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>
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.
37 * Warn if that happens, once per boot.
39 static void warn_setuid_and_fcaps_mixed(const char *fname
)
43 printk(KERN_INFO
"warning: `%s' has both setuid-root and"
44 " effective capabilities. Therefore not raising all"
45 " capabilities.\n", fname
);
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
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.
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.
65 int cap_capable(const struct cred
*cred
, struct user_namespace
*targ_ns
,
66 int cap
, unsigned int opts
)
68 struct user_namespace
*ns
= targ_ns
;
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.
75 /* Do we have the necessary capabilities? */
76 if (ns
== cred
->user_ns
)
77 return cap_raised(cred
->cap_effective
, cap
) ? 0 : -EPERM
;
80 * If we're already at a lower level than we're looking for,
81 * we're done searching.
83 if (ns
->level
<= cred
->user_ns
->level
)
87 * The owner of the user namespace in the parent of the
88 * user namespace has all caps.
90 if ((ns
->parent
== cred
->user_ns
) && uid_eq(ns
->owner
, cred
->euid
))
94 * If you have a capability in a parent user ns, then you have
95 * it over all children user namespaces as well.
100 /* We never get here */
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
108 * Determine whether the current process may set the system clock and timezone
109 * information, returning 0 if permission granted, -ve if denied.
111 int cap_settime(const struct timespec64
*ts
, const struct timezone
*tz
)
113 if (!capable(CAP_SYS_TIME
))
119 * cap_ptrace_access_check - Determine whether the current process may access
121 * @child: The process to be accessed
122 * @mode: The mode of attachment.
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
130 * Determine whether a process may access another, returning 0 if permission
131 * granted, -ve if denied.
133 int cap_ptrace_access_check(struct task_struct
*child
, unsigned int mode
)
136 const struct cred
*cred
, *child_cred
;
137 const kernel_cap_t
*caller_caps
;
140 cred
= current_cred();
141 child_cred
= __task_cred(child
);
142 if (mode
& PTRACE_MODE_FSCREDS
)
143 caller_caps
= &cred
->cap_effective
;
145 caller_caps
= &cred
->cap_permitted
;
146 if (cred
->user_ns
== child_cred
->user_ns
&&
147 cap_issubset(child_cred
->cap_permitted
, *caller_caps
))
149 if (ns_capable(child_cred
->user_ns
, CAP_SYS_PTRACE
))
158 * cap_ptrace_traceme - Determine whether another process may trace the current
159 * @parent: The task proposed to be the tracer
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
167 * Determine whether the nominated task is permitted to trace the current
168 * process, returning 0 if permission is granted, -ve if denied.
170 int cap_ptrace_traceme(struct task_struct
*parent
)
173 const struct cred
*cred
, *child_cred
;
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
))
181 if (has_ns_capability(parent
, child_cred
->user_ns
, CAP_SYS_PTRACE
))
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
196 * This function retrieves the capabilities of the nominated task and returns
197 * them to the caller.
199 int cap_capget(struct task_struct
*target
, kernel_cap_t
*effective
,
200 kernel_cap_t
*inheritable
, kernel_cap_t
*permitted
)
202 const struct cred
*cred
;
204 /* Derived from kernel/capability.c:sys_capget. */
206 cred
= __task_cred(target
);
207 *effective
= cred
->cap_effective
;
208 *inheritable
= cred
->cap_inheritable
;
209 *permitted
= cred
->cap_permitted
;
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.
218 static inline int cap_inh_is_capped(void)
220 /* they are so limited unless the current task has the CAP_SETPCAP
223 if (cap_capable(current_cred(), current_cred()->user_ns
,
224 CAP_SETPCAP
, CAP_OPT_NONE
) == 0)
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
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.
241 int 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
)
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 */
254 if (!cap_issubset(*inheritable
,
255 cap_combine(old
->cap_inheritable
,
257 /* no new pI capabilities outside bounding set */
260 /* verify restrictions on target's new Permitted set */
261 if (!cap_issubset(*permitted
, old
->cap_permitted
))
264 /* verify the _new_Effective_ is a subset of the _new_Permitted_ */
265 if (!cap_issubset(*effective
, *permitted
))
268 new->cap_effective
= *effective
;
269 new->cap_inheritable
= *inheritable
;
270 new->cap_permitted
= *permitted
;
273 * Mask off ambient bits that are no longer both permitted and
276 new->cap_ambient
= cap_intersect(new->cap_ambient
,
277 cap_intersect(*permitted
,
279 if (WARN_ON(!cap_ambient_invariant_ok(new)))
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
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.
292 * Return: 1 if security.capability has a value, meaning inode_killpriv()
293 * is required, 0 otherwise, meaning inode_killpriv() is not required.
295 int cap_inode_need_killpriv(struct dentry
*dentry
)
297 struct inode
*inode
= d_backing_inode(dentry
);
300 error
= __vfs_getxattr(dentry
, inode
, XATTR_NAME_CAPS
, NULL
, 0);
305 * cap_inode_killpriv - Erase the security markings on an inode
307 * @mnt_userns: user namespace of the mount the inode was found from
308 * @dentry: The inode/dentry to alter
310 * Erase the privilege-enhancing security markings on an inode.
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.
318 * Return: 0 if successful, -ve on error.
320 int cap_inode_killpriv(struct user_namespace
*mnt_userns
, struct dentry
*dentry
)
324 error
= __vfs_removexattr(mnt_userns
, dentry
, XATTR_NAME_CAPS
);
325 if (error
== -EOPNOTSUPP
)
330 static bool rootid_owns_currentns(kuid_t kroot
)
332 struct user_namespace
*ns
;
334 if (!uid_valid(kroot
))
337 for (ns
= current_user_ns(); ; ns
= ns
->parent
) {
338 if (from_kuid(ns
, kroot
) == 0)
340 if (ns
== &init_user_ns
)
347 static __u32
sansflags(__u32 m
)
349 return m
& ~VFS_CAP_FLAGS_EFFECTIVE
;
352 static bool is_v2header(size_t size
, const struct vfs_cap_data
*cap
)
354 if (size
!= XATTR_CAPS_SZ_2
)
356 return sansflags(le32_to_cpu(cap
->magic_etc
)) == VFS_CAP_REVISION_2
;
359 static bool is_v3header(size_t size
, const struct vfs_cap_data
*cap
)
361 if (size
!= XATTR_CAPS_SZ_3
)
363 return sansflags(le32_to_cpu(cap
->magic_etc
)) == VFS_CAP_REVISION_3
;
367 * getsecurity: We are called for security.* before any attempt to read the
368 * xattr from the inode itself.
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.
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 -
377 int cap_inode_getsecurity(struct user_namespace
*mnt_userns
,
378 struct inode
*inode
, const char *name
, void **buffer
,
384 uid_t root
, mappedroot
;
386 struct vfs_cap_data
*cap
;
387 struct vfs_ns_cap_data
*nscap
= NULL
;
388 struct dentry
*dentry
;
389 struct user_namespace
*fs_ns
;
391 if (strcmp(name
, "capability") != 0)
394 dentry
= d_find_any_alias(inode
);
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
);
403 if (ret
< 0 || !tmpbuf
)
406 fs_ns
= inode
->i_sb
->s_user_ns
;
407 cap
= (struct vfs_cap_data
*) tmpbuf
;
408 if (is_v2header((size_t) ret
, cap
)) {
410 } else if (is_v3header((size_t) ret
, cap
)) {
411 nscap
= (struct vfs_ns_cap_data
*) tmpbuf
;
412 root
= le32_to_cpu(nscap
->rootid
);
418 kroot
= make_kuid(fs_ns
, root
);
420 /* If this is an idmapped mount shift the kuid. */
421 kroot
= kuid_into_mnt(mnt_userns
, kroot
);
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
);
430 /* v2 -> v3 conversion */
431 nscap
= kzalloc(size
, GFP_ATOMIC
);
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
);
443 /* use allocated v3 buffer */
446 nscap
->rootid
= cpu_to_le32(mappedroot
);
452 if (!rootid_owns_currentns(kroot
)) {
457 /* This comes from a parent namespace. Return as a v2 capability */
458 size
= sizeof(struct vfs_cap_data
);
461 /* v3 -> v2 conversion */
462 cap
= kzalloc(size
, GFP_ATOMIC
);
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
);
474 /* use unconverted v2 */
485 * rootid_from_xattr - translate root uid of vfs caps
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
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.
498 static kuid_t
rootid_from_xattr(const void *value
, size_t size
,
499 struct user_namespace
*task_ns
,
500 struct user_namespace
*mnt_userns
)
502 const struct vfs_ns_cap_data
*nscap
= value
;
506 if (size
== XATTR_CAPS_SZ_3
)
507 rootid
= le32_to_cpu(nscap
->rootid
);
509 rootkid
= make_kuid(task_ns
, rootid
);
510 return kuid_from_mnt(mnt_userns
, rootkid
);
513 static bool validheader(size_t size
, const struct vfs_cap_data
*cap
)
515 return is_v2header(size
, cap
) || is_v3header(size
, cap
);
519 * cap_convert_nscap - check vfs caps
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
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.
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.
535 * Return: On success, return the new size; on error, return < 0.
537 int cap_convert_nscap(struct user_namespace
*mnt_userns
, struct dentry
*dentry
,
538 const void **ivalue
, size_t size
)
540 struct vfs_ns_cap_data
*nscap
;
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
;
552 if (!validheader(size
, cap
))
554 if (!capable_wrt_inode_uidgid(mnt_userns
, inode
, CAP_SETFCAP
))
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 */
561 rootid
= rootid_from_xattr(*ivalue
, size
, task_ns
, mnt_userns
);
562 if (!uid_valid(rootid
))
565 nsrootid
= from_kuid(fs_ns
, rootid
);
569 newsize
= sizeof(struct vfs_ns_cap_data
);
570 nscap
= kmalloc(newsize
, GFP_ATOMIC
);
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
);
586 * Calculate the new process capability sets from the capability sets attached
589 static inline int bprm_caps_from_vfs_caps(struct cpu_vfs_cap_data
*caps
,
590 struct linux_binprm
*bprm
,
594 struct cred
*new = bprm
->cred
;
598 if (caps
->magic_etc
& VFS_CAP_FLAGS_EFFECTIVE
)
601 if (caps
->magic_etc
& VFS_CAP_REVISION_MASK
)
604 CAP_FOR_EACH_U32(i
) {
605 __u32 permitted
= caps
->permitted
.cap
[i
];
606 __u32 inheritable
= caps
->inheritable
.cap
[i
];
609 * pP' = (X & fP) | (pI & fI)
610 * The addition of pA' is handled later.
612 new->cap_permitted
.cap
[i
] =
613 (new->cap_bset
.cap
[i
] & permitted
) |
614 (new->cap_inheritable
.cap
[i
] & inheritable
);
616 if (permitted
& ~new->cap_permitted
.cap
[i
])
617 /* insufficient to execute correctly */
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.
626 return *effective
? ret
: 0;
630 * get_vfs_caps_from_disk - retrieve vfs caps from disk
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
636 * Extract the on-exec-apply capability sets for an executable file.
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.
644 int get_vfs_caps_from_disk(struct user_namespace
*mnt_userns
,
645 const struct dentry
*dentry
,
646 struct cpu_vfs_cap_data
*cpu_caps
)
648 struct inode
*inode
= d_backing_inode(dentry
);
652 struct vfs_ns_cap_data data
, *nscaps
= &data
;
653 struct vfs_cap_data
*caps
= (struct vfs_cap_data
*) &data
;
655 struct user_namespace
*fs_ns
;
657 memset(cpu_caps
, 0, sizeof(struct cpu_vfs_cap_data
));
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 */
672 if (size
< sizeof(magic_etc
))
675 cpu_caps
->magic_etc
= magic_etc
= le32_to_cpu(caps
->magic_etc
);
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
)
682 tocopy
= VFS_CAP_U32_1
;
684 case VFS_CAP_REVISION_2
:
685 if (size
!= XATTR_CAPS_SZ_2
)
687 tocopy
= VFS_CAP_U32_2
;
689 case VFS_CAP_REVISION_3
:
690 if (size
!= XATTR_CAPS_SZ_3
)
692 tocopy
= VFS_CAP_U32_3
;
693 rootkuid
= make_kuid(fs_ns
, le32_to_cpu(nscaps
->rootid
));
699 /* Limit the caps to the mounter of the filesystem
700 * or the more limited uid specified in the xattr.
702 rootkuid
= kuid_into_mnt(mnt_userns
, rootkuid
);
703 if (!rootid_owns_currentns(rootkuid
))
706 CAP_FOR_EACH_U32(i
) {
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
);
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
;
716 cpu_caps
->rootid
= rootkuid
;
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().
726 static int get_file_caps(struct linux_binprm
*bprm
, struct file
*file
,
727 bool *effective
, bool *has_fcap
)
730 struct cpu_vfs_cap_data vcaps
;
732 cap_clear(bprm
->cred
->cap_permitted
);
734 if (!file_caps_enabled
)
737 if (!mnt_may_suid(file
->f_path
.mnt
))
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
745 if (!current_in_userns(file
->f_path
.mnt
->mnt_sb
->s_user_ns
))
748 rc
= get_vfs_caps_from_disk(file_mnt_user_ns(file
),
749 file
->f_path
.dentry
, &vcaps
);
752 printk(KERN_NOTICE
"Invalid argument reading file caps for %s\n",
754 else if (rc
== -ENODATA
)
759 rc
= bprm_caps_from_vfs_caps(&vcaps
, bprm
, effective
, has_fcap
);
763 cap_clear(bprm
->cred
->cap_permitted
);
768 static inline bool root_privileged(void) { return !issecure(SECURE_NOROOT
); }
770 static inline bool __is_real(kuid_t uid
, struct cred
*cred
)
771 { return uid_eq(cred
->uid
, uid
); }
773 static inline bool __is_eff(kuid_t uid
, struct cred
*cred
)
774 { return uid_eq(cred
->euid
, uid
); }
776 static inline bool __is_suid(kuid_t uid
, struct cred
*cred
)
777 { return !__is_real(uid
, cred
) && __is_eff(uid
, cred
); }
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
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.
791 static void handle_privileged_root(struct linux_binprm
*bprm
, bool has_fcap
,
792 bool *effective
, kuid_t root_uid
)
794 const struct cred
*old
= current_cred();
795 struct cred
*new = bprm
->cred
;
797 if (!root_privileged())
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.
804 if (has_fcap
&& __is_suid(root_uid
, new)) {
805 warn_setuid_and_fcaps_mixed(bprm
->filename
);
809 * To support inheritance of root-permissions and suid-root
810 * executables under compatibility mode, we override the
811 * capability sets for the file.
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
);
819 * If only the real uid is 0, we do not set the effective bit.
821 if (__is_eff(root_uid
, new))
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)
832 static inline bool __is_setuid(struct cred
*new, const struct cred
*old
)
833 { return !uid_eq(new->euid
, old
->uid
); }
835 static inline bool __is_setgid(struct cred
*new, const struct cred
*old
)
836 { return !gid_eq(new->egid
, old
->gid
); }
839 * 1) Audit candidate if current->cap_effective is set
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.
847 * Number 1 above might fail if you don't have a full bset, but I think
848 * that is interesting information to audit.
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
855 static inline bool nonroot_raised_pE(struct cred
*new, const struct cred
*old
,
856 kuid_t root
, bool has_fcap
)
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
) &&
869 __cap_gained(permitted
, new, old
)) ||
870 __cap_gained(ambient
, new, old
))))
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
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.
886 * Return: 0 if successful, -ve on error.
888 int cap_bprm_creds_from_file(struct linux_binprm
*bprm
, struct file
*file
)
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
;
897 if (WARN_ON(!cap_ambient_invariant_ok(old
)))
900 ret
= get_file_caps(bprm
, file
, &effective
, &has_fcap
);
904 root_uid
= make_kuid(new->user_ns
, 0);
906 handle_privileged_root(bprm
, has_fcap
, &effective
, root_uid
);
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
;
912 /* Don't let someone trace a set[ug]id/setpcap binary with the revised
913 * credentials unless they have the appropriate permit.
915 * In addition, if NO_NEW_PRIVS, then ensure we get no new privs.
917 is_setid
= __is_setuid(new, old
) || __is_setgid(new, old
);
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
;
928 new->cap_permitted
= cap_intersect(new->cap_permitted
,
932 new->suid
= new->fsuid
= new->euid
;
933 new->sgid
= new->fsgid
= new->egid
;
935 /* File caps or setid cancels ambient. */
936 if (has_fcap
|| is_setid
)
937 cap_clear(new->cap_ambient
);
940 * Now that we've computed pA', update pP' to give:
941 * pP' = (X & fP) | (pI & fI) | pA'
943 new->cap_permitted
= cap_combine(new->cap_permitted
, new->cap_ambient
);
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'.
950 new->cap_effective
= new->cap_permitted
;
952 new->cap_effective
= new->cap_ambient
;
954 if (WARN_ON(!cap_ambient_invariant_ok(new)))
957 if (nonroot_raised_pE(new, old
, root_uid
, has_fcap
)) {
958 ret
= audit_log_bprm_fcaps(bprm
, new, old
);
963 new->securebits
&= ~issecure_mask(SECURE_KEEP_CAPS
);
965 if (WARN_ON(!cap_ambient_invariant_ok(new)))
968 /* Check for privilege-elevated exec. */
970 (!__is_real(root_uid
, new) &&
972 __cap_grew(permitted
, ambient
, new))))
973 bprm
->secureexec
= 1;
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
986 * Determine whether an xattr may be altered or set on an inode, returning 0 if
987 * permission is granted, -ve if denied.
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.
992 int cap_inode_setxattr(struct dentry
*dentry
, const char *name
,
993 const void *value
, size_t size
, int flags
)
995 struct user_namespace
*user_ns
= dentry
->d_sb
->s_user_ns
;
997 /* Ignore non-security xattrs */
998 if (strncmp(name
, XATTR_SECURITY_PREFIX
,
999 XATTR_SECURITY_PREFIX_LEN
) != 0)
1003 * For XATTR_NAME_CAPS the check will be done in
1004 * cap_convert_nscap(), called by setxattr()
1006 if (strcmp(name
, XATTR_NAME_CAPS
) == 0)
1009 if (!ns_capable(user_ns
, CAP_SYS_ADMIN
))
1015 * cap_inode_removexattr - Determine whether an xattr may be removed
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
1021 * Determine whether an xattr may be removed from an inode, returning 0 if
1022 * permission is granted, -ve if denied.
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.
1030 * This is used to make sure security xattrs don't get removed by those who
1031 * aren't privileged to remove them.
1033 int cap_inode_removexattr(struct user_namespace
*mnt_userns
,
1034 struct dentry
*dentry
, const char *name
)
1036 struct user_namespace
*user_ns
= dentry
->d_sb
->s_user_ns
;
1038 /* Ignore non-security xattrs */
1039 if (strncmp(name
, XATTR_SECURITY_PREFIX
,
1040 XATTR_SECURITY_PREFIX_LEN
) != 0)
1043 if (strcmp(name
, XATTR_NAME_CAPS
) == 0) {
1044 /* security.capability gets namespaced */
1045 struct inode
*inode
= d_backing_inode(dentry
);
1048 if (!capable_wrt_inode_uidgid(mnt_userns
, inode
, CAP_SETFCAP
))
1053 if (!ns_capable(user_ns
, CAP_SYS_ADMIN
))
1059 * cap_emulate_setxuid() fixes the effective / permitted capabilities of
1060 * a process after a call to setuid, setreuid, or setresuid.
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
1066 * 2) When set*uiding _from_ euid == 0 _to_ euid != 0, the effective
1067 * capabilities of the process are cleared.
1069 * 3) When set*uiding _from_ euid != 0 _to_ euid == 0, the effective
1070 * capabilities are set to the permitted capabilities.
1072 * fsuid is handled elsewhere. fsuid == 0 and {r,e,s}uid!= 0 should
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
1085 * Thanks to Olaf Kirch and Peter Benie for spotting this.
1087 static inline void cap_emulate_setxuid(struct cred
*new, const struct cred
*old
)
1089 kuid_t root_uid
= make_kuid(old
->user_ns
, 0);
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
);
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.
1107 cap_clear(new->cap_ambient
);
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
;
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
1121 * Fix up the results of setuid() call before the credential changes are
1124 * Return: 0 to grant the changes, -ve to deny them.
1126 int cap_task_fix_setuid(struct cred
*new, const struct cred
*old
, int flags
)
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
);
1139 /* juggle the capabilties to follow FSUID changes, unless
1140 * otherwise suppressed
1142 * FIXME - is fsuser used for all CAP_FS_MASK capabilities?
1143 * if not, we might be a bit too harsh here.
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
);
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
);
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.
1175 static int cap_safe_nice(struct task_struct
*p
)
1177 int is_subset
, ret
= 0;
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
))
1190 * cap_task_setscheduler - Detemine if scheduler policy change is permitted
1191 * @p: The task to affect
1193 * Detemine if the requested scheduler policy change is permitted for the
1196 * Return: 0 if permission is granted, -ve if denied.
1198 int cap_task_setscheduler(struct task_struct
*p
)
1200 return cap_safe_nice(p
);
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
1208 * Detemine if the requested I/O priority change is permitted for the specified
1211 * Return: 0 if permission is granted, -ve if denied.
1213 int cap_task_setioprio(struct task_struct
*p
, int ioprio
)
1215 return cap_safe_nice(p
);
1219 * cap_task_setnice - Detemine if task priority change is permitted
1220 * @p: The task to affect
1221 * @nice: The nice value to set
1223 * Detemine if the requested task priority change is permitted for the
1226 * Return: 0 if permission is granted, -ve if denied.
1228 int cap_task_setnice(struct task_struct
*p
, int nice
)
1230 return cap_safe_nice(p
);
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.
1237 static int cap_prctl_drop(unsigned long cap
)
1241 if (!ns_capable(current_user_ns(), CAP_SETPCAP
))
1243 if (!cap_valid(cap
))
1246 new = prepare_creds();
1249 cap_lower(new->cap_bset
, cap
);
1250 return commit_creds(new);
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
1261 * Allow process control functions (sys_prctl()) to alter capabilities; may
1262 * also deny access to other functions not otherwise implemented here.
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.
1268 int cap_task_prctl(int option
, unsigned long arg2
, unsigned long arg3
,
1269 unsigned long arg4
, unsigned long arg5
)
1271 const struct cred
*old
= current_cred();
1275 case PR_CAPBSET_READ
:
1276 if (!cap_valid(arg2
))
1278 return !!cap_raised(old
->cap_bset
, arg2
);
1280 case PR_CAPBSET_DROP
:
1281 return cap_prctl_drop(arg2
);
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.
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)
1298 * will ensure that the current process and all of its
1299 * children will be locked into a pure
1300 * capability-based-privilege environment.
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
,
1310 CAP_OPT_NONE
) != 0) /*[4]*/
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")
1319 /* cannot change a locked bit */
1322 new = prepare_creds();
1325 new->securebits
= arg2
;
1326 return commit_creds(new);
1328 case PR_GET_SECUREBITS
:
1329 return old
->securebits
;
1331 case PR_GET_KEEPCAPS
:
1332 return !!issecure(SECURE_KEEP_CAPS
);
1334 case PR_SET_KEEPCAPS
:
1335 if (arg2
> 1) /* Note, we rely on arg2 being unsigned here */
1337 if (issecure(SECURE_KEEP_CAPS_LOCKED
))
1340 new = prepare_creds();
1344 new->securebits
|= issecure_mask(SECURE_KEEP_CAPS
);
1346 new->securebits
&= ~issecure_mask(SECURE_KEEP_CAPS
);
1347 return commit_creds(new);
1349 case PR_CAP_AMBIENT
:
1350 if (arg2
== PR_CAP_AMBIENT_CLEAR_ALL
) {
1351 if (arg3
| arg4
| arg5
)
1354 new = prepare_creds();
1357 cap_clear(new->cap_ambient
);
1358 return commit_creds(new);
1361 if (((!cap_valid(arg3
)) | arg4
| arg5
))
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
) {
1370 if (arg2
== PR_CAP_AMBIENT_RAISE
&&
1371 (!cap_raised(current_cred()->cap_permitted
, arg3
) ||
1372 !cap_raised(current_cred()->cap_inheritable
,
1374 issecure(SECURE_NO_CAP_AMBIENT_RAISE
)))
1377 new = prepare_creds();
1380 if (arg2
== PR_CAP_AMBIENT_RAISE
)
1381 cap_raise(new->cap_ambient
, arg3
);
1383 cap_lower(new->cap_ambient
, arg3
);
1384 return commit_creds(new);
1388 /* No functionality available - continue with default */
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
1398 * Determine whether the allocation of a new virtual mapping by the current
1399 * task is permitted.
1401 * Return: 1 if permission is granted, 0 if not.
1403 int cap_vm_enough_memory(struct mm_struct
*mm
, long pages
)
1405 int cap_sys_admin
= 0;
1407 if (cap_capable(current_cred(), &init_user_ns
,
1408 CAP_SYS_ADMIN
, CAP_OPT_NOAUDIT
) == 0)
1411 return cap_sys_admin
;
1415 * cap_mmap_addr - check if able to map given addr
1416 * @addr: address attempting to be mapped
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.
1422 * Return: 0 if this mapping should be allowed or -EPERM if not.
1424 int cap_mmap_addr(unsigned long addr
)
1428 if (addr
< dac_mmap_min_addr
) {
1429 ret
= cap_capable(current_cred(), &init_user_ns
, CAP_SYS_RAWIO
,
1431 /* set PF_SUPERPRIV if it turns out we allow the low mmap */
1433 current
->flags
|= PF_SUPERPRIV
;
1438 int cap_mmap_file(struct file
*file
, unsigned long reqprot
,
1439 unsigned long prot
, unsigned long flags
)
1444 #ifdef CONFIG_SECURITY
1446 static 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
),
1467 static int __init
capability_init(void)
1469 security_add_hooks(capability_hooks
, ARRAY_SIZE(capability_hooks
),
1474 DEFINE_LSM(capability
) = {
1475 .name
= "capability",
1476 .order
= LSM_ORDER_FIRST
,
1477 .init
= capability_init
,
1480 #endif /* CONFIG_SECURITY */