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, &init_user_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 == &init_user_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,
566 if (!uid_valid(rootid))
569 nsrootid = from_kuid(fs_ns, rootid);
573 newsize = sizeof(struct vfs_ns_cap_data);
574 nscap = kmalloc(newsize, GFP_ATOMIC);
577 nscap->rootid = cpu_to_le32(nsrootid);
578 nsmagic = VFS_CAP_REVISION_3;
579 magic = le32_to_cpu(cap->magic_etc);
580 if (magic & VFS_CAP_FLAGS_EFFECTIVE)
581 nsmagic |= VFS_CAP_FLAGS_EFFECTIVE;
582 nscap->magic_etc = cpu_to_le32(nsmagic);
583 memcpy(&nscap->data, &cap->data, sizeof(__le32) * 2 * VFS_CAP_U32);
590 * Calculate the new process capability sets from the capability sets attached
593 static inline int bprm_caps_from_vfs_caps(struct cpu_vfs_cap_data *caps,
594 struct linux_binprm *bprm,
598 struct cred *new = bprm->cred;
602 if (caps->magic_etc & VFS_CAP_FLAGS_EFFECTIVE)
605 if (caps->magic_etc & VFS_CAP_REVISION_MASK)
608 CAP_FOR_EACH_U32(i) {
609 __u32 permitted = caps->permitted.cap[i];
610 __u32 inheritable = caps->inheritable.cap[i];
613 * pP' = (X & fP) | (pI & fI)
614 * The addition of pA' is handled later.
616 new->cap_permitted.cap[i] =
617 (new->cap_bset.cap[i] & permitted) |
618 (new->cap_inheritable.cap[i] & inheritable);
620 if (permitted & ~new->cap_permitted.cap[i])
621 /* insufficient to execute correctly */
626 * For legacy apps, with no internal support for recognizing they
627 * do not have enough capabilities, we return an error if they are
628 * missing some "forced" (aka file-permitted) capabilities.
630 return *effective ? ret : 0;
634 * get_vfs_caps_from_disk - retrieve vfs caps from disk
636 * @mnt_userns: user namespace of the mount the inode was found from
637 * @dentry: dentry from which @inode is retrieved
638 * @cpu_caps: vfs capabilities
640 * Extract the on-exec-apply capability sets for an executable file.
642 * If the inode has been found through an idmapped mount the user namespace of
643 * the vfsmount must be passed through @mnt_userns. This function will then
644 * take care to map the inode according to @mnt_userns before checking
645 * permissions. On non-idmapped mounts or if permission checking is to be
646 * performed on the raw inode simply passs init_user_ns.
648 int get_vfs_caps_from_disk(struct user_namespace *mnt_userns,
649 const struct dentry *dentry,
650 struct cpu_vfs_cap_data *cpu_caps)
652 struct inode *inode = d_backing_inode(dentry);
656 struct vfs_ns_cap_data data, *nscaps = &data;
657 struct vfs_cap_data *caps = (struct vfs_cap_data *) &data;
659 struct user_namespace *fs_ns;
661 memset(cpu_caps, 0, sizeof(struct cpu_vfs_cap_data));
666 fs_ns = inode->i_sb->s_user_ns;
667 size = __vfs_getxattr((struct dentry *)dentry, inode,
668 XATTR_NAME_CAPS, &data, XATTR_CAPS_SZ);
669 if (size == -ENODATA || size == -EOPNOTSUPP)
670 /* no data, that's ok */
676 if (size < sizeof(magic_etc))
679 cpu_caps->magic_etc = magic_etc = le32_to_cpu(caps->magic_etc);
681 rootkuid = make_kuid(fs_ns, 0);
682 switch (magic_etc & VFS_CAP_REVISION_MASK) {
683 case VFS_CAP_REVISION_1:
684 if (size != XATTR_CAPS_SZ_1)
686 tocopy = VFS_CAP_U32_1;
688 case VFS_CAP_REVISION_2:
689 if (size != XATTR_CAPS_SZ_2)
691 tocopy = VFS_CAP_U32_2;
693 case VFS_CAP_REVISION_3:
694 if (size != XATTR_CAPS_SZ_3)
696 tocopy = VFS_CAP_U32_3;
697 rootkuid = make_kuid(fs_ns, le32_to_cpu(nscaps->rootid));
703 /* Limit the caps to the mounter of the filesystem
704 * or the more limited uid specified in the xattr.
706 rootkuid = mapped_kuid_fs(mnt_userns, &init_user_ns, rootkuid);
707 if (!rootid_owns_currentns(rootkuid))
710 CAP_FOR_EACH_U32(i) {
713 cpu_caps->permitted.cap[i] = le32_to_cpu(caps->data[i].permitted);
714 cpu_caps->inheritable.cap[i] = le32_to_cpu(caps->data[i].inheritable);
717 cpu_caps->permitted.cap[CAP_LAST_U32] &= CAP_LAST_U32_VALID_MASK;
718 cpu_caps->inheritable.cap[CAP_LAST_U32] &= CAP_LAST_U32_VALID_MASK;
720 cpu_caps->rootid = rootkuid;
726 * Attempt to get the on-exec apply capability sets for an executable file from
727 * its xattrs and, if present, apply them to the proposed credentials being
728 * constructed by execve().
730 static int get_file_caps(struct linux_binprm *bprm, struct file *file,
731 bool *effective, bool *has_fcap)
734 struct cpu_vfs_cap_data vcaps;
736 cap_clear(bprm->cred->cap_permitted);
738 if (!file_caps_enabled)
741 if (!mnt_may_suid(file->f_path.mnt))
745 * This check is redundant with mnt_may_suid() but is kept to make
746 * explicit that capability bits are limited to s_user_ns and its
749 if (!current_in_userns(file->f_path.mnt->mnt_sb->s_user_ns))
752 rc = get_vfs_caps_from_disk(file_mnt_user_ns(file),
753 file->f_path.dentry, &vcaps);
756 printk(KERN_NOTICE "Invalid argument reading file caps for %s\n",
758 else if (rc == -ENODATA)
763 rc = bprm_caps_from_vfs_caps(&vcaps, bprm, effective, has_fcap);
767 cap_clear(bprm->cred->cap_permitted);
772 static inline bool root_privileged(void) { return !issecure(SECURE_NOROOT); }
774 static inline bool __is_real(kuid_t uid, struct cred *cred)
775 { return uid_eq(cred->uid, uid); }
777 static inline bool __is_eff(kuid_t uid, struct cred *cred)
778 { return uid_eq(cred->euid, uid); }
780 static inline bool __is_suid(kuid_t uid, struct cred *cred)
781 { return !__is_real(uid, cred) && __is_eff(uid, cred); }
784 * handle_privileged_root - Handle case of privileged root
785 * @bprm: The execution parameters, including the proposed creds
786 * @has_fcap: Are any file capabilities set?
787 * @effective: Do we have effective root privilege?
788 * @root_uid: This namespace' root UID WRT initial USER namespace
790 * Handle the case where root is privileged and hasn't been neutered by
791 * SECURE_NOROOT. If file capabilities are set, they won't be combined with
792 * set UID root and nothing is changed. If we are root, cap_permitted is
793 * updated. If we have become set UID root, the effective bit is set.
795 static void handle_privileged_root(struct linux_binprm *bprm, bool has_fcap,
796 bool *effective, kuid_t root_uid)
798 const struct cred *old = current_cred();
799 struct cred *new = bprm->cred;
801 if (!root_privileged())
804 * If the legacy file capability is set, then don't set privs
805 * for a setuid root binary run by a non-root user. Do set it
806 * for a root user just to cause least surprise to an admin.
808 if (has_fcap && __is_suid(root_uid, new)) {
809 warn_setuid_and_fcaps_mixed(bprm->filename);
813 * To support inheritance of root-permissions and suid-root
814 * executables under compatibility mode, we override the
815 * capability sets for the file.
817 if (__is_eff(root_uid, new) || __is_real(root_uid, new)) {
818 /* pP' = (cap_bset & ~0) | (pI & ~0) */
819 new->cap_permitted = cap_combine(old->cap_bset,
820 old->cap_inheritable);
823 * If only the real uid is 0, we do not set the effective bit.
825 if (__is_eff(root_uid, new))
829 #define __cap_gained(field, target, source) \
830 !cap_issubset(target->cap_##field, source->cap_##field)
831 #define __cap_grew(target, source, cred) \
832 !cap_issubset(cred->cap_##target, cred->cap_##source)
833 #define __cap_full(field, cred) \
834 cap_issubset(CAP_FULL_SET, cred->cap_##field)
836 static inline bool __is_setuid(struct cred *new, const struct cred *old)
837 { return !uid_eq(new->euid, old->uid); }
839 static inline bool __is_setgid(struct cred *new, const struct cred *old)
840 { return !gid_eq(new->egid, old->gid); }
843 * 1) Audit candidate if current->cap_effective is set
845 * We do not bother to audit if 3 things are true:
846 * 1) cap_effective has all caps
847 * 2) we became root *OR* are were already root
848 * 3) root is supposed to have all caps (SECURE_NOROOT)
849 * Since this is just a normal root execing a process.
851 * Number 1 above might fail if you don't have a full bset, but I think
852 * that is interesting information to audit.
854 * A number of other conditions require logging:
855 * 2) something prevented setuid root getting all caps
856 * 3) non-setuid root gets fcaps
857 * 4) non-setuid root gets ambient
859 static inline bool nonroot_raised_pE(struct cred *new, const struct cred *old,
860 kuid_t root, bool has_fcap)
864 if ((__cap_grew(effective, ambient, new) &&
865 !(__cap_full(effective, new) &&
866 (__is_eff(root, new) || __is_real(root, new)) &&
867 root_privileged())) ||
868 (root_privileged() &&
869 __is_suid(root, new) &&
870 !__cap_full(effective, new)) ||
871 (!__is_setuid(new, old) &&
873 __cap_gained(permitted, new, old)) ||
874 __cap_gained(ambient, new, old))))
882 * cap_bprm_creds_from_file - Set up the proposed credentials for execve().
883 * @bprm: The execution parameters, including the proposed creds
884 * @file: The file to pull the credentials from
886 * Set up the proposed credentials for a new execution context being
887 * constructed by execve(). The proposed creds in @bprm->cred is altered,
888 * which won't take effect immediately.
890 * Return: 0 if successful, -ve on error.
892 int cap_bprm_creds_from_file(struct linux_binprm *bprm, struct file *file)
894 /* Process setpcap binaries and capabilities for uid 0 */
895 const struct cred *old = current_cred();
896 struct cred *new = bprm->cred;
897 bool effective = false, has_fcap = false, is_setid;
901 if (WARN_ON(!cap_ambient_invariant_ok(old)))
904 ret = get_file_caps(bprm, file, &effective, &has_fcap);
908 root_uid = make_kuid(new->user_ns, 0);
910 handle_privileged_root(bprm, has_fcap, &effective, root_uid);
912 /* if we have fs caps, clear dangerous personality flags */
913 if (__cap_gained(permitted, new, old))
914 bprm->per_clear |= PER_CLEAR_ON_SETID;
916 /* Don't let someone trace a set[ug]id/setpcap binary with the revised
917 * credentials unless they have the appropriate permit.
919 * In addition, if NO_NEW_PRIVS, then ensure we get no new privs.
921 is_setid = __is_setuid(new, old) || __is_setgid(new, old);
923 if ((is_setid || __cap_gained(permitted, new, old)) &&
924 ((bprm->unsafe & ~LSM_UNSAFE_PTRACE) ||
925 !ptracer_capable(current, new->user_ns))) {
926 /* downgrade; they get no more than they had, and maybe less */
927 if (!ns_capable(new->user_ns, CAP_SETUID) ||
928 (bprm->unsafe & LSM_UNSAFE_NO_NEW_PRIVS)) {
929 new->euid = new->uid;
930 new->egid = new->gid;
932 new->cap_permitted = cap_intersect(new->cap_permitted,
936 new->suid = new->fsuid = new->euid;
937 new->sgid = new->fsgid = new->egid;
939 /* File caps or setid cancels ambient. */
940 if (has_fcap || is_setid)
941 cap_clear(new->cap_ambient);
944 * Now that we've computed pA', update pP' to give:
945 * pP' = (X & fP) | (pI & fI) | pA'
947 new->cap_permitted = cap_combine(new->cap_permitted, new->cap_ambient);
950 * Set pE' = (fE ? pP' : pA'). Because pA' is zero if fE is set,
951 * this is the same as pE' = (fE ? pP' : 0) | pA'.
954 new->cap_effective = new->cap_permitted;
956 new->cap_effective = new->cap_ambient;
958 if (WARN_ON(!cap_ambient_invariant_ok(new)))
961 if (nonroot_raised_pE(new, old, root_uid, has_fcap)) {
962 ret = audit_log_bprm_fcaps(bprm, new, old);
967 new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS);
969 if (WARN_ON(!cap_ambient_invariant_ok(new)))
972 /* Check for privilege-elevated exec. */
974 (!__is_real(root_uid, new) &&
976 __cap_grew(permitted, ambient, new))))
977 bprm->secureexec = 1;
983 * cap_inode_setxattr - Determine whether an xattr may be altered
984 * @dentry: The inode/dentry being altered
985 * @name: The name of the xattr to be changed
986 * @value: The value that the xattr will be changed to
987 * @size: The size of value
988 * @flags: The replacement flag
990 * Determine whether an xattr may be altered or set on an inode, returning 0 if
991 * permission is granted, -ve if denied.
993 * This is used to make sure security xattrs don't get updated or set by those
994 * who aren't privileged to do so.
996 int cap_inode_setxattr(struct dentry *dentry, const char *name,
997 const void *value, size_t size, int flags)
999 struct user_namespace *user_ns = dentry->d_sb->s_user_ns;
1001 /* Ignore non-security xattrs */
1002 if (strncmp(name, XATTR_SECURITY_PREFIX,
1003 XATTR_SECURITY_PREFIX_LEN) != 0)
1007 * For XATTR_NAME_CAPS the check will be done in
1008 * cap_convert_nscap(), called by setxattr()
1010 if (strcmp(name, XATTR_NAME_CAPS) == 0)
1013 if (!ns_capable(user_ns, CAP_SYS_ADMIN))
1019 * cap_inode_removexattr - Determine whether an xattr may be removed
1021 * @mnt_userns: User namespace of the mount the inode was found from
1022 * @dentry: The inode/dentry being altered
1023 * @name: The name of the xattr to be changed
1025 * Determine whether an xattr may be removed from an inode, returning 0 if
1026 * permission is granted, -ve if denied.
1028 * If the inode has been found through an idmapped mount the user namespace of
1029 * the vfsmount must be passed through @mnt_userns. This function will then
1030 * take care to map the inode according to @mnt_userns before checking
1031 * permissions. On non-idmapped mounts or if permission checking is to be
1032 * performed on the raw inode simply passs init_user_ns.
1034 * This is used to make sure security xattrs don't get removed by those who
1035 * aren't privileged to remove them.
1037 int cap_inode_removexattr(struct user_namespace *mnt_userns,
1038 struct dentry *dentry, const char *name)
1040 struct user_namespace *user_ns = dentry->d_sb->s_user_ns;
1042 /* Ignore non-security xattrs */
1043 if (strncmp(name, XATTR_SECURITY_PREFIX,
1044 XATTR_SECURITY_PREFIX_LEN) != 0)
1047 if (strcmp(name, XATTR_NAME_CAPS) == 0) {
1048 /* security.capability gets namespaced */
1049 struct inode *inode = d_backing_inode(dentry);
1052 if (!capable_wrt_inode_uidgid(mnt_userns, inode, CAP_SETFCAP))
1057 if (!ns_capable(user_ns, CAP_SYS_ADMIN))
1063 * cap_emulate_setxuid() fixes the effective / permitted capabilities of
1064 * a process after a call to setuid, setreuid, or setresuid.
1066 * 1) When set*uiding _from_ one of {r,e,s}uid == 0 _to_ all of
1067 * {r,e,s}uid != 0, the permitted and effective capabilities are
1070 * 2) When set*uiding _from_ euid == 0 _to_ euid != 0, the effective
1071 * capabilities of the process are cleared.
1073 * 3) When set*uiding _from_ euid != 0 _to_ euid == 0, the effective
1074 * capabilities are set to the permitted capabilities.
1076 * fsuid is handled elsewhere. fsuid == 0 and {r,e,s}uid!= 0 should
1081 * cevans - New behaviour, Oct '99
1082 * A process may, via prctl(), elect to keep its capabilities when it
1083 * calls setuid() and switches away from uid==0. Both permitted and
1084 * effective sets will be retained.
1085 * Without this change, it was impossible for a daemon to drop only some
1086 * of its privilege. The call to setuid(!=0) would drop all privileges!
1087 * Keeping uid 0 is not an option because uid 0 owns too many vital
1089 * Thanks to Olaf Kirch and Peter Benie for spotting this.
1091 static inline void cap_emulate_setxuid(struct cred *new, const struct cred *old)
1093 kuid_t root_uid = make_kuid(old->user_ns, 0);
1095 if ((uid_eq(old->uid, root_uid) ||
1096 uid_eq(old->euid, root_uid) ||
1097 uid_eq(old->suid, root_uid)) &&
1098 (!uid_eq(new->uid, root_uid) &&
1099 !uid_eq(new->euid, root_uid) &&
1100 !uid_eq(new->suid, root_uid))) {
1101 if (!issecure(SECURE_KEEP_CAPS)) {
1102 cap_clear(new->cap_permitted);
1103 cap_clear(new->cap_effective);
1107 * Pre-ambient programs expect setresuid to nonroot followed
1108 * by exec to drop capabilities. We should make sure that
1109 * this remains the case.
1111 cap_clear(new->cap_ambient);
1113 if (uid_eq(old->euid, root_uid) && !uid_eq(new->euid, root_uid))
1114 cap_clear(new->cap_effective);
1115 if (!uid_eq(old->euid, root_uid) && uid_eq(new->euid, root_uid))
1116 new->cap_effective = new->cap_permitted;
1120 * cap_task_fix_setuid - Fix up the results of setuid() call
1121 * @new: The proposed credentials
1122 * @old: The current task's current credentials
1123 * @flags: Indications of what has changed
1125 * Fix up the results of setuid() call before the credential changes are
1128 * Return: 0 to grant the changes, -ve to deny them.
1130 int cap_task_fix_setuid(struct cred *new, const struct cred *old, int flags)
1136 /* juggle the capabilities to follow [RES]UID changes unless
1137 * otherwise suppressed */
1138 if (!issecure(SECURE_NO_SETUID_FIXUP))
1139 cap_emulate_setxuid(new, old);
1143 /* juggle the capabilties to follow FSUID changes, unless
1144 * otherwise suppressed
1146 * FIXME - is fsuser used for all CAP_FS_MASK capabilities?
1147 * if not, we might be a bit too harsh here.
1149 if (!issecure(SECURE_NO_SETUID_FIXUP)) {
1150 kuid_t root_uid = make_kuid(old->user_ns, 0);
1151 if (uid_eq(old->fsuid, root_uid) && !uid_eq(new->fsuid, root_uid))
1152 new->cap_effective =
1153 cap_drop_fs_set(new->cap_effective);
1155 if (!uid_eq(old->fsuid, root_uid) && uid_eq(new->fsuid, root_uid))
1156 new->cap_effective =
1157 cap_raise_fs_set(new->cap_effective,
1158 new->cap_permitted);
1170 * Rationale: code calling task_setscheduler, task_setioprio, and
1171 * task_setnice, assumes that
1172 * . if capable(cap_sys_nice), then those actions should be allowed
1173 * . if not capable(cap_sys_nice), but acting on your own processes,
1174 * then those actions should be allowed
1175 * This is insufficient now since you can call code without suid, but
1176 * yet with increased caps.
1177 * So we check for increased caps on the target process.
1179 static int cap_safe_nice(struct task_struct *p)
1181 int is_subset, ret = 0;
1184 is_subset = cap_issubset(__task_cred(p)->cap_permitted,
1185 current_cred()->cap_permitted);
1186 if (!is_subset && !ns_capable(__task_cred(p)->user_ns, CAP_SYS_NICE))
1194 * cap_task_setscheduler - Detemine if scheduler policy change is permitted
1195 * @p: The task to affect
1197 * Detemine if the requested scheduler policy change is permitted for the
1200 * Return: 0 if permission is granted, -ve if denied.
1202 int cap_task_setscheduler(struct task_struct *p)
1204 return cap_safe_nice(p);
1208 * cap_task_setioprio - Detemine if I/O priority change is permitted
1209 * @p: The task to affect
1210 * @ioprio: The I/O priority to set
1212 * Detemine if the requested I/O priority change is permitted for the specified
1215 * Return: 0 if permission is granted, -ve if denied.
1217 int cap_task_setioprio(struct task_struct *p, int ioprio)
1219 return cap_safe_nice(p);
1223 * cap_task_setnice - Detemine if task priority change is permitted
1224 * @p: The task to affect
1225 * @nice: The nice value to set
1227 * Detemine if the requested task priority change is permitted for the
1230 * Return: 0 if permission is granted, -ve if denied.
1232 int cap_task_setnice(struct task_struct *p, int nice)
1234 return cap_safe_nice(p);
1238 * Implement PR_CAPBSET_DROP. Attempt to remove the specified capability from
1239 * the current task's bounding set. Returns 0 on success, -ve on error.
1241 static int cap_prctl_drop(unsigned long cap)
1245 if (!ns_capable(current_user_ns(), CAP_SETPCAP))
1247 if (!cap_valid(cap))
1250 new = prepare_creds();
1253 cap_lower(new->cap_bset, cap);
1254 return commit_creds(new);
1258 * cap_task_prctl - Implement process control functions for this security module
1259 * @option: The process control function requested
1260 * @arg2: The argument data for this function
1261 * @arg3: The argument data for this function
1262 * @arg4: The argument data for this function
1263 * @arg5: The argument data for this function
1265 * Allow process control functions (sys_prctl()) to alter capabilities; may
1266 * also deny access to other functions not otherwise implemented here.
1268 * Return: 0 or +ve on success, -ENOSYS if this function is not implemented
1269 * here, other -ve on error. If -ENOSYS is returned, sys_prctl() and other LSM
1270 * modules will consider performing the function.
1272 int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3,
1273 unsigned long arg4, unsigned long arg5)
1275 const struct cred *old = current_cred();
1279 case PR_CAPBSET_READ:
1280 if (!cap_valid(arg2))
1282 return !!cap_raised(old->cap_bset, arg2);
1284 case PR_CAPBSET_DROP:
1285 return cap_prctl_drop(arg2);
1288 * The next four prctl's remain to assist with transitioning a
1289 * system from legacy UID=0 based privilege (when filesystem
1290 * capabilities are not in use) to a system using filesystem
1291 * capabilities only - as the POSIX.1e draft intended.
1295 * PR_SET_SECUREBITS =
1296 * issecure_mask(SECURE_KEEP_CAPS_LOCKED)
1297 * | issecure_mask(SECURE_NOROOT)
1298 * | issecure_mask(SECURE_NOROOT_LOCKED)
1299 * | issecure_mask(SECURE_NO_SETUID_FIXUP)
1300 * | issecure_mask(SECURE_NO_SETUID_FIXUP_LOCKED)
1302 * will ensure that the current process and all of its
1303 * children will be locked into a pure
1304 * capability-based-privilege environment.
1306 case PR_SET_SECUREBITS:
1307 if ((((old->securebits & SECURE_ALL_LOCKS) >> 1)
1308 & (old->securebits ^ arg2)) /*[1]*/
1309 || ((old->securebits & SECURE_ALL_LOCKS & ~arg2)) /*[2]*/
1310 || (arg2 & ~(SECURE_ALL_LOCKS | SECURE_ALL_BITS)) /*[3]*/
1311 || (cap_capable(current_cred(),
1312 current_cred()->user_ns,
1314 CAP_OPT_NONE) != 0) /*[4]*/
1316 * [1] no changing of bits that are locked
1317 * [2] no unlocking of locks
1318 * [3] no setting of unsupported bits
1319 * [4] doing anything requires privilege (go read about
1320 * the "sendmail capabilities bug")
1323 /* cannot change a locked bit */
1326 new = prepare_creds();
1329 new->securebits = arg2;
1330 return commit_creds(new);
1332 case PR_GET_SECUREBITS:
1333 return old->securebits;
1335 case PR_GET_KEEPCAPS:
1336 return !!issecure(SECURE_KEEP_CAPS);
1338 case PR_SET_KEEPCAPS:
1339 if (arg2 > 1) /* Note, we rely on arg2 being unsigned here */
1341 if (issecure(SECURE_KEEP_CAPS_LOCKED))
1344 new = prepare_creds();
1348 new->securebits |= issecure_mask(SECURE_KEEP_CAPS);
1350 new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS);
1351 return commit_creds(new);
1353 case PR_CAP_AMBIENT:
1354 if (arg2 == PR_CAP_AMBIENT_CLEAR_ALL) {
1355 if (arg3 | arg4 | arg5)
1358 new = prepare_creds();
1361 cap_clear(new->cap_ambient);
1362 return commit_creds(new);
1365 if (((!cap_valid(arg3)) | arg4 | arg5))
1368 if (arg2 == PR_CAP_AMBIENT_IS_SET) {
1369 return !!cap_raised(current_cred()->cap_ambient, arg3);
1370 } else if (arg2 != PR_CAP_AMBIENT_RAISE &&
1371 arg2 != PR_CAP_AMBIENT_LOWER) {
1374 if (arg2 == PR_CAP_AMBIENT_RAISE &&
1375 (!cap_raised(current_cred()->cap_permitted, arg3) ||
1376 !cap_raised(current_cred()->cap_inheritable,
1378 issecure(SECURE_NO_CAP_AMBIENT_RAISE)))
1381 new = prepare_creds();
1384 if (arg2 == PR_CAP_AMBIENT_RAISE)
1385 cap_raise(new->cap_ambient, arg3);
1387 cap_lower(new->cap_ambient, arg3);
1388 return commit_creds(new);
1392 /* No functionality available - continue with default */
1398 * cap_vm_enough_memory - Determine whether a new virtual mapping is permitted
1399 * @mm: The VM space in which the new mapping is to be made
1400 * @pages: The size of the mapping
1402 * Determine whether the allocation of a new virtual mapping by the current
1403 * task is permitted.
1405 * Return: 1 if permission is granted, 0 if not.
1407 int cap_vm_enough_memory(struct mm_struct *mm, long pages)
1409 int cap_sys_admin = 0;
1411 if (cap_capable(current_cred(), &init_user_ns,
1412 CAP_SYS_ADMIN, CAP_OPT_NOAUDIT) == 0)
1415 return cap_sys_admin;
1419 * cap_mmap_addr - check if able to map given addr
1420 * @addr: address attempting to be mapped
1422 * If the process is attempting to map memory below dac_mmap_min_addr they need
1423 * CAP_SYS_RAWIO. The other parameters to this function are unused by the
1424 * capability security module.
1426 * Return: 0 if this mapping should be allowed or -EPERM if not.
1428 int cap_mmap_addr(unsigned long addr)
1432 if (addr < dac_mmap_min_addr) {
1433 ret = cap_capable(current_cred(), &init_user_ns, CAP_SYS_RAWIO,
1435 /* set PF_SUPERPRIV if it turns out we allow the low mmap */
1437 current->flags |= PF_SUPERPRIV;
1442 int cap_mmap_file(struct file *file, unsigned long reqprot,
1443 unsigned long prot, unsigned long flags)
1448 #ifdef CONFIG_SECURITY
1450 static struct security_hook_list capability_hooks[] __lsm_ro_after_init = {
1451 LSM_HOOK_INIT(capable, cap_capable),
1452 LSM_HOOK_INIT(settime, cap_settime),
1453 LSM_HOOK_INIT(ptrace_access_check, cap_ptrace_access_check),
1454 LSM_HOOK_INIT(ptrace_traceme, cap_ptrace_traceme),
1455 LSM_HOOK_INIT(capget, cap_capget),
1456 LSM_HOOK_INIT(capset, cap_capset),
1457 LSM_HOOK_INIT(bprm_creds_from_file, cap_bprm_creds_from_file),
1458 LSM_HOOK_INIT(inode_need_killpriv, cap_inode_need_killpriv),
1459 LSM_HOOK_INIT(inode_killpriv, cap_inode_killpriv),
1460 LSM_HOOK_INIT(inode_getsecurity, cap_inode_getsecurity),
1461 LSM_HOOK_INIT(mmap_addr, cap_mmap_addr),
1462 LSM_HOOK_INIT(mmap_file, cap_mmap_file),
1463 LSM_HOOK_INIT(task_fix_setuid, cap_task_fix_setuid),
1464 LSM_HOOK_INIT(task_prctl, cap_task_prctl),
1465 LSM_HOOK_INIT(task_setscheduler, cap_task_setscheduler),
1466 LSM_HOOK_INIT(task_setioprio, cap_task_setioprio),
1467 LSM_HOOK_INIT(task_setnice, cap_task_setnice),
1468 LSM_HOOK_INIT(vm_enough_memory, cap_vm_enough_memory),
1471 static int __init capability_init(void)
1473 security_add_hooks(capability_hooks, ARRAY_SIZE(capability_hooks),
1478 DEFINE_LSM(capability) = {
1479 .name = "capability",
1480 .order = LSM_ORDER_FIRST,
1481 .init = capability_init,
1484 #endif /* CONFIG_SECURITY */