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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(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 | * @policy: The policy to effect |
723 | * @lp: The parameters to the scheduling policy |
724 | * |
725 | * Detemine if the requested scheduler policy change is permitted for the |
726 | * specified task, returning 0 if permission is granted, -ve if denied. |
727 | */ |
728 | int cap_task_setscheduler(struct task_struct *p, int policy, |
729 | struct sched_param *lp) |
730 | { |
731 | return cap_safe_nice(p); |
732 | } |
733 | |
734 | /** |
735 | * cap_task_ioprio - Detemine if I/O priority change is permitted |
736 | * @p: The task to affect |
737 | * @ioprio: The I/O priority to set |
738 | * |
739 | * Detemine if the requested I/O priority change is permitted for the specified |
740 | * task, returning 0 if permission is granted, -ve if denied. |
741 | */ |
742 | int cap_task_setioprio(struct task_struct *p, int ioprio) |
743 | { |
744 | return cap_safe_nice(p); |
745 | } |
746 | |
747 | /** |
748 | * cap_task_ioprio - Detemine if task priority change is permitted |
749 | * @p: The task to affect |
750 | * @nice: The nice value to set |
751 | * |
752 | * Detemine if the requested task priority change is permitted for the |
753 | * specified task, returning 0 if permission is granted, -ve if denied. |
754 | */ |
755 | int cap_task_setnice(struct task_struct *p, int nice) |
756 | { |
757 | return cap_safe_nice(p); |
758 | } |
759 | |
760 | /* |
761 | * Implement PR_CAPBSET_DROP. Attempt to remove the specified capability from |
762 | * the current task's bounding set. Returns 0 on success, -ve on error. |
763 | */ |
764 | static long cap_prctl_drop(struct cred *new, unsigned long cap) |
765 | { |
766 | if (!capable(CAP_SETPCAP)) |
767 | return -EPERM; |
768 | if (!cap_valid(cap)) |
769 | return -EINVAL; |
770 | |
771 | cap_lower(new->cap_bset, cap); |
772 | return 0; |
773 | } |
774 | |
775 | /** |
776 | * cap_task_prctl - Implement process control functions for this security module |
777 | * @option: The process control function requested |
778 | * @arg2, @arg3, @arg4, @arg5: The argument data for this function |
779 | * |
780 | * Allow process control functions (sys_prctl()) to alter capabilities; may |
781 | * also deny access to other functions not otherwise implemented here. |
782 | * |
783 | * Returns 0 or +ve on success, -ENOSYS if this function is not implemented |
784 | * here, other -ve on error. If -ENOSYS is returned, sys_prctl() and other LSM |
785 | * modules will consider performing the function. |
786 | */ |
787 | int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3, |
788 | unsigned long arg4, unsigned long arg5) |
789 | { |
790 | struct cred *new; |
791 | long error = 0; |
792 | |
793 | new = prepare_creds(); |
794 | if (!new) |
795 | return -ENOMEM; |
796 | |
797 | switch (option) { |
798 | case PR_CAPBSET_READ: |
799 | error = -EINVAL; |
800 | if (!cap_valid(arg2)) |
801 | goto error; |
802 | error = !!cap_raised(new->cap_bset, arg2); |
803 | goto no_change; |
804 | |
805 | case PR_CAPBSET_DROP: |
806 | error = cap_prctl_drop(new, arg2); |
807 | if (error < 0) |
808 | goto error; |
809 | goto changed; |
810 | |
811 | /* |
812 | * The next four prctl's remain to assist with transitioning a |
813 | * system from legacy UID=0 based privilege (when filesystem |
814 | * capabilities are not in use) to a system using filesystem |
815 | * capabilities only - as the POSIX.1e draft intended. |
816 | * |
817 | * Note: |
818 | * |
819 | * PR_SET_SECUREBITS = |
820 | * issecure_mask(SECURE_KEEP_CAPS_LOCKED) |
821 | * | issecure_mask(SECURE_NOROOT) |
822 | * | issecure_mask(SECURE_NOROOT_LOCKED) |
823 | * | issecure_mask(SECURE_NO_SETUID_FIXUP) |
824 | * | issecure_mask(SECURE_NO_SETUID_FIXUP_LOCKED) |
825 | * |
826 | * will ensure that the current process and all of its |
827 | * children will be locked into a pure |
828 | * capability-based-privilege environment. |
829 | */ |
830 | case PR_SET_SECUREBITS: |
831 | error = -EPERM; |
832 | if ((((new->securebits & SECURE_ALL_LOCKS) >> 1) |
833 | & (new->securebits ^ arg2)) /*[1]*/ |
834 | || ((new->securebits & SECURE_ALL_LOCKS & ~arg2)) /*[2]*/ |
835 | || (arg2 & ~(SECURE_ALL_LOCKS | SECURE_ALL_BITS)) /*[3]*/ |
836 | || (cap_capable(current, current_cred(), CAP_SETPCAP, |
837 | SECURITY_CAP_AUDIT) != 0) /*[4]*/ |
838 | /* |
839 | * [1] no changing of bits that are locked |
840 | * [2] no unlocking of locks |
841 | * [3] no setting of unsupported bits |
842 | * [4] doing anything requires privilege (go read about |
843 | * the "sendmail capabilities bug") |
844 | */ |
845 | ) |
846 | /* cannot change a locked bit */ |
847 | goto error; |
848 | new->securebits = arg2; |
849 | goto changed; |
850 | |
851 | case PR_GET_SECUREBITS: |
852 | error = new->securebits; |
853 | goto no_change; |
854 | |
855 | case PR_GET_KEEPCAPS: |
856 | if (issecure(SECURE_KEEP_CAPS)) |
857 | error = 1; |
858 | goto no_change; |
859 | |
860 | case PR_SET_KEEPCAPS: |
861 | error = -EINVAL; |
862 | if (arg2 > 1) /* Note, we rely on arg2 being unsigned here */ |
863 | goto error; |
864 | error = -EPERM; |
865 | if (issecure(SECURE_KEEP_CAPS_LOCKED)) |
866 | goto error; |
867 | if (arg2) |
868 | new->securebits |= issecure_mask(SECURE_KEEP_CAPS); |
869 | else |
870 | new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS); |
871 | goto changed; |
872 | |
873 | default: |
874 | /* No functionality available - continue with default */ |
875 | error = -ENOSYS; |
876 | goto error; |
877 | } |
878 | |
879 | /* Functionality provided */ |
880 | changed: |
881 | return commit_creds(new); |
882 | |
883 | no_change: |
884 | error: |
885 | abort_creds(new); |
886 | return error; |
887 | } |
888 | |
889 | /** |
890 | * cap_syslog - Determine whether syslog function is permitted |
891 | * @type: Function requested |
892 | * @from_file: Whether this request came from an open file (i.e. /proc) |
893 | * |
894 | * Determine whether the current process is permitted to use a particular |
895 | * syslog function, returning 0 if permission is granted, -ve if not. |
896 | */ |
897 | int cap_syslog(int type, bool from_file) |
898 | { |
899 | if (type != SYSLOG_ACTION_OPEN && from_file) |
900 | return 0; |
901 | if ((type != SYSLOG_ACTION_READ_ALL && |
902 | type != SYSLOG_ACTION_SIZE_BUFFER) && !capable(CAP_SYS_ADMIN)) |
903 | return -EPERM; |
904 | return 0; |
905 | } |
906 | |
907 | /** |
908 | * cap_vm_enough_memory - Determine whether a new virtual mapping is permitted |
909 | * @mm: The VM space in which the new mapping is to be made |
910 | * @pages: The size of the mapping |
911 | * |
912 | * Determine whether the allocation of a new virtual mapping by the current |
913 | * task is permitted, returning 0 if permission is granted, -ve if not. |
914 | */ |
915 | int cap_vm_enough_memory(struct mm_struct *mm, long pages) |
916 | { |
917 | int cap_sys_admin = 0; |
918 | |
919 | if (cap_capable(current, current_cred(), CAP_SYS_ADMIN, |
920 | SECURITY_CAP_NOAUDIT) == 0) |
921 | cap_sys_admin = 1; |
922 | return __vm_enough_memory(mm, pages, cap_sys_admin); |
923 | } |
924 | |
925 | /* |
926 | * cap_file_mmap - check if able to map given addr |
927 | * @file: unused |
928 | * @reqprot: unused |
929 | * @prot: unused |
930 | * @flags: unused |
931 | * @addr: address attempting to be mapped |
932 | * @addr_only: unused |
933 | * |
934 | * If the process is attempting to map memory below mmap_min_addr they need |
935 | * CAP_SYS_RAWIO. The other parameters to this function are unused by the |
936 | * capability security module. Returns 0 if this mapping should be allowed |
937 | * -EPERM if not. |
938 | */ |
939 | int cap_file_mmap(struct file *file, unsigned long reqprot, |
940 | unsigned long prot, unsigned long flags, |
941 | unsigned long addr, unsigned long addr_only) |
942 | { |
943 | int ret = 0; |
944 | |
945 | if (addr < dac_mmap_min_addr) { |
946 | ret = cap_capable(current, current_cred(), CAP_SYS_RAWIO, |
947 | SECURITY_CAP_AUDIT); |
948 | /* set PF_SUPERPRIV if it turns out we allow the low mmap */ |
949 | if (ret == 0) |
950 | current->flags |= PF_SUPERPRIV; |
951 | } |
952 | return ret; |
953 | } |
954 |
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