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