1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /* Common capabilities, needed by capability.o.
3 */
4
5 #include <linux/capability.h>
6 #include <linux/audit.h>
7 #include <linux/init.h>
8 #include <linux/kernel.h>
9 #include <linux/lsm_hooks.h>
10 #include <linux/file.h>
11 #include <linux/mm.h>
12 #include <linux/mman.h>
13 #include <linux/pagemap.h>
14 #include <linux/swap.h>
15 #include <linux/skbuff.h>
16 #include <linux/netlink.h>
17 #include <linux/ptrace.h>
18 #include <linux/xattr.h>
19 #include <linux/hugetlb.h>
20 #include <linux/mount.h>
21 #include <linux/sched.h>
22 #include <linux/prctl.h>
23 #include <linux/securebits.h>
24 #include <linux/user_namespace.h>
25 #include <linux/binfmts.h>
26 #include <linux/personality.h>
27 #include <linux/mnt_idmapping.h>
28
29 /*
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.
37 *
38 * Warn if that happens, once per boot.
39 */
warn_setuid_and_fcaps_mixed(const char * fname)40 static void warn_setuid_and_fcaps_mixed(const char *fname)
41 {
42 static int warned;
43 if (!warned) {
44 printk(KERN_INFO "warning: `%s' has both setuid-root and"
45 " effective capabilities. Therefore not raising all"
46 " capabilities.\n", fname);
47 warned = 1;
48 }
49 }
50
51 /**
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
57 *
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.
60 *
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.
65 */
cap_capable(const struct cred * cred,struct user_namespace * targ_ns,int cap,unsigned int opts)66 int cap_capable(const struct cred *cred, struct user_namespace *targ_ns,
67 int cap, unsigned int opts)
68 {
69 struct user_namespace *ns = targ_ns;
70
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.
74 */
75 for (;;) {
76 /* Do we have the necessary capabilities? */
77 if (ns == cred->user_ns)
78 return cap_raised(cred->cap_effective, cap) ? 0 : -EPERM;
79
80 /*
81 * If we're already at a lower level than we're looking for,
82 * we're done searching.
83 */
84 if (ns->level <= cred->user_ns->level)
85 return -EPERM;
86
87 /*
88 * The owner of the user namespace in the parent of the
89 * user namespace has all caps.
90 */
91 if ((ns->parent == cred->user_ns) && uid_eq(ns->owner, cred->euid))
92 return 0;
93
94 /*
95 * If you have a capability in a parent user ns, then you have
96 * it over all children user namespaces as well.
97 */
98 ns = ns->parent;
99 }
100
101 /* We never get here */
102 }
103
104 /**
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
108 *
109 * Determine whether the current process may set the system clock and timezone
110 * information, returning 0 if permission granted, -ve if denied.
111 */
cap_settime(const struct timespec64 * ts,const struct timezone * tz)112 int cap_settime(const struct timespec64 *ts, const struct timezone *tz)
113 {
114 if (!capable(CAP_SYS_TIME))
115 return -EPERM;
116 return 0;
117 }
118
119 /**
120 * cap_ptrace_access_check - Determine whether the current process may access
121 * another
122 * @child: The process to be accessed
123 * @mode: The mode of attachment.
124 *
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
128 * access is allowed.
129 * Else denied.
130 *
131 * Determine whether a process may access another, returning 0 if permission
132 * granted, -ve if denied.
133 */
cap_ptrace_access_check(struct task_struct * child,unsigned int mode)134 int cap_ptrace_access_check(struct task_struct *child, unsigned int mode)
135 {
136 int ret = 0;
137 const struct cred *cred, *child_cred;
138 const kernel_cap_t *caller_caps;
139
140 rcu_read_lock();
141 cred = current_cred();
142 child_cred = __task_cred(child);
143 if (mode & PTRACE_MODE_FSCREDS)
144 caller_caps = &cred->cap_effective;
145 else
146 caller_caps = &cred->cap_permitted;
147 if (cred->user_ns == child_cred->user_ns &&
148 cap_issubset(child_cred->cap_permitted, *caller_caps))
149 goto out;
150 if (ns_capable(child_cred->user_ns, CAP_SYS_PTRACE))
151 goto out;
152 ret = -EPERM;
153 out:
154 rcu_read_unlock();
155 return ret;
156 }
157
158 /**
159 * cap_ptrace_traceme - Determine whether another process may trace the current
160 * @parent: The task proposed to be the tracer
161 *
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
165 * access is allowed.
166 * Else denied.
167 *
168 * Determine whether the nominated task is permitted to trace the current
169 * process, returning 0 if permission is granted, -ve if denied.
170 */
cap_ptrace_traceme(struct task_struct * parent)171 int cap_ptrace_traceme(struct task_struct *parent)
172 {
173 int ret = 0;
174 const struct cred *cred, *child_cred;
175
176 rcu_read_lock();
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))
181 goto out;
182 if (has_ns_capability(parent, child_cred->user_ns, CAP_SYS_PTRACE))
183 goto out;
184 ret = -EPERM;
185 out:
186 rcu_read_unlock();
187 return ret;
188 }
189
190 /**
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
196 *
197 * This function retrieves the capabilities of the nominated task and returns
198 * them to the caller.
199 */
cap_capget(struct task_struct * target,kernel_cap_t * effective,kernel_cap_t * inheritable,kernel_cap_t * permitted)200 int cap_capget(struct task_struct *target, kernel_cap_t *effective,
201 kernel_cap_t *inheritable, kernel_cap_t *permitted)
202 {
203 const struct cred *cred;
204
205 /* Derived from kernel/capability.c:sys_capget. */
206 rcu_read_lock();
207 cred = __task_cred(target);
208 *effective = cred->cap_effective;
209 *inheritable = cred->cap_inheritable;
210 *permitted = cred->cap_permitted;
211 rcu_read_unlock();
212 return 0;
213 }
214
215 /*
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.
218 */
cap_inh_is_capped(void)219 static inline int cap_inh_is_capped(void)
220 {
221 /* they are so limited unless the current task has the CAP_SETPCAP
222 * capability
223 */
224 if (cap_capable(current_cred(), current_cred()->user_ns,
225 CAP_SETPCAP, CAP_OPT_NONE) == 0)
226 return 0;
227 return 1;
228 }
229
230 /**
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
237 *
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.
241 */
cap_capset(struct cred * new,const struct cred * old,const kernel_cap_t * effective,const kernel_cap_t * inheritable,const kernel_cap_t * permitted)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)
247 {
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 */
253 return -EPERM;
254
255 if (!cap_issubset(*inheritable,
256 cap_combine(old->cap_inheritable,
257 old->cap_bset)))
258 /* no new pI capabilities outside bounding set */
259 return -EPERM;
260
261 /* verify restrictions on target's new Permitted set */
262 if (!cap_issubset(*permitted, old->cap_permitted))
263 return -EPERM;
264
265 /* verify the _new_Effective_ is a subset of the _new_Permitted_ */
266 if (!cap_issubset(*effective, *permitted))
267 return -EPERM;
268
269 new->cap_effective = *effective;
270 new->cap_inheritable = *inheritable;
271 new->cap_permitted = *permitted;
272
273 /*
274 * Mask off ambient bits that are no longer both permitted and
275 * inheritable.
276 */
277 new->cap_ambient = cap_intersect(new->cap_ambient,
278 cap_intersect(*permitted,
279 *inheritable));
280 if (WARN_ON(!cap_ambient_invariant_ok(new)))
281 return -EINVAL;
282 return 0;
283 }
284
285 /**
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
288 *
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.
292 *
293 * Return: 1 if security.capability has a value, meaning inode_killpriv()
294 * is required, 0 otherwise, meaning inode_killpriv() is not required.
295 */
cap_inode_need_killpriv(struct dentry * dentry)296 int cap_inode_need_killpriv(struct dentry *dentry)
297 {
298 struct inode *inode = d_backing_inode(dentry);
299 int error;
300
301 error = __vfs_getxattr(dentry, inode, XATTR_NAME_CAPS, NULL, 0);
302 return error > 0;
303 }
304
305 /**
306 * cap_inode_killpriv - Erase the security markings on an inode
307 *
308 * @mnt_userns: user namespace of the mount the inode was found from
309 * @dentry: The inode/dentry to alter
310 *
311 * Erase the privilege-enhancing security markings on an inode.
312 *
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.
318 *
319 * Return: 0 if successful, -ve on error.
320 */
cap_inode_killpriv(struct user_namespace * mnt_userns,struct dentry * dentry)321 int cap_inode_killpriv(struct user_namespace *mnt_userns, struct dentry *dentry)
322 {
323 int error;
324
325 error = __vfs_removexattr(mnt_userns, dentry, XATTR_NAME_CAPS);
326 if (error == -EOPNOTSUPP)
327 error = 0;
328 return error;
329 }
330
rootid_owns_currentns(kuid_t kroot)331 static bool rootid_owns_currentns(kuid_t kroot)
332 {
333 struct user_namespace *ns;
334
335 if (!uid_valid(kroot))
336 return false;
337
338 for (ns = current_user_ns(); ; ns = ns->parent) {
339 if (from_kuid(ns, kroot) == 0)
340 return true;
341 if (ns == &init_user_ns)
342 break;
343 }
344
345 return false;
346 }
347
sansflags(__u32 m)348 static __u32 sansflags(__u32 m)
349 {
350 return m & ~VFS_CAP_FLAGS_EFFECTIVE;
351 }
352
is_v2header(size_t size,const struct vfs_cap_data * cap)353 static bool is_v2header(size_t size, const struct vfs_cap_data *cap)
354 {
355 if (size != XATTR_CAPS_SZ_2)
356 return false;
357 return sansflags(le32_to_cpu(cap->magic_etc)) == VFS_CAP_REVISION_2;
358 }
359
is_v3header(size_t size,const struct vfs_cap_data * cap)360 static bool is_v3header(size_t size, const struct vfs_cap_data *cap)
361 {
362 if (size != XATTR_CAPS_SZ_3)
363 return false;
364 return sansflags(le32_to_cpu(cap->magic_etc)) == VFS_CAP_REVISION_3;
365 }
366
367 /*
368 * getsecurity: We are called for security.* before any attempt to read the
369 * xattr from the inode itself.
370 *
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.
373 *
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 -
376 * so that's good.
377 */
cap_inode_getsecurity(struct user_namespace * mnt_userns,struct inode * inode,const char * name,void ** buffer,bool alloc)378 int cap_inode_getsecurity(struct user_namespace *mnt_userns,
379 struct inode *inode, const char *name, void **buffer,
380 bool alloc)
381 {
382 int size, ret;
383 kuid_t kroot;
384 u32 nsmagic, magic;
385 uid_t root, mappedroot;
386 char *tmpbuf = NULL;
387 struct vfs_cap_data *cap;
388 struct vfs_ns_cap_data *nscap = NULL;
389 struct dentry *dentry;
390 struct user_namespace *fs_ns;
391
392 if (strcmp(name, "capability") != 0)
393 return -EOPNOTSUPP;
394
395 dentry = d_find_any_alias(inode);
396 if (!dentry)
397 return -EINVAL;
398
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);
402 dput(dentry);
403
404 if (ret < 0 || !tmpbuf)
405 return ret;
406
407 fs_ns = inode->i_sb->s_user_ns;
408 cap = (struct vfs_cap_data *) tmpbuf;
409 if (is_v2header((size_t) ret, cap)) {
410 root = 0;
411 } else if (is_v3header((size_t) ret, cap)) {
412 nscap = (struct vfs_ns_cap_data *) tmpbuf;
413 root = le32_to_cpu(nscap->rootid);
414 } else {
415 size = -EINVAL;
416 goto out_free;
417 }
418
419 kroot = make_kuid(fs_ns, root);
420
421 /* If this is an idmapped mount shift the kuid. */
422 kroot = mapped_kuid_fs(mnt_userns, fs_ns, kroot);
423
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);
429 if (alloc) {
430 if (!nscap) {
431 /* v2 -> v3 conversion */
432 nscap = kzalloc(size, GFP_ATOMIC);
433 if (!nscap) {
434 size = -ENOMEM;
435 goto out_free;
436 }
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);
443 } else {
444 /* use allocated v3 buffer */
445 tmpbuf = NULL;
446 }
447 nscap->rootid = cpu_to_le32(mappedroot);
448 *buffer = nscap;
449 }
450 goto out_free;
451 }
452
453 if (!rootid_owns_currentns(kroot)) {
454 size = -EOVERFLOW;
455 goto out_free;
456 }
457
458 /* This comes from a parent namespace. Return as a v2 capability */
459 size = sizeof(struct vfs_cap_data);
460 if (alloc) {
461 if (nscap) {
462 /* v3 -> v2 conversion */
463 cap = kzalloc(size, GFP_ATOMIC);
464 if (!cap) {
465 size = -ENOMEM;
466 goto out_free;
467 }
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);
474 } else {
475 /* use unconverted v2 */
476 tmpbuf = NULL;
477 }
478 *buffer = cap;
479 }
480 out_free:
481 kfree(tmpbuf);
482 return size;
483 }
484
485 /**
486 * rootid_from_xattr - translate root uid of vfs caps
487 *
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
493 *
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.
499 */
rootid_from_xattr(const void * value,size_t size,struct user_namespace * task_ns,struct user_namespace * mnt_userns,struct user_namespace * fs_userns)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)
504 {
505 const struct vfs_ns_cap_data *nscap = value;
506 kuid_t rootkid;
507 uid_t rootid = 0;
508
509 if (size == XATTR_CAPS_SZ_3)
510 rootid = le32_to_cpu(nscap->rootid);
511
512 rootkid = make_kuid(task_ns, rootid);
513 return mapped_kuid_user(mnt_userns, fs_userns, rootkid);
514 }
515
validheader(size_t size,const struct vfs_cap_data * cap)516 static bool validheader(size_t size, const struct vfs_cap_data *cap)
517 {
518 return is_v2header(size, cap) || is_v3header(size, cap);
519 }
520
521 /**
522 * cap_convert_nscap - check vfs caps
523 *
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
528 *
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.
531 *
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.
537 *
538 * Return: On success, return the new size; on error, return < 0.
539 */
cap_convert_nscap(struct user_namespace * mnt_userns,struct dentry * dentry,const void ** ivalue,size_t size)540 int cap_convert_nscap(struct user_namespace *mnt_userns, struct dentry *dentry,
541 const void **ivalue, size_t size)
542 {
543 struct vfs_ns_cap_data *nscap;
544 uid_t nsrootid;
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;
550 kuid_t rootid;
551 size_t newsize;
552
553 if (!*ivalue)
554 return -EINVAL;
555 if (!validheader(size, cap))
556 return -EINVAL;
557 if (!capable_wrt_inode_uidgid(mnt_userns, inode, CAP_SETFCAP))
558 return -EPERM;
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 */
562 return size;
563
564 rootid = rootid_from_xattr(*ivalue, size, task_ns, mnt_userns, fs_ns);
565 if (!uid_valid(rootid))
566 return -EINVAL;
567
568 nsrootid = from_kuid(fs_ns, rootid);
569 if (nsrootid == -1)
570 return -EINVAL;
571
572 newsize = sizeof(struct vfs_ns_cap_data);
573 nscap = kmalloc(newsize, GFP_ATOMIC);
574 if (!nscap)
575 return -ENOMEM;
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);
583
584 *ivalue = nscap;
585 return newsize;
586 }
587
588 /*
589 * Calculate the new process capability sets from the capability sets attached
590 * to a file.
591 */
bprm_caps_from_vfs_caps(struct cpu_vfs_cap_data * caps,struct linux_binprm * bprm,bool * effective,bool * has_fcap)592 static inline int bprm_caps_from_vfs_caps(struct cpu_vfs_cap_data *caps,
593 struct linux_binprm *bprm,
594 bool *effective,
595 bool *has_fcap)
596 {
597 struct cred *new = bprm->cred;
598 unsigned i;
599 int ret = 0;
600
601 if (caps->magic_etc & VFS_CAP_FLAGS_EFFECTIVE)
602 *effective = true;
603
604 if (caps->magic_etc & VFS_CAP_REVISION_MASK)
605 *has_fcap = true;
606
607 CAP_FOR_EACH_U32(i) {
608 __u32 permitted = caps->permitted.cap[i];
609 __u32 inheritable = caps->inheritable.cap[i];
610
611 /*
612 * pP' = (X & fP) | (pI & fI)
613 * The addition of pA' is handled later.
614 */
615 new->cap_permitted.cap[i] =
616 (new->cap_bset.cap[i] & permitted) |
617 (new->cap_inheritable.cap[i] & inheritable);
618
619 if (permitted & ~new->cap_permitted.cap[i])
620 /* insufficient to execute correctly */
621 ret = -EPERM;
622 }
623
624 /*
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.
628 */
629 return *effective ? ret : 0;
630 }
631
632 /**
633 * get_vfs_caps_from_disk - retrieve vfs caps from disk
634 *
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
638 *
639 * Extract the on-exec-apply capability sets for an executable file.
640 *
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.
646 */
get_vfs_caps_from_disk(struct user_namespace * mnt_userns,const struct dentry * dentry,struct cpu_vfs_cap_data * cpu_caps)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)
650 {
651 struct inode *inode = d_backing_inode(dentry);
652 __u32 magic_etc;
653 unsigned tocopy, i;
654 int size;
655 struct vfs_ns_cap_data data, *nscaps = &data;
656 struct vfs_cap_data *caps = (struct vfs_cap_data *) &data;
657 kuid_t rootkuid;
658 struct user_namespace *fs_ns;
659
660 memset(cpu_caps, 0, sizeof(struct cpu_vfs_cap_data));
661
662 if (!inode)
663 return -ENODATA;
664
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 */
670 return -ENODATA;
671
672 if (size < 0)
673 return size;
674
675 if (size < sizeof(magic_etc))
676 return -EINVAL;
677
678 cpu_caps->magic_etc = magic_etc = le32_to_cpu(caps->magic_etc);
679
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)
684 return -EINVAL;
685 tocopy = VFS_CAP_U32_1;
686 break;
687 case VFS_CAP_REVISION_2:
688 if (size != XATTR_CAPS_SZ_2)
689 return -EINVAL;
690 tocopy = VFS_CAP_U32_2;
691 break;
692 case VFS_CAP_REVISION_3:
693 if (size != XATTR_CAPS_SZ_3)
694 return -EINVAL;
695 tocopy = VFS_CAP_U32_3;
696 rootkuid = make_kuid(fs_ns, le32_to_cpu(nscaps->rootid));
697 break;
698
699 default:
700 return -EINVAL;
701 }
702 /* Limit the caps to the mounter of the filesystem
703 * or the more limited uid specified in the xattr.
704 */
705 rootkuid = mapped_kuid_fs(mnt_userns, fs_ns, rootkuid);
706 if (!rootid_owns_currentns(rootkuid))
707 return -ENODATA;
708
709 CAP_FOR_EACH_U32(i) {
710 if (i >= tocopy)
711 break;
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);
714 }
715
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;
718
719 cpu_caps->rootid = rootkuid;
720
721 return 0;
722 }
723
724 /*
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().
728 */
get_file_caps(struct linux_binprm * bprm,struct file * file,bool * effective,bool * has_fcap)729 static int get_file_caps(struct linux_binprm *bprm, struct file *file,
730 bool *effective, bool *has_fcap)
731 {
732 int rc = 0;
733 struct cpu_vfs_cap_data vcaps;
734
735 cap_clear(bprm->cred->cap_permitted);
736
737 if (!file_caps_enabled)
738 return 0;
739
740 if (!mnt_may_suid(file->f_path.mnt))
741 return 0;
742
743 /*
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
746 * descendants.
747 */
748 if (!current_in_userns(file->f_path.mnt->mnt_sb->s_user_ns))
749 return 0;
750
751 rc = get_vfs_caps_from_disk(file_mnt_user_ns(file),
752 file->f_path.dentry, &vcaps);
753 if (rc < 0) {
754 if (rc == -EINVAL)
755 printk(KERN_NOTICE "Invalid argument reading file caps for %s\n",
756 bprm->filename);
757 else if (rc == -ENODATA)
758 rc = 0;
759 goto out;
760 }
761
762 rc = bprm_caps_from_vfs_caps(&vcaps, bprm, effective, has_fcap);
763
764 out:
765 if (rc)
766 cap_clear(bprm->cred->cap_permitted);
767
768 return rc;
769 }
770
root_privileged(void)771 static inline bool root_privileged(void) { return !issecure(SECURE_NOROOT); }
772
__is_real(kuid_t uid,struct cred * cred)773 static inline bool __is_real(kuid_t uid, struct cred *cred)
774 { return uid_eq(cred->uid, uid); }
775
__is_eff(kuid_t uid,struct cred * cred)776 static inline bool __is_eff(kuid_t uid, struct cred *cred)
777 { return uid_eq(cred->euid, uid); }
778
__is_suid(kuid_t uid,struct cred * cred)779 static inline bool __is_suid(kuid_t uid, struct cred *cred)
780 { return !__is_real(uid, cred) && __is_eff(uid, cred); }
781
782 /*
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
788 *
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.
793 */
handle_privileged_root(struct linux_binprm * bprm,bool has_fcap,bool * effective,kuid_t root_uid)794 static void handle_privileged_root(struct linux_binprm *bprm, bool has_fcap,
795 bool *effective, kuid_t root_uid)
796 {
797 const struct cred *old = current_cred();
798 struct cred *new = bprm->cred;
799
800 if (!root_privileged())
801 return;
802 /*
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.
806 */
807 if (has_fcap && __is_suid(root_uid, new)) {
808 warn_setuid_and_fcaps_mixed(bprm->filename);
809 return;
810 }
811 /*
812 * To support inheritance of root-permissions and suid-root
813 * executables under compatibility mode, we override the
814 * capability sets for the file.
815 */
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);
820 }
821 /*
822 * If only the real uid is 0, we do not set the effective bit.
823 */
824 if (__is_eff(root_uid, new))
825 *effective = true;
826 }
827
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)
834
__is_setuid(struct cred * new,const struct cred * old)835 static inline bool __is_setuid(struct cred *new, const struct cred *old)
836 { return !uid_eq(new->euid, old->uid); }
837
__is_setgid(struct cred * new,const struct cred * old)838 static inline bool __is_setgid(struct cred *new, const struct cred *old)
839 { return !gid_eq(new->egid, old->gid); }
840
841 /*
842 * 1) Audit candidate if current->cap_effective is set
843 *
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.
849 *
850 * Number 1 above might fail if you don't have a full bset, but I think
851 * that is interesting information to audit.
852 *
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
857 */
nonroot_raised_pE(struct cred * new,const struct cred * old,kuid_t root,bool has_fcap)858 static inline bool nonroot_raised_pE(struct cred *new, const struct cred *old,
859 kuid_t root, bool has_fcap)
860 {
861 bool ret = false;
862
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) &&
871 ((has_fcap &&
872 __cap_gained(permitted, new, old)) ||
873 __cap_gained(ambient, new, old))))
874
875 ret = true;
876
877 return ret;
878 }
879
880 /**
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
884 *
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.
888 *
889 * Return: 0 if successful, -ve on error.
890 */
cap_bprm_creds_from_file(struct linux_binprm * bprm,struct file * file)891 int cap_bprm_creds_from_file(struct linux_binprm *bprm, struct file *file)
892 {
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;
897 int ret;
898 kuid_t root_uid;
899
900 if (WARN_ON(!cap_ambient_invariant_ok(old)))
901 return -EPERM;
902
903 ret = get_file_caps(bprm, file, &effective, &has_fcap);
904 if (ret < 0)
905 return ret;
906
907 root_uid = make_kuid(new->user_ns, 0);
908
909 handle_privileged_root(bprm, has_fcap, &effective, root_uid);
910
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;
914
915 /* Don't let someone trace a set[ug]id/setpcap binary with the revised
916 * credentials unless they have the appropriate permit.
917 *
918 * In addition, if NO_NEW_PRIVS, then ensure we get no new privs.
919 */
920 is_setid = __is_setuid(new, old) || __is_setgid(new, old);
921
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;
930 }
931 new->cap_permitted = cap_intersect(new->cap_permitted,
932 old->cap_permitted);
933 }
934
935 new->suid = new->fsuid = new->euid;
936 new->sgid = new->fsgid = new->egid;
937
938 /* File caps or setid cancels ambient. */
939 if (has_fcap || is_setid)
940 cap_clear(new->cap_ambient);
941
942 /*
943 * Now that we've computed pA', update pP' to give:
944 * pP' = (X & fP) | (pI & fI) | pA'
945 */
946 new->cap_permitted = cap_combine(new->cap_permitted, new->cap_ambient);
947
948 /*
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'.
951 */
952 if (effective)
953 new->cap_effective = new->cap_permitted;
954 else
955 new->cap_effective = new->cap_ambient;
956
957 if (WARN_ON(!cap_ambient_invariant_ok(new)))
958 return -EPERM;
959
960 if (nonroot_raised_pE(new, old, root_uid, has_fcap)) {
961 ret = audit_log_bprm_fcaps(bprm, new, old);
962 if (ret < 0)
963 return ret;
964 }
965
966 new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS);
967
968 if (WARN_ON(!cap_ambient_invariant_ok(new)))
969 return -EPERM;
970
971 /* Check for privilege-elevated exec. */
972 if (is_setid ||
973 (!__is_real(root_uid, new) &&
974 (effective ||
975 __cap_grew(permitted, ambient, new))))
976 bprm->secureexec = 1;
977
978 return 0;
979 }
980
981 /**
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
988 *
989 * Determine whether an xattr may be altered or set on an inode, returning 0 if
990 * permission is granted, -ve if denied.
991 *
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.
994 */
cap_inode_setxattr(struct dentry * dentry,const char * name,const void * value,size_t size,int flags)995 int cap_inode_setxattr(struct dentry *dentry, const char *name,
996 const void *value, size_t size, int flags)
997 {
998 struct user_namespace *user_ns = dentry->d_sb->s_user_ns;
999
1000 /* Ignore non-security xattrs */
1001 if (strncmp(name, XATTR_SECURITY_PREFIX,
1002 XATTR_SECURITY_PREFIX_LEN) != 0)
1003 return 0;
1004
1005 /*
1006 * For XATTR_NAME_CAPS the check will be done in
1007 * cap_convert_nscap(), called by setxattr()
1008 */
1009 if (strcmp(name, XATTR_NAME_CAPS) == 0)
1010 return 0;
1011
1012 if (!ns_capable(user_ns, CAP_SYS_ADMIN))
1013 return -EPERM;
1014 return 0;
1015 }
1016
1017 /**
1018 * cap_inode_removexattr - Determine whether an xattr may be removed
1019 *
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
1023 *
1024 * Determine whether an xattr may be removed from an inode, returning 0 if
1025 * permission is granted, -ve if denied.
1026 *
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.
1032 *
1033 * This is used to make sure security xattrs don't get removed by those who
1034 * aren't privileged to remove them.
1035 */
cap_inode_removexattr(struct user_namespace * mnt_userns,struct dentry * dentry,const char * name)1036 int cap_inode_removexattr(struct user_namespace *mnt_userns,
1037 struct dentry *dentry, const char *name)
1038 {
1039 struct user_namespace *user_ns = dentry->d_sb->s_user_ns;
1040
1041 /* Ignore non-security xattrs */
1042 if (strncmp(name, XATTR_SECURITY_PREFIX,
1043 XATTR_SECURITY_PREFIX_LEN) != 0)
1044 return 0;
1045
1046 if (strcmp(name, XATTR_NAME_CAPS) == 0) {
1047 /* security.capability gets namespaced */
1048 struct inode *inode = d_backing_inode(dentry);
1049 if (!inode)
1050 return -EINVAL;
1051 if (!capable_wrt_inode_uidgid(mnt_userns, inode, CAP_SETFCAP))
1052 return -EPERM;
1053 return 0;
1054 }
1055
1056 if (!ns_capable(user_ns, CAP_SYS_ADMIN))
1057 return -EPERM;
1058 return 0;
1059 }
1060
1061 /*
1062 * cap_emulate_setxuid() fixes the effective / permitted capabilities of
1063 * a process after a call to setuid, setreuid, or setresuid.
1064 *
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
1067 * cleared.
1068 *
1069 * 2) When set*uiding _from_ euid == 0 _to_ euid != 0, the effective
1070 * capabilities of the process are cleared.
1071 *
1072 * 3) When set*uiding _from_ euid != 0 _to_ euid == 0, the effective
1073 * capabilities are set to the permitted capabilities.
1074 *
1075 * fsuid is handled elsewhere. fsuid == 0 and {r,e,s}uid!= 0 should
1076 * never happen.
1077 *
1078 * -astor
1079 *
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
1087 * files..
1088 * Thanks to Olaf Kirch and Peter Benie for spotting this.
1089 */
cap_emulate_setxuid(struct cred * new,const struct cred * old)1090 static inline void cap_emulate_setxuid(struct cred *new, const struct cred *old)
1091 {
1092 kuid_t root_uid = make_kuid(old->user_ns, 0);
1093
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);
1103 }
1104
1105 /*
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.
1109 */
1110 cap_clear(new->cap_ambient);
1111 }
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;
1116 }
1117
1118 /**
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
1123 *
1124 * Fix up the results of setuid() call before the credential changes are
1125 * actually applied.
1126 *
1127 * Return: 0 to grant the changes, -ve to deny them.
1128 */
cap_task_fix_setuid(struct cred * new,const struct cred * old,int flags)1129 int cap_task_fix_setuid(struct cred *new, const struct cred *old, int flags)
1130 {
1131 switch (flags) {
1132 case LSM_SETID_RE:
1133 case LSM_SETID_ID:
1134 case LSM_SETID_RES:
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);
1139 break;
1140
1141 case LSM_SETID_FS:
1142 /* juggle the capabilties to follow FSUID changes, unless
1143 * otherwise suppressed
1144 *
1145 * FIXME - is fsuser used for all CAP_FS_MASK capabilities?
1146 * if not, we might be a bit too harsh here.
1147 */
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);
1153
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);
1158 }
1159 break;
1160
1161 default:
1162 return -EINVAL;
1163 }
1164
1165 return 0;
1166 }
1167
1168 /*
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.
1177 */
cap_safe_nice(struct task_struct * p)1178 static int cap_safe_nice(struct task_struct *p)
1179 {
1180 int is_subset, ret = 0;
1181
1182 rcu_read_lock();
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))
1186 ret = -EPERM;
1187 rcu_read_unlock();
1188
1189 return ret;
1190 }
1191
1192 /**
1193 * cap_task_setscheduler - Detemine if scheduler policy change is permitted
1194 * @p: The task to affect
1195 *
1196 * Detemine if the requested scheduler policy change is permitted for the
1197 * specified task.
1198 *
1199 * Return: 0 if permission is granted, -ve if denied.
1200 */
cap_task_setscheduler(struct task_struct * p)1201 int cap_task_setscheduler(struct task_struct *p)
1202 {
1203 return cap_safe_nice(p);
1204 }
1205
1206 /**
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
1210 *
1211 * Detemine if the requested I/O priority change is permitted for the specified
1212 * task.
1213 *
1214 * Return: 0 if permission is granted, -ve if denied.
1215 */
cap_task_setioprio(struct task_struct * p,int ioprio)1216 int cap_task_setioprio(struct task_struct *p, int ioprio)
1217 {
1218 return cap_safe_nice(p);
1219 }
1220
1221 /**
1222 * cap_task_setnice - Detemine if task priority change is permitted
1223 * @p: The task to affect
1224 * @nice: The nice value to set
1225 *
1226 * Detemine if the requested task priority change is permitted for the
1227 * specified task.
1228 *
1229 * Return: 0 if permission is granted, -ve if denied.
1230 */
cap_task_setnice(struct task_struct * p,int nice)1231 int cap_task_setnice(struct task_struct *p, int nice)
1232 {
1233 return cap_safe_nice(p);
1234 }
1235
1236 /*
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.
1239 */
cap_prctl_drop(unsigned long cap)1240 static int cap_prctl_drop(unsigned long cap)
1241 {
1242 struct cred *new;
1243
1244 if (!ns_capable(current_user_ns(), CAP_SETPCAP))
1245 return -EPERM;
1246 if (!cap_valid(cap))
1247 return -EINVAL;
1248
1249 new = prepare_creds();
1250 if (!new)
1251 return -ENOMEM;
1252 cap_lower(new->cap_bset, cap);
1253 return commit_creds(new);
1254 }
1255
1256 /**
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
1263 *
1264 * Allow process control functions (sys_prctl()) to alter capabilities; may
1265 * also deny access to other functions not otherwise implemented here.
1266 *
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.
1270 */
cap_task_prctl(int option,unsigned long arg2,unsigned long arg3,unsigned long arg4,unsigned long arg5)1271 int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3,
1272 unsigned long arg4, unsigned long arg5)
1273 {
1274 const struct cred *old = current_cred();
1275 struct cred *new;
1276
1277 switch (option) {
1278 case PR_CAPBSET_READ:
1279 if (!cap_valid(arg2))
1280 return -EINVAL;
1281 return !!cap_raised(old->cap_bset, arg2);
1282
1283 case PR_CAPBSET_DROP:
1284 return cap_prctl_drop(arg2);
1285
1286 /*
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.
1291 *
1292 * Note:
1293 *
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)
1300 *
1301 * will ensure that the current process and all of its
1302 * children will be locked into a pure
1303 * capability-based-privilege environment.
1304 */
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,
1312 CAP_SETPCAP,
1313 CAP_OPT_NONE) != 0) /*[4]*/
1314 /*
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")
1320 */
1321 )
1322 /* cannot change a locked bit */
1323 return -EPERM;
1324
1325 new = prepare_creds();
1326 if (!new)
1327 return -ENOMEM;
1328 new->securebits = arg2;
1329 return commit_creds(new);
1330
1331 case PR_GET_SECUREBITS:
1332 return old->securebits;
1333
1334 case PR_GET_KEEPCAPS:
1335 return !!issecure(SECURE_KEEP_CAPS);
1336
1337 case PR_SET_KEEPCAPS:
1338 if (arg2 > 1) /* Note, we rely on arg2 being unsigned here */
1339 return -EINVAL;
1340 if (issecure(SECURE_KEEP_CAPS_LOCKED))
1341 return -EPERM;
1342
1343 new = prepare_creds();
1344 if (!new)
1345 return -ENOMEM;
1346 if (arg2)
1347 new->securebits |= issecure_mask(SECURE_KEEP_CAPS);
1348 else
1349 new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS);
1350 return commit_creds(new);
1351
1352 case PR_CAP_AMBIENT:
1353 if (arg2 == PR_CAP_AMBIENT_CLEAR_ALL) {
1354 if (arg3 | arg4 | arg5)
1355 return -EINVAL;
1356
1357 new = prepare_creds();
1358 if (!new)
1359 return -ENOMEM;
1360 cap_clear(new->cap_ambient);
1361 return commit_creds(new);
1362 }
1363
1364 if (((!cap_valid(arg3)) | arg4 | arg5))
1365 return -EINVAL;
1366
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) {
1371 return -EINVAL;
1372 } else {
1373 if (arg2 == PR_CAP_AMBIENT_RAISE &&
1374 (!cap_raised(current_cred()->cap_permitted, arg3) ||
1375 !cap_raised(current_cred()->cap_inheritable,
1376 arg3) ||
1377 issecure(SECURE_NO_CAP_AMBIENT_RAISE)))
1378 return -EPERM;
1379
1380 new = prepare_creds();
1381 if (!new)
1382 return -ENOMEM;
1383 if (arg2 == PR_CAP_AMBIENT_RAISE)
1384 cap_raise(new->cap_ambient, arg3);
1385 else
1386 cap_lower(new->cap_ambient, arg3);
1387 return commit_creds(new);
1388 }
1389
1390 default:
1391 /* No functionality available - continue with default */
1392 return -ENOSYS;
1393 }
1394 }
1395
1396 /**
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
1400 *
1401 * Determine whether the allocation of a new virtual mapping by the current
1402 * task is permitted.
1403 *
1404 * Return: 1 if permission is granted, 0 if not.
1405 */
cap_vm_enough_memory(struct mm_struct * mm,long pages)1406 int cap_vm_enough_memory(struct mm_struct *mm, long pages)
1407 {
1408 int cap_sys_admin = 0;
1409
1410 if (cap_capable(current_cred(), &init_user_ns,
1411 CAP_SYS_ADMIN, CAP_OPT_NOAUDIT) == 0)
1412 cap_sys_admin = 1;
1413
1414 return cap_sys_admin;
1415 }
1416
1417 /**
1418 * cap_mmap_addr - check if able to map given addr
1419 * @addr: address attempting to be mapped
1420 *
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.
1424 *
1425 * Return: 0 if this mapping should be allowed or -EPERM if not.
1426 */
cap_mmap_addr(unsigned long addr)1427 int cap_mmap_addr(unsigned long addr)
1428 {
1429 int ret = 0;
1430
1431 if (addr < dac_mmap_min_addr) {
1432 ret = cap_capable(current_cred(), &init_user_ns, CAP_SYS_RAWIO,
1433 CAP_OPT_NONE);
1434 /* set PF_SUPERPRIV if it turns out we allow the low mmap */
1435 if (ret == 0)
1436 current->flags |= PF_SUPERPRIV;
1437 }
1438 return ret;
1439 }
1440
cap_mmap_file(struct file * file,unsigned long reqprot,unsigned long prot,unsigned long flags)1441 int cap_mmap_file(struct file *file, unsigned long reqprot,
1442 unsigned long prot, unsigned long flags)
1443 {
1444 return 0;
1445 }
1446
1447 #ifdef CONFIG_SECURITY
1448
1449 static struct security_hook_list capability_hooks[] __lsm_ro_after_init = {
1450 LSM_HOOK_INIT(capable, cap_capable),
1451 LSM_HOOK_INIT(settime, cap_settime),
1452 LSM_HOOK_INIT(ptrace_access_check, cap_ptrace_access_check),
1453 LSM_HOOK_INIT(ptrace_traceme, cap_ptrace_traceme),
1454 LSM_HOOK_INIT(capget, cap_capget),
1455 LSM_HOOK_INIT(capset, cap_capset),
1456 LSM_HOOK_INIT(bprm_creds_from_file, cap_bprm_creds_from_file),
1457 LSM_HOOK_INIT(inode_need_killpriv, cap_inode_need_killpriv),
1458 LSM_HOOK_INIT(inode_killpriv, cap_inode_killpriv),
1459 LSM_HOOK_INIT(inode_getsecurity, cap_inode_getsecurity),
1460 LSM_HOOK_INIT(mmap_addr, cap_mmap_addr),
1461 LSM_HOOK_INIT(mmap_file, cap_mmap_file),
1462 LSM_HOOK_INIT(task_fix_setuid, cap_task_fix_setuid),
1463 LSM_HOOK_INIT(task_prctl, cap_task_prctl),
1464 LSM_HOOK_INIT(task_setscheduler, cap_task_setscheduler),
1465 LSM_HOOK_INIT(task_setioprio, cap_task_setioprio),
1466 LSM_HOOK_INIT(task_setnice, cap_task_setnice),
1467 LSM_HOOK_INIT(vm_enough_memory, cap_vm_enough_memory),
1468 };
1469
capability_init(void)1470 static int __init capability_init(void)
1471 {
1472 security_add_hooks(capability_hooks, ARRAY_SIZE(capability_hooks),
1473 "capability");
1474 return 0;
1475 }
1476
1477 DEFINE_LSM(capability) = {
1478 .name = "capability",
1479 .order = LSM_ORDER_FIRST,
1480 .init = capability_init,
1481 };
1482
1483 #endif /* CONFIG_SECURITY */
1484