1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /* Common capabilities, needed by capability.o.
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>
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 #include <linux/mnt_idmapping.h>
30 * If a non-root user executes a setuid-root binary in
31 * !secure(SECURE_NOROOT) mode, then we raise capabilities.
32 * However if fE is also set, then the intent is for only
33 * the file capabilities to be applied, and the setuid-root
34 * bit is left on either to change the uid (plausible) or
35 * to get full privilege on a kernel without file capabilities
36 * support. So in that case we do not raise capabilities.
38 * Warn if that happens, once per boot.
40 static void warn_setuid_and_fcaps_mixed(const char *fname
)
44 printk(KERN_INFO
"warning: `%s' has both setuid-root and"
45 " effective capabilities. Therefore not raising all"
46 " capabilities.\n", fname
);
52 * cap_capable - Determine whether a task has a particular effective capability
53 * @cred: The credentials to use
54 * @targ_ns: The user namespace in which we need the capability
55 * @cap: The capability to check for
56 * @opts: Bitmask of options defined in include/linux/security.h
58 * Determine whether the nominated task has the specified capability amongst
59 * its effective set, returning 0 if it does, -ve if it does not.
61 * NOTE WELL: cap_has_capability() cannot be used like the kernel's capable()
62 * and has_capability() functions. That is, it has the reverse semantics:
63 * cap_has_capability() returns 0 when a task has a capability, but the
64 * kernel's capable() and has_capability() returns 1 for this case.
66 int cap_capable(const struct cred
*cred
, struct user_namespace
*targ_ns
,
67 int cap
, unsigned int opts
)
69 struct user_namespace
*ns
= targ_ns
;
71 /* See if cred has the capability in the target user namespace
72 * by examining the target user namespace and all of the target
73 * user namespace's parents.
76 /* Do we have the necessary capabilities? */
77 if (ns
== cred
->user_ns
)
78 return cap_raised(cred
->cap_effective
, cap
) ? 0 : -EPERM
;
81 * If we're already at a lower level than we're looking for,
82 * we're done searching.
84 if (ns
->level
<= cred
->user_ns
->level
)
88 * The owner of the user namespace in the parent of the
89 * user namespace has all caps.
91 if ((ns
->parent
== cred
->user_ns
) && uid_eq(ns
->owner
, cred
->euid
))
95 * If you have a capability in a parent user ns, then you have
96 * it over all children user namespaces as well.
101 /* We never get here */
105 * cap_settime - Determine whether the current process may set the system clock
106 * @ts: The time to set
107 * @tz: The timezone to set
109 * Determine whether the current process may set the system clock and timezone
110 * information, returning 0 if permission granted, -ve if denied.
112 int cap_settime(const struct timespec64
*ts
, const struct timezone
*tz
)
114 if (!capable(CAP_SYS_TIME
))
120 * cap_ptrace_access_check - Determine whether the current process may access
122 * @child: The process to be accessed
123 * @mode: The mode of attachment.
125 * If we are in the same or an ancestor user_ns and have all the target
126 * task's capabilities, then ptrace access is allowed.
127 * If we have the ptrace capability to the target user_ns, then ptrace
131 * Determine whether a process may access another, returning 0 if permission
132 * granted, -ve if denied.
134 int cap_ptrace_access_check(struct task_struct
*child
, unsigned int mode
)
137 const struct cred
*cred
, *child_cred
;
138 const kernel_cap_t
*caller_caps
;
141 cred
= current_cred();
142 child_cred
= __task_cred(child
);
143 if (mode
& PTRACE_MODE_FSCREDS
)
144 caller_caps
= &cred
->cap_effective
;
146 caller_caps
= &cred
->cap_permitted
;
147 if (cred
->user_ns
== child_cred
->user_ns
&&
148 cap_issubset(child_cred
->cap_permitted
, *caller_caps
))
150 if (ns_capable(child_cred
->user_ns
, CAP_SYS_PTRACE
))
159 * cap_ptrace_traceme - Determine whether another process may trace the current
160 * @parent: The task proposed to be the tracer
162 * If parent is in the same or an ancestor user_ns and has all current's
163 * capabilities, then ptrace access is allowed.
164 * If parent has the ptrace capability to current's user_ns, then ptrace
168 * Determine whether the nominated task is permitted to trace the current
169 * process, returning 0 if permission is granted, -ve if denied.
171 int cap_ptrace_traceme(struct task_struct
*parent
)
174 const struct cred
*cred
, *child_cred
;
177 cred
= __task_cred(parent
);
178 child_cred
= current_cred();
179 if (cred
->user_ns
== child_cred
->user_ns
&&
180 cap_issubset(child_cred
->cap_permitted
, cred
->cap_permitted
))
182 if (has_ns_capability(parent
, child_cred
->user_ns
, CAP_SYS_PTRACE
))
191 * cap_capget - Retrieve a task's capability sets
192 * @target: The task from which to retrieve the capability sets
193 * @effective: The place to record the effective set
194 * @inheritable: The place to record the inheritable set
195 * @permitted: The place to record the permitted set
197 * This function retrieves the capabilities of the nominated task and returns
198 * them to the caller.
200 int cap_capget(struct task_struct
*target
, kernel_cap_t
*effective
,
201 kernel_cap_t
*inheritable
, kernel_cap_t
*permitted
)
203 const struct cred
*cred
;
205 /* Derived from kernel/capability.c:sys_capget. */
207 cred
= __task_cred(target
);
208 *effective
= cred
->cap_effective
;
209 *inheritable
= cred
->cap_inheritable
;
210 *permitted
= cred
->cap_permitted
;
216 * Determine whether the inheritable capabilities are limited to the old
217 * permitted set. Returns 1 if they are limited, 0 if they are not.
219 static inline int cap_inh_is_capped(void)
221 /* they are so limited unless the current task has the CAP_SETPCAP
224 if (cap_capable(current_cred(), current_cred()->user_ns
,
225 CAP_SETPCAP
, CAP_OPT_NONE
) == 0)
231 * cap_capset - Validate and apply proposed changes to current's capabilities
232 * @new: The proposed new credentials; alterations should be made here
233 * @old: The current task's current credentials
234 * @effective: A pointer to the proposed new effective capabilities set
235 * @inheritable: A pointer to the proposed new inheritable capabilities set
236 * @permitted: A pointer to the proposed new permitted capabilities set
238 * This function validates and applies a proposed mass change to the current
239 * process's capability sets. The changes are made to the proposed new
240 * credentials, and assuming no error, will be committed by the caller of LSM.
242 int cap_capset(struct cred
*new,
243 const struct cred
*old
,
244 const kernel_cap_t
*effective
,
245 const kernel_cap_t
*inheritable
,
246 const kernel_cap_t
*permitted
)
248 if (cap_inh_is_capped() &&
249 !cap_issubset(*inheritable
,
250 cap_combine(old
->cap_inheritable
,
251 old
->cap_permitted
)))
252 /* incapable of using this inheritable set */
255 if (!cap_issubset(*inheritable
,
256 cap_combine(old
->cap_inheritable
,
258 /* no new pI capabilities outside bounding set */
261 /* verify restrictions on target's new Permitted set */
262 if (!cap_issubset(*permitted
, old
->cap_permitted
))
265 /* verify the _new_Effective_ is a subset of the _new_Permitted_ */
266 if (!cap_issubset(*effective
, *permitted
))
269 new->cap_effective
= *effective
;
270 new->cap_inheritable
= *inheritable
;
271 new->cap_permitted
= *permitted
;
274 * Mask off ambient bits that are no longer both permitted and
277 new->cap_ambient
= cap_intersect(new->cap_ambient
,
278 cap_intersect(*permitted
,
280 if (WARN_ON(!cap_ambient_invariant_ok(new)))
286 * cap_inode_need_killpriv - Determine if inode change affects privileges
287 * @dentry: The inode/dentry in being changed with change marked ATTR_KILL_PRIV
289 * Determine if an inode having a change applied that's marked ATTR_KILL_PRIV
290 * affects the security markings on that inode, and if it is, should
291 * inode_killpriv() be invoked or the change rejected.
293 * Return: 1 if security.capability has a value, meaning inode_killpriv()
294 * is required, 0 otherwise, meaning inode_killpriv() is not required.
296 int cap_inode_need_killpriv(struct dentry
*dentry
)
298 struct inode
*inode
= d_backing_inode(dentry
);
301 error
= __vfs_getxattr(dentry
, inode
, XATTR_NAME_CAPS
, NULL
, 0);
306 * cap_inode_killpriv - Erase the security markings on an inode
308 * @idmap: idmap of the mount the inode was found from
309 * @dentry: The inode/dentry to alter
311 * Erase the privilege-enhancing security markings on an inode.
313 * If the inode has been found through an idmapped mount the idmap of
314 * the vfsmount must be passed through @idmap. This function will then
315 * take care to map the inode according to @idmap before checking
316 * permissions. On non-idmapped mounts or if permission checking is to be
317 * performed on the raw inode simply pass @nop_mnt_idmap.
319 * Return: 0 if successful, -ve on error.
321 int cap_inode_killpriv(struct mnt_idmap
*idmap
, struct dentry
*dentry
)
325 error
= __vfs_removexattr(idmap
, dentry
, XATTR_NAME_CAPS
);
326 if (error
== -EOPNOTSUPP
)
331 static bool rootid_owns_currentns(vfsuid_t rootvfsuid
)
333 struct user_namespace
*ns
;
336 if (!vfsuid_valid(rootvfsuid
))
339 kroot
= vfsuid_into_kuid(rootvfsuid
);
340 for (ns
= current_user_ns();; ns
= ns
->parent
) {
341 if (from_kuid(ns
, kroot
) == 0)
343 if (ns
== &init_user_ns
)
350 static __u32
sansflags(__u32 m
)
352 return m
& ~VFS_CAP_FLAGS_EFFECTIVE
;
355 static bool is_v2header(int size
, const struct vfs_cap_data
*cap
)
357 if (size
!= XATTR_CAPS_SZ_2
)
359 return sansflags(le32_to_cpu(cap
->magic_etc
)) == VFS_CAP_REVISION_2
;
362 static bool is_v3header(int size
, const struct vfs_cap_data
*cap
)
364 if (size
!= XATTR_CAPS_SZ_3
)
366 return sansflags(le32_to_cpu(cap
->magic_etc
)) == VFS_CAP_REVISION_3
;
370 * getsecurity: We are called for security.* before any attempt to read the
371 * xattr from the inode itself.
373 * This gives us a chance to read the on-disk value and convert it. If we
374 * return -EOPNOTSUPP, then vfs_getxattr() will call the i_op handler.
376 * Note we are not called by vfs_getxattr_alloc(), but that is only called
377 * by the integrity subsystem, which really wants the unconverted values -
380 int cap_inode_getsecurity(struct mnt_idmap
*idmap
,
381 struct inode
*inode
, const char *name
, void **buffer
,
388 uid_t root
, mappedroot
;
390 struct vfs_cap_data
*cap
;
391 struct vfs_ns_cap_data
*nscap
= NULL
;
392 struct dentry
*dentry
;
393 struct user_namespace
*fs_ns
;
395 if (strcmp(name
, "capability") != 0)
398 dentry
= d_find_any_alias(inode
);
401 size
= vfs_getxattr_alloc(idmap
, dentry
, XATTR_NAME_CAPS
, &tmpbuf
,
402 sizeof(struct vfs_ns_cap_data
), GFP_NOFS
);
404 /* gcc11 complains if we don't check for !tmpbuf */
405 if (size
< 0 || !tmpbuf
)
408 fs_ns
= inode
->i_sb
->s_user_ns
;
409 cap
= (struct vfs_cap_data
*) tmpbuf
;
410 if (is_v2header(size
, cap
)) {
412 } else if (is_v3header(size
, cap
)) {
413 nscap
= (struct vfs_ns_cap_data
*) tmpbuf
;
414 root
= le32_to_cpu(nscap
->rootid
);
420 kroot
= make_kuid(fs_ns
, root
);
422 /* If this is an idmapped mount shift the kuid. */
423 vfsroot
= make_vfsuid(idmap
, fs_ns
, kroot
);
425 /* If the root kuid maps to a valid uid in current ns, then return
426 * this as a nscap. */
427 mappedroot
= from_kuid(current_user_ns(), vfsuid_into_kuid(vfsroot
));
428 if (mappedroot
!= (uid_t
)-1 && mappedroot
!= (uid_t
)0) {
429 size
= sizeof(struct vfs_ns_cap_data
);
432 /* v2 -> v3 conversion */
433 nscap
= kzalloc(size
, GFP_ATOMIC
);
438 nsmagic
= VFS_CAP_REVISION_3
;
439 magic
= le32_to_cpu(cap
->magic_etc
);
440 if (magic
& VFS_CAP_FLAGS_EFFECTIVE
)
441 nsmagic
|= VFS_CAP_FLAGS_EFFECTIVE
;
442 memcpy(&nscap
->data
, &cap
->data
, sizeof(__le32
) * 2 * VFS_CAP_U32
);
443 nscap
->magic_etc
= cpu_to_le32(nsmagic
);
445 /* use allocated v3 buffer */
448 nscap
->rootid
= cpu_to_le32(mappedroot
);
454 if (!rootid_owns_currentns(vfsroot
)) {
459 /* This comes from a parent namespace. Return as a v2 capability */
460 size
= sizeof(struct vfs_cap_data
);
463 /* v3 -> v2 conversion */
464 cap
= kzalloc(size
, GFP_ATOMIC
);
469 magic
= VFS_CAP_REVISION_2
;
470 nsmagic
= le32_to_cpu(nscap
->magic_etc
);
471 if (nsmagic
& VFS_CAP_FLAGS_EFFECTIVE
)
472 magic
|= VFS_CAP_FLAGS_EFFECTIVE
;
473 memcpy(&cap
->data
, &nscap
->data
, sizeof(__le32
) * 2 * VFS_CAP_U32
);
474 cap
->magic_etc
= cpu_to_le32(magic
);
476 /* use unconverted v2 */
487 * rootid_from_xattr - translate root uid of vfs caps
489 * @value: vfs caps value which may be modified by this function
490 * @size: size of @ivalue
491 * @task_ns: user namespace of the caller
493 static vfsuid_t
rootid_from_xattr(const void *value
, size_t size
,
494 struct user_namespace
*task_ns
)
496 const struct vfs_ns_cap_data
*nscap
= value
;
499 if (size
== XATTR_CAPS_SZ_3
)
500 rootid
= le32_to_cpu(nscap
->rootid
);
502 return VFSUIDT_INIT(make_kuid(task_ns
, rootid
));
505 static bool validheader(size_t size
, const struct vfs_cap_data
*cap
)
507 return is_v2header(size
, cap
) || is_v3header(size
, cap
);
511 * cap_convert_nscap - check vfs caps
513 * @idmap: idmap of the mount the inode was found from
514 * @dentry: used to retrieve inode to check permissions on
515 * @ivalue: vfs caps value which may be modified by this function
516 * @size: size of @ivalue
518 * User requested a write of security.capability. If needed, update the
519 * xattr to change from v2 to v3, or to fixup the v3 rootid.
521 * If the inode has been found through an idmapped mount the idmap of
522 * the vfsmount must be passed through @idmap. This function will then
523 * take care to map the inode according to @idmap before checking
524 * permissions. On non-idmapped mounts or if permission checking is to be
525 * performed on the raw inode simply pass @nop_mnt_idmap.
527 * Return: On success, return the new size; on error, return < 0.
529 int cap_convert_nscap(struct mnt_idmap
*idmap
, struct dentry
*dentry
,
530 const void **ivalue
, size_t size
)
532 struct vfs_ns_cap_data
*nscap
;
534 const struct vfs_cap_data
*cap
= *ivalue
;
535 __u32 magic
, nsmagic
;
536 struct inode
*inode
= d_backing_inode(dentry
);
537 struct user_namespace
*task_ns
= current_user_ns(),
538 *fs_ns
= inode
->i_sb
->s_user_ns
;
545 if (!validheader(size
, cap
))
547 if (!capable_wrt_inode_uidgid(idmap
, inode
, CAP_SETFCAP
))
549 if (size
== XATTR_CAPS_SZ_2
&& (idmap
== &nop_mnt_idmap
))
550 if (ns_capable(inode
->i_sb
->s_user_ns
, CAP_SETFCAP
))
551 /* user is privileged, just write the v2 */
554 vfsrootid
= rootid_from_xattr(*ivalue
, size
, task_ns
);
555 if (!vfsuid_valid(vfsrootid
))
558 rootid
= from_vfsuid(idmap
, fs_ns
, vfsrootid
);
559 if (!uid_valid(rootid
))
562 nsrootid
= from_kuid(fs_ns
, rootid
);
566 newsize
= sizeof(struct vfs_ns_cap_data
);
567 nscap
= kmalloc(newsize
, GFP_ATOMIC
);
570 nscap
->rootid
= cpu_to_le32(nsrootid
);
571 nsmagic
= VFS_CAP_REVISION_3
;
572 magic
= le32_to_cpu(cap
->magic_etc
);
573 if (magic
& VFS_CAP_FLAGS_EFFECTIVE
)
574 nsmagic
|= VFS_CAP_FLAGS_EFFECTIVE
;
575 nscap
->magic_etc
= cpu_to_le32(nsmagic
);
576 memcpy(&nscap
->data
, &cap
->data
, sizeof(__le32
) * 2 * VFS_CAP_U32
);
583 * Calculate the new process capability sets from the capability sets attached
586 static inline int bprm_caps_from_vfs_caps(struct cpu_vfs_cap_data
*caps
,
587 struct linux_binprm
*bprm
,
591 struct cred
*new = bprm
->cred
;
594 if (caps
->magic_etc
& VFS_CAP_FLAGS_EFFECTIVE
)
597 if (caps
->magic_etc
& VFS_CAP_REVISION_MASK
)
601 * pP' = (X & fP) | (pI & fI)
602 * The addition of pA' is handled later.
604 new->cap_permitted
.val
=
605 (new->cap_bset
.val
& caps
->permitted
.val
) |
606 (new->cap_inheritable
.val
& caps
->inheritable
.val
);
608 if (caps
->permitted
.val
& ~new->cap_permitted
.val
)
609 /* insufficient to execute correctly */
613 * For legacy apps, with no internal support for recognizing they
614 * do not have enough capabilities, we return an error if they are
615 * missing some "forced" (aka file-permitted) capabilities.
617 return *effective
? ret
: 0;
621 * get_vfs_caps_from_disk - retrieve vfs caps from disk
623 * @idmap: idmap of the mount the inode was found from
624 * @dentry: dentry from which @inode is retrieved
625 * @cpu_caps: vfs capabilities
627 * Extract the on-exec-apply capability sets for an executable file.
629 * If the inode has been found through an idmapped mount the idmap of
630 * the vfsmount must be passed through @idmap. This function will then
631 * take care to map the inode according to @idmap before checking
632 * permissions. On non-idmapped mounts or if permission checking is to be
633 * performed on the raw inode simply pass @nop_mnt_idmap.
635 int get_vfs_caps_from_disk(struct mnt_idmap
*idmap
,
636 const struct dentry
*dentry
,
637 struct cpu_vfs_cap_data
*cpu_caps
)
639 struct inode
*inode
= d_backing_inode(dentry
);
642 struct vfs_ns_cap_data data
, *nscaps
= &data
;
643 struct vfs_cap_data
*caps
= (struct vfs_cap_data
*) &data
;
646 struct user_namespace
*fs_ns
;
648 memset(cpu_caps
, 0, sizeof(struct cpu_vfs_cap_data
));
653 fs_ns
= inode
->i_sb
->s_user_ns
;
654 size
= __vfs_getxattr((struct dentry
*)dentry
, inode
,
655 XATTR_NAME_CAPS
, &data
, XATTR_CAPS_SZ
);
656 if (size
== -ENODATA
|| size
== -EOPNOTSUPP
)
657 /* no data, that's ok */
663 if (size
< sizeof(magic_etc
))
666 cpu_caps
->magic_etc
= magic_etc
= le32_to_cpu(caps
->magic_etc
);
668 rootkuid
= make_kuid(fs_ns
, 0);
669 switch (magic_etc
& VFS_CAP_REVISION_MASK
) {
670 case VFS_CAP_REVISION_1
:
671 if (size
!= XATTR_CAPS_SZ_1
)
674 case VFS_CAP_REVISION_2
:
675 if (size
!= XATTR_CAPS_SZ_2
)
678 case VFS_CAP_REVISION_3
:
679 if (size
!= XATTR_CAPS_SZ_3
)
681 rootkuid
= make_kuid(fs_ns
, le32_to_cpu(nscaps
->rootid
));
688 rootvfsuid
= make_vfsuid(idmap
, fs_ns
, rootkuid
);
689 if (!vfsuid_valid(rootvfsuid
))
692 /* Limit the caps to the mounter of the filesystem
693 * or the more limited uid specified in the xattr.
695 if (!rootid_owns_currentns(rootvfsuid
))
698 cpu_caps
->permitted
.val
= le32_to_cpu(caps
->data
[0].permitted
);
699 cpu_caps
->inheritable
.val
= le32_to_cpu(caps
->data
[0].inheritable
);
702 * Rev1 had just a single 32-bit word, later expanded
703 * to a second one for the high bits
705 if ((magic_etc
& VFS_CAP_REVISION_MASK
) != VFS_CAP_REVISION_1
) {
706 cpu_caps
->permitted
.val
+= (u64
)le32_to_cpu(caps
->data
[1].permitted
) << 32;
707 cpu_caps
->inheritable
.val
+= (u64
)le32_to_cpu(caps
->data
[1].inheritable
) << 32;
710 cpu_caps
->permitted
.val
&= CAP_VALID_MASK
;
711 cpu_caps
->inheritable
.val
&= CAP_VALID_MASK
;
713 cpu_caps
->rootid
= vfsuid_into_kuid(rootvfsuid
);
719 * Attempt to get the on-exec apply capability sets for an executable file from
720 * its xattrs and, if present, apply them to the proposed credentials being
721 * constructed by execve().
723 static int get_file_caps(struct linux_binprm
*bprm
, struct file
*file
,
724 bool *effective
, bool *has_fcap
)
727 struct cpu_vfs_cap_data vcaps
;
729 cap_clear(bprm
->cred
->cap_permitted
);
731 if (!file_caps_enabled
)
734 if (!mnt_may_suid(file
->f_path
.mnt
))
738 * This check is redundant with mnt_may_suid() but is kept to make
739 * explicit that capability bits are limited to s_user_ns and its
742 if (!current_in_userns(file
->f_path
.mnt
->mnt_sb
->s_user_ns
))
745 rc
= get_vfs_caps_from_disk(file_mnt_idmap(file
),
746 file
->f_path
.dentry
, &vcaps
);
749 printk(KERN_NOTICE
"Invalid argument reading file caps for %s\n",
751 else if (rc
== -ENODATA
)
756 rc
= bprm_caps_from_vfs_caps(&vcaps
, bprm
, effective
, has_fcap
);
760 cap_clear(bprm
->cred
->cap_permitted
);
765 static inline bool root_privileged(void) { return !issecure(SECURE_NOROOT
); }
767 static inline bool __is_real(kuid_t uid
, struct cred
*cred
)
768 { return uid_eq(cred
->uid
, uid
); }
770 static inline bool __is_eff(kuid_t uid
, struct cred
*cred
)
771 { return uid_eq(cred
->euid
, uid
); }
773 static inline bool __is_suid(kuid_t uid
, struct cred
*cred
)
774 { return !__is_real(uid
, cred
) && __is_eff(uid
, cred
); }
777 * handle_privileged_root - Handle case of privileged root
778 * @bprm: The execution parameters, including the proposed creds
779 * @has_fcap: Are any file capabilities set?
780 * @effective: Do we have effective root privilege?
781 * @root_uid: This namespace' root UID WRT initial USER namespace
783 * Handle the case where root is privileged and hasn't been neutered by
784 * SECURE_NOROOT. If file capabilities are set, they won't be combined with
785 * set UID root and nothing is changed. If we are root, cap_permitted is
786 * updated. If we have become set UID root, the effective bit is set.
788 static void handle_privileged_root(struct linux_binprm
*bprm
, bool has_fcap
,
789 bool *effective
, kuid_t root_uid
)
791 const struct cred
*old
= current_cred();
792 struct cred
*new = bprm
->cred
;
794 if (!root_privileged())
797 * If the legacy file capability is set, then don't set privs
798 * for a setuid root binary run by a non-root user. Do set it
799 * for a root user just to cause least surprise to an admin.
801 if (has_fcap
&& __is_suid(root_uid
, new)) {
802 warn_setuid_and_fcaps_mixed(bprm
->filename
);
806 * To support inheritance of root-permissions and suid-root
807 * executables under compatibility mode, we override the
808 * capability sets for the file.
810 if (__is_eff(root_uid
, new) || __is_real(root_uid
, new)) {
811 /* pP' = (cap_bset & ~0) | (pI & ~0) */
812 new->cap_permitted
= cap_combine(old
->cap_bset
,
813 old
->cap_inheritable
);
816 * If only the real uid is 0, we do not set the effective bit.
818 if (__is_eff(root_uid
, new))
822 #define __cap_gained(field, target, source) \
823 !cap_issubset(target->cap_##field, source->cap_##field)
824 #define __cap_grew(target, source, cred) \
825 !cap_issubset(cred->cap_##target, cred->cap_##source)
826 #define __cap_full(field, cred) \
827 cap_issubset(CAP_FULL_SET, cred->cap_##field)
829 static inline bool __is_setuid(struct cred
*new, const struct cred
*old
)
830 { return !uid_eq(new->euid
, old
->uid
); }
832 static inline bool __is_setgid(struct cred
*new, const struct cred
*old
)
833 { return !gid_eq(new->egid
, old
->gid
); }
836 * 1) Audit candidate if current->cap_effective is set
838 * We do not bother to audit if 3 things are true:
839 * 1) cap_effective has all caps
840 * 2) we became root *OR* are were already root
841 * 3) root is supposed to have all caps (SECURE_NOROOT)
842 * Since this is just a normal root execing a process.
844 * Number 1 above might fail if you don't have a full bset, but I think
845 * that is interesting information to audit.
847 * A number of other conditions require logging:
848 * 2) something prevented setuid root getting all caps
849 * 3) non-setuid root gets fcaps
850 * 4) non-setuid root gets ambient
852 static inline bool nonroot_raised_pE(struct cred
*new, const struct cred
*old
,
853 kuid_t root
, bool has_fcap
)
857 if ((__cap_grew(effective
, ambient
, new) &&
858 !(__cap_full(effective
, new) &&
859 (__is_eff(root
, new) || __is_real(root
, new)) &&
860 root_privileged())) ||
861 (root_privileged() &&
862 __is_suid(root
, new) &&
863 !__cap_full(effective
, new)) ||
864 (!__is_setuid(new, old
) &&
866 __cap_gained(permitted
, new, old
)) ||
867 __cap_gained(ambient
, new, old
))))
875 * cap_bprm_creds_from_file - Set up the proposed credentials for execve().
876 * @bprm: The execution parameters, including the proposed creds
877 * @file: The file to pull the credentials from
879 * Set up the proposed credentials for a new execution context being
880 * constructed by execve(). The proposed creds in @bprm->cred is altered,
881 * which won't take effect immediately.
883 * Return: 0 if successful, -ve on error.
885 int cap_bprm_creds_from_file(struct linux_binprm
*bprm
, struct file
*file
)
887 /* Process setpcap binaries and capabilities for uid 0 */
888 const struct cred
*old
= current_cred();
889 struct cred
*new = bprm
->cred
;
890 bool effective
= false, has_fcap
= false, is_setid
;
894 if (WARN_ON(!cap_ambient_invariant_ok(old
)))
897 ret
= get_file_caps(bprm
, file
, &effective
, &has_fcap
);
901 root_uid
= make_kuid(new->user_ns
, 0);
903 handle_privileged_root(bprm
, has_fcap
, &effective
, root_uid
);
905 /* if we have fs caps, clear dangerous personality flags */
906 if (__cap_gained(permitted
, new, old
))
907 bprm
->per_clear
|= PER_CLEAR_ON_SETID
;
909 /* Don't let someone trace a set[ug]id/setpcap binary with the revised
910 * credentials unless they have the appropriate permit.
912 * In addition, if NO_NEW_PRIVS, then ensure we get no new privs.
914 is_setid
= __is_setuid(new, old
) || __is_setgid(new, old
);
916 if ((is_setid
|| __cap_gained(permitted
, new, old
)) &&
917 ((bprm
->unsafe
& ~LSM_UNSAFE_PTRACE
) ||
918 !ptracer_capable(current
, new->user_ns
))) {
919 /* downgrade; they get no more than they had, and maybe less */
920 if (!ns_capable(new->user_ns
, CAP_SETUID
) ||
921 (bprm
->unsafe
& LSM_UNSAFE_NO_NEW_PRIVS
)) {
922 new->euid
= new->uid
;
923 new->egid
= new->gid
;
925 new->cap_permitted
= cap_intersect(new->cap_permitted
,
929 new->suid
= new->fsuid
= new->euid
;
930 new->sgid
= new->fsgid
= new->egid
;
932 /* File caps or setid cancels ambient. */
933 if (has_fcap
|| is_setid
)
934 cap_clear(new->cap_ambient
);
937 * Now that we've computed pA', update pP' to give:
938 * pP' = (X & fP) | (pI & fI) | pA'
940 new->cap_permitted
= cap_combine(new->cap_permitted
, new->cap_ambient
);
943 * Set pE' = (fE ? pP' : pA'). Because pA' is zero if fE is set,
944 * this is the same as pE' = (fE ? pP' : 0) | pA'.
947 new->cap_effective
= new->cap_permitted
;
949 new->cap_effective
= new->cap_ambient
;
951 if (WARN_ON(!cap_ambient_invariant_ok(new)))
954 if (nonroot_raised_pE(new, old
, root_uid
, has_fcap
)) {
955 ret
= audit_log_bprm_fcaps(bprm
, new, old
);
960 new->securebits
&= ~issecure_mask(SECURE_KEEP_CAPS
);
962 if (WARN_ON(!cap_ambient_invariant_ok(new)))
965 /* Check for privilege-elevated exec. */
967 (!__is_real(root_uid
, new) &&
969 __cap_grew(permitted
, ambient
, new))))
970 bprm
->secureexec
= 1;
976 * cap_inode_setxattr - Determine whether an xattr may be altered
977 * @dentry: The inode/dentry being altered
978 * @name: The name of the xattr to be changed
979 * @value: The value that the xattr will be changed to
980 * @size: The size of value
981 * @flags: The replacement flag
983 * Determine whether an xattr may be altered or set on an inode, returning 0 if
984 * permission is granted, -ve if denied.
986 * This is used to make sure security xattrs don't get updated or set by those
987 * who aren't privileged to do so.
989 int cap_inode_setxattr(struct dentry
*dentry
, const char *name
,
990 const void *value
, size_t size
, int flags
)
992 struct user_namespace
*user_ns
= dentry
->d_sb
->s_user_ns
;
994 /* Ignore non-security xattrs */
995 if (strncmp(name
, XATTR_SECURITY_PREFIX
,
996 XATTR_SECURITY_PREFIX_LEN
) != 0)
1000 * For XATTR_NAME_CAPS the check will be done in
1001 * cap_convert_nscap(), called by setxattr()
1003 if (strcmp(name
, XATTR_NAME_CAPS
) == 0)
1006 if (!ns_capable(user_ns
, CAP_SYS_ADMIN
))
1012 * cap_inode_removexattr - Determine whether an xattr may be removed
1014 * @idmap: idmap of the mount the inode was found from
1015 * @dentry: The inode/dentry being altered
1016 * @name: The name of the xattr to be changed
1018 * Determine whether an xattr may be removed from an inode, returning 0 if
1019 * permission is granted, -ve if denied.
1021 * If the inode has been found through an idmapped mount the idmap of
1022 * the vfsmount must be passed through @idmap. This function will then
1023 * take care to map the inode according to @idmap before checking
1024 * permissions. On non-idmapped mounts or if permission checking is to be
1025 * performed on the raw inode simply pass @nop_mnt_idmap.
1027 * This is used to make sure security xattrs don't get removed by those who
1028 * aren't privileged to remove them.
1030 int cap_inode_removexattr(struct mnt_idmap
*idmap
,
1031 struct dentry
*dentry
, const char *name
)
1033 struct user_namespace
*user_ns
= dentry
->d_sb
->s_user_ns
;
1035 /* Ignore non-security xattrs */
1036 if (strncmp(name
, XATTR_SECURITY_PREFIX
,
1037 XATTR_SECURITY_PREFIX_LEN
) != 0)
1040 if (strcmp(name
, XATTR_NAME_CAPS
) == 0) {
1041 /* security.capability gets namespaced */
1042 struct inode
*inode
= d_backing_inode(dentry
);
1045 if (!capable_wrt_inode_uidgid(idmap
, inode
, CAP_SETFCAP
))
1050 if (!ns_capable(user_ns
, CAP_SYS_ADMIN
))
1056 * cap_emulate_setxuid() fixes the effective / permitted capabilities of
1057 * a process after a call to setuid, setreuid, or setresuid.
1059 * 1) When set*uiding _from_ one of {r,e,s}uid == 0 _to_ all of
1060 * {r,e,s}uid != 0, the permitted and effective capabilities are
1063 * 2) When set*uiding _from_ euid == 0 _to_ euid != 0, the effective
1064 * capabilities of the process are cleared.
1066 * 3) When set*uiding _from_ euid != 0 _to_ euid == 0, the effective
1067 * capabilities are set to the permitted capabilities.
1069 * fsuid is handled elsewhere. fsuid == 0 and {r,e,s}uid!= 0 should
1074 * cevans - New behaviour, Oct '99
1075 * A process may, via prctl(), elect to keep its capabilities when it
1076 * calls setuid() and switches away from uid==0. Both permitted and
1077 * effective sets will be retained.
1078 * Without this change, it was impossible for a daemon to drop only some
1079 * of its privilege. The call to setuid(!=0) would drop all privileges!
1080 * Keeping uid 0 is not an option because uid 0 owns too many vital
1082 * Thanks to Olaf Kirch and Peter Benie for spotting this.
1084 static inline void cap_emulate_setxuid(struct cred
*new, const struct cred
*old
)
1086 kuid_t root_uid
= make_kuid(old
->user_ns
, 0);
1088 if ((uid_eq(old
->uid
, root_uid
) ||
1089 uid_eq(old
->euid
, root_uid
) ||
1090 uid_eq(old
->suid
, root_uid
)) &&
1091 (!uid_eq(new->uid
, root_uid
) &&
1092 !uid_eq(new->euid
, root_uid
) &&
1093 !uid_eq(new->suid
, root_uid
))) {
1094 if (!issecure(SECURE_KEEP_CAPS
)) {
1095 cap_clear(new->cap_permitted
);
1096 cap_clear(new->cap_effective
);
1100 * Pre-ambient programs expect setresuid to nonroot followed
1101 * by exec to drop capabilities. We should make sure that
1102 * this remains the case.
1104 cap_clear(new->cap_ambient
);
1106 if (uid_eq(old
->euid
, root_uid
) && !uid_eq(new->euid
, root_uid
))
1107 cap_clear(new->cap_effective
);
1108 if (!uid_eq(old
->euid
, root_uid
) && uid_eq(new->euid
, root_uid
))
1109 new->cap_effective
= new->cap_permitted
;
1113 * cap_task_fix_setuid - Fix up the results of setuid() call
1114 * @new: The proposed credentials
1115 * @old: The current task's current credentials
1116 * @flags: Indications of what has changed
1118 * Fix up the results of setuid() call before the credential changes are
1121 * Return: 0 to grant the changes, -ve to deny them.
1123 int cap_task_fix_setuid(struct cred
*new, const struct cred
*old
, int flags
)
1129 /* juggle the capabilities to follow [RES]UID changes unless
1130 * otherwise suppressed */
1131 if (!issecure(SECURE_NO_SETUID_FIXUP
))
1132 cap_emulate_setxuid(new, old
);
1136 /* juggle the capabilities to follow FSUID changes, unless
1137 * otherwise suppressed
1139 * FIXME - is fsuser used for all CAP_FS_MASK capabilities?
1140 * if not, we might be a bit too harsh here.
1142 if (!issecure(SECURE_NO_SETUID_FIXUP
)) {
1143 kuid_t root_uid
= make_kuid(old
->user_ns
, 0);
1144 if (uid_eq(old
->fsuid
, root_uid
) && !uid_eq(new->fsuid
, root_uid
))
1145 new->cap_effective
=
1146 cap_drop_fs_set(new->cap_effective
);
1148 if (!uid_eq(old
->fsuid
, root_uid
) && uid_eq(new->fsuid
, root_uid
))
1149 new->cap_effective
=
1150 cap_raise_fs_set(new->cap_effective
,
1151 new->cap_permitted
);
1163 * Rationale: code calling task_setscheduler, task_setioprio, and
1164 * task_setnice, assumes that
1165 * . if capable(cap_sys_nice), then those actions should be allowed
1166 * . if not capable(cap_sys_nice), but acting on your own processes,
1167 * then those actions should be allowed
1168 * This is insufficient now since you can call code without suid, but
1169 * yet with increased caps.
1170 * So we check for increased caps on the target process.
1172 static int cap_safe_nice(struct task_struct
*p
)
1174 int is_subset
, ret
= 0;
1177 is_subset
= cap_issubset(__task_cred(p
)->cap_permitted
,
1178 current_cred()->cap_permitted
);
1179 if (!is_subset
&& !ns_capable(__task_cred(p
)->user_ns
, CAP_SYS_NICE
))
1187 * cap_task_setscheduler - Determine if scheduler policy change is permitted
1188 * @p: The task to affect
1190 * Determine if the requested scheduler policy change is permitted for the
1193 * Return: 0 if permission is granted, -ve if denied.
1195 int cap_task_setscheduler(struct task_struct
*p
)
1197 return cap_safe_nice(p
);
1201 * cap_task_setioprio - Determine if I/O priority change is permitted
1202 * @p: The task to affect
1203 * @ioprio: The I/O priority to set
1205 * Determine if the requested I/O priority change is permitted for the specified
1208 * Return: 0 if permission is granted, -ve if denied.
1210 int cap_task_setioprio(struct task_struct
*p
, int ioprio
)
1212 return cap_safe_nice(p
);
1216 * cap_task_setnice - Determine if task priority change is permitted
1217 * @p: The task to affect
1218 * @nice: The nice value to set
1220 * Determine if the requested task priority change is permitted for the
1223 * Return: 0 if permission is granted, -ve if denied.
1225 int cap_task_setnice(struct task_struct
*p
, int nice
)
1227 return cap_safe_nice(p
);
1231 * Implement PR_CAPBSET_DROP. Attempt to remove the specified capability from
1232 * the current task's bounding set. Returns 0 on success, -ve on error.
1234 static int cap_prctl_drop(unsigned long cap
)
1238 if (!ns_capable(current_user_ns(), CAP_SETPCAP
))
1240 if (!cap_valid(cap
))
1243 new = prepare_creds();
1246 cap_lower(new->cap_bset
, cap
);
1247 return commit_creds(new);
1251 * cap_task_prctl - Implement process control functions for this security module
1252 * @option: The process control function requested
1253 * @arg2: The argument data for this function
1254 * @arg3: The argument data for this function
1255 * @arg4: The argument data for this function
1256 * @arg5: The argument data for this function
1258 * Allow process control functions (sys_prctl()) to alter capabilities; may
1259 * also deny access to other functions not otherwise implemented here.
1261 * Return: 0 or +ve on success, -ENOSYS if this function is not implemented
1262 * here, other -ve on error. If -ENOSYS is returned, sys_prctl() and other LSM
1263 * modules will consider performing the function.
1265 int cap_task_prctl(int option
, unsigned long arg2
, unsigned long arg3
,
1266 unsigned long arg4
, unsigned long arg5
)
1268 const struct cred
*old
= current_cred();
1272 case PR_CAPBSET_READ
:
1273 if (!cap_valid(arg2
))
1275 return !!cap_raised(old
->cap_bset
, arg2
);
1277 case PR_CAPBSET_DROP
:
1278 return cap_prctl_drop(arg2
);
1281 * The next four prctl's remain to assist with transitioning a
1282 * system from legacy UID=0 based privilege (when filesystem
1283 * capabilities are not in use) to a system using filesystem
1284 * capabilities only - as the POSIX.1e draft intended.
1288 * PR_SET_SECUREBITS =
1289 * issecure_mask(SECURE_KEEP_CAPS_LOCKED)
1290 * | issecure_mask(SECURE_NOROOT)
1291 * | issecure_mask(SECURE_NOROOT_LOCKED)
1292 * | issecure_mask(SECURE_NO_SETUID_FIXUP)
1293 * | issecure_mask(SECURE_NO_SETUID_FIXUP_LOCKED)
1295 * will ensure that the current process and all of its
1296 * children will be locked into a pure
1297 * capability-based-privilege environment.
1299 case PR_SET_SECUREBITS
:
1300 if ((((old
->securebits
& SECURE_ALL_LOCKS
) >> 1)
1301 & (old
->securebits
^ arg2
)) /*[1]*/
1302 || ((old
->securebits
& SECURE_ALL_LOCKS
& ~arg2
)) /*[2]*/
1303 || (arg2
& ~(SECURE_ALL_LOCKS
| SECURE_ALL_BITS
)) /*[3]*/
1304 || (cap_capable(current_cred(),
1305 current_cred()->user_ns
,
1307 CAP_OPT_NONE
) != 0) /*[4]*/
1309 * [1] no changing of bits that are locked
1310 * [2] no unlocking of locks
1311 * [3] no setting of unsupported bits
1312 * [4] doing anything requires privilege (go read about
1313 * the "sendmail capabilities bug")
1316 /* cannot change a locked bit */
1319 new = prepare_creds();
1322 new->securebits
= arg2
;
1323 return commit_creds(new);
1325 case PR_GET_SECUREBITS
:
1326 return old
->securebits
;
1328 case PR_GET_KEEPCAPS
:
1329 return !!issecure(SECURE_KEEP_CAPS
);
1331 case PR_SET_KEEPCAPS
:
1332 if (arg2
> 1) /* Note, we rely on arg2 being unsigned here */
1334 if (issecure(SECURE_KEEP_CAPS_LOCKED
))
1337 new = prepare_creds();
1341 new->securebits
|= issecure_mask(SECURE_KEEP_CAPS
);
1343 new->securebits
&= ~issecure_mask(SECURE_KEEP_CAPS
);
1344 return commit_creds(new);
1346 case PR_CAP_AMBIENT
:
1347 if (arg2
== PR_CAP_AMBIENT_CLEAR_ALL
) {
1348 if (arg3
| arg4
| arg5
)
1351 new = prepare_creds();
1354 cap_clear(new->cap_ambient
);
1355 return commit_creds(new);
1358 if (((!cap_valid(arg3
)) | arg4
| arg5
))
1361 if (arg2
== PR_CAP_AMBIENT_IS_SET
) {
1362 return !!cap_raised(current_cred()->cap_ambient
, arg3
);
1363 } else if (arg2
!= PR_CAP_AMBIENT_RAISE
&&
1364 arg2
!= PR_CAP_AMBIENT_LOWER
) {
1367 if (arg2
== PR_CAP_AMBIENT_RAISE
&&
1368 (!cap_raised(current_cred()->cap_permitted
, arg3
) ||
1369 !cap_raised(current_cred()->cap_inheritable
,
1371 issecure(SECURE_NO_CAP_AMBIENT_RAISE
)))
1374 new = prepare_creds();
1377 if (arg2
== PR_CAP_AMBIENT_RAISE
)
1378 cap_raise(new->cap_ambient
, arg3
);
1380 cap_lower(new->cap_ambient
, arg3
);
1381 return commit_creds(new);
1385 /* No functionality available - continue with default */
1391 * cap_vm_enough_memory - Determine whether a new virtual mapping is permitted
1392 * @mm: The VM space in which the new mapping is to be made
1393 * @pages: The size of the mapping
1395 * Determine whether the allocation of a new virtual mapping by the current
1396 * task is permitted.
1398 * Return: 1 if permission is granted, 0 if not.
1400 int cap_vm_enough_memory(struct mm_struct
*mm
, long pages
)
1402 int cap_sys_admin
= 0;
1404 if (cap_capable(current_cred(), &init_user_ns
,
1405 CAP_SYS_ADMIN
, CAP_OPT_NOAUDIT
) == 0)
1408 return cap_sys_admin
;
1412 * cap_mmap_addr - check if able to map given addr
1413 * @addr: address attempting to be mapped
1415 * If the process is attempting to map memory below dac_mmap_min_addr they need
1416 * CAP_SYS_RAWIO. The other parameters to this function are unused by the
1417 * capability security module.
1419 * Return: 0 if this mapping should be allowed or -EPERM if not.
1421 int cap_mmap_addr(unsigned long addr
)
1425 if (addr
< dac_mmap_min_addr
) {
1426 ret
= cap_capable(current_cred(), &init_user_ns
, CAP_SYS_RAWIO
,
1428 /* set PF_SUPERPRIV if it turns out we allow the low mmap */
1430 current
->flags
|= PF_SUPERPRIV
;
1435 int cap_mmap_file(struct file
*file
, unsigned long reqprot
,
1436 unsigned long prot
, unsigned long flags
)
1441 #ifdef CONFIG_SECURITY
1443 static struct security_hook_list capability_hooks
[] __ro_after_init
= {
1444 LSM_HOOK_INIT(capable
, cap_capable
),
1445 LSM_HOOK_INIT(settime
, cap_settime
),
1446 LSM_HOOK_INIT(ptrace_access_check
, cap_ptrace_access_check
),
1447 LSM_HOOK_INIT(ptrace_traceme
, cap_ptrace_traceme
),
1448 LSM_HOOK_INIT(capget
, cap_capget
),
1449 LSM_HOOK_INIT(capset
, cap_capset
),
1450 LSM_HOOK_INIT(bprm_creds_from_file
, cap_bprm_creds_from_file
),
1451 LSM_HOOK_INIT(inode_need_killpriv
, cap_inode_need_killpriv
),
1452 LSM_HOOK_INIT(inode_killpriv
, cap_inode_killpriv
),
1453 LSM_HOOK_INIT(inode_getsecurity
, cap_inode_getsecurity
),
1454 LSM_HOOK_INIT(mmap_addr
, cap_mmap_addr
),
1455 LSM_HOOK_INIT(mmap_file
, cap_mmap_file
),
1456 LSM_HOOK_INIT(task_fix_setuid
, cap_task_fix_setuid
),
1457 LSM_HOOK_INIT(task_prctl
, cap_task_prctl
),
1458 LSM_HOOK_INIT(task_setscheduler
, cap_task_setscheduler
),
1459 LSM_HOOK_INIT(task_setioprio
, cap_task_setioprio
),
1460 LSM_HOOK_INIT(task_setnice
, cap_task_setnice
),
1461 LSM_HOOK_INIT(vm_enough_memory
, cap_vm_enough_memory
),
1464 static int __init
capability_init(void)
1466 security_add_hooks(capability_hooks
, ARRAY_SIZE(capability_hooks
),
1471 DEFINE_LSM(capability
) = {
1472 .name
= "capability",
1473 .order
= LSM_ORDER_FIRST
,
1474 .init
= capability_init
,
1477 #endif /* CONFIG_SECURITY */