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