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1/* Common capabilities, needed by capability.o.
2 *
3 * This program is free software; you can redistribute it and/or modify
4 * it under the terms of the GNU General Public License as published by
5 * the Free Software Foundation; either version 2 of the License, or
6 * (at your option) any later version.
7 *
8 */
9
10#include <linux/capability.h>
11#include <linux/audit.h>
12#include <linux/module.h>
13#include <linux/init.h>
14#include <linux/kernel.h>
15#include <linux/security.h>
16#include <linux/file.h>
17#include <linux/mm.h>
18#include <linux/mman.h>
19#include <linux/pagemap.h>
20#include <linux/swap.h>
21#include <linux/skbuff.h>
22#include <linux/netlink.h>
23#include <linux/ptrace.h>
24#include <linux/xattr.h>
25#include <linux/hugetlb.h>
26#include <linux/mount.h>
27#include <linux/sched.h>
28#include <linux/prctl.h>
29#include <linux/securebits.h>
30#include <linux/user_namespace.h>
31#include <linux/binfmts.h>
32#include <linux/personality.h>
33
34/*
35 * If a non-root user executes a setuid-root binary in
36 * !secure(SECURE_NOROOT) mode, then we raise capabilities.
37 * However if fE is also set, then the intent is for only
38 * the file capabilities to be applied, and the setuid-root
39 * bit is left on either to change the uid (plausible) or
40 * to get full privilege on a kernel without file capabilities
41 * support. So in that case we do not raise capabilities.
42 *
43 * Warn if that happens, once per boot.
44 */
45static void warn_setuid_and_fcaps_mixed(const char *fname)
46{
47 static int warned;
48 if (!warned) {
49 printk(KERN_INFO "warning: `%s' has both setuid-root and"
50 " effective capabilities. Therefore not raising all"
51 " capabilities.\n", fname);
52 warned = 1;
53 }
54}
55
56int cap_netlink_send(struct sock *sk, struct sk_buff *skb)
57{
58 return 0;
59}
60
61/**
62 * cap_capable - Determine whether a task has a particular effective capability
63 * @cred: The credentials to use
64 * @ns: The user namespace in which we need the capability
65 * @cap: The capability to check for
66 * @audit: Whether to write an audit message or not
67 *
68 * Determine whether the nominated task has the specified capability amongst
69 * its effective set, returning 0 if it does, -ve if it does not.
70 *
71 * NOTE WELL: cap_has_capability() cannot be used like the kernel's capable()
72 * and has_capability() functions. That is, it has the reverse semantics:
73 * cap_has_capability() returns 0 when a task has a capability, but the
74 * kernel's capable() and has_capability() returns 1 for this case.
75 */
76int cap_capable(const struct cred *cred, struct user_namespace *targ_ns,
77 int cap, int audit)
78{
79 struct user_namespace *ns = targ_ns;
80
81 /* See if cred has the capability in the target user namespace
82 * by examining the target user namespace and all of the target
83 * user namespace's parents.
84 */
85 for (;;) {
86 /* Do we have the necessary capabilities? */
87 if (ns == cred->user_ns)
88 return cap_raised(cred->cap_effective, cap) ? 0 : -EPERM;
89
90 /* Have we tried all of the parent namespaces? */
91 if (ns == &init_user_ns)
92 return -EPERM;
93
94 /*
95 * The owner of the user namespace in the parent of the
96 * user namespace has all caps.
97 */
98 if ((ns->parent == cred->user_ns) && uid_eq(ns->owner, cred->euid))
99 return 0;
100
101 /*
102 * If you have a capability in a parent user ns, then you have
103 * it over all children user namespaces as well.
104 */
105 ns = ns->parent;
106 }
107
108 /* We never get here */
109}
110
111/**
112 * cap_settime - Determine whether the current process may set the system clock
113 * @ts: The time to set
114 * @tz: The timezone to set
115 *
116 * Determine whether the current process may set the system clock and timezone
117 * information, returning 0 if permission granted, -ve if denied.
118 */
119int cap_settime(const struct timespec *ts, const struct timezone *tz)
120{
121 if (!capable(CAP_SYS_TIME))
122 return -EPERM;
123 return 0;
124}
125
126/**
127 * cap_ptrace_access_check - Determine whether the current process may access
128 * another
129 * @child: The process to be accessed
130 * @mode: The mode of attachment.
131 *
132 * If we are in the same or an ancestor user_ns and have all the target
133 * task's capabilities, then ptrace access is allowed.
134 * If we have the ptrace capability to the target user_ns, then ptrace
135 * access is allowed.
136 * Else denied.
137 *
138 * Determine whether a process may access another, returning 0 if permission
139 * granted, -ve if denied.
140 */
141int cap_ptrace_access_check(struct task_struct *child, unsigned int mode)
142{
143 int ret = 0;
144 const struct cred *cred, *child_cred;
145
146 rcu_read_lock();
147 cred = current_cred();
148 child_cred = __task_cred(child);
149 if (cred->user_ns == child_cred->user_ns &&
150 cap_issubset(child_cred->cap_permitted, cred->cap_permitted))
151 goto out;
152 if (ns_capable(child_cred->user_ns, CAP_SYS_PTRACE))
153 goto out;
154 ret = -EPERM;
155out:
156 rcu_read_unlock();
157 return ret;
158}
159
160/**
161 * cap_ptrace_traceme - Determine whether another process may trace the current
162 * @parent: The task proposed to be the tracer
163 *
164 * If parent is in the same or an ancestor user_ns and has all current's
165 * capabilities, then ptrace access is allowed.
166 * If parent has the ptrace capability to current's user_ns, then ptrace
167 * access is allowed.
168 * Else denied.
169 *
170 * Determine whether the nominated task is permitted to trace the current
171 * process, returning 0 if permission is granted, -ve if denied.
172 */
173int cap_ptrace_traceme(struct task_struct *parent)
174{
175 int ret = 0;
176 const struct cred *cred, *child_cred;
177
178 rcu_read_lock();
179 cred = __task_cred(parent);
180 child_cred = current_cred();
181 if (cred->user_ns == child_cred->user_ns &&
182 cap_issubset(child_cred->cap_permitted, cred->cap_permitted))
183 goto out;
184 if (has_ns_capability(parent, child_cred->user_ns, CAP_SYS_PTRACE))
185 goto out;
186 ret = -EPERM;
187out:
188 rcu_read_unlock();
189 return ret;
190}
191
192/**
193 * cap_capget - Retrieve a task's capability sets
194 * @target: The task from which to retrieve the capability sets
195 * @effective: The place to record the effective set
196 * @inheritable: The place to record the inheritable set
197 * @permitted: The place to record the permitted set
198 *
199 * This function retrieves the capabilities of the nominated task and returns
200 * them to the caller.
201 */
202int cap_capget(struct task_struct *target, kernel_cap_t *effective,
203 kernel_cap_t *inheritable, kernel_cap_t *permitted)
204{
205 const struct cred *cred;
206
207 /* Derived from kernel/capability.c:sys_capget. */
208 rcu_read_lock();
209 cred = __task_cred(target);
210 *effective = cred->cap_effective;
211 *inheritable = cred->cap_inheritable;
212 *permitted = cred->cap_permitted;
213 rcu_read_unlock();
214 return 0;
215}
216
217/*
218 * Determine whether the inheritable capabilities are limited to the old
219 * permitted set. Returns 1 if they are limited, 0 if they are not.
220 */
221static inline int cap_inh_is_capped(void)
222{
223
224 /* they are so limited unless the current task has the CAP_SETPCAP
225 * capability
226 */
227 if (cap_capable(current_cred(), current_cred()->user_ns,
228 CAP_SETPCAP, SECURITY_CAP_AUDIT) == 0)
229 return 0;
230 return 1;
231}
232
233/**
234 * cap_capset - Validate and apply proposed changes to current's capabilities
235 * @new: The proposed new credentials; alterations should be made here
236 * @old: The current task's current credentials
237 * @effective: A pointer to the proposed new effective capabilities set
238 * @inheritable: A pointer to the proposed new inheritable capabilities set
239 * @permitted: A pointer to the proposed new permitted capabilities set
240 *
241 * This function validates and applies a proposed mass change to the current
242 * process's capability sets. The changes are made to the proposed new
243 * credentials, and assuming no error, will be committed by the caller of LSM.
244 */
245int cap_capset(struct cred *new,
246 const struct cred *old,
247 const kernel_cap_t *effective,
248 const kernel_cap_t *inheritable,
249 const kernel_cap_t *permitted)
250{
251 if (cap_inh_is_capped() &&
252 !cap_issubset(*inheritable,
253 cap_combine(old->cap_inheritable,
254 old->cap_permitted)))
255 /* incapable of using this inheritable set */
256 return -EPERM;
257
258 if (!cap_issubset(*inheritable,
259 cap_combine(old->cap_inheritable,
260 old->cap_bset)))
261 /* no new pI capabilities outside bounding set */
262 return -EPERM;
263
264 /* verify restrictions on target's new Permitted set */
265 if (!cap_issubset(*permitted, old->cap_permitted))
266 return -EPERM;
267
268 /* verify the _new_Effective_ is a subset of the _new_Permitted_ */
269 if (!cap_issubset(*effective, *permitted))
270 return -EPERM;
271
272 new->cap_effective = *effective;
273 new->cap_inheritable = *inheritable;
274 new->cap_permitted = *permitted;
275 return 0;
276}
277
278/*
279 * Clear proposed capability sets for execve().
280 */
281static inline void bprm_clear_caps(struct linux_binprm *bprm)
282{
283 cap_clear(bprm->cred->cap_permitted);
284 bprm->cap_effective = false;
285}
286
287/**
288 * cap_inode_need_killpriv - Determine if inode change affects privileges
289 * @dentry: The inode/dentry in being changed with change marked ATTR_KILL_PRIV
290 *
291 * Determine if an inode having a change applied that's marked ATTR_KILL_PRIV
292 * affects the security markings on that inode, and if it is, should
293 * inode_killpriv() be invoked or the change rejected?
294 *
295 * Returns 0 if granted; +ve if granted, but inode_killpriv() is required; and
296 * -ve to deny the change.
297 */
298int cap_inode_need_killpriv(struct dentry *dentry)
299{
300 struct inode *inode = dentry->d_inode;
301 int error;
302
303 if (!inode->i_op->getxattr)
304 return 0;
305
306 error = inode->i_op->getxattr(dentry, XATTR_NAME_CAPS, NULL, 0);
307 if (error <= 0)
308 return 0;
309 return 1;
310}
311
312/**
313 * cap_inode_killpriv - Erase the security markings on an inode
314 * @dentry: The inode/dentry to alter
315 *
316 * Erase the privilege-enhancing security markings on an inode.
317 *
318 * Returns 0 if successful, -ve on error.
319 */
320int cap_inode_killpriv(struct dentry *dentry)
321{
322 struct inode *inode = dentry->d_inode;
323
324 if (!inode->i_op->removexattr)
325 return 0;
326
327 return inode->i_op->removexattr(dentry, XATTR_NAME_CAPS);
328}
329
330/*
331 * Calculate the new process capability sets from the capability sets attached
332 * to a file.
333 */
334static inline int bprm_caps_from_vfs_caps(struct cpu_vfs_cap_data *caps,
335 struct linux_binprm *bprm,
336 bool *effective,
337 bool *has_cap)
338{
339 struct cred *new = bprm->cred;
340 unsigned i;
341 int ret = 0;
342
343 if (caps->magic_etc & VFS_CAP_FLAGS_EFFECTIVE)
344 *effective = true;
345
346 if (caps->magic_etc & VFS_CAP_REVISION_MASK)
347 *has_cap = true;
348
349 CAP_FOR_EACH_U32(i) {
350 __u32 permitted = caps->permitted.cap[i];
351 __u32 inheritable = caps->inheritable.cap[i];
352
353 /*
354 * pP' = (X & fP) | (pI & fI)
355 */
356 new->cap_permitted.cap[i] =
357 (new->cap_bset.cap[i] & permitted) |
358 (new->cap_inheritable.cap[i] & inheritable);
359
360 if (permitted & ~new->cap_permitted.cap[i])
361 /* insufficient to execute correctly */
362 ret = -EPERM;
363 }
364
365 /*
366 * For legacy apps, with no internal support for recognizing they
367 * do not have enough capabilities, we return an error if they are
368 * missing some "forced" (aka file-permitted) capabilities.
369 */
370 return *effective ? ret : 0;
371}
372
373/*
374 * Extract the on-exec-apply capability sets for an executable file.
375 */
376int get_vfs_caps_from_disk(const struct dentry *dentry, struct cpu_vfs_cap_data *cpu_caps)
377{
378 struct inode *inode = dentry->d_inode;
379 __u32 magic_etc;
380 unsigned tocopy, i;
381 int size;
382 struct vfs_cap_data caps;
383
384 memset(cpu_caps, 0, sizeof(struct cpu_vfs_cap_data));
385
386 if (!inode || !inode->i_op->getxattr)
387 return -ENODATA;
388
389 size = inode->i_op->getxattr((struct dentry *)dentry, XATTR_NAME_CAPS, &caps,
390 XATTR_CAPS_SZ);
391 if (size == -ENODATA || size == -EOPNOTSUPP)
392 /* no data, that's ok */
393 return -ENODATA;
394 if (size < 0)
395 return size;
396
397 if (size < sizeof(magic_etc))
398 return -EINVAL;
399
400 cpu_caps->magic_etc = magic_etc = le32_to_cpu(caps.magic_etc);
401
402 switch (magic_etc & VFS_CAP_REVISION_MASK) {
403 case VFS_CAP_REVISION_1:
404 if (size != XATTR_CAPS_SZ_1)
405 return -EINVAL;
406 tocopy = VFS_CAP_U32_1;
407 break;
408 case VFS_CAP_REVISION_2:
409 if (size != XATTR_CAPS_SZ_2)
410 return -EINVAL;
411 tocopy = VFS_CAP_U32_2;
412 break;
413 default:
414 return -EINVAL;
415 }
416
417 CAP_FOR_EACH_U32(i) {
418 if (i >= tocopy)
419 break;
420 cpu_caps->permitted.cap[i] = le32_to_cpu(caps.data[i].permitted);
421 cpu_caps->inheritable.cap[i] = le32_to_cpu(caps.data[i].inheritable);
422 }
423
424 return 0;
425}
426
427/*
428 * Attempt to get the on-exec apply capability sets for an executable file from
429 * its xattrs and, if present, apply them to the proposed credentials being
430 * constructed by execve().
431 */
432static int get_file_caps(struct linux_binprm *bprm, bool *effective, bool *has_cap)
433{
434 struct dentry *dentry;
435 int rc = 0;
436 struct cpu_vfs_cap_data vcaps;
437
438 bprm_clear_caps(bprm);
439
440 if (!file_caps_enabled)
441 return 0;
442
443 if (bprm->file->f_path.mnt->mnt_flags & MNT_NOSUID)
444 return 0;
445
446 dentry = dget(bprm->file->f_dentry);
447
448 rc = get_vfs_caps_from_disk(dentry, &vcaps);
449 if (rc < 0) {
450 if (rc == -EINVAL)
451 printk(KERN_NOTICE "%s: get_vfs_caps_from_disk returned %d for %s\n",
452 __func__, rc, bprm->filename);
453 else if (rc == -ENODATA)
454 rc = 0;
455 goto out;
456 }
457
458 rc = bprm_caps_from_vfs_caps(&vcaps, bprm, effective, has_cap);
459 if (rc == -EINVAL)
460 printk(KERN_NOTICE "%s: cap_from_disk returned %d for %s\n",
461 __func__, rc, bprm->filename);
462
463out:
464 dput(dentry);
465 if (rc)
466 bprm_clear_caps(bprm);
467
468 return rc;
469}
470
471/**
472 * cap_bprm_set_creds - Set up the proposed credentials for execve().
473 * @bprm: The execution parameters, including the proposed creds
474 *
475 * Set up the proposed credentials for a new execution context being
476 * constructed by execve(). The proposed creds in @bprm->cred is altered,
477 * which won't take effect immediately. Returns 0 if successful, -ve on error.
478 */
479int cap_bprm_set_creds(struct linux_binprm *bprm)
480{
481 const struct cred *old = current_cred();
482 struct cred *new = bprm->cred;
483 bool effective, has_cap = false;
484 int ret;
485 kuid_t root_uid;
486
487 effective = false;
488 ret = get_file_caps(bprm, &effective, &has_cap);
489 if (ret < 0)
490 return ret;
491
492 root_uid = make_kuid(new->user_ns, 0);
493
494 if (!issecure(SECURE_NOROOT)) {
495 /*
496 * If the legacy file capability is set, then don't set privs
497 * for a setuid root binary run by a non-root user. Do set it
498 * for a root user just to cause least surprise to an admin.
499 */
500 if (has_cap && !uid_eq(new->uid, root_uid) && uid_eq(new->euid, root_uid)) {
501 warn_setuid_and_fcaps_mixed(bprm->filename);
502 goto skip;
503 }
504 /*
505 * To support inheritance of root-permissions and suid-root
506 * executables under compatibility mode, we override the
507 * capability sets for the file.
508 *
509 * If only the real uid is 0, we do not set the effective bit.
510 */
511 if (uid_eq(new->euid, root_uid) || uid_eq(new->uid, root_uid)) {
512 /* pP' = (cap_bset & ~0) | (pI & ~0) */
513 new->cap_permitted = cap_combine(old->cap_bset,
514 old->cap_inheritable);
515 }
516 if (uid_eq(new->euid, root_uid))
517 effective = true;
518 }
519skip:
520
521 /* if we have fs caps, clear dangerous personality flags */
522 if (!cap_issubset(new->cap_permitted, old->cap_permitted))
523 bprm->per_clear |= PER_CLEAR_ON_SETID;
524
525
526 /* Don't let someone trace a set[ug]id/setpcap binary with the revised
527 * credentials unless they have the appropriate permit.
528 *
529 * In addition, if NO_NEW_PRIVS, then ensure we get no new privs.
530 */
531 if ((!uid_eq(new->euid, old->uid) ||
532 !gid_eq(new->egid, old->gid) ||
533 !cap_issubset(new->cap_permitted, old->cap_permitted)) &&
534 bprm->unsafe & ~LSM_UNSAFE_PTRACE_CAP) {
535 /* downgrade; they get no more than they had, and maybe less */
536 if (!capable(CAP_SETUID) ||
537 (bprm->unsafe & LSM_UNSAFE_NO_NEW_PRIVS)) {
538 new->euid = new->uid;
539 new->egid = new->gid;
540 }
541 new->cap_permitted = cap_intersect(new->cap_permitted,
542 old->cap_permitted);
543 }
544
545 new->suid = new->fsuid = new->euid;
546 new->sgid = new->fsgid = new->egid;
547
548 if (effective)
549 new->cap_effective = new->cap_permitted;
550 else
551 cap_clear(new->cap_effective);
552 bprm->cap_effective = effective;
553
554 /*
555 * Audit candidate if current->cap_effective is set
556 *
557 * We do not bother to audit if 3 things are true:
558 * 1) cap_effective has all caps
559 * 2) we are root
560 * 3) root is supposed to have all caps (SECURE_NOROOT)
561 * Since this is just a normal root execing a process.
562 *
563 * Number 1 above might fail if you don't have a full bset, but I think
564 * that is interesting information to audit.
565 */
566 if (!cap_isclear(new->cap_effective)) {
567 if (!cap_issubset(CAP_FULL_SET, new->cap_effective) ||
568 !uid_eq(new->euid, root_uid) || !uid_eq(new->uid, root_uid) ||
569 issecure(SECURE_NOROOT)) {
570 ret = audit_log_bprm_fcaps(bprm, new, old);
571 if (ret < 0)
572 return ret;
573 }
574 }
575
576 new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS);
577 return 0;
578}
579
580/**
581 * cap_bprm_secureexec - Determine whether a secure execution is required
582 * @bprm: The execution parameters
583 *
584 * Determine whether a secure execution is required, return 1 if it is, and 0
585 * if it is not.
586 *
587 * The credentials have been committed by this point, and so are no longer
588 * available through @bprm->cred.
589 */
590int cap_bprm_secureexec(struct linux_binprm *bprm)
591{
592 const struct cred *cred = current_cred();
593 kuid_t root_uid = make_kuid(cred->user_ns, 0);
594
595 if (!uid_eq(cred->uid, root_uid)) {
596 if (bprm->cap_effective)
597 return 1;
598 if (!cap_isclear(cred->cap_permitted))
599 return 1;
600 }
601
602 return (!uid_eq(cred->euid, cred->uid) ||
603 !gid_eq(cred->egid, cred->gid));
604}
605
606/**
607 * cap_inode_setxattr - Determine whether an xattr may be altered
608 * @dentry: The inode/dentry being altered
609 * @name: The name of the xattr to be changed
610 * @value: The value that the xattr will be changed to
611 * @size: The size of value
612 * @flags: The replacement flag
613 *
614 * Determine whether an xattr may be altered or set on an inode, returning 0 if
615 * permission is granted, -ve if denied.
616 *
617 * This is used to make sure security xattrs don't get updated or set by those
618 * who aren't privileged to do so.
619 */
620int cap_inode_setxattr(struct dentry *dentry, const char *name,
621 const void *value, size_t size, int flags)
622{
623 if (!strcmp(name, XATTR_NAME_CAPS)) {
624 if (!capable(CAP_SETFCAP))
625 return -EPERM;
626 return 0;
627 }
628
629 if (!strncmp(name, XATTR_SECURITY_PREFIX,
630 sizeof(XATTR_SECURITY_PREFIX) - 1) &&
631 !capable(CAP_SYS_ADMIN))
632 return -EPERM;
633 return 0;
634}
635
636/**
637 * cap_inode_removexattr - Determine whether an xattr may be removed
638 * @dentry: The inode/dentry being altered
639 * @name: The name of the xattr to be changed
640 *
641 * Determine whether an xattr may be removed from an inode, returning 0 if
642 * permission is granted, -ve if denied.
643 *
644 * This is used to make sure security xattrs don't get removed by those who
645 * aren't privileged to remove them.
646 */
647int cap_inode_removexattr(struct dentry *dentry, const char *name)
648{
649 if (!strcmp(name, XATTR_NAME_CAPS)) {
650 if (!capable(CAP_SETFCAP))
651 return -EPERM;
652 return 0;
653 }
654
655 if (!strncmp(name, XATTR_SECURITY_PREFIX,
656 sizeof(XATTR_SECURITY_PREFIX) - 1) &&
657 !capable(CAP_SYS_ADMIN))
658 return -EPERM;
659 return 0;
660}
661
662/*
663 * cap_emulate_setxuid() fixes the effective / permitted capabilities of
664 * a process after a call to setuid, setreuid, or setresuid.
665 *
666 * 1) When set*uiding _from_ one of {r,e,s}uid == 0 _to_ all of
667 * {r,e,s}uid != 0, the permitted and effective capabilities are
668 * cleared.
669 *
670 * 2) When set*uiding _from_ euid == 0 _to_ euid != 0, the effective
671 * capabilities of the process are cleared.
672 *
673 * 3) When set*uiding _from_ euid != 0 _to_ euid == 0, the effective
674 * capabilities are set to the permitted capabilities.
675 *
676 * fsuid is handled elsewhere. fsuid == 0 and {r,e,s}uid!= 0 should
677 * never happen.
678 *
679 * -astor
680 *
681 * cevans - New behaviour, Oct '99
682 * A process may, via prctl(), elect to keep its capabilities when it
683 * calls setuid() and switches away from uid==0. Both permitted and
684 * effective sets will be retained.
685 * Without this change, it was impossible for a daemon to drop only some
686 * of its privilege. The call to setuid(!=0) would drop all privileges!
687 * Keeping uid 0 is not an option because uid 0 owns too many vital
688 * files..
689 * Thanks to Olaf Kirch and Peter Benie for spotting this.
690 */
691static inline void cap_emulate_setxuid(struct cred *new, const struct cred *old)
692{
693 kuid_t root_uid = make_kuid(old->user_ns, 0);
694
695 if ((uid_eq(old->uid, root_uid) ||
696 uid_eq(old->euid, root_uid) ||
697 uid_eq(old->suid, root_uid)) &&
698 (!uid_eq(new->uid, root_uid) &&
699 !uid_eq(new->euid, root_uid) &&
700 !uid_eq(new->suid, root_uid)) &&
701 !issecure(SECURE_KEEP_CAPS)) {
702 cap_clear(new->cap_permitted);
703 cap_clear(new->cap_effective);
704 }
705 if (uid_eq(old->euid, root_uid) && !uid_eq(new->euid, root_uid))
706 cap_clear(new->cap_effective);
707 if (!uid_eq(old->euid, root_uid) && uid_eq(new->euid, root_uid))
708 new->cap_effective = new->cap_permitted;
709}
710
711/**
712 * cap_task_fix_setuid - Fix up the results of setuid() call
713 * @new: The proposed credentials
714 * @old: The current task's current credentials
715 * @flags: Indications of what has changed
716 *
717 * Fix up the results of setuid() call before the credential changes are
718 * actually applied, returning 0 to grant the changes, -ve to deny them.
719 */
720int cap_task_fix_setuid(struct cred *new, const struct cred *old, int flags)
721{
722 switch (flags) {
723 case LSM_SETID_RE:
724 case LSM_SETID_ID:
725 case LSM_SETID_RES:
726 /* juggle the capabilities to follow [RES]UID changes unless
727 * otherwise suppressed */
728 if (!issecure(SECURE_NO_SETUID_FIXUP))
729 cap_emulate_setxuid(new, old);
730 break;
731
732 case LSM_SETID_FS:
733 /* juggle the capabilties to follow FSUID changes, unless
734 * otherwise suppressed
735 *
736 * FIXME - is fsuser used for all CAP_FS_MASK capabilities?
737 * if not, we might be a bit too harsh here.
738 */
739 if (!issecure(SECURE_NO_SETUID_FIXUP)) {
740 kuid_t root_uid = make_kuid(old->user_ns, 0);
741 if (uid_eq(old->fsuid, root_uid) && !uid_eq(new->fsuid, root_uid))
742 new->cap_effective =
743 cap_drop_fs_set(new->cap_effective);
744
745 if (!uid_eq(old->fsuid, root_uid) && uid_eq(new->fsuid, root_uid))
746 new->cap_effective =
747 cap_raise_fs_set(new->cap_effective,
748 new->cap_permitted);
749 }
750 break;
751
752 default:
753 return -EINVAL;
754 }
755
756 return 0;
757}
758
759/*
760 * Rationale: code calling task_setscheduler, task_setioprio, and
761 * task_setnice, assumes that
762 * . if capable(cap_sys_nice), then those actions should be allowed
763 * . if not capable(cap_sys_nice), but acting on your own processes,
764 * then those actions should be allowed
765 * This is insufficient now since you can call code without suid, but
766 * yet with increased caps.
767 * So we check for increased caps on the target process.
768 */
769static int cap_safe_nice(struct task_struct *p)
770{
771 int is_subset, ret = 0;
772
773 rcu_read_lock();
774 is_subset = cap_issubset(__task_cred(p)->cap_permitted,
775 current_cred()->cap_permitted);
776 if (!is_subset && !ns_capable(__task_cred(p)->user_ns, CAP_SYS_NICE))
777 ret = -EPERM;
778 rcu_read_unlock();
779
780 return ret;
781}
782
783/**
784 * cap_task_setscheduler - Detemine if scheduler policy change is permitted
785 * @p: The task to affect
786 *
787 * Detemine if the requested scheduler policy change is permitted for the
788 * specified task, returning 0 if permission is granted, -ve if denied.
789 */
790int cap_task_setscheduler(struct task_struct *p)
791{
792 return cap_safe_nice(p);
793}
794
795/**
796 * cap_task_ioprio - Detemine if I/O priority change is permitted
797 * @p: The task to affect
798 * @ioprio: The I/O priority to set
799 *
800 * Detemine if the requested I/O priority change is permitted for the specified
801 * task, returning 0 if permission is granted, -ve if denied.
802 */
803int cap_task_setioprio(struct task_struct *p, int ioprio)
804{
805 return cap_safe_nice(p);
806}
807
808/**
809 * cap_task_ioprio - Detemine if task priority change is permitted
810 * @p: The task to affect
811 * @nice: The nice value to set
812 *
813 * Detemine if the requested task priority change is permitted for the
814 * specified task, returning 0 if permission is granted, -ve if denied.
815 */
816int cap_task_setnice(struct task_struct *p, int nice)
817{
818 return cap_safe_nice(p);
819}
820
821/*
822 * Implement PR_CAPBSET_DROP. Attempt to remove the specified capability from
823 * the current task's bounding set. Returns 0 on success, -ve on error.
824 */
825static long cap_prctl_drop(struct cred *new, unsigned long cap)
826{
827 if (!ns_capable(current_user_ns(), CAP_SETPCAP))
828 return -EPERM;
829 if (!cap_valid(cap))
830 return -EINVAL;
831
832 cap_lower(new->cap_bset, cap);
833 return 0;
834}
835
836/**
837 * cap_task_prctl - Implement process control functions for this security module
838 * @option: The process control function requested
839 * @arg2, @arg3, @arg4, @arg5: The argument data for this function
840 *
841 * Allow process control functions (sys_prctl()) to alter capabilities; may
842 * also deny access to other functions not otherwise implemented here.
843 *
844 * Returns 0 or +ve on success, -ENOSYS if this function is not implemented
845 * here, other -ve on error. If -ENOSYS is returned, sys_prctl() and other LSM
846 * modules will consider performing the function.
847 */
848int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3,
849 unsigned long arg4, unsigned long arg5)
850{
851 struct cred *new;
852 long error = 0;
853
854 new = prepare_creds();
855 if (!new)
856 return -ENOMEM;
857
858 switch (option) {
859 case PR_CAPBSET_READ:
860 error = -EINVAL;
861 if (!cap_valid(arg2))
862 goto error;
863 error = !!cap_raised(new->cap_bset, arg2);
864 goto no_change;
865
866 case PR_CAPBSET_DROP:
867 error = cap_prctl_drop(new, arg2);
868 if (error < 0)
869 goto error;
870 goto changed;
871
872 /*
873 * The next four prctl's remain to assist with transitioning a
874 * system from legacy UID=0 based privilege (when filesystem
875 * capabilities are not in use) to a system using filesystem
876 * capabilities only - as the POSIX.1e draft intended.
877 *
878 * Note:
879 *
880 * PR_SET_SECUREBITS =
881 * issecure_mask(SECURE_KEEP_CAPS_LOCKED)
882 * | issecure_mask(SECURE_NOROOT)
883 * | issecure_mask(SECURE_NOROOT_LOCKED)
884 * | issecure_mask(SECURE_NO_SETUID_FIXUP)
885 * | issecure_mask(SECURE_NO_SETUID_FIXUP_LOCKED)
886 *
887 * will ensure that the current process and all of its
888 * children will be locked into a pure
889 * capability-based-privilege environment.
890 */
891 case PR_SET_SECUREBITS:
892 error = -EPERM;
893 if ((((new->securebits & SECURE_ALL_LOCKS) >> 1)
894 & (new->securebits ^ arg2)) /*[1]*/
895 || ((new->securebits & SECURE_ALL_LOCKS & ~arg2)) /*[2]*/
896 || (arg2 & ~(SECURE_ALL_LOCKS | SECURE_ALL_BITS)) /*[3]*/
897 || (cap_capable(current_cred(),
898 current_cred()->user_ns, CAP_SETPCAP,
899 SECURITY_CAP_AUDIT) != 0) /*[4]*/
900 /*
901 * [1] no changing of bits that are locked
902 * [2] no unlocking of locks
903 * [3] no setting of unsupported bits
904 * [4] doing anything requires privilege (go read about
905 * the "sendmail capabilities bug")
906 */
907 )
908 /* cannot change a locked bit */
909 goto error;
910 new->securebits = arg2;
911 goto changed;
912
913 case PR_GET_SECUREBITS:
914 error = new->securebits;
915 goto no_change;
916
917 case PR_GET_KEEPCAPS:
918 if (issecure(SECURE_KEEP_CAPS))
919 error = 1;
920 goto no_change;
921
922 case PR_SET_KEEPCAPS:
923 error = -EINVAL;
924 if (arg2 > 1) /* Note, we rely on arg2 being unsigned here */
925 goto error;
926 error = -EPERM;
927 if (issecure(SECURE_KEEP_CAPS_LOCKED))
928 goto error;
929 if (arg2)
930 new->securebits |= issecure_mask(SECURE_KEEP_CAPS);
931 else
932 new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS);
933 goto changed;
934
935 default:
936 /* No functionality available - continue with default */
937 error = -ENOSYS;
938 goto error;
939 }
940
941 /* Functionality provided */
942changed:
943 return commit_creds(new);
944
945no_change:
946error:
947 abort_creds(new);
948 return error;
949}
950
951/**
952 * cap_vm_enough_memory - Determine whether a new virtual mapping is permitted
953 * @mm: The VM space in which the new mapping is to be made
954 * @pages: The size of the mapping
955 *
956 * Determine whether the allocation of a new virtual mapping by the current
957 * task is permitted, returning 0 if permission is granted, -ve if not.
958 */
959int cap_vm_enough_memory(struct mm_struct *mm, long pages)
960{
961 int cap_sys_admin = 0;
962
963 if (cap_capable(current_cred(), &init_user_ns, CAP_SYS_ADMIN,
964 SECURITY_CAP_NOAUDIT) == 0)
965 cap_sys_admin = 1;
966 return __vm_enough_memory(mm, pages, cap_sys_admin);
967}
968
969/*
970 * cap_mmap_addr - check if able to map given addr
971 * @addr: address attempting to be mapped
972 *
973 * If the process is attempting to map memory below dac_mmap_min_addr they need
974 * CAP_SYS_RAWIO. The other parameters to this function are unused by the
975 * capability security module. Returns 0 if this mapping should be allowed
976 * -EPERM if not.
977 */
978int cap_mmap_addr(unsigned long addr)
979{
980 int ret = 0;
981
982 if (addr < dac_mmap_min_addr) {
983 ret = cap_capable(current_cred(), &init_user_ns, CAP_SYS_RAWIO,
984 SECURITY_CAP_AUDIT);
985 /* set PF_SUPERPRIV if it turns out we allow the low mmap */
986 if (ret == 0)
987 current->flags |= PF_SUPERPRIV;
988 }
989 return ret;
990}
991
992int cap_mmap_file(struct file *file, unsigned long reqprot,
993 unsigned long prot, unsigned long flags)
994{
995 return 0;
996}
1/* Common capabilities, needed by capability.o.
2 *
3 * This program is free software; you can redistribute it and/or modify
4 * it under the terms of the GNU General Public License as published by
5 * the Free Software Foundation; either version 2 of the License, or
6 * (at your option) any later version.
7 *
8 */
9
10#include <linux/capability.h>
11#include <linux/audit.h>
12#include <linux/module.h>
13#include <linux/init.h>
14#include <linux/kernel.h>
15#include <linux/security.h>
16#include <linux/file.h>
17#include <linux/mm.h>
18#include <linux/mman.h>
19#include <linux/pagemap.h>
20#include <linux/swap.h>
21#include <linux/skbuff.h>
22#include <linux/netlink.h>
23#include <linux/ptrace.h>
24#include <linux/xattr.h>
25#include <linux/hugetlb.h>
26#include <linux/mount.h>
27#include <linux/sched.h>
28#include <linux/prctl.h>
29#include <linux/securebits.h>
30#include <linux/user_namespace.h>
31#include <linux/binfmts.h>
32#include <linux/personality.h>
33
34/*
35 * If a non-root user executes a setuid-root binary in
36 * !secure(SECURE_NOROOT) mode, then we raise capabilities.
37 * However if fE is also set, then the intent is for only
38 * the file capabilities to be applied, and the setuid-root
39 * bit is left on either to change the uid (plausible) or
40 * to get full privilege on a kernel without file capabilities
41 * support. So in that case we do not raise capabilities.
42 *
43 * Warn if that happens, once per boot.
44 */
45static void warn_setuid_and_fcaps_mixed(const char *fname)
46{
47 static int warned;
48 if (!warned) {
49 printk(KERN_INFO "warning: `%s' has both setuid-root and"
50 " effective capabilities. Therefore not raising all"
51 " capabilities.\n", fname);
52 warned = 1;
53 }
54}
55
56int cap_netlink_send(struct sock *sk, struct sk_buff *skb)
57{
58 return 0;
59}
60
61/**
62 * cap_capable - Determine whether a task has a particular effective capability
63 * @cred: The credentials to use
64 * @ns: The user namespace in which we need the capability
65 * @cap: The capability to check for
66 * @audit: Whether to write an audit message or not
67 *
68 * Determine whether the nominated task has the specified capability amongst
69 * its effective set, returning 0 if it does, -ve if it does not.
70 *
71 * NOTE WELL: cap_has_capability() cannot be used like the kernel's capable()
72 * and has_capability() functions. That is, it has the reverse semantics:
73 * cap_has_capability() returns 0 when a task has a capability, but the
74 * kernel's capable() and has_capability() returns 1 for this case.
75 */
76int cap_capable(const struct cred *cred, struct user_namespace *targ_ns,
77 int cap, int audit)
78{
79 for (;;) {
80 /* The owner of the user namespace has all caps. */
81 if (targ_ns != &init_user_ns && uid_eq(targ_ns->owner, cred->euid))
82 return 0;
83
84 /* Do we have the necessary capabilities? */
85 if (targ_ns == cred->user_ns)
86 return cap_raised(cred->cap_effective, cap) ? 0 : -EPERM;
87
88 /* Have we tried all of the parent namespaces? */
89 if (targ_ns == &init_user_ns)
90 return -EPERM;
91
92 /*
93 *If you have a capability in a parent user ns, then you have
94 * it over all children user namespaces as well.
95 */
96 targ_ns = targ_ns->parent;
97 }
98
99 /* We never get here */
100}
101
102/**
103 * cap_settime - Determine whether the current process may set the system clock
104 * @ts: The time to set
105 * @tz: The timezone to set
106 *
107 * Determine whether the current process may set the system clock and timezone
108 * information, returning 0 if permission granted, -ve if denied.
109 */
110int cap_settime(const struct timespec *ts, const struct timezone *tz)
111{
112 if (!capable(CAP_SYS_TIME))
113 return -EPERM;
114 return 0;
115}
116
117/**
118 * cap_ptrace_access_check - Determine whether the current process may access
119 * another
120 * @child: The process to be accessed
121 * @mode: The mode of attachment.
122 *
123 * If we are in the same or an ancestor user_ns and have all the target
124 * task's capabilities, then ptrace access is allowed.
125 * If we have the ptrace capability to the target user_ns, then ptrace
126 * access is allowed.
127 * Else denied.
128 *
129 * Determine whether a process may access another, returning 0 if permission
130 * granted, -ve if denied.
131 */
132int cap_ptrace_access_check(struct task_struct *child, unsigned int mode)
133{
134 int ret = 0;
135 const struct cred *cred, *child_cred;
136
137 rcu_read_lock();
138 cred = current_cred();
139 child_cred = __task_cred(child);
140 if (cred->user_ns == child_cred->user_ns &&
141 cap_issubset(child_cred->cap_permitted, cred->cap_permitted))
142 goto out;
143 if (ns_capable(child_cred->user_ns, CAP_SYS_PTRACE))
144 goto out;
145 ret = -EPERM;
146out:
147 rcu_read_unlock();
148 return ret;
149}
150
151/**
152 * cap_ptrace_traceme - Determine whether another process may trace the current
153 * @parent: The task proposed to be the tracer
154 *
155 * If parent is in the same or an ancestor user_ns and has all current's
156 * capabilities, then ptrace access is allowed.
157 * If parent has the ptrace capability to current's user_ns, then ptrace
158 * access is allowed.
159 * Else denied.
160 *
161 * Determine whether the nominated task is permitted to trace the current
162 * process, returning 0 if permission is granted, -ve if denied.
163 */
164int cap_ptrace_traceme(struct task_struct *parent)
165{
166 int ret = 0;
167 const struct cred *cred, *child_cred;
168
169 rcu_read_lock();
170 cred = __task_cred(parent);
171 child_cred = current_cred();
172 if (cred->user_ns == child_cred->user_ns &&
173 cap_issubset(child_cred->cap_permitted, cred->cap_permitted))
174 goto out;
175 if (has_ns_capability(parent, child_cred->user_ns, CAP_SYS_PTRACE))
176 goto out;
177 ret = -EPERM;
178out:
179 rcu_read_unlock();
180 return ret;
181}
182
183/**
184 * cap_capget - Retrieve a task's capability sets
185 * @target: The task from which to retrieve the capability sets
186 * @effective: The place to record the effective set
187 * @inheritable: The place to record the inheritable set
188 * @permitted: The place to record the permitted set
189 *
190 * This function retrieves the capabilities of the nominated task and returns
191 * them to the caller.
192 */
193int cap_capget(struct task_struct *target, kernel_cap_t *effective,
194 kernel_cap_t *inheritable, kernel_cap_t *permitted)
195{
196 const struct cred *cred;
197
198 /* Derived from kernel/capability.c:sys_capget. */
199 rcu_read_lock();
200 cred = __task_cred(target);
201 *effective = cred->cap_effective;
202 *inheritable = cred->cap_inheritable;
203 *permitted = cred->cap_permitted;
204 rcu_read_unlock();
205 return 0;
206}
207
208/*
209 * Determine whether the inheritable capabilities are limited to the old
210 * permitted set. Returns 1 if they are limited, 0 if they are not.
211 */
212static inline int cap_inh_is_capped(void)
213{
214
215 /* they are so limited unless the current task has the CAP_SETPCAP
216 * capability
217 */
218 if (cap_capable(current_cred(), current_cred()->user_ns,
219 CAP_SETPCAP, SECURITY_CAP_AUDIT) == 0)
220 return 0;
221 return 1;
222}
223
224/**
225 * cap_capset - Validate and apply proposed changes to current's capabilities
226 * @new: The proposed new credentials; alterations should be made here
227 * @old: The current task's current credentials
228 * @effective: A pointer to the proposed new effective capabilities set
229 * @inheritable: A pointer to the proposed new inheritable capabilities set
230 * @permitted: A pointer to the proposed new permitted capabilities set
231 *
232 * This function validates and applies a proposed mass change to the current
233 * process's capability sets. The changes are made to the proposed new
234 * credentials, and assuming no error, will be committed by the caller of LSM.
235 */
236int cap_capset(struct cred *new,
237 const struct cred *old,
238 const kernel_cap_t *effective,
239 const kernel_cap_t *inheritable,
240 const kernel_cap_t *permitted)
241{
242 if (cap_inh_is_capped() &&
243 !cap_issubset(*inheritable,
244 cap_combine(old->cap_inheritable,
245 old->cap_permitted)))
246 /* incapable of using this inheritable set */
247 return -EPERM;
248
249 if (!cap_issubset(*inheritable,
250 cap_combine(old->cap_inheritable,
251 old->cap_bset)))
252 /* no new pI capabilities outside bounding set */
253 return -EPERM;
254
255 /* verify restrictions on target's new Permitted set */
256 if (!cap_issubset(*permitted, old->cap_permitted))
257 return -EPERM;
258
259 /* verify the _new_Effective_ is a subset of the _new_Permitted_ */
260 if (!cap_issubset(*effective, *permitted))
261 return -EPERM;
262
263 new->cap_effective = *effective;
264 new->cap_inheritable = *inheritable;
265 new->cap_permitted = *permitted;
266 return 0;
267}
268
269/*
270 * Clear proposed capability sets for execve().
271 */
272static inline void bprm_clear_caps(struct linux_binprm *bprm)
273{
274 cap_clear(bprm->cred->cap_permitted);
275 bprm->cap_effective = false;
276}
277
278/**
279 * cap_inode_need_killpriv - Determine if inode change affects privileges
280 * @dentry: The inode/dentry in being changed with change marked ATTR_KILL_PRIV
281 *
282 * Determine if an inode having a change applied that's marked ATTR_KILL_PRIV
283 * affects the security markings on that inode, and if it is, should
284 * inode_killpriv() be invoked or the change rejected?
285 *
286 * Returns 0 if granted; +ve if granted, but inode_killpriv() is required; and
287 * -ve to deny the change.
288 */
289int cap_inode_need_killpriv(struct dentry *dentry)
290{
291 struct inode *inode = dentry->d_inode;
292 int error;
293
294 if (!inode->i_op->getxattr)
295 return 0;
296
297 error = inode->i_op->getxattr(dentry, XATTR_NAME_CAPS, NULL, 0);
298 if (error <= 0)
299 return 0;
300 return 1;
301}
302
303/**
304 * cap_inode_killpriv - Erase the security markings on an inode
305 * @dentry: The inode/dentry to alter
306 *
307 * Erase the privilege-enhancing security markings on an inode.
308 *
309 * Returns 0 if successful, -ve on error.
310 */
311int cap_inode_killpriv(struct dentry *dentry)
312{
313 struct inode *inode = dentry->d_inode;
314
315 if (!inode->i_op->removexattr)
316 return 0;
317
318 return inode->i_op->removexattr(dentry, XATTR_NAME_CAPS);
319}
320
321/*
322 * Calculate the new process capability sets from the capability sets attached
323 * to a file.
324 */
325static inline int bprm_caps_from_vfs_caps(struct cpu_vfs_cap_data *caps,
326 struct linux_binprm *bprm,
327 bool *effective,
328 bool *has_cap)
329{
330 struct cred *new = bprm->cred;
331 unsigned i;
332 int ret = 0;
333
334 if (caps->magic_etc & VFS_CAP_FLAGS_EFFECTIVE)
335 *effective = true;
336
337 if (caps->magic_etc & VFS_CAP_REVISION_MASK)
338 *has_cap = true;
339
340 CAP_FOR_EACH_U32(i) {
341 __u32 permitted = caps->permitted.cap[i];
342 __u32 inheritable = caps->inheritable.cap[i];
343
344 /*
345 * pP' = (X & fP) | (pI & fI)
346 */
347 new->cap_permitted.cap[i] =
348 (new->cap_bset.cap[i] & permitted) |
349 (new->cap_inheritable.cap[i] & inheritable);
350
351 if (permitted & ~new->cap_permitted.cap[i])
352 /* insufficient to execute correctly */
353 ret = -EPERM;
354 }
355
356 /*
357 * For legacy apps, with no internal support for recognizing they
358 * do not have enough capabilities, we return an error if they are
359 * missing some "forced" (aka file-permitted) capabilities.
360 */
361 return *effective ? ret : 0;
362}
363
364/*
365 * Extract the on-exec-apply capability sets for an executable file.
366 */
367int get_vfs_caps_from_disk(const struct dentry *dentry, struct cpu_vfs_cap_data *cpu_caps)
368{
369 struct inode *inode = dentry->d_inode;
370 __u32 magic_etc;
371 unsigned tocopy, i;
372 int size;
373 struct vfs_cap_data caps;
374
375 memset(cpu_caps, 0, sizeof(struct cpu_vfs_cap_data));
376
377 if (!inode || !inode->i_op->getxattr)
378 return -ENODATA;
379
380 size = inode->i_op->getxattr((struct dentry *)dentry, XATTR_NAME_CAPS, &caps,
381 XATTR_CAPS_SZ);
382 if (size == -ENODATA || size == -EOPNOTSUPP)
383 /* no data, that's ok */
384 return -ENODATA;
385 if (size < 0)
386 return size;
387
388 if (size < sizeof(magic_etc))
389 return -EINVAL;
390
391 cpu_caps->magic_etc = magic_etc = le32_to_cpu(caps.magic_etc);
392
393 switch (magic_etc & VFS_CAP_REVISION_MASK) {
394 case VFS_CAP_REVISION_1:
395 if (size != XATTR_CAPS_SZ_1)
396 return -EINVAL;
397 tocopy = VFS_CAP_U32_1;
398 break;
399 case VFS_CAP_REVISION_2:
400 if (size != XATTR_CAPS_SZ_2)
401 return -EINVAL;
402 tocopy = VFS_CAP_U32_2;
403 break;
404 default:
405 return -EINVAL;
406 }
407
408 CAP_FOR_EACH_U32(i) {
409 if (i >= tocopy)
410 break;
411 cpu_caps->permitted.cap[i] = le32_to_cpu(caps.data[i].permitted);
412 cpu_caps->inheritable.cap[i] = le32_to_cpu(caps.data[i].inheritable);
413 }
414
415 return 0;
416}
417
418/*
419 * Attempt to get the on-exec apply capability sets for an executable file from
420 * its xattrs and, if present, apply them to the proposed credentials being
421 * constructed by execve().
422 */
423static int get_file_caps(struct linux_binprm *bprm, bool *effective, bool *has_cap)
424{
425 struct dentry *dentry;
426 int rc = 0;
427 struct cpu_vfs_cap_data vcaps;
428
429 bprm_clear_caps(bprm);
430
431 if (!file_caps_enabled)
432 return 0;
433
434 if (bprm->file->f_vfsmnt->mnt_flags & MNT_NOSUID)
435 return 0;
436
437 dentry = dget(bprm->file->f_dentry);
438
439 rc = get_vfs_caps_from_disk(dentry, &vcaps);
440 if (rc < 0) {
441 if (rc == -EINVAL)
442 printk(KERN_NOTICE "%s: get_vfs_caps_from_disk returned %d for %s\n",
443 __func__, rc, bprm->filename);
444 else if (rc == -ENODATA)
445 rc = 0;
446 goto out;
447 }
448
449 rc = bprm_caps_from_vfs_caps(&vcaps, bprm, effective, has_cap);
450 if (rc == -EINVAL)
451 printk(KERN_NOTICE "%s: cap_from_disk returned %d for %s\n",
452 __func__, rc, bprm->filename);
453
454out:
455 dput(dentry);
456 if (rc)
457 bprm_clear_caps(bprm);
458
459 return rc;
460}
461
462/**
463 * cap_bprm_set_creds - Set up the proposed credentials for execve().
464 * @bprm: The execution parameters, including the proposed creds
465 *
466 * Set up the proposed credentials for a new execution context being
467 * constructed by execve(). The proposed creds in @bprm->cred is altered,
468 * which won't take effect immediately. Returns 0 if successful, -ve on error.
469 */
470int cap_bprm_set_creds(struct linux_binprm *bprm)
471{
472 const struct cred *old = current_cred();
473 struct cred *new = bprm->cred;
474 bool effective, has_cap = false;
475 int ret;
476 kuid_t root_uid;
477
478 effective = false;
479 ret = get_file_caps(bprm, &effective, &has_cap);
480 if (ret < 0)
481 return ret;
482
483 root_uid = make_kuid(new->user_ns, 0);
484
485 if (!issecure(SECURE_NOROOT)) {
486 /*
487 * If the legacy file capability is set, then don't set privs
488 * for a setuid root binary run by a non-root user. Do set it
489 * for a root user just to cause least surprise to an admin.
490 */
491 if (has_cap && !uid_eq(new->uid, root_uid) && uid_eq(new->euid, root_uid)) {
492 warn_setuid_and_fcaps_mixed(bprm->filename);
493 goto skip;
494 }
495 /*
496 * To support inheritance of root-permissions and suid-root
497 * executables under compatibility mode, we override the
498 * capability sets for the file.
499 *
500 * If only the real uid is 0, we do not set the effective bit.
501 */
502 if (uid_eq(new->euid, root_uid) || uid_eq(new->uid, root_uid)) {
503 /* pP' = (cap_bset & ~0) | (pI & ~0) */
504 new->cap_permitted = cap_combine(old->cap_bset,
505 old->cap_inheritable);
506 }
507 if (uid_eq(new->euid, root_uid))
508 effective = true;
509 }
510skip:
511
512 /* if we have fs caps, clear dangerous personality flags */
513 if (!cap_issubset(new->cap_permitted, old->cap_permitted))
514 bprm->per_clear |= PER_CLEAR_ON_SETID;
515
516
517 /* Don't let someone trace a set[ug]id/setpcap binary with the revised
518 * credentials unless they have the appropriate permit.
519 *
520 * In addition, if NO_NEW_PRIVS, then ensure we get no new privs.
521 */
522 if ((!uid_eq(new->euid, old->uid) ||
523 !gid_eq(new->egid, old->gid) ||
524 !cap_issubset(new->cap_permitted, old->cap_permitted)) &&
525 bprm->unsafe & ~LSM_UNSAFE_PTRACE_CAP) {
526 /* downgrade; they get no more than they had, and maybe less */
527 if (!capable(CAP_SETUID) ||
528 (bprm->unsafe & LSM_UNSAFE_NO_NEW_PRIVS)) {
529 new->euid = new->uid;
530 new->egid = new->gid;
531 }
532 new->cap_permitted = cap_intersect(new->cap_permitted,
533 old->cap_permitted);
534 }
535
536 new->suid = new->fsuid = new->euid;
537 new->sgid = new->fsgid = new->egid;
538
539 if (effective)
540 new->cap_effective = new->cap_permitted;
541 else
542 cap_clear(new->cap_effective);
543 bprm->cap_effective = effective;
544
545 /*
546 * Audit candidate if current->cap_effective is set
547 *
548 * We do not bother to audit if 3 things are true:
549 * 1) cap_effective has all caps
550 * 2) we are root
551 * 3) root is supposed to have all caps (SECURE_NOROOT)
552 * Since this is just a normal root execing a process.
553 *
554 * Number 1 above might fail if you don't have a full bset, but I think
555 * that is interesting information to audit.
556 */
557 if (!cap_isclear(new->cap_effective)) {
558 if (!cap_issubset(CAP_FULL_SET, new->cap_effective) ||
559 !uid_eq(new->euid, root_uid) || !uid_eq(new->uid, root_uid) ||
560 issecure(SECURE_NOROOT)) {
561 ret = audit_log_bprm_fcaps(bprm, new, old);
562 if (ret < 0)
563 return ret;
564 }
565 }
566
567 new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS);
568 return 0;
569}
570
571/**
572 * cap_bprm_secureexec - Determine whether a secure execution is required
573 * @bprm: The execution parameters
574 *
575 * Determine whether a secure execution is required, return 1 if it is, and 0
576 * if it is not.
577 *
578 * The credentials have been committed by this point, and so are no longer
579 * available through @bprm->cred.
580 */
581int cap_bprm_secureexec(struct linux_binprm *bprm)
582{
583 const struct cred *cred = current_cred();
584 kuid_t root_uid = make_kuid(cred->user_ns, 0);
585
586 if (!uid_eq(cred->uid, root_uid)) {
587 if (bprm->cap_effective)
588 return 1;
589 if (!cap_isclear(cred->cap_permitted))
590 return 1;
591 }
592
593 return (!uid_eq(cred->euid, cred->uid) ||
594 !gid_eq(cred->egid, cred->gid));
595}
596
597/**
598 * cap_inode_setxattr - Determine whether an xattr may be altered
599 * @dentry: The inode/dentry being altered
600 * @name: The name of the xattr to be changed
601 * @value: The value that the xattr will be changed to
602 * @size: The size of value
603 * @flags: The replacement flag
604 *
605 * Determine whether an xattr may be altered or set on an inode, returning 0 if
606 * permission is granted, -ve if denied.
607 *
608 * This is used to make sure security xattrs don't get updated or set by those
609 * who aren't privileged to do so.
610 */
611int cap_inode_setxattr(struct dentry *dentry, const char *name,
612 const void *value, size_t size, int flags)
613{
614 if (!strcmp(name, XATTR_NAME_CAPS)) {
615 if (!capable(CAP_SETFCAP))
616 return -EPERM;
617 return 0;
618 }
619
620 if (!strncmp(name, XATTR_SECURITY_PREFIX,
621 sizeof(XATTR_SECURITY_PREFIX) - 1) &&
622 !capable(CAP_SYS_ADMIN))
623 return -EPERM;
624 return 0;
625}
626
627/**
628 * cap_inode_removexattr - Determine whether an xattr may be removed
629 * @dentry: The inode/dentry being altered
630 * @name: The name of the xattr to be changed
631 *
632 * Determine whether an xattr may be removed from an inode, returning 0 if
633 * permission is granted, -ve if denied.
634 *
635 * This is used to make sure security xattrs don't get removed by those who
636 * aren't privileged to remove them.
637 */
638int cap_inode_removexattr(struct dentry *dentry, const char *name)
639{
640 if (!strcmp(name, XATTR_NAME_CAPS)) {
641 if (!capable(CAP_SETFCAP))
642 return -EPERM;
643 return 0;
644 }
645
646 if (!strncmp(name, XATTR_SECURITY_PREFIX,
647 sizeof(XATTR_SECURITY_PREFIX) - 1) &&
648 !capable(CAP_SYS_ADMIN))
649 return -EPERM;
650 return 0;
651}
652
653/*
654 * cap_emulate_setxuid() fixes the effective / permitted capabilities of
655 * a process after a call to setuid, setreuid, or setresuid.
656 *
657 * 1) When set*uiding _from_ one of {r,e,s}uid == 0 _to_ all of
658 * {r,e,s}uid != 0, the permitted and effective capabilities are
659 * cleared.
660 *
661 * 2) When set*uiding _from_ euid == 0 _to_ euid != 0, the effective
662 * capabilities of the process are cleared.
663 *
664 * 3) When set*uiding _from_ euid != 0 _to_ euid == 0, the effective
665 * capabilities are set to the permitted capabilities.
666 *
667 * fsuid is handled elsewhere. fsuid == 0 and {r,e,s}uid!= 0 should
668 * never happen.
669 *
670 * -astor
671 *
672 * cevans - New behaviour, Oct '99
673 * A process may, via prctl(), elect to keep its capabilities when it
674 * calls setuid() and switches away from uid==0. Both permitted and
675 * effective sets will be retained.
676 * Without this change, it was impossible for a daemon to drop only some
677 * of its privilege. The call to setuid(!=0) would drop all privileges!
678 * Keeping uid 0 is not an option because uid 0 owns too many vital
679 * files..
680 * Thanks to Olaf Kirch and Peter Benie for spotting this.
681 */
682static inline void cap_emulate_setxuid(struct cred *new, const struct cred *old)
683{
684 kuid_t root_uid = make_kuid(old->user_ns, 0);
685
686 if ((uid_eq(old->uid, root_uid) ||
687 uid_eq(old->euid, root_uid) ||
688 uid_eq(old->suid, root_uid)) &&
689 (!uid_eq(new->uid, root_uid) &&
690 !uid_eq(new->euid, root_uid) &&
691 !uid_eq(new->suid, root_uid)) &&
692 !issecure(SECURE_KEEP_CAPS)) {
693 cap_clear(new->cap_permitted);
694 cap_clear(new->cap_effective);
695 }
696 if (uid_eq(old->euid, root_uid) && !uid_eq(new->euid, root_uid))
697 cap_clear(new->cap_effective);
698 if (!uid_eq(old->euid, root_uid) && uid_eq(new->euid, root_uid))
699 new->cap_effective = new->cap_permitted;
700}
701
702/**
703 * cap_task_fix_setuid - Fix up the results of setuid() call
704 * @new: The proposed credentials
705 * @old: The current task's current credentials
706 * @flags: Indications of what has changed
707 *
708 * Fix up the results of setuid() call before the credential changes are
709 * actually applied, returning 0 to grant the changes, -ve to deny them.
710 */
711int cap_task_fix_setuid(struct cred *new, const struct cred *old, int flags)
712{
713 switch (flags) {
714 case LSM_SETID_RE:
715 case LSM_SETID_ID:
716 case LSM_SETID_RES:
717 /* juggle the capabilities to follow [RES]UID changes unless
718 * otherwise suppressed */
719 if (!issecure(SECURE_NO_SETUID_FIXUP))
720 cap_emulate_setxuid(new, old);
721 break;
722
723 case LSM_SETID_FS:
724 /* juggle the capabilties to follow FSUID changes, unless
725 * otherwise suppressed
726 *
727 * FIXME - is fsuser used for all CAP_FS_MASK capabilities?
728 * if not, we might be a bit too harsh here.
729 */
730 if (!issecure(SECURE_NO_SETUID_FIXUP)) {
731 kuid_t root_uid = make_kuid(old->user_ns, 0);
732 if (uid_eq(old->fsuid, root_uid) && !uid_eq(new->fsuid, root_uid))
733 new->cap_effective =
734 cap_drop_fs_set(new->cap_effective);
735
736 if (!uid_eq(old->fsuid, root_uid) && uid_eq(new->fsuid, root_uid))
737 new->cap_effective =
738 cap_raise_fs_set(new->cap_effective,
739 new->cap_permitted);
740 }
741 break;
742
743 default:
744 return -EINVAL;
745 }
746
747 return 0;
748}
749
750/*
751 * Rationale: code calling task_setscheduler, task_setioprio, and
752 * task_setnice, assumes that
753 * . if capable(cap_sys_nice), then those actions should be allowed
754 * . if not capable(cap_sys_nice), but acting on your own processes,
755 * then those actions should be allowed
756 * This is insufficient now since you can call code without suid, but
757 * yet with increased caps.
758 * So we check for increased caps on the target process.
759 */
760static int cap_safe_nice(struct task_struct *p)
761{
762 int is_subset;
763
764 rcu_read_lock();
765 is_subset = cap_issubset(__task_cred(p)->cap_permitted,
766 current_cred()->cap_permitted);
767 rcu_read_unlock();
768
769 if (!is_subset && !capable(CAP_SYS_NICE))
770 return -EPERM;
771 return 0;
772}
773
774/**
775 * cap_task_setscheduler - Detemine if scheduler policy change is permitted
776 * @p: The task to affect
777 *
778 * Detemine if the requested scheduler policy change is permitted for the
779 * specified task, returning 0 if permission is granted, -ve if denied.
780 */
781int cap_task_setscheduler(struct task_struct *p)
782{
783 return cap_safe_nice(p);
784}
785
786/**
787 * cap_task_ioprio - Detemine if I/O priority change is permitted
788 * @p: The task to affect
789 * @ioprio: The I/O priority to set
790 *
791 * Detemine if the requested I/O priority change is permitted for the specified
792 * task, returning 0 if permission is granted, -ve if denied.
793 */
794int cap_task_setioprio(struct task_struct *p, int ioprio)
795{
796 return cap_safe_nice(p);
797}
798
799/**
800 * cap_task_ioprio - Detemine if task priority change is permitted
801 * @p: The task to affect
802 * @nice: The nice value to set
803 *
804 * Detemine if the requested task priority change is permitted for the
805 * specified task, returning 0 if permission is granted, -ve if denied.
806 */
807int cap_task_setnice(struct task_struct *p, int nice)
808{
809 return cap_safe_nice(p);
810}
811
812/*
813 * Implement PR_CAPBSET_DROP. Attempt to remove the specified capability from
814 * the current task's bounding set. Returns 0 on success, -ve on error.
815 */
816static long cap_prctl_drop(struct cred *new, unsigned long cap)
817{
818 if (!capable(CAP_SETPCAP))
819 return -EPERM;
820 if (!cap_valid(cap))
821 return -EINVAL;
822
823 cap_lower(new->cap_bset, cap);
824 return 0;
825}
826
827/**
828 * cap_task_prctl - Implement process control functions for this security module
829 * @option: The process control function requested
830 * @arg2, @arg3, @arg4, @arg5: The argument data for this function
831 *
832 * Allow process control functions (sys_prctl()) to alter capabilities; may
833 * also deny access to other functions not otherwise implemented here.
834 *
835 * Returns 0 or +ve on success, -ENOSYS if this function is not implemented
836 * here, other -ve on error. If -ENOSYS is returned, sys_prctl() and other LSM
837 * modules will consider performing the function.
838 */
839int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3,
840 unsigned long arg4, unsigned long arg5)
841{
842 struct cred *new;
843 long error = 0;
844
845 new = prepare_creds();
846 if (!new)
847 return -ENOMEM;
848
849 switch (option) {
850 case PR_CAPBSET_READ:
851 error = -EINVAL;
852 if (!cap_valid(arg2))
853 goto error;
854 error = !!cap_raised(new->cap_bset, arg2);
855 goto no_change;
856
857 case PR_CAPBSET_DROP:
858 error = cap_prctl_drop(new, arg2);
859 if (error < 0)
860 goto error;
861 goto changed;
862
863 /*
864 * The next four prctl's remain to assist with transitioning a
865 * system from legacy UID=0 based privilege (when filesystem
866 * capabilities are not in use) to a system using filesystem
867 * capabilities only - as the POSIX.1e draft intended.
868 *
869 * Note:
870 *
871 * PR_SET_SECUREBITS =
872 * issecure_mask(SECURE_KEEP_CAPS_LOCKED)
873 * | issecure_mask(SECURE_NOROOT)
874 * | issecure_mask(SECURE_NOROOT_LOCKED)
875 * | issecure_mask(SECURE_NO_SETUID_FIXUP)
876 * | issecure_mask(SECURE_NO_SETUID_FIXUP_LOCKED)
877 *
878 * will ensure that the current process and all of its
879 * children will be locked into a pure
880 * capability-based-privilege environment.
881 */
882 case PR_SET_SECUREBITS:
883 error = -EPERM;
884 if ((((new->securebits & SECURE_ALL_LOCKS) >> 1)
885 & (new->securebits ^ arg2)) /*[1]*/
886 || ((new->securebits & SECURE_ALL_LOCKS & ~arg2)) /*[2]*/
887 || (arg2 & ~(SECURE_ALL_LOCKS | SECURE_ALL_BITS)) /*[3]*/
888 || (cap_capable(current_cred(),
889 current_cred()->user_ns, CAP_SETPCAP,
890 SECURITY_CAP_AUDIT) != 0) /*[4]*/
891 /*
892 * [1] no changing of bits that are locked
893 * [2] no unlocking of locks
894 * [3] no setting of unsupported bits
895 * [4] doing anything requires privilege (go read about
896 * the "sendmail capabilities bug")
897 */
898 )
899 /* cannot change a locked bit */
900 goto error;
901 new->securebits = arg2;
902 goto changed;
903
904 case PR_GET_SECUREBITS:
905 error = new->securebits;
906 goto no_change;
907
908 case PR_GET_KEEPCAPS:
909 if (issecure(SECURE_KEEP_CAPS))
910 error = 1;
911 goto no_change;
912
913 case PR_SET_KEEPCAPS:
914 error = -EINVAL;
915 if (arg2 > 1) /* Note, we rely on arg2 being unsigned here */
916 goto error;
917 error = -EPERM;
918 if (issecure(SECURE_KEEP_CAPS_LOCKED))
919 goto error;
920 if (arg2)
921 new->securebits |= issecure_mask(SECURE_KEEP_CAPS);
922 else
923 new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS);
924 goto changed;
925
926 default:
927 /* No functionality available - continue with default */
928 error = -ENOSYS;
929 goto error;
930 }
931
932 /* Functionality provided */
933changed:
934 return commit_creds(new);
935
936no_change:
937error:
938 abort_creds(new);
939 return error;
940}
941
942/**
943 * cap_vm_enough_memory - Determine whether a new virtual mapping is permitted
944 * @mm: The VM space in which the new mapping is to be made
945 * @pages: The size of the mapping
946 *
947 * Determine whether the allocation of a new virtual mapping by the current
948 * task is permitted, returning 0 if permission is granted, -ve if not.
949 */
950int cap_vm_enough_memory(struct mm_struct *mm, long pages)
951{
952 int cap_sys_admin = 0;
953
954 if (cap_capable(current_cred(), &init_user_ns, CAP_SYS_ADMIN,
955 SECURITY_CAP_NOAUDIT) == 0)
956 cap_sys_admin = 1;
957 return __vm_enough_memory(mm, pages, cap_sys_admin);
958}
959
960/*
961 * cap_mmap_addr - check if able to map given addr
962 * @addr: address attempting to be mapped
963 *
964 * If the process is attempting to map memory below dac_mmap_min_addr they need
965 * CAP_SYS_RAWIO. The other parameters to this function are unused by the
966 * capability security module. Returns 0 if this mapping should be allowed
967 * -EPERM if not.
968 */
969int cap_mmap_addr(unsigned long addr)
970{
971 int ret = 0;
972
973 if (addr < dac_mmap_min_addr) {
974 ret = cap_capable(current_cred(), &init_user_ns, CAP_SYS_RAWIO,
975 SECURITY_CAP_AUDIT);
976 /* set PF_SUPERPRIV if it turns out we allow the low mmap */
977 if (ret == 0)
978 current->flags |= PF_SUPERPRIV;
979 }
980 return ret;
981}
982
983int cap_mmap_file(struct file *file, unsigned long reqprot,
984 unsigned long prot, unsigned long flags)
985{
986 return 0;
987}