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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 | */ |
45 | static 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 | |
56 | int 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 | */ |
76 | int 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 | */ |
110 | int 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 | */ |
132 | int 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; |
146 | out: |
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 | */ |
164 | int 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; |
178 | out: |
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 | */ |
193 | int 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 | */ |
212 | static 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 | */ |
236 | int 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 | */ |
272 | static 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 | */ |
289 | int 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 | */ |
311 | int 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 | */ |
325 | static 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 | */ |
367 | int 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 | */ |
423 | static 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 | |
454 | out: |
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 | */ |
470 | int 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 | } |
510 | skip: |
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 | */ |
581 | int 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 | */ |
611 | int 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 | */ |
638 | int 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 | */ |
682 | static 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 | */ |
711 | int 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 | */ |
760 | static 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 | */ |
781 | int 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 | */ |
794 | int 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 | */ |
807 | int 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 | */ |
816 | static 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 | */ |
839 | int 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 */ |
933 | changed: |
934 | return commit_creds(new); |
935 | |
936 | no_change: |
937 | error: |
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 | */ |
950 | int 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 | */ |
969 | int 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 | |
983 | int cap_mmap_file(struct file *file, unsigned long reqprot, |
984 | unsigned long prot, unsigned long flags) |
985 | { |
986 | return 0; |
987 | } |
988 |
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