i] =
368 (new->cap_bset.cap[i] & permitted) |
369 (new->cap_inheritable.cap[i] & inheritable);
370
371 if (permitted & ~new->cap_permitted.cap[i])
372 /* insufficient to execute correctly */
373 ret = -EPERM;
374 }
375
376 /*
377 * For legacy apps, with no internal support for recognizing they
378 * do not have enough capabilities, we return an error if they are
379 * missing some "forced" (aka file-permitted) capabilities.
380 */
381 return *effective ? ret : 0;
382}
383
384/*
385 * Extract the on-exec-apply capability sets for an executable file.
386 */
387int get_vfs_caps_from_disk(const struct dentry *dentry, struct cpu_vfs_cap_data *cpu_caps)
388{
389 struct inode *inode = d_backing_inode(dentry);
390 __u32 magic_etc;
391 unsigned tocopy, i;
392 int size;
393 struct vfs_cap_data caps;
394
395 memset(cpu_caps, 0, sizeof(struct cpu_vfs_cap_data));
396
397 if (!inode || !inode->i_op->getxattr)
398 return -ENODATA;
399
400 size = inode->i_op->getxattr((struct dentry *)dentry, XATTR_NAME_CAPS, &caps,
401 XATTR_CAPS_SZ);
402 if (size == -ENODATA || size == -EOPNOTSUPP)
403 /* no data, that's ok */
404 return -ENODATA;
405 if (size < 0)
406 return size;
407
408 if (size < sizeof(magic_etc))
409 return -EINVAL;
410
411 cpu_caps->magic_etc = magic_etc = le32_to_cpu(caps.magic_etc);
412
413 switch (magic_etc & VFS_CAP_REVISION_MASK) {
414 case VFS_CAP_REVISION_1:
415 if (size != XATTR_CAPS_SZ_1)
416 return -EINVAL;
417 tocopy = VFS_CAP_U32_1;
418 break;
419 case VFS_CAP_REVISION_2:
420 if (size != XATTR_CAPS_SZ_2)
421 return -EINVAL;
422 tocopy = VFS_CAP_U32_2;
423 break;
424 default:
425 return -EINVAL;
426 }
427
428 CAP_FOR_EACH_U32(i) {
429 if (i >= tocopy)
430 break;
431 cpu_caps->permitted.cap[i] = le32_to_cpu(caps.data[i].permitted);
432 cpu_caps->inheritable.cap[i] = le32_to_cpu(caps.data[i].inheritable);
433 }
434
435 cpu_caps->permitted.cap[CAP_LAST_U32] &= CAP_LAST_U32_VALID_MASK;
436 cpu_caps->inheritable.cap[CAP_LAST_U32] &= CAP_LAST_U32_VALID_MASK;
437
438 return 0;
439}
440
441/*
442 * Attempt to get the on-exec apply capability sets for an executable file from
443 * its xattrs and, if present, apply them to the proposed credentials being
444 * constructed by execve().
445 */
446static int get_file_caps(struct linux_binprm *bprm, bool *effective, bool *has_cap)
447{
448 int rc = 0;
449 struct cpu_vfs_cap_data vcaps;
450
451 bprm_clear_caps(bprm);
452
453 if (!file_caps_enabled)
454 return 0;
455
456 if (bprm->file->f_path.mnt->mnt_flags & MNT_NOSUID)
457 return 0;
458
459 rc = get_vfs_caps_from_disk(bprm->file->f_path.dentry, &vcaps);
460 if (rc < 0) {
461 if (rc == -EINVAL)
462 printk(KERN_NOTICE "%s: get_vfs_caps_from_disk returned %d for %s\n",
463 __func__, rc, bprm->filename);
464 else if (rc == -ENODATA)
465 rc = 0;
466 goto out;
467 }
468
469 rc = bprm_caps_from_vfs_caps(&vcaps, bprm, effective, has_cap);
470 if (rc == -EINVAL)
471 printk(KERN_NOTICE "%s: cap_from_disk returned %d for %s\n",
472 __func__, rc, bprm->filename);
473
474out:
475 if (rc)
476 bprm_clear_caps(bprm);
477
478 return rc;
479}
480
481/**
482 * cap_bprm_set_creds - Set up the proposed credentials for execve().
483 * @bprm: The execution parameters, including the proposed creds
484 *
485 * Set up the proposed credentials for a new execution context being
486 * constructed by execve(). The proposed creds in @bprm->cred is altered,
487 * which won't take effect immediately. Returns 0 if successful, -ve on error.
488 */
489int cap_bprm_set_creds(struct linux_binprm *bprm)
490{
491 const struct cred *old = current_cred();
492 struct cred *new = bprm->cred;
493 bool effective, has_cap = false, is_setid;
494 int ret;
495 kuid_t root_uid;
496
497 if (WARN_ON(!cap_ambient_invariant_ok(old)))
498 return -EPERM;
499
500 effective = false;
501 ret = get_file_caps(bprm, &effective, &has_cap);
502 if (ret < 0)
503 return ret;
504
505 root_uid = make_kuid(new->user_ns, 0);
506
507 if (!issecure(SECURE_NOROOT)) {
508 /*
509 * If the legacy file capability is set, then don't set privs
510 * for a setuid root binary run by a non-root user. Do set it
511 * for a root user just to cause least surprise to an admin.
512 */
513 if (has_cap && !uid_eq(new->uid, root_uid) && uid_eq(new->euid, root_uid)) {
514 warn_setuid_and_fcaps_mixed(bprm->filename);
515 goto skip;
516 }
517 /*
518 * To support inheritance of root-permissions and suid-root
519 * executables under compatibility mode, we override the
520 * capability sets for the file.
521 *
522 * If only the real uid is 0, we do not set the effective bit.
523 */
524 if (uid_eq(new->euid, root_uid) || uid_eq(new->uid, root_uid)) {
525 /* pP' = (cap_bset & ~0) | (pI & ~0) */
526 new->cap_permitted = cap_combine(old->cap_bset,
527 old->cap_inheritable);
528 }
529 if (uid_eq(new->euid, root_uid))
530 effective = true;
531 }
532skip:
533
534 /* if we have fs caps, clear dangerous personality flags */
535 if (!cap_issubset(new->cap_permitted, old->cap_permitted))
536 bprm->per_clear |= PER_CLEAR_ON_SETID;
537
538
539 /* Don't let someone trace a set[ug]id/setpcap binary with the revised
540 * credentials unless they have the appropriate permit.
541 *
542 * In addition, if NO_NEW_PRIVS, then ensure we get no new privs.
543 */
544 is_setid = !uid_eq(new->euid, old->uid) || !gid_eq(new->egid, old->gid);
545
546 if ((is_setid ||
547 !cap_issubset(new->cap_permitted, old->cap_permitted)) &&
548 bprm->unsafe & ~LSM_UNSAFE_PTRACE_CAP) {
549 /* downgrade; they get no more than they had, and maybe less */
550 if (!capable(CAP_SETUID) ||
551 (bprm->unsafe & LSM_UNSAFE_NO_NEW_PRIVS)) {
552 new->euid = new->uid;
553 new->egid = new->gid;
554 }
555 new->cap_permitted = cap_intersect(new->cap_permitted,
556 old->cap_permitted);
557 }
558
559 new->suid = new->fsuid = new->euid;
560 new->sgid = new->fsgid = new->egid;
561
562 /* File caps or setid cancels ambient. */
563 if (has_cap || is_setid)
564 cap_clear(new->cap_ambient);
565
566 /*
567 * Now that we've computed pA', update pP' to give:
568 * pP' = (X & fP) | (pI & fI) | pA'
569 */
570 new->cap_permitted = cap_combine(new->cap_permitted, new->cap_ambient);
571
572 /*
573 * Set pE' = (fE ? pP' : pA'). Because pA' is zero if fE is set,
574 * this is the same as pE' = (fE ? pP' : 0) | pA'.
575 */
576 if (effective)
577 new->cap_effective = new->cap_permitted;
578 else
579 new->cap_effective = new->cap_ambient;
580
581 if (WARN_ON(!cap_ambient_invariant_ok(new)))
582 return -EPERM;
583
584 bprm->cap_effective = effective;
585
586 /*
587 * Audit candidate if current->cap_effective is set
588 *
589 * We do not bother to audit if 3 things are true:
590 * 1) cap_effective has all caps
591 * 2) we are root
592 * 3) root is supposed to have all caps (SECURE_NOROOT)
593 * Since this is just a normal root execing a process.
594 *
595 * Number 1 above might fail if you don't have a full bset, but I think
596 * that is interesting information to audit.
597 */
598 if (!cap_issubset(new->cap_effective, new->cap_ambient)) {
599 if (!cap_issubset(CAP_FULL_SET, new->cap_effective) ||
600 !uid_eq(new->euid, root_uid) || !uid_eq(new->uid, root_uid) ||
601 issecure(SECURE_NOROOT)) {
602 ret = audit_log_bprm_fcaps(bprm, new, old);
603 if (ret < 0)
604 return ret;
605 }
606 }
607
608 new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS);
609
610 if (WARN_ON(!cap_ambient_invariant_ok(new)))
611 return -EPERM;
612
613 return 0;
614}
615
616/**
617 * cap_bprm_secureexec - Determine whether a secure execution is required
618 * @bprm: The execution parameters
619 *
620 * Determine whether a secure execution is required, return 1 if it is, and 0
621 * if it is not.
622 *
623 * The credentials have been committed by this point, and so are no longer
624 * available through @bprm->cred.
625 */
626int cap_bprm_secureexec(struct linux_binprm *bprm)
627{
628 const struct cred *cred = current_cred();
629 kuid_t root_uid = make_kuid(cred->user_ns, 0);
630
631 if (!uid_eq(cred->uid, root_uid)) {
632 if (bprm->cap_effective)
633 return 1;
634 if (!cap_issubset(cred->cap_permitted, cred->cap_ambient))
635 return 1;
636 }
637
638 return (!uid_eq(cred->euid, cred->uid) ||
639 !gid_eq(cred->egid, cred->gid));
640}
641
642/**
643 * cap_inode_setxattr - Determine whether an xattr may be altered
644 * @dentry: The inode/dentry being altered
645 * @name: The name of the xattr to be changed
646 * @value: The value that the xattr will be changed to
647 * @size: The size of value
648 * @flags: The replacement flag
649 *
650 * Determine whether an xattr may be altered or set on an inode, returning 0 if
651 * permission is granted, -ve if denied.
652 *
653 * This is used to make sure security xattrs don't get updated or set by those
654 * who aren't privileged to do so.
655 */
656int cap_inode_setxattr(struct dentry *dentry, const char *name,
657 const void *value, size_t size, int flags)
658{
659 if (!strcmp(name, XATTR_NAME_CAPS)) {
660 if (!capable(CAP_SETFCAP))
661 return -EPERM;
662 return 0;
663 }
664
665 if (!strncmp(name, XATTR_SECURITY_PREFIX,
666 sizeof(XATTR_SECURITY_PREFIX) - 1) &&
667 !capable(CAP_SYS_ADMIN))
668 return -EPERM;
669 return 0;
670}
671
672/**
673 * cap_inode_removexattr - Determine whether an xattr may be removed
674 * @dentry: The inode/dentry being altered
675 * @name: The name of the xattr to be changed
676 *
677 * Determine whether an xattr may be removed from an inode, returning 0 if
678 * permission is granted, -ve if denied.
679 *
680 * This is used to make sure security xattrs don't get removed by those who
681 * aren't privileged to remove them.
682 */
683int cap_inode_removexattr(struct dentry *dentry, const char *name)
684{
685 if (!strcmp(name, XATTR_NAME_CAPS)) {
686 if (!capable(CAP_SETFCAP))
687 return -EPERM;
688 return 0;
689 }
690
691 if (!strncmp(name, XATTR_SECURITY_PREFIX,
692 sizeof(XATTR_SECURITY_PREFIX) - 1) &&
693 !capable(CAP_SYS_ADMIN))
694 return -EPERM;
695 return 0;
696}
697
698/*
699 * cap_emulate_setxuid() fixes the effective / permitted capabilities of
700 * a process after a call to setuid, setreuid, or setresuid.
701 *
702 * 1) When set*uiding _from_ one of {r,e,s}uid == 0 _to_ all of
703 * {r,e,s}uid != 0, the permitted and effective capabilities are
704 * cleared.
705 *
706 * 2) When set*uiding _from_ euid == 0 _to_ euid != 0, the effective
707 * capabilities of the process are cleared.
708 *
709 * 3) When set*uiding _from_ euid != 0 _to_ euid == 0, the effective
710 * capabilities are set to the permitted capabilities.
711 *
712 * fsuid is handled elsewhere. fsuid == 0 and {r,e,s}uid!= 0 should
713 * never happen.
714 *
715 * -astor
716 *
717 * cevans - New behaviour, Oct '99
718 * A process may, via prctl(), elect to keep its capabilities when it
719 * calls setuid() and switches away from uid==0. Both permitted and
720 * effective sets will be retained.
721 * Without this change, it was impossible for a daemon to drop only some
722 * of its privilege. The call to setuid(!=0) would drop all privileges!
723 * Keeping uid 0 is not an option because uid 0 owns too many vital
724 * files..
725 * Thanks to Olaf Kirch and Peter Benie for spotting this.
726 */
727static inline void cap_emulate_setxuid(struct cred *new, const struct cred *old)
728{
729 kuid_t root_uid = make_kuid(old->user_ns, 0);
730
731 if ((uid_eq(old->uid, root_uid) ||
732 uid_eq(old->euid, root_uid) ||
733 uid_eq(old->suid, root_uid)) &&
734 (!uid_eq(new->uid, root_uid) &&
735 !uid_eq(new->euid, root_uid) &&
736 !uid_eq(new->suid, root_uid))) {
737 if (!issecure(SECURE_KEEP_CAPS)) {
738 cap_clear(new->cap_permitted);
739 cap_clear(new->cap_effective);
740 }
741
742 /*
743 * Pre-ambient programs expect setresuid to nonroot followed
744 * by exec to drop capabilities. We should make sure that
745 * this remains the case.
746 */
747 cap_clear(new->cap_ambient);
748 }
749 if (uid_eq(old->euid, root_uid) && !uid_eq(new->euid, root_uid))
750 cap_clear(new->cap_effective);
751 if (!uid_eq(old->euid, root_uid) && uid_eq(new->euid, root_uid))
752 new->cap_effective = new->cap_permitted;
753}
754
755/**
756 * cap_task_fix_setuid - Fix up the results of setuid() call
757 * @new: The proposed credentials
758 * @old: The current task's current credentials
759 * @flags: Indications of what has changed
760 *
761 * Fix up the results of setuid() call before the credential changes are
762 * actually applied, returning 0 to grant the changes, -ve to deny them.
763 */
764int cap_task_fix_setuid(struct cred *new, const struct cred *old, int flags)
765{
766 switch (flags) {
767 case LSM_SETID_RE:
768 case LSM_SETID_ID:
769 case LSM_SETID_RES:
770 /* juggle the capabilities to follow [RES]UID changes unless
771 * otherwise suppressed */
772 if (!issecure(SECURE_NO_SETUID_FIXUP))
773 cap_emulate_setxuid(new, old);
774 break;
775
776 case LSM_SETID_FS:
777 /* juggle the capabilties to follow FSUID changes, unless
778 * otherwise suppressed
779 *
780 * FIXME - is fsuser used for all CAP_FS_MASK capabilities?
781 * if not, we might be a bit too harsh here.
782 */
783 if (!issecure(SECURE_NO_SETUID_FIXUP)) {
784 kuid_t root_uid = make_kuid(old->user_ns, 0);
785 if (uid_eq(old->fsuid, root_uid) && !uid_eq(new->fsuid, root_uid))
786 new->cap_effective =
787 cap_drop_fs_set(new->cap_effective);
788
789 if (!uid_eq(old->fsuid, root_uid) && uid_eq(new->fsuid, root_uid))
790 new->cap_effective =
791 cap_raise_fs_set(new->cap_effective,
792 new->cap_permitted);
793 }
794 break;
795
796 default:
797 return -EINVAL;
798 }
799
800 return 0;
801}
802
803/*
804 * Rationale: code calling task_setscheduler, task_setioprio, and
805 * task_setnice, assumes that
806 * . if capable(cap_sys_nice), then those actions should be allowed
807 * . if not capable(cap_sys_nice), but acting on your own processes,
808 * then those actions should be allowed
809 * This is insufficient now since you can call code without suid, but
810 * yet with increased caps.
811 * So we check for increased caps on the target process.
812 */
813static int cap_safe_nice(struct task_struct *p)
814{
815 int is_subset, ret = 0;
816
817 rcu_read_lock();
818 is_subset = cap_issubset(__task_cred(p)->cap_permitted,
819 current_cred()->cap_permitted);
820 if (!is_subset && !ns_capable(__task_cred(p)->user_ns, CAP_SYS_NICE))
821 ret = -EPERM;
822 rcu_read_unlock();
823
824 return ret;
825}
826
827/**
828 * cap_task_setscheduler - Detemine if scheduler policy change is permitted
829 * @p: The task to affect
830 *
831 * Detemine if the requested scheduler policy change is permitted for the
832 * specified task, returning 0 if permission is granted, -ve if denied.
833 */
834int cap_task_setscheduler(struct task_struct *p)
835{
836 return cap_safe_nice(p);
837}
838
839/**
840 * cap_task_ioprio - Detemine if I/O priority change is permitted
841 * @p: The task to affect
842 * @ioprio: The I/O priority to set
843 *
844 * Detemine if the requested I/O priority change is permitted for the specified
845 * task, returning 0 if permission is granted, -ve if denied.
846 */
847int cap_task_setioprio(struct task_struct *p, int ioprio)
848{
849 return cap_safe_nice(p);
850}
851
852/**
853 * cap_task_ioprio - Detemine if task priority change is permitted
854 * @p: The task to affect
855 * @nice: The nice value to set
856 *
857 * Detemine if the requested task priority change is permitted for the
858 * specified task, returning 0 if permission is granted, -ve if denied.
859 */
860int cap_task_setnice(struct task_struct *p, int nice)
861{
862 return cap_safe_nice(p);
863}
864
865/*
866 * Implement PR_CAPBSET_DROP. Attempt to remove the specified capability from
867 * the current task's bounding set. Returns 0 on success, -ve on error.
868 */
869static int cap_prctl_drop(unsigned long cap)
870{
871 struct cred *new;
872
873 if (!ns_capable(current_user_ns(), CAP_SETPCAP))
874 return -EPERM;
875 if (!cap_valid(cap))
876 return -EINVAL;
877
878 new = prepare_creds();
879 if (!new)
880 return -ENOMEM;
881 cap_lower(new->cap_bset, cap);
882 return commit_creds(new);
883}
884
885/**
886 * cap_task_prctl - Implement process control functions for this security module
887 * @option: The process control function requested
888 * @arg2, @arg3, @arg4, @arg5: The argument data for this function
889 *
890 * Allow process control functions (sys_prctl()) to alter capabilities; may
891 * also deny access to other functions not otherwise implemented here.
892 *
893 * Returns 0 or +ve on success, -ENOSYS if this function is not implemented
894 * here, other -ve on error. If -ENOSYS is returned, sys_prctl() and other LSM
895 * modules will consider performing the function.
896 */
897int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3,
898 unsigned long arg4, unsigned long arg5)
899{
900 const struct cred *old = current_cred();
901 struct cred *new;
902
903 switch (option) {
904 case PR_CAPBSET_READ:
905 if (!cap_valid(arg2))
906 return -EINVAL;
907 return !!cap_raised(old->cap_bset, arg2);
908
909 case PR_CAPBSET_DROP:
910 return cap_prctl_drop(arg2);
911
912 /*
913 * The next four prctl's remain to assist with transitioning a
914 * system from legacy UID=0 based privilege (when filesystem
915 * capabilities are not in use) to a system using filesystem
916 * capabilities only - as the POSIX.1e draft intended.
917 *
918 * Note:
919 *
920 * PR_SET_SECUREBITS =
921 * issecure_mask(SECURE_KEEP_CAPS_LOCKED)
922 * | issecure_mask(SECURE_NOROOT)
923 * | issecure_mask(SECURE_NOROOT_LOCKED)
924 * | issecure_mask(SECURE_NO_SETUID_FIXUP)
925 * | issecure_mask(SECURE_NO_SETUID_FIXUP_LOCKED)
926 *
927 * will ensure that the current process and all of its
928 * children will be locked into a pure
929 * capability-based-privilege environment.
930 */
931 case PR_SET_SECUREBITS:
932 if ((((old->securebits & SECURE_ALL_LOCKS) >> 1)
933 & (old->securebits ^ arg2)) /*[1]*/
934 || ((old->securebits & SECURE_ALL_LOCKS & ~arg2)) /*[2]*/
935 || (arg2 & ~(SECURE_ALL_LOCKS | SECURE_ALL_BITS)) /*[3]*/
936 || (cap_capable(current_cred(),
937 current_cred()->user_ns, CAP_SETPCAP,
938 SECURITY_CAP_AUDIT) != 0) /*[4]*/
939 /*
940 * [1] no changing of bits that are locked
941 * [2] no unlocking of locks
942 * [3] no setting of unsupported bits
943 * [4] doing anything requires privilege (go read about
944 * the "sendmail capabilities bug")
945 */
946 )
947 /* cannot change a locked bit */
948 return -EPERM;
949
950 new = prepare_creds();
951 if (!new)
952 return -ENOMEM;
953 new->securebits = arg2;
954 return commit_creds(new);
955
956 case PR_GET_SECUREBITS:
957 return old->securebits;
958
959 case PR_GET_KEEPCAPS:
960 return !!issecure(SECURE_KEEP_CAPS);
961
962 case PR_SET_KEEPCAPS:
963 if (arg2 > 1) /* Note, we rely on arg2 being unsigned here */
964 return -EINVAL;
965 if (issecure(SECURE_KEEP_CAPS_LOCKED))
966 return -EPERM;
967
968 new = prepare_creds();
969 if (!new)
970 return -ENOMEM;
971 if (arg2)
972 new->securebits |= issecure_mask(SECURE_KEEP_CAPS);
973 else
974 new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS);
975 return commit_creds(new);
976
977 case PR_CAP_AMBIENT:
978 if (arg2 == PR_CAP_AMBIENT_CLEAR_ALL) {
979 if (arg3 | arg4 | arg5)
980 return -EINVAL;
981
982 new = prepare_creds();
983 if (!new)
984 return -ENOMEM;
985 cap_clear(new->cap_ambient);
986 return commit_creds(new);
987 }
988
989 if (((!cap_valid(arg3)) | arg4 | arg5))
990 return -EINVAL;
991
992 if (arg2 == PR_CAP_AMBIENT_IS_SET) {
993 return !!cap_raised(current_cred()->cap_ambient, arg3);
994 } else if (arg2 != PR_CAP_AMBIENT_RAISE &&
995 arg2 != PR_CAP_AMBIENT_LOWER) {
996 return -EINVAL;
997 } else {
998 if (arg2 == PR_CAP_AMBIENT_RAISE &&
999 (!cap_raised(current_cred()->cap_permitted, arg3) ||
1000 !cap_raised(current_cred()->cap_inheritable,
1001 arg3) ||
1002 issecure(SECURE_NO_CAP_AMBIENT_RAISE)))
1003 return -EPERM;
1004
1005 new = prepare_creds();
1006 if (!new)
1007 return -ENOMEM;
1008 if (arg2 == PR_CAP_AMBIENT_RAISE)
1009 cap_raise(new->cap_ambient, arg3);
1010 else
1011 cap_lower(new->cap_ambient, arg3);
1012 return commit_creds(new);
1013 }
1014
1015 default:
1016 /* No functionality available - continue with default */
1017 return -ENOSYS;
1018 }
1019}
1020
1021/**
1022 * cap_vm_enough_memory - Determine whether a new virtual mapping is permitted
1023 * @mm: The VM space in which the new mapping is to be made
1024 * @pages: The size of the mapping
1025 *
1026 * Determine whether the allocation of a new virtual mapping by the current
1027 * task is permitted, returning 1 if permission is granted, 0 if not.
1028 */
1029int cap_vm_enough_memory(struct mm_struct *mm, long pages)
1030{
1031 int cap_sys_admin = 0;
1032
1033 if (cap_capable(current_cred(), &init_user_ns, CAP_SYS_ADMIN,
1034 SECURITY_CAP_NOAUDIT) == 0)
1035 cap_sys_admin = 1;
1036 return cap_sys_admin;
1037}
1038
1039/*
1040 * cap_mmap_addr - check if able to map given addr
1041 * @addr: address attempting to be mapped
1042 *
1043 * If the process is attempting to map memory below dac_mmap_min_addr they need
1044 * CAP_SYS_RAWIO. The other parameters to this function are unused by the
1045 * capability security module. Returns 0 if this mapping should be allowed
1046 * -EPERM if not.
1047 */
1048int cap_mmap_addr(unsigned long addr)
1049{
1050 int ret = 0;
1051
1052 if (addr < dac_mmap_min_addr) {
1053 ret = cap_capable(current_cred(), &init_user_ns, CAP_SYS_RAWIO,
1054 SECURITY_CAP_AUDIT);
1055 /* set PF_SUPERPRIV if it turns out we allow the low mmap */
1056 if (ret == 0)
1057 current->flags |= PF_SUPERPRIV;
1058 }
1059 return ret;
1060}
1061
1062int cap_mmap_file(struct file *file, unsigned long reqprot,
1063 unsigned long prot, unsigned long flags)
1064{
1065 return 0;
1066}
1067
1068#ifdef CONFIG_SECURITY
1069
1070struct security_hook_list capability_hooks[] = {
1071 LSM_HOOK_INIT(capable, cap_capable),
1072 LSM_HOOK_INIT(settime, cap_settime),
1073 LSM_HOOK_INIT(ptrace_access_check, cap_ptrace_access_check),
1074 LSM_HOOK_INIT(ptrace_traceme, cap_ptrace_traceme),
1075 LSM_HOOK_INIT(capget, cap_capget),
1076 LSM_HOOK_INIT(capset, cap_capset),
1077 LSM_HOOK_INIT(bprm_set_creds, cap_bprm_set_creds),
1078 LSM_HOOK_INIT(bprm_secureexec, cap_bprm_secureexec),
1079 LSM_HOOK_INIT(inode_need_killpriv, cap_inode_need_killpriv),
1080 LSM_HOOK_INIT(inode_killpriv, cap_inode_killpriv),
1081 LSM_HOOK_INIT(mmap_addr, cap_mmap_addr),
1082 LSM_HOOK_INIT(mmap_file, cap_mmap_file),
1083 LSM_HOOK_INIT(task_fix_setuid, cap_task_fix_setuid),
1084 LSM_HOOK_INIT(task_prctl, cap_task_prctl),
1085 LSM_HOOK_INIT(task_setscheduler, cap_task_setscheduler),
1086 LSM_HOOK_INIT(task_setioprio, cap_task_setioprio),
1087 LSM_HOOK_INIT(task_setnice, cap_task_setnice),
1088 LSM_HOOK_INIT(vm_enough_memory, cap_vm_enough_memory),
1089};
1090
1091void __init capability_add_hooks(void)
1092{
1093 security_add_hooks(capability_hooks, ARRAY_SIZE(capability_hooks));
1094}
1095
1096#endif /* CONFIG_SECURITY */
1// SPDX-License-Identifier: GPL-2.0-or-later
2/* Common capabilities, needed by capability.o.
3 */
4
5#include <linux/capability.h>
6#include <linux/audit.h>
7#include <linux/init.h>
8#include <linux/kernel.h>
9#include <linux/lsm_hooks.h>
10#include <linux/file.h>
11#include <linux/mm.h>
12#include <linux/mman.h>
13#include <linux/pagemap.h>
14#include <linux/swap.h>
15#include <linux/skbuff.h>
16#include <linux/netlink.h>
17#include <linux/ptrace.h>
18#include <linux/xattr.h>
19#include <linux/hugetlb.h>
20#include <linux/mount.h>
21#include <linux/sched.h>
22#include <linux/prctl.h>
23#include <linux/securebits.h>
24#include <linux/user_namespace.h>
25#include <linux/binfmts.h>
26#include <linux/personality.h>
27
28/*
29 * If a non-root user executes a setuid-root binary in
30 * !secure(SECURE_NOROOT) mode, then we raise capabilities.
31 * However if fE is also set, then the intent is for only
32 * the file capabilities to be applied, and the setuid-root
33 * bit is left on either to change the uid (plausible) or
34 * to get full privilege on a kernel without file capabilities
35 * support. So in that case we do not raise capabilities.
36 *
37 * Warn if that happens, once per boot.
38 */
39static void warn_setuid_and_fcaps_mixed(const char *fname)
40{
41 static int warned;
42 if (!warned) {
43 printk(KERN_INFO "warning: `%s' has both setuid-root and"
44 " effective capabilities. Therefore not raising all"
45 " capabilities.\n", fname);
46 warned = 1;
47 }
48}
49
50/**
51 * cap_capable - Determine whether a task has a particular effective capability
52 * @cred: The credentials to use
53 * @targ_ns: The user namespace in which we need the capability
54 * @cap: The capability to check for
55 * @opts: Bitmask of options defined in include/linux/security.h
56 *
57 * Determine whether the nominated task has the specified capability amongst
58 * its effective set, returning 0 if it does, -ve if it does not.
59 *
60 * NOTE WELL: cap_has_capability() cannot be used like the kernel's capable()
61 * and has_capability() functions. That is, it has the reverse semantics:
62 * cap_has_capability() returns 0 when a task has a capability, but the
63 * kernel's capable() and has_capability() returns 1 for this case.
64 */
65int cap_capable(const struct cred *cred, struct user_namespace *targ_ns,
66 int cap, unsigned int opts)
67{
68 struct user_namespace *ns = targ_ns;
69
70 /* See if cred has the capability in the target user namespace
71 * by examining the target user namespace and all of the target
72 * user namespace's parents.
73 */
74 for (;;) {
75 /* Do we have the necessary capabilities? */
76 if (ns == cred->user_ns)
77 return cap_raised(cred->cap_effective, cap) ? 0 : -EPERM;
78
79 /*
80 * If we're already at a lower level than we're looking for,
81 * we're done searching.
82 */
83 if (ns->level <= cred->user_ns->level)
84 return -EPERM;
85
86 /*
87 * The owner of the user namespace in the parent of the
88 * user namespace has all caps.
89 */
90 if ((ns->parent == cred->user_ns) && uid_eq(ns->owner, cred->euid))
91 return 0;
92
93 /*
94 * If you have a capability in a parent user ns, then you have
95 * it over all children user namespaces as well.
96 */
97 ns = ns->parent;
98 }
99
100 /* We never get here */
101}
102
103/**
104 * cap_settime - Determine whether the current process may set the system clock
105 * @ts: The time to set
106 * @tz: The timezone to set
107 *
108 * Determine whether the current process may set the system clock and timezone
109 * information, returning 0 if permission granted, -ve if denied.
110 */
111int cap_settime(const struct timespec64 *ts, const struct timezone *tz)
112{
113 if (!capable(CAP_SYS_TIME))
114 return -EPERM;
115 return 0;
116}
117
118/**
119 * cap_ptrace_access_check - Determine whether the current process may access
120 * another
121 * @child: The process to be accessed
122 * @mode: The mode of attachment.
123 *
124 * If we are in the same or an ancestor user_ns and have all the target
125 * task's capabilities, then ptrace access is allowed.
126 * If we have the ptrace capability to the target user_ns, then ptrace
127 * access is allowed.
128 * Else denied.
129 *
130 * Determine whether a process may access another, returning 0 if permission
131 * granted, -ve if denied.
132 */
133int cap_ptrace_access_check(struct task_struct *child, unsigned int mode)
134{
135 int ret = 0;
136 const struct cred *cred, *child_cred;
137 const kernel_cap_t *caller_caps;
138
139 rcu_read_lock();
140 cred = current_cred();
141 child_cred = __task_cred(child);
142 if (mode & PTRACE_MODE_FSCREDS)
143 caller_caps = &cred->cap_effective;
144 else
145 caller_caps = &cred->cap_permitted;
146 if (cred->user_ns == child_cred->user_ns &&
147 cap_issubset(child_cred->cap_permitted, *caller_caps))
148 goto out;
149 if (ns_capable(child_cred->user_ns, CAP_SYS_PTRACE))
150 goto out;
151 ret = -EPERM;
152out:
153 rcu_read_unlock();
154 return ret;
155}
156
157/**
158 * cap_ptrace_traceme - Determine whether another process may trace the current
159 * @parent: The task proposed to be the tracer
160 *
161 * If parent is in the same or an ancestor user_ns and has all current's
162 * capabilities, then ptrace access is allowed.
163 * If parent has the ptrace capability to current's user_ns, then ptrace
164 * access is allowed.
165 * Else denied.
166 *
167 * Determine whether the nominated task is permitted to trace the current
168 * process, returning 0 if permission is granted, -ve if denied.
169 */
170int cap_ptrace_traceme(struct task_struct *parent)
171{
172 int ret = 0;
173 const struct cred *cred, *child_cred;
174
175 rcu_read_lock();
176 cred = __task_cred(parent);
177 child_cred = current_cred();
178 if (cred->user_ns == child_cred->user_ns &&
179 cap_issubset(child_cred->cap_permitted, cred->cap_permitted))
180 goto out;
181 if (has_ns_capability(parent, child_cred->user_ns, CAP_SYS_PTRACE))
182 goto out;
183 ret = -EPERM;
184out:
185 rcu_read_unlock();
186 return ret;
187}
188
189/**
190 * cap_capget - Retrieve a task's capability sets
191 * @target: The task from which to retrieve the capability sets
192 * @effective: The place to record the effective set
193 * @inheritable: The place to record the inheritable set
194 * @permitted: The place to record the permitted set
195 *
196 * This function retrieves the capabilities of the nominated task and returns
197 * them to the caller.
198 */
199int cap_capget(struct task_struct *target, kernel_cap_t *effective,
200 kernel_cap_t *inheritable, kernel_cap_t *permitted)
201{
202 const struct cred *cred;
203
204 /* Derived from kernel/capability.c:sys_capget. */
205 rcu_read_lock();
206 cred = __task_cred(target);
207 *effective = cred->cap_effective;
208 *inheritable = cred->cap_inheritable;
209 *permitted = cred->cap_permitted;
210 rcu_read_unlock();
211 return 0;
212}
213
214/*
215 * Determine whether the inheritable capabilities are limited to the old
216 * permitted set. Returns 1 if they are limited, 0 if they are not.
217 */
218static inline int cap_inh_is_capped(void)
219{
220 /* they are so limited unless the current task has the CAP_SETPCAP
221 * capability
222 */
223 if (cap_capable(current_cred(), current_cred()->user_ns,
224 CAP_SETPCAP, CAP_OPT_NONE) == 0)
225 return 0;
226 return 1;
227}
228
229/**
230 * cap_capset - Validate and apply proposed changes to current's capabilities
231 * @new: The proposed new credentials; alterations should be made here
232 * @old: The current task's current credentials
233 * @effective: A pointer to the proposed new effective capabilities set
234 * @inheritable: A pointer to the proposed new inheritable capabilities set
235 * @permitted: A pointer to the proposed new permitted capabilities set
236 *
237 * This function validates and applies a proposed mass change to the current
238 * process's capability sets. The changes are made to the proposed new
239 * credentials, and assuming no error, will be committed by the caller of LSM.
240 */
241int cap_capset(struct cred *new,
242 const struct cred *old,
243 const kernel_cap_t *effective,
244 const kernel_cap_t *inheritable,
245 const kernel_cap_t *permitted)
246{
247 if (cap_inh_is_capped() &&
248 !cap_issubset(*inheritable,
249 cap_combine(old->cap_inheritable,
250 old->cap_permitted)))
251 /* incapable of using this inheritable set */
252 return -EPERM;
253
254 if (!cap_issubset(*inheritable,
255 cap_combine(old->cap_inheritable,
256 old->cap_bset)))
257 /* no new pI capabilities outside bounding set */
258 return -EPERM;
259
260 /* verify restrictions on target's new Permitted set */
261 if (!cap_issubset(*permitted, old->cap_permitted))
262 return -EPERM;
263
264 /* verify the _new_Effective_ is a subset of the _new_Permitted_ */
265 if (!cap_issubset(*effective, *permitted))
266 return -EPERM;
267
268 new->cap_effective = *effective;
269 new->cap_inheritable = *inheritable;
270 new->cap_permitted = *permitted;
271
272 /*
273 * Mask off ambient bits that are no longer both permitted and
274 * inheritable.
275 */
276 new->cap_ambient = cap_intersect(new->cap_ambient,
277 cap_intersect(*permitted,
278 *inheritable));
279 if (WARN_ON(!cap_ambient_invariant_ok(new)))
280 return -EINVAL;
281 return 0;
282}
283
284/**
285 * cap_inode_need_killpriv - Determine if inode change affects privileges
286 * @dentry: The inode/dentry in being changed with change marked ATTR_KILL_PRIV
287 *
288 * Determine if an inode having a change applied that's marked ATTR_KILL_PRIV
289 * affects the security markings on that inode, and if it is, should
290 * inode_killpriv() be invoked or the change rejected.
291 *
292 * Return: 1 if security.capability has a value, meaning inode_killpriv()
293 * is required, 0 otherwise, meaning inode_killpriv() is not required.
294 */
295int cap_inode_need_killpriv(struct dentry *dentry)
296{
297 struct inode *inode = d_backing_inode(dentry);
298 int error;
299
300 error = __vfs_getxattr(dentry, inode, XATTR_NAME_CAPS, NULL, 0);
301 return error > 0;
302}
303
304/**
305 * cap_inode_killpriv - Erase the security markings on an inode
306 *
307 * @mnt_userns: user namespace of the mount the inode was found from
308 * @dentry: The inode/dentry to alter
309 *
310 * Erase the privilege-enhancing security markings on an inode.
311 *
312 * If the inode has been found through an idmapped mount the user namespace of
313 * the vfsmount must be passed through @mnt_userns. This function will then
314 * take care to map the inode according to @mnt_userns before checking
315 * permissions. On non-idmapped mounts or if permission checking is to be
316 * performed on the raw inode simply passs init_user_ns.
317 *
318 * Return: 0 if successful, -ve on error.
319 */
320int cap_inode_killpriv(struct user_namespace *mnt_userns, struct dentry *dentry)
321{
322 int error;
323
324 error = __vfs_removexattr(mnt_userns, dentry, XATTR_NAME_CAPS);
325 if (error == -EOPNOTSUPP)
326 error = 0;
327 return error;
328}
329
330static bool rootid_owns_currentns(kuid_t kroot)
331{
332 struct user_namespace *ns;
333
334 if (!uid_valid(kroot))
335 return false;
336
337 for (ns = current_user_ns(); ; ns = ns->parent) {
338 if (from_kuid(ns, kroot) == 0)
339 return true;
340 if (ns == &init_user_ns)
341 break;
342 }
343
344 return false;
345}
346
347static __u32 sansflags(__u32 m)
348{
349 return m & ~VFS_CAP_FLAGS_EFFECTIVE;
350}
351
352static bool is_v2header(size_t size, const struct vfs_cap_data *cap)
353{
354 if (size != XATTR_CAPS_SZ_2)
355 return false;
356 return sansflags(le32_to_cpu(cap->magic_etc)) == VFS_CAP_REVISION_2;
357}
358
359static bool is_v3header(size_t size, const struct vfs_cap_data *cap)
360{
361 if (size != XATTR_CAPS_SZ_3)
362 return false;
363 return sansflags(le32_to_cpu(cap->magic_etc)) == VFS_CAP_REVISION_3;
364}
365
366/*
367 * getsecurity: We are called for security.* before any attempt to read the
368 * xattr from the inode itself.
369 *
370 * This gives us a chance to read the on-disk value and convert it. If we
371 * return -EOPNOTSUPP, then vfs_getxattr() will call the i_op handler.
372 *
373 * Note we are not called by vfs_getxattr_alloc(), but that is only called
374 * by the integrity subsystem, which really wants the unconverted values -
375 * so that's good.
376 */
377int cap_inode_getsecurity(struct user_namespace *mnt_userns,
378 struct inode *inode, const char *name, void **buffer,
379 bool alloc)
380{
381 int size, ret;
382 kuid_t kroot;
383 u32 nsmagic, magic;
384 uid_t root, mappedroot;
385 char *tmpbuf = NULL;
386 struct vfs_cap_data *cap;
387 struct vfs_ns_cap_data *nscap = NULL;
388 struct dentry *dentry;
389 struct user_namespace *fs_ns;
390
391 if (strcmp(name, "capability") != 0)
392 return -EOPNOTSUPP;
393
394 dentry = d_find_any_alias(inode);
395 if (!dentry)
396 return -EINVAL;
397
398 size = sizeof(struct vfs_ns_cap_data);
399 ret = (int)vfs_getxattr_alloc(mnt_userns, dentry, XATTR_NAME_CAPS,
400 &tmpbuf, size, GFP_NOFS);
401 dput(dentry);
402
403 if (ret < 0 || !tmpbuf)
404 return ret;
405
406 fs_ns = inode->i_sb->s_user_ns;
407 cap = (struct vfs_cap_data *) tmpbuf;
408 if (is_v2header((size_t) ret, cap)) {
409 root = 0;
410 } else if (is_v3header((size_t) ret, cap)) {
411 nscap = (struct vfs_ns_cap_data *) tmpbuf;
412 root = le32_to_cpu(nscap->rootid);
413 } else {
414 size = -EINVAL;
415 goto out_free;
416 }
417
418 kroot = make_kuid(fs_ns, root);
419
420 /* If this is an idmapped mount shift the kuid. */
421 kroot = kuid_into_mnt(mnt_userns, kroot);
422
423 /* If the root kuid maps to a valid uid in current ns, then return
424 * this as a nscap. */
425 mappedroot = from_kuid(current_user_ns(), kroot);
426 if (mappedroot != (uid_t)-1 && mappedroot != (uid_t)0) {
427 size = sizeof(struct vfs_ns_cap_data);
428 if (alloc) {
429 if (!nscap) {
430 /* v2 -> v3 conversion */
431 nscap = kzalloc(size, GFP_ATOMIC);
432 if (!nscap) {
433 size = -ENOMEM;
434 goto out_free;
435 }
436 nsmagic = VFS_CAP_REVISION_3;
437 magic = le32_to_cpu(cap->magic_etc);
438 if (magic & VFS_CAP_FLAGS_EFFECTIVE)
439 nsmagic |= VFS_CAP_FLAGS_EFFECTIVE;
440 memcpy(&nscap->data, &cap->data, sizeof(__le32) * 2 * VFS_CAP_U32);
441 nscap->magic_etc = cpu_to_le32(nsmagic);
442 } else {
443 /* use allocated v3 buffer */
444 tmpbuf = NULL;
445 }
446 nscap->rootid = cpu_to_le32(mappedroot);
447 *buffer = nscap;
448 }
449 goto out_free;
450 }
451
452 if (!rootid_owns_currentns(kroot)) {
453 size = -EOVERFLOW;
454 goto out_free;
455 }
456
457 /* This comes from a parent namespace. Return as a v2 capability */
458 size = sizeof(struct vfs_cap_data);
459 if (alloc) {
460 if (nscap) {
461 /* v3 -> v2 conversion */
462 cap = kzalloc(size, GFP_ATOMIC);
463 if (!cap) {
464 size = -ENOMEM;
465 goto out_free;
466 }
467 magic = VFS_CAP_REVISION_2;
468 nsmagic = le32_to_cpu(nscap->magic_etc);
469 if (nsmagic & VFS_CAP_FLAGS_EFFECTIVE)
470 magic |= VFS_CAP_FLAGS_EFFECTIVE;
471 memcpy(&cap->data, &nscap->data, sizeof(__le32) * 2 * VFS_CAP_U32);
472 cap->magic_etc = cpu_to_le32(magic);
473 } else {
474 /* use unconverted v2 */
475 tmpbuf = NULL;
476 }
477 *buffer = cap;
478 }
479out_free:
480 kfree(tmpbuf);
481 return size;
482}
483
484/**
485 * rootid_from_xattr - translate root uid of vfs caps
486 *
487 * @value: vfs caps value which may be modified by this function
488 * @size: size of @ivalue
489 * @task_ns: user namespace of the caller
490 * @mnt_userns: user namespace of the mount the inode was found from
491 *
492 * If the inode has been found through an idmapped mount the user namespace of
493 * the vfsmount must be passed through @mnt_userns. This function will then
494 * take care to map the inode according to @mnt_userns before checking
495 * permissions. On non-idmapped mounts or if permission checking is to be
496 * performed on the raw inode simply passs init_user_ns.
497 */
498static kuid_t rootid_from_xattr(const void *value, size_t size,
499 struct user_namespace *task_ns,
500 struct user_namespace *mnt_userns)
501{
502 const struct vfs_ns_cap_data *nscap = value;
503 kuid_t rootkid;
504 uid_t rootid = 0;
505
506 if (size == XATTR_CAPS_SZ_3)
507 rootid = le32_to_cpu(nscap->rootid);
508
509 rootkid = make_kuid(task_ns, rootid);
510 return kuid_from_mnt(mnt_userns, rootkid);
511}
512
513static bool validheader(size_t size, const struct vfs_cap_data *cap)
514{
515 return is_v2header(size, cap) || is_v3header(size, cap);
516}
517
518/**
519 * cap_convert_nscap - check vfs caps
520 *
521 * @mnt_userns: user namespace of the mount the inode was found from
522 * @dentry: used to retrieve inode to check permissions on
523 * @ivalue: vfs caps value which may be modified by this function
524 * @size: size of @ivalue
525 *
526 * User requested a write of security.capability. If needed, update the
527 * xattr to change from v2 to v3, or to fixup the v3 rootid.
528 *
529 * If the inode has been found through an idmapped mount the user namespace of
530 * the vfsmount must be passed through @mnt_userns. This function will then
531 * take care to map the inode according to @mnt_userns before checking
532 * permissions. On non-idmapped mounts or if permission checking is to be
533 * performed on the raw inode simply passs init_user_ns.
534 *
535 * Return: On success, return the new size; on error, return < 0.
536 */
537int cap_convert_nscap(struct user_namespace *mnt_userns, struct dentry *dentry,
538 const void **ivalue, size_t size)
539{
540 struct vfs_ns_cap_data *nscap;
541 uid_t nsrootid;
542 const struct vfs_cap_data *cap = *ivalue;
543 __u32 magic, nsmagic;
544 struct inode *inode = d_backing_inode(dentry);
545 struct user_namespace *task_ns = current_user_ns(),
546 *fs_ns = inode->i_sb->s_user_ns;
547 kuid_t rootid;
548 size_t newsize;
549
550 if (!*ivalue)
551 return -EINVAL;
552 if (!validheader(size, cap))
553 return -EINVAL;
554 if (!capable_wrt_inode_uidgid(mnt_userns, inode, CAP_SETFCAP))
555 return -EPERM;
556 if (size == XATTR_CAPS_SZ_2 && (mnt_userns == &init_user_ns))
557 if (ns_capable(inode->i_sb->s_user_ns, CAP_SETFCAP))
558 /* user is privileged, just write the v2 */
559 return size;
560
561 rootid = rootid_from_xattr(*ivalue, size, task_ns, mnt_userns);
562 if (!uid_valid(rootid))
563 return -EINVAL;
564
565 nsrootid = from_kuid(fs_ns, rootid);
566 if (nsrootid == -1)
567 return -EINVAL;
568
569 newsize = sizeof(struct vfs_ns_cap_data);
570 nscap = kmalloc(newsize, GFP_ATOMIC);
571 if (!nscap)
572 return -ENOMEM;
573 nscap->rootid = cpu_to_le32(nsrootid);
574 nsmagic = VFS_CAP_REVISION_3;
575 magic = le32_to_cpu(cap->magic_etc);
576 if (magic & VFS_CAP_FLAGS_EFFECTIVE)
577 nsmagic |= VFS_CAP_FLAGS_EFFECTIVE;
578 nscap->magic_etc = cpu_to_le32(nsmagic);
579 memcpy(&nscap->data, &cap->data, sizeof(__le32) * 2 * VFS_CAP_U32);
580
581 *ivalue = nscap;
582 return newsize;
583}
584
585/*
586 * Calculate the new process capability sets from the capability sets attached
587 * to a file.
588 */
589static inline int bprm_caps_from_vfs_caps(struct cpu_vfs_cap_data *caps,
590 struct linux_binprm *bprm,
591 bool *effective,
592 bool *has_fcap)
593{
594 struct cred *new = bprm->cred;
595 unsigned i;
596 int ret = 0;
597
598 if (caps->magic_etc & VFS_CAP_FLAGS_EFFECTIVE)
599 *effective = true;
600
601 if (caps->magic_etc & VFS_CAP_REVISION_MASK)
602 *has_fcap = true;
603
604 CAP_FOR_EACH_U32(i) {
605 __u32 permitted = caps->permitted.cap[i];
606 __u32 inheritable = caps->inheritable.cap[i];
607
608 /*
609 * pP' = (X & fP) | (pI & fI)
610 * The addition of pA' is handled later.
611 */
612 new->cap_permitted.cap[i] =
613 (new->cap_bset.cap[i] & permitted) |
614 (new->cap_inheritable.cap[i] & inheritable);
615
616 if (permitted & ~new->cap_permitted.cap[i])
617 /* insufficient to execute correctly */
618 ret = -EPERM;
619 }
620
621 /*
622 * For legacy apps, with no internal support for recognizing they
623 * do not have enough capabilities, we return an error if they are
624 * missing some "forced" (aka file-permitted) capabilities.
625 */
626 return *effective ? ret : 0;
627}
628
629/**
630 * get_vfs_caps_from_disk - retrieve vfs caps from disk
631 *
632 * @mnt_userns: user namespace of the mount the inode was found from
633 * @dentry: dentry from which @inode is retrieved
634 * @cpu_caps: vfs capabilities
635 *
636 * Extract the on-exec-apply capability sets for an executable file.
637 *
638 * If the inode has been found through an idmapped mount the user namespace of
639 * the vfsmount must be passed through @mnt_userns. This function will then
640 * take care to map the inode according to @mnt_userns before checking
641 * permissions. On non-idmapped mounts or if permission checking is to be
642 * performed on the raw inode simply passs init_user_ns.
643 */
644int get_vfs_caps_from_disk(struct user_namespace *mnt_userns,
645 const struct dentry *dentry,
646 struct cpu_vfs_cap_data *cpu_caps)
647{
648 struct inode *inode = d_backing_inode(dentry);
649 __u32 magic_etc;
650 unsigned tocopy, i;
651 int size;
652 struct vfs_ns_cap_data data, *nscaps = &data;
653 struct vfs_cap_data *caps = (struct vfs_cap_data *) &data;
654 kuid_t rootkuid;
655 struct user_namespace *fs_ns;
656
657 memset(cpu_caps, 0, sizeof(struct cpu_vfs_cap_data));
658
659 if (!inode)
660 return -ENODATA;
661
662 fs_ns = inode->i_sb->s_user_ns;
663 size = __vfs_getxattr((struct dentry *)dentry, inode,
664 XATTR_NAME_CAPS, &data, XATTR_CAPS_SZ);
665 if (size == -ENODATA || size == -EOPNOTSUPP)
666 /* no data, that's ok */
667 return -ENODATA;
668
669 if (size < 0)
670 return size;
671
672 if (size < sizeof(magic_etc))
673 return -EINVAL;
674
675 cpu_caps->magic_etc = magic_etc = le32_to_cpu(caps->magic_etc);
676
677 rootkuid = make_kuid(fs_ns, 0);
678 switch (magic_etc & VFS_CAP_REVISION_MASK) {
679 case VFS_CAP_REVISION_1:
680 if (size != XATTR_CAPS_SZ_1)
681 return -EINVAL;
682 tocopy = VFS_CAP_U32_1;
683 break;
684 case VFS_CAP_REVISION_2:
685 if (size != XATTR_CAPS_SZ_2)
686 return -EINVAL;
687 tocopy = VFS_CAP_U32_2;
688 break;
689 case VFS_CAP_REVISION_3:
690 if (size != XATTR_CAPS_SZ_3)
691 return -EINVAL;
692 tocopy = VFS_CAP_U32_3;
693 rootkuid = make_kuid(fs_ns, le32_to_cpu(nscaps->rootid));
694 break;
695
696 default:
697 return -EINVAL;
698 }
699 /* Limit the caps to the mounter of the filesystem
700 * or the more limited uid specified in the xattr.
701 */
702 rootkuid = kuid_into_mnt(mnt_userns, rootkuid);
703 if (!rootid_owns_currentns(rootkuid))
704 return -ENODATA;
705
706 CAP_FOR_EACH_U32(i) {
707 if (i >= tocopy)
708 break;
709 cpu_caps->permitted.cap[i] = le32_to_cpu(caps->data[i].permitted);
710 cpu_caps->inheritable.cap[i] = le32_to_cpu(caps->data[i].inheritable);
711 }
712
713 cpu_caps->permitted.cap[CAP_LAST_U32] &= CAP_LAST_U32_VALID_MASK;
714 cpu_caps->inheritable.cap[CAP_LAST_U32] &= CAP_LAST_U32_VALID_MASK;
715
716 cpu_caps->rootid = rootkuid;
717
718 return 0;
719}
720
721/*
722 * Attempt to get the on-exec apply capability sets for an executable file from
723 * its xattrs and, if present, apply them to the proposed credentials being
724 * constructed by execve().
725 */
726static int get_file_caps(struct linux_binprm *bprm, struct file *file,
727 bool *effective, bool *has_fcap)
728{
729 int rc = 0;
730 struct cpu_vfs_cap_data vcaps;
731
732 cap_clear(bprm->cred->cap_permitted);
733
734 if (!file_caps_enabled)
735 return 0;
736
737 if (!mnt_may_suid(file->f_path.mnt))
738 return 0;
739
740 /*
741 * This check is redundant with mnt_may_suid() but is kept to make
742 * explicit that capability bits are limited to s_user_ns and its
743 * descendants.
744 */
745 if (!current_in_userns(file->f_path.mnt->mnt_sb->s_user_ns))
746 return 0;
747
748 rc = get_vfs_caps_from_disk(file_mnt_user_ns(file),
749 file->f_path.dentry, &vcaps);
750 if (rc < 0) {
751 if (rc == -EINVAL)
752 printk(KERN_NOTICE "Invalid argument reading file caps for %s\n",
753 bprm->filename);
754 else if (rc == -ENODATA)
755 rc = 0;
756 goto out;
757 }
758
759 rc = bprm_caps_from_vfs_caps(&vcaps, bprm, effective, has_fcap);
760
761out:
762 if (rc)
763 cap_clear(bprm->cred->cap_permitted);
764
765 return rc;
766}
767
768static inline bool root_privileged(void) { return !issecure(SECURE_NOROOT); }
769
770static inline bool __is_real(kuid_t uid, struct cred *cred)
771{ return uid_eq(cred->uid, uid); }
772
773static inline bool __is_eff(kuid_t uid, struct cred *cred)
774{ return uid_eq(cred->euid, uid); }
775
776static inline bool __is_suid(kuid_t uid, struct cred *cred)
777{ return !__is_real(uid, cred) && __is_eff(uid, cred); }
778
779/*
780 * handle_privileged_root - Handle case of privileged root
781 * @bprm: The execution parameters, including the proposed creds
782 * @has_fcap: Are any file capabilities set?
783 * @effective: Do we have effective root privilege?
784 * @root_uid: This namespace' root UID WRT initial USER namespace
785 *
786 * Handle the case where root is privileged and hasn't been neutered by
787 * SECURE_NOROOT. If file capabilities are set, they won't be combined with
788 * set UID root and nothing is changed. If we are root, cap_permitted is
789 * updated. If we have become set UID root, the effective bit is set.
790 */
791static void handle_privileged_root(struct linux_binprm *bprm, bool has_fcap,
792 bool *effective, kuid_t root_uid)
793{
794 const struct cred *old = current_cred();
795 struct cred *new = bprm->cred;
796
797 if (!root_privileged())
798 return;
799 /*
800 * If the legacy file capability is set, then don't set privs
801 * for a setuid root binary run by a non-root user. Do set it
802 * for a root user just to cause least surprise to an admin.
803 */
804 if (has_fcap && __is_suid(root_uid, new)) {
805 warn_setuid_and_fcaps_mixed(bprm->filename);
806 return;
807 }
808 /*
809 * To support inheritance of root-permissions and suid-root
810 * executables under compatibility mode, we override the
811 * capability sets for the file.
812 */
813 if (__is_eff(root_uid, new) || __is_real(root_uid, new)) {
814 /* pP' = (cap_bset & ~0) | (pI & ~0) */
815 new->cap_permitted = cap_combine(old->cap_bset,
816 old->cap_inheritable);
817 }
818 /*
819 * If only the real uid is 0, we do not set the effective bit.
820 */
821 if (__is_eff(root_uid, new))
822 *effective = true;
823}
824
825#define __cap_gained(field, target, source) \
826 !cap_issubset(target->cap_##field, source->cap_##field)
827#define __cap_grew(target, source, cred) \
828 !cap_issubset(cred->cap_##target, cred->cap_##source)
829#define __cap_full(field, cred) \
830 cap_issubset(CAP_FULL_SET, cred->cap_##field)
831
832static inline bool __is_setuid(struct cred *new, const struct cred *old)
833{ return !uid_eq(new->euid, old->uid); }
834
835static inline bool __is_setgid(struct cred *new, const struct cred *old)
836{ return !gid_eq(new->egid, old->gid); }
837
838/*
839 * 1) Audit candidate if current->cap_effective is set
840 *
841 * We do not bother to audit if 3 things are true:
842 * 1) cap_effective has all caps
843 * 2) we became root *OR* are were already root
844 * 3) root is supposed to have all caps (SECURE_NOROOT)
845 * Since this is just a normal root execing a process.
846 *
847 * Number 1 above might fail if you don't have a full bset, but I think
848 * that is interesting information to audit.
849 *
850 * A number of other conditions require logging:
851 * 2) something prevented setuid root getting all caps
852 * 3) non-setuid root gets fcaps
853 * 4) non-setuid root gets ambient
854 */
855static inline bool nonroot_raised_pE(struct cred *new, const struct cred *old,
856 kuid_t root, bool has_fcap)
857{
858 bool ret = false;
859
860 if ((__cap_grew(effective, ambient, new) &&
861 !(__cap_full(effective, new) &&
862 (__is_eff(root, new) || __is_real(root, new)) &&
863 root_privileged())) ||
864 (root_privileged() &&
865 __is_suid(root, new) &&
866 !__cap_full(effective, new)) ||
867 (!__is_setuid(new, old) &&
868 ((has_fcap &&
869 __cap_gained(permitted, new, old)) ||
870 __cap_gained(ambient, new, old))))
871
872 ret = true;
873
874 return ret;
875}
876
877/**
878 * cap_bprm_creds_from_file - Set up the proposed credentials for execve().
879 * @bprm: The execution parameters, including the proposed creds
880 * @file: The file to pull the credentials from
881 *
882 * Set up the proposed credentials for a new execution context being
883 * constructed by execve(). The proposed creds in @bprm->cred is altered,
884 * which won't take effect immediately.
885 *
886 * Return: 0 if successful, -ve on error.
887 */
888int cap_bprm_creds_from_file(struct linux_binprm *bprm, struct file *file)
889{
890 /* Process setpcap binaries and capabilities for uid 0 */
891 const struct cred *old = current_cred();
892 struct cred *new = bprm->cred;
893 bool effective = false, has_fcap = false, is_setid;
894 int ret;
895 kuid_t root_uid;
896
897 if (WARN_ON(!cap_ambient_invariant_ok(old)))
898 return -EPERM;
899
900 ret = get_file_caps(bprm, file, &effective, &has_fcap);
901 if (ret < 0)
902 return ret;
903
904 root_uid = make_kuid(new->user_ns, 0);
905
906 handle_privileged_root(bprm, has_fcap, &effective, root_uid);
907
908 /* if we have fs caps, clear dangerous personality flags */
909 if (__cap_gained(permitted, new, old))
910 bprm->per_clear |= PER_CLEAR_ON_SETID;
911
912 /* Don't let someone trace a set[ug]id/setpcap binary with the revised
913 * credentials unless they have the appropriate permit.
914 *
915 * In addition, if NO_NEW_PRIVS, then ensure we get no new privs.
916 */
917 is_setid = __is_setuid(new, old) || __is_setgid(new, old);
918
919 if ((is_setid || __cap_gained(permitted, new, old)) &&
920 ((bprm->unsafe & ~LSM_UNSAFE_PTRACE) ||
921 !ptracer_capable(current, new->user_ns))) {
922 /* downgrade; they get no more than they had, and maybe less */
923 if (!ns_capable(new->user_ns, CAP_SETUID) ||
924 (bprm->unsafe & LSM_UNSAFE_NO_NEW_PRIVS)) {
925 new->euid = new->uid;
926 new->egid = new->gid;
927 }
928 new->cap_permitted = cap_intersect(new->cap_permitted,
929 old->cap_permitted);
930 }
931
932 new->suid = new->fsuid = new->euid;
933 new->sgid = new->fsgid = new->egid;
934
935 /* File caps or setid cancels ambient. */
936 if (has_fcap || is_setid)
937 cap_clear(new->cap_ambient);
938
939 /*
940 * Now that we've computed pA', update pP' to give:
941 * pP' = (X & fP) | (pI & fI) | pA'
942 */
943 new->cap_permitted = cap_combine(new->cap_permitted, new->cap_ambient);
944
945 /*
946 * Set pE' = (fE ? pP' : pA'). Because pA' is zero if fE is set,
947 * this is the same as pE' = (fE ? pP' : 0) | pA'.
948 */
949 if (effective)
950 new->cap_effective = new->cap_permitted;
951 else
952 new->cap_effective = new->cap_ambient;
953
954 if (WARN_ON(!cap_ambient_invariant_ok(new)))
955 return -EPERM;
956
957 if (nonroot_raised_pE(new, old, root_uid, has_fcap)) {
958 ret = audit_log_bprm_fcaps(bprm, new, old);
959 if (ret < 0)
960 return ret;
961 }
962
963 new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS);
964
965 if (WARN_ON(!cap_ambient_invariant_ok(new)))
966 return -EPERM;
967
968 /* Check for privilege-elevated exec. */
969 if (is_setid ||
970 (!__is_real(root_uid, new) &&
971 (effective ||
972 __cap_grew(permitted, ambient, new))))
973 bprm->secureexec = 1;
974
975 return 0;
976}
977
978/**
979 * cap_inode_setxattr - Determine whether an xattr may be altered
980 * @dentry: The inode/dentry being altered
981 * @name: The name of the xattr to be changed
982 * @value: The value that the xattr will be changed to
983 * @size: The size of value
984 * @flags: The replacement flag
985 *
986 * Determine whether an xattr may be altered or set on an inode, returning 0 if
987 * permission is granted, -ve if denied.
988 *
989 * This is used to make sure security xattrs don't get updated or set by those
990 * who aren't privileged to do so.
991 */
992int cap_inode_setxattr(struct dentry *dentry, const char *name,
993 const void *value, size_t size, int flags)
994{
995 struct user_namespace *user_ns = dentry->d_sb->s_user_ns;
996
997 /* Ignore non-security xattrs */
998 if (strncmp(name, XATTR_SECURITY_PREFIX,
999 XATTR_SECURITY_PREFIX_LEN) != 0)
1000 return 0;
1001
1002 /*
1003 * For XATTR_NAME_CAPS the check will be done in
1004 * cap_convert_nscap(), called by setxattr()
1005 */
1006 if (strcmp(name, XATTR_NAME_CAPS) == 0)
1007 return 0;
1008
1009 if (!ns_capable(user_ns, CAP_SYS_ADMIN))
1010 return -EPERM;
1011 return 0;
1012}
1013
1014/**
1015 * cap_inode_removexattr - Determine whether an xattr may be removed
1016 *
1017 * @mnt_userns: User namespace of the mount the inode was found from
1018 * @dentry: The inode/dentry being altered
1019 * @name: The name of the xattr to be changed
1020 *
1021 * Determine whether an xattr may be removed from an inode, returning 0 if
1022 * permission is granted, -ve if denied.
1023 *
1024 * If the inode has been found through an idmapped mount the user namespace of
1025 * the vfsmount must be passed through @mnt_userns. This function will then
1026 * take care to map the inode according to @mnt_userns before checking
1027 * permissions. On non-idmapped mounts or if permission checking is to be
1028 * performed on the raw inode simply passs init_user_ns.
1029 *
1030 * This is used to make sure security xattrs don't get removed by those who
1031 * aren't privileged to remove them.
1032 */
1033int cap_inode_removexattr(struct user_namespace *mnt_userns,
1034 struct dentry *dentry, const char *name)
1035{
1036 struct user_namespace *user_ns = dentry->d_sb->s_user_ns;
1037
1038 /* Ignore non-security xattrs */
1039 if (strncmp(name, XATTR_SECURITY_PREFIX,
1040 XATTR_SECURITY_PREFIX_LEN) != 0)
1041 return 0;
1042
1043 if (strcmp(name, XATTR_NAME_CAPS) == 0) {
1044 /* security.capability gets namespaced */
1045 struct inode *inode = d_backing_inode(dentry);
1046 if (!inode)
1047 return -EINVAL;
1048 if (!capable_wrt_inode_uidgid(mnt_userns, inode, CAP_SETFCAP))
1049 return -EPERM;
1050 return 0;
1051 }
1052
1053 if (!ns_capable(user_ns, CAP_SYS_ADMIN))
1054 return -EPERM;
1055 return 0;
1056}
1057
1058/*
1059 * cap_emulate_setxuid() fixes the effective / permitted capabilities of
1060 * a process after a call to setuid, setreuid, or setresuid.
1061 *
1062 * 1) When set*uiding _from_ one of {r,e,s}uid == 0 _to_ all of
1063 * {r,e,s}uid != 0, the permitted and effective capabilities are
1064 * cleared.
1065 *
1066 * 2) When set*uiding _from_ euid == 0 _to_ euid != 0, the effective
1067 * capabilities of the process are cleared.
1068 *
1069 * 3) When set*uiding _from_ euid != 0 _to_ euid == 0, the effective
1070 * capabilities are set to the permitted capabilities.
1071 *
1072 * fsuid is handled elsewhere. fsuid == 0 and {r,e,s}uid!= 0 should
1073 * never happen.
1074 *
1075 * -astor
1076 *
1077 * cevans - New behaviour, Oct '99
1078 * A process may, via prctl(), elect to keep its capabilities when it
1079 * calls setuid() and switches away from uid==0. Both permitted and
1080 * effective sets will be retained.
1081 * Without this change, it was impossible for a daemon to drop only some
1082 * of its privilege. The call to setuid(!=0) would drop all privileges!
1083 * Keeping uid 0 is not an option because uid 0 owns too many vital
1084 * files..
1085 * Thanks to Olaf Kirch and Peter Benie for spotting this.
1086 */
1087static inline void cap_emulate_setxuid(struct cred *new, const struct cred *old)
1088{
1089 kuid_t root_uid = make_kuid(old->user_ns, 0);
1090
1091 if ((uid_eq(old->uid, root_uid) ||
1092 uid_eq(old->euid, root_uid) ||
1093 uid_eq(old->suid, root_uid)) &&
1094 (!uid_eq(new->uid, root_uid) &&
1095 !uid_eq(new->euid, root_uid) &&
1096 !uid_eq(new->suid, root_uid))) {
1097 if (!issecure(SECURE_KEEP_CAPS)) {
1098 cap_clear(new->cap_permitted);
1099 cap_clear(new->cap_effective);
1100 }
1101
1102 /*
1103 * Pre-ambient programs expect setresuid to nonroot followed
1104 * by exec to drop capabilities. We should make sure that
1105 * this remains the case.
1106 */
1107 cap_clear(new->cap_ambient);
1108 }
1109 if (uid_eq(old->euid, root_uid) && !uid_eq(new->euid, root_uid))
1110 cap_clear(new->cap_effective);
1111 if (!uid_eq(old->euid, root_uid) && uid_eq(new->euid, root_uid))
1112 new->cap_effective = new->cap_permitted;
1113}
1114
1115/**
1116 * cap_task_fix_setuid - Fix up the results of setuid() call
1117 * @new: The proposed credentials
1118 * @old: The current task's current credentials
1119 * @flags: Indications of what has changed
1120 *
1121 * Fix up the results of setuid() call before the credential changes are
1122 * actually applied.
1123 *
1124 * Return: 0 to grant the changes, -ve to deny them.
1125 */
1126int cap_task_fix_setuid(struct cred *new, const struct cred *old, int flags)
1127{
1128 switch (flags) {
1129 case LSM_SETID_RE:
1130 case LSM_SETID_ID:
1131 case LSM_SETID_RES:
1132 /* juggle the capabilities to follow [RES]UID changes unless
1133 * otherwise suppressed */
1134 if (!issecure(SECURE_NO_SETUID_FIXUP))
1135 cap_emulate_setxuid(new, old);
1136 break;
1137
1138 case LSM_SETID_FS:
1139 /* juggle the capabilties to follow FSUID changes, unless
1140 * otherwise suppressed
1141 *
1142 * FIXME - is fsuser used for all CAP_FS_MASK capabilities?
1143 * if not, we might be a bit too harsh here.
1144 */
1145 if (!issecure(SECURE_NO_SETUID_FIXUP)) {
1146 kuid_t root_uid = make_kuid(old->user_ns, 0);
1147 if (uid_eq(old->fsuid, root_uid) && !uid_eq(new->fsuid, root_uid))
1148 new->cap_effective =
1149 cap_drop_fs_set(new->cap_effective);
1150
1151 if (!uid_eq(old->fsuid, root_uid) && uid_eq(new->fsuid, root_uid))
1152 new->cap_effective =
1153 cap_raise_fs_set(new->cap_effective,
1154 new->cap_permitted);
1155 }
1156 break;
1157
1158 default:
1159 return -EINVAL;
1160 }
1161
1162 return 0;
1163}
1164
1165/*
1166 * Rationale: code calling task_setscheduler, task_setioprio, and
1167 * task_setnice, assumes that
1168 * . if capable(cap_sys_nice), then those actions should be allowed
1169 * . if not capable(cap_sys_nice), but acting on your own processes,
1170 * then those actions should be allowed
1171 * This is insufficient now since you can call code without suid, but
1172 * yet with increased caps.
1173 * So we check for increased caps on the target process.
1174 */
1175static int cap_safe_nice(struct task_struct *p)
1176{
1177 int is_subset, ret = 0;
1178
1179 rcu_read_lock();
1180 is_subset = cap_issubset(__task_cred(p)->cap_permitted,
1181 current_cred()->cap_permitted);
1182 if (!is_subset && !ns_capable(__task_cred(p)->user_ns, CAP_SYS_NICE))
1183 ret = -EPERM;
1184 rcu_read_unlock();
1185
1186 return ret;
1187}
1188
1189/**
1190 * cap_task_setscheduler - Detemine if scheduler policy change is permitted
1191 * @p: The task to affect
1192 *
1193 * Detemine if the requested scheduler policy change is permitted for the
1194 * specified task.
1195 *
1196 * Return: 0 if permission is granted, -ve if denied.
1197 */
1198int cap_task_setscheduler(struct task_struct *p)
1199{
1200 return cap_safe_nice(p);
1201}
1202
1203/**
1204 * cap_task_setioprio - Detemine if I/O priority change is permitted
1205 * @p: The task to affect
1206 * @ioprio: The I/O priority to set
1207 *
1208 * Detemine if the requested I/O priority change is permitted for the specified
1209 * task.
1210 *
1211 * Return: 0 if permission is granted, -ve if denied.
1212 */
1213int cap_task_setioprio(struct task_struct *p, int ioprio)
1214{
1215 return cap_safe_nice(p);
1216}
1217
1218/**
1219 * cap_task_setnice - Detemine if task priority change is permitted
1220 * @p: The task to affect
1221 * @nice: The nice value to set
1222 *
1223 * Detemine if the requested task priority change is permitted for the
1224 * specified task.
1225 *
1226 * Return: 0 if permission is granted, -ve if denied.
1227 */
1228int cap_task_setnice(struct task_struct *p, int nice)
1229{
1230 return cap_safe_nice(p);
1231}
1232
1233/*
1234 * Implement PR_CAPBSET_DROP. Attempt to remove the specified capability from
1235 * the current task's bounding set. Returns 0 on success, -ve on error.
1236 */
1237static int cap_prctl_drop(unsigned long cap)
1238{
1239 struct cred *new;
1240
1241 if (!ns_capable(current_user_ns(), CAP_SETPCAP))
1242 return -EPERM;
1243 if (!cap_valid(cap))
1244 return -EINVAL;
1245
1246 new = prepare_creds();
1247 if (!new)
1248 return -ENOMEM;
1249 cap_lower(new->cap_bset, cap);
1250 return commit_creds(new);
1251}
1252
1253/**
1254 * cap_task_prctl - Implement process control functions for this security module
1255 * @option: The process control function requested
1256 * @arg2: The argument data for this function
1257 * @arg3: The argument data for this function
1258 * @arg4: The argument data for this function
1259 * @arg5: The argument data for this function
1260 *
1261 * Allow process control functions (sys_prctl()) to alter capabilities; may
1262 * also deny access to other functions not otherwise implemented here.
1263 *
1264 * Return: 0 or +ve on success, -ENOSYS if this function is not implemented
1265 * here, other -ve on error. If -ENOSYS is returned, sys_prctl() and other LSM
1266 * modules will consider performing the function.
1267 */
1268int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3,
1269 unsigned long arg4, unsigned long arg5)
1270{
1271 const struct cred *old = current_cred();
1272 struct cred *new;
1273
1274 switch (option) {
1275 case PR_CAPBSET_READ:
1276 if (!cap_valid(arg2))
1277 return -EINVAL;
1278 return !!cap_raised(old->cap_bset, arg2);
1279
1280 case PR_CAPBSET_DROP:
1281 return cap_prctl_drop(arg2);
1282
1283 /*
1284 * The next four prctl's remain to assist with transitioning a
1285 * system from legacy UID=0 based privilege (when filesystem
1286 * capabilities are not in use) to a system using filesystem
1287 * capabilities only - as the POSIX.1e draft intended.
1288 *
1289 * Note:
1290 *
1291 * PR_SET_SECUREBITS =
1292 * issecure_mask(SECURE_KEEP_CAPS_LOCKED)
1293 * | issecure_mask(SECURE_NOROOT)
1294 * | issecure_mask(SECURE_NOROOT_LOCKED)
1295 * | issecure_mask(SECURE_NO_SETUID_FIXUP)
1296 * | issecure_mask(SECURE_NO_SETUID_FIXUP_LOCKED)
1297 *
1298 * will ensure that the current process and all of its
1299 * children will be locked into a pure
1300 * capability-based-privilege environment.
1301 */
1302 case PR_SET_SECUREBITS:
1303 if ((((old->securebits & SECURE_ALL_LOCKS) >> 1)
1304 & (old->securebits ^ arg2)) /*[1]*/
1305 || ((old->securebits & SECURE_ALL_LOCKS & ~arg2)) /*[2]*/
1306 || (arg2 & ~(SECURE_ALL_LOCKS | SECURE_ALL_BITS)) /*[3]*/
1307 || (cap_capable(current_cred(),
1308 current_cred()->user_ns,
1309 CAP_SETPCAP,
1310 CAP_OPT_NONE) != 0) /*[4]*/
1311 /*
1312 * [1] no changing of bits that are locked
1313 * [2] no unlocking of locks
1314 * [3] no setting of unsupported bits
1315 * [4] doing anything requires privilege (go read about
1316 * the "sendmail capabilities bug")
1317 */
1318 )
1319 /* cannot change a locked bit */
1320 return -EPERM;
1321
1322 new = prepare_creds();
1323 if (!new)
1324 return -ENOMEM;
1325 new->securebits = arg2;
1326 return commit_creds(new);
1327
1328 case PR_GET_SECUREBITS:
1329 return old->securebits;
1330
1331 case PR_GET_KEEPCAPS:
1332 return !!issecure(SECURE_KEEP_CAPS);
1333
1334 case PR_SET_KEEPCAPS:
1335 if (arg2 > 1) /* Note, we rely on arg2 being unsigned here */
1336 return -EINVAL;
1337 if (issecure(SECURE_KEEP_CAPS_LOCKED))
1338 return -EPERM;
1339
1340 new = prepare_creds();
1341 if (!new)
1342 return -ENOMEM;
1343 if (arg2)
1344 new->securebits |= issecure_mask(SECURE_KEEP_CAPS);
1345 else
1346 new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS);
1347 return commit_creds(new);
1348
1349 case PR_CAP_AMBIENT:
1350 if (arg2 == PR_CAP_AMBIENT_CLEAR_ALL) {
1351 if (arg3 | arg4 | arg5)
1352 return -EINVAL;
1353
1354 new = prepare_creds();
1355 if (!new)
1356 return -ENOMEM;
1357 cap_clear(new->cap_ambient);
1358 return commit_creds(new);
1359 }
1360
1361 if (((!cap_valid(arg3)) | arg4 | arg5))
1362 return -EINVAL;
1363
1364 if (arg2 == PR_CAP_AMBIENT_IS_SET) {
1365 return !!cap_raised(current_cred()->cap_ambient, arg3);
1366 } else if (arg2 != PR_CAP_AMBIENT_RAISE &&
1367 arg2 != PR_CAP_AMBIENT_LOWER) {
1368 return -EINVAL;
1369 } else {
1370 if (arg2 == PR_CAP_AMBIENT_RAISE &&
1371 (!cap_raised(current_cred()->cap_permitted, arg3) ||
1372 !cap_raised(current_cred()->cap_inheritable,
1373 arg3) ||
1374 issecure(SECURE_NO_CAP_AMBIENT_RAISE)))
1375 return -EPERM;
1376
1377 new = prepare_creds();
1378 if (!new)
1379 return -ENOMEM;
1380 if (arg2 == PR_CAP_AMBIENT_RAISE)
1381 cap_raise(new->cap_ambient, arg3);
1382 else
1383 cap_lower(new->cap_ambient, arg3);
1384 return commit_creds(new);
1385 }
1386
1387 default:
1388 /* No functionality available - continue with default */
1389 return -ENOSYS;
1390 }
1391}
1392
1393/**
1394 * cap_vm_enough_memory - Determine whether a new virtual mapping is permitted
1395 * @mm: The VM space in which the new mapping is to be made
1396 * @pages: The size of the mapping
1397 *
1398 * Determine whether the allocation of a new virtual mapping by the current
1399 * task is permitted.
1400 *
1401 * Return: 1 if permission is granted, 0 if not.
1402 */
1403int cap_vm_enough_memory(struct mm_struct *mm, long pages)
1404{
1405 int cap_sys_admin = 0;
1406
1407 if (cap_capable(current_cred(), &init_user_ns,
1408 CAP_SYS_ADMIN, CAP_OPT_NOAUDIT) == 0)
1409 cap_sys_admin = 1;
1410
1411 return cap_sys_admin;
1412}
1413
1414/**
1415 * cap_mmap_addr - check if able to map given addr
1416 * @addr: address attempting to be mapped
1417 *
1418 * If the process is attempting to map memory below dac_mmap_min_addr they need
1419 * CAP_SYS_RAWIO. The other parameters to this function are unused by the
1420 * capability security module.
1421 *
1422 * Return: 0 if this mapping should be allowed or -EPERM if not.
1423 */
1424int cap_mmap_addr(unsigned long addr)
1425{
1426 int ret = 0;
1427
1428 if (addr < dac_mmap_min_addr) {
1429 ret = cap_capable(current_cred(), &init_user_ns, CAP_SYS_RAWIO,
1430 CAP_OPT_NONE);
1431 /* set PF_SUPERPRIV if it turns out we allow the low mmap */
1432 if (ret == 0)
1433 current->flags |= PF_SUPERPRIV;
1434 }
1435 return ret;
1436}
1437
1438int cap_mmap_file(struct file *file, unsigned long reqprot,
1439 unsigned long prot, unsigned long flags)
1440{
1441 return 0;
1442}
1443
1444#ifdef CONFIG_SECURITY
1445
1446static struct security_hook_list capability_hooks[] __lsm_ro_after_init = {
1447 LSM_HOOK_INIT(capable, cap_capable),
1448 LSM_HOOK_INIT(settime, cap_settime),
1449 LSM_HOOK_INIT(ptrace_access_check, cap_ptrace_access_check),
1450 LSM_HOOK_INIT(ptrace_traceme, cap_ptrace_traceme),
1451 LSM_HOOK_INIT(capget, cap_capget),
1452 LSM_HOOK_INIT(capset, cap_capset),
1453 LSM_HOOK_INIT(bprm_creds_from_file, cap_bprm_creds_from_file),
1454 LSM_HOOK_INIT(inode_need_killpriv, cap_inode_need_killpriv),
1455 LSM_HOOK_INIT(inode_killpriv, cap_inode_killpriv),
1456 LSM_HOOK_INIT(inode_getsecurity, cap_inode_getsecurity),
1457 LSM_HOOK_INIT(mmap_addr, cap_mmap_addr),
1458 LSM_HOOK_INIT(mmap_file, cap_mmap_file),
1459 LSM_HOOK_INIT(task_fix_setuid, cap_task_fix_setuid),
1460 LSM_HOOK_INIT(task_prctl, cap_task_prctl),
1461 LSM_HOOK_INIT(task_setscheduler, cap_task_setscheduler),
1462 LSM_HOOK_INIT(task_setioprio, cap_task_setioprio),
1463 LSM_HOOK_INIT(task_setnice, cap_task_setnice),
1464 LSM_HOOK_INIT(vm_enough_memory, cap_vm_enough_memory),
1465};
1466
1467static int __init capability_init(void)
1468{
1469 security_add_hooks(capability_hooks, ARRAY_SIZE(capability_hooks),
1470 "capability");
1471 return 0;
1472}
1473
1474DEFINE_LSM(capability) = {
1475 .name = "capability",
1476 .order = LSM_ORDER_FIRST,
1477 .init = capability_init,
1478};
1479
1480#endif /* CONFIG_SECURITY */