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1 | // SPDX-License-Identifier: GPL-2.0-or-later | |
2 | /* Common capabilities, needed by capability.o. | |
3 | */ | |
4 | ||
5 | #include <linux/capability.h> | |
6 | #include <linux/audit.h> | |
7 | #include <linux/init.h> | |
8 | #include <linux/kernel.h> | |
9 | #include <linux/lsm_hooks.h> | |
10 | #include <linux/file.h> | |
11 | #include <linux/mm.h> | |
12 | #include <linux/mman.h> | |
13 | #include <linux/pagemap.h> | |
14 | #include <linux/swap.h> | |
15 | #include <linux/skbuff.h> | |
16 | #include <linux/netlink.h> | |
17 | #include <linux/ptrace.h> | |
18 | #include <linux/xattr.h> | |
19 | #include <linux/hugetlb.h> | |
20 | #include <linux/mount.h> | |
21 | #include <linux/sched.h> | |
22 | #include <linux/prctl.h> | |
23 | #include <linux/securebits.h> | |
24 | #include <linux/user_namespace.h> | |
25 | #include <linux/binfmts.h> | |
26 | #include <linux/personality.h> | |
27 | ||
28 | /* | |
29 | * If a non-root user executes a setuid-root binary in | |
30 | * !secure(SECURE_NOROOT) mode, then we raise capabilities. | |
31 | * However if fE is also set, then the intent is for only | |
32 | * the file capabilities to be applied, and the setuid-root | |
33 | * bit is left on either to change the uid (plausible) or | |
34 | * to get full privilege on a kernel without file capabilities | |
35 | * support. So in that case we do not raise capabilities. | |
36 | * | |
37 | * Warn if that happens, once per boot. | |
38 | */ | |
39 | static void warn_setuid_and_fcaps_mixed(const char *fname) | |
40 | { | |
41 | static int warned; | |
42 | if (!warned) { | |
43 | printk(KERN_INFO "warning: `%s' has both setuid-root and" | |
44 | " effective capabilities. Therefore not raising all" | |
45 | " capabilities.\n", fname); | |
46 | warned = 1; | |
47 | } | |
48 | } | |
49 | ||
50 | /** | |
51 | * cap_capable - Determine whether a task has a particular effective capability | |
52 | * @cred: The credentials to use | |
53 | * @targ_ns: The user namespace in which we need the capability | |
54 | * @cap: The capability to check for | |
55 | * @opts: Bitmask of options defined in include/linux/security.h | |
56 | * | |
57 | * Determine whether the nominated task has the specified capability amongst | |
58 | * its effective set, returning 0 if it does, -ve if it does not. | |
59 | * | |
60 | * NOTE WELL: cap_has_capability() cannot be used like the kernel's capable() | |
61 | * and has_capability() functions. That is, it has the reverse semantics: | |
62 | * cap_has_capability() returns 0 when a task has a capability, but the | |
63 | * kernel's capable() and has_capability() returns 1 for this case. | |
64 | */ | |
65 | int cap_capable(const struct cred *cred, struct user_namespace *targ_ns, | |
66 | int cap, unsigned int opts) | |
67 | { | |
68 | struct user_namespace *ns = targ_ns; | |
69 | ||
70 | /* See if cred has the capability in the target user namespace | |
71 | * by examining the target user namespace and all of the target | |
72 | * user namespace's parents. | |
73 | */ | |
74 | for (;;) { | |
75 | /* Do we have the necessary capabilities? */ | |
76 | if (ns == cred->user_ns) | |
77 | return cap_raised(cred->cap_effective, cap) ? 0 : -EPERM; | |
78 | ||
79 | /* | |
80 | * If we're already at a lower level than we're looking for, | |
81 | * we're done searching. | |
82 | */ | |
83 | if (ns->level <= cred->user_ns->level) | |
84 | return -EPERM; | |
85 | ||
86 | /* | |
87 | * The owner of the user namespace in the parent of the | |
88 | * user namespace has all caps. | |
89 | */ | |
90 | if ((ns->parent == cred->user_ns) && uid_eq(ns->owner, cred->euid)) | |
91 | return 0; | |
92 | ||
93 | /* | |
94 | * If you have a capability in a parent user ns, then you have | |
95 | * it over all children user namespaces as well. | |
96 | */ | |
97 | ns = ns->parent; | |
98 | } | |
99 | ||
100 | /* We never get here */ | |
101 | } | |
102 | ||
103 | /** | |
104 | * cap_settime - Determine whether the current process may set the system clock | |
105 | * @ts: The time to set | |
106 | * @tz: The timezone to set | |
107 | * | |
108 | * Determine whether the current process may set the system clock and timezone | |
109 | * information, returning 0 if permission granted, -ve if denied. | |
110 | */ | |
111 | int cap_settime(const struct timespec64 *ts, const struct timezone *tz) | |
112 | { | |
113 | if (!capable(CAP_SYS_TIME)) | |
114 | return -EPERM; | |
115 | return 0; | |
116 | } | |
117 | ||
118 | /** | |
119 | * cap_ptrace_access_check - Determine whether the current process may access | |
120 | * another | |
121 | * @child: The process to be accessed | |
122 | * @mode: The mode of attachment. | |
123 | * | |
124 | * If we are in the same or an ancestor user_ns and have all the target | |
125 | * task's capabilities, then ptrace access is allowed. | |
126 | * If we have the ptrace capability to the target user_ns, then ptrace | |
127 | * access is allowed. | |
128 | * Else denied. | |
129 | * | |
130 | * Determine whether a process may access another, returning 0 if permission | |
131 | * granted, -ve if denied. | |
132 | */ | |
133 | int cap_ptrace_access_check(struct task_struct *child, unsigned int mode) | |
134 | { | |
135 | int ret = 0; | |
136 | const struct cred *cred, *child_cred; | |
137 | const kernel_cap_t *caller_caps; | |
138 | ||
139 | rcu_read_lock(); | |
140 | cred = current_cred(); | |
141 | child_cred = __task_cred(child); | |
142 | if (mode & PTRACE_MODE_FSCREDS) | |
143 | caller_caps = &cred->cap_effective; | |
144 | else | |
145 | caller_caps = &cred->cap_permitted; | |
146 | if (cred->user_ns == child_cred->user_ns && | |
147 | cap_issubset(child_cred->cap_permitted, *caller_caps)) | |
148 | goto out; | |
149 | if (ns_capable(child_cred->user_ns, CAP_SYS_PTRACE)) | |
150 | goto out; | |
151 | ret = -EPERM; | |
152 | out: | |
153 | rcu_read_unlock(); | |
154 | return ret; | |
155 | } | |
156 | ||
157 | /** | |
158 | * cap_ptrace_traceme - Determine whether another process may trace the current | |
159 | * @parent: The task proposed to be the tracer | |
160 | * | |
161 | * If parent is in the same or an ancestor user_ns and has all current's | |
162 | * capabilities, then ptrace access is allowed. | |
163 | * If parent has the ptrace capability to current's user_ns, then ptrace | |
164 | * access is allowed. | |
165 | * Else denied. | |
166 | * | |
167 | * Determine whether the nominated task is permitted to trace the current | |
168 | * process, returning 0 if permission is granted, -ve if denied. | |
169 | */ | |
170 | int cap_ptrace_traceme(struct task_struct *parent) | |
171 | { | |
172 | int ret = 0; | |
173 | const struct cred *cred, *child_cred; | |
174 | ||
175 | rcu_read_lock(); | |
176 | cred = __task_cred(parent); | |
177 | child_cred = current_cred(); | |
178 | if (cred->user_ns == child_cred->user_ns && | |
179 | cap_issubset(child_cred->cap_permitted, cred->cap_permitted)) | |
180 | goto out; | |
181 | if (has_ns_capability(parent, child_cred->user_ns, CAP_SYS_PTRACE)) | |
182 | goto out; | |
183 | ret = -EPERM; | |
184 | out: | |
185 | rcu_read_unlock(); | |
186 | return ret; | |
187 | } | |
188 | ||
189 | /** | |
190 | * cap_capget - Retrieve a task's capability sets | |
191 | * @target: The task from which to retrieve the capability sets | |
192 | * @effective: The place to record the effective set | |
193 | * @inheritable: The place to record the inheritable set | |
194 | * @permitted: The place to record the permitted set | |
195 | * | |
196 | * This function retrieves the capabilities of the nominated task and returns | |
197 | * them to the caller. | |
198 | */ | |
199 | int cap_capget(struct task_struct *target, kernel_cap_t *effective, | |
200 | kernel_cap_t *inheritable, kernel_cap_t *permitted) | |
201 | { | |
202 | const struct cred *cred; | |
203 | ||
204 | /* Derived from kernel/capability.c:sys_capget. */ | |
205 | rcu_read_lock(); | |
206 | cred = __task_cred(target); | |
207 | *effective = cred->cap_effective; | |
208 | *inheritable = cred->cap_inheritable; | |
209 | *permitted = cred->cap_permitted; | |
210 | rcu_read_unlock(); | |
211 | return 0; | |
212 | } | |
213 | ||
214 | /* | |
215 | * Determine whether the inheritable capabilities are limited to the old | |
216 | * permitted set. Returns 1 if they are limited, 0 if they are not. | |
217 | */ | |
218 | static inline int cap_inh_is_capped(void) | |
219 | { | |
220 | /* they are so limited unless the current task has the CAP_SETPCAP | |
221 | * capability | |
222 | */ | |
223 | if (cap_capable(current_cred(), current_cred()->user_ns, | |
224 | CAP_SETPCAP, CAP_OPT_NONE) == 0) | |
225 | return 0; | |
226 | return 1; | |
227 | } | |
228 | ||
229 | /** | |
230 | * cap_capset - Validate and apply proposed changes to current's capabilities | |
231 | * @new: The proposed new credentials; alterations should be made here | |
232 | * @old: The current task's current credentials | |
233 | * @effective: A pointer to the proposed new effective capabilities set | |
234 | * @inheritable: A pointer to the proposed new inheritable capabilities set | |
235 | * @permitted: A pointer to the proposed new permitted capabilities set | |
236 | * | |
237 | * This function validates and applies a proposed mass change to the current | |
238 | * process's capability sets. The changes are made to the proposed new | |
239 | * credentials, and assuming no error, will be committed by the caller of LSM. | |
240 | */ | |
241 | int cap_capset(struct cred *new, | |
242 | const struct cred *old, | |
243 | const kernel_cap_t *effective, | |
244 | const kernel_cap_t *inheritable, | |
245 | const kernel_cap_t *permitted) | |
246 | { | |
247 | if (cap_inh_is_capped() && | |
248 | !cap_issubset(*inheritable, | |
249 | cap_combine(old->cap_inheritable, | |
250 | old->cap_permitted))) | |
251 | /* incapable of using this inheritable set */ | |
252 | return -EPERM; | |
253 | ||
254 | if (!cap_issubset(*inheritable, | |
255 | cap_combine(old->cap_inheritable, | |
256 | old->cap_bset))) | |
257 | /* no new pI capabilities outside bounding set */ | |
258 | return -EPERM; | |
259 | ||
260 | /* verify restrictions on target's new Permitted set */ | |
261 | if (!cap_issubset(*permitted, old->cap_permitted)) | |
262 | return -EPERM; | |
263 | ||
264 | /* verify the _new_Effective_ is a subset of the _new_Permitted_ */ | |
265 | if (!cap_issubset(*effective, *permitted)) | |
266 | return -EPERM; | |
267 | ||
268 | new->cap_effective = *effective; | |
269 | new->cap_inheritable = *inheritable; | |
270 | new->cap_permitted = *permitted; | |
271 | ||
272 | /* | |
273 | * Mask off ambient bits that are no longer both permitted and | |
274 | * inheritable. | |
275 | */ | |
276 | new->cap_ambient = cap_intersect(new->cap_ambient, | |
277 | cap_intersect(*permitted, | |
278 | *inheritable)); | |
279 | if (WARN_ON(!cap_ambient_invariant_ok(new))) | |
280 | return -EINVAL; | |
281 | return 0; | |
282 | } | |
283 | ||
284 | /** | |
285 | * cap_inode_need_killpriv - Determine if inode change affects privileges | |
286 | * @dentry: The inode/dentry in being changed with change marked ATTR_KILL_PRIV | |
287 | * | |
288 | * Determine if an inode having a change applied that's marked ATTR_KILL_PRIV | |
289 | * affects the security markings on that inode, and if it is, should | |
290 | * inode_killpriv() be invoked or the change rejected. | |
291 | * | |
292 | * Return: 1 if security.capability has a value, meaning inode_killpriv() | |
293 | * is required, 0 otherwise, meaning inode_killpriv() is not required. | |
294 | */ | |
295 | int cap_inode_need_killpriv(struct dentry *dentry) | |
296 | { | |
297 | struct inode *inode = d_backing_inode(dentry); | |
298 | int error; | |
299 | ||
300 | error = __vfs_getxattr(dentry, inode, XATTR_NAME_CAPS, NULL, 0); | |
301 | return error > 0; | |
302 | } | |
303 | ||
304 | /** | |
305 | * cap_inode_killpriv - Erase the security markings on an inode | |
306 | * | |
307 | * @mnt_userns: user namespace of the mount the inode was found from | |
308 | * @dentry: The inode/dentry to alter | |
309 | * | |
310 | * Erase the privilege-enhancing security markings on an inode. | |
311 | * | |
312 | * If the inode has been found through an idmapped mount the user namespace of | |
313 | * the vfsmount must be passed through @mnt_userns. This function will then | |
314 | * take care to map the inode according to @mnt_userns before checking | |
315 | * permissions. On non-idmapped mounts or if permission checking is to be | |
316 | * performed on the raw inode simply passs init_user_ns. | |
317 | * | |
318 | * Return: 0 if successful, -ve on error. | |
319 | */ | |
320 | int cap_inode_killpriv(struct user_namespace *mnt_userns, struct dentry *dentry) | |
321 | { | |
322 | int error; | |
323 | ||
324 | error = __vfs_removexattr(mnt_userns, dentry, XATTR_NAME_CAPS); | |
325 | if (error == -EOPNOTSUPP) | |
326 | error = 0; | |
327 | return error; | |
328 | } | |
329 | ||
330 | static bool rootid_owns_currentns(kuid_t kroot) | |
331 | { | |
332 | struct user_namespace *ns; | |
333 | ||
334 | if (!uid_valid(kroot)) | |
335 | return false; | |
336 | ||
337 | for (ns = current_user_ns(); ; ns = ns->parent) { | |
338 | if (from_kuid(ns, kroot) == 0) | |
339 | return true; | |
340 | if (ns == &init_user_ns) | |
341 | break; | |
342 | } | |
343 | ||
344 | return false; | |
345 | } | |
346 | ||
347 | static __u32 sansflags(__u32 m) | |
348 | { | |
349 | return m & ~VFS_CAP_FLAGS_EFFECTIVE; | |
350 | } | |
351 | ||
352 | static bool is_v2header(size_t size, const struct vfs_cap_data *cap) | |
353 | { | |
354 | if (size != XATTR_CAPS_SZ_2) | |
355 | return false; | |
356 | return sansflags(le32_to_cpu(cap->magic_etc)) == VFS_CAP_REVISION_2; | |
357 | } | |
358 | ||
359 | static bool is_v3header(size_t size, const struct vfs_cap_data *cap) | |
360 | { | |
361 | if (size != XATTR_CAPS_SZ_3) | |
362 | return false; | |
363 | return sansflags(le32_to_cpu(cap->magic_etc)) == VFS_CAP_REVISION_3; | |
364 | } | |
365 | ||
366 | /* | |
367 | * getsecurity: We are called for security.* before any attempt to read the | |
368 | * xattr from the inode itself. | |
369 | * | |
370 | * This gives us a chance to read the on-disk value and convert it. If we | |
371 | * return -EOPNOTSUPP, then vfs_getxattr() will call the i_op handler. | |
372 | * | |
373 | * Note we are not called by vfs_getxattr_alloc(), but that is only called | |
374 | * by the integrity subsystem, which really wants the unconverted values - | |
375 | * so that's good. | |
376 | */ | |
377 | int cap_inode_getsecurity(struct user_namespace *mnt_userns, | |
378 | struct inode *inode, const char *name, void **buffer, | |
379 | bool alloc) | |
380 | { | |
381 | int size, ret; | |
382 | kuid_t kroot; | |
383 | u32 nsmagic, magic; | |
384 | uid_t root, mappedroot; | |
385 | char *tmpbuf = NULL; | |
386 | struct vfs_cap_data *cap; | |
387 | struct vfs_ns_cap_data *nscap = NULL; | |
388 | struct dentry *dentry; | |
389 | struct user_namespace *fs_ns; | |
390 | ||
391 | if (strcmp(name, "capability") != 0) | |
392 | return -EOPNOTSUPP; | |
393 | ||
394 | dentry = d_find_any_alias(inode); | |
395 | if (!dentry) | |
396 | return -EINVAL; | |
397 | ||
398 | size = sizeof(struct vfs_ns_cap_data); | |
399 | ret = (int)vfs_getxattr_alloc(mnt_userns, dentry, XATTR_NAME_CAPS, | |
400 | &tmpbuf, size, GFP_NOFS); | |
401 | dput(dentry); | |
402 | ||
403 | if (ret < 0 || !tmpbuf) | |
404 | return ret; | |
405 | ||
406 | fs_ns = inode->i_sb->s_user_ns; | |
407 | cap = (struct vfs_cap_data *) tmpbuf; | |
408 | if (is_v2header((size_t) ret, cap)) { | |
409 | root = 0; | |
410 | } else if (is_v3header((size_t) ret, cap)) { | |
411 | nscap = (struct vfs_ns_cap_data *) tmpbuf; | |
412 | root = le32_to_cpu(nscap->rootid); | |
413 | } else { | |
414 | size = -EINVAL; | |
415 | goto out_free; | |
416 | } | |
417 | ||
418 | kroot = make_kuid(fs_ns, root); | |
419 | ||
420 | /* If this is an idmapped mount shift the kuid. */ | |
421 | kroot = kuid_into_mnt(mnt_userns, kroot); | |
422 | ||
423 | /* If the root kuid maps to a valid uid in current ns, then return | |
424 | * this as a nscap. */ | |
425 | mappedroot = from_kuid(current_user_ns(), kroot); | |
426 | if (mappedroot != (uid_t)-1 && mappedroot != (uid_t)0) { | |
427 | size = sizeof(struct vfs_ns_cap_data); | |
428 | if (alloc) { | |
429 | if (!nscap) { | |
430 | /* v2 -> v3 conversion */ | |
431 | nscap = kzalloc(size, GFP_ATOMIC); | |
432 | if (!nscap) { | |
433 | size = -ENOMEM; | |
434 | goto out_free; | |
435 | } | |
436 | nsmagic = VFS_CAP_REVISION_3; | |
437 | magic = le32_to_cpu(cap->magic_etc); | |
438 | if (magic & VFS_CAP_FLAGS_EFFECTIVE) | |
439 | nsmagic |= VFS_CAP_FLAGS_EFFECTIVE; | |
440 | memcpy(&nscap->data, &cap->data, sizeof(__le32) * 2 * VFS_CAP_U32); | |
441 | nscap->magic_etc = cpu_to_le32(nsmagic); | |
442 | } else { | |
443 | /* use allocated v3 buffer */ | |
444 | tmpbuf = NULL; | |
445 | } | |
446 | nscap->rootid = cpu_to_le32(mappedroot); | |
447 | *buffer = nscap; | |
448 | } | |
449 | goto out_free; | |
450 | } | |
451 | ||
452 | if (!rootid_owns_currentns(kroot)) { | |
453 | size = -EOVERFLOW; | |
454 | goto out_free; | |
455 | } | |
456 | ||
457 | /* This comes from a parent namespace. Return as a v2 capability */ | |
458 | size = sizeof(struct vfs_cap_data); | |
459 | if (alloc) { | |
460 | if (nscap) { | |
461 | /* v3 -> v2 conversion */ | |
462 | cap = kzalloc(size, GFP_ATOMIC); | |
463 | if (!cap) { | |
464 | size = -ENOMEM; | |
465 | goto out_free; | |
466 | } | |
467 | magic = VFS_CAP_REVISION_2; | |
468 | nsmagic = le32_to_cpu(nscap->magic_etc); | |
469 | if (nsmagic & VFS_CAP_FLAGS_EFFECTIVE) | |
470 | magic |= VFS_CAP_FLAGS_EFFECTIVE; | |
471 | memcpy(&cap->data, &nscap->data, sizeof(__le32) * 2 * VFS_CAP_U32); | |
472 | cap->magic_etc = cpu_to_le32(magic); | |
473 | } else { | |
474 | /* use unconverted v2 */ | |
475 | tmpbuf = NULL; | |
476 | } | |
477 | *buffer = cap; | |
478 | } | |
479 | out_free: | |
480 | kfree(tmpbuf); | |
481 | return size; | |
482 | } | |
483 | ||
484 | /** | |
485 | * rootid_from_xattr - translate root uid of vfs caps | |
486 | * | |
487 | * @value: vfs caps value which may be modified by this function | |
488 | * @size: size of @ivalue | |
489 | * @task_ns: user namespace of the caller | |
490 | * @mnt_userns: user namespace of the mount the inode was found from | |
491 | * | |
492 | * If the inode has been found through an idmapped mount the user namespace of | |
493 | * the vfsmount must be passed through @mnt_userns. This function will then | |
494 | * take care to map the inode according to @mnt_userns before checking | |
495 | * permissions. On non-idmapped mounts or if permission checking is to be | |
496 | * performed on the raw inode simply passs init_user_ns. | |
497 | */ | |
498 | static kuid_t rootid_from_xattr(const void *value, size_t size, | |
499 | struct user_namespace *task_ns, | |
500 | struct user_namespace *mnt_userns) | |
501 | { | |
502 | const struct vfs_ns_cap_data *nscap = value; | |
503 | kuid_t rootkid; | |
504 | uid_t rootid = 0; | |
505 | ||
506 | if (size == XATTR_CAPS_SZ_3) | |
507 | rootid = le32_to_cpu(nscap->rootid); | |
508 | ||
509 | rootkid = make_kuid(task_ns, rootid); | |
510 | return kuid_from_mnt(mnt_userns, rootkid); | |
511 | } | |
512 | ||
513 | static bool validheader(size_t size, const struct vfs_cap_data *cap) | |
514 | { | |
515 | return is_v2header(size, cap) || is_v3header(size, cap); | |
516 | } | |
517 | ||
518 | /** | |
519 | * cap_convert_nscap - check vfs caps | |
520 | * | |
521 | * @mnt_userns: user namespace of the mount the inode was found from | |
522 | * @dentry: used to retrieve inode to check permissions on | |
523 | * @ivalue: vfs caps value which may be modified by this function | |
524 | * @size: size of @ivalue | |
525 | * | |
526 | * User requested a write of security.capability. If needed, update the | |
527 | * xattr to change from v2 to v3, or to fixup the v3 rootid. | |
528 | * | |
529 | * If the inode has been found through an idmapped mount the user namespace of | |
530 | * the vfsmount must be passed through @mnt_userns. This function will then | |
531 | * take care to map the inode according to @mnt_userns before checking | |
532 | * permissions. On non-idmapped mounts or if permission checking is to be | |
533 | * performed on the raw inode simply passs init_user_ns. | |
534 | * | |
535 | * Return: On success, return the new size; on error, return < 0. | |
536 | */ | |
537 | int cap_convert_nscap(struct user_namespace *mnt_userns, struct dentry *dentry, | |
538 | const void **ivalue, size_t size) | |
539 | { | |
540 | struct vfs_ns_cap_data *nscap; | |
541 | uid_t nsrootid; | |
542 | const struct vfs_cap_data *cap = *ivalue; | |
543 | __u32 magic, nsmagic; | |
544 | struct inode *inode = d_backing_inode(dentry); | |
545 | struct user_namespace *task_ns = current_user_ns(), | |
546 | *fs_ns = inode->i_sb->s_user_ns; | |
547 | kuid_t rootid; | |
548 | size_t newsize; | |
549 | ||
550 | if (!*ivalue) | |
551 | return -EINVAL; | |
552 | if (!validheader(size, cap)) | |
553 | return -EINVAL; | |
554 | if (!capable_wrt_inode_uidgid(mnt_userns, inode, CAP_SETFCAP)) | |
555 | return -EPERM; | |
556 | if (size == XATTR_CAPS_SZ_2 && (mnt_userns == &init_user_ns)) | |
557 | if (ns_capable(inode->i_sb->s_user_ns, CAP_SETFCAP)) | |
558 | /* user is privileged, just write the v2 */ | |
559 | return size; | |
560 | ||
561 | rootid = rootid_from_xattr(*ivalue, size, task_ns, mnt_userns); | |
562 | if (!uid_valid(rootid)) | |
563 | return -EINVAL; | |
564 | ||
565 | nsrootid = from_kuid(fs_ns, rootid); | |
566 | if (nsrootid == -1) | |
567 | return -EINVAL; | |
568 | ||
569 | newsize = sizeof(struct vfs_ns_cap_data); | |
570 | nscap = kmalloc(newsize, GFP_ATOMIC); | |
571 | if (!nscap) | |
572 | return -ENOMEM; | |
573 | nscap->rootid = cpu_to_le32(nsrootid); | |
574 | nsmagic = VFS_CAP_REVISION_3; | |
575 | magic = le32_to_cpu(cap->magic_etc); | |
576 | if (magic & VFS_CAP_FLAGS_EFFECTIVE) | |
577 | nsmagic |= VFS_CAP_FLAGS_EFFECTIVE; | |
578 | nscap->magic_etc = cpu_to_le32(nsmagic); | |
579 | memcpy(&nscap->data, &cap->data, sizeof(__le32) * 2 * VFS_CAP_U32); | |
580 | ||
581 | *ivalue = nscap; | |
582 | return newsize; | |
583 | } | |
584 | ||
585 | /* | |
586 | * Calculate the new process capability sets from the capability sets attached | |
587 | * to a file. | |
588 | */ | |
589 | static inline int bprm_caps_from_vfs_caps(struct cpu_vfs_cap_data *caps, | |
590 | struct linux_binprm *bprm, | |
591 | bool *effective, | |
592 | bool *has_fcap) | |
593 | { | |
594 | struct cred *new = bprm->cred; | |
595 | unsigned i; | |
596 | int ret = 0; | |
597 | ||
598 | if (caps->magic_etc & VFS_CAP_FLAGS_EFFECTIVE) | |
599 | *effective = true; | |
600 | ||
601 | if (caps->magic_etc & VFS_CAP_REVISION_MASK) | |
602 | *has_fcap = true; | |
603 | ||
604 | CAP_FOR_EACH_U32(i) { | |
605 | __u32 permitted = caps->permitted.cap[i]; | |
606 | __u32 inheritable = caps->inheritable.cap[i]; | |
607 | ||
608 | /* | |
609 | * pP' = (X & fP) | (pI & fI) | |
610 | * The addition of pA' is handled later. | |
611 | */ | |
612 | new->cap_permitted.cap[i] = | |
613 | (new->cap_bset.cap[i] & permitted) | | |
614 | (new->cap_inheritable.cap[i] & inheritable); | |
615 | ||
616 | if (permitted & ~new->cap_permitted.cap[i]) | |
617 | /* insufficient to execute correctly */ | |
618 | ret = -EPERM; | |
619 | } | |
620 | ||
621 | /* | |
622 | * For legacy apps, with no internal support for recognizing they | |
623 | * do not have enough capabilities, we return an error if they are | |
624 | * missing some "forced" (aka file-permitted) capabilities. | |
625 | */ | |
626 | return *effective ? ret : 0; | |
627 | } | |
628 | ||
629 | /** | |
630 | * get_vfs_caps_from_disk - retrieve vfs caps from disk | |
631 | * | |
632 | * @mnt_userns: user namespace of the mount the inode was found from | |
633 | * @dentry: dentry from which @inode is retrieved | |
634 | * @cpu_caps: vfs capabilities | |
635 | * | |
636 | * Extract the on-exec-apply capability sets for an executable file. | |
637 | * | |
638 | * If the inode has been found through an idmapped mount the user namespace of | |
639 | * the vfsmount must be passed through @mnt_userns. This function will then | |
640 | * take care to map the inode according to @mnt_userns before checking | |
641 | * permissions. On non-idmapped mounts or if permission checking is to be | |
642 | * performed on the raw inode simply passs init_user_ns. | |
643 | */ | |
644 | int get_vfs_caps_from_disk(struct user_namespace *mnt_userns, | |
645 | const struct dentry *dentry, | |
646 | struct cpu_vfs_cap_data *cpu_caps) | |
647 | { | |
648 | struct inode *inode = d_backing_inode(dentry); | |
649 | __u32 magic_etc; | |
650 | unsigned tocopy, i; | |
651 | int size; | |
652 | struct vfs_ns_cap_data data, *nscaps = &data; | |
653 | struct vfs_cap_data *caps = (struct vfs_cap_data *) &data; | |
654 | kuid_t rootkuid; | |
655 | struct user_namespace *fs_ns; | |
656 | ||
657 | memset(cpu_caps, 0, sizeof(struct cpu_vfs_cap_data)); | |
658 | ||
659 | if (!inode) | |
660 | return -ENODATA; | |
661 | ||
662 | fs_ns = inode->i_sb->s_user_ns; | |
663 | size = __vfs_getxattr((struct dentry *)dentry, inode, | |
664 | XATTR_NAME_CAPS, &data, XATTR_CAPS_SZ); | |
665 | if (size == -ENODATA || size == -EOPNOTSUPP) | |
666 | /* no data, that's ok */ | |
667 | return -ENODATA; | |
668 | ||
669 | if (size < 0) | |
670 | return size; | |
671 | ||
672 | if (size < sizeof(magic_etc)) | |
673 | return -EINVAL; | |
674 | ||
675 | cpu_caps->magic_etc = magic_etc = le32_to_cpu(caps->magic_etc); | |
676 | ||
677 | rootkuid = make_kuid(fs_ns, 0); | |
678 | switch (magic_etc & VFS_CAP_REVISION_MASK) { | |
679 | case VFS_CAP_REVISION_1: | |
680 | if (size != XATTR_CAPS_SZ_1) | |
681 | return -EINVAL; | |
682 | tocopy = VFS_CAP_U32_1; | |
683 | break; | |
684 | case VFS_CAP_REVISION_2: | |
685 | if (size != XATTR_CAPS_SZ_2) | |
686 | return -EINVAL; | |
687 | tocopy = VFS_CAP_U32_2; | |
688 | break; | |
689 | case VFS_CAP_REVISION_3: | |
690 | if (size != XATTR_CAPS_SZ_3) | |
691 | return -EINVAL; | |
692 | tocopy = VFS_CAP_U32_3; | |
693 | rootkuid = make_kuid(fs_ns, le32_to_cpu(nscaps->rootid)); | |
694 | break; | |
695 | ||
696 | default: | |
697 | return -EINVAL; | |
698 | } | |
699 | /* Limit the caps to the mounter of the filesystem | |
700 | * or the more limited uid specified in the xattr. | |
701 | */ | |
702 | rootkuid = kuid_into_mnt(mnt_userns, rootkuid); | |
703 | if (!rootid_owns_currentns(rootkuid)) | |
704 | return -ENODATA; | |
705 | ||
706 | CAP_FOR_EACH_U32(i) { | |
707 | if (i >= tocopy) | |
708 | break; | |
709 | cpu_caps->permitted.cap[i] = le32_to_cpu(caps->data[i].permitted); | |
710 | cpu_caps->inheritable.cap[i] = le32_to_cpu(caps->data[i].inheritable); | |
711 | } | |
712 | ||
713 | cpu_caps->permitted.cap[CAP_LAST_U32] &= CAP_LAST_U32_VALID_MASK; | |
714 | cpu_caps->inheritable.cap[CAP_LAST_U32] &= CAP_LAST_U32_VALID_MASK; | |
715 | ||
716 | cpu_caps->rootid = rootkuid; | |
717 | ||
718 | return 0; | |
719 | } | |
720 | ||
721 | /* | |
722 | * Attempt to get the on-exec apply capability sets for an executable file from | |
723 | * its xattrs and, if present, apply them to the proposed credentials being | |
724 | * constructed by execve(). | |
725 | */ | |
726 | static int get_file_caps(struct linux_binprm *bprm, struct file *file, | |
727 | bool *effective, bool *has_fcap) | |
728 | { | |
729 | int rc = 0; | |
730 | struct cpu_vfs_cap_data vcaps; | |
731 | ||
732 | cap_clear(bprm->cred->cap_permitted); | |
733 | ||
734 | if (!file_caps_enabled) | |
735 | return 0; | |
736 | ||
737 | if (!mnt_may_suid(file->f_path.mnt)) | |
738 | return 0; | |
739 | ||
740 | /* | |
741 | * This check is redundant with mnt_may_suid() but is kept to make | |
742 | * explicit that capability bits are limited to s_user_ns and its | |
743 | * descendants. | |
744 | */ | |
745 | if (!current_in_userns(file->f_path.mnt->mnt_sb->s_user_ns)) | |
746 | return 0; | |
747 | ||
748 | rc = get_vfs_caps_from_disk(file_mnt_user_ns(file), | |
749 | file->f_path.dentry, &vcaps); | |
750 | if (rc < 0) { | |
751 | if (rc == -EINVAL) | |
752 | printk(KERN_NOTICE "Invalid argument reading file caps for %s\n", | |
753 | bprm->filename); | |
754 | else if (rc == -ENODATA) | |
755 | rc = 0; | |
756 | goto out; | |
757 | } | |
758 | ||
759 | rc = bprm_caps_from_vfs_caps(&vcaps, bprm, effective, has_fcap); | |
760 | ||
761 | out: | |
762 | if (rc) | |
763 | cap_clear(bprm->cred->cap_permitted); | |
764 | ||
765 | return rc; | |
766 | } | |
767 | ||
768 | static inline bool root_privileged(void) { return !issecure(SECURE_NOROOT); } | |
769 | ||
770 | static inline bool __is_real(kuid_t uid, struct cred *cred) | |
771 | { return uid_eq(cred->uid, uid); } | |
772 | ||
773 | static inline bool __is_eff(kuid_t uid, struct cred *cred) | |
774 | { return uid_eq(cred->euid, uid); } | |
775 | ||
776 | static inline bool __is_suid(kuid_t uid, struct cred *cred) | |
777 | { return !__is_real(uid, cred) && __is_eff(uid, cred); } | |
778 | ||
779 | /* | |
780 | * handle_privileged_root - Handle case of privileged root | |
781 | * @bprm: The execution parameters, including the proposed creds | |
782 | * @has_fcap: Are any file capabilities set? | |
783 | * @effective: Do we have effective root privilege? | |
784 | * @root_uid: This namespace' root UID WRT initial USER namespace | |
785 | * | |
786 | * Handle the case where root is privileged and hasn't been neutered by | |
787 | * SECURE_NOROOT. If file capabilities are set, they won't be combined with | |
788 | * set UID root and nothing is changed. If we are root, cap_permitted is | |
789 | * updated. If we have become set UID root, the effective bit is set. | |
790 | */ | |
791 | static void handle_privileged_root(struct linux_binprm *bprm, bool has_fcap, | |
792 | bool *effective, kuid_t root_uid) | |
793 | { | |
794 | const struct cred *old = current_cred(); | |
795 | struct cred *new = bprm->cred; | |
796 | ||
797 | if (!root_privileged()) | |
798 | return; | |
799 | /* | |
800 | * If the legacy file capability is set, then don't set privs | |
801 | * for a setuid root binary run by a non-root user. Do set it | |
802 | * for a root user just to cause least surprise to an admin. | |
803 | */ | |
804 | if (has_fcap && __is_suid(root_uid, new)) { | |
805 | warn_setuid_and_fcaps_mixed(bprm->filename); | |
806 | return; | |
807 | } | |
808 | /* | |
809 | * To support inheritance of root-permissions and suid-root | |
810 | * executables under compatibility mode, we override the | |
811 | * capability sets for the file. | |
812 | */ | |
813 | if (__is_eff(root_uid, new) || __is_real(root_uid, new)) { | |
814 | /* pP' = (cap_bset & ~0) | (pI & ~0) */ | |
815 | new->cap_permitted = cap_combine(old->cap_bset, | |
816 | old->cap_inheritable); | |
817 | } | |
818 | /* | |
819 | * If only the real uid is 0, we do not set the effective bit. | |
820 | */ | |
821 | if (__is_eff(root_uid, new)) | |
822 | *effective = true; | |
823 | } | |
824 | ||
825 | #define __cap_gained(field, target, source) \ | |
826 | !cap_issubset(target->cap_##field, source->cap_##field) | |
827 | #define __cap_grew(target, source, cred) \ | |
828 | !cap_issubset(cred->cap_##target, cred->cap_##source) | |
829 | #define __cap_full(field, cred) \ | |
830 | cap_issubset(CAP_FULL_SET, cred->cap_##field) | |
831 | ||
832 | static inline bool __is_setuid(struct cred *new, const struct cred *old) | |
833 | { return !uid_eq(new->euid, old->uid); } | |
834 | ||
835 | static inline bool __is_setgid(struct cred *new, const struct cred *old) | |
836 | { return !gid_eq(new->egid, old->gid); } | |
837 | ||
838 | /* | |
839 | * 1) Audit candidate if current->cap_effective is set | |
840 | * | |
841 | * We do not bother to audit if 3 things are true: | |
842 | * 1) cap_effective has all caps | |
843 | * 2) we became root *OR* are were already root | |
844 | * 3) root is supposed to have all caps (SECURE_NOROOT) | |
845 | * Since this is just a normal root execing a process. | |
846 | * | |
847 | * Number 1 above might fail if you don't have a full bset, but I think | |
848 | * that is interesting information to audit. | |
849 | * | |
850 | * A number of other conditions require logging: | |
851 | * 2) something prevented setuid root getting all caps | |
852 | * 3) non-setuid root gets fcaps | |
853 | * 4) non-setuid root gets ambient | |
854 | */ | |
855 | static inline bool nonroot_raised_pE(struct cred *new, const struct cred *old, | |
856 | kuid_t root, bool has_fcap) | |
857 | { | |
858 | bool ret = false; | |
859 | ||
860 | if ((__cap_grew(effective, ambient, new) && | |
861 | !(__cap_full(effective, new) && | |
862 | (__is_eff(root, new) || __is_real(root, new)) && | |
863 | root_privileged())) || | |
864 | (root_privileged() && | |
865 | __is_suid(root, new) && | |
866 | !__cap_full(effective, new)) || | |
867 | (!__is_setuid(new, old) && | |
868 | ((has_fcap && | |
869 | __cap_gained(permitted, new, old)) || | |
870 | __cap_gained(ambient, new, old)))) | |
871 | ||
872 | ret = true; | |
873 | ||
874 | return ret; | |
875 | } | |
876 | ||
877 | /** | |
878 | * cap_bprm_creds_from_file - Set up the proposed credentials for execve(). | |
879 | * @bprm: The execution parameters, including the proposed creds | |
880 | * @file: The file to pull the credentials from | |
881 | * | |
882 | * Set up the proposed credentials for a new execution context being | |
883 | * constructed by execve(). The proposed creds in @bprm->cred is altered, | |
884 | * which won't take effect immediately. | |
885 | * | |
886 | * Return: 0 if successful, -ve on error. | |
887 | */ | |
888 | int cap_bprm_creds_from_file(struct linux_binprm *bprm, struct file *file) | |
889 | { | |
890 | /* Process setpcap binaries and capabilities for uid 0 */ | |
891 | const struct cred *old = current_cred(); | |
892 | struct cred *new = bprm->cred; | |
893 | bool effective = false, has_fcap = false, is_setid; | |
894 | int ret; | |
895 | kuid_t root_uid; | |
896 | ||
897 | if (WARN_ON(!cap_ambient_invariant_ok(old))) | |
898 | return -EPERM; | |
899 | ||
900 | ret = get_file_caps(bprm, file, &effective, &has_fcap); | |
901 | if (ret < 0) | |
902 | return ret; | |
903 | ||
904 | root_uid = make_kuid(new->user_ns, 0); | |
905 | ||
906 | handle_privileged_root(bprm, has_fcap, &effective, root_uid); | |
907 | ||
908 | /* if we have fs caps, clear dangerous personality flags */ | |
909 | if (__cap_gained(permitted, new, old)) | |
910 | bprm->per_clear |= PER_CLEAR_ON_SETID; | |
911 | ||
912 | /* Don't let someone trace a set[ug]id/setpcap binary with the revised | |
913 | * credentials unless they have the appropriate permit. | |
914 | * | |
915 | * In addition, if NO_NEW_PRIVS, then ensure we get no new privs. | |
916 | */ | |
917 | is_setid = __is_setuid(new, old) || __is_setgid(new, old); | |
918 | ||
919 | if ((is_setid || __cap_gained(permitted, new, old)) && | |
920 | ((bprm->unsafe & ~LSM_UNSAFE_PTRACE) || | |
921 | !ptracer_capable(current, new->user_ns))) { | |
922 | /* downgrade; they get no more than they had, and maybe less */ | |
923 | if (!ns_capable(new->user_ns, CAP_SETUID) || | |
924 | (bprm->unsafe & LSM_UNSAFE_NO_NEW_PRIVS)) { | |
925 | new->euid = new->uid; | |
926 | new->egid = new->gid; | |
927 | } | |
928 | new->cap_permitted = cap_intersect(new->cap_permitted, | |
929 | old->cap_permitted); | |
930 | } | |
931 | ||
932 | new->suid = new->fsuid = new->euid; | |
933 | new->sgid = new->fsgid = new->egid; | |
934 | ||
935 | /* File caps or setid cancels ambient. */ | |
936 | if (has_fcap || is_setid) | |
937 | cap_clear(new->cap_ambient); | |
938 | ||
939 | /* | |
940 | * Now that we've computed pA', update pP' to give: | |
941 | * pP' = (X & fP) | (pI & fI) | pA' | |
942 | */ | |
943 | new->cap_permitted = cap_combine(new->cap_permitted, new->cap_ambient); | |
944 | ||
945 | /* | |
946 | * Set pE' = (fE ? pP' : pA'). Because pA' is zero if fE is set, | |
947 | * this is the same as pE' = (fE ? pP' : 0) | pA'. | |
948 | */ | |
949 | if (effective) | |
950 | new->cap_effective = new->cap_permitted; | |
951 | else | |
952 | new->cap_effective = new->cap_ambient; | |
953 | ||
954 | if (WARN_ON(!cap_ambient_invariant_ok(new))) | |
955 | return -EPERM; | |
956 | ||
957 | if (nonroot_raised_pE(new, old, root_uid, has_fcap)) { | |
958 | ret = audit_log_bprm_fcaps(bprm, new, old); | |
959 | if (ret < 0) | |
960 | return ret; | |
961 | } | |
962 | ||
963 | new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS); | |
964 | ||
965 | if (WARN_ON(!cap_ambient_invariant_ok(new))) | |
966 | return -EPERM; | |
967 | ||
968 | /* Check for privilege-elevated exec. */ | |
969 | if (is_setid || | |
970 | (!__is_real(root_uid, new) && | |
971 | (effective || | |
972 | __cap_grew(permitted, ambient, new)))) | |
973 | bprm->secureexec = 1; | |
974 | ||
975 | return 0; | |
976 | } | |
977 | ||
978 | /** | |
979 | * cap_inode_setxattr - Determine whether an xattr may be altered | |
980 | * @dentry: The inode/dentry being altered | |
981 | * @name: The name of the xattr to be changed | |
982 | * @value: The value that the xattr will be changed to | |
983 | * @size: The size of value | |
984 | * @flags: The replacement flag | |
985 | * | |
986 | * Determine whether an xattr may be altered or set on an inode, returning 0 if | |
987 | * permission is granted, -ve if denied. | |
988 | * | |
989 | * This is used to make sure security xattrs don't get updated or set by those | |
990 | * who aren't privileged to do so. | |
991 | */ | |
992 | int cap_inode_setxattr(struct dentry *dentry, const char *name, | |
993 | const void *value, size_t size, int flags) | |
994 | { | |
995 | struct user_namespace *user_ns = dentry->d_sb->s_user_ns; | |
996 | ||
997 | /* Ignore non-security xattrs */ | |
998 | if (strncmp(name, XATTR_SECURITY_PREFIX, | |
999 | XATTR_SECURITY_PREFIX_LEN) != 0) | |
1000 | return 0; | |
1001 | ||
1002 | /* | |
1003 | * For XATTR_NAME_CAPS the check will be done in | |
1004 | * cap_convert_nscap(), called by setxattr() | |
1005 | */ | |
1006 | if (strcmp(name, XATTR_NAME_CAPS) == 0) | |
1007 | return 0; | |
1008 | ||
1009 | if (!ns_capable(user_ns, CAP_SYS_ADMIN)) | |
1010 | return -EPERM; | |
1011 | return 0; | |
1012 | } | |
1013 | ||
1014 | /** | |
1015 | * cap_inode_removexattr - Determine whether an xattr may be removed | |
1016 | * | |
1017 | * @mnt_userns: User namespace of the mount the inode was found from | |
1018 | * @dentry: The inode/dentry being altered | |
1019 | * @name: The name of the xattr to be changed | |
1020 | * | |
1021 | * Determine whether an xattr may be removed from an inode, returning 0 if | |
1022 | * permission is granted, -ve if denied. | |
1023 | * | |
1024 | * If the inode has been found through an idmapped mount the user namespace of | |
1025 | * the vfsmount must be passed through @mnt_userns. This function will then | |
1026 | * take care to map the inode according to @mnt_userns before checking | |
1027 | * permissions. On non-idmapped mounts or if permission checking is to be | |
1028 | * performed on the raw inode simply passs init_user_ns. | |
1029 | * | |
1030 | * This is used to make sure security xattrs don't get removed by those who | |
1031 | * aren't privileged to remove them. | |
1032 | */ | |
1033 | int cap_inode_removexattr(struct user_namespace *mnt_userns, | |
1034 | struct dentry *dentry, const char *name) | |
1035 | { | |
1036 | struct user_namespace *user_ns = dentry->d_sb->s_user_ns; | |
1037 | ||
1038 | /* Ignore non-security xattrs */ | |
1039 | if (strncmp(name, XATTR_SECURITY_PREFIX, | |
1040 | XATTR_SECURITY_PREFIX_LEN) != 0) | |
1041 | return 0; | |
1042 | ||
1043 | if (strcmp(name, XATTR_NAME_CAPS) == 0) { | |
1044 | /* security.capability gets namespaced */ | |
1045 | struct inode *inode = d_backing_inode(dentry); | |
1046 | if (!inode) | |
1047 | return -EINVAL; | |
1048 | if (!capable_wrt_inode_uidgid(mnt_userns, inode, CAP_SETFCAP)) | |
1049 | return -EPERM; | |
1050 | return 0; | |
1051 | } | |
1052 | ||
1053 | if (!ns_capable(user_ns, CAP_SYS_ADMIN)) | |
1054 | return -EPERM; | |
1055 | return 0; | |
1056 | } | |
1057 | ||
1058 | /* | |
1059 | * cap_emulate_setxuid() fixes the effective / permitted capabilities of | |
1060 | * a process after a call to setuid, setreuid, or setresuid. | |
1061 | * | |
1062 | * 1) When set*uiding _from_ one of {r,e,s}uid == 0 _to_ all of | |
1063 | * {r,e,s}uid != 0, the permitted and effective capabilities are | |
1064 | * cleared. | |
1065 | * | |
1066 | * 2) When set*uiding _from_ euid == 0 _to_ euid != 0, the effective | |
1067 | * capabilities of the process are cleared. | |
1068 | * | |
1069 | * 3) When set*uiding _from_ euid != 0 _to_ euid == 0, the effective | |
1070 | * capabilities are set to the permitted capabilities. | |
1071 | * | |
1072 | * fsuid is handled elsewhere. fsuid == 0 and {r,e,s}uid!= 0 should | |
1073 | * never happen. | |
1074 | * | |
1075 | * -astor | |
1076 | * | |
1077 | * cevans - New behaviour, Oct '99 | |
1078 | * A process may, via prctl(), elect to keep its capabilities when it | |
1079 | * calls setuid() and switches away from uid==0. Both permitted and | |
1080 | * effective sets will be retained. | |
1081 | * Without this change, it was impossible for a daemon to drop only some | |
1082 | * of its privilege. The call to setuid(!=0) would drop all privileges! | |
1083 | * Keeping uid 0 is not an option because uid 0 owns too many vital | |
1084 | * files.. | |
1085 | * Thanks to Olaf Kirch and Peter Benie for spotting this. | |
1086 | */ | |
1087 | static inline void cap_emulate_setxuid(struct cred *new, const struct cred *old) | |
1088 | { | |
1089 | kuid_t root_uid = make_kuid(old->user_ns, 0); | |
1090 | ||
1091 | if ((uid_eq(old->uid, root_uid) || | |
1092 | uid_eq(old->euid, root_uid) || | |
1093 | uid_eq(old->suid, root_uid)) && | |
1094 | (!uid_eq(new->uid, root_uid) && | |
1095 | !uid_eq(new->euid, root_uid) && | |
1096 | !uid_eq(new->suid, root_uid))) { | |
1097 | if (!issecure(SECURE_KEEP_CAPS)) { | |
1098 | cap_clear(new->cap_permitted); | |
1099 | cap_clear(new->cap_effective); | |
1100 | } | |
1101 | ||
1102 | /* | |
1103 | * Pre-ambient programs expect setresuid to nonroot followed | |
1104 | * by exec to drop capabilities. We should make sure that | |
1105 | * this remains the case. | |
1106 | */ | |
1107 | cap_clear(new->cap_ambient); | |
1108 | } | |
1109 | if (uid_eq(old->euid, root_uid) && !uid_eq(new->euid, root_uid)) | |
1110 | cap_clear(new->cap_effective); | |
1111 | if (!uid_eq(old->euid, root_uid) && uid_eq(new->euid, root_uid)) | |
1112 | new->cap_effective = new->cap_permitted; | |
1113 | } | |
1114 | ||
1115 | /** | |
1116 | * cap_task_fix_setuid - Fix up the results of setuid() call | |
1117 | * @new: The proposed credentials | |
1118 | * @old: The current task's current credentials | |
1119 | * @flags: Indications of what has changed | |
1120 | * | |
1121 | * Fix up the results of setuid() call before the credential changes are | |
1122 | * actually applied. | |
1123 | * | |
1124 | * Return: 0 to grant the changes, -ve to deny them. | |
1125 | */ | |
1126 | int cap_task_fix_setuid(struct cred *new, const struct cred *old, int flags) | |
1127 | { | |
1128 | switch (flags) { | |
1129 | case LSM_SETID_RE: | |
1130 | case LSM_SETID_ID: | |
1131 | case LSM_SETID_RES: | |
1132 | /* juggle the capabilities to follow [RES]UID changes unless | |
1133 | * otherwise suppressed */ | |
1134 | if (!issecure(SECURE_NO_SETUID_FIXUP)) | |
1135 | cap_emulate_setxuid(new, old); | |
1136 | break; | |
1137 | ||
1138 | case LSM_SETID_FS: | |
1139 | /* juggle the capabilties to follow FSUID changes, unless | |
1140 | * otherwise suppressed | |
1141 | * | |
1142 | * FIXME - is fsuser used for all CAP_FS_MASK capabilities? | |
1143 | * if not, we might be a bit too harsh here. | |
1144 | */ | |
1145 | if (!issecure(SECURE_NO_SETUID_FIXUP)) { | |
1146 | kuid_t root_uid = make_kuid(old->user_ns, 0); | |
1147 | if (uid_eq(old->fsuid, root_uid) && !uid_eq(new->fsuid, root_uid)) | |
1148 | new->cap_effective = | |
1149 | cap_drop_fs_set(new->cap_effective); | |
1150 | ||
1151 | if (!uid_eq(old->fsuid, root_uid) && uid_eq(new->fsuid, root_uid)) | |
1152 | new->cap_effective = | |
1153 | cap_raise_fs_set(new->cap_effective, | |
1154 | new->cap_permitted); | |
1155 | } | |
1156 | break; | |
1157 | ||
1158 | default: | |
1159 | return -EINVAL; | |
1160 | } | |
1161 | ||
1162 | return 0; | |
1163 | } | |
1164 | ||
1165 | /* | |
1166 | * Rationale: code calling task_setscheduler, task_setioprio, and | |
1167 | * task_setnice, assumes that | |
1168 | * . if capable(cap_sys_nice), then those actions should be allowed | |
1169 | * . if not capable(cap_sys_nice), but acting on your own processes, | |
1170 | * then those actions should be allowed | |
1171 | * This is insufficient now since you can call code without suid, but | |
1172 | * yet with increased caps. | |
1173 | * So we check for increased caps on the target process. | |
1174 | */ | |
1175 | static int cap_safe_nice(struct task_struct *p) | |
1176 | { | |
1177 | int is_subset, ret = 0; | |
1178 | ||
1179 | rcu_read_lock(); | |
1180 | is_subset = cap_issubset(__task_cred(p)->cap_permitted, | |
1181 | current_cred()->cap_permitted); | |
1182 | if (!is_subset && !ns_capable(__task_cred(p)->user_ns, CAP_SYS_NICE)) | |
1183 | ret = -EPERM; | |
1184 | rcu_read_unlock(); | |
1185 | ||
1186 | return ret; | |
1187 | } | |
1188 | ||
1189 | /** | |
1190 | * cap_task_setscheduler - Detemine if scheduler policy change is permitted | |
1191 | * @p: The task to affect | |
1192 | * | |
1193 | * Detemine if the requested scheduler policy change is permitted for the | |
1194 | * specified task. | |
1195 | * | |
1196 | * Return: 0 if permission is granted, -ve if denied. | |
1197 | */ | |
1198 | int cap_task_setscheduler(struct task_struct *p) | |
1199 | { | |
1200 | return cap_safe_nice(p); | |
1201 | } | |
1202 | ||
1203 | /** | |
1204 | * cap_task_setioprio - Detemine if I/O priority change is permitted | |
1205 | * @p: The task to affect | |
1206 | * @ioprio: The I/O priority to set | |
1207 | * | |
1208 | * Detemine if the requested I/O priority change is permitted for the specified | |
1209 | * task. | |
1210 | * | |
1211 | * Return: 0 if permission is granted, -ve if denied. | |
1212 | */ | |
1213 | int cap_task_setioprio(struct task_struct *p, int ioprio) | |
1214 | { | |
1215 | return cap_safe_nice(p); | |
1216 | } | |
1217 | ||
1218 | /** | |
1219 | * cap_task_setnice - Detemine if task priority change is permitted | |
1220 | * @p: The task to affect | |
1221 | * @nice: The nice value to set | |
1222 | * | |
1223 | * Detemine if the requested task priority change is permitted for the | |
1224 | * specified task. | |
1225 | * | |
1226 | * Return: 0 if permission is granted, -ve if denied. | |
1227 | */ | |
1228 | int cap_task_setnice(struct task_struct *p, int nice) | |
1229 | { | |
1230 | return cap_safe_nice(p); | |
1231 | } | |
1232 | ||
1233 | /* | |
1234 | * Implement PR_CAPBSET_DROP. Attempt to remove the specified capability from | |
1235 | * the current task's bounding set. Returns 0 on success, -ve on error. | |
1236 | */ | |
1237 | static int cap_prctl_drop(unsigned long cap) | |
1238 | { | |
1239 | struct cred *new; | |
1240 | ||
1241 | if (!ns_capable(current_user_ns(), CAP_SETPCAP)) | |
1242 | return -EPERM; | |
1243 | if (!cap_valid(cap)) | |
1244 | return -EINVAL; | |
1245 | ||
1246 | new = prepare_creds(); | |
1247 | if (!new) | |
1248 | return -ENOMEM; | |
1249 | cap_lower(new->cap_bset, cap); | |
1250 | return commit_creds(new); | |
1251 | } | |
1252 | ||
1253 | /** | |
1254 | * cap_task_prctl - Implement process control functions for this security module | |
1255 | * @option: The process control function requested | |
1256 | * @arg2: The argument data for this function | |
1257 | * @arg3: The argument data for this function | |
1258 | * @arg4: The argument data for this function | |
1259 | * @arg5: The argument data for this function | |
1260 | * | |
1261 | * Allow process control functions (sys_prctl()) to alter capabilities; may | |
1262 | * also deny access to other functions not otherwise implemented here. | |
1263 | * | |
1264 | * Return: 0 or +ve on success, -ENOSYS if this function is not implemented | |
1265 | * here, other -ve on error. If -ENOSYS is returned, sys_prctl() and other LSM | |
1266 | * modules will consider performing the function. | |
1267 | */ | |
1268 | int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3, | |
1269 | unsigned long arg4, unsigned long arg5) | |
1270 | { | |
1271 | const struct cred *old = current_cred(); | |
1272 | struct cred *new; | |
1273 | ||
1274 | switch (option) { | |
1275 | case PR_CAPBSET_READ: | |
1276 | if (!cap_valid(arg2)) | |
1277 | return -EINVAL; | |
1278 | return !!cap_raised(old->cap_bset, arg2); | |
1279 | ||
1280 | case PR_CAPBSET_DROP: | |
1281 | return cap_prctl_drop(arg2); | |
1282 | ||
1283 | /* | |
1284 | * The next four prctl's remain to assist with transitioning a | |
1285 | * system from legacy UID=0 based privilege (when filesystem | |
1286 | * capabilities are not in use) to a system using filesystem | |
1287 | * capabilities only - as the POSIX.1e draft intended. | |
1288 | * | |
1289 | * Note: | |
1290 | * | |
1291 | * PR_SET_SECUREBITS = | |
1292 | * issecure_mask(SECURE_KEEP_CAPS_LOCKED) | |
1293 | * | issecure_mask(SECURE_NOROOT) | |
1294 | * | issecure_mask(SECURE_NOROOT_LOCKED) | |
1295 | * | issecure_mask(SECURE_NO_SETUID_FIXUP) | |
1296 | * | issecure_mask(SECURE_NO_SETUID_FIXUP_LOCKED) | |
1297 | * | |
1298 | * will ensure that the current process and all of its | |
1299 | * children will be locked into a pure | |
1300 | * capability-based-privilege environment. | |
1301 | */ | |
1302 | case PR_SET_SECUREBITS: | |
1303 | if ((((old->securebits & SECURE_ALL_LOCKS) >> 1) | |
1304 | & (old->securebits ^ arg2)) /*[1]*/ | |
1305 | || ((old->securebits & SECURE_ALL_LOCKS & ~arg2)) /*[2]*/ | |
1306 | || (arg2 & ~(SECURE_ALL_LOCKS | SECURE_ALL_BITS)) /*[3]*/ | |
1307 | || (cap_capable(current_cred(), | |
1308 | current_cred()->user_ns, | |
1309 | CAP_SETPCAP, | |
1310 | CAP_OPT_NONE) != 0) /*[4]*/ | |
1311 | /* | |
1312 | * [1] no changing of bits that are locked | |
1313 | * [2] no unlocking of locks | |
1314 | * [3] no setting of unsupported bits | |
1315 | * [4] doing anything requires privilege (go read about | |
1316 | * the "sendmail capabilities bug") | |
1317 | */ | |
1318 | ) | |
1319 | /* cannot change a locked bit */ | |
1320 | return -EPERM; | |
1321 | ||
1322 | new = prepare_creds(); | |
1323 | if (!new) | |
1324 | return -ENOMEM; | |
1325 | new->securebits = arg2; | |
1326 | return commit_creds(new); | |
1327 | ||
1328 | case PR_GET_SECUREBITS: | |
1329 | return old->securebits; | |
1330 | ||
1331 | case PR_GET_KEEPCAPS: | |
1332 | return !!issecure(SECURE_KEEP_CAPS); | |
1333 | ||
1334 | case PR_SET_KEEPCAPS: | |
1335 | if (arg2 > 1) /* Note, we rely on arg2 being unsigned here */ | |
1336 | return -EINVAL; | |
1337 | if (issecure(SECURE_KEEP_CAPS_LOCKED)) | |
1338 | return -EPERM; | |
1339 | ||
1340 | new = prepare_creds(); | |
1341 | if (!new) | |
1342 | return -ENOMEM; | |
1343 | if (arg2) | |
1344 | new->securebits |= issecure_mask(SECURE_KEEP_CAPS); | |
1345 | else | |
1346 | new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS); | |
1347 | return commit_creds(new); | |
1348 | ||
1349 | case PR_CAP_AMBIENT: | |
1350 | if (arg2 == PR_CAP_AMBIENT_CLEAR_ALL) { | |
1351 | if (arg3 | arg4 | arg5) | |
1352 | return -EINVAL; | |
1353 | ||
1354 | new = prepare_creds(); | |
1355 | if (!new) | |
1356 | return -ENOMEM; | |
1357 | cap_clear(new->cap_ambient); | |
1358 | return commit_creds(new); | |
1359 | } | |
1360 | ||
1361 | if (((!cap_valid(arg3)) | arg4 | arg5)) | |
1362 | return -EINVAL; | |
1363 | ||
1364 | if (arg2 == PR_CAP_AMBIENT_IS_SET) { | |
1365 | return !!cap_raised(current_cred()->cap_ambient, arg3); | |
1366 | } else if (arg2 != PR_CAP_AMBIENT_RAISE && | |
1367 | arg2 != PR_CAP_AMBIENT_LOWER) { | |
1368 | return -EINVAL; | |
1369 | } else { | |
1370 | if (arg2 == PR_CAP_AMBIENT_RAISE && | |
1371 | (!cap_raised(current_cred()->cap_permitted, arg3) || | |
1372 | !cap_raised(current_cred()->cap_inheritable, | |
1373 | arg3) || | |
1374 | issecure(SECURE_NO_CAP_AMBIENT_RAISE))) | |
1375 | return -EPERM; | |
1376 | ||
1377 | new = prepare_creds(); | |
1378 | if (!new) | |
1379 | return -ENOMEM; | |
1380 | if (arg2 == PR_CAP_AMBIENT_RAISE) | |
1381 | cap_raise(new->cap_ambient, arg3); | |
1382 | else | |
1383 | cap_lower(new->cap_ambient, arg3); | |
1384 | return commit_creds(new); | |
1385 | } | |
1386 | ||
1387 | default: | |
1388 | /* No functionality available - continue with default */ | |
1389 | return -ENOSYS; | |
1390 | } | |
1391 | } | |
1392 | ||
1393 | /** | |
1394 | * cap_vm_enough_memory - Determine whether a new virtual mapping is permitted | |
1395 | * @mm: The VM space in which the new mapping is to be made | |
1396 | * @pages: The size of the mapping | |
1397 | * | |
1398 | * Determine whether the allocation of a new virtual mapping by the current | |
1399 | * task is permitted. | |
1400 | * | |
1401 | * Return: 1 if permission is granted, 0 if not. | |
1402 | */ | |
1403 | int cap_vm_enough_memory(struct mm_struct *mm, long pages) | |
1404 | { | |
1405 | int cap_sys_admin = 0; | |
1406 | ||
1407 | if (cap_capable(current_cred(), &init_user_ns, | |
1408 | CAP_SYS_ADMIN, CAP_OPT_NOAUDIT) == 0) | |
1409 | cap_sys_admin = 1; | |
1410 | ||
1411 | return cap_sys_admin; | |
1412 | } | |
1413 | ||
1414 | /** | |
1415 | * cap_mmap_addr - check if able to map given addr | |
1416 | * @addr: address attempting to be mapped | |
1417 | * | |
1418 | * If the process is attempting to map memory below dac_mmap_min_addr they need | |
1419 | * CAP_SYS_RAWIO. The other parameters to this function are unused by the | |
1420 | * capability security module. | |
1421 | * | |
1422 | * Return: 0 if this mapping should be allowed or -EPERM if not. | |
1423 | */ | |
1424 | int cap_mmap_addr(unsigned long addr) | |
1425 | { | |
1426 | int ret = 0; | |
1427 | ||
1428 | if (addr < dac_mmap_min_addr) { | |
1429 | ret = cap_capable(current_cred(), &init_user_ns, CAP_SYS_RAWIO, | |
1430 | CAP_OPT_NONE); | |
1431 | /* set PF_SUPERPRIV if it turns out we allow the low mmap */ | |
1432 | if (ret == 0) | |
1433 | current->flags |= PF_SUPERPRIV; | |
1434 | } | |
1435 | return ret; | |
1436 | } | |
1437 | ||
1438 | int cap_mmap_file(struct file *file, unsigned long reqprot, | |
1439 | unsigned long prot, unsigned long flags) | |
1440 | { | |
1441 | return 0; | |
1442 | } | |
1443 | ||
1444 | #ifdef CONFIG_SECURITY | |
1445 | ||
1446 | static struct lsm_id capability_lsmid __lsm_ro_after_init = { | |
1447 | .lsm = "capability", | |
1448 | .slot = LSMBLOB_NOT_NEEDED | |
1449 | }; | |
1450 | ||
1451 | static struct security_hook_list capability_hooks[] __lsm_ro_after_init = { | |
1452 | LSM_HOOK_INIT(capable, cap_capable), | |
1453 | LSM_HOOK_INIT(settime, cap_settime), | |
1454 | LSM_HOOK_INIT(ptrace_access_check, cap_ptrace_access_check), | |
1455 | LSM_HOOK_INIT(ptrace_traceme, cap_ptrace_traceme), | |
1456 | LSM_HOOK_INIT(capget, cap_capget), | |
1457 | LSM_HOOK_INIT(capset, cap_capset), | |
1458 | LSM_HOOK_INIT(bprm_creds_from_file, cap_bprm_creds_from_file), | |
1459 | LSM_HOOK_INIT(inode_need_killpriv, cap_inode_need_killpriv), | |
1460 | LSM_HOOK_INIT(inode_killpriv, cap_inode_killpriv), | |
1461 | LSM_HOOK_INIT(inode_getsecurity, cap_inode_getsecurity), | |
1462 | LSM_HOOK_INIT(mmap_addr, cap_mmap_addr), | |
1463 | LSM_HOOK_INIT(mmap_file, cap_mmap_file), | |
1464 | LSM_HOOK_INIT(task_fix_setuid, cap_task_fix_setuid), | |
1465 | LSM_HOOK_INIT(task_prctl, cap_task_prctl), | |
1466 | LSM_HOOK_INIT(task_setscheduler, cap_task_setscheduler), | |
1467 | LSM_HOOK_INIT(task_setioprio, cap_task_setioprio), | |
1468 | LSM_HOOK_INIT(task_setnice, cap_task_setnice), | |
1469 | LSM_HOOK_INIT(vm_enough_memory, cap_vm_enough_memory), | |
1470 | }; | |
1471 | ||
1472 | static int __init capability_init(void) | |
1473 | { | |
1474 | security_add_hooks(capability_hooks, ARRAY_SIZE(capability_hooks), | |
1475 | &capability_lsmid); | |
1476 | return 0; | |
1477 | } | |
1478 | ||
1479 | DEFINE_LSM(capability) = { | |
1480 | .name = "capability", | |
1481 | .order = LSM_ORDER_FIRST, | |
1482 | .init = capability_init, | |
1483 | }; | |
1484 | ||
1485 | #endif /* CONFIG_SECURITY */ |