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 * @mnt_userns: user namespace 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 user namespace of
314 * the vfsmount must be passed through @mnt_userns. This function will then
315 * take care to map the inode according to @mnt_userns before checking
316 * permissions. On non-idmapped mounts or if permission checking is to be
317 * performed on the raw inode simply passs init_user_ns.
319 * Return: 0 if successful, -ve on error.
321 int cap_inode_killpriv(struct user_namespace
*mnt_userns
, struct dentry
*dentry
)
325 error
= __vfs_removexattr(mnt_userns
, dentry
, XATTR_NAME_CAPS
);
326 if (error
== -EOPNOTSUPP
)
331 static bool rootid_owns_currentns(kuid_t kroot
)
333 struct user_namespace
*ns
;
335 if (!uid_valid(kroot
))
338 for (ns
= current_user_ns(); ; ns
= ns
->parent
) {
339 if (from_kuid(ns
, kroot
) == 0)
341 if (ns
== &init_user_ns
)
348 static __u32
sansflags(__u32 m
)
350 return m
& ~VFS_CAP_FLAGS_EFFECTIVE
;
353 static bool is_v2header(size_t size
, const struct vfs_cap_data
*cap
)
355 if (size
!= XATTR_CAPS_SZ_2
)
357 return sansflags(le32_to_cpu(cap
->magic_etc
)) == VFS_CAP_REVISION_2
;
360 static bool is_v3header(size_t size
, const struct vfs_cap_data
*cap
)
362 if (size
!= XATTR_CAPS_SZ_3
)
364 return sansflags(le32_to_cpu(cap
->magic_etc
)) == VFS_CAP_REVISION_3
;
368 * getsecurity: We are called for security.* before any attempt to read the
369 * xattr from the inode itself.
371 * This gives us a chance to read the on-disk value and convert it. If we
372 * return -EOPNOTSUPP, then vfs_getxattr() will call the i_op handler.
374 * Note we are not called by vfs_getxattr_alloc(), but that is only called
375 * by the integrity subsystem, which really wants the unconverted values -
378 int cap_inode_getsecurity(struct user_namespace
*mnt_userns
,
379 struct inode
*inode
, const char *name
, void **buffer
,
385 uid_t root
, mappedroot
;
387 struct vfs_cap_data
*cap
;
388 struct vfs_ns_cap_data
*nscap
= NULL
;
389 struct dentry
*dentry
;
390 struct user_namespace
*fs_ns
;
392 if (strcmp(name
, "capability") != 0)
395 dentry
= d_find_any_alias(inode
);
399 size
= sizeof(struct vfs_ns_cap_data
);
400 ret
= (int)vfs_getxattr_alloc(mnt_userns
, dentry
, XATTR_NAME_CAPS
,
401 &tmpbuf
, size
, GFP_NOFS
);
404 if (ret
< 0 || !tmpbuf
)
407 fs_ns
= inode
->i_sb
->s_user_ns
;
408 cap
= (struct vfs_cap_data
*) tmpbuf
;
409 if (is_v2header((size_t) ret
, cap
)) {
411 } else if (is_v3header((size_t) ret
, cap
)) {
412 nscap
= (struct vfs_ns_cap_data
*) tmpbuf
;
413 root
= le32_to_cpu(nscap
->rootid
);
419 kroot
= make_kuid(fs_ns
, root
);
421 /* If this is an idmapped mount shift the kuid. */
422 kroot
= mapped_kuid_fs(mnt_userns
, fs_ns
, kroot
);
424 /* If the root kuid maps to a valid uid in current ns, then return
425 * this as a nscap. */
426 mappedroot
= from_kuid(current_user_ns(), kroot
);
427 if (mappedroot
!= (uid_t
)-1 && mappedroot
!= (uid_t
)0) {
428 size
= sizeof(struct vfs_ns_cap_data
);
431 /* v2 -> v3 conversion */
432 nscap
= kzalloc(size
, GFP_ATOMIC
);
437 nsmagic
= VFS_CAP_REVISION_3
;
438 magic
= le32_to_cpu(cap
->magic_etc
);
439 if (magic
& VFS_CAP_FLAGS_EFFECTIVE
)
440 nsmagic
|= VFS_CAP_FLAGS_EFFECTIVE
;
441 memcpy(&nscap
->data
, &cap
->data
, sizeof(__le32
) * 2 * VFS_CAP_U32
);
442 nscap
->magic_etc
= cpu_to_le32(nsmagic
);
444 /* use allocated v3 buffer */
447 nscap
->rootid
= cpu_to_le32(mappedroot
);
453 if (!rootid_owns_currentns(kroot
)) {
458 /* This comes from a parent namespace. Return as a v2 capability */
459 size
= sizeof(struct vfs_cap_data
);
462 /* v3 -> v2 conversion */
463 cap
= kzalloc(size
, GFP_ATOMIC
);
468 magic
= VFS_CAP_REVISION_2
;
469 nsmagic
= le32_to_cpu(nscap
->magic_etc
);
470 if (nsmagic
& VFS_CAP_FLAGS_EFFECTIVE
)
471 magic
|= VFS_CAP_FLAGS_EFFECTIVE
;
472 memcpy(&cap
->data
, &nscap
->data
, sizeof(__le32
) * 2 * VFS_CAP_U32
);
473 cap
->magic_etc
= cpu_to_le32(magic
);
475 /* use unconverted v2 */
486 * rootid_from_xattr - translate root uid of vfs caps
488 * @value: vfs caps value which may be modified by this function
489 * @size: size of @ivalue
490 * @task_ns: user namespace of the caller
491 * @mnt_userns: user namespace of the mount the inode was found from
492 * @fs_userns: user namespace of the filesystem
494 * If the inode has been found through an idmapped mount the user namespace of
495 * the vfsmount must be passed through @mnt_userns. This function will then
496 * take care to map the inode according to @mnt_userns before checking
497 * permissions. On non-idmapped mounts or if permission checking is to be
498 * performed on the raw inode simply passs init_user_ns.
500 static kuid_t
rootid_from_xattr(const void *value
, size_t size
,
501 struct user_namespace
*task_ns
,
502 struct user_namespace
*mnt_userns
,
503 struct user_namespace
*fs_userns
)
505 const struct vfs_ns_cap_data
*nscap
= value
;
509 if (size
== XATTR_CAPS_SZ_3
)
510 rootid
= le32_to_cpu(nscap
->rootid
);
512 rootkid
= make_kuid(task_ns
, rootid
);
513 return mapped_kuid_user(mnt_userns
, fs_userns
, rootkid
);
516 static bool validheader(size_t size
, const struct vfs_cap_data
*cap
)
518 return is_v2header(size
, cap
) || is_v3header(size
, cap
);
522 * cap_convert_nscap - check vfs caps
524 * @mnt_userns: user namespace of the mount the inode was found from
525 * @dentry: used to retrieve inode to check permissions on
526 * @ivalue: vfs caps value which may be modified by this function
527 * @size: size of @ivalue
529 * User requested a write of security.capability. If needed, update the
530 * xattr to change from v2 to v3, or to fixup the v3 rootid.
532 * If the inode has been found through an idmapped mount the user namespace of
533 * the vfsmount must be passed through @mnt_userns. This function will then
534 * take care to map the inode according to @mnt_userns before checking
535 * permissions. On non-idmapped mounts or if permission checking is to be
536 * performed on the raw inode simply passs init_user_ns.
538 * Return: On success, return the new size; on error, return < 0.
540 int cap_convert_nscap(struct user_namespace
*mnt_userns
, struct dentry
*dentry
,
541 const void **ivalue
, size_t size
)
543 struct vfs_ns_cap_data
*nscap
;
545 const struct vfs_cap_data
*cap
= *ivalue
;
546 __u32 magic
, nsmagic
;
547 struct inode
*inode
= d_backing_inode(dentry
);
548 struct user_namespace
*task_ns
= current_user_ns(),
549 *fs_ns
= inode
->i_sb
->s_user_ns
;
555 if (!validheader(size
, cap
))
557 if (!capable_wrt_inode_uidgid(mnt_userns
, inode
, CAP_SETFCAP
))
559 if (size
== XATTR_CAPS_SZ_2
&& (mnt_userns
== fs_ns
))
560 if (ns_capable(inode
->i_sb
->s_user_ns
, CAP_SETFCAP
))
561 /* user is privileged, just write the v2 */
564 rootid
= rootid_from_xattr(*ivalue
, size
, task_ns
, mnt_userns
, fs_ns
);
565 if (!uid_valid(rootid
))
568 nsrootid
= from_kuid(fs_ns
, rootid
);
572 newsize
= sizeof(struct vfs_ns_cap_data
);
573 nscap
= kmalloc(newsize
, GFP_ATOMIC
);
576 nscap
->rootid
= cpu_to_le32(nsrootid
);
577 nsmagic
= VFS_CAP_REVISION_3
;
578 magic
= le32_to_cpu(cap
->magic_etc
);
579 if (magic
& VFS_CAP_FLAGS_EFFECTIVE
)
580 nsmagic
|= VFS_CAP_FLAGS_EFFECTIVE
;
581 nscap
->magic_etc
= cpu_to_le32(nsmagic
);
582 memcpy(&nscap
->data
, &cap
->data
, sizeof(__le32
) * 2 * VFS_CAP_U32
);
589 * Calculate the new process capability sets from the capability sets attached
592 static inline int bprm_caps_from_vfs_caps(struct cpu_vfs_cap_data
*caps
,
593 struct linux_binprm
*bprm
,
597 struct cred
*new = bprm
->cred
;
601 if (caps
->magic_etc
& VFS_CAP_FLAGS_EFFECTIVE
)
604 if (caps
->magic_etc
& VFS_CAP_REVISION_MASK
)
607 CAP_FOR_EACH_U32(i
) {
608 __u32 permitted
= caps
->permitted
.cap
[i
];
609 __u32 inheritable
= caps
->inheritable
.cap
[i
];
612 * pP' = (X & fP) | (pI & fI)
613 * The addition of pA' is handled later.
615 new->cap_permitted
.cap
[i
] =
616 (new->cap_bset
.cap
[i
] & permitted
) |
617 (new->cap_inheritable
.cap
[i
] & inheritable
);
619 if (permitted
& ~new->cap_permitted
.cap
[i
])
620 /* insufficient to execute correctly */
625 * For legacy apps, with no internal support for recognizing they
626 * do not have enough capabilities, we return an error if they are
627 * missing some "forced" (aka file-permitted) capabilities.
629 return *effective
? ret
: 0;
633 * get_vfs_caps_from_disk - retrieve vfs caps from disk
635 * @mnt_userns: user namespace of the mount the inode was found from
636 * @dentry: dentry from which @inode is retrieved
637 * @cpu_caps: vfs capabilities
639 * Extract the on-exec-apply capability sets for an executable file.
641 * If the inode has been found through an idmapped mount the user namespace of
642 * the vfsmount must be passed through @mnt_userns. This function will then
643 * take care to map the inode according to @mnt_userns before checking
644 * permissions. On non-idmapped mounts or if permission checking is to be
645 * performed on the raw inode simply passs init_user_ns.
647 int get_vfs_caps_from_disk(struct user_namespace
*mnt_userns
,
648 const struct dentry
*dentry
,
649 struct cpu_vfs_cap_data
*cpu_caps
)
651 struct inode
*inode
= d_backing_inode(dentry
);
655 struct vfs_ns_cap_data data
, *nscaps
= &data
;
656 struct vfs_cap_data
*caps
= (struct vfs_cap_data
*) &data
;
658 struct user_namespace
*fs_ns
;
660 memset(cpu_caps
, 0, sizeof(struct cpu_vfs_cap_data
));
665 fs_ns
= inode
->i_sb
->s_user_ns
;
666 size
= __vfs_getxattr((struct dentry
*)dentry
, inode
,
667 XATTR_NAME_CAPS
, &data
, XATTR_CAPS_SZ
);
668 if (size
== -ENODATA
|| size
== -EOPNOTSUPP
)
669 /* no data, that's ok */
675 if (size
< sizeof(magic_etc
))
678 cpu_caps
->magic_etc
= magic_etc
= le32_to_cpu(caps
->magic_etc
);
680 rootkuid
= make_kuid(fs_ns
, 0);
681 switch (magic_etc
& VFS_CAP_REVISION_MASK
) {
682 case VFS_CAP_REVISION_1
:
683 if (size
!= XATTR_CAPS_SZ_1
)
685 tocopy
= VFS_CAP_U32_1
;
687 case VFS_CAP_REVISION_2
:
688 if (size
!= XATTR_CAPS_SZ_2
)
690 tocopy
= VFS_CAP_U32_2
;
692 case VFS_CAP_REVISION_3
:
693 if (size
!= XATTR_CAPS_SZ_3
)
695 tocopy
= VFS_CAP_U32_3
;
696 rootkuid
= make_kuid(fs_ns
, le32_to_cpu(nscaps
->rootid
));
702 /* Limit the caps to the mounter of the filesystem
703 * or the more limited uid specified in the xattr.
705 rootkuid
= mapped_kuid_fs(mnt_userns
, fs_ns
, rootkuid
);
706 if (!rootid_owns_currentns(rootkuid
))
709 CAP_FOR_EACH_U32(i
) {
712 cpu_caps
->permitted
.cap
[i
] = le32_to_cpu(caps
->data
[i
].permitted
);
713 cpu_caps
->inheritable
.cap
[i
] = le32_to_cpu(caps
->data
[i
].inheritable
);
716 cpu_caps
->permitted
.cap
[CAP_LAST_U32
] &= CAP_LAST_U32_VALID_MASK
;
717 cpu_caps
->inheritable
.cap
[CAP_LAST_U32
] &= CAP_LAST_U32_VALID_MASK
;
719 cpu_caps
->rootid
= rootkuid
;
725 * Attempt to get the on-exec apply capability sets for an executable file from
726 * its xattrs and, if present, apply them to the proposed credentials being
727 * constructed by execve().
729 static int get_file_caps(struct linux_binprm
*bprm
, struct file
*file
,
730 bool *effective
, bool *has_fcap
)
733 struct cpu_vfs_cap_data vcaps
;
735 cap_clear(bprm
->cred
->cap_permitted
);
737 if (!file_caps_enabled
)
740 if (!mnt_may_suid(file
->f_path
.mnt
))
744 * This check is redundant with mnt_may_suid() but is kept to make
745 * explicit that capability bits are limited to s_user_ns and its
748 if (!current_in_userns(file
->f_path
.mnt
->mnt_sb
->s_user_ns
))
751 rc
= get_vfs_caps_from_disk(file_mnt_user_ns(file
),
752 file
->f_path
.dentry
, &vcaps
);
755 printk(KERN_NOTICE
"Invalid argument reading file caps for %s\n",
757 else if (rc
== -ENODATA
)
762 rc
= bprm_caps_from_vfs_caps(&vcaps
, bprm
, effective
, has_fcap
);
766 cap_clear(bprm
->cred
->cap_permitted
);
771 static inline bool root_privileged(void) { return !issecure(SECURE_NOROOT
); }
773 static inline bool __is_real(kuid_t uid
, struct cred
*cred
)
774 { return uid_eq(cred
->uid
, uid
); }
776 static inline bool __is_eff(kuid_t uid
, struct cred
*cred
)
777 { return uid_eq(cred
->euid
, uid
); }
779 static inline bool __is_suid(kuid_t uid
, struct cred
*cred
)
780 { return !__is_real(uid
, cred
) && __is_eff(uid
, cred
); }
783 * handle_privileged_root - Handle case of privileged root
784 * @bprm: The execution parameters, including the proposed creds
785 * @has_fcap: Are any file capabilities set?
786 * @effective: Do we have effective root privilege?
787 * @root_uid: This namespace' root UID WRT initial USER namespace
789 * Handle the case where root is privileged and hasn't been neutered by
790 * SECURE_NOROOT. If file capabilities are set, they won't be combined with
791 * set UID root and nothing is changed. If we are root, cap_permitted is
792 * updated. If we have become set UID root, the effective bit is set.
794 static void handle_privileged_root(struct linux_binprm
*bprm
, bool has_fcap
,
795 bool *effective
, kuid_t root_uid
)
797 const struct cred
*old
= current_cred();
798 struct cred
*new = bprm
->cred
;
800 if (!root_privileged())
803 * If the legacy file capability is set, then don't set privs
804 * for a setuid root binary run by a non-root user. Do set it
805 * for a root user just to cause least surprise to an admin.
807 if (has_fcap
&& __is_suid(root_uid
, new)) {
808 warn_setuid_and_fcaps_mixed(bprm
->filename
);
812 * To support inheritance of root-permissions and suid-root
813 * executables under compatibility mode, we override the
814 * capability sets for the file.
816 if (__is_eff(root_uid
, new) || __is_real(root_uid
, new)) {
817 /* pP' = (cap_bset & ~0) | (pI & ~0) */
818 new->cap_permitted
= cap_combine(old
->cap_bset
,
819 old
->cap_inheritable
);
822 * If only the real uid is 0, we do not set the effective bit.
824 if (__is_eff(root_uid
, new))
828 #define __cap_gained(field, target, source) \
829 !cap_issubset(target->cap_##field, source->cap_##field)
830 #define __cap_grew(target, source, cred) \
831 !cap_issubset(cred->cap_##target, cred->cap_##source)
832 #define __cap_full(field, cred) \
833 cap_issubset(CAP_FULL_SET, cred->cap_##field)
835 static inline bool __is_setuid(struct cred
*new, const struct cred
*old
)
836 { return !uid_eq(new->euid
, old
->uid
); }
838 static inline bool __is_setgid(struct cred
*new, const struct cred
*old
)
839 { return !gid_eq(new->egid
, old
->gid
); }
842 * 1) Audit candidate if current->cap_effective is set
844 * We do not bother to audit if 3 things are true:
845 * 1) cap_effective has all caps
846 * 2) we became root *OR* are were already root
847 * 3) root is supposed to have all caps (SECURE_NOROOT)
848 * Since this is just a normal root execing a process.
850 * Number 1 above might fail if you don't have a full bset, but I think
851 * that is interesting information to audit.
853 * A number of other conditions require logging:
854 * 2) something prevented setuid root getting all caps
855 * 3) non-setuid root gets fcaps
856 * 4) non-setuid root gets ambient
858 static inline bool nonroot_raised_pE(struct cred
*new, const struct cred
*old
,
859 kuid_t root
, bool has_fcap
)
863 if ((__cap_grew(effective
, ambient
, new) &&
864 !(__cap_full(effective
, new) &&
865 (__is_eff(root
, new) || __is_real(root
, new)) &&
866 root_privileged())) ||
867 (root_privileged() &&
868 __is_suid(root
, new) &&
869 !__cap_full(effective
, new)) ||
870 (!__is_setuid(new, old
) &&
872 __cap_gained(permitted
, new, old
)) ||
873 __cap_gained(ambient
, new, old
))))
881 * cap_bprm_creds_from_file - Set up the proposed credentials for execve().
882 * @bprm: The execution parameters, including the proposed creds
883 * @file: The file to pull the credentials from
885 * Set up the proposed credentials for a new execution context being
886 * constructed by execve(). The proposed creds in @bprm->cred is altered,
887 * which won't take effect immediately.
889 * Return: 0 if successful, -ve on error.
891 int cap_bprm_creds_from_file(struct linux_binprm
*bprm
, struct file
*file
)
893 /* Process setpcap binaries and capabilities for uid 0 */
894 const struct cred
*old
= current_cred();
895 struct cred
*new = bprm
->cred
;
896 bool effective
= false, has_fcap
= false, is_setid
;
900 if (WARN_ON(!cap_ambient_invariant_ok(old
)))
903 ret
= get_file_caps(bprm
, file
, &effective
, &has_fcap
);
907 root_uid
= make_kuid(new->user_ns
, 0);
909 handle_privileged_root(bprm
, has_fcap
, &effective
, root_uid
);
911 /* if we have fs caps, clear dangerous personality flags */
912 if (__cap_gained(permitted
, new, old
))
913 bprm
->per_clear
|= PER_CLEAR_ON_SETID
;
915 /* Don't let someone trace a set[ug]id/setpcap binary with the revised
916 * credentials unless they have the appropriate permit.
918 * In addition, if NO_NEW_PRIVS, then ensure we get no new privs.
920 is_setid
= __is_setuid(new, old
) || __is_setgid(new, old
);
922 if ((is_setid
|| __cap_gained(permitted
, new, old
)) &&
923 ((bprm
->unsafe
& ~LSM_UNSAFE_PTRACE
) ||
924 !ptracer_capable(current
, new->user_ns
))) {
925 /* downgrade; they get no more than they had, and maybe less */
926 if (!ns_capable(new->user_ns
, CAP_SETUID
) ||
927 (bprm
->unsafe
& LSM_UNSAFE_NO_NEW_PRIVS
)) {
928 new->euid
= new->uid
;
929 new->egid
= new->gid
;
931 new->cap_permitted
= cap_intersect(new->cap_permitted
,
935 new->suid
= new->fsuid
= new->euid
;
936 new->sgid
= new->fsgid
= new->egid
;
938 /* File caps or setid cancels ambient. */
939 if (has_fcap
|| is_setid
)
940 cap_clear(new->cap_ambient
);
943 * Now that we've computed pA', update pP' to give:
944 * pP' = (X & fP) | (pI & fI) | pA'
946 new->cap_permitted
= cap_combine(new->cap_permitted
, new->cap_ambient
);
949 * Set pE' = (fE ? pP' : pA'). Because pA' is zero if fE is set,
950 * this is the same as pE' = (fE ? pP' : 0) | pA'.
953 new->cap_effective
= new->cap_permitted
;
955 new->cap_effective
= new->cap_ambient
;
957 if (WARN_ON(!cap_ambient_invariant_ok(new)))
960 if (nonroot_raised_pE(new, old
, root_uid
, has_fcap
)) {
961 ret
= audit_log_bprm_fcaps(bprm
, new, old
);
966 new->securebits
&= ~issecure_mask(SECURE_KEEP_CAPS
);
968 if (WARN_ON(!cap_ambient_invariant_ok(new)))
971 /* Check for privilege-elevated exec. */
973 (!__is_real(root_uid
, new) &&
975 __cap_grew(permitted
, ambient
, new))))
976 bprm
->secureexec
= 1;
982 * cap_inode_setxattr - Determine whether an xattr may be altered
983 * @dentry: The inode/dentry being altered
984 * @name: The name of the xattr to be changed
985 * @value: The value that the xattr will be changed to
986 * @size: The size of value
987 * @flags: The replacement flag
989 * Determine whether an xattr may be altered or set on an inode, returning 0 if
990 * permission is granted, -ve if denied.
992 * This is used to make sure security xattrs don't get updated or set by those
993 * who aren't privileged to do so.
995 int cap_inode_setxattr(struct dentry
*dentry
, const char *name
,
996 const void *value
, size_t size
, int flags
)
998 struct user_namespace
*user_ns
= dentry
->d_sb
->s_user_ns
;
1000 /* Ignore non-security xattrs */
1001 if (strncmp(name
, XATTR_SECURITY_PREFIX
,
1002 XATTR_SECURITY_PREFIX_LEN
) != 0)
1006 * For XATTR_NAME_CAPS the check will be done in
1007 * cap_convert_nscap(), called by setxattr()
1009 if (strcmp(name
, XATTR_NAME_CAPS
) == 0)
1012 if (!ns_capable(user_ns
, CAP_SYS_ADMIN
))
1018 * cap_inode_removexattr - Determine whether an xattr may be removed
1020 * @mnt_userns: User namespace of the mount the inode was found from
1021 * @dentry: The inode/dentry being altered
1022 * @name: The name of the xattr to be changed
1024 * Determine whether an xattr may be removed from an inode, returning 0 if
1025 * permission is granted, -ve if denied.
1027 * If the inode has been found through an idmapped mount the user namespace of
1028 * the vfsmount must be passed through @mnt_userns. This function will then
1029 * take care to map the inode according to @mnt_userns before checking
1030 * permissions. On non-idmapped mounts or if permission checking is to be
1031 * performed on the raw inode simply passs init_user_ns.
1033 * This is used to make sure security xattrs don't get removed by those who
1034 * aren't privileged to remove them.
1036 int cap_inode_removexattr(struct user_namespace
*mnt_userns
,
1037 struct dentry
*dentry
, const char *name
)
1039 struct user_namespace
*user_ns
= dentry
->d_sb
->s_user_ns
;
1041 /* Ignore non-security xattrs */
1042 if (strncmp(name
, XATTR_SECURITY_PREFIX
,
1043 XATTR_SECURITY_PREFIX_LEN
) != 0)
1046 if (strcmp(name
, XATTR_NAME_CAPS
) == 0) {
1047 /* security.capability gets namespaced */
1048 struct inode
*inode
= d_backing_inode(dentry
);
1051 if (!capable_wrt_inode_uidgid(mnt_userns
, inode
, CAP_SETFCAP
))
1056 if (!ns_capable(user_ns
, CAP_SYS_ADMIN
))
1062 * cap_emulate_setxuid() fixes the effective / permitted capabilities of
1063 * a process after a call to setuid, setreuid, or setresuid.
1065 * 1) When set*uiding _from_ one of {r,e,s}uid == 0 _to_ all of
1066 * {r,e,s}uid != 0, the permitted and effective capabilities are
1069 * 2) When set*uiding _from_ euid == 0 _to_ euid != 0, the effective
1070 * capabilities of the process are cleared.
1072 * 3) When set*uiding _from_ euid != 0 _to_ euid == 0, the effective
1073 * capabilities are set to the permitted capabilities.
1075 * fsuid is handled elsewhere. fsuid == 0 and {r,e,s}uid!= 0 should
1080 * cevans - New behaviour, Oct '99
1081 * A process may, via prctl(), elect to keep its capabilities when it
1082 * calls setuid() and switches away from uid==0. Both permitted and
1083 * effective sets will be retained.
1084 * Without this change, it was impossible for a daemon to drop only some
1085 * of its privilege. The call to setuid(!=0) would drop all privileges!
1086 * Keeping uid 0 is not an option because uid 0 owns too many vital
1088 * Thanks to Olaf Kirch and Peter Benie for spotting this.
1090 static inline void cap_emulate_setxuid(struct cred
*new, const struct cred
*old
)
1092 kuid_t root_uid
= make_kuid(old
->user_ns
, 0);
1094 if ((uid_eq(old
->uid
, root_uid
) ||
1095 uid_eq(old
->euid
, root_uid
) ||
1096 uid_eq(old
->suid
, root_uid
)) &&
1097 (!uid_eq(new->uid
, root_uid
) &&
1098 !uid_eq(new->euid
, root_uid
) &&
1099 !uid_eq(new->suid
, root_uid
))) {
1100 if (!issecure(SECURE_KEEP_CAPS
)) {
1101 cap_clear(new->cap_permitted
);
1102 cap_clear(new->cap_effective
);
1106 * Pre-ambient programs expect setresuid to nonroot followed
1107 * by exec to drop capabilities. We should make sure that
1108 * this remains the case.
1110 cap_clear(new->cap_ambient
);
1112 if (uid_eq(old
->euid
, root_uid
) && !uid_eq(new->euid
, root_uid
))
1113 cap_clear(new->cap_effective
);
1114 if (!uid_eq(old
->euid
, root_uid
) && uid_eq(new->euid
, root_uid
))
1115 new->cap_effective
= new->cap_permitted
;
1119 * cap_task_fix_setuid - Fix up the results of setuid() call
1120 * @new: The proposed credentials
1121 * @old: The current task's current credentials
1122 * @flags: Indications of what has changed
1124 * Fix up the results of setuid() call before the credential changes are
1127 * Return: 0 to grant the changes, -ve to deny them.
1129 int cap_task_fix_setuid(struct cred
*new, const struct cred
*old
, int flags
)
1135 /* juggle the capabilities to follow [RES]UID changes unless
1136 * otherwise suppressed */
1137 if (!issecure(SECURE_NO_SETUID_FIXUP
))
1138 cap_emulate_setxuid(new, old
);
1142 /* juggle the capabilties to follow FSUID changes, unless
1143 * otherwise suppressed
1145 * FIXME - is fsuser used for all CAP_FS_MASK capabilities?
1146 * if not, we might be a bit too harsh here.
1148 if (!issecure(SECURE_NO_SETUID_FIXUP
)) {
1149 kuid_t root_uid
= make_kuid(old
->user_ns
, 0);
1150 if (uid_eq(old
->fsuid
, root_uid
) && !uid_eq(new->fsuid
, root_uid
))
1151 new->cap_effective
=
1152 cap_drop_fs_set(new->cap_effective
);
1154 if (!uid_eq(old
->fsuid
, root_uid
) && uid_eq(new->fsuid
, root_uid
))
1155 new->cap_effective
=
1156 cap_raise_fs_set(new->cap_effective
,
1157 new->cap_permitted
);
1169 * Rationale: code calling task_setscheduler, task_setioprio, and
1170 * task_setnice, assumes that
1171 * . if capable(cap_sys_nice), then those actions should be allowed
1172 * . if not capable(cap_sys_nice), but acting on your own processes,
1173 * then those actions should be allowed
1174 * This is insufficient now since you can call code without suid, but
1175 * yet with increased caps.
1176 * So we check for increased caps on the target process.
1178 static int cap_safe_nice(struct task_struct
*p
)
1180 int is_subset
, ret
= 0;
1183 is_subset
= cap_issubset(__task_cred(p
)->cap_permitted
,
1184 current_cred()->cap_permitted
);
1185 if (!is_subset
&& !ns_capable(__task_cred(p
)->user_ns
, CAP_SYS_NICE
))
1193 * cap_task_setscheduler - Detemine if scheduler policy change is permitted
1194 * @p: The task to affect
1196 * Detemine if the requested scheduler policy change is permitted for the
1199 * Return: 0 if permission is granted, -ve if denied.
1201 int cap_task_setscheduler(struct task_struct
*p
)
1203 return cap_safe_nice(p
);
1207 * cap_task_setioprio - Detemine if I/O priority change is permitted
1208 * @p: The task to affect
1209 * @ioprio: The I/O priority to set
1211 * Detemine if the requested I/O priority change is permitted for the specified
1214 * Return: 0 if permission is granted, -ve if denied.
1216 int cap_task_setioprio(struct task_struct
*p
, int ioprio
)
1218 return cap_safe_nice(p
);
1222 * cap_task_setnice - Detemine if task priority change is permitted
1223 * @p: The task to affect
1224 * @nice: The nice value to set
1226 * Detemine if the requested task priority change is permitted for the
1229 * Return: 0 if permission is granted, -ve if denied.
1231 int cap_task_setnice(struct task_struct
*p
, int nice
)
1233 return cap_safe_nice(p
);
1237 * Implement PR_CAPBSET_DROP. Attempt to remove the specified capability from
1238 * the current task's bounding set. Returns 0 on success, -ve on error.
1240 static int cap_prctl_drop(unsigned long cap
)
1244 if (!ns_capable(current_user_ns(), CAP_SETPCAP
))
1246 if (!cap_valid(cap
))
1249 new = prepare_creds();
1252 cap_lower(new->cap_bset
, cap
);
1253 return commit_creds(new);
1257 * cap_task_prctl - Implement process control functions for this security module
1258 * @option: The process control function requested
1259 * @arg2: The argument data for this function
1260 * @arg3: The argument data for this function
1261 * @arg4: The argument data for this function
1262 * @arg5: The argument data for this function
1264 * Allow process control functions (sys_prctl()) to alter capabilities; may
1265 * also deny access to other functions not otherwise implemented here.
1267 * Return: 0 or +ve on success, -ENOSYS if this function is not implemented
1268 * here, other -ve on error. If -ENOSYS is returned, sys_prctl() and other LSM
1269 * modules will consider performing the function.
1271 int cap_task_prctl(int option
, unsigned long arg2
, unsigned long arg3
,
1272 unsigned long arg4
, unsigned long arg5
)
1274 const struct cred
*old
= current_cred();
1278 case PR_CAPBSET_READ
:
1279 if (!cap_valid(arg2
))
1281 return !!cap_raised(old
->cap_bset
, arg2
);
1283 case PR_CAPBSET_DROP
:
1284 return cap_prctl_drop(arg2
);
1287 * The next four prctl's remain to assist with transitioning a
1288 * system from legacy UID=0 based privilege (when filesystem
1289 * capabilities are not in use) to a system using filesystem
1290 * capabilities only - as the POSIX.1e draft intended.
1294 * PR_SET_SECUREBITS =
1295 * issecure_mask(SECURE_KEEP_CAPS_LOCKED)
1296 * | issecure_mask(SECURE_NOROOT)
1297 * | issecure_mask(SECURE_NOROOT_LOCKED)
1298 * | issecure_mask(SECURE_NO_SETUID_FIXUP)
1299 * | issecure_mask(SECURE_NO_SETUID_FIXUP_LOCKED)
1301 * will ensure that the current process and all of its
1302 * children will be locked into a pure
1303 * capability-based-privilege environment.
1305 case PR_SET_SECUREBITS
:
1306 if ((((old
->securebits
& SECURE_ALL_LOCKS
) >> 1)
1307 & (old
->securebits
^ arg2
)) /*[1]*/
1308 || ((old
->securebits
& SECURE_ALL_LOCKS
& ~arg2
)) /*[2]*/
1309 || (arg2
& ~(SECURE_ALL_LOCKS
| SECURE_ALL_BITS
)) /*[3]*/
1310 || (cap_capable(current_cred(),
1311 current_cred()->user_ns
,
1313 CAP_OPT_NONE
) != 0) /*[4]*/
1315 * [1] no changing of bits that are locked
1316 * [2] no unlocking of locks
1317 * [3] no setting of unsupported bits
1318 * [4] doing anything requires privilege (go read about
1319 * the "sendmail capabilities bug")
1322 /* cannot change a locked bit */
1325 new = prepare_creds();
1328 new->securebits
= arg2
;
1329 return commit_creds(new);
1331 case PR_GET_SECUREBITS
:
1332 return old
->securebits
;
1334 case PR_GET_KEEPCAPS
:
1335 return !!issecure(SECURE_KEEP_CAPS
);
1337 case PR_SET_KEEPCAPS
:
1338 if (arg2
> 1) /* Note, we rely on arg2 being unsigned here */
1340 if (issecure(SECURE_KEEP_CAPS_LOCKED
))
1343 new = prepare_creds();
1347 new->securebits
|= issecure_mask(SECURE_KEEP_CAPS
);
1349 new->securebits
&= ~issecure_mask(SECURE_KEEP_CAPS
);
1350 return commit_creds(new);
1352 case PR_CAP_AMBIENT
:
1353 if (arg2
== PR_CAP_AMBIENT_CLEAR_ALL
) {
1354 if (arg3
| arg4
| arg5
)
1357 new = prepare_creds();
1360 cap_clear(new->cap_ambient
);
1361 return commit_creds(new);
1364 if (((!cap_valid(arg3
)) | arg4
| arg5
))
1367 if (arg2
== PR_CAP_AMBIENT_IS_SET
) {
1368 return !!cap_raised(current_cred()->cap_ambient
, arg3
);
1369 } else if (arg2
!= PR_CAP_AMBIENT_RAISE
&&
1370 arg2
!= PR_CAP_AMBIENT_LOWER
) {
1373 if (arg2
== PR_CAP_AMBIENT_RAISE
&&
1374 (!cap_raised(current_cred()->cap_permitted
, arg3
) ||
1375 !cap_raised(current_cred()->cap_inheritable
,
1377 issecure(SECURE_NO_CAP_AMBIENT_RAISE
)))
1380 new = prepare_creds();
1383 if (arg2
== PR_CAP_AMBIENT_RAISE
)
1384 cap_raise(new->cap_ambient
, arg3
);
1386 cap_lower(new->cap_ambient
, arg3
);
1387 return commit_creds(new);
1391 /* No functionality available - continue with default */
1397 * cap_vm_enough_memory - Determine whether a new virtual mapping is permitted
1398 * @mm: The VM space in which the new mapping is to be made
1399 * @pages: The size of the mapping
1401 * Determine whether the allocation of a new virtual mapping by the current
1402 * task is permitted.
1404 * Return: 1 if permission is granted, 0 if not.
1406 int cap_vm_enough_memory(struct mm_struct
*mm
, long pages
)
1408 int cap_sys_admin
= 0;
1410 if (cap_capable(current_cred(), &init_user_ns
,
1411 CAP_SYS_ADMIN
, CAP_OPT_NOAUDIT
) == 0)
1414 return cap_sys_admin
;
1418 * cap_mmap_addr - check if able to map given addr
1419 * @addr: address attempting to be mapped
1421 * If the process is attempting to map memory below dac_mmap_min_addr they need
1422 * CAP_SYS_RAWIO. The other parameters to this function are unused by the
1423 * capability security module.
1425 * Return: 0 if this mapping should be allowed or -EPERM if not.
1427 int cap_mmap_addr(unsigned long addr
)
1431 if (addr
< dac_mmap_min_addr
) {
1432 ret
= cap_capable(current_cred(), &init_user_ns
, CAP_SYS_RAWIO
,
1434 /* set PF_SUPERPRIV if it turns out we allow the low mmap */
1436 current
->flags
|= PF_SUPERPRIV
;
1441 int cap_mmap_file(struct file
*file
, unsigned long reqprot
,
1442 unsigned long prot
, unsigned long flags
)
1447 #ifdef CONFIG_SECURITY
1449 static struct lsm_id capability_lsmid __lsm_ro_after_init
= {
1450 .lsm
= "capability",
1451 .slot
= LSMBLOB_NOT_NEEDED
1454 static struct security_hook_list capability_hooks
[] __lsm_ro_after_init
= {
1455 LSM_HOOK_INIT(capable
, cap_capable
),
1456 LSM_HOOK_INIT(settime
, cap_settime
),
1457 LSM_HOOK_INIT(ptrace_access_check
, cap_ptrace_access_check
),
1458 LSM_HOOK_INIT(ptrace_traceme
, cap_ptrace_traceme
),
1459 LSM_HOOK_INIT(capget
, cap_capget
),
1460 LSM_HOOK_INIT(capset
, cap_capset
),
1461 LSM_HOOK_INIT(bprm_creds_from_file
, cap_bprm_creds_from_file
),
1462 LSM_HOOK_INIT(inode_need_killpriv
, cap_inode_need_killpriv
),
1463 LSM_HOOK_INIT(inode_killpriv
, cap_inode_killpriv
),
1464 LSM_HOOK_INIT(inode_getsecurity
, cap_inode_getsecurity
),
1465 LSM_HOOK_INIT(mmap_addr
, cap_mmap_addr
),
1466 LSM_HOOK_INIT(mmap_file
, cap_mmap_file
),
1467 LSM_HOOK_INIT(task_fix_setuid
, cap_task_fix_setuid
),
1468 LSM_HOOK_INIT(task_prctl
, cap_task_prctl
),
1469 LSM_HOOK_INIT(task_setscheduler
, cap_task_setscheduler
),
1470 LSM_HOOK_INIT(task_setioprio
, cap_task_setioprio
),
1471 LSM_HOOK_INIT(task_setnice
, cap_task_setnice
),
1472 LSM_HOOK_INIT(vm_enough_memory
, cap_vm_enough_memory
),
1475 static int __init
capability_init(void)
1477 security_add_hooks(capability_hooks
, ARRAY_SIZE(capability_hooks
),
1482 DEFINE_LSM(capability
) = {
1483 .name
= "capability",
1484 .order
= LSM_ORDER_FIRST
,
1485 .init
= capability_init
,
1488 #endif /* CONFIG_SECURITY */