Line data Source code
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 : */
40 : static void warn_setuid_and_fcaps_mixed(const char *fname)
41 : {
42 : static int warned;
43 0 : if (!warned) {
44 0 : printk(KERN_INFO "warning: `%s' has both setuid-root and"
45 : " effective capabilities. Therefore not raising all"
46 : " capabilities.\n", fname);
47 0 : 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 : */
66 1 : int cap_capable(const struct cred *cred, struct user_namespace *targ_ns,
67 : int cap, unsigned int opts)
68 : {
69 1 : 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 1 : if (ns == cred->user_ns)
78 1 : 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 0 : 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 0 : 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 : */
112 0 : int cap_settime(const struct timespec64 *ts, const struct timezone *tz)
113 : {
114 0 : if (!capable(CAP_SYS_TIME))
115 : return -EPERM;
116 0 : 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 : */
134 0 : int cap_ptrace_access_check(struct task_struct *child, unsigned int mode)
135 : {
136 0 : int ret = 0;
137 : const struct cred *cred, *child_cred;
138 : const kernel_cap_t *caller_caps;
139 :
140 : rcu_read_lock();
141 0 : cred = current_cred();
142 0 : child_cred = __task_cred(child);
143 0 : if (mode & PTRACE_MODE_FSCREDS)
144 0 : caller_caps = &cred->cap_effective;
145 : else
146 0 : caller_caps = &cred->cap_permitted;
147 0 : if (cred->user_ns == child_cred->user_ns &&
148 : cap_issubset(child_cred->cap_permitted, *caller_caps))
149 : goto out;
150 0 : if (ns_capable(child_cred->user_ns, CAP_SYS_PTRACE))
151 : goto out;
152 0 : ret = -EPERM;
153 : out:
154 : rcu_read_unlock();
155 0 : 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 : */
171 0 : int cap_ptrace_traceme(struct task_struct *parent)
172 : {
173 0 : int ret = 0;
174 : const struct cred *cred, *child_cred;
175 :
176 : rcu_read_lock();
177 0 : cred = __task_cred(parent);
178 0 : child_cred = current_cred();
179 0 : if (cred->user_ns == child_cred->user_ns &&
180 : cap_issubset(child_cred->cap_permitted, cred->cap_permitted))
181 : goto out;
182 0 : if (has_ns_capability(parent, child_cred->user_ns, CAP_SYS_PTRACE))
183 : goto out;
184 0 : ret = -EPERM;
185 : out:
186 : rcu_read_unlock();
187 0 : 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 : */
200 0 : 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 0 : cred = __task_cred(target);
208 0 : *effective = cred->cap_effective;
209 0 : *inheritable = cred->cap_inheritable;
210 0 : *permitted = cred->cap_permitted;
211 : rcu_read_unlock();
212 0 : 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 : */
219 0 : 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 0 : if (cap_capable(current_cred(), current_cred()->user_ns,
225 : CAP_SETPCAP, CAP_OPT_NONE) == 0)
226 : return 0;
227 0 : 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 : */
242 0 : 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 0 : 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 0 : 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 0 : if (!cap_issubset(*permitted, old->cap_permitted))
263 : return -EPERM;
264 :
265 : /* verify the _new_Effective_ is a subset of the _new_Permitted_ */
266 0 : if (!cap_issubset(*effective, *permitted))
267 : return -EPERM;
268 :
269 0 : new->cap_effective = *effective;
270 0 : new->cap_inheritable = *inheritable;
271 0 : new->cap_permitted = *permitted;
272 :
273 : /*
274 : * Mask off ambient bits that are no longer both permitted and
275 : * inheritable.
276 : */
277 0 : new->cap_ambient = cap_intersect(new->cap_ambient,
278 : cap_intersect(*permitted,
279 : *inheritable));
280 0 : if (WARN_ON(!cap_ambient_invariant_ok(new)))
281 : return -EINVAL;
282 0 : 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 : */
296 0 : int cap_inode_need_killpriv(struct dentry *dentry)
297 : {
298 0 : struct inode *inode = d_backing_inode(dentry);
299 : int error;
300 :
301 0 : error = __vfs_getxattr(dentry, inode, XATTR_NAME_CAPS, NULL, 0);
302 0 : return error > 0;
303 : }
304 :
305 : /**
306 : * cap_inode_killpriv - Erase the security markings on an inode
307 : *
308 : * @idmap: idmap 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 idmap of
314 : * the vfsmount must be passed through @idmap. This function will then
315 : * take care to map the inode according to @idmap before checking
316 : * permissions. On non-idmapped mounts or if permission checking is to be
317 : * performed on the raw inode simply passs @nop_mnt_idmap.
318 : *
319 : * Return: 0 if successful, -ve on error.
320 : */
321 0 : int cap_inode_killpriv(struct mnt_idmap *idmap, struct dentry *dentry)
322 : {
323 : int error;
324 :
325 0 : error = __vfs_removexattr(idmap, dentry, XATTR_NAME_CAPS);
326 0 : if (error == -EOPNOTSUPP)
327 0 : error = 0;
328 0 : return error;
329 : }
330 :
331 : static bool rootid_owns_currentns(vfsuid_t rootvfsuid)
332 : {
333 : struct user_namespace *ns;
334 : kuid_t kroot;
335 :
336 0 : if (!vfsuid_valid(rootvfsuid))
337 : return false;
338 :
339 0 : kroot = vfsuid_into_kuid(rootvfsuid);
340 0 : for (ns = current_user_ns();; ns = ns->parent) {
341 0 : if (from_kuid(ns, kroot) == 0)
342 : return true;
343 : if (ns == &init_user_ns)
344 : break;
345 : }
346 :
347 : return false;
348 : }
349 :
350 : static __u32 sansflags(__u32 m)
351 : {
352 0 : return m & ~VFS_CAP_FLAGS_EFFECTIVE;
353 : }
354 :
355 : static bool is_v2header(int size, const struct vfs_cap_data *cap)
356 : {
357 0 : if (size != XATTR_CAPS_SZ_2)
358 : return false;
359 0 : return sansflags(le32_to_cpu(cap->magic_etc)) == VFS_CAP_REVISION_2;
360 : }
361 :
362 : static bool is_v3header(int size, const struct vfs_cap_data *cap)
363 : {
364 0 : if (size != XATTR_CAPS_SZ_3)
365 : return false;
366 0 : return sansflags(le32_to_cpu(cap->magic_etc)) == VFS_CAP_REVISION_3;
367 : }
368 :
369 : /*
370 : * getsecurity: We are called for security.* before any attempt to read the
371 : * xattr from the inode itself.
372 : *
373 : * This gives us a chance to read the on-disk value and convert it. If we
374 : * return -EOPNOTSUPP, then vfs_getxattr() will call the i_op handler.
375 : *
376 : * Note we are not called by vfs_getxattr_alloc(), but that is only called
377 : * by the integrity subsystem, which really wants the unconverted values -
378 : * so that's good.
379 : */
380 0 : int cap_inode_getsecurity(struct mnt_idmap *idmap,
381 : struct inode *inode, const char *name, void **buffer,
382 : bool alloc)
383 : {
384 : int size;
385 : kuid_t kroot;
386 : vfsuid_t vfsroot;
387 : u32 nsmagic, magic;
388 : uid_t root, mappedroot;
389 0 : char *tmpbuf = NULL;
390 : struct vfs_cap_data *cap;
391 0 : struct vfs_ns_cap_data *nscap = NULL;
392 : struct dentry *dentry;
393 : struct user_namespace *fs_ns;
394 :
395 0 : if (strcmp(name, "capability") != 0)
396 : return -EOPNOTSUPP;
397 :
398 0 : dentry = d_find_any_alias(inode);
399 0 : if (!dentry)
400 : return -EINVAL;
401 0 : size = vfs_getxattr_alloc(idmap, dentry, XATTR_NAME_CAPS, &tmpbuf,
402 : sizeof(struct vfs_ns_cap_data), GFP_NOFS);
403 0 : dput(dentry);
404 : /* gcc11 complains if we don't check for !tmpbuf */
405 0 : if (size < 0 || !tmpbuf)
406 : goto out_free;
407 :
408 0 : fs_ns = inode->i_sb->s_user_ns;
409 0 : cap = (struct vfs_cap_data *) tmpbuf;
410 0 : if (is_v2header(size, cap)) {
411 : root = 0;
412 0 : } else if (is_v3header(size, cap)) {
413 0 : nscap = (struct vfs_ns_cap_data *) tmpbuf;
414 0 : root = le32_to_cpu(nscap->rootid);
415 : } else {
416 : size = -EINVAL;
417 : goto out_free;
418 : }
419 :
420 0 : kroot = make_kuid(fs_ns, root);
421 :
422 : /* If this is an idmapped mount shift the kuid. */
423 0 : vfsroot = make_vfsuid(idmap, fs_ns, kroot);
424 :
425 : /* If the root kuid maps to a valid uid in current ns, then return
426 : * this as a nscap. */
427 0 : mappedroot = from_kuid(current_user_ns(), vfsuid_into_kuid(vfsroot));
428 0 : if (mappedroot != (uid_t)-1 && mappedroot != (uid_t)0) {
429 0 : size = sizeof(struct vfs_ns_cap_data);
430 0 : if (alloc) {
431 0 : if (!nscap) {
432 : /* v2 -> v3 conversion */
433 0 : nscap = kzalloc(size, GFP_ATOMIC);
434 0 : if (!nscap) {
435 : size = -ENOMEM;
436 : goto out_free;
437 : }
438 0 : nsmagic = VFS_CAP_REVISION_3;
439 0 : magic = le32_to_cpu(cap->magic_etc);
440 0 : if (magic & VFS_CAP_FLAGS_EFFECTIVE)
441 0 : nsmagic |= VFS_CAP_FLAGS_EFFECTIVE;
442 0 : memcpy(&nscap->data, &cap->data, sizeof(__le32) * 2 * VFS_CAP_U32);
443 0 : nscap->magic_etc = cpu_to_le32(nsmagic);
444 : } else {
445 : /* use allocated v3 buffer */
446 0 : tmpbuf = NULL;
447 : }
448 0 : nscap->rootid = cpu_to_le32(mappedroot);
449 0 : *buffer = nscap;
450 : }
451 : goto out_free;
452 : }
453 :
454 0 : if (!rootid_owns_currentns(vfsroot)) {
455 : size = -EOVERFLOW;
456 : goto out_free;
457 : }
458 :
459 : /* This comes from a parent namespace. Return as a v2 capability */
460 0 : size = sizeof(struct vfs_cap_data);
461 0 : if (alloc) {
462 0 : if (nscap) {
463 : /* v3 -> v2 conversion */
464 0 : cap = kzalloc(size, GFP_ATOMIC);
465 0 : if (!cap) {
466 : size = -ENOMEM;
467 : goto out_free;
468 : }
469 0 : magic = VFS_CAP_REVISION_2;
470 0 : nsmagic = le32_to_cpu(nscap->magic_etc);
471 0 : if (nsmagic & VFS_CAP_FLAGS_EFFECTIVE)
472 0 : magic |= VFS_CAP_FLAGS_EFFECTIVE;
473 0 : memcpy(&cap->data, &nscap->data, sizeof(__le32) * 2 * VFS_CAP_U32);
474 0 : cap->magic_etc = cpu_to_le32(magic);
475 : } else {
476 : /* use unconverted v2 */
477 0 : tmpbuf = NULL;
478 : }
479 0 : *buffer = cap;
480 : }
481 : out_free:
482 0 : kfree(tmpbuf);
483 0 : return size;
484 : }
485 :
486 : /**
487 : * rootid_from_xattr - translate root uid of vfs caps
488 : *
489 : * @value: vfs caps value which may be modified by this function
490 : * @size: size of @ivalue
491 : * @task_ns: user namespace of the caller
492 : */
493 : static vfsuid_t rootid_from_xattr(const void *value, size_t size,
494 : struct user_namespace *task_ns)
495 : {
496 0 : const struct vfs_ns_cap_data *nscap = value;
497 0 : uid_t rootid = 0;
498 :
499 0 : if (size == XATTR_CAPS_SZ_3)
500 0 : rootid = le32_to_cpu(nscap->rootid);
501 :
502 0 : return VFSUIDT_INIT(make_kuid(task_ns, rootid));
503 : }
504 :
505 : static bool validheader(size_t size, const struct vfs_cap_data *cap)
506 : {
507 0 : return is_v2header(size, cap) || is_v3header(size, cap);
508 : }
509 :
510 : /**
511 : * cap_convert_nscap - check vfs caps
512 : *
513 : * @idmap: idmap of the mount the inode was found from
514 : * @dentry: used to retrieve inode to check permissions on
515 : * @ivalue: vfs caps value which may be modified by this function
516 : * @size: size of @ivalue
517 : *
518 : * User requested a write of security.capability. If needed, update the
519 : * xattr to change from v2 to v3, or to fixup the v3 rootid.
520 : *
521 : * If the inode has been found through an idmapped mount the idmap of
522 : * the vfsmount must be passed through @idmap. This function will then
523 : * take care to map the inode according to @idmap before checking
524 : * permissions. On non-idmapped mounts or if permission checking is to be
525 : * performed on the raw inode simply passs @nop_mnt_idmap.
526 : *
527 : * Return: On success, return the new size; on error, return < 0.
528 : */
529 0 : int cap_convert_nscap(struct mnt_idmap *idmap, struct dentry *dentry,
530 : const void **ivalue, size_t size)
531 : {
532 : struct vfs_ns_cap_data *nscap;
533 : uid_t nsrootid;
534 0 : const struct vfs_cap_data *cap = *ivalue;
535 : __u32 magic, nsmagic;
536 0 : struct inode *inode = d_backing_inode(dentry);
537 0 : struct user_namespace *task_ns = current_user_ns(),
538 0 : *fs_ns = inode->i_sb->s_user_ns;
539 : kuid_t rootid;
540 : vfsuid_t vfsrootid;
541 : size_t newsize;
542 :
543 0 : if (!*ivalue)
544 : return -EINVAL;
545 0 : if (!validheader(size, cap))
546 : return -EINVAL;
547 0 : if (!capable_wrt_inode_uidgid(idmap, inode, CAP_SETFCAP))
548 : return -EPERM;
549 0 : if (size == XATTR_CAPS_SZ_2 && (idmap == &nop_mnt_idmap))
550 0 : if (ns_capable(inode->i_sb->s_user_ns, CAP_SETFCAP))
551 : /* user is privileged, just write the v2 */
552 : return size;
553 :
554 0 : vfsrootid = rootid_from_xattr(*ivalue, size, task_ns);
555 0 : if (!vfsuid_valid(vfsrootid))
556 : return -EINVAL;
557 :
558 0 : rootid = from_vfsuid(idmap, fs_ns, vfsrootid);
559 0 : if (!uid_valid(rootid))
560 : return -EINVAL;
561 :
562 0 : nsrootid = from_kuid(fs_ns, rootid);
563 : if (nsrootid == -1)
564 : return -EINVAL;
565 :
566 0 : newsize = sizeof(struct vfs_ns_cap_data);
567 0 : nscap = kmalloc(newsize, GFP_ATOMIC);
568 0 : if (!nscap)
569 : return -ENOMEM;
570 0 : nscap->rootid = cpu_to_le32(nsrootid);
571 0 : nsmagic = VFS_CAP_REVISION_3;
572 0 : magic = le32_to_cpu(cap->magic_etc);
573 0 : if (magic & VFS_CAP_FLAGS_EFFECTIVE)
574 0 : nsmagic |= VFS_CAP_FLAGS_EFFECTIVE;
575 0 : nscap->magic_etc = cpu_to_le32(nsmagic);
576 0 : memcpy(&nscap->data, &cap->data, sizeof(__le32) * 2 * VFS_CAP_U32);
577 :
578 0 : *ivalue = nscap;
579 0 : return newsize;
580 : }
581 :
582 : /*
583 : * Calculate the new process capability sets from the capability sets attached
584 : * to a file.
585 : */
586 0 : static inline int bprm_caps_from_vfs_caps(struct cpu_vfs_cap_data *caps,
587 : struct linux_binprm *bprm,
588 : bool *effective,
589 : bool *has_fcap)
590 : {
591 0 : struct cred *new = bprm->cred;
592 0 : int ret = 0;
593 :
594 0 : if (caps->magic_etc & VFS_CAP_FLAGS_EFFECTIVE)
595 0 : *effective = true;
596 :
597 0 : if (caps->magic_etc & VFS_CAP_REVISION_MASK)
598 0 : *has_fcap = true;
599 :
600 : /*
601 : * pP' = (X & fP) | (pI & fI)
602 : * The addition of pA' is handled later.
603 : */
604 0 : new->cap_permitted.val =
605 0 : (new->cap_bset.val & caps->permitted.val) |
606 0 : (new->cap_inheritable.val & caps->inheritable.val);
607 :
608 0 : if (caps->permitted.val & ~new->cap_permitted.val)
609 : /* insufficient to execute correctly */
610 0 : ret = -EPERM;
611 :
612 : /*
613 : * For legacy apps, with no internal support for recognizing they
614 : * do not have enough capabilities, we return an error if they are
615 : * missing some "forced" (aka file-permitted) capabilities.
616 : */
617 0 : return *effective ? ret : 0;
618 : }
619 :
620 : /**
621 : * get_vfs_caps_from_disk - retrieve vfs caps from disk
622 : *
623 : * @idmap: idmap of the mount the inode was found from
624 : * @dentry: dentry from which @inode is retrieved
625 : * @cpu_caps: vfs capabilities
626 : *
627 : * Extract the on-exec-apply capability sets for an executable file.
628 : *
629 : * If the inode has been found through an idmapped mount the idmap of
630 : * the vfsmount must be passed through @idmap. This function will then
631 : * take care to map the inode according to @idmap before checking
632 : * permissions. On non-idmapped mounts or if permission checking is to be
633 : * performed on the raw inode simply passs @nop_mnt_idmap.
634 : */
635 0 : int get_vfs_caps_from_disk(struct mnt_idmap *idmap,
636 : const struct dentry *dentry,
637 : struct cpu_vfs_cap_data *cpu_caps)
638 : {
639 0 : struct inode *inode = d_backing_inode(dentry);
640 : __u32 magic_etc;
641 : int size;
642 0 : struct vfs_ns_cap_data data, *nscaps = &data;
643 0 : struct vfs_cap_data *caps = (struct vfs_cap_data *) &data;
644 : kuid_t rootkuid;
645 : vfsuid_t rootvfsuid;
646 : struct user_namespace *fs_ns;
647 :
648 0 : memset(cpu_caps, 0, sizeof(struct cpu_vfs_cap_data));
649 :
650 0 : if (!inode)
651 : return -ENODATA;
652 :
653 0 : fs_ns = inode->i_sb->s_user_ns;
654 0 : size = __vfs_getxattr((struct dentry *)dentry, inode,
655 : XATTR_NAME_CAPS, &data, XATTR_CAPS_SZ);
656 0 : if (size == -ENODATA || size == -EOPNOTSUPP)
657 : /* no data, that's ok */
658 : return -ENODATA;
659 :
660 0 : if (size < 0)
661 : return size;
662 :
663 0 : if (size < sizeof(magic_etc))
664 : return -EINVAL;
665 :
666 0 : cpu_caps->magic_etc = magic_etc = le32_to_cpu(caps->magic_etc);
667 :
668 0 : rootkuid = make_kuid(fs_ns, 0);
669 0 : switch (magic_etc & VFS_CAP_REVISION_MASK) {
670 : case VFS_CAP_REVISION_1:
671 0 : if (size != XATTR_CAPS_SZ_1)
672 : return -EINVAL;
673 : break;
674 : case VFS_CAP_REVISION_2:
675 0 : if (size != XATTR_CAPS_SZ_2)
676 : return -EINVAL;
677 : break;
678 : case VFS_CAP_REVISION_3:
679 0 : if (size != XATTR_CAPS_SZ_3)
680 : return -EINVAL;
681 0 : rootkuid = make_kuid(fs_ns, le32_to_cpu(nscaps->rootid));
682 : break;
683 :
684 : default:
685 : return -EINVAL;
686 : }
687 :
688 0 : rootvfsuid = make_vfsuid(idmap, fs_ns, rootkuid);
689 0 : if (!vfsuid_valid(rootvfsuid))
690 : return -ENODATA;
691 :
692 : /* Limit the caps to the mounter of the filesystem
693 : * or the more limited uid specified in the xattr.
694 : */
695 0 : if (!rootid_owns_currentns(rootvfsuid))
696 : return -ENODATA;
697 :
698 0 : cpu_caps->permitted.val = le32_to_cpu(caps->data[0].permitted);
699 0 : cpu_caps->inheritable.val = le32_to_cpu(caps->data[0].inheritable);
700 :
701 : /*
702 : * Rev1 had just a single 32-bit word, later expanded
703 : * to a second one for the high bits
704 : */
705 0 : if ((magic_etc & VFS_CAP_REVISION_MASK) != VFS_CAP_REVISION_1) {
706 0 : cpu_caps->permitted.val += (u64)le32_to_cpu(caps->data[1].permitted) << 32;
707 0 : cpu_caps->inheritable.val += (u64)le32_to_cpu(caps->data[1].inheritable) << 32;
708 : }
709 :
710 0 : cpu_caps->permitted.val &= CAP_VALID_MASK;
711 0 : cpu_caps->inheritable.val &= CAP_VALID_MASK;
712 :
713 0 : cpu_caps->rootid = vfsuid_into_kuid(rootvfsuid);
714 :
715 0 : return 0;
716 : }
717 :
718 : /*
719 : * Attempt to get the on-exec apply capability sets for an executable file from
720 : * its xattrs and, if present, apply them to the proposed credentials being
721 : * constructed by execve().
722 : */
723 0 : static int get_file_caps(struct linux_binprm *bprm, struct file *file,
724 : bool *effective, bool *has_fcap)
725 : {
726 0 : int rc = 0;
727 : struct cpu_vfs_cap_data vcaps;
728 :
729 0 : cap_clear(bprm->cred->cap_permitted);
730 :
731 0 : if (!file_caps_enabled)
732 : return 0;
733 :
734 0 : if (!mnt_may_suid(file->f_path.mnt))
735 : return 0;
736 :
737 : /*
738 : * This check is redundant with mnt_may_suid() but is kept to make
739 : * explicit that capability bits are limited to s_user_ns and its
740 : * descendants.
741 : */
742 0 : if (!current_in_userns(file->f_path.mnt->mnt_sb->s_user_ns))
743 : return 0;
744 :
745 0 : rc = get_vfs_caps_from_disk(file_mnt_idmap(file),
746 0 : file->f_path.dentry, &vcaps);
747 0 : if (rc < 0) {
748 0 : if (rc == -EINVAL)
749 0 : printk(KERN_NOTICE "Invalid argument reading file caps for %s\n",
750 : bprm->filename);
751 0 : else if (rc == -ENODATA)
752 0 : rc = 0;
753 : goto out;
754 : }
755 :
756 0 : rc = bprm_caps_from_vfs_caps(&vcaps, bprm, effective, has_fcap);
757 :
758 : out:
759 0 : if (rc)
760 0 : cap_clear(bprm->cred->cap_permitted);
761 :
762 : return rc;
763 : }
764 :
765 0 : static inline bool root_privileged(void) { return !issecure(SECURE_NOROOT); }
766 :
767 : static inline bool __is_real(kuid_t uid, struct cred *cred)
768 0 : { return uid_eq(cred->uid, uid); }
769 :
770 : static inline bool __is_eff(kuid_t uid, struct cred *cred)
771 0 : { return uid_eq(cred->euid, uid); }
772 :
773 : static inline bool __is_suid(kuid_t uid, struct cred *cred)
774 0 : { return !__is_real(uid, cred) && __is_eff(uid, cred); }
775 :
776 : /*
777 : * handle_privileged_root - Handle case of privileged root
778 : * @bprm: The execution parameters, including the proposed creds
779 : * @has_fcap: Are any file capabilities set?
780 : * @effective: Do we have effective root privilege?
781 : * @root_uid: This namespace' root UID WRT initial USER namespace
782 : *
783 : * Handle the case where root is privileged and hasn't been neutered by
784 : * SECURE_NOROOT. If file capabilities are set, they won't be combined with
785 : * set UID root and nothing is changed. If we are root, cap_permitted is
786 : * updated. If we have become set UID root, the effective bit is set.
787 : */
788 0 : static void handle_privileged_root(struct linux_binprm *bprm, bool has_fcap,
789 : bool *effective, kuid_t root_uid)
790 : {
791 0 : const struct cred *old = current_cred();
792 0 : struct cred *new = bprm->cred;
793 :
794 0 : if (!root_privileged())
795 : return;
796 : /*
797 : * If the legacy file capability is set, then don't set privs
798 : * for a setuid root binary run by a non-root user. Do set it
799 : * for a root user just to cause least surprise to an admin.
800 : */
801 0 : if (has_fcap && __is_suid(root_uid, new)) {
802 0 : warn_setuid_and_fcaps_mixed(bprm->filename);
803 : return;
804 : }
805 : /*
806 : * To support inheritance of root-permissions and suid-root
807 : * executables under compatibility mode, we override the
808 : * capability sets for the file.
809 : */
810 0 : if (__is_eff(root_uid, new) || __is_real(root_uid, new)) {
811 : /* pP' = (cap_bset & ~0) | (pI & ~0) */
812 0 : new->cap_permitted = cap_combine(old->cap_bset,
813 : old->cap_inheritable);
814 : }
815 : /*
816 : * If only the real uid is 0, we do not set the effective bit.
817 : */
818 0 : if (__is_eff(root_uid, new))
819 0 : *effective = true;
820 : }
821 :
822 : #define __cap_gained(field, target, source) \
823 : !cap_issubset(target->cap_##field, source->cap_##field)
824 : #define __cap_grew(target, source, cred) \
825 : !cap_issubset(cred->cap_##target, cred->cap_##source)
826 : #define __cap_full(field, cred) \
827 : cap_issubset(CAP_FULL_SET, cred->cap_##field)
828 :
829 : static inline bool __is_setuid(struct cred *new, const struct cred *old)
830 0 : { return !uid_eq(new->euid, old->uid); }
831 :
832 : static inline bool __is_setgid(struct cred *new, const struct cred *old)
833 0 : { return !gid_eq(new->egid, old->gid); }
834 :
835 : /*
836 : * 1) Audit candidate if current->cap_effective is set
837 : *
838 : * We do not bother to audit if 3 things are true:
839 : * 1) cap_effective has all caps
840 : * 2) we became root *OR* are were already root
841 : * 3) root is supposed to have all caps (SECURE_NOROOT)
842 : * Since this is just a normal root execing a process.
843 : *
844 : * Number 1 above might fail if you don't have a full bset, but I think
845 : * that is interesting information to audit.
846 : *
847 : * A number of other conditions require logging:
848 : * 2) something prevented setuid root getting all caps
849 : * 3) non-setuid root gets fcaps
850 : * 4) non-setuid root gets ambient
851 : */
852 0 : static inline bool nonroot_raised_pE(struct cred *new, const struct cred *old,
853 : kuid_t root, bool has_fcap)
854 : {
855 0 : bool ret = false;
856 :
857 0 : if ((__cap_grew(effective, ambient, new) &&
858 0 : !(__cap_full(effective, new) &&
859 0 : (__is_eff(root, new) || __is_real(root, new)) &&
860 0 : root_privileged())) ||
861 0 : (root_privileged() &&
862 0 : __is_suid(root, new) &&
863 0 : !__cap_full(effective, new)) ||
864 0 : (!__is_setuid(new, old) &&
865 0 : ((has_fcap &&
866 0 : __cap_gained(permitted, new, old)) ||
867 : __cap_gained(ambient, new, old))))
868 :
869 : ret = true;
870 :
871 0 : return ret;
872 : }
873 :
874 : /**
875 : * cap_bprm_creds_from_file - Set up the proposed credentials for execve().
876 : * @bprm: The execution parameters, including the proposed creds
877 : * @file: The file to pull the credentials from
878 : *
879 : * Set up the proposed credentials for a new execution context being
880 : * constructed by execve(). The proposed creds in @bprm->cred is altered,
881 : * which won't take effect immediately.
882 : *
883 : * Return: 0 if successful, -ve on error.
884 : */
885 0 : int cap_bprm_creds_from_file(struct linux_binprm *bprm, struct file *file)
886 : {
887 : /* Process setpcap binaries and capabilities for uid 0 */
888 0 : const struct cred *old = current_cred();
889 0 : struct cred *new = bprm->cred;
890 0 : bool effective = false, has_fcap = false, is_setid;
891 : int ret;
892 : kuid_t root_uid;
893 :
894 0 : if (WARN_ON(!cap_ambient_invariant_ok(old)))
895 : return -EPERM;
896 :
897 0 : ret = get_file_caps(bprm, file, &effective, &has_fcap);
898 0 : if (ret < 0)
899 : return ret;
900 :
901 0 : root_uid = make_kuid(new->user_ns, 0);
902 :
903 0 : handle_privileged_root(bprm, has_fcap, &effective, root_uid);
904 :
905 : /* if we have fs caps, clear dangerous personality flags */
906 0 : if (__cap_gained(permitted, new, old))
907 0 : bprm->per_clear |= PER_CLEAR_ON_SETID;
908 :
909 : /* Don't let someone trace a set[ug]id/setpcap binary with the revised
910 : * credentials unless they have the appropriate permit.
911 : *
912 : * In addition, if NO_NEW_PRIVS, then ensure we get no new privs.
913 : */
914 0 : is_setid = __is_setuid(new, old) || __is_setgid(new, old);
915 :
916 0 : if ((is_setid || __cap_gained(permitted, new, old)) &&
917 0 : ((bprm->unsafe & ~LSM_UNSAFE_PTRACE) ||
918 0 : !ptracer_capable(current, new->user_ns))) {
919 : /* downgrade; they get no more than they had, and maybe less */
920 0 : if (!ns_capable(new->user_ns, CAP_SETUID) ||
921 0 : (bprm->unsafe & LSM_UNSAFE_NO_NEW_PRIVS)) {
922 0 : new->euid = new->uid;
923 0 : new->egid = new->gid;
924 : }
925 0 : new->cap_permitted = cap_intersect(new->cap_permitted,
926 : old->cap_permitted);
927 : }
928 :
929 0 : new->suid = new->fsuid = new->euid;
930 0 : new->sgid = new->fsgid = new->egid;
931 :
932 : /* File caps or setid cancels ambient. */
933 0 : if (has_fcap || is_setid)
934 0 : cap_clear(new->cap_ambient);
935 :
936 : /*
937 : * Now that we've computed pA', update pP' to give:
938 : * pP' = (X & fP) | (pI & fI) | pA'
939 : */
940 0 : new->cap_permitted = cap_combine(new->cap_permitted, new->cap_ambient);
941 :
942 : /*
943 : * Set pE' = (fE ? pP' : pA'). Because pA' is zero if fE is set,
944 : * this is the same as pE' = (fE ? pP' : 0) | pA'.
945 : */
946 0 : if (effective)
947 0 : new->cap_effective = new->cap_permitted;
948 : else
949 0 : new->cap_effective = new->cap_ambient;
950 :
951 0 : if (WARN_ON(!cap_ambient_invariant_ok(new)))
952 : return -EPERM;
953 :
954 0 : if (nonroot_raised_pE(new, old, root_uid, has_fcap)) {
955 : ret = audit_log_bprm_fcaps(bprm, new, old);
956 : if (ret < 0)
957 : return ret;
958 : }
959 :
960 0 : new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS);
961 :
962 0 : if (WARN_ON(!cap_ambient_invariant_ok(new)))
963 : return -EPERM;
964 :
965 : /* Check for privilege-elevated exec. */
966 0 : if (is_setid ||
967 0 : (!__is_real(root_uid, new) &&
968 0 : (effective ||
969 : __cap_grew(permitted, ambient, new))))
970 0 : bprm->secureexec = 1;
971 :
972 : return 0;
973 : }
974 :
975 : /**
976 : * cap_inode_setxattr - Determine whether an xattr may be altered
977 : * @dentry: The inode/dentry being altered
978 : * @name: The name of the xattr to be changed
979 : * @value: The value that the xattr will be changed to
980 : * @size: The size of value
981 : * @flags: The replacement flag
982 : *
983 : * Determine whether an xattr may be altered or set on an inode, returning 0 if
984 : * permission is granted, -ve if denied.
985 : *
986 : * This is used to make sure security xattrs don't get updated or set by those
987 : * who aren't privileged to do so.
988 : */
989 0 : int cap_inode_setxattr(struct dentry *dentry, const char *name,
990 : const void *value, size_t size, int flags)
991 : {
992 0 : struct user_namespace *user_ns = dentry->d_sb->s_user_ns;
993 :
994 : /* Ignore non-security xattrs */
995 0 : if (strncmp(name, XATTR_SECURITY_PREFIX,
996 : XATTR_SECURITY_PREFIX_LEN) != 0)
997 : return 0;
998 :
999 : /*
1000 : * For XATTR_NAME_CAPS the check will be done in
1001 : * cap_convert_nscap(), called by setxattr()
1002 : */
1003 0 : if (strcmp(name, XATTR_NAME_CAPS) == 0)
1004 : return 0;
1005 :
1006 0 : if (!ns_capable(user_ns, CAP_SYS_ADMIN))
1007 : return -EPERM;
1008 0 : return 0;
1009 : }
1010 :
1011 : /**
1012 : * cap_inode_removexattr - Determine whether an xattr may be removed
1013 : *
1014 : * @idmap: idmap of the mount the inode was found from
1015 : * @dentry: The inode/dentry being altered
1016 : * @name: The name of the xattr to be changed
1017 : *
1018 : * Determine whether an xattr may be removed from an inode, returning 0 if
1019 : * permission is granted, -ve if denied.
1020 : *
1021 : * If the inode has been found through an idmapped mount the idmap of
1022 : * the vfsmount must be passed through @idmap. This function will then
1023 : * take care to map the inode according to @idmap before checking
1024 : * permissions. On non-idmapped mounts or if permission checking is to be
1025 : * performed on the raw inode simply pass @nop_mnt_idmap.
1026 : *
1027 : * This is used to make sure security xattrs don't get removed by those who
1028 : * aren't privileged to remove them.
1029 : */
1030 0 : int cap_inode_removexattr(struct mnt_idmap *idmap,
1031 : struct dentry *dentry, const char *name)
1032 : {
1033 0 : struct user_namespace *user_ns = dentry->d_sb->s_user_ns;
1034 :
1035 : /* Ignore non-security xattrs */
1036 0 : if (strncmp(name, XATTR_SECURITY_PREFIX,
1037 : XATTR_SECURITY_PREFIX_LEN) != 0)
1038 : return 0;
1039 :
1040 0 : if (strcmp(name, XATTR_NAME_CAPS) == 0) {
1041 : /* security.capability gets namespaced */
1042 0 : struct inode *inode = d_backing_inode(dentry);
1043 0 : if (!inode)
1044 : return -EINVAL;
1045 0 : if (!capable_wrt_inode_uidgid(idmap, inode, CAP_SETFCAP))
1046 : return -EPERM;
1047 0 : return 0;
1048 : }
1049 :
1050 0 : if (!ns_capable(user_ns, CAP_SYS_ADMIN))
1051 : return -EPERM;
1052 0 : return 0;
1053 : }
1054 :
1055 : /*
1056 : * cap_emulate_setxuid() fixes the effective / permitted capabilities of
1057 : * a process after a call to setuid, setreuid, or setresuid.
1058 : *
1059 : * 1) When set*uiding _from_ one of {r,e,s}uid == 0 _to_ all of
1060 : * {r,e,s}uid != 0, the permitted and effective capabilities are
1061 : * cleared.
1062 : *
1063 : * 2) When set*uiding _from_ euid == 0 _to_ euid != 0, the effective
1064 : * capabilities of the process are cleared.
1065 : *
1066 : * 3) When set*uiding _from_ euid != 0 _to_ euid == 0, the effective
1067 : * capabilities are set to the permitted capabilities.
1068 : *
1069 : * fsuid is handled elsewhere. fsuid == 0 and {r,e,s}uid!= 0 should
1070 : * never happen.
1071 : *
1072 : * -astor
1073 : *
1074 : * cevans - New behaviour, Oct '99
1075 : * A process may, via prctl(), elect to keep its capabilities when it
1076 : * calls setuid() and switches away from uid==0. Both permitted and
1077 : * effective sets will be retained.
1078 : * Without this change, it was impossible for a daemon to drop only some
1079 : * of its privilege. The call to setuid(!=0) would drop all privileges!
1080 : * Keeping uid 0 is not an option because uid 0 owns too many vital
1081 : * files..
1082 : * Thanks to Olaf Kirch and Peter Benie for spotting this.
1083 : */
1084 0 : static inline void cap_emulate_setxuid(struct cred *new, const struct cred *old)
1085 : {
1086 0 : kuid_t root_uid = make_kuid(old->user_ns, 0);
1087 :
1088 0 : if ((uid_eq(old->uid, root_uid) ||
1089 0 : uid_eq(old->euid, root_uid) ||
1090 0 : uid_eq(old->suid, root_uid)) &&
1091 0 : (!uid_eq(new->uid, root_uid) &&
1092 0 : !uid_eq(new->euid, root_uid) &&
1093 0 : !uid_eq(new->suid, root_uid))) {
1094 0 : if (!issecure(SECURE_KEEP_CAPS)) {
1095 0 : cap_clear(new->cap_permitted);
1096 0 : cap_clear(new->cap_effective);
1097 : }
1098 :
1099 : /*
1100 : * Pre-ambient programs expect setresuid to nonroot followed
1101 : * by exec to drop capabilities. We should make sure that
1102 : * this remains the case.
1103 : */
1104 0 : cap_clear(new->cap_ambient);
1105 : }
1106 0 : if (uid_eq(old->euid, root_uid) && !uid_eq(new->euid, root_uid))
1107 0 : cap_clear(new->cap_effective);
1108 0 : if (!uid_eq(old->euid, root_uid) && uid_eq(new->euid, root_uid))
1109 0 : new->cap_effective = new->cap_permitted;
1110 0 : }
1111 :
1112 : /**
1113 : * cap_task_fix_setuid - Fix up the results of setuid() call
1114 : * @new: The proposed credentials
1115 : * @old: The current task's current credentials
1116 : * @flags: Indications of what has changed
1117 : *
1118 : * Fix up the results of setuid() call before the credential changes are
1119 : * actually applied.
1120 : *
1121 : * Return: 0 to grant the changes, -ve to deny them.
1122 : */
1123 0 : int cap_task_fix_setuid(struct cred *new, const struct cred *old, int flags)
1124 : {
1125 0 : switch (flags) {
1126 : case LSM_SETID_RE:
1127 : case LSM_SETID_ID:
1128 : case LSM_SETID_RES:
1129 : /* juggle the capabilities to follow [RES]UID changes unless
1130 : * otherwise suppressed */
1131 0 : if (!issecure(SECURE_NO_SETUID_FIXUP))
1132 0 : cap_emulate_setxuid(new, old);
1133 : break;
1134 :
1135 : case LSM_SETID_FS:
1136 : /* juggle the capabilties to follow FSUID changes, unless
1137 : * otherwise suppressed
1138 : *
1139 : * FIXME - is fsuser used for all CAP_FS_MASK capabilities?
1140 : * if not, we might be a bit too harsh here.
1141 : */
1142 0 : if (!issecure(SECURE_NO_SETUID_FIXUP)) {
1143 0 : kuid_t root_uid = make_kuid(old->user_ns, 0);
1144 0 : if (uid_eq(old->fsuid, root_uid) && !uid_eq(new->fsuid, root_uid))
1145 0 : new->cap_effective =
1146 : cap_drop_fs_set(new->cap_effective);
1147 :
1148 0 : if (!uid_eq(old->fsuid, root_uid) && uid_eq(new->fsuid, root_uid))
1149 0 : new->cap_effective =
1150 : cap_raise_fs_set(new->cap_effective,
1151 : new->cap_permitted);
1152 : }
1153 : break;
1154 :
1155 : default:
1156 : return -EINVAL;
1157 : }
1158 :
1159 : return 0;
1160 : }
1161 :
1162 : /*
1163 : * Rationale: code calling task_setscheduler, task_setioprio, and
1164 : * task_setnice, assumes that
1165 : * . if capable(cap_sys_nice), then those actions should be allowed
1166 : * . if not capable(cap_sys_nice), but acting on your own processes,
1167 : * then those actions should be allowed
1168 : * This is insufficient now since you can call code without suid, but
1169 : * yet with increased caps.
1170 : * So we check for increased caps on the target process.
1171 : */
1172 0 : static int cap_safe_nice(struct task_struct *p)
1173 : {
1174 0 : int is_subset, ret = 0;
1175 :
1176 : rcu_read_lock();
1177 0 : is_subset = cap_issubset(__task_cred(p)->cap_permitted,
1178 0 : current_cred()->cap_permitted);
1179 0 : if (!is_subset && !ns_capable(__task_cred(p)->user_ns, CAP_SYS_NICE))
1180 0 : ret = -EPERM;
1181 : rcu_read_unlock();
1182 :
1183 0 : return ret;
1184 : }
1185 :
1186 : /**
1187 : * cap_task_setscheduler - Detemine if scheduler policy change is permitted
1188 : * @p: The task to affect
1189 : *
1190 : * Detemine if the requested scheduler policy change is permitted for the
1191 : * specified task.
1192 : *
1193 : * Return: 0 if permission is granted, -ve if denied.
1194 : */
1195 0 : int cap_task_setscheduler(struct task_struct *p)
1196 : {
1197 0 : return cap_safe_nice(p);
1198 : }
1199 :
1200 : /**
1201 : * cap_task_setioprio - Detemine if I/O priority change is permitted
1202 : * @p: The task to affect
1203 : * @ioprio: The I/O priority to set
1204 : *
1205 : * Detemine if the requested I/O priority change is permitted for the specified
1206 : * task.
1207 : *
1208 : * Return: 0 if permission is granted, -ve if denied.
1209 : */
1210 0 : int cap_task_setioprio(struct task_struct *p, int ioprio)
1211 : {
1212 0 : return cap_safe_nice(p);
1213 : }
1214 :
1215 : /**
1216 : * cap_task_setnice - Detemine if task priority change is permitted
1217 : * @p: The task to affect
1218 : * @nice: The nice value to set
1219 : *
1220 : * Detemine if the requested task priority change is permitted for the
1221 : * specified task.
1222 : *
1223 : * Return: 0 if permission is granted, -ve if denied.
1224 : */
1225 0 : int cap_task_setnice(struct task_struct *p, int nice)
1226 : {
1227 0 : return cap_safe_nice(p);
1228 : }
1229 :
1230 : /*
1231 : * Implement PR_CAPBSET_DROP. Attempt to remove the specified capability from
1232 : * the current task's bounding set. Returns 0 on success, -ve on error.
1233 : */
1234 0 : static int cap_prctl_drop(unsigned long cap)
1235 : {
1236 : struct cred *new;
1237 :
1238 0 : if (!ns_capable(current_user_ns(), CAP_SETPCAP))
1239 : return -EPERM;
1240 0 : if (!cap_valid(cap))
1241 : return -EINVAL;
1242 :
1243 0 : new = prepare_creds();
1244 0 : if (!new)
1245 : return -ENOMEM;
1246 0 : cap_lower(new->cap_bset, cap);
1247 0 : return commit_creds(new);
1248 : }
1249 :
1250 : /**
1251 : * cap_task_prctl - Implement process control functions for this security module
1252 : * @option: The process control function requested
1253 : * @arg2: The argument data for this function
1254 : * @arg3: The argument data for this function
1255 : * @arg4: The argument data for this function
1256 : * @arg5: The argument data for this function
1257 : *
1258 : * Allow process control functions (sys_prctl()) to alter capabilities; may
1259 : * also deny access to other functions not otherwise implemented here.
1260 : *
1261 : * Return: 0 or +ve on success, -ENOSYS if this function is not implemented
1262 : * here, other -ve on error. If -ENOSYS is returned, sys_prctl() and other LSM
1263 : * modules will consider performing the function.
1264 : */
1265 0 : int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3,
1266 : unsigned long arg4, unsigned long arg5)
1267 : {
1268 0 : const struct cred *old = current_cred();
1269 : struct cred *new;
1270 :
1271 0 : switch (option) {
1272 : case PR_CAPBSET_READ:
1273 0 : if (!cap_valid(arg2))
1274 : return -EINVAL;
1275 0 : return !!cap_raised(old->cap_bset, arg2);
1276 :
1277 : case PR_CAPBSET_DROP:
1278 0 : return cap_prctl_drop(arg2);
1279 :
1280 : /*
1281 : * The next four prctl's remain to assist with transitioning a
1282 : * system from legacy UID=0 based privilege (when filesystem
1283 : * capabilities are not in use) to a system using filesystem
1284 : * capabilities only - as the POSIX.1e draft intended.
1285 : *
1286 : * Note:
1287 : *
1288 : * PR_SET_SECUREBITS =
1289 : * issecure_mask(SECURE_KEEP_CAPS_LOCKED)
1290 : * | issecure_mask(SECURE_NOROOT)
1291 : * | issecure_mask(SECURE_NOROOT_LOCKED)
1292 : * | issecure_mask(SECURE_NO_SETUID_FIXUP)
1293 : * | issecure_mask(SECURE_NO_SETUID_FIXUP_LOCKED)
1294 : *
1295 : * will ensure that the current process and all of its
1296 : * children will be locked into a pure
1297 : * capability-based-privilege environment.
1298 : */
1299 : case PR_SET_SECUREBITS:
1300 0 : if ((((old->securebits & SECURE_ALL_LOCKS) >> 1)
1301 0 : & (old->securebits ^ arg2)) /*[1]*/
1302 0 : || ((old->securebits & SECURE_ALL_LOCKS & ~arg2)) /*[2]*/
1303 0 : || (arg2 & ~(SECURE_ALL_LOCKS | SECURE_ALL_BITS)) /*[3]*/
1304 0 : || (cap_capable(current_cred(),
1305 0 : current_cred()->user_ns,
1306 : CAP_SETPCAP,
1307 : CAP_OPT_NONE) != 0) /*[4]*/
1308 : /*
1309 : * [1] no changing of bits that are locked
1310 : * [2] no unlocking of locks
1311 : * [3] no setting of unsupported bits
1312 : * [4] doing anything requires privilege (go read about
1313 : * the "sendmail capabilities bug")
1314 : */
1315 : )
1316 : /* cannot change a locked bit */
1317 : return -EPERM;
1318 :
1319 0 : new = prepare_creds();
1320 0 : if (!new)
1321 : return -ENOMEM;
1322 0 : new->securebits = arg2;
1323 0 : return commit_creds(new);
1324 :
1325 : case PR_GET_SECUREBITS:
1326 0 : return old->securebits;
1327 :
1328 : case PR_GET_KEEPCAPS:
1329 0 : return !!issecure(SECURE_KEEP_CAPS);
1330 :
1331 : case PR_SET_KEEPCAPS:
1332 0 : if (arg2 > 1) /* Note, we rely on arg2 being unsigned here */
1333 : return -EINVAL;
1334 0 : if (issecure(SECURE_KEEP_CAPS_LOCKED))
1335 : return -EPERM;
1336 :
1337 0 : new = prepare_creds();
1338 0 : if (!new)
1339 : return -ENOMEM;
1340 0 : if (arg2)
1341 0 : new->securebits |= issecure_mask(SECURE_KEEP_CAPS);
1342 : else
1343 0 : new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS);
1344 0 : return commit_creds(new);
1345 :
1346 : case PR_CAP_AMBIENT:
1347 0 : if (arg2 == PR_CAP_AMBIENT_CLEAR_ALL) {
1348 0 : if (arg3 | arg4 | arg5)
1349 : return -EINVAL;
1350 :
1351 0 : new = prepare_creds();
1352 0 : if (!new)
1353 : return -ENOMEM;
1354 0 : cap_clear(new->cap_ambient);
1355 0 : return commit_creds(new);
1356 : }
1357 :
1358 0 : if (((!cap_valid(arg3)) | arg4 | arg5))
1359 : return -EINVAL;
1360 :
1361 0 : if (arg2 == PR_CAP_AMBIENT_IS_SET) {
1362 0 : return !!cap_raised(current_cred()->cap_ambient, arg3);
1363 0 : } else if (arg2 != PR_CAP_AMBIENT_RAISE &&
1364 : arg2 != PR_CAP_AMBIENT_LOWER) {
1365 : return -EINVAL;
1366 : } else {
1367 0 : if (arg2 == PR_CAP_AMBIENT_RAISE &&
1368 0 : (!cap_raised(current_cred()->cap_permitted, arg3) ||
1369 0 : !cap_raised(current_cred()->cap_inheritable,
1370 0 : arg3) ||
1371 0 : issecure(SECURE_NO_CAP_AMBIENT_RAISE)))
1372 : return -EPERM;
1373 :
1374 0 : new = prepare_creds();
1375 0 : if (!new)
1376 : return -ENOMEM;
1377 0 : if (arg2 == PR_CAP_AMBIENT_RAISE)
1378 0 : cap_raise(new->cap_ambient, arg3);
1379 : else
1380 0 : cap_lower(new->cap_ambient, arg3);
1381 0 : return commit_creds(new);
1382 : }
1383 :
1384 : default:
1385 : /* No functionality available - continue with default */
1386 : return -ENOSYS;
1387 : }
1388 : }
1389 :
1390 : /**
1391 : * cap_vm_enough_memory - Determine whether a new virtual mapping is permitted
1392 : * @mm: The VM space in which the new mapping is to be made
1393 : * @pages: The size of the mapping
1394 : *
1395 : * Determine whether the allocation of a new virtual mapping by the current
1396 : * task is permitted.
1397 : *
1398 : * Return: 1 if permission is granted, 0 if not.
1399 : */
1400 0 : int cap_vm_enough_memory(struct mm_struct *mm, long pages)
1401 : {
1402 0 : int cap_sys_admin = 0;
1403 :
1404 0 : if (cap_capable(current_cred(), &init_user_ns,
1405 : CAP_SYS_ADMIN, CAP_OPT_NOAUDIT) == 0)
1406 0 : cap_sys_admin = 1;
1407 :
1408 0 : return cap_sys_admin;
1409 : }
1410 :
1411 : /**
1412 : * cap_mmap_addr - check if able to map given addr
1413 : * @addr: address attempting to be mapped
1414 : *
1415 : * If the process is attempting to map memory below dac_mmap_min_addr they need
1416 : * CAP_SYS_RAWIO. The other parameters to this function are unused by the
1417 : * capability security module.
1418 : *
1419 : * Return: 0 if this mapping should be allowed or -EPERM if not.
1420 : */
1421 0 : int cap_mmap_addr(unsigned long addr)
1422 : {
1423 0 : int ret = 0;
1424 :
1425 0 : if (addr < dac_mmap_min_addr) {
1426 0 : ret = cap_capable(current_cred(), &init_user_ns, CAP_SYS_RAWIO,
1427 : CAP_OPT_NONE);
1428 : /* set PF_SUPERPRIV if it turns out we allow the low mmap */
1429 0 : if (ret == 0)
1430 0 : current->flags |= PF_SUPERPRIV;
1431 : }
1432 0 : return ret;
1433 : }
1434 :
1435 0 : int cap_mmap_file(struct file *file, unsigned long reqprot,
1436 : unsigned long prot, unsigned long flags)
1437 : {
1438 0 : return 0;
1439 : }
1440 :
1441 : #ifdef CONFIG_SECURITY
1442 :
1443 : static struct security_hook_list capability_hooks[] __lsm_ro_after_init = {
1444 : LSM_HOOK_INIT(capable, cap_capable),
1445 : LSM_HOOK_INIT(settime, cap_settime),
1446 : LSM_HOOK_INIT(ptrace_access_check, cap_ptrace_access_check),
1447 : LSM_HOOK_INIT(ptrace_traceme, cap_ptrace_traceme),
1448 : LSM_HOOK_INIT(capget, cap_capget),
1449 : LSM_HOOK_INIT(capset, cap_capset),
1450 : LSM_HOOK_INIT(bprm_creds_from_file, cap_bprm_creds_from_file),
1451 : LSM_HOOK_INIT(inode_need_killpriv, cap_inode_need_killpriv),
1452 : LSM_HOOK_INIT(inode_killpriv, cap_inode_killpriv),
1453 : LSM_HOOK_INIT(inode_getsecurity, cap_inode_getsecurity),
1454 : LSM_HOOK_INIT(mmap_addr, cap_mmap_addr),
1455 : LSM_HOOK_INIT(mmap_file, cap_mmap_file),
1456 : LSM_HOOK_INIT(task_fix_setuid, cap_task_fix_setuid),
1457 : LSM_HOOK_INIT(task_prctl, cap_task_prctl),
1458 : LSM_HOOK_INIT(task_setscheduler, cap_task_setscheduler),
1459 : LSM_HOOK_INIT(task_setioprio, cap_task_setioprio),
1460 : LSM_HOOK_INIT(task_setnice, cap_task_setnice),
1461 : LSM_HOOK_INIT(vm_enough_memory, cap_vm_enough_memory),
1462 : };
1463 :
1464 : static int __init capability_init(void)
1465 : {
1466 : security_add_hooks(capability_hooks, ARRAY_SIZE(capability_hooks),
1467 : "capability");
1468 : return 0;
1469 : }
1470 :
1471 : DEFINE_LSM(capability) = {
1472 : .name = "capability",
1473 : .order = LSM_ORDER_FIRST,
1474 : .init = capability_init,
1475 : };
1476 :
1477 : #endif /* CONFIG_SECURITY */
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