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1 | /* Common capabilities, needed by capability.o. | |
2 | * | |
3 | * This program is free software; you can redistribute it and/or modify | |
4 | * it under the terms of the GNU General Public License as published by | |
5 | * the Free Software Foundation; either version 2 of the License, or | |
6 | * (at your option) any later version. | |
7 | * | |
8 | */ | |
9 | ||
10 | #include <linux/capability.h> | |
11 | #include <linux/audit.h> | |
12 | #include <linux/module.h> | |
13 | #include <linux/init.h> | |
14 | #include <linux/kernel.h> | |
15 | #include <linux/security.h> | |
16 | #include <linux/file.h> | |
17 | #include <linux/mm.h> | |
18 | #include <linux/mman.h> | |
19 | #include <linux/pagemap.h> | |
20 | #include <linux/swap.h> | |
21 | #include <linux/skbuff.h> | |
22 | #include <linux/netlink.h> | |
23 | #include <linux/ptrace.h> | |
24 | #include <linux/xattr.h> | |
25 | #include <linux/hugetlb.h> | |
26 | #include <linux/mount.h> | |
27 | #include <linux/sched.h> | |
28 | #include <linux/prctl.h> | |
29 | #include <linux/securebits.h> | |
30 | #include <linux/user_namespace.h> | |
31 | #include <linux/binfmts.h> | |
32 | #include <linux/personality.h> | |
33 | ||
34 | /* | |
35 | * If a non-root user executes a setuid-root binary in | |
36 | * !secure(SECURE_NOROOT) mode, then we raise capabilities. | |
37 | * However if fE is also set, then the intent is for only | |
38 | * the file capabilities to be applied, and the setuid-root | |
39 | * bit is left on either to change the uid (plausible) or | |
40 | * to get full privilege on a kernel without file capabilities | |
41 | * support. So in that case we do not raise capabilities. | |
42 | * | |
43 | * Warn if that happens, once per boot. | |
44 | */ | |
45 | static void warn_setuid_and_fcaps_mixed(const char *fname) | |
46 | { | |
47 | static int warned; | |
48 | if (!warned) { | |
49 | printk(KERN_INFO "warning: `%s' has both setuid-root and" | |
50 | " effective capabilities. Therefore not raising all" | |
51 | " capabilities.\n", fname); | |
52 | warned = 1; | |
53 | } | |
54 | } | |
55 | ||
56 | int cap_netlink_send(struct sock *sk, struct sk_buff *skb) | |
57 | { | |
58 | return 0; | |
59 | } | |
60 | ||
61 | /** | |
62 | * cap_capable - Determine whether a task has a particular effective capability | |
63 | * @cred: The credentials to use | |
64 | * @ns: The user namespace in which we need the capability | |
65 | * @cap: The capability to check for | |
66 | * @audit: Whether to write an audit message or not | |
67 | * | |
68 | * Determine whether the nominated task has the specified capability amongst | |
69 | * its effective set, returning 0 if it does, -ve if it does not. | |
70 | * | |
71 | * NOTE WELL: cap_has_capability() cannot be used like the kernel's capable() | |
72 | * and has_capability() functions. That is, it has the reverse semantics: | |
73 | * cap_has_capability() returns 0 when a task has a capability, but the | |
74 | * kernel's capable() and has_capability() returns 1 for this case. | |
75 | */ | |
76 | int cap_capable(const struct cred *cred, struct user_namespace *targ_ns, | |
77 | int cap, int audit) | |
78 | { | |
79 | struct user_namespace *ns = targ_ns; | |
80 | ||
81 | /* See if cred has the capability in the target user namespace | |
82 | * by examining the target user namespace and all of the target | |
83 | * user namespace's parents. | |
84 | */ | |
85 | for (;;) { | |
86 | /* Do we have the necessary capabilities? */ | |
87 | if (ns == cred->user_ns) | |
88 | return cap_raised(cred->cap_effective, cap) ? 0 : -EPERM; | |
89 | ||
90 | /* Have we tried all of the parent namespaces? */ | |
91 | if (ns == &init_user_ns) | |
92 | return -EPERM; | |
93 | ||
94 | /* | |
95 | * The owner of the user namespace in the parent of the | |
96 | * user namespace has all caps. | |
97 | */ | |
98 | if ((ns->parent == cred->user_ns) && uid_eq(ns->owner, cred->euid)) | |
99 | return 0; | |
100 | ||
101 | /* | |
102 | * If you have a capability in a parent user ns, then you have | |
103 | * it over all children user namespaces as well. | |
104 | */ | |
105 | ns = ns->parent; | |
106 | } | |
107 | ||
108 | /* We never get here */ | |
109 | } | |
110 | ||
111 | /** | |
112 | * cap_settime - Determine whether the current process may set the system clock | |
113 | * @ts: The time to set | |
114 | * @tz: The timezone to set | |
115 | * | |
116 | * Determine whether the current process may set the system clock and timezone | |
117 | * information, returning 0 if permission granted, -ve if denied. | |
118 | */ | |
119 | int cap_settime(const struct timespec *ts, const struct timezone *tz) | |
120 | { | |
121 | if (!capable(CAP_SYS_TIME)) | |
122 | return -EPERM; | |
123 | return 0; | |
124 | } | |
125 | ||
126 | /** | |
127 | * cap_ptrace_access_check - Determine whether the current process may access | |
128 | * another | |
129 | * @child: The process to be accessed | |
130 | * @mode: The mode of attachment. | |
131 | * | |
132 | * If we are in the same or an ancestor user_ns and have all the target | |
133 | * task's capabilities, then ptrace access is allowed. | |
134 | * If we have the ptrace capability to the target user_ns, then ptrace | |
135 | * access is allowed. | |
136 | * Else denied. | |
137 | * | |
138 | * Determine whether a process may access another, returning 0 if permission | |
139 | * granted, -ve if denied. | |
140 | */ | |
141 | int cap_ptrace_access_check(struct task_struct *child, unsigned int mode) | |
142 | { | |
143 | int ret = 0; | |
144 | const struct cred *cred, *child_cred; | |
145 | ||
146 | rcu_read_lock(); | |
147 | cred = current_cred(); | |
148 | child_cred = __task_cred(child); | |
149 | if (cred->user_ns == child_cred->user_ns && | |
150 | cap_issubset(child_cred->cap_permitted, cred->cap_permitted)) | |
151 | goto out; | |
152 | if (ns_capable(child_cred->user_ns, CAP_SYS_PTRACE)) | |
153 | goto out; | |
154 | ret = -EPERM; | |
155 | out: | |
156 | rcu_read_unlock(); | |
157 | return ret; | |
158 | } | |
159 | ||
160 | /** | |
161 | * cap_ptrace_traceme - Determine whether another process may trace the current | |
162 | * @parent: The task proposed to be the tracer | |
163 | * | |
164 | * If parent is in the same or an ancestor user_ns and has all current's | |
165 | * capabilities, then ptrace access is allowed. | |
166 | * If parent has the ptrace capability to current's user_ns, then ptrace | |
167 | * access is allowed. | |
168 | * Else denied. | |
169 | * | |
170 | * Determine whether the nominated task is permitted to trace the current | |
171 | * process, returning 0 if permission is granted, -ve if denied. | |
172 | */ | |
173 | int cap_ptrace_traceme(struct task_struct *parent) | |
174 | { | |
175 | int ret = 0; | |
176 | const struct cred *cred, *child_cred; | |
177 | ||
178 | rcu_read_lock(); | |
179 | cred = __task_cred(parent); | |
180 | child_cred = current_cred(); | |
181 | if (cred->user_ns == child_cred->user_ns && | |
182 | cap_issubset(child_cred->cap_permitted, cred->cap_permitted)) | |
183 | goto out; | |
184 | if (has_ns_capability(parent, child_cred->user_ns, CAP_SYS_PTRACE)) | |
185 | goto out; | |
186 | ret = -EPERM; | |
187 | out: | |
188 | rcu_read_unlock(); | |
189 | return ret; | |
190 | } | |
191 | ||
192 | /** | |
193 | * cap_capget - Retrieve a task's capability sets | |
194 | * @target: The task from which to retrieve the capability sets | |
195 | * @effective: The place to record the effective set | |
196 | * @inheritable: The place to record the inheritable set | |
197 | * @permitted: The place to record the permitted set | |
198 | * | |
199 | * This function retrieves the capabilities of the nominated task and returns | |
200 | * them to the caller. | |
201 | */ | |
202 | int cap_capget(struct task_struct *target, kernel_cap_t *effective, | |
203 | kernel_cap_t *inheritable, kernel_cap_t *permitted) | |
204 | { | |
205 | const struct cred *cred; | |
206 | ||
207 | /* Derived from kernel/capability.c:sys_capget. */ | |
208 | rcu_read_lock(); | |
209 | cred = __task_cred(target); | |
210 | *effective = cred->cap_effective; | |
211 | *inheritable = cred->cap_inheritable; | |
212 | *permitted = cred->cap_permitted; | |
213 | rcu_read_unlock(); | |
214 | return 0; | |
215 | } | |
216 | ||
217 | /* | |
218 | * Determine whether the inheritable capabilities are limited to the old | |
219 | * permitted set. Returns 1 if they are limited, 0 if they are not. | |
220 | */ | |
221 | static inline int cap_inh_is_capped(void) | |
222 | { | |
223 | ||
224 | /* they are so limited unless the current task has the CAP_SETPCAP | |
225 | * capability | |
226 | */ | |
227 | if (cap_capable(current_cred(), current_cred()->user_ns, | |
228 | CAP_SETPCAP, SECURITY_CAP_AUDIT) == 0) | |
229 | return 0; | |
230 | return 1; | |
231 | } | |
232 | ||
233 | /** | |
234 | * cap_capset - Validate and apply proposed changes to current's capabilities | |
235 | * @new: The proposed new credentials; alterations should be made here | |
236 | * @old: The current task's current credentials | |
237 | * @effective: A pointer to the proposed new effective capabilities set | |
238 | * @inheritable: A pointer to the proposed new inheritable capabilities set | |
239 | * @permitted: A pointer to the proposed new permitted capabilities set | |
240 | * | |
241 | * This function validates and applies a proposed mass change to the current | |
242 | * process's capability sets. The changes are made to the proposed new | |
243 | * credentials, and assuming no error, will be committed by the caller of LSM. | |
244 | */ | |
245 | int cap_capset(struct cred *new, | |
246 | const struct cred *old, | |
247 | const kernel_cap_t *effective, | |
248 | const kernel_cap_t *inheritable, | |
249 | const kernel_cap_t *permitted) | |
250 | { | |
251 | if (cap_inh_is_capped() && | |
252 | !cap_issubset(*inheritable, | |
253 | cap_combine(old->cap_inheritable, | |
254 | old->cap_permitted))) | |
255 | /* incapable of using this inheritable set */ | |
256 | return -EPERM; | |
257 | ||
258 | if (!cap_issubset(*inheritable, | |
259 | cap_combine(old->cap_inheritable, | |
260 | old->cap_bset))) | |
261 | /* no new pI capabilities outside bounding set */ | |
262 | return -EPERM; | |
263 | ||
264 | /* verify restrictions on target's new Permitted set */ | |
265 | if (!cap_issubset(*permitted, old->cap_permitted)) | |
266 | return -EPERM; | |
267 | ||
268 | /* verify the _new_Effective_ is a subset of the _new_Permitted_ */ | |
269 | if (!cap_issubset(*effective, *permitted)) | |
270 | return -EPERM; | |
271 | ||
272 | new->cap_effective = *effective; | |
273 | new->cap_inheritable = *inheritable; | |
274 | new->cap_permitted = *permitted; | |
275 | return 0; | |
276 | } | |
277 | ||
278 | /* | |
279 | * Clear proposed capability sets for execve(). | |
280 | */ | |
281 | static inline void bprm_clear_caps(struct linux_binprm *bprm) | |
282 | { | |
283 | cap_clear(bprm->cred->cap_permitted); | |
284 | bprm->cap_effective = false; | |
285 | } | |
286 | ||
287 | /** | |
288 | * cap_inode_need_killpriv - Determine if inode change affects privileges | |
289 | * @dentry: The inode/dentry in being changed with change marked ATTR_KILL_PRIV | |
290 | * | |
291 | * Determine if an inode having a change applied that's marked ATTR_KILL_PRIV | |
292 | * affects the security markings on that inode, and if it is, should | |
293 | * inode_killpriv() be invoked or the change rejected? | |
294 | * | |
295 | * Returns 0 if granted; +ve if granted, but inode_killpriv() is required; and | |
296 | * -ve to deny the change. | |
297 | */ | |
298 | int cap_inode_need_killpriv(struct dentry *dentry) | |
299 | { | |
300 | struct inode *inode = dentry->d_inode; | |
301 | int error; | |
302 | ||
303 | if (!inode->i_op->getxattr) | |
304 | return 0; | |
305 | ||
306 | error = inode->i_op->getxattr(dentry, XATTR_NAME_CAPS, NULL, 0); | |
307 | if (error <= 0) | |
308 | return 0; | |
309 | return 1; | |
310 | } | |
311 | ||
312 | /** | |
313 | * cap_inode_killpriv - Erase the security markings on an inode | |
314 | * @dentry: The inode/dentry to alter | |
315 | * | |
316 | * Erase the privilege-enhancing security markings on an inode. | |
317 | * | |
318 | * Returns 0 if successful, -ve on error. | |
319 | */ | |
320 | int cap_inode_killpriv(struct dentry *dentry) | |
321 | { | |
322 | struct inode *inode = dentry->d_inode; | |
323 | ||
324 | if (!inode->i_op->removexattr) | |
325 | return 0; | |
326 | ||
327 | return inode->i_op->removexattr(dentry, XATTR_NAME_CAPS); | |
328 | } | |
329 | ||
330 | /* | |
331 | * Calculate the new process capability sets from the capability sets attached | |
332 | * to a file. | |
333 | */ | |
334 | static inline int bprm_caps_from_vfs_caps(struct cpu_vfs_cap_data *caps, | |
335 | struct linux_binprm *bprm, | |
336 | bool *effective, | |
337 | bool *has_cap) | |
338 | { | |
339 | struct cred *new = bprm->cred; | |
340 | unsigned i; | |
341 | int ret = 0; | |
342 | ||
343 | if (caps->magic_etc & VFS_CAP_FLAGS_EFFECTIVE) | |
344 | *effective = true; | |
345 | ||
346 | if (caps->magic_etc & VFS_CAP_REVISION_MASK) | |
347 | *has_cap = true; | |
348 | ||
349 | CAP_FOR_EACH_U32(i) { | |
350 | __u32 permitted = caps->permitted.cap[i]; | |
351 | __u32 inheritable = caps->inheritable.cap[i]; | |
352 | ||
353 | /* | |
354 | * pP' = (X & fP) | (pI & fI) | |
355 | */ | |
356 | new->cap_permitted.cap[i] = | |
357 | (new->cap_bset.cap[i] & permitted) | | |
358 | (new->cap_inheritable.cap[i] & inheritable); | |
359 | ||
360 | if (permitted & ~new->cap_permitted.cap[i]) | |
361 | /* insufficient to execute correctly */ | |
362 | ret = -EPERM; | |
363 | } | |
364 | ||
365 | /* | |
366 | * For legacy apps, with no internal support for recognizing they | |
367 | * do not have enough capabilities, we return an error if they are | |
368 | * missing some "forced" (aka file-permitted) capabilities. | |
369 | */ | |
370 | return *effective ? ret : 0; | |
371 | } | |
372 | ||
373 | /* | |
374 | * Extract the on-exec-apply capability sets for an executable file. | |
375 | */ | |
376 | int get_vfs_caps_from_disk(const struct dentry *dentry, struct cpu_vfs_cap_data *cpu_caps) | |
377 | { | |
378 | struct inode *inode = dentry->d_inode; | |
379 | __u32 magic_etc; | |
380 | unsigned tocopy, i; | |
381 | int size; | |
382 | struct vfs_cap_data caps; | |
383 | ||
384 | memset(cpu_caps, 0, sizeof(struct cpu_vfs_cap_data)); | |
385 | ||
386 | if (!inode || !inode->i_op->getxattr) | |
387 | return -ENODATA; | |
388 | ||
389 | size = inode->i_op->getxattr((struct dentry *)dentry, XATTR_NAME_CAPS, &caps, | |
390 | XATTR_CAPS_SZ); | |
391 | if (size == -ENODATA || size == -EOPNOTSUPP) | |
392 | /* no data, that's ok */ | |
393 | return -ENODATA; | |
394 | if (size < 0) | |
395 | return size; | |
396 | ||
397 | if (size < sizeof(magic_etc)) | |
398 | return -EINVAL; | |
399 | ||
400 | cpu_caps->magic_etc = magic_etc = le32_to_cpu(caps.magic_etc); | |
401 | ||
402 | switch (magic_etc & VFS_CAP_REVISION_MASK) { | |
403 | case VFS_CAP_REVISION_1: | |
404 | if (size != XATTR_CAPS_SZ_1) | |
405 | return -EINVAL; | |
406 | tocopy = VFS_CAP_U32_1; | |
407 | break; | |
408 | case VFS_CAP_REVISION_2: | |
409 | if (size != XATTR_CAPS_SZ_2) | |
410 | return -EINVAL; | |
411 | tocopy = VFS_CAP_U32_2; | |
412 | break; | |
413 | default: | |
414 | return -EINVAL; | |
415 | } | |
416 | ||
417 | CAP_FOR_EACH_U32(i) { | |
418 | if (i >= tocopy) | |
419 | break; | |
420 | cpu_caps->permitted.cap[i] = le32_to_cpu(caps.data[i].permitted); | |
421 | cpu_caps->inheritable.cap[i] = le32_to_cpu(caps.data[i].inheritable); | |
422 | } | |
423 | ||
424 | return 0; | |
425 | } | |
426 | ||
427 | /* | |
428 | * Attempt to get the on-exec apply capability sets for an executable file from | |
429 | * its xattrs and, if present, apply them to the proposed credentials being | |
430 | * constructed by execve(). | |
431 | */ | |
432 | static int get_file_caps(struct linux_binprm *bprm, bool *effective, bool *has_cap) | |
433 | { | |
434 | struct dentry *dentry; | |
435 | int rc = 0; | |
436 | struct cpu_vfs_cap_data vcaps; | |
437 | ||
438 | bprm_clear_caps(bprm); | |
439 | ||
440 | if (!file_caps_enabled) | |
441 | return 0; | |
442 | ||
443 | if (bprm->file->f_path.mnt->mnt_flags & MNT_NOSUID) | |
444 | return 0; | |
445 | ||
446 | dentry = dget(bprm->file->f_dentry); | |
447 | ||
448 | rc = get_vfs_caps_from_disk(dentry, &vcaps); | |
449 | if (rc < 0) { | |
450 | if (rc == -EINVAL) | |
451 | printk(KERN_NOTICE "%s: get_vfs_caps_from_disk returned %d for %s\n", | |
452 | __func__, rc, bprm->filename); | |
453 | else if (rc == -ENODATA) | |
454 | rc = 0; | |
455 | goto out; | |
456 | } | |
457 | ||
458 | rc = bprm_caps_from_vfs_caps(&vcaps, bprm, effective, has_cap); | |
459 | if (rc == -EINVAL) | |
460 | printk(KERN_NOTICE "%s: cap_from_disk returned %d for %s\n", | |
461 | __func__, rc, bprm->filename); | |
462 | ||
463 | out: | |
464 | dput(dentry); | |
465 | if (rc) | |
466 | bprm_clear_caps(bprm); | |
467 | ||
468 | return rc; | |
469 | } | |
470 | ||
471 | /** | |
472 | * cap_bprm_set_creds - Set up the proposed credentials for execve(). | |
473 | * @bprm: The execution parameters, including the proposed creds | |
474 | * | |
475 | * Set up the proposed credentials for a new execution context being | |
476 | * constructed by execve(). The proposed creds in @bprm->cred is altered, | |
477 | * which won't take effect immediately. Returns 0 if successful, -ve on error. | |
478 | */ | |
479 | int cap_bprm_set_creds(struct linux_binprm *bprm) | |
480 | { | |
481 | const struct cred *old = current_cred(); | |
482 | struct cred *new = bprm->cred; | |
483 | bool effective, has_cap = false; | |
484 | int ret; | |
485 | kuid_t root_uid; | |
486 | ||
487 | effective = false; | |
488 | ret = get_file_caps(bprm, &effective, &has_cap); | |
489 | if (ret < 0) | |
490 | return ret; | |
491 | ||
492 | root_uid = make_kuid(new->user_ns, 0); | |
493 | ||
494 | if (!issecure(SECURE_NOROOT)) { | |
495 | /* | |
496 | * If the legacy file capability is set, then don't set privs | |
497 | * for a setuid root binary run by a non-root user. Do set it | |
498 | * for a root user just to cause least surprise to an admin. | |
499 | */ | |
500 | if (has_cap && !uid_eq(new->uid, root_uid) && uid_eq(new->euid, root_uid)) { | |
501 | warn_setuid_and_fcaps_mixed(bprm->filename); | |
502 | goto skip; | |
503 | } | |
504 | /* | |
505 | * To support inheritance of root-permissions and suid-root | |
506 | * executables under compatibility mode, we override the | |
507 | * capability sets for the file. | |
508 | * | |
509 | * If only the real uid is 0, we do not set the effective bit. | |
510 | */ | |
511 | if (uid_eq(new->euid, root_uid) || uid_eq(new->uid, root_uid)) { | |
512 | /* pP' = (cap_bset & ~0) | (pI & ~0) */ | |
513 | new->cap_permitted = cap_combine(old->cap_bset, | |
514 | old->cap_inheritable); | |
515 | } | |
516 | if (uid_eq(new->euid, root_uid)) | |
517 | effective = true; | |
518 | } | |
519 | skip: | |
520 | ||
521 | /* if we have fs caps, clear dangerous personality flags */ | |
522 | if (!cap_issubset(new->cap_permitted, old->cap_permitted)) | |
523 | bprm->per_clear |= PER_CLEAR_ON_SETID; | |
524 | ||
525 | ||
526 | /* Don't let someone trace a set[ug]id/setpcap binary with the revised | |
527 | * credentials unless they have the appropriate permit. | |
528 | * | |
529 | * In addition, if NO_NEW_PRIVS, then ensure we get no new privs. | |
530 | */ | |
531 | if ((!uid_eq(new->euid, old->uid) || | |
532 | !gid_eq(new->egid, old->gid) || | |
533 | !cap_issubset(new->cap_permitted, old->cap_permitted)) && | |
534 | bprm->unsafe & ~LSM_UNSAFE_PTRACE_CAP) { | |
535 | /* downgrade; they get no more than they had, and maybe less */ | |
536 | if (!capable(CAP_SETUID) || | |
537 | (bprm->unsafe & LSM_UNSAFE_NO_NEW_PRIVS)) { | |
538 | new->euid = new->uid; | |
539 | new->egid = new->gid; | |
540 | } | |
541 | new->cap_permitted = cap_intersect(new->cap_permitted, | |
542 | old->cap_permitted); | |
543 | } | |
544 | ||
545 | new->suid = new->fsuid = new->euid; | |
546 | new->sgid = new->fsgid = new->egid; | |
547 | ||
548 | if (effective) | |
549 | new->cap_effective = new->cap_permitted; | |
550 | else | |
551 | cap_clear(new->cap_effective); | |
552 | bprm->cap_effective = effective; | |
553 | ||
554 | /* | |
555 | * Audit candidate if current->cap_effective is set | |
556 | * | |
557 | * We do not bother to audit if 3 things are true: | |
558 | * 1) cap_effective has all caps | |
559 | * 2) we are root | |
560 | * 3) root is supposed to have all caps (SECURE_NOROOT) | |
561 | * Since this is just a normal root execing a process. | |
562 | * | |
563 | * Number 1 above might fail if you don't have a full bset, but I think | |
564 | * that is interesting information to audit. | |
565 | */ | |
566 | if (!cap_isclear(new->cap_effective)) { | |
567 | if (!cap_issubset(CAP_FULL_SET, new->cap_effective) || | |
568 | !uid_eq(new->euid, root_uid) || !uid_eq(new->uid, root_uid) || | |
569 | issecure(SECURE_NOROOT)) { | |
570 | ret = audit_log_bprm_fcaps(bprm, new, old); | |
571 | if (ret < 0) | |
572 | return ret; | |
573 | } | |
574 | } | |
575 | ||
576 | new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS); | |
577 | return 0; | |
578 | } | |
579 | ||
580 | /** | |
581 | * cap_bprm_secureexec - Determine whether a secure execution is required | |
582 | * @bprm: The execution parameters | |
583 | * | |
584 | * Determine whether a secure execution is required, return 1 if it is, and 0 | |
585 | * if it is not. | |
586 | * | |
587 | * The credentials have been committed by this point, and so are no longer | |
588 | * available through @bprm->cred. | |
589 | */ | |
590 | int cap_bprm_secureexec(struct linux_binprm *bprm) | |
591 | { | |
592 | const struct cred *cred = current_cred(); | |
593 | kuid_t root_uid = make_kuid(cred->user_ns, 0); | |
594 | ||
595 | if (!uid_eq(cred->uid, root_uid)) { | |
596 | if (bprm->cap_effective) | |
597 | return 1; | |
598 | if (!cap_isclear(cred->cap_permitted)) | |
599 | return 1; | |
600 | } | |
601 | ||
602 | return (!uid_eq(cred->euid, cred->uid) || | |
603 | !gid_eq(cred->egid, cred->gid)); | |
604 | } | |
605 | ||
606 | /** | |
607 | * cap_inode_setxattr - Determine whether an xattr may be altered | |
608 | * @dentry: The inode/dentry being altered | |
609 | * @name: The name of the xattr to be changed | |
610 | * @value: The value that the xattr will be changed to | |
611 | * @size: The size of value | |
612 | * @flags: The replacement flag | |
613 | * | |
614 | * Determine whether an xattr may be altered or set on an inode, returning 0 if | |
615 | * permission is granted, -ve if denied. | |
616 | * | |
617 | * This is used to make sure security xattrs don't get updated or set by those | |
618 | * who aren't privileged to do so. | |
619 | */ | |
620 | int cap_inode_setxattr(struct dentry *dentry, const char *name, | |
621 | const void *value, size_t size, int flags) | |
622 | { | |
623 | if (!strcmp(name, XATTR_NAME_CAPS)) { | |
624 | if (!capable(CAP_SETFCAP)) | |
625 | return -EPERM; | |
626 | return 0; | |
627 | } | |
628 | ||
629 | if (!strncmp(name, XATTR_SECURITY_PREFIX, | |
630 | sizeof(XATTR_SECURITY_PREFIX) - 1) && | |
631 | !capable(CAP_SYS_ADMIN)) | |
632 | return -EPERM; | |
633 | return 0; | |
634 | } | |
635 | ||
636 | /** | |
637 | * cap_inode_removexattr - Determine whether an xattr may be removed | |
638 | * @dentry: The inode/dentry being altered | |
639 | * @name: The name of the xattr to be changed | |
640 | * | |
641 | * Determine whether an xattr may be removed from an inode, returning 0 if | |
642 | * permission is granted, -ve if denied. | |
643 | * | |
644 | * This is used to make sure security xattrs don't get removed by those who | |
645 | * aren't privileged to remove them. | |
646 | */ | |
647 | int cap_inode_removexattr(struct dentry *dentry, const char *name) | |
648 | { | |
649 | if (!strcmp(name, XATTR_NAME_CAPS)) { | |
650 | if (!capable(CAP_SETFCAP)) | |
651 | return -EPERM; | |
652 | return 0; | |
653 | } | |
654 | ||
655 | if (!strncmp(name, XATTR_SECURITY_PREFIX, | |
656 | sizeof(XATTR_SECURITY_PREFIX) - 1) && | |
657 | !capable(CAP_SYS_ADMIN)) | |
658 | return -EPERM; | |
659 | return 0; | |
660 | } | |
661 | ||
662 | /* | |
663 | * cap_emulate_setxuid() fixes the effective / permitted capabilities of | |
664 | * a process after a call to setuid, setreuid, or setresuid. | |
665 | * | |
666 | * 1) When set*uiding _from_ one of {r,e,s}uid == 0 _to_ all of | |
667 | * {r,e,s}uid != 0, the permitted and effective capabilities are | |
668 | * cleared. | |
669 | * | |
670 | * 2) When set*uiding _from_ euid == 0 _to_ euid != 0, the effective | |
671 | * capabilities of the process are cleared. | |
672 | * | |
673 | * 3) When set*uiding _from_ euid != 0 _to_ euid == 0, the effective | |
674 | * capabilities are set to the permitted capabilities. | |
675 | * | |
676 | * fsuid is handled elsewhere. fsuid == 0 and {r,e,s}uid!= 0 should | |
677 | * never happen. | |
678 | * | |
679 | * -astor | |
680 | * | |
681 | * cevans - New behaviour, Oct '99 | |
682 | * A process may, via prctl(), elect to keep its capabilities when it | |
683 | * calls setuid() and switches away from uid==0. Both permitted and | |
684 | * effective sets will be retained. | |
685 | * Without this change, it was impossible for a daemon to drop only some | |
686 | * of its privilege. The call to setuid(!=0) would drop all privileges! | |
687 | * Keeping uid 0 is not an option because uid 0 owns too many vital | |
688 | * files.. | |
689 | * Thanks to Olaf Kirch and Peter Benie for spotting this. | |
690 | */ | |
691 | static inline void cap_emulate_setxuid(struct cred *new, const struct cred *old) | |
692 | { | |
693 | kuid_t root_uid = make_kuid(old->user_ns, 0); | |
694 | ||
695 | if ((uid_eq(old->uid, root_uid) || | |
696 | uid_eq(old->euid, root_uid) || | |
697 | uid_eq(old->suid, root_uid)) && | |
698 | (!uid_eq(new->uid, root_uid) && | |
699 | !uid_eq(new->euid, root_uid) && | |
700 | !uid_eq(new->suid, root_uid)) && | |
701 | !issecure(SECURE_KEEP_CAPS)) { | |
702 | cap_clear(new->cap_permitted); | |
703 | cap_clear(new->cap_effective); | |
704 | } | |
705 | if (uid_eq(old->euid, root_uid) && !uid_eq(new->euid, root_uid)) | |
706 | cap_clear(new->cap_effective); | |
707 | if (!uid_eq(old->euid, root_uid) && uid_eq(new->euid, root_uid)) | |
708 | new->cap_effective = new->cap_permitted; | |
709 | } | |
710 | ||
711 | /** | |
712 | * cap_task_fix_setuid - Fix up the results of setuid() call | |
713 | * @new: The proposed credentials | |
714 | * @old: The current task's current credentials | |
715 | * @flags: Indications of what has changed | |
716 | * | |
717 | * Fix up the results of setuid() call before the credential changes are | |
718 | * actually applied, returning 0 to grant the changes, -ve to deny them. | |
719 | */ | |
720 | int cap_task_fix_setuid(struct cred *new, const struct cred *old, int flags) | |
721 | { | |
722 | switch (flags) { | |
723 | case LSM_SETID_RE: | |
724 | case LSM_SETID_ID: | |
725 | case LSM_SETID_RES: | |
726 | /* juggle the capabilities to follow [RES]UID changes unless | |
727 | * otherwise suppressed */ | |
728 | if (!issecure(SECURE_NO_SETUID_FIXUP)) | |
729 | cap_emulate_setxuid(new, old); | |
730 | break; | |
731 | ||
732 | case LSM_SETID_FS: | |
733 | /* juggle the capabilties to follow FSUID changes, unless | |
734 | * otherwise suppressed | |
735 | * | |
736 | * FIXME - is fsuser used for all CAP_FS_MASK capabilities? | |
737 | * if not, we might be a bit too harsh here. | |
738 | */ | |
739 | if (!issecure(SECURE_NO_SETUID_FIXUP)) { | |
740 | kuid_t root_uid = make_kuid(old->user_ns, 0); | |
741 | if (uid_eq(old->fsuid, root_uid) && !uid_eq(new->fsuid, root_uid)) | |
742 | new->cap_effective = | |
743 | cap_drop_fs_set(new->cap_effective); | |
744 | ||
745 | if (!uid_eq(old->fsuid, root_uid) && uid_eq(new->fsuid, root_uid)) | |
746 | new->cap_effective = | |
747 | cap_raise_fs_set(new->cap_effective, | |
748 | new->cap_permitted); | |
749 | } | |
750 | break; | |
751 | ||
752 | default: | |
753 | return -EINVAL; | |
754 | } | |
755 | ||
756 | return 0; | |
757 | } | |
758 | ||
759 | /* | |
760 | * Rationale: code calling task_setscheduler, task_setioprio, and | |
761 | * task_setnice, assumes that | |
762 | * . if capable(cap_sys_nice), then those actions should be allowed | |
763 | * . if not capable(cap_sys_nice), but acting on your own processes, | |
764 | * then those actions should be allowed | |
765 | * This is insufficient now since you can call code without suid, but | |
766 | * yet with increased caps. | |
767 | * So we check for increased caps on the target process. | |
768 | */ | |
769 | static int cap_safe_nice(struct task_struct *p) | |
770 | { | |
771 | int is_subset, ret = 0; | |
772 | ||
773 | rcu_read_lock(); | |
774 | is_subset = cap_issubset(__task_cred(p)->cap_permitted, | |
775 | current_cred()->cap_permitted); | |
776 | if (!is_subset && !ns_capable(__task_cred(p)->user_ns, CAP_SYS_NICE)) | |
777 | ret = -EPERM; | |
778 | rcu_read_unlock(); | |
779 | ||
780 | return ret; | |
781 | } | |
782 | ||
783 | /** | |
784 | * cap_task_setscheduler - Detemine if scheduler policy change is permitted | |
785 | * @p: The task to affect | |
786 | * | |
787 | * Detemine if the requested scheduler policy change is permitted for the | |
788 | * specified task, returning 0 if permission is granted, -ve if denied. | |
789 | */ | |
790 | int cap_task_setscheduler(struct task_struct *p) | |
791 | { | |
792 | return cap_safe_nice(p); | |
793 | } | |
794 | ||
795 | /** | |
796 | * cap_task_ioprio - Detemine if I/O priority change is permitted | |
797 | * @p: The task to affect | |
798 | * @ioprio: The I/O priority to set | |
799 | * | |
800 | * Detemine if the requested I/O priority change is permitted for the specified | |
801 | * task, returning 0 if permission is granted, -ve if denied. | |
802 | */ | |
803 | int cap_task_setioprio(struct task_struct *p, int ioprio) | |
804 | { | |
805 | return cap_safe_nice(p); | |
806 | } | |
807 | ||
808 | /** | |
809 | * cap_task_ioprio - Detemine if task priority change is permitted | |
810 | * @p: The task to affect | |
811 | * @nice: The nice value to set | |
812 | * | |
813 | * Detemine if the requested task priority change is permitted for the | |
814 | * specified task, returning 0 if permission is granted, -ve if denied. | |
815 | */ | |
816 | int cap_task_setnice(struct task_struct *p, int nice) | |
817 | { | |
818 | return cap_safe_nice(p); | |
819 | } | |
820 | ||
821 | /* | |
822 | * Implement PR_CAPBSET_DROP. Attempt to remove the specified capability from | |
823 | * the current task's bounding set. Returns 0 on success, -ve on error. | |
824 | */ | |
825 | static long cap_prctl_drop(struct cred *new, unsigned long cap) | |
826 | { | |
827 | if (!ns_capable(current_user_ns(), CAP_SETPCAP)) | |
828 | return -EPERM; | |
829 | if (!cap_valid(cap)) | |
830 | return -EINVAL; | |
831 | ||
832 | cap_lower(new->cap_bset, cap); | |
833 | return 0; | |
834 | } | |
835 | ||
836 | /** | |
837 | * cap_task_prctl - Implement process control functions for this security module | |
838 | * @option: The process control function requested | |
839 | * @arg2, @arg3, @arg4, @arg5: The argument data for this function | |
840 | * | |
841 | * Allow process control functions (sys_prctl()) to alter capabilities; may | |
842 | * also deny access to other functions not otherwise implemented here. | |
843 | * | |
844 | * Returns 0 or +ve on success, -ENOSYS if this function is not implemented | |
845 | * here, other -ve on error. If -ENOSYS is returned, sys_prctl() and other LSM | |
846 | * modules will consider performing the function. | |
847 | */ | |
848 | int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3, | |
849 | unsigned long arg4, unsigned long arg5) | |
850 | { | |
851 | struct cred *new; | |
852 | long error = 0; | |
853 | ||
854 | new = prepare_creds(); | |
855 | if (!new) | |
856 | return -ENOMEM; | |
857 | ||
858 | switch (option) { | |
859 | case PR_CAPBSET_READ: | |
860 | error = -EINVAL; | |
861 | if (!cap_valid(arg2)) | |
862 | goto error; | |
863 | error = !!cap_raised(new->cap_bset, arg2); | |
864 | goto no_change; | |
865 | ||
866 | case PR_CAPBSET_DROP: | |
867 | error = cap_prctl_drop(new, arg2); | |
868 | if (error < 0) | |
869 | goto error; | |
870 | goto changed; | |
871 | ||
872 | /* | |
873 | * The next four prctl's remain to assist with transitioning a | |
874 | * system from legacy UID=0 based privilege (when filesystem | |
875 | * capabilities are not in use) to a system using filesystem | |
876 | * capabilities only - as the POSIX.1e draft intended. | |
877 | * | |
878 | * Note: | |
879 | * | |
880 | * PR_SET_SECUREBITS = | |
881 | * issecure_mask(SECURE_KEEP_CAPS_LOCKED) | |
882 | * | issecure_mask(SECURE_NOROOT) | |
883 | * | issecure_mask(SECURE_NOROOT_LOCKED) | |
884 | * | issecure_mask(SECURE_NO_SETUID_FIXUP) | |
885 | * | issecure_mask(SECURE_NO_SETUID_FIXUP_LOCKED) | |
886 | * | |
887 | * will ensure that the current process and all of its | |
888 | * children will be locked into a pure | |
889 | * capability-based-privilege environment. | |
890 | */ | |
891 | case PR_SET_SECUREBITS: | |
892 | error = -EPERM; | |
893 | if ((((new->securebits & SECURE_ALL_LOCKS) >> 1) | |
894 | & (new->securebits ^ arg2)) /*[1]*/ | |
895 | || ((new->securebits & SECURE_ALL_LOCKS & ~arg2)) /*[2]*/ | |
896 | || (arg2 & ~(SECURE_ALL_LOCKS | SECURE_ALL_BITS)) /*[3]*/ | |
897 | || (cap_capable(current_cred(), | |
898 | current_cred()->user_ns, CAP_SETPCAP, | |
899 | SECURITY_CAP_AUDIT) != 0) /*[4]*/ | |
900 | /* | |
901 | * [1] no changing of bits that are locked | |
902 | * [2] no unlocking of locks | |
903 | * [3] no setting of unsupported bits | |
904 | * [4] doing anything requires privilege (go read about | |
905 | * the "sendmail capabilities bug") | |
906 | */ | |
907 | ) | |
908 | /* cannot change a locked bit */ | |
909 | goto error; | |
910 | new->securebits = arg2; | |
911 | goto changed; | |
912 | ||
913 | case PR_GET_SECUREBITS: | |
914 | error = new->securebits; | |
915 | goto no_change; | |
916 | ||
917 | case PR_GET_KEEPCAPS: | |
918 | if (issecure(SECURE_KEEP_CAPS)) | |
919 | error = 1; | |
920 | goto no_change; | |
921 | ||
922 | case PR_SET_KEEPCAPS: | |
923 | error = -EINVAL; | |
924 | if (arg2 > 1) /* Note, we rely on arg2 being unsigned here */ | |
925 | goto error; | |
926 | error = -EPERM; | |
927 | if (issecure(SECURE_KEEP_CAPS_LOCKED)) | |
928 | goto error; | |
929 | if (arg2) | |
930 | new->securebits |= issecure_mask(SECURE_KEEP_CAPS); | |
931 | else | |
932 | new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS); | |
933 | goto changed; | |
934 | ||
935 | default: | |
936 | /* No functionality available - continue with default */ | |
937 | error = -ENOSYS; | |
938 | goto error; | |
939 | } | |
940 | ||
941 | /* Functionality provided */ | |
942 | changed: | |
943 | return commit_creds(new); | |
944 | ||
945 | no_change: | |
946 | error: | |
947 | abort_creds(new); | |
948 | return error; | |
949 | } | |
950 | ||
951 | /** | |
952 | * cap_vm_enough_memory - Determine whether a new virtual mapping is permitted | |
953 | * @mm: The VM space in which the new mapping is to be made | |
954 | * @pages: The size of the mapping | |
955 | * | |
956 | * Determine whether the allocation of a new virtual mapping by the current | |
957 | * task is permitted, returning 0 if permission is granted, -ve if not. | |
958 | */ | |
959 | int cap_vm_enough_memory(struct mm_struct *mm, long pages) | |
960 | { | |
961 | int cap_sys_admin = 0; | |
962 | ||
963 | if (cap_capable(current_cred(), &init_user_ns, CAP_SYS_ADMIN, | |
964 | SECURITY_CAP_NOAUDIT) == 0) | |
965 | cap_sys_admin = 1; | |
966 | return __vm_enough_memory(mm, pages, cap_sys_admin); | |
967 | } | |
968 | ||
969 | /* | |
970 | * cap_mmap_addr - check if able to map given addr | |
971 | * @addr: address attempting to be mapped | |
972 | * | |
973 | * If the process is attempting to map memory below dac_mmap_min_addr they need | |
974 | * CAP_SYS_RAWIO. The other parameters to this function are unused by the | |
975 | * capability security module. Returns 0 if this mapping should be allowed | |
976 | * -EPERM if not. | |
977 | */ | |
978 | int cap_mmap_addr(unsigned long addr) | |
979 | { | |
980 | int ret = 0; | |
981 | ||
982 | if (addr < dac_mmap_min_addr) { | |
983 | ret = cap_capable(current_cred(), &init_user_ns, CAP_SYS_RAWIO, | |
984 | SECURITY_CAP_AUDIT); | |
985 | /* set PF_SUPERPRIV if it turns out we allow the low mmap */ | |
986 | if (ret == 0) | |
987 | current->flags |= PF_SUPERPRIV; | |
988 | } | |
989 | return ret; | |
990 | } | |
991 | ||
992 | int cap_mmap_file(struct file *file, unsigned long reqprot, | |
993 | unsigned long prot, unsigned long flags) | |
994 | { | |
995 | return 0; | |
996 | } |