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1 | /* Common capabilities, needed by capability.o. | |
2 | * | |
3 | * This program is free software; you can redistribute it and/or modify | |
4 | * it under the terms of the GNU General Public License as published by | |
5 | * the Free Software Foundation; either version 2 of the License, or | |
6 | * (at your option) any later version. | |
7 | * | |
8 | */ | |
9 | ||
10 | #include <linux/capability.h> | |
11 | #include <linux/audit.h> | |
12 | #include <linux/module.h> | |
13 | #include <linux/init.h> | |
14 | #include <linux/kernel.h> | |
15 | #include <linux/lsm_hooks.h> | |
16 | #include <linux/file.h> | |
17 | #include <linux/mm.h> | |
18 | #include <linux/mman.h> | |
19 | #include <linux/pagemap.h> | |
20 | #include <linux/swap.h> | |
21 | #include <linux/skbuff.h> | |
22 | #include <linux/netlink.h> | |
23 | #include <linux/ptrace.h> | |
24 | #include <linux/xattr.h> | |
25 | #include <linux/hugetlb.h> | |
26 | #include <linux/mount.h> | |
27 | #include <linux/sched.h> | |
28 | #include <linux/prctl.h> | |
29 | #include <linux/securebits.h> | |
30 | #include <linux/user_namespace.h> | |
31 | #include <linux/binfmts.h> | |
32 | #include <linux/personality.h> | |
33 | ||
34 | /* | |
35 | * If a non-root user executes a setuid-root binary in | |
36 | * !secure(SECURE_NOROOT) mode, then we raise capabilities. | |
37 | * However if fE is also set, then the intent is for only | |
38 | * the file capabilities to be applied, and the setuid-root | |
39 | * bit is left on either to change the uid (plausible) or | |
40 | * to get full privilege on a kernel without file capabilities | |
41 | * support. So in that case we do not raise capabilities. | |
42 | * | |
43 | * Warn if that happens, once per boot. | |
44 | */ | |
45 | static void warn_setuid_and_fcaps_mixed(const char *fname) | |
46 | { | |
47 | static int warned; | |
48 | if (!warned) { | |
49 | printk(KERN_INFO "warning: `%s' has both setuid-root and" | |
50 | " effective capabilities. Therefore not raising all" | |
51 | " capabilities.\n", fname); | |
52 | warned = 1; | |
53 | } | |
54 | } | |
55 | ||
56 | /** | |
57 | * cap_capable - Determine whether a task has a particular effective capability | |
58 | * @cred: The credentials to use | |
59 | * @ns: The user namespace in which we need the capability | |
60 | * @cap: The capability to check for | |
61 | * @audit: Whether to write an audit message or not | |
62 | * | |
63 | * Determine whether the nominated task has the specified capability amongst | |
64 | * its effective set, returning 0 if it does, -ve if it does not. | |
65 | * | |
66 | * NOTE WELL: cap_has_capability() cannot be used like the kernel's capable() | |
67 | * and has_capability() functions. That is, it has the reverse semantics: | |
68 | * cap_has_capability() returns 0 when a task has a capability, but the | |
69 | * kernel's capable() and has_capability() returns 1 for this case. | |
70 | */ | |
71 | int cap_capable(const struct cred *cred, struct user_namespace *targ_ns, | |
72 | int cap, int audit) | |
73 | { | |
74 | struct user_namespace *ns = targ_ns; | |
75 | ||
76 | /* See if cred has the capability in the target user namespace | |
77 | * by examining the target user namespace and all of the target | |
78 | * user namespace's parents. | |
79 | */ | |
80 | for (;;) { | |
81 | /* Do we have the necessary capabilities? */ | |
82 | if (ns == cred->user_ns) | |
83 | return cap_raised(cred->cap_effective, cap) ? 0 : -EPERM; | |
84 | ||
85 | /* Have we tried all of the parent namespaces? */ | |
86 | if (ns == &init_user_ns) | |
87 | return -EPERM; | |
88 | ||
89 | /* | |
90 | * The owner of the user namespace in the parent of the | |
91 | * user namespace has all caps. | |
92 | */ | |
93 | if ((ns->parent == cred->user_ns) && uid_eq(ns->owner, cred->euid)) | |
94 | return 0; | |
95 | ||
96 | /* | |
97 | * If you have a capability in a parent user ns, then you have | |
98 | * it over all children user namespaces as well. | |
99 | */ | |
100 | ns = ns->parent; | |
101 | } | |
102 | ||
103 | /* We never get here */ | |
104 | } | |
105 | ||
106 | /** | |
107 | * cap_settime - Determine whether the current process may set the system clock | |
108 | * @ts: The time to set | |
109 | * @tz: The timezone to set | |
110 | * | |
111 | * Determine whether the current process may set the system clock and timezone | |
112 | * information, returning 0 if permission granted, -ve if denied. | |
113 | */ | |
114 | int cap_settime(const struct timespec64 *ts, const struct timezone *tz) | |
115 | { | |
116 | if (!capable(CAP_SYS_TIME)) | |
117 | return -EPERM; | |
118 | return 0; | |
119 | } | |
120 | ||
121 | /** | |
122 | * cap_ptrace_access_check - Determine whether the current process may access | |
123 | * another | |
124 | * @child: The process to be accessed | |
125 | * @mode: The mode of attachment. | |
126 | * | |
127 | * If we are in the same or an ancestor user_ns and have all the target | |
128 | * task's capabilities, then ptrace access is allowed. | |
129 | * If we have the ptrace capability to the target user_ns, then ptrace | |
130 | * access is allowed. | |
131 | * Else denied. | |
132 | * | |
133 | * Determine whether a process may access another, returning 0 if permission | |
134 | * granted, -ve if denied. | |
135 | */ | |
136 | int cap_ptrace_access_check(struct task_struct *child, unsigned int mode) | |
137 | { | |
138 | int ret = 0; | |
139 | const struct cred *cred, *child_cred; | |
140 | const kernel_cap_t *caller_caps; | |
141 | ||
142 | rcu_read_lock(); | |
143 | cred = current_cred(); | |
144 | child_cred = __task_cred(child); | |
145 | if (mode & PTRACE_MODE_FSCREDS) | |
146 | caller_caps = &cred->cap_effective; | |
147 | else | |
148 | caller_caps = &cred->cap_permitted; | |
149 | if (cred->user_ns == child_cred->user_ns && | |
150 | cap_issubset(child_cred->cap_permitted, *caller_caps)) | |
151 | goto out; | |
152 | if (ns_capable(child_cred->user_ns, CAP_SYS_PTRACE)) | |
153 | goto out; | |
154 | ret = -EPERM; | |
155 | out: | |
156 | rcu_read_unlock(); | |
157 | return ret; | |
158 | } | |
159 | ||
160 | /** | |
161 | * cap_ptrace_traceme - Determine whether another process may trace the current | |
162 | * @parent: The task proposed to be the tracer | |
163 | * | |
164 | * If parent is in the same or an ancestor user_ns and has all current's | |
165 | * capabilities, then ptrace access is allowed. | |
166 | * If parent has the ptrace capability to current's user_ns, then ptrace | |
167 | * access is allowed. | |
168 | * Else denied. | |
169 | * | |
170 | * Determine whether the nominated task is permitted to trace the current | |
171 | * process, returning 0 if permission is granted, -ve if denied. | |
172 | */ | |
173 | int cap_ptrace_traceme(struct task_struct *parent) | |
174 | { | |
175 | int ret = 0; | |
176 | const struct cred *cred, *child_cred; | |
177 | ||
178 | rcu_read_lock(); | |
179 | cred = __task_cred(parent); | |
180 | child_cred = current_cred(); | |
181 | if (cred->user_ns == child_cred->user_ns && | |
182 | cap_issubset(child_cred->cap_permitted, cred->cap_permitted)) | |
183 | goto out; | |
184 | if (has_ns_capability(parent, child_cred->user_ns, CAP_SYS_PTRACE)) | |
185 | goto out; | |
186 | ret = -EPERM; | |
187 | out: | |
188 | rcu_read_unlock(); | |
189 | return ret; | |
190 | } | |
191 | ||
192 | /** | |
193 | * cap_capget - Retrieve a task's capability sets | |
194 | * @target: The task from which to retrieve the capability sets | |
195 | * @effective: The place to record the effective set | |
196 | * @inheritable: The place to record the inheritable set | |
197 | * @permitted: The place to record the permitted set | |
198 | * | |
199 | * This function retrieves the capabilities of the nominated task and returns | |
200 | * them to the caller. | |
201 | */ | |
202 | int cap_capget(struct task_struct *target, kernel_cap_t *effective, | |
203 | kernel_cap_t *inheritable, kernel_cap_t *permitted) | |
204 | { | |
205 | const struct cred *cred; | |
206 | ||
207 | /* Derived from kernel/capability.c:sys_capget. */ | |
208 | rcu_read_lock(); | |
209 | cred = __task_cred(target); | |
210 | *effective = cred->cap_effective; | |
211 | *inheritable = cred->cap_inheritable; | |
212 | *permitted = cred->cap_permitted; | |
213 | rcu_read_unlock(); | |
214 | return 0; | |
215 | } | |
216 | ||
217 | /* | |
218 | * Determine whether the inheritable capabilities are limited to the old | |
219 | * permitted set. Returns 1 if they are limited, 0 if they are not. | |
220 | */ | |
221 | static inline int cap_inh_is_capped(void) | |
222 | { | |
223 | ||
224 | /* they are so limited unless the current task has the CAP_SETPCAP | |
225 | * capability | |
226 | */ | |
227 | if (cap_capable(current_cred(), current_cred()->user_ns, | |
228 | CAP_SETPCAP, SECURITY_CAP_AUDIT) == 0) | |
229 | return 0; | |
230 | return 1; | |
231 | } | |
232 | ||
233 | /** | |
234 | * cap_capset - Validate and apply proposed changes to current's capabilities | |
235 | * @new: The proposed new credentials; alterations should be made here | |
236 | * @old: The current task's current credentials | |
237 | * @effective: A pointer to the proposed new effective capabilities set | |
238 | * @inheritable: A pointer to the proposed new inheritable capabilities set | |
239 | * @permitted: A pointer to the proposed new permitted capabilities set | |
240 | * | |
241 | * This function validates and applies a proposed mass change to the current | |
242 | * process's capability sets. The changes are made to the proposed new | |
243 | * credentials, and assuming no error, will be committed by the caller of LSM. | |
244 | */ | |
245 | int cap_capset(struct cred *new, | |
246 | const struct cred *old, | |
247 | const kernel_cap_t *effective, | |
248 | const kernel_cap_t *inheritable, | |
249 | const kernel_cap_t *permitted) | |
250 | { | |
251 | if (cap_inh_is_capped() && | |
252 | !cap_issubset(*inheritable, | |
253 | cap_combine(old->cap_inheritable, | |
254 | old->cap_permitted))) | |
255 | /* incapable of using this inheritable set */ | |
256 | return -EPERM; | |
257 | ||
258 | if (!cap_issubset(*inheritable, | |
259 | cap_combine(old->cap_inheritable, | |
260 | old->cap_bset))) | |
261 | /* no new pI capabilities outside bounding set */ | |
262 | return -EPERM; | |
263 | ||
264 | /* verify restrictions on target's new Permitted set */ | |
265 | if (!cap_issubset(*permitted, old->cap_permitted)) | |
266 | return -EPERM; | |
267 | ||
268 | /* verify the _new_Effective_ is a subset of the _new_Permitted_ */ | |
269 | if (!cap_issubset(*effective, *permitted)) | |
270 | return -EPERM; | |
271 | ||
272 | new->cap_effective = *effective; | |
273 | new->cap_inheritable = *inheritable; | |
274 | new->cap_permitted = *permitted; | |
275 | ||
276 | /* | |
277 | * Mask off ambient bits that are no longer both permitted and | |
278 | * inheritable. | |
279 | */ | |
280 | new->cap_ambient = cap_intersect(new->cap_ambient, | |
281 | cap_intersect(*permitted, | |
282 | *inheritable)); | |
283 | if (WARN_ON(!cap_ambient_invariant_ok(new))) | |
284 | return -EINVAL; | |
285 | return 0; | |
286 | } | |
287 | ||
288 | /* | |
289 | * Clear proposed capability sets for execve(). | |
290 | */ | |
291 | static inline void bprm_clear_caps(struct linux_binprm *bprm) | |
292 | { | |
293 | cap_clear(bprm->cred->cap_permitted); | |
294 | bprm->cap_effective = false; | |
295 | } | |
296 | ||
297 | /** | |
298 | * cap_inode_need_killpriv - Determine if inode change affects privileges | |
299 | * @dentry: The inode/dentry in being changed with change marked ATTR_KILL_PRIV | |
300 | * | |
301 | * Determine if an inode having a change applied that's marked ATTR_KILL_PRIV | |
302 | * affects the security markings on that inode, and if it is, should | |
303 | * inode_killpriv() be invoked or the change rejected? | |
304 | * | |
305 | * Returns 0 if granted; +ve if granted, but inode_killpriv() is required; and | |
306 | * -ve to deny the change. | |
307 | */ | |
308 | int cap_inode_need_killpriv(struct dentry *dentry) | |
309 | { | |
310 | struct inode *inode = d_backing_inode(dentry); | |
311 | int error; | |
312 | ||
313 | error = __vfs_getxattr(dentry, inode, XATTR_NAME_CAPS, NULL, 0); | |
314 | return error > 0; | |
315 | } | |
316 | ||
317 | /** | |
318 | * cap_inode_killpriv - Erase the security markings on an inode | |
319 | * @dentry: The inode/dentry to alter | |
320 | * | |
321 | * Erase the privilege-enhancing security markings on an inode. | |
322 | * | |
323 | * Returns 0 if successful, -ve on error. | |
324 | */ | |
325 | int cap_inode_killpriv(struct dentry *dentry) | |
326 | { | |
327 | int error; | |
328 | ||
329 | error = __vfs_removexattr(dentry, XATTR_NAME_CAPS); | |
330 | if (error == -EOPNOTSUPP) | |
331 | error = 0; | |
332 | return error; | |
333 | } | |
334 | ||
335 | /* | |
336 | * Calculate the new process capability sets from the capability sets attached | |
337 | * to a file. | |
338 | */ | |
339 | static inline int bprm_caps_from_vfs_caps(struct cpu_vfs_cap_data *caps, | |
340 | struct linux_binprm *bprm, | |
341 | bool *effective, | |
342 | bool *has_cap) | |
343 | { | |
344 | struct cred *new = bprm->cred; | |
345 | unsigned i; | |
346 | int ret = 0; | |
347 | ||
348 | if (caps->magic_etc & VFS_CAP_FLAGS_EFFECTIVE) | |
349 | *effective = true; | |
350 | ||
351 | if (caps->magic_etc & VFS_CAP_REVISION_MASK) | |
352 | *has_cap = true; | |
353 | ||
354 | CAP_FOR_EACH_U32(i) { | |
355 | __u32 permitted = caps->permitted.cap[i]; | |
356 | __u32 inheritable = caps->inheritable.cap[i]; | |
357 | ||
358 | /* | |
359 | * pP' = (X & fP) | (pI & fI) | |
360 | * The addition of pA' is handled later. | |
361 | */ | |
362 | new->cap_permitted.cap[i] = | |
363 | (new->cap_bset.cap[i] & permitted) | | |
364 | (new->cap_inheritable.cap[i] & inheritable); | |
365 | ||
366 | if (permitted & ~new->cap_permitted.cap[i]) | |
367 | /* insufficient to execute correctly */ | |
368 | ret = -EPERM; | |
369 | } | |
370 | ||
371 | /* | |
372 | * For legacy apps, with no internal support for recognizing they | |
373 | * do not have enough capabilities, we return an error if they are | |
374 | * missing some "forced" (aka file-permitted) capabilities. | |
375 | */ | |
376 | return *effective ? ret : 0; | |
377 | } | |
378 | ||
379 | /* | |
380 | * Extract the on-exec-apply capability sets for an executable file. | |
381 | */ | |
382 | int get_vfs_caps_from_disk(const struct dentry *dentry, struct cpu_vfs_cap_data *cpu_caps) | |
383 | { | |
384 | struct inode *inode = d_backing_inode(dentry); | |
385 | __u32 magic_etc; | |
386 | unsigned tocopy, i; | |
387 | int size; | |
388 | struct vfs_cap_data caps; | |
389 | ||
390 | memset(cpu_caps, 0, sizeof(struct cpu_vfs_cap_data)); | |
391 | ||
392 | if (!inode) | |
393 | return -ENODATA; | |
394 | ||
395 | size = __vfs_getxattr((struct dentry *)dentry, inode, | |
396 | XATTR_NAME_CAPS, &caps, XATTR_CAPS_SZ); | |
397 | if (size == -ENODATA || size == -EOPNOTSUPP) | |
398 | /* no data, that's ok */ | |
399 | return -ENODATA; | |
400 | if (size < 0) | |
401 | return size; | |
402 | ||
403 | if (size < sizeof(magic_etc)) | |
404 | return -EINVAL; | |
405 | ||
406 | cpu_caps->magic_etc = magic_etc = le32_to_cpu(caps.magic_etc); | |
407 | ||
408 | switch (magic_etc & VFS_CAP_REVISION_MASK) { | |
409 | case VFS_CAP_REVISION_1: | |
410 | if (size != XATTR_CAPS_SZ_1) | |
411 | return -EINVAL; | |
412 | tocopy = VFS_CAP_U32_1; | |
413 | break; | |
414 | case VFS_CAP_REVISION_2: | |
415 | if (size != XATTR_CAPS_SZ_2) | |
416 | return -EINVAL; | |
417 | tocopy = VFS_CAP_U32_2; | |
418 | break; | |
419 | default: | |
420 | return -EINVAL; | |
421 | } | |
422 | ||
423 | CAP_FOR_EACH_U32(i) { | |
424 | if (i >= tocopy) | |
425 | break; | |
426 | cpu_caps->permitted.cap[i] = le32_to_cpu(caps.data[i].permitted); | |
427 | cpu_caps->inheritable.cap[i] = le32_to_cpu(caps.data[i].inheritable); | |
428 | } | |
429 | ||
430 | cpu_caps->permitted.cap[CAP_LAST_U32] &= CAP_LAST_U32_VALID_MASK; | |
431 | cpu_caps->inheritable.cap[CAP_LAST_U32] &= CAP_LAST_U32_VALID_MASK; | |
432 | ||
433 | return 0; | |
434 | } | |
435 | ||
436 | /* | |
437 | * Attempt to get the on-exec apply capability sets for an executable file from | |
438 | * its xattrs and, if present, apply them to the proposed credentials being | |
439 | * constructed by execve(). | |
440 | */ | |
441 | static int get_file_caps(struct linux_binprm *bprm, bool *effective, bool *has_cap) | |
442 | { | |
443 | int rc = 0; | |
444 | struct cpu_vfs_cap_data vcaps; | |
445 | ||
446 | bprm_clear_caps(bprm); | |
447 | ||
448 | if (!file_caps_enabled) | |
449 | return 0; | |
450 | ||
451 | if (!mnt_may_suid(bprm->file->f_path.mnt)) | |
452 | return 0; | |
453 | ||
454 | /* | |
455 | * This check is redundant with mnt_may_suid() but is kept to make | |
456 | * explicit that capability bits are limited to s_user_ns and its | |
457 | * descendants. | |
458 | */ | |
459 | if (!current_in_userns(bprm->file->f_path.mnt->mnt_sb->s_user_ns)) | |
460 | return 0; | |
461 | ||
462 | rc = get_vfs_caps_from_disk(bprm->file->f_path.dentry, &vcaps); | |
463 | if (rc < 0) { | |
464 | if (rc == -EINVAL) | |
465 | printk(KERN_NOTICE "%s: get_vfs_caps_from_disk returned %d for %s\n", | |
466 | __func__, rc, bprm->filename); | |
467 | else if (rc == -ENODATA) | |
468 | rc = 0; | |
469 | goto out; | |
470 | } | |
471 | ||
472 | rc = bprm_caps_from_vfs_caps(&vcaps, bprm, effective, has_cap); | |
473 | if (rc == -EINVAL) | |
474 | printk(KERN_NOTICE "%s: cap_from_disk returned %d for %s\n", | |
475 | __func__, rc, bprm->filename); | |
476 | ||
477 | out: | |
478 | if (rc) | |
479 | bprm_clear_caps(bprm); | |
480 | ||
481 | return rc; | |
482 | } | |
483 | ||
484 | /** | |
485 | * cap_bprm_set_creds - Set up the proposed credentials for execve(). | |
486 | * @bprm: The execution parameters, including the proposed creds | |
487 | * | |
488 | * Set up the proposed credentials for a new execution context being | |
489 | * constructed by execve(). The proposed creds in @bprm->cred is altered, | |
490 | * which won't take effect immediately. Returns 0 if successful, -ve on error. | |
491 | */ | |
492 | int cap_bprm_set_creds(struct linux_binprm *bprm) | |
493 | { | |
494 | const struct cred *old = current_cred(); | |
495 | struct cred *new = bprm->cred; | |
496 | bool effective, has_cap = false, is_setid; | |
497 | int ret; | |
498 | kuid_t root_uid; | |
499 | ||
500 | if (WARN_ON(!cap_ambient_invariant_ok(old))) | |
501 | return -EPERM; | |
502 | ||
503 | effective = false; | |
504 | ret = get_file_caps(bprm, &effective, &has_cap); | |
505 | if (ret < 0) | |
506 | return ret; | |
507 | ||
508 | root_uid = make_kuid(new->user_ns, 0); | |
509 | ||
510 | if (!issecure(SECURE_NOROOT)) { | |
511 | /* | |
512 | * If the legacy file capability is set, then don't set privs | |
513 | * for a setuid root binary run by a non-root user. Do set it | |
514 | * for a root user just to cause least surprise to an admin. | |
515 | */ | |
516 | if (has_cap && !uid_eq(new->uid, root_uid) && uid_eq(new->euid, root_uid)) { | |
517 | warn_setuid_and_fcaps_mixed(bprm->filename); | |
518 | goto skip; | |
519 | } | |
520 | /* | |
521 | * To support inheritance of root-permissions and suid-root | |
522 | * executables under compatibility mode, we override the | |
523 | * capability sets for the file. | |
524 | * | |
525 | * If only the real uid is 0, we do not set the effective bit. | |
526 | */ | |
527 | if (uid_eq(new->euid, root_uid) || uid_eq(new->uid, root_uid)) { | |
528 | /* pP' = (cap_bset & ~0) | (pI & ~0) */ | |
529 | new->cap_permitted = cap_combine(old->cap_bset, | |
530 | old->cap_inheritable); | |
531 | } | |
532 | if (uid_eq(new->euid, root_uid)) | |
533 | effective = true; | |
534 | } | |
535 | skip: | |
536 | ||
537 | /* if we have fs caps, clear dangerous personality flags */ | |
538 | if (!cap_issubset(new->cap_permitted, old->cap_permitted)) | |
539 | bprm->per_clear |= PER_CLEAR_ON_SETID; | |
540 | ||
541 | ||
542 | /* Don't let someone trace a set[ug]id/setpcap binary with the revised | |
543 | * credentials unless they have the appropriate permit. | |
544 | * | |
545 | * In addition, if NO_NEW_PRIVS, then ensure we get no new privs. | |
546 | */ | |
547 | is_setid = !uid_eq(new->euid, old->uid) || !gid_eq(new->egid, old->gid); | |
548 | ||
549 | if ((is_setid || | |
550 | !cap_issubset(new->cap_permitted, old->cap_permitted)) && | |
551 | bprm->unsafe & ~LSM_UNSAFE_PTRACE_CAP) { | |
552 | /* downgrade; they get no more than they had, and maybe less */ | |
553 | if (!capable(CAP_SETUID) || | |
554 | (bprm->unsafe & LSM_UNSAFE_NO_NEW_PRIVS)) { | |
555 | new->euid = new->uid; | |
556 | new->egid = new->gid; | |
557 | } | |
558 | new->cap_permitted = cap_intersect(new->cap_permitted, | |
559 | old->cap_permitted); | |
560 | } | |
561 | ||
562 | new->suid = new->fsuid = new->euid; | |
563 | new->sgid = new->fsgid = new->egid; | |
564 | ||
565 | /* File caps or setid cancels ambient. */ | |
566 | if (has_cap || is_setid) | |
567 | cap_clear(new->cap_ambient); | |
568 | ||
569 | /* | |
570 | * Now that we've computed pA', update pP' to give: | |
571 | * pP' = (X & fP) | (pI & fI) | pA' | |
572 | */ | |
573 | new->cap_permitted = cap_combine(new->cap_permitted, new->cap_ambient); | |
574 | ||
575 | /* | |
576 | * Set pE' = (fE ? pP' : pA'). Because pA' is zero if fE is set, | |
577 | * this is the same as pE' = (fE ? pP' : 0) | pA'. | |
578 | */ | |
579 | if (effective) | |
580 | new->cap_effective = new->cap_permitted; | |
581 | else | |
582 | new->cap_effective = new->cap_ambient; | |
583 | ||
584 | if (WARN_ON(!cap_ambient_invariant_ok(new))) | |
585 | return -EPERM; | |
586 | ||
587 | bprm->cap_effective = effective; | |
588 | ||
589 | /* | |
590 | * Audit candidate if current->cap_effective is set | |
591 | * | |
592 | * We do not bother to audit if 3 things are true: | |
593 | * 1) cap_effective has all caps | |
594 | * 2) we are root | |
595 | * 3) root is supposed to have all caps (SECURE_NOROOT) | |
596 | * Since this is just a normal root execing a process. | |
597 | * | |
598 | * Number 1 above might fail if you don't have a full bset, but I think | |
599 | * that is interesting information to audit. | |
600 | */ | |
601 | if (!cap_issubset(new->cap_effective, new->cap_ambient)) { | |
602 | if (!cap_issubset(CAP_FULL_SET, new->cap_effective) || | |
603 | !uid_eq(new->euid, root_uid) || !uid_eq(new->uid, root_uid) || | |
604 | issecure(SECURE_NOROOT)) { | |
605 | ret = audit_log_bprm_fcaps(bprm, new, old); | |
606 | if (ret < 0) | |
607 | return ret; | |
608 | } | |
609 | } | |
610 | ||
611 | new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS); | |
612 | ||
613 | if (WARN_ON(!cap_ambient_invariant_ok(new))) | |
614 | return -EPERM; | |
615 | ||
616 | return 0; | |
617 | } | |
618 | ||
619 | /** | |
620 | * cap_bprm_secureexec - Determine whether a secure execution is required | |
621 | * @bprm: The execution parameters | |
622 | * | |
623 | * Determine whether a secure execution is required, return 1 if it is, and 0 | |
624 | * if it is not. | |
625 | * | |
626 | * The credentials have been committed by this point, and so are no longer | |
627 | * available through @bprm->cred. | |
628 | */ | |
629 | int cap_bprm_secureexec(struct linux_binprm *bprm) | |
630 | { | |
631 | const struct cred *cred = current_cred(); | |
632 | kuid_t root_uid = make_kuid(cred->user_ns, 0); | |
633 | ||
634 | if (!uid_eq(cred->uid, root_uid)) { | |
635 | if (bprm->cap_effective) | |
636 | return 1; | |
637 | if (!cap_issubset(cred->cap_permitted, cred->cap_ambient)) | |
638 | return 1; | |
639 | } | |
640 | ||
641 | return (!uid_eq(cred->euid, cred->uid) || | |
642 | !gid_eq(cred->egid, cred->gid)); | |
643 | } | |
644 | ||
645 | /** | |
646 | * cap_inode_setxattr - Determine whether an xattr may be altered | |
647 | * @dentry: The inode/dentry being altered | |
648 | * @name: The name of the xattr to be changed | |
649 | * @value: The value that the xattr will be changed to | |
650 | * @size: The size of value | |
651 | * @flags: The replacement flag | |
652 | * | |
653 | * Determine whether an xattr may be altered or set on an inode, returning 0 if | |
654 | * permission is granted, -ve if denied. | |
655 | * | |
656 | * This is used to make sure security xattrs don't get updated or set by those | |
657 | * who aren't privileged to do so. | |
658 | */ | |
659 | int cap_inode_setxattr(struct dentry *dentry, const char *name, | |
660 | const void *value, size_t size, int flags) | |
661 | { | |
662 | if (!strcmp(name, XATTR_NAME_CAPS)) { | |
663 | if (!capable(CAP_SETFCAP)) | |
664 | return -EPERM; | |
665 | return 0; | |
666 | } | |
667 | ||
668 | if (!strncmp(name, XATTR_SECURITY_PREFIX, | |
669 | sizeof(XATTR_SECURITY_PREFIX) - 1) && | |
670 | !capable(CAP_SYS_ADMIN)) | |
671 | return -EPERM; | |
672 | return 0; | |
673 | } | |
674 | ||
675 | /** | |
676 | * cap_inode_removexattr - Determine whether an xattr may be removed | |
677 | * @dentry: The inode/dentry being altered | |
678 | * @name: The name of the xattr to be changed | |
679 | * | |
680 | * Determine whether an xattr may be removed from an inode, returning 0 if | |
681 | * permission is granted, -ve if denied. | |
682 | * | |
683 | * This is used to make sure security xattrs don't get removed by those who | |
684 | * aren't privileged to remove them. | |
685 | */ | |
686 | int cap_inode_removexattr(struct dentry *dentry, const char *name) | |
687 | { | |
688 | if (!strcmp(name, XATTR_NAME_CAPS)) { | |
689 | if (!capable(CAP_SETFCAP)) | |
690 | return -EPERM; | |
691 | return 0; | |
692 | } | |
693 | ||
694 | if (!strncmp(name, XATTR_SECURITY_PREFIX, | |
695 | sizeof(XATTR_SECURITY_PREFIX) - 1) && | |
696 | !capable(CAP_SYS_ADMIN)) | |
697 | return -EPERM; | |
698 | return 0; | |
699 | } | |
700 | ||
701 | /* | |
702 | * cap_emulate_setxuid() fixes the effective / permitted capabilities of | |
703 | * a process after a call to setuid, setreuid, or setresuid. | |
704 | * | |
705 | * 1) When set*uiding _from_ one of {r,e,s}uid == 0 _to_ all of | |
706 | * {r,e,s}uid != 0, the permitted and effective capabilities are | |
707 | * cleared. | |
708 | * | |
709 | * 2) When set*uiding _from_ euid == 0 _to_ euid != 0, the effective | |
710 | * capabilities of the process are cleared. | |
711 | * | |
712 | * 3) When set*uiding _from_ euid != 0 _to_ euid == 0, the effective | |
713 | * capabilities are set to the permitted capabilities. | |
714 | * | |
715 | * fsuid is handled elsewhere. fsuid == 0 and {r,e,s}uid!= 0 should | |
716 | * never happen. | |
717 | * | |
718 | * -astor | |
719 | * | |
720 | * cevans - New behaviour, Oct '99 | |
721 | * A process may, via prctl(), elect to keep its capabilities when it | |
722 | * calls setuid() and switches away from uid==0. Both permitted and | |
723 | * effective sets will be retained. | |
724 | * Without this change, it was impossible for a daemon to drop only some | |
725 | * of its privilege. The call to setuid(!=0) would drop all privileges! | |
726 | * Keeping uid 0 is not an option because uid 0 owns too many vital | |
727 | * files.. | |
728 | * Thanks to Olaf Kirch and Peter Benie for spotting this. | |
729 | */ | |
730 | static inline void cap_emulate_setxuid(struct cred *new, const struct cred *old) | |
731 | { | |
732 | kuid_t root_uid = make_kuid(old->user_ns, 0); | |
733 | ||
734 | if ((uid_eq(old->uid, root_uid) || | |
735 | uid_eq(old->euid, root_uid) || | |
736 | uid_eq(old->suid, root_uid)) && | |
737 | (!uid_eq(new->uid, root_uid) && | |
738 | !uid_eq(new->euid, root_uid) && | |
739 | !uid_eq(new->suid, root_uid))) { | |
740 | if (!issecure(SECURE_KEEP_CAPS)) { | |
741 | cap_clear(new->cap_permitted); | |
742 | cap_clear(new->cap_effective); | |
743 | } | |
744 | ||
745 | /* | |
746 | * Pre-ambient programs expect setresuid to nonroot followed | |
747 | * by exec to drop capabilities. We should make sure that | |
748 | * this remains the case. | |
749 | */ | |
750 | cap_clear(new->cap_ambient); | |
751 | } | |
752 | if (uid_eq(old->euid, root_uid) && !uid_eq(new->euid, root_uid)) | |
753 | cap_clear(new->cap_effective); | |
754 | if (!uid_eq(old->euid, root_uid) && uid_eq(new->euid, root_uid)) | |
755 | new->cap_effective = new->cap_permitted; | |
756 | } | |
757 | ||
758 | /** | |
759 | * cap_task_fix_setuid - Fix up the results of setuid() call | |
760 | * @new: The proposed credentials | |
761 | * @old: The current task's current credentials | |
762 | * @flags: Indications of what has changed | |
763 | * | |
764 | * Fix up the results of setuid() call before the credential changes are | |
765 | * actually applied, returning 0 to grant the changes, -ve to deny them. | |
766 | */ | |
767 | int cap_task_fix_setuid(struct cred *new, const struct cred *old, int flags) | |
768 | { | |
769 | switch (flags) { | |
770 | case LSM_SETID_RE: | |
771 | case LSM_SETID_ID: | |
772 | case LSM_SETID_RES: | |
773 | /* juggle the capabilities to follow [RES]UID changes unless | |
774 | * otherwise suppressed */ | |
775 | if (!issecure(SECURE_NO_SETUID_FIXUP)) | |
776 | cap_emulate_setxuid(new, old); | |
777 | break; | |
778 | ||
779 | case LSM_SETID_FS: | |
780 | /* juggle the capabilties to follow FSUID changes, unless | |
781 | * otherwise suppressed | |
782 | * | |
783 | * FIXME - is fsuser used for all CAP_FS_MASK capabilities? | |
784 | * if not, we might be a bit too harsh here. | |
785 | */ | |
786 | if (!issecure(SECURE_NO_SETUID_FIXUP)) { | |
787 | kuid_t root_uid = make_kuid(old->user_ns, 0); | |
788 | if (uid_eq(old->fsuid, root_uid) && !uid_eq(new->fsuid, root_uid)) | |
789 | new->cap_effective = | |
790 | cap_drop_fs_set(new->cap_effective); | |
791 | ||
792 | if (!uid_eq(old->fsuid, root_uid) && uid_eq(new->fsuid, root_uid)) | |
793 | new->cap_effective = | |
794 | cap_raise_fs_set(new->cap_effective, | |
795 | new->cap_permitted); | |
796 | } | |
797 | break; | |
798 | ||
799 | default: | |
800 | return -EINVAL; | |
801 | } | |
802 | ||
803 | return 0; | |
804 | } | |
805 | ||
806 | /* | |
807 | * Rationale: code calling task_setscheduler, task_setioprio, and | |
808 | * task_setnice, assumes that | |
809 | * . if capable(cap_sys_nice), then those actions should be allowed | |
810 | * . if not capable(cap_sys_nice), but acting on your own processes, | |
811 | * then those actions should be allowed | |
812 | * This is insufficient now since you can call code without suid, but | |
813 | * yet with increased caps. | |
814 | * So we check for increased caps on the target process. | |
815 | */ | |
816 | static int cap_safe_nice(struct task_struct *p) | |
817 | { | |
818 | int is_subset, ret = 0; | |
819 | ||
820 | rcu_read_lock(); | |
821 | is_subset = cap_issubset(__task_cred(p)->cap_permitted, | |
822 | current_cred()->cap_permitted); | |
823 | if (!is_subset && !ns_capable(__task_cred(p)->user_ns, CAP_SYS_NICE)) | |
824 | ret = -EPERM; | |
825 | rcu_read_unlock(); | |
826 | ||
827 | return ret; | |
828 | } | |
829 | ||
830 | /** | |
831 | * cap_task_setscheduler - Detemine if scheduler policy change is permitted | |
832 | * @p: The task to affect | |
833 | * | |
834 | * Detemine if the requested scheduler policy change is permitted for the | |
835 | * specified task, returning 0 if permission is granted, -ve if denied. | |
836 | */ | |
837 | int cap_task_setscheduler(struct task_struct *p) | |
838 | { | |
839 | return cap_safe_nice(p); | |
840 | } | |
841 | ||
842 | /** | |
843 | * cap_task_ioprio - Detemine if I/O priority change is permitted | |
844 | * @p: The task to affect | |
845 | * @ioprio: The I/O priority to set | |
846 | * | |
847 | * Detemine if the requested I/O priority change is permitted for the specified | |
848 | * task, returning 0 if permission is granted, -ve if denied. | |
849 | */ | |
850 | int cap_task_setioprio(struct task_struct *p, int ioprio) | |
851 | { | |
852 | return cap_safe_nice(p); | |
853 | } | |
854 | ||
855 | /** | |
856 | * cap_task_ioprio - Detemine if task priority change is permitted | |
857 | * @p: The task to affect | |
858 | * @nice: The nice value to set | |
859 | * | |
860 | * Detemine if the requested task priority change is permitted for the | |
861 | * specified task, returning 0 if permission is granted, -ve if denied. | |
862 | */ | |
863 | int cap_task_setnice(struct task_struct *p, int nice) | |
864 | { | |
865 | return cap_safe_nice(p); | |
866 | } | |
867 | ||
868 | /* | |
869 | * Implement PR_CAPBSET_DROP. Attempt to remove the specified capability from | |
870 | * the current task's bounding set. Returns 0 on success, -ve on error. | |
871 | */ | |
872 | static int cap_prctl_drop(unsigned long cap) | |
873 | { | |
874 | struct cred *new; | |
875 | ||
876 | if (!ns_capable(current_user_ns(), CAP_SETPCAP)) | |
877 | return -EPERM; | |
878 | if (!cap_valid(cap)) | |
879 | return -EINVAL; | |
880 | ||
881 | new = prepare_creds(); | |
882 | if (!new) | |
883 | return -ENOMEM; | |
884 | cap_lower(new->cap_bset, cap); | |
885 | return commit_creds(new); | |
886 | } | |
887 | ||
888 | /** | |
889 | * cap_task_prctl - Implement process control functions for this security module | |
890 | * @option: The process control function requested | |
891 | * @arg2, @arg3, @arg4, @arg5: The argument data for this function | |
892 | * | |
893 | * Allow process control functions (sys_prctl()) to alter capabilities; may | |
894 | * also deny access to other functions not otherwise implemented here. | |
895 | * | |
896 | * Returns 0 or +ve on success, -ENOSYS if this function is not implemented | |
897 | * here, other -ve on error. If -ENOSYS is returned, sys_prctl() and other LSM | |
898 | * modules will consider performing the function. | |
899 | */ | |
900 | int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3, | |
901 | unsigned long arg4, unsigned long arg5) | |
902 | { | |
903 | const struct cred *old = current_cred(); | |
904 | struct cred *new; | |
905 | ||
906 | switch (option) { | |
907 | case PR_CAPBSET_READ: | |
908 | if (!cap_valid(arg2)) | |
909 | return -EINVAL; | |
910 | return !!cap_raised(old->cap_bset, arg2); | |
911 | ||
912 | case PR_CAPBSET_DROP: | |
913 | return cap_prctl_drop(arg2); | |
914 | ||
915 | /* | |
916 | * The next four prctl's remain to assist with transitioning a | |
917 | * system from legacy UID=0 based privilege (when filesystem | |
918 | * capabilities are not in use) to a system using filesystem | |
919 | * capabilities only - as the POSIX.1e draft intended. | |
920 | * | |
921 | * Note: | |
922 | * | |
923 | * PR_SET_SECUREBITS = | |
924 | * issecure_mask(SECURE_KEEP_CAPS_LOCKED) | |
925 | * | issecure_mask(SECURE_NOROOT) | |
926 | * | issecure_mask(SECURE_NOROOT_LOCKED) | |
927 | * | issecure_mask(SECURE_NO_SETUID_FIXUP) | |
928 | * | issecure_mask(SECURE_NO_SETUID_FIXUP_LOCKED) | |
929 | * | |
930 | * will ensure that the current process and all of its | |
931 | * children will be locked into a pure | |
932 | * capability-based-privilege environment. | |
933 | */ | |
934 | case PR_SET_SECUREBITS: | |
935 | if ((((old->securebits & SECURE_ALL_LOCKS) >> 1) | |
936 | & (old->securebits ^ arg2)) /*[1]*/ | |
937 | || ((old->securebits & SECURE_ALL_LOCKS & ~arg2)) /*[2]*/ | |
938 | || (arg2 & ~(SECURE_ALL_LOCKS | SECURE_ALL_BITS)) /*[3]*/ | |
939 | || (cap_capable(current_cred(), | |
940 | current_cred()->user_ns, CAP_SETPCAP, | |
941 | SECURITY_CAP_AUDIT) != 0) /*[4]*/ | |
942 | /* | |
943 | * [1] no changing of bits that are locked | |
944 | * [2] no unlocking of locks | |
945 | * [3] no setting of unsupported bits | |
946 | * [4] doing anything requires privilege (go read about | |
947 | * the "sendmail capabilities bug") | |
948 | */ | |
949 | ) | |
950 | /* cannot change a locked bit */ | |
951 | return -EPERM; | |
952 | ||
953 | new = prepare_creds(); | |
954 | if (!new) | |
955 | return -ENOMEM; | |
956 | new->securebits = arg2; | |
957 | return commit_creds(new); | |
958 | ||
959 | case PR_GET_SECUREBITS: | |
960 | return old->securebits; | |
961 | ||
962 | case PR_GET_KEEPCAPS: | |
963 | return !!issecure(SECURE_KEEP_CAPS); | |
964 | ||
965 | case PR_SET_KEEPCAPS: | |
966 | if (arg2 > 1) /* Note, we rely on arg2 being unsigned here */ | |
967 | return -EINVAL; | |
968 | if (issecure(SECURE_KEEP_CAPS_LOCKED)) | |
969 | return -EPERM; | |
970 | ||
971 | new = prepare_creds(); | |
972 | if (!new) | |
973 | return -ENOMEM; | |
974 | if (arg2) | |
975 | new->securebits |= issecure_mask(SECURE_KEEP_CAPS); | |
976 | else | |
977 | new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS); | |
978 | return commit_creds(new); | |
979 | ||
980 | case PR_CAP_AMBIENT: | |
981 | if (arg2 == PR_CAP_AMBIENT_CLEAR_ALL) { | |
982 | if (arg3 | arg4 | arg5) | |
983 | return -EINVAL; | |
984 | ||
985 | new = prepare_creds(); | |
986 | if (!new) | |
987 | return -ENOMEM; | |
988 | cap_clear(new->cap_ambient); | |
989 | return commit_creds(new); | |
990 | } | |
991 | ||
992 | if (((!cap_valid(arg3)) | arg4 | arg5)) | |
993 | return -EINVAL; | |
994 | ||
995 | if (arg2 == PR_CAP_AMBIENT_IS_SET) { | |
996 | return !!cap_raised(current_cred()->cap_ambient, arg3); | |
997 | } else if (arg2 != PR_CAP_AMBIENT_RAISE && | |
998 | arg2 != PR_CAP_AMBIENT_LOWER) { | |
999 | return -EINVAL; | |
1000 | } else { | |
1001 | if (arg2 == PR_CAP_AMBIENT_RAISE && | |
1002 | (!cap_raised(current_cred()->cap_permitted, arg3) || | |
1003 | !cap_raised(current_cred()->cap_inheritable, | |
1004 | arg3) || | |
1005 | issecure(SECURE_NO_CAP_AMBIENT_RAISE))) | |
1006 | return -EPERM; | |
1007 | ||
1008 | new = prepare_creds(); | |
1009 | if (!new) | |
1010 | return -ENOMEM; | |
1011 | if (arg2 == PR_CAP_AMBIENT_RAISE) | |
1012 | cap_raise(new->cap_ambient, arg3); | |
1013 | else | |
1014 | cap_lower(new->cap_ambient, arg3); | |
1015 | return commit_creds(new); | |
1016 | } | |
1017 | ||
1018 | default: | |
1019 | /* No functionality available - continue with default */ | |
1020 | return -ENOSYS; | |
1021 | } | |
1022 | } | |
1023 | ||
1024 | /** | |
1025 | * cap_vm_enough_memory - Determine whether a new virtual mapping is permitted | |
1026 | * @mm: The VM space in which the new mapping is to be made | |
1027 | * @pages: The size of the mapping | |
1028 | * | |
1029 | * Determine whether the allocation of a new virtual mapping by the current | |
1030 | * task is permitted, returning 1 if permission is granted, 0 if not. | |
1031 | */ | |
1032 | int cap_vm_enough_memory(struct mm_struct *mm, long pages) | |
1033 | { | |
1034 | int cap_sys_admin = 0; | |
1035 | ||
1036 | if (cap_capable(current_cred(), &init_user_ns, CAP_SYS_ADMIN, | |
1037 | SECURITY_CAP_NOAUDIT) == 0) | |
1038 | cap_sys_admin = 1; | |
1039 | return cap_sys_admin; | |
1040 | } | |
1041 | ||
1042 | /* | |
1043 | * cap_mmap_addr - check if able to map given addr | |
1044 | * @addr: address attempting to be mapped | |
1045 | * | |
1046 | * If the process is attempting to map memory below dac_mmap_min_addr they need | |
1047 | * CAP_SYS_RAWIO. The other parameters to this function are unused by the | |
1048 | * capability security module. Returns 0 if this mapping should be allowed | |
1049 | * -EPERM if not. | |
1050 | */ | |
1051 | int cap_mmap_addr(unsigned long addr) | |
1052 | { | |
1053 | int ret = 0; | |
1054 | ||
1055 | if (addr < dac_mmap_min_addr) { | |
1056 | ret = cap_capable(current_cred(), &init_user_ns, CAP_SYS_RAWIO, | |
1057 | SECURITY_CAP_AUDIT); | |
1058 | /* set PF_SUPERPRIV if it turns out we allow the low mmap */ | |
1059 | if (ret == 0) | |
1060 | current->flags |= PF_SUPERPRIV; | |
1061 | } | |
1062 | return ret; | |
1063 | } | |
1064 | ||
1065 | int cap_mmap_file(struct file *file, unsigned long reqprot, | |
1066 | unsigned long prot, unsigned long flags) | |
1067 | { | |
1068 | return 0; | |
1069 | } | |
1070 | ||
1071 | #ifdef CONFIG_SECURITY | |
1072 | ||
1073 | struct security_hook_list capability_hooks[] = { | |
1074 | LSM_HOOK_INIT(capable, cap_capable), | |
1075 | LSM_HOOK_INIT(settime, cap_settime), | |
1076 | LSM_HOOK_INIT(ptrace_access_check, cap_ptrace_access_check), | |
1077 | LSM_HOOK_INIT(ptrace_traceme, cap_ptrace_traceme), | |
1078 | LSM_HOOK_INIT(capget, cap_capget), | |
1079 | LSM_HOOK_INIT(capset, cap_capset), | |
1080 | LSM_HOOK_INIT(bprm_set_creds, cap_bprm_set_creds), | |
1081 | LSM_HOOK_INIT(bprm_secureexec, cap_bprm_secureexec), | |
1082 | LSM_HOOK_INIT(inode_need_killpriv, cap_inode_need_killpriv), | |
1083 | LSM_HOOK_INIT(inode_killpriv, cap_inode_killpriv), | |
1084 | LSM_HOOK_INIT(mmap_addr, cap_mmap_addr), | |
1085 | LSM_HOOK_INIT(mmap_file, cap_mmap_file), | |
1086 | LSM_HOOK_INIT(task_fix_setuid, cap_task_fix_setuid), | |
1087 | LSM_HOOK_INIT(task_prctl, cap_task_prctl), | |
1088 | LSM_HOOK_INIT(task_setscheduler, cap_task_setscheduler), | |
1089 | LSM_HOOK_INIT(task_setioprio, cap_task_setioprio), | |
1090 | LSM_HOOK_INIT(task_setnice, cap_task_setnice), | |
1091 | LSM_HOOK_INIT(vm_enough_memory, cap_vm_enough_memory), | |
1092 | }; | |
1093 | ||
1094 | void __init capability_add_hooks(void) | |
1095 | { | |
1096 | security_add_hooks(capability_hooks, ARRAY_SIZE(capability_hooks)); | |
1097 | } | |
1098 | ||
1099 | #endif /* CONFIG_SECURITY */ |