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