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 | #include <linux/mnt_idmapping.h> |
28 | #include <uapi/linux/lsm.h> |
29 | |
30 | /* |
31 | * If a non-root user executes a setuid-root binary in |
32 | * !secure(SECURE_NOROOT) mode, then we raise capabilities. |
33 | * However if fE is also set, then the intent is for only |
34 | * the file capabilities to be applied, and the setuid-root |
35 | * bit is left on either to change the uid (plausible) or |
36 | * to get full privilege on a kernel without file capabilities |
37 | * support. So in that case we do not raise capabilities. |
38 | * |
39 | * Warn if that happens, once per boot. |
40 | */ |
41 | static void warn_setuid_and_fcaps_mixed(const char *fname) |
42 | { |
43 | static int warned; |
44 | if (!warned) { |
45 | printk(KERN_INFO "warning: `%s' has both setuid-root and" |
46 | " effective capabilities. Therefore not raising all" |
47 | " capabilities.\n" , fname); |
48 | warned = 1; |
49 | } |
50 | } |
51 | |
52 | /** |
53 | * cap_capable - Determine whether a task has a particular effective capability |
54 | * @cred: The credentials to use |
55 | * @targ_ns: The user namespace in which we need the capability |
56 | * @cap: The capability to check for |
57 | * @opts: Bitmask of options defined in include/linux/security.h |
58 | * |
59 | * Determine whether the nominated task has the specified capability amongst |
60 | * its effective set, returning 0 if it does, -ve if it does not. |
61 | * |
62 | * NOTE WELL: cap_has_capability() cannot be used like the kernel's capable() |
63 | * and has_capability() functions. That is, it has the reverse semantics: |
64 | * cap_has_capability() returns 0 when a task has a capability, but the |
65 | * kernel's capable() and has_capability() returns 1 for this case. |
66 | */ |
67 | int cap_capable(const struct cred *cred, struct user_namespace *targ_ns, |
68 | int cap, unsigned int opts) |
69 | { |
70 | struct user_namespace *ns = targ_ns; |
71 | |
72 | /* See if cred has the capability in the target user namespace |
73 | * by examining the target user namespace and all of the target |
74 | * user namespace's parents. |
75 | */ |
76 | for (;;) { |
77 | /* Do we have the necessary capabilities? */ |
78 | if (ns == cred->user_ns) |
79 | return cap_raised(cred->cap_effective, cap) ? 0 : -EPERM; |
80 | |
81 | /* |
82 | * If we're already at a lower level than we're looking for, |
83 | * we're done searching. |
84 | */ |
85 | if (ns->level <= cred->user_ns->level) |
86 | return -EPERM; |
87 | |
88 | /* |
89 | * The owner of the user namespace in the parent of the |
90 | * user namespace has all caps. |
91 | */ |
92 | if ((ns->parent == cred->user_ns) && uid_eq(left: ns->owner, right: cred->euid)) |
93 | return 0; |
94 | |
95 | /* |
96 | * If you have a capability in a parent user ns, then you have |
97 | * it over all children user namespaces as well. |
98 | */ |
99 | ns = ns->parent; |
100 | } |
101 | |
102 | /* We never get here */ |
103 | } |
104 | |
105 | /** |
106 | * cap_settime - Determine whether the current process may set the system clock |
107 | * @ts: The time to set |
108 | * @tz: The timezone to set |
109 | * |
110 | * Determine whether the current process may set the system clock and timezone |
111 | * information, returning 0 if permission granted, -ve if denied. |
112 | */ |
113 | int cap_settime(const struct timespec64 *ts, const struct timezone *tz) |
114 | { |
115 | if (!capable(CAP_SYS_TIME)) |
116 | return -EPERM; |
117 | return 0; |
118 | } |
119 | |
120 | /** |
121 | * cap_ptrace_access_check - Determine whether the current process may access |
122 | * another |
123 | * @child: The process to be accessed |
124 | * @mode: The mode of attachment. |
125 | * |
126 | * If we are in the same or an ancestor user_ns and have all the target |
127 | * task's capabilities, then ptrace access is allowed. |
128 | * If we have the ptrace capability to the target user_ns, then ptrace |
129 | * access is allowed. |
130 | * Else denied. |
131 | * |
132 | * Determine whether a process may access another, returning 0 if permission |
133 | * granted, -ve if denied. |
134 | */ |
135 | int cap_ptrace_access_check(struct task_struct *child, unsigned int mode) |
136 | { |
137 | int ret = 0; |
138 | const struct cred *cred, *child_cred; |
139 | const kernel_cap_t *caller_caps; |
140 | |
141 | rcu_read_lock(); |
142 | cred = current_cred(); |
143 | child_cred = __task_cred(child); |
144 | if (mode & PTRACE_MODE_FSCREDS) |
145 | caller_caps = &cred->cap_effective; |
146 | else |
147 | caller_caps = &cred->cap_permitted; |
148 | if (cred->user_ns == child_cred->user_ns && |
149 | cap_issubset(a: child_cred->cap_permitted, set: *caller_caps)) |
150 | goto out; |
151 | if (ns_capable(ns: child_cred->user_ns, CAP_SYS_PTRACE)) |
152 | goto out; |
153 | ret = -EPERM; |
154 | out: |
155 | rcu_read_unlock(); |
156 | return ret; |
157 | } |
158 | |
159 | /** |
160 | * cap_ptrace_traceme - Determine whether another process may trace the current |
161 | * @parent: The task proposed to be the tracer |
162 | * |
163 | * If parent is in the same or an ancestor user_ns and has all current's |
164 | * capabilities, then ptrace access is allowed. |
165 | * If parent has the ptrace capability to current's user_ns, then ptrace |
166 | * access is allowed. |
167 | * Else denied. |
168 | * |
169 | * Determine whether the nominated task is permitted to trace the current |
170 | * process, returning 0 if permission is granted, -ve if denied. |
171 | */ |
172 | int cap_ptrace_traceme(struct task_struct *parent) |
173 | { |
174 | int ret = 0; |
175 | const struct cred *cred, *child_cred; |
176 | |
177 | rcu_read_lock(); |
178 | cred = __task_cred(parent); |
179 | child_cred = current_cred(); |
180 | if (cred->user_ns == child_cred->user_ns && |
181 | cap_issubset(a: child_cred->cap_permitted, set: cred->cap_permitted)) |
182 | goto out; |
183 | if (has_ns_capability(t: parent, ns: child_cred->user_ns, CAP_SYS_PTRACE)) |
184 | goto out; |
185 | ret = -EPERM; |
186 | out: |
187 | rcu_read_unlock(); |
188 | return ret; |
189 | } |
190 | |
191 | /** |
192 | * cap_capget - Retrieve a task's capability sets |
193 | * @target: The task from which to retrieve the capability sets |
194 | * @effective: The place to record the effective set |
195 | * @inheritable: The place to record the inheritable set |
196 | * @permitted: The place to record the permitted set |
197 | * |
198 | * This function retrieves the capabilities of the nominated task and returns |
199 | * them to the caller. |
200 | */ |
201 | int cap_capget(const struct task_struct *target, kernel_cap_t *effective, |
202 | kernel_cap_t *inheritable, kernel_cap_t *permitted) |
203 | { |
204 | const struct cred *cred; |
205 | |
206 | /* Derived from kernel/capability.c:sys_capget. */ |
207 | rcu_read_lock(); |
208 | cred = __task_cred(target); |
209 | *effective = cred->cap_effective; |
210 | *inheritable = cred->cap_inheritable; |
211 | *permitted = cred->cap_permitted; |
212 | rcu_read_unlock(); |
213 | return 0; |
214 | } |
215 | |
216 | /* |
217 | * Determine whether the inheritable capabilities are limited to the old |
218 | * permitted set. Returns 1 if they are limited, 0 if they are not. |
219 | */ |
220 | static inline int cap_inh_is_capped(void) |
221 | { |
222 | /* they are so limited unless the current task has the CAP_SETPCAP |
223 | * capability |
224 | */ |
225 | if (cap_capable(current_cred(), current_cred()->user_ns, |
226 | CAP_SETPCAP, CAP_OPT_NONE) == 0) |
227 | return 0; |
228 | return 1; |
229 | } |
230 | |
231 | /** |
232 | * cap_capset - Validate and apply proposed changes to current's capabilities |
233 | * @new: The proposed new credentials; alterations should be made here |
234 | * @old: The current task's current credentials |
235 | * @effective: A pointer to the proposed new effective capabilities set |
236 | * @inheritable: A pointer to the proposed new inheritable capabilities set |
237 | * @permitted: A pointer to the proposed new permitted capabilities set |
238 | * |
239 | * This function validates and applies a proposed mass change to the current |
240 | * process's capability sets. The changes are made to the proposed new |
241 | * credentials, and assuming no error, will be committed by the caller of LSM. |
242 | */ |
243 | int cap_capset(struct cred *new, |
244 | const struct cred *old, |
245 | const kernel_cap_t *effective, |
246 | const kernel_cap_t *inheritable, |
247 | const kernel_cap_t *permitted) |
248 | { |
249 | if (cap_inh_is_capped() && |
250 | !cap_issubset(a: *inheritable, |
251 | set: cap_combine(a: old->cap_inheritable, |
252 | b: old->cap_permitted))) |
253 | /* incapable of using this inheritable set */ |
254 | return -EPERM; |
255 | |
256 | if (!cap_issubset(a: *inheritable, |
257 | set: cap_combine(a: old->cap_inheritable, |
258 | b: old->cap_bset))) |
259 | /* no new pI capabilities outside bounding set */ |
260 | return -EPERM; |
261 | |
262 | /* verify restrictions on target's new Permitted set */ |
263 | if (!cap_issubset(a: *permitted, set: old->cap_permitted)) |
264 | return -EPERM; |
265 | |
266 | /* verify the _new_Effective_ is a subset of the _new_Permitted_ */ |
267 | if (!cap_issubset(a: *effective, set: *permitted)) |
268 | return -EPERM; |
269 | |
270 | new->cap_effective = *effective; |
271 | new->cap_inheritable = *inheritable; |
272 | new->cap_permitted = *permitted; |
273 | |
274 | /* |
275 | * Mask off ambient bits that are no longer both permitted and |
276 | * inheritable. |
277 | */ |
278 | new->cap_ambient = cap_intersect(a: new->cap_ambient, |
279 | b: cap_intersect(a: *permitted, |
280 | b: *inheritable)); |
281 | if (WARN_ON(!cap_ambient_invariant_ok(new))) |
282 | return -EINVAL; |
283 | return 0; |
284 | } |
285 | |
286 | /** |
287 | * cap_inode_need_killpriv - Determine if inode change affects privileges |
288 | * @dentry: The inode/dentry in being changed with change marked ATTR_KILL_PRIV |
289 | * |
290 | * Determine if an inode having a change applied that's marked ATTR_KILL_PRIV |
291 | * affects the security markings on that inode, and if it is, should |
292 | * inode_killpriv() be invoked or the change rejected. |
293 | * |
294 | * Return: 1 if security.capability has a value, meaning inode_killpriv() |
295 | * is required, 0 otherwise, meaning inode_killpriv() is not required. |
296 | */ |
297 | int cap_inode_need_killpriv(struct dentry *dentry) |
298 | { |
299 | struct inode *inode = d_backing_inode(upper: dentry); |
300 | int error; |
301 | |
302 | error = __vfs_getxattr(dentry, inode, XATTR_NAME_CAPS, NULL, 0); |
303 | return error > 0; |
304 | } |
305 | |
306 | /** |
307 | * cap_inode_killpriv - Erase the security markings on an inode |
308 | * |
309 | * @idmap: idmap of the mount the inode was found from |
310 | * @dentry: The inode/dentry to alter |
311 | * |
312 | * Erase the privilege-enhancing security markings on an inode. |
313 | * |
314 | * If the inode has been found through an idmapped mount the idmap of |
315 | * the vfsmount must be passed through @idmap. This function will then |
316 | * take care to map the inode according to @idmap before checking |
317 | * permissions. On non-idmapped mounts or if permission checking is to be |
318 | * performed on the raw inode simply pass @nop_mnt_idmap. |
319 | * |
320 | * Return: 0 if successful, -ve on error. |
321 | */ |
322 | int cap_inode_killpriv(struct mnt_idmap *idmap, struct dentry *dentry) |
323 | { |
324 | int error; |
325 | |
326 | error = __vfs_removexattr(idmap, dentry, XATTR_NAME_CAPS); |
327 | if (error == -EOPNOTSUPP) |
328 | error = 0; |
329 | return error; |
330 | } |
331 | |
332 | static bool rootid_owns_currentns(vfsuid_t rootvfsuid) |
333 | { |
334 | struct user_namespace *ns; |
335 | kuid_t kroot; |
336 | |
337 | if (!vfsuid_valid(uid: rootvfsuid)) |
338 | return false; |
339 | |
340 | kroot = vfsuid_into_kuid(vfsuid: rootvfsuid); |
341 | for (ns = current_user_ns();; ns = ns->parent) { |
342 | if (from_kuid(to: ns, uid: kroot) == 0) |
343 | return true; |
344 | if (ns == &init_user_ns) |
345 | break; |
346 | } |
347 | |
348 | return false; |
349 | } |
350 | |
351 | static __u32 sansflags(__u32 m) |
352 | { |
353 | return m & ~VFS_CAP_FLAGS_EFFECTIVE; |
354 | } |
355 | |
356 | static bool (int size, const struct vfs_cap_data *cap) |
357 | { |
358 | if (size != XATTR_CAPS_SZ_2) |
359 | return false; |
360 | return sansflags(le32_to_cpu(cap->magic_etc)) == VFS_CAP_REVISION_2; |
361 | } |
362 | |
363 | static bool (int size, const struct vfs_cap_data *cap) |
364 | { |
365 | if (size != XATTR_CAPS_SZ_3) |
366 | return false; |
367 | return sansflags(le32_to_cpu(cap->magic_etc)) == VFS_CAP_REVISION_3; |
368 | } |
369 | |
370 | /* |
371 | * getsecurity: We are called for security.* before any attempt to read the |
372 | * xattr from the inode itself. |
373 | * |
374 | * This gives us a chance to read the on-disk value and convert it. If we |
375 | * return -EOPNOTSUPP, then vfs_getxattr() will call the i_op handler. |
376 | * |
377 | * Note we are not called by vfs_getxattr_alloc(), but that is only called |
378 | * by the integrity subsystem, which really wants the unconverted values - |
379 | * so that's good. |
380 | */ |
381 | int cap_inode_getsecurity(struct mnt_idmap *idmap, |
382 | struct inode *inode, const char *name, void **buffer, |
383 | bool alloc) |
384 | { |
385 | int size; |
386 | kuid_t kroot; |
387 | vfsuid_t vfsroot; |
388 | u32 nsmagic, magic; |
389 | uid_t root, mappedroot; |
390 | char *tmpbuf = NULL; |
391 | struct vfs_cap_data *cap; |
392 | struct vfs_ns_cap_data *nscap = NULL; |
393 | struct dentry *dentry; |
394 | struct user_namespace *fs_ns; |
395 | |
396 | if (strcmp(name, "capability" ) != 0) |
397 | return -EOPNOTSUPP; |
398 | |
399 | dentry = d_find_any_alias(inode); |
400 | if (!dentry) |
401 | return -EINVAL; |
402 | size = vfs_getxattr_alloc(idmap, dentry, XATTR_NAME_CAPS, xattr_value: &tmpbuf, |
403 | size: sizeof(struct vfs_ns_cap_data), GFP_NOFS); |
404 | dput(dentry); |
405 | /* gcc11 complains if we don't check for !tmpbuf */ |
406 | if (size < 0 || !tmpbuf) |
407 | goto out_free; |
408 | |
409 | fs_ns = inode->i_sb->s_user_ns; |
410 | cap = (struct vfs_cap_data *) tmpbuf; |
411 | if (is_v2header(size, cap)) { |
412 | root = 0; |
413 | } else if (is_v3header(size, cap)) { |
414 | nscap = (struct vfs_ns_cap_data *) tmpbuf; |
415 | root = le32_to_cpu(nscap->rootid); |
416 | } else { |
417 | size = -EINVAL; |
418 | goto out_free; |
419 | } |
420 | |
421 | kroot = make_kuid(from: fs_ns, uid: root); |
422 | |
423 | /* If this is an idmapped mount shift the kuid. */ |
424 | vfsroot = make_vfsuid(idmap, fs_userns: fs_ns, kuid: kroot); |
425 | |
426 | /* If the root kuid maps to a valid uid in current ns, then return |
427 | * this as a nscap. */ |
428 | mappedroot = from_kuid(current_user_ns(), uid: vfsuid_into_kuid(vfsuid: vfsroot)); |
429 | if (mappedroot != (uid_t)-1 && mappedroot != (uid_t)0) { |
430 | size = sizeof(struct vfs_ns_cap_data); |
431 | if (alloc) { |
432 | if (!nscap) { |
433 | /* v2 -> v3 conversion */ |
434 | nscap = kzalloc(size, GFP_ATOMIC); |
435 | if (!nscap) { |
436 | size = -ENOMEM; |
437 | goto out_free; |
438 | } |
439 | nsmagic = VFS_CAP_REVISION_3; |
440 | magic = le32_to_cpu(cap->magic_etc); |
441 | if (magic & VFS_CAP_FLAGS_EFFECTIVE) |
442 | nsmagic |= VFS_CAP_FLAGS_EFFECTIVE; |
443 | memcpy(&nscap->data, &cap->data, sizeof(__le32) * 2 * VFS_CAP_U32); |
444 | nscap->magic_etc = cpu_to_le32(nsmagic); |
445 | } else { |
446 | /* use allocated v3 buffer */ |
447 | tmpbuf = NULL; |
448 | } |
449 | nscap->rootid = cpu_to_le32(mappedroot); |
450 | *buffer = nscap; |
451 | } |
452 | goto out_free; |
453 | } |
454 | |
455 | if (!rootid_owns_currentns(rootvfsuid: vfsroot)) { |
456 | size = -EOVERFLOW; |
457 | goto out_free; |
458 | } |
459 | |
460 | /* This comes from a parent namespace. Return as a v2 capability */ |
461 | size = sizeof(struct vfs_cap_data); |
462 | if (alloc) { |
463 | if (nscap) { |
464 | /* v3 -> v2 conversion */ |
465 | cap = kzalloc(size, GFP_ATOMIC); |
466 | if (!cap) { |
467 | size = -ENOMEM; |
468 | goto out_free; |
469 | } |
470 | magic = VFS_CAP_REVISION_2; |
471 | nsmagic = le32_to_cpu(nscap->magic_etc); |
472 | if (nsmagic & VFS_CAP_FLAGS_EFFECTIVE) |
473 | magic |= VFS_CAP_FLAGS_EFFECTIVE; |
474 | memcpy(&cap->data, &nscap->data, sizeof(__le32) * 2 * VFS_CAP_U32); |
475 | cap->magic_etc = cpu_to_le32(magic); |
476 | } else { |
477 | /* use unconverted v2 */ |
478 | tmpbuf = NULL; |
479 | } |
480 | *buffer = cap; |
481 | } |
482 | out_free: |
483 | kfree(objp: tmpbuf); |
484 | return size; |
485 | } |
486 | |
487 | /** |
488 | * rootid_from_xattr - translate root uid of vfs caps |
489 | * |
490 | * @value: vfs caps value which may be modified by this function |
491 | * @size: size of @ivalue |
492 | * @task_ns: user namespace of the caller |
493 | */ |
494 | static vfsuid_t rootid_from_xattr(const void *value, size_t size, |
495 | struct user_namespace *task_ns) |
496 | { |
497 | const struct vfs_ns_cap_data *nscap = value; |
498 | uid_t rootid = 0; |
499 | |
500 | if (size == XATTR_CAPS_SZ_3) |
501 | rootid = le32_to_cpu(nscap->rootid); |
502 | |
503 | return VFSUIDT_INIT(make_kuid(task_ns, rootid)); |
504 | } |
505 | |
506 | static bool (size_t size, const struct vfs_cap_data *cap) |
507 | { |
508 | return is_v2header(size, cap) || is_v3header(size, cap); |
509 | } |
510 | |
511 | /** |
512 | * cap_convert_nscap - check vfs caps |
513 | * |
514 | * @idmap: idmap of the mount the inode was found from |
515 | * @dentry: used to retrieve inode to check permissions on |
516 | * @ivalue: vfs caps value which may be modified by this function |
517 | * @size: size of @ivalue |
518 | * |
519 | * User requested a write of security.capability. If needed, update the |
520 | * xattr to change from v2 to v3, or to fixup the v3 rootid. |
521 | * |
522 | * If the inode has been found through an idmapped mount the idmap of |
523 | * the vfsmount must be passed through @idmap. This function will then |
524 | * take care to map the inode according to @idmap before checking |
525 | * permissions. On non-idmapped mounts or if permission checking is to be |
526 | * performed on the raw inode simply pass @nop_mnt_idmap. |
527 | * |
528 | * Return: On success, return the new size; on error, return < 0. |
529 | */ |
530 | int cap_convert_nscap(struct mnt_idmap *idmap, struct dentry *dentry, |
531 | const void **ivalue, size_t size) |
532 | { |
533 | struct vfs_ns_cap_data *nscap; |
534 | uid_t nsrootid; |
535 | const struct vfs_cap_data *cap = *ivalue; |
536 | __u32 magic, nsmagic; |
537 | struct inode *inode = d_backing_inode(upper: dentry); |
538 | struct user_namespace *task_ns = current_user_ns(), |
539 | *fs_ns = inode->i_sb->s_user_ns; |
540 | kuid_t rootid; |
541 | vfsuid_t vfsrootid; |
542 | size_t newsize; |
543 | |
544 | if (!*ivalue) |
545 | return -EINVAL; |
546 | if (!validheader(size, cap)) |
547 | return -EINVAL; |
548 | if (!capable_wrt_inode_uidgid(idmap, inode, CAP_SETFCAP)) |
549 | return -EPERM; |
550 | if (size == XATTR_CAPS_SZ_2 && (idmap == &nop_mnt_idmap)) |
551 | if (ns_capable(ns: inode->i_sb->s_user_ns, CAP_SETFCAP)) |
552 | /* user is privileged, just write the v2 */ |
553 | return size; |
554 | |
555 | vfsrootid = rootid_from_xattr(value: *ivalue, size, task_ns); |
556 | if (!vfsuid_valid(uid: vfsrootid)) |
557 | return -EINVAL; |
558 | |
559 | rootid = from_vfsuid(idmap, fs_userns: fs_ns, vfsuid: vfsrootid); |
560 | if (!uid_valid(uid: rootid)) |
561 | return -EINVAL; |
562 | |
563 | nsrootid = from_kuid(to: fs_ns, uid: rootid); |
564 | if (nsrootid == -1) |
565 | return -EINVAL; |
566 | |
567 | newsize = sizeof(struct vfs_ns_cap_data); |
568 | nscap = kmalloc(size: newsize, GFP_ATOMIC); |
569 | if (!nscap) |
570 | return -ENOMEM; |
571 | nscap->rootid = cpu_to_le32(nsrootid); |
572 | nsmagic = VFS_CAP_REVISION_3; |
573 | magic = le32_to_cpu(cap->magic_etc); |
574 | if (magic & VFS_CAP_FLAGS_EFFECTIVE) |
575 | nsmagic |= VFS_CAP_FLAGS_EFFECTIVE; |
576 | nscap->magic_etc = cpu_to_le32(nsmagic); |
577 | memcpy(&nscap->data, &cap->data, sizeof(__le32) * 2 * VFS_CAP_U32); |
578 | |
579 | *ivalue = nscap; |
580 | return newsize; |
581 | } |
582 | |
583 | /* |
584 | * Calculate the new process capability sets from the capability sets attached |
585 | * to a file. |
586 | */ |
587 | static inline int bprm_caps_from_vfs_caps(struct cpu_vfs_cap_data *caps, |
588 | struct linux_binprm *bprm, |
589 | bool *effective, |
590 | bool *has_fcap) |
591 | { |
592 | struct cred *new = bprm->cred; |
593 | int ret = 0; |
594 | |
595 | if (caps->magic_etc & VFS_CAP_FLAGS_EFFECTIVE) |
596 | *effective = true; |
597 | |
598 | if (caps->magic_etc & VFS_CAP_REVISION_MASK) |
599 | *has_fcap = true; |
600 | |
601 | /* |
602 | * pP' = (X & fP) | (pI & fI) |
603 | * The addition of pA' is handled later. |
604 | */ |
605 | new->cap_permitted.val = |
606 | (new->cap_bset.val & caps->permitted.val) | |
607 | (new->cap_inheritable.val & caps->inheritable.val); |
608 | |
609 | if (caps->permitted.val & ~new->cap_permitted.val) |
610 | /* insufficient to execute correctly */ |
611 | ret = -EPERM; |
612 | |
613 | /* |
614 | * For legacy apps, with no internal support for recognizing they |
615 | * do not have enough capabilities, we return an error if they are |
616 | * missing some "forced" (aka file-permitted) capabilities. |
617 | */ |
618 | return *effective ? ret : 0; |
619 | } |
620 | |
621 | /** |
622 | * get_vfs_caps_from_disk - retrieve vfs caps from disk |
623 | * |
624 | * @idmap: idmap of the mount the inode was found from |
625 | * @dentry: dentry from which @inode is retrieved |
626 | * @cpu_caps: vfs capabilities |
627 | * |
628 | * Extract the on-exec-apply capability sets for an executable file. |
629 | * |
630 | * If the inode has been found through an idmapped mount the idmap of |
631 | * the vfsmount must be passed through @idmap. This function will then |
632 | * take care to map the inode according to @idmap before checking |
633 | * permissions. On non-idmapped mounts or if permission checking is to be |
634 | * performed on the raw inode simply pass @nop_mnt_idmap. |
635 | */ |
636 | int get_vfs_caps_from_disk(struct mnt_idmap *idmap, |
637 | const struct dentry *dentry, |
638 | struct cpu_vfs_cap_data *cpu_caps) |
639 | { |
640 | struct inode *inode = d_backing_inode(upper: dentry); |
641 | __u32 magic_etc; |
642 | int size; |
643 | struct vfs_ns_cap_data data, *nscaps = &data; |
644 | struct vfs_cap_data *caps = (struct vfs_cap_data *) &data; |
645 | kuid_t rootkuid; |
646 | vfsuid_t rootvfsuid; |
647 | struct user_namespace *fs_ns; |
648 | |
649 | memset(cpu_caps, 0, sizeof(struct cpu_vfs_cap_data)); |
650 | |
651 | if (!inode) |
652 | return -ENODATA; |
653 | |
654 | fs_ns = inode->i_sb->s_user_ns; |
655 | size = __vfs_getxattr((struct dentry *)dentry, inode, |
656 | XATTR_NAME_CAPS, &data, XATTR_CAPS_SZ); |
657 | if (size == -ENODATA || size == -EOPNOTSUPP) |
658 | /* no data, that's ok */ |
659 | return -ENODATA; |
660 | |
661 | if (size < 0) |
662 | return size; |
663 | |
664 | if (size < sizeof(magic_etc)) |
665 | return -EINVAL; |
666 | |
667 | cpu_caps->magic_etc = magic_etc = le32_to_cpu(caps->magic_etc); |
668 | |
669 | rootkuid = make_kuid(from: fs_ns, uid: 0); |
670 | switch (magic_etc & VFS_CAP_REVISION_MASK) { |
671 | case VFS_CAP_REVISION_1: |
672 | if (size != XATTR_CAPS_SZ_1) |
673 | return -EINVAL; |
674 | break; |
675 | case VFS_CAP_REVISION_2: |
676 | if (size != XATTR_CAPS_SZ_2) |
677 | return -EINVAL; |
678 | break; |
679 | case VFS_CAP_REVISION_3: |
680 | if (size != XATTR_CAPS_SZ_3) |
681 | return -EINVAL; |
682 | rootkuid = make_kuid(from: fs_ns, le32_to_cpu(nscaps->rootid)); |
683 | break; |
684 | |
685 | default: |
686 | return -EINVAL; |
687 | } |
688 | |
689 | rootvfsuid = make_vfsuid(idmap, fs_userns: fs_ns, kuid: rootkuid); |
690 | if (!vfsuid_valid(uid: rootvfsuid)) |
691 | return -ENODATA; |
692 | |
693 | /* Limit the caps to the mounter of the filesystem |
694 | * or the more limited uid specified in the xattr. |
695 | */ |
696 | if (!rootid_owns_currentns(rootvfsuid)) |
697 | return -ENODATA; |
698 | |
699 | cpu_caps->permitted.val = le32_to_cpu(caps->data[0].permitted); |
700 | cpu_caps->inheritable.val = le32_to_cpu(caps->data[0].inheritable); |
701 | |
702 | /* |
703 | * Rev1 had just a single 32-bit word, later expanded |
704 | * to a second one for the high bits |
705 | */ |
706 | if ((magic_etc & VFS_CAP_REVISION_MASK) != VFS_CAP_REVISION_1) { |
707 | cpu_caps->permitted.val += (u64)le32_to_cpu(caps->data[1].permitted) << 32; |
708 | cpu_caps->inheritable.val += (u64)le32_to_cpu(caps->data[1].inheritable) << 32; |
709 | } |
710 | |
711 | cpu_caps->permitted.val &= CAP_VALID_MASK; |
712 | cpu_caps->inheritable.val &= CAP_VALID_MASK; |
713 | |
714 | cpu_caps->rootid = vfsuid_into_kuid(vfsuid: rootvfsuid); |
715 | |
716 | return 0; |
717 | } |
718 | |
719 | /* |
720 | * Attempt to get the on-exec apply capability sets for an executable file from |
721 | * its xattrs and, if present, apply them to the proposed credentials being |
722 | * constructed by execve(). |
723 | */ |
724 | static int get_file_caps(struct linux_binprm *bprm, const struct file *file, |
725 | bool *effective, bool *has_fcap) |
726 | { |
727 | int rc = 0; |
728 | struct cpu_vfs_cap_data vcaps; |
729 | |
730 | cap_clear(bprm->cred->cap_permitted); |
731 | |
732 | if (!file_caps_enabled) |
733 | return 0; |
734 | |
735 | if (!mnt_may_suid(mnt: file->f_path.mnt)) |
736 | return 0; |
737 | |
738 | /* |
739 | * This check is redundant with mnt_may_suid() but is kept to make |
740 | * explicit that capability bits are limited to s_user_ns and its |
741 | * descendants. |
742 | */ |
743 | if (!current_in_userns(target_ns: file->f_path.mnt->mnt_sb->s_user_ns)) |
744 | return 0; |
745 | |
746 | rc = get_vfs_caps_from_disk(idmap: file_mnt_idmap(file), |
747 | dentry: file->f_path.dentry, cpu_caps: &vcaps); |
748 | if (rc < 0) { |
749 | if (rc == -EINVAL) |
750 | printk(KERN_NOTICE "Invalid argument reading file caps for %s\n" , |
751 | bprm->filename); |
752 | else if (rc == -ENODATA) |
753 | rc = 0; |
754 | goto out; |
755 | } |
756 | |
757 | rc = bprm_caps_from_vfs_caps(caps: &vcaps, bprm, effective, has_fcap); |
758 | |
759 | out: |
760 | if (rc) |
761 | cap_clear(bprm->cred->cap_permitted); |
762 | |
763 | return rc; |
764 | } |
765 | |
766 | static inline bool root_privileged(void) { return !issecure(SECURE_NOROOT); } |
767 | |
768 | static inline bool __is_real(kuid_t uid, struct cred *cred) |
769 | { return uid_eq(left: cred->uid, right: uid); } |
770 | |
771 | static inline bool __is_eff(kuid_t uid, struct cred *cred) |
772 | { return uid_eq(left: cred->euid, right: uid); } |
773 | |
774 | static inline bool __is_suid(kuid_t uid, struct cred *cred) |
775 | { return !__is_real(uid, cred) && __is_eff(uid, cred); } |
776 | |
777 | /* |
778 | * handle_privileged_root - Handle case of privileged root |
779 | * @bprm: The execution parameters, including the proposed creds |
780 | * @has_fcap: Are any file capabilities set? |
781 | * @effective: Do we have effective root privilege? |
782 | * @root_uid: This namespace' root UID WRT initial USER namespace |
783 | * |
784 | * Handle the case where root is privileged and hasn't been neutered by |
785 | * SECURE_NOROOT. If file capabilities are set, they won't be combined with |
786 | * set UID root and nothing is changed. If we are root, cap_permitted is |
787 | * updated. If we have become set UID root, the effective bit is set. |
788 | */ |
789 | static void handle_privileged_root(struct linux_binprm *bprm, bool has_fcap, |
790 | bool *effective, kuid_t root_uid) |
791 | { |
792 | const struct cred *old = current_cred(); |
793 | struct cred *new = bprm->cred; |
794 | |
795 | if (!root_privileged()) |
796 | return; |
797 | /* |
798 | * If the legacy file capability is set, then don't set privs |
799 | * for a setuid root binary run by a non-root user. Do set it |
800 | * for a root user just to cause least surprise to an admin. |
801 | */ |
802 | if (has_fcap && __is_suid(uid: root_uid, cred: new)) { |
803 | warn_setuid_and_fcaps_mixed(fname: bprm->filename); |
804 | return; |
805 | } |
806 | /* |
807 | * To support inheritance of root-permissions and suid-root |
808 | * executables under compatibility mode, we override the |
809 | * capability sets for the file. |
810 | */ |
811 | if (__is_eff(uid: root_uid, cred: new) || __is_real(uid: root_uid, cred: new)) { |
812 | /* pP' = (cap_bset & ~0) | (pI & ~0) */ |
813 | new->cap_permitted = cap_combine(a: old->cap_bset, |
814 | b: old->cap_inheritable); |
815 | } |
816 | /* |
817 | * If only the real uid is 0, we do not set the effective bit. |
818 | */ |
819 | if (__is_eff(uid: root_uid, cred: new)) |
820 | *effective = true; |
821 | } |
822 | |
823 | #define __cap_gained(field, target, source) \ |
824 | !cap_issubset(target->cap_##field, source->cap_##field) |
825 | #define __cap_grew(target, source, cred) \ |
826 | !cap_issubset(cred->cap_##target, cred->cap_##source) |
827 | #define __cap_full(field, cred) \ |
828 | cap_issubset(CAP_FULL_SET, cred->cap_##field) |
829 | |
830 | static inline bool __is_setuid(struct cred *new, const struct cred *old) |
831 | { return !uid_eq(left: new->euid, right: old->uid); } |
832 | |
833 | static inline bool __is_setgid(struct cred *new, const struct cred *old) |
834 | { return !gid_eq(left: new->egid, right: old->gid); } |
835 | |
836 | /* |
837 | * 1) Audit candidate if current->cap_effective is set |
838 | * |
839 | * We do not bother to audit if 3 things are true: |
840 | * 1) cap_effective has all caps |
841 | * 2) we became root *OR* are were already root |
842 | * 3) root is supposed to have all caps (SECURE_NOROOT) |
843 | * Since this is just a normal root execing a process. |
844 | * |
845 | * Number 1 above might fail if you don't have a full bset, but I think |
846 | * that is interesting information to audit. |
847 | * |
848 | * A number of other conditions require logging: |
849 | * 2) something prevented setuid root getting all caps |
850 | * 3) non-setuid root gets fcaps |
851 | * 4) non-setuid root gets ambient |
852 | */ |
853 | static inline bool nonroot_raised_pE(struct cred *new, const struct cred *old, |
854 | kuid_t root, bool has_fcap) |
855 | { |
856 | bool ret = false; |
857 | |
858 | if ((__cap_grew(effective, ambient, new) && |
859 | !(__cap_full(effective, new) && |
860 | (__is_eff(uid: root, cred: new) || __is_real(uid: root, cred: new)) && |
861 | root_privileged())) || |
862 | (root_privileged() && |
863 | __is_suid(uid: root, cred: new) && |
864 | !__cap_full(effective, new)) || |
865 | (!__is_setuid(new, old) && |
866 | ((has_fcap && |
867 | __cap_gained(permitted, new, old)) || |
868 | __cap_gained(ambient, new, old)))) |
869 | |
870 | ret = true; |
871 | |
872 | return ret; |
873 | } |
874 | |
875 | /** |
876 | * cap_bprm_creds_from_file - Set up the proposed credentials for execve(). |
877 | * @bprm: The execution parameters, including the proposed creds |
878 | * @file: The file to pull the credentials from |
879 | * |
880 | * Set up the proposed credentials for a new execution context being |
881 | * constructed by execve(). The proposed creds in @bprm->cred is altered, |
882 | * which won't take effect immediately. |
883 | * |
884 | * Return: 0 if successful, -ve on error. |
885 | */ |
886 | int cap_bprm_creds_from_file(struct linux_binprm *bprm, const struct file *file) |
887 | { |
888 | /* Process setpcap binaries and capabilities for uid 0 */ |
889 | const struct cred *old = current_cred(); |
890 | struct cred *new = bprm->cred; |
891 | bool effective = false, has_fcap = false, is_setid; |
892 | int ret; |
893 | kuid_t root_uid; |
894 | |
895 | if (WARN_ON(!cap_ambient_invariant_ok(old))) |
896 | return -EPERM; |
897 | |
898 | ret = get_file_caps(bprm, file, effective: &effective, has_fcap: &has_fcap); |
899 | if (ret < 0) |
900 | return ret; |
901 | |
902 | root_uid = make_kuid(from: new->user_ns, uid: 0); |
903 | |
904 | handle_privileged_root(bprm, has_fcap, effective: &effective, root_uid); |
905 | |
906 | /* if we have fs caps, clear dangerous personality flags */ |
907 | if (__cap_gained(permitted, new, old)) |
908 | bprm->per_clear |= PER_CLEAR_ON_SETID; |
909 | |
910 | /* Don't let someone trace a set[ug]id/setpcap binary with the revised |
911 | * credentials unless they have the appropriate permit. |
912 | * |
913 | * In addition, if NO_NEW_PRIVS, then ensure we get no new privs. |
914 | */ |
915 | is_setid = __is_setuid(new, old) || __is_setgid(new, old); |
916 | |
917 | if ((is_setid || __cap_gained(permitted, new, old)) && |
918 | ((bprm->unsafe & ~LSM_UNSAFE_PTRACE) || |
919 | !ptracer_capable(current, ns: new->user_ns))) { |
920 | /* downgrade; they get no more than they had, and maybe less */ |
921 | if (!ns_capable(ns: new->user_ns, CAP_SETUID) || |
922 | (bprm->unsafe & LSM_UNSAFE_NO_NEW_PRIVS)) { |
923 | new->euid = new->uid; |
924 | new->egid = new->gid; |
925 | } |
926 | new->cap_permitted = cap_intersect(a: new->cap_permitted, |
927 | b: old->cap_permitted); |
928 | } |
929 | |
930 | new->suid = new->fsuid = new->euid; |
931 | new->sgid = new->fsgid = new->egid; |
932 | |
933 | /* File caps or setid cancels ambient. */ |
934 | if (has_fcap || is_setid) |
935 | cap_clear(new->cap_ambient); |
936 | |
937 | /* |
938 | * Now that we've computed pA', update pP' to give: |
939 | * pP' = (X & fP) | (pI & fI) | pA' |
940 | */ |
941 | new->cap_permitted = cap_combine(a: new->cap_permitted, b: new->cap_ambient); |
942 | |
943 | /* |
944 | * Set pE' = (fE ? pP' : pA'). Because pA' is zero if fE is set, |
945 | * this is the same as pE' = (fE ? pP' : 0) | pA'. |
946 | */ |
947 | if (effective) |
948 | new->cap_effective = new->cap_permitted; |
949 | else |
950 | new->cap_effective = new->cap_ambient; |
951 | |
952 | if (WARN_ON(!cap_ambient_invariant_ok(new))) |
953 | return -EPERM; |
954 | |
955 | if (nonroot_raised_pE(new, old, root: root_uid, has_fcap)) { |
956 | ret = audit_log_bprm_fcaps(bprm, new, old); |
957 | if (ret < 0) |
958 | return ret; |
959 | } |
960 | |
961 | new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS); |
962 | |
963 | if (WARN_ON(!cap_ambient_invariant_ok(new))) |
964 | return -EPERM; |
965 | |
966 | /* Check for privilege-elevated exec. */ |
967 | if (is_setid || |
968 | (!__is_real(uid: root_uid, cred: new) && |
969 | (effective || |
970 | __cap_grew(permitted, ambient, new)))) |
971 | bprm->secureexec = 1; |
972 | |
973 | return 0; |
974 | } |
975 | |
976 | /** |
977 | * cap_inode_setxattr - Determine whether an xattr may be altered |
978 | * @dentry: The inode/dentry being altered |
979 | * @name: The name of the xattr to be changed |
980 | * @value: The value that the xattr will be changed to |
981 | * @size: The size of value |
982 | * @flags: The replacement flag |
983 | * |
984 | * Determine whether an xattr may be altered or set on an inode, returning 0 if |
985 | * permission is granted, -ve if denied. |
986 | * |
987 | * This is used to make sure security xattrs don't get updated or set by those |
988 | * who aren't privileged to do so. |
989 | */ |
990 | int cap_inode_setxattr(struct dentry *dentry, const char *name, |
991 | const void *value, size_t size, int flags) |
992 | { |
993 | struct user_namespace *user_ns = dentry->d_sb->s_user_ns; |
994 | |
995 | /* Ignore non-security xattrs */ |
996 | if (strncmp(name, XATTR_SECURITY_PREFIX, |
997 | XATTR_SECURITY_PREFIX_LEN) != 0) |
998 | return 0; |
999 | |
1000 | /* |
1001 | * For XATTR_NAME_CAPS the check will be done in |
1002 | * cap_convert_nscap(), called by setxattr() |
1003 | */ |
1004 | if (strcmp(name, XATTR_NAME_CAPS) == 0) |
1005 | return 0; |
1006 | |
1007 | if (!ns_capable(ns: user_ns, CAP_SYS_ADMIN)) |
1008 | return -EPERM; |
1009 | return 0; |
1010 | } |
1011 | |
1012 | /** |
1013 | * cap_inode_removexattr - Determine whether an xattr may be removed |
1014 | * |
1015 | * @idmap: idmap of the mount the inode was found from |
1016 | * @dentry: The inode/dentry being altered |
1017 | * @name: The name of the xattr to be changed |
1018 | * |
1019 | * Determine whether an xattr may be removed from an inode, returning 0 if |
1020 | * permission is granted, -ve if denied. |
1021 | * |
1022 | * If the inode has been found through an idmapped mount the idmap of |
1023 | * the vfsmount must be passed through @idmap. This function will then |
1024 | * take care to map the inode according to @idmap before checking |
1025 | * permissions. On non-idmapped mounts or if permission checking is to be |
1026 | * performed on the raw inode simply pass @nop_mnt_idmap. |
1027 | * |
1028 | * This is used to make sure security xattrs don't get removed by those who |
1029 | * aren't privileged to remove them. |
1030 | */ |
1031 | int cap_inode_removexattr(struct mnt_idmap *idmap, |
1032 | struct dentry *dentry, const char *name) |
1033 | { |
1034 | struct user_namespace *user_ns = dentry->d_sb->s_user_ns; |
1035 | |
1036 | /* Ignore non-security xattrs */ |
1037 | if (strncmp(name, XATTR_SECURITY_PREFIX, |
1038 | XATTR_SECURITY_PREFIX_LEN) != 0) |
1039 | return 0; |
1040 | |
1041 | if (strcmp(name, XATTR_NAME_CAPS) == 0) { |
1042 | /* security.capability gets namespaced */ |
1043 | struct inode *inode = d_backing_inode(upper: dentry); |
1044 | if (!inode) |
1045 | return -EINVAL; |
1046 | if (!capable_wrt_inode_uidgid(idmap, inode, CAP_SETFCAP)) |
1047 | return -EPERM; |
1048 | return 0; |
1049 | } |
1050 | |
1051 | if (!ns_capable(ns: user_ns, CAP_SYS_ADMIN)) |
1052 | return -EPERM; |
1053 | return 0; |
1054 | } |
1055 | |
1056 | /* |
1057 | * cap_emulate_setxuid() fixes the effective / permitted capabilities of |
1058 | * a process after a call to setuid, setreuid, or setresuid. |
1059 | * |
1060 | * 1) When set*uiding _from_ one of {r,e,s}uid == 0 _to_ all of |
1061 | * {r,e,s}uid != 0, the permitted and effective capabilities are |
1062 | * cleared. |
1063 | * |
1064 | * 2) When set*uiding _from_ euid == 0 _to_ euid != 0, the effective |
1065 | * capabilities of the process are cleared. |
1066 | * |
1067 | * 3) When set*uiding _from_ euid != 0 _to_ euid == 0, the effective |
1068 | * capabilities are set to the permitted capabilities. |
1069 | * |
1070 | * fsuid is handled elsewhere. fsuid == 0 and {r,e,s}uid!= 0 should |
1071 | * never happen. |
1072 | * |
1073 | * -astor |
1074 | * |
1075 | * cevans - New behaviour, Oct '99 |
1076 | * A process may, via prctl(), elect to keep its capabilities when it |
1077 | * calls setuid() and switches away from uid==0. Both permitted and |
1078 | * effective sets will be retained. |
1079 | * Without this change, it was impossible for a daemon to drop only some |
1080 | * of its privilege. The call to setuid(!=0) would drop all privileges! |
1081 | * Keeping uid 0 is not an option because uid 0 owns too many vital |
1082 | * files.. |
1083 | * Thanks to Olaf Kirch and Peter Benie for spotting this. |
1084 | */ |
1085 | static inline void cap_emulate_setxuid(struct cred *new, const struct cred *old) |
1086 | { |
1087 | kuid_t root_uid = make_kuid(from: old->user_ns, uid: 0); |
1088 | |
1089 | if ((uid_eq(left: old->uid, right: root_uid) || |
1090 | uid_eq(left: old->euid, right: root_uid) || |
1091 | uid_eq(left: old->suid, right: root_uid)) && |
1092 | (!uid_eq(left: new->uid, right: root_uid) && |
1093 | !uid_eq(left: new->euid, right: root_uid) && |
1094 | !uid_eq(left: new->suid, right: root_uid))) { |
1095 | if (!issecure(SECURE_KEEP_CAPS)) { |
1096 | cap_clear(new->cap_permitted); |
1097 | cap_clear(new->cap_effective); |
1098 | } |
1099 | |
1100 | /* |
1101 | * Pre-ambient programs expect setresuid to nonroot followed |
1102 | * by exec to drop capabilities. We should make sure that |
1103 | * this remains the case. |
1104 | */ |
1105 | cap_clear(new->cap_ambient); |
1106 | } |
1107 | if (uid_eq(left: old->euid, right: root_uid) && !uid_eq(left: new->euid, right: root_uid)) |
1108 | cap_clear(new->cap_effective); |
1109 | if (!uid_eq(left: old->euid, right: root_uid) && uid_eq(left: new->euid, right: root_uid)) |
1110 | new->cap_effective = new->cap_permitted; |
1111 | } |
1112 | |
1113 | /** |
1114 | * cap_task_fix_setuid - Fix up the results of setuid() call |
1115 | * @new: The proposed credentials |
1116 | * @old: The current task's current credentials |
1117 | * @flags: Indications of what has changed |
1118 | * |
1119 | * Fix up the results of setuid() call before the credential changes are |
1120 | * actually applied. |
1121 | * |
1122 | * Return: 0 to grant the changes, -ve to deny them. |
1123 | */ |
1124 | int cap_task_fix_setuid(struct cred *new, const struct cred *old, int flags) |
1125 | { |
1126 | switch (flags) { |
1127 | case LSM_SETID_RE: |
1128 | case LSM_SETID_ID: |
1129 | case LSM_SETID_RES: |
1130 | /* juggle the capabilities to follow [RES]UID changes unless |
1131 | * otherwise suppressed */ |
1132 | if (!issecure(SECURE_NO_SETUID_FIXUP)) |
1133 | cap_emulate_setxuid(new, old); |
1134 | break; |
1135 | |
1136 | case LSM_SETID_FS: |
1137 | /* juggle the capabilities to follow FSUID changes, unless |
1138 | * otherwise suppressed |
1139 | * |
1140 | * FIXME - is fsuser used for all CAP_FS_MASK capabilities? |
1141 | * if not, we might be a bit too harsh here. |
1142 | */ |
1143 | if (!issecure(SECURE_NO_SETUID_FIXUP)) { |
1144 | kuid_t root_uid = make_kuid(from: old->user_ns, uid: 0); |
1145 | if (uid_eq(left: old->fsuid, right: root_uid) && !uid_eq(left: new->fsuid, right: root_uid)) |
1146 | new->cap_effective = |
1147 | cap_drop_fs_set(a: new->cap_effective); |
1148 | |
1149 | if (!uid_eq(left: old->fsuid, right: root_uid) && uid_eq(left: new->fsuid, right: root_uid)) |
1150 | new->cap_effective = |
1151 | cap_raise_fs_set(a: new->cap_effective, |
1152 | permitted: new->cap_permitted); |
1153 | } |
1154 | break; |
1155 | |
1156 | default: |
1157 | return -EINVAL; |
1158 | } |
1159 | |
1160 | return 0; |
1161 | } |
1162 | |
1163 | /* |
1164 | * Rationale: code calling task_setscheduler, task_setioprio, and |
1165 | * task_setnice, assumes that |
1166 | * . if capable(cap_sys_nice), then those actions should be allowed |
1167 | * . if not capable(cap_sys_nice), but acting on your own processes, |
1168 | * then those actions should be allowed |
1169 | * This is insufficient now since you can call code without suid, but |
1170 | * yet with increased caps. |
1171 | * So we check for increased caps on the target process. |
1172 | */ |
1173 | static int cap_safe_nice(struct task_struct *p) |
1174 | { |
1175 | int is_subset, ret = 0; |
1176 | |
1177 | rcu_read_lock(); |
1178 | is_subset = cap_issubset(__task_cred(p)->cap_permitted, |
1179 | current_cred()->cap_permitted); |
1180 | if (!is_subset && !ns_capable(__task_cred(p)->user_ns, CAP_SYS_NICE)) |
1181 | ret = -EPERM; |
1182 | rcu_read_unlock(); |
1183 | |
1184 | return ret; |
1185 | } |
1186 | |
1187 | /** |
1188 | * cap_task_setscheduler - Determine if scheduler policy change is permitted |
1189 | * @p: The task to affect |
1190 | * |
1191 | * Determine if the requested scheduler policy change is permitted for the |
1192 | * specified task. |
1193 | * |
1194 | * Return: 0 if permission is granted, -ve if denied. |
1195 | */ |
1196 | int cap_task_setscheduler(struct task_struct *p) |
1197 | { |
1198 | return cap_safe_nice(p); |
1199 | } |
1200 | |
1201 | /** |
1202 | * cap_task_setioprio - Determine if I/O priority change is permitted |
1203 | * @p: The task to affect |
1204 | * @ioprio: The I/O priority to set |
1205 | * |
1206 | * Determine if the requested I/O priority change is permitted for the specified |
1207 | * task. |
1208 | * |
1209 | * Return: 0 if permission is granted, -ve if denied. |
1210 | */ |
1211 | int cap_task_setioprio(struct task_struct *p, int ioprio) |
1212 | { |
1213 | return cap_safe_nice(p); |
1214 | } |
1215 | |
1216 | /** |
1217 | * cap_task_setnice - Determine if task priority change is permitted |
1218 | * @p: The task to affect |
1219 | * @nice: The nice value to set |
1220 | * |
1221 | * Determine if the requested task priority change is permitted for the |
1222 | * specified task. |
1223 | * |
1224 | * Return: 0 if permission is granted, -ve if denied. |
1225 | */ |
1226 | int cap_task_setnice(struct task_struct *p, int nice) |
1227 | { |
1228 | return cap_safe_nice(p); |
1229 | } |
1230 | |
1231 | /* |
1232 | * Implement PR_CAPBSET_DROP. Attempt to remove the specified capability from |
1233 | * the current task's bounding set. Returns 0 on success, -ve on error. |
1234 | */ |
1235 | static int cap_prctl_drop(unsigned long cap) |
1236 | { |
1237 | struct cred *new; |
1238 | |
1239 | if (!ns_capable(current_user_ns(), CAP_SETPCAP)) |
1240 | return -EPERM; |
1241 | if (!cap_valid(cap)) |
1242 | return -EINVAL; |
1243 | |
1244 | new = prepare_creds(); |
1245 | if (!new) |
1246 | return -ENOMEM; |
1247 | cap_lower(new->cap_bset, cap); |
1248 | return commit_creds(new); |
1249 | } |
1250 | |
1251 | /** |
1252 | * cap_task_prctl - Implement process control functions for this security module |
1253 | * @option: The process control function requested |
1254 | * @arg2: The argument data for this function |
1255 | * @arg3: The argument data for this function |
1256 | * @arg4: The argument data for this function |
1257 | * @arg5: The argument data for this function |
1258 | * |
1259 | * Allow process control functions (sys_prctl()) to alter capabilities; may |
1260 | * also deny access to other functions not otherwise implemented here. |
1261 | * |
1262 | * Return: 0 or +ve on success, -ENOSYS if this function is not implemented |
1263 | * here, other -ve on error. If -ENOSYS is returned, sys_prctl() and other LSM |
1264 | * modules will consider performing the function. |
1265 | */ |
1266 | int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3, |
1267 | unsigned long arg4, unsigned long arg5) |
1268 | { |
1269 | const struct cred *old = current_cred(); |
1270 | struct cred *new; |
1271 | |
1272 | switch (option) { |
1273 | case PR_CAPBSET_READ: |
1274 | if (!cap_valid(arg2)) |
1275 | return -EINVAL; |
1276 | return !!cap_raised(old->cap_bset, arg2); |
1277 | |
1278 | case PR_CAPBSET_DROP: |
1279 | return cap_prctl_drop(cap: arg2); |
1280 | |
1281 | /* |
1282 | * The next four prctl's remain to assist with transitioning a |
1283 | * system from legacy UID=0 based privilege (when filesystem |
1284 | * capabilities are not in use) to a system using filesystem |
1285 | * capabilities only - as the POSIX.1e draft intended. |
1286 | * |
1287 | * Note: |
1288 | * |
1289 | * PR_SET_SECUREBITS = |
1290 | * issecure_mask(SECURE_KEEP_CAPS_LOCKED) |
1291 | * | issecure_mask(SECURE_NOROOT) |
1292 | * | issecure_mask(SECURE_NOROOT_LOCKED) |
1293 | * | issecure_mask(SECURE_NO_SETUID_FIXUP) |
1294 | * | issecure_mask(SECURE_NO_SETUID_FIXUP_LOCKED) |
1295 | * |
1296 | * will ensure that the current process and all of its |
1297 | * children will be locked into a pure |
1298 | * capability-based-privilege environment. |
1299 | */ |
1300 | case PR_SET_SECUREBITS: |
1301 | if ((((old->securebits & SECURE_ALL_LOCKS) >> 1) |
1302 | & (old->securebits ^ arg2)) /*[1]*/ |
1303 | || ((old->securebits & SECURE_ALL_LOCKS & ~arg2)) /*[2]*/ |
1304 | || (arg2 & ~(SECURE_ALL_LOCKS | SECURE_ALL_BITS)) /*[3]*/ |
1305 | || (cap_capable(current_cred(), |
1306 | current_cred()->user_ns, |
1307 | CAP_SETPCAP, |
1308 | CAP_OPT_NONE) != 0) /*[4]*/ |
1309 | /* |
1310 | * [1] no changing of bits that are locked |
1311 | * [2] no unlocking of locks |
1312 | * [3] no setting of unsupported bits |
1313 | * [4] doing anything requires privilege (go read about |
1314 | * the "sendmail capabilities bug") |
1315 | */ |
1316 | ) |
1317 | /* cannot change a locked bit */ |
1318 | return -EPERM; |
1319 | |
1320 | new = prepare_creds(); |
1321 | if (!new) |
1322 | return -ENOMEM; |
1323 | new->securebits = arg2; |
1324 | return commit_creds(new); |
1325 | |
1326 | case PR_GET_SECUREBITS: |
1327 | return old->securebits; |
1328 | |
1329 | case PR_GET_KEEPCAPS: |
1330 | return !!issecure(SECURE_KEEP_CAPS); |
1331 | |
1332 | case PR_SET_KEEPCAPS: |
1333 | if (arg2 > 1) /* Note, we rely on arg2 being unsigned here */ |
1334 | return -EINVAL; |
1335 | if (issecure(SECURE_KEEP_CAPS_LOCKED)) |
1336 | return -EPERM; |
1337 | |
1338 | new = prepare_creds(); |
1339 | if (!new) |
1340 | return -ENOMEM; |
1341 | if (arg2) |
1342 | new->securebits |= issecure_mask(SECURE_KEEP_CAPS); |
1343 | else |
1344 | new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS); |
1345 | return commit_creds(new); |
1346 | |
1347 | case PR_CAP_AMBIENT: |
1348 | if (arg2 == PR_CAP_AMBIENT_CLEAR_ALL) { |
1349 | if (arg3 | arg4 | arg5) |
1350 | return -EINVAL; |
1351 | |
1352 | new = prepare_creds(); |
1353 | if (!new) |
1354 | return -ENOMEM; |
1355 | cap_clear(new->cap_ambient); |
1356 | return commit_creds(new); |
1357 | } |
1358 | |
1359 | if (((!cap_valid(arg3)) | arg4 | arg5)) |
1360 | return -EINVAL; |
1361 | |
1362 | if (arg2 == PR_CAP_AMBIENT_IS_SET) { |
1363 | return !!cap_raised(current_cred()->cap_ambient, arg3); |
1364 | } else if (arg2 != PR_CAP_AMBIENT_RAISE && |
1365 | arg2 != PR_CAP_AMBIENT_LOWER) { |
1366 | return -EINVAL; |
1367 | } else { |
1368 | if (arg2 == PR_CAP_AMBIENT_RAISE && |
1369 | (!cap_raised(current_cred()->cap_permitted, arg3) || |
1370 | !cap_raised(current_cred()->cap_inheritable, |
1371 | arg3) || |
1372 | issecure(SECURE_NO_CAP_AMBIENT_RAISE))) |
1373 | return -EPERM; |
1374 | |
1375 | new = prepare_creds(); |
1376 | if (!new) |
1377 | return -ENOMEM; |
1378 | if (arg2 == PR_CAP_AMBIENT_RAISE) |
1379 | cap_raise(new->cap_ambient, arg3); |
1380 | else |
1381 | cap_lower(new->cap_ambient, arg3); |
1382 | return commit_creds(new); |
1383 | } |
1384 | |
1385 | default: |
1386 | /* No functionality available - continue with default */ |
1387 | return -ENOSYS; |
1388 | } |
1389 | } |
1390 | |
1391 | /** |
1392 | * cap_vm_enough_memory - Determine whether a new virtual mapping is permitted |
1393 | * @mm: The VM space in which the new mapping is to be made |
1394 | * @pages: The size of the mapping |
1395 | * |
1396 | * Determine whether the allocation of a new virtual mapping by the current |
1397 | * task is permitted. |
1398 | * |
1399 | * Return: 1 if permission is granted, 0 if not. |
1400 | */ |
1401 | int cap_vm_enough_memory(struct mm_struct *mm, long pages) |
1402 | { |
1403 | int cap_sys_admin = 0; |
1404 | |
1405 | if (cap_capable(current_cred(), targ_ns: &init_user_ns, |
1406 | CAP_SYS_ADMIN, CAP_OPT_NOAUDIT) == 0) |
1407 | cap_sys_admin = 1; |
1408 | |
1409 | return cap_sys_admin; |
1410 | } |
1411 | |
1412 | /** |
1413 | * cap_mmap_addr - check if able to map given addr |
1414 | * @addr: address attempting to be mapped |
1415 | * |
1416 | * If the process is attempting to map memory below dac_mmap_min_addr they need |
1417 | * CAP_SYS_RAWIO. The other parameters to this function are unused by the |
1418 | * capability security module. |
1419 | * |
1420 | * Return: 0 if this mapping should be allowed or -EPERM if not. |
1421 | */ |
1422 | int cap_mmap_addr(unsigned long addr) |
1423 | { |
1424 | int ret = 0; |
1425 | |
1426 | if (addr < dac_mmap_min_addr) { |
1427 | ret = cap_capable(current_cred(), targ_ns: &init_user_ns, CAP_SYS_RAWIO, |
1428 | CAP_OPT_NONE); |
1429 | /* set PF_SUPERPRIV if it turns out we allow the low mmap */ |
1430 | if (ret == 0) |
1431 | current->flags |= PF_SUPERPRIV; |
1432 | } |
1433 | return ret; |
1434 | } |
1435 | |
1436 | int cap_mmap_file(struct file *file, unsigned long reqprot, |
1437 | unsigned long prot, unsigned long flags) |
1438 | { |
1439 | return 0; |
1440 | } |
1441 | |
1442 | #ifdef CONFIG_SECURITY |
1443 | |
1444 | static const struct lsm_id capability_lsmid = { |
1445 | .name = "capability" , |
1446 | .id = LSM_ID_CAPABILITY, |
1447 | }; |
1448 | |
1449 | static struct security_hook_list capability_hooks[] __ro_after_init = { |
1450 | LSM_HOOK_INIT(capable, cap_capable), |
1451 | LSM_HOOK_INIT(settime, cap_settime), |
1452 | LSM_HOOK_INIT(ptrace_access_check, cap_ptrace_access_check), |
1453 | LSM_HOOK_INIT(ptrace_traceme, cap_ptrace_traceme), |
1454 | LSM_HOOK_INIT(capget, cap_capget), |
1455 | LSM_HOOK_INIT(capset, cap_capset), |
1456 | LSM_HOOK_INIT(bprm_creds_from_file, cap_bprm_creds_from_file), |
1457 | LSM_HOOK_INIT(inode_need_killpriv, cap_inode_need_killpriv), |
1458 | LSM_HOOK_INIT(inode_killpriv, cap_inode_killpriv), |
1459 | LSM_HOOK_INIT(inode_getsecurity, cap_inode_getsecurity), |
1460 | LSM_HOOK_INIT(mmap_addr, cap_mmap_addr), |
1461 | LSM_HOOK_INIT(mmap_file, cap_mmap_file), |
1462 | LSM_HOOK_INIT(task_fix_setuid, cap_task_fix_setuid), |
1463 | LSM_HOOK_INIT(task_prctl, cap_task_prctl), |
1464 | LSM_HOOK_INIT(task_setscheduler, cap_task_setscheduler), |
1465 | LSM_HOOK_INIT(task_setioprio, cap_task_setioprio), |
1466 | LSM_HOOK_INIT(task_setnice, cap_task_setnice), |
1467 | LSM_HOOK_INIT(vm_enough_memory, cap_vm_enough_memory), |
1468 | }; |
1469 | |
1470 | static int __init capability_init(void) |
1471 | { |
1472 | security_add_hooks(hooks: capability_hooks, ARRAY_SIZE(capability_hooks), |
1473 | lsmid: &capability_lsmid); |
1474 | return 0; |
1475 | } |
1476 | |
1477 | DEFINE_LSM(capability) = { |
1478 | .name = "capability" , |
1479 | .order = LSM_ORDER_FIRST, |
1480 | .init = capability_init, |
1481 | }; |
1482 | |
1483 | #endif /* CONFIG_SECURITY */ |
1484 | |