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 #ifdef CONFIG_ANDROID_PARANOID_NETWORK
35 #include <linux/android_aid.h>
36 #endif
37
38 /*
39 * If a non-root user executes a setuid-root binary in
40 * !secure(SECURE_NOROOT) mode, then we raise capabilities.
41 * However if fE is also set, then the intent is for only
42 * the file capabilities to be applied, and the setuid-root
43 * bit is left on either to change the uid (plausible) or
44 * to get full privilege on a kernel without file capabilities
45 * support. So in that case we do not raise capabilities.
46 *
47 * Warn if that happens, once per boot.
48 */
warn_setuid_and_fcaps_mixed(const char * fname)49 static void warn_setuid_and_fcaps_mixed(const char *fname)
50 {
51 static int warned;
52 if (!warned) {
53 printk(KERN_INFO "warning: `%s' has both setuid-root and"
54 " effective capabilities. Therefore not raising all"
55 " capabilities.\n", fname);
56 warned = 1;
57 }
58 }
59
cap_netlink_send(struct sock * sk,struct sk_buff * skb)60 int cap_netlink_send(struct sock *sk, struct sk_buff *skb)
61 {
62 return 0;
63 }
64
65 /**
66 * cap_capable - Determine whether a task has a particular effective capability
67 * @cred: The credentials to use
68 * @ns: The user namespace in which we need the capability
69 * @cap: The capability to check for
70 * @audit: Whether to write an audit message or not
71 *
72 * Determine whether the nominated task has the specified capability amongst
73 * its effective set, returning 0 if it does, -ve if it does not.
74 *
75 * NOTE WELL: cap_has_capability() cannot be used like the kernel's capable()
76 * and has_capability() functions. That is, it has the reverse semantics:
77 * cap_has_capability() returns 0 when a task has a capability, but the
78 * kernel's capable() and has_capability() returns 1 for this case.
79 */
cap_capable(const struct cred * cred,struct user_namespace * targ_ns,int cap,int audit)80 int cap_capable(const struct cred *cred, struct user_namespace *targ_ns,
81 int cap, int audit)
82 {
83 struct user_namespace *ns = targ_ns;
84
85 #ifdef CONFIG_ANDROID_PARANOID_NETWORK
86 if (cap == CAP_NET_RAW && in_egroup_p(AID_NET_RAW))
87 return 0;
88 if (cap == CAP_NET_ADMIN && in_egroup_p(AID_NET_ADMIN))
89 return 0;
90 #endif
91
92 /* See if cred has the capability in the target user namespace
93 * by examining the target user namespace and all of the target
94 * user namespace's parents.
95 */
96 for (;;) {
97 /* Do we have the necessary capabilities? */
98 if (ns == cred->user_ns)
99 return cap_raised(cred->cap_effective, cap) ? 0 : -EPERM;
100
101 /* Have we tried all of the parent namespaces? */
102 if (ns == &init_user_ns)
103 return -EPERM;
104
105 /*
106 * The owner of the user namespace in the parent of the
107 * user namespace has all caps.
108 */
109 if ((ns->parent == cred->user_ns) && uid_eq(ns->owner, cred->euid))
110 return 0;
111
112 /*
113 * If you have a capability in a parent user ns, then you have
114 * it over all children user namespaces as well.
115 */
116 ns = ns->parent;
117 }
118
119 /* We never get here */
120 }
121
122 /**
123 * cap_settime - Determine whether the current process may set the system clock
124 * @ts: The time to set
125 * @tz: The timezone to set
126 *
127 * Determine whether the current process may set the system clock and timezone
128 * information, returning 0 if permission granted, -ve if denied.
129 */
cap_settime(const struct timespec * ts,const struct timezone * tz)130 int cap_settime(const struct timespec *ts, const struct timezone *tz)
131 {
132 if (!capable(CAP_SYS_TIME))
133 return -EPERM;
134 return 0;
135 }
136
137 /**
138 * cap_ptrace_access_check - Determine whether the current process may access
139 * another
140 * @child: The process to be accessed
141 * @mode: The mode of attachment.
142 *
143 * If we are in the same or an ancestor user_ns and have all the target
144 * task's capabilities, then ptrace access is allowed.
145 * If we have the ptrace capability to the target user_ns, then ptrace
146 * access is allowed.
147 * Else denied.
148 *
149 * Determine whether a process may access another, returning 0 if permission
150 * granted, -ve if denied.
151 */
cap_ptrace_access_check(struct task_struct * child,unsigned int mode)152 int cap_ptrace_access_check(struct task_struct *child, unsigned int mode)
153 {
154 int ret = 0;
155 const struct cred *cred, *child_cred;
156 const kernel_cap_t *caller_caps;
157
158 rcu_read_lock();
159 cred = current_cred();
160 child_cred = __task_cred(child);
161 if (mode & PTRACE_MODE_FSCREDS)
162 caller_caps = &cred->cap_effective;
163 else
164 caller_caps = &cred->cap_permitted;
165 if (cred->user_ns == child_cred->user_ns &&
166 cap_issubset(child_cred->cap_permitted, *caller_caps))
167 goto out;
168 if (ns_capable(child_cred->user_ns, CAP_SYS_PTRACE))
169 goto out;
170 ret = -EPERM;
171 out:
172 rcu_read_unlock();
173 return ret;
174 }
175
176 /**
177 * cap_ptrace_traceme - Determine whether another process may trace the current
178 * @parent: The task proposed to be the tracer
179 *
180 * If parent is in the same or an ancestor user_ns and has all current's
181 * capabilities, then ptrace access is allowed.
182 * If parent has the ptrace capability to current's user_ns, then ptrace
183 * access is allowed.
184 * Else denied.
185 *
186 * Determine whether the nominated task is permitted to trace the current
187 * process, returning 0 if permission is granted, -ve if denied.
188 */
cap_ptrace_traceme(struct task_struct * parent)189 int cap_ptrace_traceme(struct task_struct *parent)
190 {
191 int ret = 0;
192 const struct cred *cred, *child_cred;
193
194 rcu_read_lock();
195 cred = __task_cred(parent);
196 child_cred = current_cred();
197 if (cred->user_ns == child_cred->user_ns &&
198 cap_issubset(child_cred->cap_permitted, cred->cap_permitted))
199 goto out;
200 if (has_ns_capability(parent, child_cred->user_ns, CAP_SYS_PTRACE))
201 goto out;
202 ret = -EPERM;
203 out:
204 rcu_read_unlock();
205 return ret;
206 }
207
208 /**
209 * cap_capget - Retrieve a task's capability sets
210 * @target: The task from which to retrieve the capability sets
211 * @effective: The place to record the effective set
212 * @inheritable: The place to record the inheritable set
213 * @permitted: The place to record the permitted set
214 *
215 * This function retrieves the capabilities of the nominated task and returns
216 * them to the caller.
217 */
cap_capget(struct task_struct * target,kernel_cap_t * effective,kernel_cap_t * inheritable,kernel_cap_t * permitted)218 int cap_capget(struct task_struct *target, kernel_cap_t *effective,
219 kernel_cap_t *inheritable, kernel_cap_t *permitted)
220 {
221 const struct cred *cred;
222
223 /* Derived from kernel/capability.c:sys_capget. */
224 rcu_read_lock();
225 cred = __task_cred(target);
226 *effective = cred->cap_effective;
227 *inheritable = cred->cap_inheritable;
228 *permitted = cred->cap_permitted;
229 rcu_read_unlock();
230 return 0;
231 }
232
233 /*
234 * Determine whether the inheritable capabilities are limited to the old
235 * permitted set. Returns 1 if they are limited, 0 if they are not.
236 */
cap_inh_is_capped(void)237 static inline int cap_inh_is_capped(void)
238 {
239
240 /* they are so limited unless the current task has the CAP_SETPCAP
241 * capability
242 */
243 if (cap_capable(current_cred(), current_cred()->user_ns,
244 CAP_SETPCAP, SECURITY_CAP_AUDIT) == 0)
245 return 0;
246 return 1;
247 }
248
249 /**
250 * cap_capset - Validate and apply proposed changes to current's capabilities
251 * @new: The proposed new credentials; alterations should be made here
252 * @old: The current task's current credentials
253 * @effective: A pointer to the proposed new effective capabilities set
254 * @inheritable: A pointer to the proposed new inheritable capabilities set
255 * @permitted: A pointer to the proposed new permitted capabilities set
256 *
257 * This function validates and applies a proposed mass change to the current
258 * process's capability sets. The changes are made to the proposed new
259 * credentials, and assuming no error, will be committed by the caller of LSM.
260 */
cap_capset(struct cred * new,const struct cred * old,const kernel_cap_t * effective,const kernel_cap_t * inheritable,const kernel_cap_t * permitted)261 int cap_capset(struct cred *new,
262 const struct cred *old,
263 const kernel_cap_t *effective,
264 const kernel_cap_t *inheritable,
265 const kernel_cap_t *permitted)
266 {
267 if (cap_inh_is_capped() &&
268 !cap_issubset(*inheritable,
269 cap_combine(old->cap_inheritable,
270 old->cap_permitted)))
271 /* incapable of using this inheritable set */
272 return -EPERM;
273
274 if (!cap_issubset(*inheritable,
275 cap_combine(old->cap_inheritable,
276 old->cap_bset)))
277 /* no new pI capabilities outside bounding set */
278 return -EPERM;
279
280 /* verify restrictions on target's new Permitted set */
281 if (!cap_issubset(*permitted, old->cap_permitted))
282 return -EPERM;
283
284 /* verify the _new_Effective_ is a subset of the _new_Permitted_ */
285 if (!cap_issubset(*effective, *permitted))
286 return -EPERM;
287
288 new->cap_effective = *effective;
289 new->cap_inheritable = *inheritable;
290 new->cap_permitted = *permitted;
291
292 /*
293 * Mask off ambient bits that are no longer both permitted and
294 * inheritable.
295 */
296 new->cap_ambient = cap_intersect(new->cap_ambient,
297 cap_intersect(*permitted,
298 *inheritable));
299 if (WARN_ON(!cap_ambient_invariant_ok(new)))
300 return -EINVAL;
301 return 0;
302 }
303
304 /*
305 * Clear proposed capability sets for execve().
306 */
bprm_clear_caps(struct linux_binprm * bprm)307 static inline void bprm_clear_caps(struct linux_binprm *bprm)
308 {
309 cap_clear(bprm->cred->cap_permitted);
310 bprm->cap_effective = false;
311 }
312
313 /**
314 * cap_inode_need_killpriv - Determine if inode change affects privileges
315 * @dentry: The inode/dentry in being changed with change marked ATTR_KILL_PRIV
316 *
317 * Determine if an inode having a change applied that's marked ATTR_KILL_PRIV
318 * affects the security markings on that inode, and if it is, should
319 * inode_killpriv() be invoked or the change rejected?
320 *
321 * Returns 0 if granted; +ve if granted, but inode_killpriv() is required; and
322 * -ve to deny the change.
323 */
cap_inode_need_killpriv(struct dentry * dentry)324 int cap_inode_need_killpriv(struct dentry *dentry)
325 {
326 struct inode *inode = dentry->d_inode;
327 int error;
328
329 if (!inode->i_op->getxattr)
330 return 0;
331
332 error = inode->i_op->getxattr(dentry, XATTR_NAME_CAPS, NULL, 0);
333 if (error <= 0)
334 return 0;
335 return 1;
336 }
337
338 /**
339 * cap_inode_killpriv - Erase the security markings on an inode
340 * @dentry: The inode/dentry to alter
341 *
342 * Erase the privilege-enhancing security markings on an inode.
343 *
344 * Returns 0 if successful, -ve on error.
345 */
cap_inode_killpriv(struct dentry * dentry)346 int cap_inode_killpriv(struct dentry *dentry)
347 {
348 struct inode *inode = dentry->d_inode;
349
350 if (!inode->i_op->removexattr)
351 return 0;
352
353 return inode->i_op->removexattr(dentry, XATTR_NAME_CAPS);
354 }
355
356 /*
357 * Calculate the new process capability sets from the capability sets attached
358 * to a file.
359 */
bprm_caps_from_vfs_caps(struct cpu_vfs_cap_data * caps,struct linux_binprm * bprm,bool * effective,bool * has_cap)360 static inline int bprm_caps_from_vfs_caps(struct cpu_vfs_cap_data *caps,
361 struct linux_binprm *bprm,
362 bool *effective,
363 bool *has_cap)
364 {
365 struct cred *new = bprm->cred;
366 unsigned i;
367 int ret = 0;
368
369 if (caps->magic_etc & VFS_CAP_FLAGS_EFFECTIVE)
370 *effective = true;
371
372 if (caps->magic_etc & VFS_CAP_REVISION_MASK)
373 *has_cap = true;
374
375 CAP_FOR_EACH_U32(i) {
376 __u32 permitted = caps->permitted.cap[i];
377 __u32 inheritable = caps->inheritable.cap[i];
378
379 /*
380 * pP' = (X & fP) | (pI & fI)
381 * The addition of pA' is handled later.
382 */
383 new->cap_permitted.cap[i] =
384 (new->cap_bset.cap[i] & permitted) |
385 (new->cap_inheritable.cap[i] & inheritable);
386
387 if (permitted & ~new->cap_permitted.cap[i])
388 /* insufficient to execute correctly */
389 ret = -EPERM;
390 }
391
392 /*
393 * For legacy apps, with no internal support for recognizing they
394 * do not have enough capabilities, we return an error if they are
395 * missing some "forced" (aka file-permitted) capabilities.
396 */
397 return *effective ? ret : 0;
398 }
399
400 /*
401 * Extract the on-exec-apply capability sets for an executable file.
402 */
get_vfs_caps_from_disk(const struct dentry * dentry,struct cpu_vfs_cap_data * cpu_caps)403 int get_vfs_caps_from_disk(const struct dentry *dentry, struct cpu_vfs_cap_data *cpu_caps)
404 {
405 struct inode *inode = dentry->d_inode;
406 __u32 magic_etc;
407 unsigned tocopy, i;
408 int size;
409 struct vfs_cap_data caps;
410
411 memset(cpu_caps, 0, sizeof(struct cpu_vfs_cap_data));
412
413 if (!inode || !inode->i_op->getxattr)
414 return -ENODATA;
415
416 size = inode->i_op->getxattr((struct dentry *)dentry, XATTR_NAME_CAPS, &caps,
417 XATTR_CAPS_SZ);
418 if (size == -ENODATA || size == -EOPNOTSUPP)
419 /* no data, that's ok */
420 return -ENODATA;
421 if (size < 0)
422 return size;
423
424 if (size < sizeof(magic_etc))
425 return -EINVAL;
426
427 cpu_caps->magic_etc = magic_etc = le32_to_cpu(caps.magic_etc);
428
429 switch (magic_etc & VFS_CAP_REVISION_MASK) {
430 case VFS_CAP_REVISION_1:
431 if (size != XATTR_CAPS_SZ_1)
432 return -EINVAL;
433 tocopy = VFS_CAP_U32_1;
434 break;
435 case VFS_CAP_REVISION_2:
436 if (size != XATTR_CAPS_SZ_2)
437 return -EINVAL;
438 tocopy = VFS_CAP_U32_2;
439 break;
440 default:
441 return -EINVAL;
442 }
443
444 CAP_FOR_EACH_U32(i) {
445 if (i >= tocopy)
446 break;
447 cpu_caps->permitted.cap[i] = le32_to_cpu(caps.data[i].permitted);
448 cpu_caps->inheritable.cap[i] = le32_to_cpu(caps.data[i].inheritable);
449 }
450
451 cpu_caps->permitted.cap[CAP_LAST_U32] &= CAP_LAST_U32_VALID_MASK;
452 cpu_caps->inheritable.cap[CAP_LAST_U32] &= CAP_LAST_U32_VALID_MASK;
453
454 return 0;
455 }
456
457 /*
458 * Attempt to get the on-exec apply capability sets for an executable file from
459 * its xattrs and, if present, apply them to the proposed credentials being
460 * constructed by execve().
461 */
get_file_caps(struct linux_binprm * bprm,bool * effective,bool * has_cap)462 static int get_file_caps(struct linux_binprm *bprm, bool *effective, bool *has_cap)
463 {
464 struct dentry *dentry;
465 int rc = 0;
466 struct cpu_vfs_cap_data vcaps;
467
468 bprm_clear_caps(bprm);
469
470 if (!file_caps_enabled)
471 return 0;
472
473 if (bprm->file->f_path.mnt->mnt_flags & MNT_NOSUID)
474 return 0;
475
476 dentry = dget(bprm->file->f_dentry);
477
478 rc = get_vfs_caps_from_disk(dentry, &vcaps);
479 if (rc < 0) {
480 if (rc == -EINVAL)
481 printk(KERN_NOTICE "%s: get_vfs_caps_from_disk returned %d for %s\n",
482 __func__, rc, bprm->filename);
483 else if (rc == -ENODATA)
484 rc = 0;
485 goto out;
486 }
487
488 rc = bprm_caps_from_vfs_caps(&vcaps, bprm, effective, has_cap);
489 if (rc == -EINVAL)
490 printk(KERN_NOTICE "%s: cap_from_disk returned %d for %s\n",
491 __func__, rc, bprm->filename);
492
493 out:
494 dput(dentry);
495 if (rc)
496 bprm_clear_caps(bprm);
497
498 return rc;
499 }
500
501 /**
502 * cap_bprm_set_creds - Set up the proposed credentials for execve().
503 * @bprm: The execution parameters, including the proposed creds
504 *
505 * Set up the proposed credentials for a new execution context being
506 * constructed by execve(). The proposed creds in @bprm->cred is altered,
507 * which won't take effect immediately. Returns 0 if successful, -ve on error.
508 */
cap_bprm_set_creds(struct linux_binprm * bprm)509 int cap_bprm_set_creds(struct linux_binprm *bprm)
510 {
511 const struct cred *old = current_cred();
512 struct cred *new = bprm->cred;
513 bool effective, has_cap = false, is_setid;
514 int ret;
515 kuid_t root_uid;
516
517 if (WARN_ON(!cap_ambient_invariant_ok(old)))
518 return -EPERM;
519
520 effective = false;
521 ret = get_file_caps(bprm, &effective, &has_cap);
522 if (ret < 0)
523 return ret;
524
525 root_uid = make_kuid(new->user_ns, 0);
526
527 if (!issecure(SECURE_NOROOT)) {
528 /*
529 * If the legacy file capability is set, then don't set privs
530 * for a setuid root binary run by a non-root user. Do set it
531 * for a root user just to cause least surprise to an admin.
532 */
533 if (has_cap && !uid_eq(new->uid, root_uid) && uid_eq(new->euid, root_uid)) {
534 warn_setuid_and_fcaps_mixed(bprm->filename);
535 goto skip;
536 }
537 /*
538 * To support inheritance of root-permissions and suid-root
539 * executables under compatibility mode, we override the
540 * capability sets for the file.
541 *
542 * If only the real uid is 0, we do not set the effective bit.
543 */
544 if (uid_eq(new->euid, root_uid) || uid_eq(new->uid, root_uid)) {
545 /* pP' = (cap_bset & ~0) | (pI & ~0) */
546 new->cap_permitted = cap_combine(old->cap_bset,
547 old->cap_inheritable);
548 }
549 if (uid_eq(new->euid, root_uid))
550 effective = true;
551 }
552 skip:
553
554 /* if we have fs caps, clear dangerous personality flags */
555 if (!cap_issubset(new->cap_permitted, old->cap_permitted))
556 bprm->per_clear |= PER_CLEAR_ON_SETID;
557
558
559 /* Don't let someone trace a set[ug]id/setpcap binary with the revised
560 * credentials unless they have the appropriate permit.
561 *
562 * In addition, if NO_NEW_PRIVS, then ensure we get no new privs.
563 */
564 is_setid = !uid_eq(new->euid, old->uid) || !gid_eq(new->egid, old->gid);
565
566 if ((is_setid ||
567 !cap_issubset(new->cap_permitted, old->cap_permitted)) &&
568 bprm->unsafe & ~LSM_UNSAFE_PTRACE_CAP) {
569 /* downgrade; they get no more than they had, and maybe less */
570 if (!capable(CAP_SETUID) ||
571 (bprm->unsafe & LSM_UNSAFE_NO_NEW_PRIVS)) {
572 new->euid = new->uid;
573 new->egid = new->gid;
574 }
575 new->cap_permitted = cap_intersect(new->cap_permitted,
576 old->cap_permitted);
577 }
578
579 new->suid = new->fsuid = new->euid;
580 new->sgid = new->fsgid = new->egid;
581
582 /* File caps or setid cancels ambient. */
583 if (has_cap || is_setid)
584 cap_clear(new->cap_ambient);
585
586 /*
587 * Now that we've computed pA', update pP' to give:
588 * pP' = (X & fP) | (pI & fI) | pA'
589 */
590 new->cap_permitted = cap_combine(new->cap_permitted, new->cap_ambient);
591
592 /*
593 * Set pE' = (fE ? pP' : pA'). Because pA' is zero if fE is set,
594 * this is the same as pE' = (fE ? pP' : 0) | pA'.
595 */
596 if (effective)
597 new->cap_effective = new->cap_permitted;
598 else
599 new->cap_effective = new->cap_ambient;
600
601 if (WARN_ON(!cap_ambient_invariant_ok(new)))
602 return -EPERM;
603
604 bprm->cap_effective = effective;
605
606 /*
607 * Audit candidate if current->cap_effective is set
608 *
609 * We do not bother to audit if 3 things are true:
610 * 1) cap_effective has all caps
611 * 2) we are root
612 * 3) root is supposed to have all caps (SECURE_NOROOT)
613 * Since this is just a normal root execing a process.
614 *
615 * Number 1 above might fail if you don't have a full bset, but I think
616 * that is interesting information to audit.
617 */
618 if (!cap_issubset(new->cap_effective, new->cap_ambient)) {
619 if (!cap_issubset(CAP_FULL_SET, new->cap_effective) ||
620 !uid_eq(new->euid, root_uid) || !uid_eq(new->uid, root_uid) ||
621 issecure(SECURE_NOROOT)) {
622 ret = audit_log_bprm_fcaps(bprm, new, old);
623 if (ret < 0)
624 return ret;
625 }
626 }
627
628 new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS);
629
630 if (WARN_ON(!cap_ambient_invariant_ok(new)))
631 return -EPERM;
632
633 return 0;
634 }
635
636 /**
637 * cap_bprm_secureexec - Determine whether a secure execution is required
638 * @bprm: The execution parameters
639 *
640 * Determine whether a secure execution is required, return 1 if it is, and 0
641 * if it is not.
642 *
643 * The credentials have been committed by this point, and so are no longer
644 * available through @bprm->cred.
645 */
cap_bprm_secureexec(struct linux_binprm * bprm)646 int cap_bprm_secureexec(struct linux_binprm *bprm)
647 {
648 const struct cred *cred = current_cred();
649 kuid_t root_uid = make_kuid(cred->user_ns, 0);
650
651 if (!uid_eq(cred->uid, root_uid)) {
652 if (bprm->cap_effective)
653 return 1;
654 if (!cap_issubset(cred->cap_permitted, cred->cap_ambient))
655 return 1;
656 }
657
658 return (!uid_eq(cred->euid, cred->uid) ||
659 !gid_eq(cred->egid, cred->gid));
660 }
661
662 /**
663 * cap_inode_setxattr - Determine whether an xattr may be altered
664 * @dentry: The inode/dentry being altered
665 * @name: The name of the xattr to be changed
666 * @value: The value that the xattr will be changed to
667 * @size: The size of value
668 * @flags: The replacement flag
669 *
670 * Determine whether an xattr may be altered or set on an inode, returning 0 if
671 * permission is granted, -ve if denied.
672 *
673 * This is used to make sure security xattrs don't get updated or set by those
674 * who aren't privileged to do so.
675 */
cap_inode_setxattr(struct dentry * dentry,const char * name,const void * value,size_t size,int flags)676 int cap_inode_setxattr(struct dentry *dentry, const char *name,
677 const void *value, size_t size, int flags)
678 {
679 if (!strcmp(name, XATTR_NAME_CAPS)) {
680 if (!capable(CAP_SETFCAP))
681 return -EPERM;
682 return 0;
683 }
684
685 if (!strncmp(name, XATTR_SECURITY_PREFIX,
686 sizeof(XATTR_SECURITY_PREFIX) - 1) &&
687 !capable(CAP_SYS_ADMIN))
688 return -EPERM;
689 return 0;
690 }
691
692 /**
693 * cap_inode_removexattr - Determine whether an xattr may be removed
694 * @dentry: The inode/dentry being altered
695 * @name: The name of the xattr to be changed
696 *
697 * Determine whether an xattr may be removed from an inode, returning 0 if
698 * permission is granted, -ve if denied.
699 *
700 * This is used to make sure security xattrs don't get removed by those who
701 * aren't privileged to remove them.
702 */
cap_inode_removexattr(struct dentry * dentry,const char * name)703 int cap_inode_removexattr(struct dentry *dentry, const char *name)
704 {
705 if (!strcmp(name, XATTR_NAME_CAPS)) {
706 if (!capable(CAP_SETFCAP))
707 return -EPERM;
708 return 0;
709 }
710
711 if (!strncmp(name, XATTR_SECURITY_PREFIX,
712 sizeof(XATTR_SECURITY_PREFIX) - 1) &&
713 !capable(CAP_SYS_ADMIN))
714 return -EPERM;
715 return 0;
716 }
717
718 /*
719 * cap_emulate_setxuid() fixes the effective / permitted capabilities of
720 * a process after a call to setuid, setreuid, or setresuid.
721 *
722 * 1) When set*uiding _from_ one of {r,e,s}uid == 0 _to_ all of
723 * {r,e,s}uid != 0, the permitted and effective capabilities are
724 * cleared.
725 *
726 * 2) When set*uiding _from_ euid == 0 _to_ euid != 0, the effective
727 * capabilities of the process are cleared.
728 *
729 * 3) When set*uiding _from_ euid != 0 _to_ euid == 0, the effective
730 * capabilities are set to the permitted capabilities.
731 *
732 * fsuid is handled elsewhere. fsuid == 0 and {r,e,s}uid!= 0 should
733 * never happen.
734 *
735 * -astor
736 *
737 * cevans - New behaviour, Oct '99
738 * A process may, via prctl(), elect to keep its capabilities when it
739 * calls setuid() and switches away from uid==0. Both permitted and
740 * effective sets will be retained.
741 * Without this change, it was impossible for a daemon to drop only some
742 * of its privilege. The call to setuid(!=0) would drop all privileges!
743 * Keeping uid 0 is not an option because uid 0 owns too many vital
744 * files..
745 * Thanks to Olaf Kirch and Peter Benie for spotting this.
746 */
cap_emulate_setxuid(struct cred * new,const struct cred * old)747 static inline void cap_emulate_setxuid(struct cred *new, const struct cred *old)
748 {
749 kuid_t root_uid = make_kuid(old->user_ns, 0);
750
751 if ((uid_eq(old->uid, root_uid) ||
752 uid_eq(old->euid, root_uid) ||
753 uid_eq(old->suid, root_uid)) &&
754 (!uid_eq(new->uid, root_uid) &&
755 !uid_eq(new->euid, root_uid) &&
756 !uid_eq(new->suid, root_uid))) {
757 if (!issecure(SECURE_KEEP_CAPS)) {
758 cap_clear(new->cap_permitted);
759 cap_clear(new->cap_effective);
760 }
761
762 /*
763 * Pre-ambient programs expect setresuid to nonroot followed
764 * by exec to drop capabilities. We should make sure that
765 * this remains the case.
766 */
767 cap_clear(new->cap_ambient);
768 }
769 if (uid_eq(old->euid, root_uid) && !uid_eq(new->euid, root_uid))
770 cap_clear(new->cap_effective);
771 if (!uid_eq(old->euid, root_uid) && uid_eq(new->euid, root_uid))
772 new->cap_effective = new->cap_permitted;
773 }
774
775 /**
776 * cap_task_fix_setuid - Fix up the results of setuid() call
777 * @new: The proposed credentials
778 * @old: The current task's current credentials
779 * @flags: Indications of what has changed
780 *
781 * Fix up the results of setuid() call before the credential changes are
782 * actually applied, returning 0 to grant the changes, -ve to deny them.
783 */
cap_task_fix_setuid(struct cred * new,const struct cred * old,int flags)784 int cap_task_fix_setuid(struct cred *new, const struct cred *old, int flags)
785 {
786 switch (flags) {
787 case LSM_SETID_RE:
788 case LSM_SETID_ID:
789 case LSM_SETID_RES:
790 /* juggle the capabilities to follow [RES]UID changes unless
791 * otherwise suppressed */
792 if (!issecure(SECURE_NO_SETUID_FIXUP))
793 cap_emulate_setxuid(new, old);
794 break;
795
796 case LSM_SETID_FS:
797 /* juggle the capabilties to follow FSUID changes, unless
798 * otherwise suppressed
799 *
800 * FIXME - is fsuser used for all CAP_FS_MASK capabilities?
801 * if not, we might be a bit too harsh here.
802 */
803 if (!issecure(SECURE_NO_SETUID_FIXUP)) {
804 kuid_t root_uid = make_kuid(old->user_ns, 0);
805 if (uid_eq(old->fsuid, root_uid) && !uid_eq(new->fsuid, root_uid))
806 new->cap_effective =
807 cap_drop_fs_set(new->cap_effective);
808
809 if (!uid_eq(old->fsuid, root_uid) && uid_eq(new->fsuid, root_uid))
810 new->cap_effective =
811 cap_raise_fs_set(new->cap_effective,
812 new->cap_permitted);
813 }
814 break;
815
816 default:
817 return -EINVAL;
818 }
819
820 return 0;
821 }
822
823 /*
824 * Rationale: code calling task_setscheduler, task_setioprio, and
825 * task_setnice, assumes that
826 * . if capable(cap_sys_nice), then those actions should be allowed
827 * . if not capable(cap_sys_nice), but acting on your own processes,
828 * then those actions should be allowed
829 * This is insufficient now since you can call code without suid, but
830 * yet with increased caps.
831 * So we check for increased caps on the target process.
832 */
cap_safe_nice(struct task_struct * p)833 static int cap_safe_nice(struct task_struct *p)
834 {
835 int is_subset, ret = 0;
836
837 rcu_read_lock();
838 is_subset = cap_issubset(__task_cred(p)->cap_permitted,
839 current_cred()->cap_permitted);
840 if (!is_subset && !ns_capable(__task_cred(p)->user_ns, CAP_SYS_NICE))
841 ret = -EPERM;
842 rcu_read_unlock();
843
844 return ret;
845 }
846
847 /**
848 * cap_task_setscheduler - Detemine if scheduler policy change is permitted
849 * @p: The task to affect
850 *
851 * Detemine if the requested scheduler policy change is permitted for the
852 * specified task, returning 0 if permission is granted, -ve if denied.
853 */
cap_task_setscheduler(struct task_struct * p)854 int cap_task_setscheduler(struct task_struct *p)
855 {
856 return cap_safe_nice(p);
857 }
858
859 /**
860 * cap_task_ioprio - Detemine if I/O priority change is permitted
861 * @p: The task to affect
862 * @ioprio: The I/O priority to set
863 *
864 * Detemine if the requested I/O priority change is permitted for the specified
865 * task, returning 0 if permission is granted, -ve if denied.
866 */
cap_task_setioprio(struct task_struct * p,int ioprio)867 int cap_task_setioprio(struct task_struct *p, int ioprio)
868 {
869 return cap_safe_nice(p);
870 }
871
872 /**
873 * cap_task_ioprio - Detemine if task priority change is permitted
874 * @p: The task to affect
875 * @nice: The nice value to set
876 *
877 * Detemine if the requested task priority change is permitted for the
878 * specified task, returning 0 if permission is granted, -ve if denied.
879 */
cap_task_setnice(struct task_struct * p,int nice)880 int cap_task_setnice(struct task_struct *p, int nice)
881 {
882 return cap_safe_nice(p);
883 }
884
885 /*
886 * Implement PR_CAPBSET_DROP. Attempt to remove the specified capability from
887 * the current task's bounding set. Returns 0 on success, -ve on error.
888 */
cap_prctl_drop(unsigned long cap)889 static int cap_prctl_drop(unsigned long cap)
890 {
891 struct cred *new;
892
893 if (!ns_capable(current_user_ns(), CAP_SETPCAP))
894 return -EPERM;
895 if (!cap_valid(cap))
896 return -EINVAL;
897
898 new = prepare_creds();
899 if (!new)
900 return -ENOMEM;
901 cap_lower(new->cap_bset, cap);
902 return commit_creds(new);
903 }
904
905 /**
906 * cap_task_prctl - Implement process control functions for this security module
907 * @option: The process control function requested
908 * @arg2, @arg3, @arg4, @arg5: The argument data for this function
909 *
910 * Allow process control functions (sys_prctl()) to alter capabilities; may
911 * also deny access to other functions not otherwise implemented here.
912 *
913 * Returns 0 or +ve on success, -ENOSYS if this function is not implemented
914 * here, other -ve on error. If -ENOSYS is returned, sys_prctl() and other LSM
915 * modules will consider performing the function.
916 */
cap_task_prctl(int option,unsigned long arg2,unsigned long arg3,unsigned long arg4,unsigned long arg5)917 int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3,
918 unsigned long arg4, unsigned long arg5)
919 {
920 const struct cred *old = current_cred();
921 struct cred *new;
922
923 switch (option) {
924 case PR_CAPBSET_READ:
925 if (!cap_valid(arg2))
926 return -EINVAL;
927 return !!cap_raised(old->cap_bset, arg2);
928
929 case PR_CAPBSET_DROP:
930 return cap_prctl_drop(arg2);
931
932 /*
933 * The next four prctl's remain to assist with transitioning a
934 * system from legacy UID=0 based privilege (when filesystem
935 * capabilities are not in use) to a system using filesystem
936 * capabilities only - as the POSIX.1e draft intended.
937 *
938 * Note:
939 *
940 * PR_SET_SECUREBITS =
941 * issecure_mask(SECURE_KEEP_CAPS_LOCKED)
942 * | issecure_mask(SECURE_NOROOT)
943 * | issecure_mask(SECURE_NOROOT_LOCKED)
944 * | issecure_mask(SECURE_NO_SETUID_FIXUP)
945 * | issecure_mask(SECURE_NO_SETUID_FIXUP_LOCKED)
946 *
947 * will ensure that the current process and all of its
948 * children will be locked into a pure
949 * capability-based-privilege environment.
950 */
951 case PR_SET_SECUREBITS:
952 if ((((old->securebits & SECURE_ALL_LOCKS) >> 1)
953 & (old->securebits ^ arg2)) /*[1]*/
954 || ((old->securebits & SECURE_ALL_LOCKS & ~arg2)) /*[2]*/
955 || (arg2 & ~(SECURE_ALL_LOCKS | SECURE_ALL_BITS)) /*[3]*/
956 || (cap_capable(current_cred(),
957 current_cred()->user_ns, CAP_SETPCAP,
958 SECURITY_CAP_AUDIT) != 0) /*[4]*/
959 /*
960 * [1] no changing of bits that are locked
961 * [2] no unlocking of locks
962 * [3] no setting of unsupported bits
963 * [4] doing anything requires privilege (go read about
964 * the "sendmail capabilities bug")
965 */
966 )
967 /* cannot change a locked bit */
968 return -EPERM;
969
970 new = prepare_creds();
971 if (!new)
972 return -ENOMEM;
973 new->securebits = arg2;
974 return commit_creds(new);
975
976 case PR_GET_SECUREBITS:
977 return old->securebits;
978
979 case PR_GET_KEEPCAPS:
980 return !!issecure(SECURE_KEEP_CAPS);
981
982 case PR_SET_KEEPCAPS:
983 if (arg2 > 1) /* Note, we rely on arg2 being unsigned here */
984 return -EINVAL;
985 if (issecure(SECURE_KEEP_CAPS_LOCKED))
986 return -EPERM;
987
988 new = prepare_creds();
989 if (!new)
990 return -ENOMEM;
991 if (arg2)
992 new->securebits |= issecure_mask(SECURE_KEEP_CAPS);
993 else
994 new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS);
995 return commit_creds(new);
996
997 case PR_CAP_AMBIENT:
998 if (arg2 == PR_CAP_AMBIENT_CLEAR_ALL) {
999 if (arg3 | arg4 | arg5)
1000 return -EINVAL;
1001
1002 new = prepare_creds();
1003 if (!new)
1004 return -ENOMEM;
1005 cap_clear(new->cap_ambient);
1006 return commit_creds(new);
1007 }
1008
1009 if (((!cap_valid(arg3)) | arg4 | arg5))
1010 return -EINVAL;
1011
1012 if (arg2 == PR_CAP_AMBIENT_IS_SET) {
1013 return !!cap_raised(current_cred()->cap_ambient, arg3);
1014 } else if (arg2 != PR_CAP_AMBIENT_RAISE &&
1015 arg2 != PR_CAP_AMBIENT_LOWER) {
1016 return -EINVAL;
1017 } else {
1018 if (arg2 == PR_CAP_AMBIENT_RAISE &&
1019 (!cap_raised(current_cred()->cap_permitted, arg3) ||
1020 !cap_raised(current_cred()->cap_inheritable,
1021 arg3)))
1022 return -EPERM;
1023
1024 new = prepare_creds();
1025 if (!new)
1026 return -ENOMEM;
1027 if (arg2 == PR_CAP_AMBIENT_RAISE)
1028 cap_raise(new->cap_ambient, arg3);
1029 else
1030 cap_lower(new->cap_ambient, arg3);
1031 return commit_creds(new);
1032 }
1033
1034 default:
1035 /* No functionality available - continue with default */
1036 return -ENOSYS;
1037 }
1038 }
1039
1040 /**
1041 * cap_vm_enough_memory - Determine whether a new virtual mapping is permitted
1042 * @mm: The VM space in which the new mapping is to be made
1043 * @pages: The size of the mapping
1044 *
1045 * Determine whether the allocation of a new virtual mapping by the current
1046 * task is permitted, returning 0 if permission is granted, -ve if not.
1047 */
cap_vm_enough_memory(struct mm_struct * mm,long pages)1048 int cap_vm_enough_memory(struct mm_struct *mm, long pages)
1049 {
1050 int cap_sys_admin = 0;
1051
1052 if (cap_capable(current_cred(), &init_user_ns, CAP_SYS_ADMIN,
1053 SECURITY_CAP_NOAUDIT) == 0)
1054 cap_sys_admin = 1;
1055 return __vm_enough_memory(mm, pages, cap_sys_admin);
1056 }
1057
1058 /*
1059 * cap_mmap_addr - check if able to map given addr
1060 * @addr: address attempting to be mapped
1061 *
1062 * If the process is attempting to map memory below dac_mmap_min_addr they need
1063 * CAP_SYS_RAWIO. The other parameters to this function are unused by the
1064 * capability security module. Returns 0 if this mapping should be allowed
1065 * -EPERM if not.
1066 */
cap_mmap_addr(unsigned long addr)1067 int cap_mmap_addr(unsigned long addr)
1068 {
1069 int ret = 0;
1070
1071 if (addr < dac_mmap_min_addr) {
1072 ret = cap_capable(current_cred(), &init_user_ns, CAP_SYS_RAWIO,
1073 SECURITY_CAP_AUDIT);
1074 /* set PF_SUPERPRIV if it turns out we allow the low mmap */
1075 if (ret == 0)
1076 current->flags |= PF_SUPERPRIV;
1077 }
1078 return ret;
1079 }
1080
cap_mmap_file(struct file * file,unsigned long reqprot,unsigned long prot,unsigned long flags)1081 int cap_mmap_file(struct file *file, unsigned long reqprot,
1082 unsigned long prot, unsigned long flags)
1083 {
1084 return 0;
1085 }
1086