1 | // SPDX-License-Identifier: GPL-2.0 |
2 | /* |
3 | * linux/kernel/capability.c |
4 | * |
5 | * Copyright (C) 1997 Andrew Main <zefram@fysh.org> |
6 | * |
7 | * Integrated into 2.1.97+, Andrew G. Morgan <morgan@kernel.org> |
8 | * 30 May 2002: Cleanup, Robert M. Love <rml@tech9.net> |
9 | */ |
10 | |
11 | #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
12 | |
13 | #include <linux/audit.h> |
14 | #include <linux/capability.h> |
15 | #include <linux/mm.h> |
16 | #include <linux/export.h> |
17 | #include <linux/security.h> |
18 | #include <linux/syscalls.h> |
19 | #include <linux/pid_namespace.h> |
20 | #include <linux/user_namespace.h> |
21 | #include <linux/uaccess.h> |
22 | |
23 | int file_caps_enabled = 1; |
24 | |
25 | static int __init file_caps_disable(char *str) |
26 | { |
27 | file_caps_enabled = 0; |
28 | return 1; |
29 | } |
30 | __setup("no_file_caps" , file_caps_disable); |
31 | |
32 | #ifdef CONFIG_MULTIUSER |
33 | /* |
34 | * More recent versions of libcap are available from: |
35 | * |
36 | * http://www.kernel.org/pub/linux/libs/security/linux-privs/ |
37 | */ |
38 | |
39 | static void warn_legacy_capability_use(void) |
40 | { |
41 | char name[sizeof(current->comm)]; |
42 | |
43 | pr_info_once("warning: `%s' uses 32-bit capabilities (legacy support in use)\n" , |
44 | get_task_comm(name, current)); |
45 | } |
46 | |
47 | /* |
48 | * Version 2 capabilities worked fine, but the linux/capability.h file |
49 | * that accompanied their introduction encouraged their use without |
50 | * the necessary user-space source code changes. As such, we have |
51 | * created a version 3 with equivalent functionality to version 2, but |
52 | * with a header change to protect legacy source code from using |
53 | * version 2 when it wanted to use version 1. If your system has code |
54 | * that trips the following warning, it is using version 2 specific |
55 | * capabilities and may be doing so insecurely. |
56 | * |
57 | * The remedy is to either upgrade your version of libcap (to 2.10+, |
58 | * if the application is linked against it), or recompile your |
59 | * application with modern kernel headers and this warning will go |
60 | * away. |
61 | */ |
62 | |
63 | static void warn_deprecated_v2(void) |
64 | { |
65 | char name[sizeof(current->comm)]; |
66 | |
67 | pr_info_once("warning: `%s' uses deprecated v2 capabilities in a way that may be insecure\n" , |
68 | get_task_comm(name, current)); |
69 | } |
70 | |
71 | /* |
72 | * Version check. Return the number of u32s in each capability flag |
73 | * array, or a negative value on error. |
74 | */ |
75 | static int cap_validate_magic(cap_user_header_t , unsigned *tocopy) |
76 | { |
77 | __u32 version; |
78 | |
79 | if (get_user(version, &header->version)) |
80 | return -EFAULT; |
81 | |
82 | switch (version) { |
83 | case _LINUX_CAPABILITY_VERSION_1: |
84 | warn_legacy_capability_use(); |
85 | *tocopy = _LINUX_CAPABILITY_U32S_1; |
86 | break; |
87 | case _LINUX_CAPABILITY_VERSION_2: |
88 | warn_deprecated_v2(); |
89 | fallthrough; /* v3 is otherwise equivalent to v2 */ |
90 | case _LINUX_CAPABILITY_VERSION_3: |
91 | *tocopy = _LINUX_CAPABILITY_U32S_3; |
92 | break; |
93 | default: |
94 | if (put_user((u32)_KERNEL_CAPABILITY_VERSION, &header->version)) |
95 | return -EFAULT; |
96 | return -EINVAL; |
97 | } |
98 | |
99 | return 0; |
100 | } |
101 | |
102 | /* |
103 | * The only thing that can change the capabilities of the current |
104 | * process is the current process. As such, we can't be in this code |
105 | * at the same time as we are in the process of setting capabilities |
106 | * in this process. The net result is that we can limit our use of |
107 | * locks to when we are reading the caps of another process. |
108 | */ |
109 | static inline int cap_get_target_pid(pid_t pid, kernel_cap_t *pEp, |
110 | kernel_cap_t *pIp, kernel_cap_t *pPp) |
111 | { |
112 | int ret; |
113 | |
114 | if (pid && (pid != task_pid_vnr(current))) { |
115 | const struct task_struct *target; |
116 | |
117 | rcu_read_lock(); |
118 | |
119 | target = find_task_by_vpid(nr: pid); |
120 | if (!target) |
121 | ret = -ESRCH; |
122 | else |
123 | ret = security_capget(target, effective: pEp, inheritable: pIp, permitted: pPp); |
124 | |
125 | rcu_read_unlock(); |
126 | } else |
127 | ret = security_capget(current, effective: pEp, inheritable: pIp, permitted: pPp); |
128 | |
129 | return ret; |
130 | } |
131 | |
132 | /** |
133 | * sys_capget - get the capabilities of a given process. |
134 | * @header: pointer to struct that contains capability version and |
135 | * target pid data |
136 | * @dataptr: pointer to struct that contains the effective, permitted, |
137 | * and inheritable capabilities that are returned |
138 | * |
139 | * Returns 0 on success and < 0 on error. |
140 | */ |
141 | SYSCALL_DEFINE2(capget, cap_user_header_t, , cap_user_data_t, dataptr) |
142 | { |
143 | int ret = 0; |
144 | pid_t pid; |
145 | unsigned tocopy; |
146 | kernel_cap_t pE, pI, pP; |
147 | struct __user_cap_data_struct kdata[2]; |
148 | |
149 | ret = cap_validate_magic(header, tocopy: &tocopy); |
150 | if ((dataptr == NULL) || (ret != 0)) |
151 | return ((dataptr == NULL) && (ret == -EINVAL)) ? 0 : ret; |
152 | |
153 | if (get_user(pid, &header->pid)) |
154 | return -EFAULT; |
155 | |
156 | if (pid < 0) |
157 | return -EINVAL; |
158 | |
159 | ret = cap_get_target_pid(pid, pEp: &pE, pIp: &pI, pPp: &pP); |
160 | if (ret) |
161 | return ret; |
162 | |
163 | /* |
164 | * Annoying legacy format with 64-bit capabilities exposed |
165 | * as two sets of 32-bit fields, so we need to split the |
166 | * capability values up. |
167 | */ |
168 | kdata[0].effective = pE.val; kdata[1].effective = pE.val >> 32; |
169 | kdata[0].permitted = pP.val; kdata[1].permitted = pP.val >> 32; |
170 | kdata[0].inheritable = pI.val; kdata[1].inheritable = pI.val >> 32; |
171 | |
172 | /* |
173 | * Note, in the case, tocopy < _KERNEL_CAPABILITY_U32S, |
174 | * we silently drop the upper capabilities here. This |
175 | * has the effect of making older libcap |
176 | * implementations implicitly drop upper capability |
177 | * bits when they perform a: capget/modify/capset |
178 | * sequence. |
179 | * |
180 | * This behavior is considered fail-safe |
181 | * behavior. Upgrading the application to a newer |
182 | * version of libcap will enable access to the newer |
183 | * capabilities. |
184 | * |
185 | * An alternative would be to return an error here |
186 | * (-ERANGE), but that causes legacy applications to |
187 | * unexpectedly fail; the capget/modify/capset aborts |
188 | * before modification is attempted and the application |
189 | * fails. |
190 | */ |
191 | if (copy_to_user(to: dataptr, from: kdata, n: tocopy * sizeof(kdata[0]))) |
192 | return -EFAULT; |
193 | |
194 | return 0; |
195 | } |
196 | |
197 | static kernel_cap_t mk_kernel_cap(u32 low, u32 high) |
198 | { |
199 | return (kernel_cap_t) { (low | ((u64)high << 32)) & CAP_VALID_MASK }; |
200 | } |
201 | |
202 | /** |
203 | * sys_capset - set capabilities for a process or (*) a group of processes |
204 | * @header: pointer to struct that contains capability version and |
205 | * target pid data |
206 | * @data: pointer to struct that contains the effective, permitted, |
207 | * and inheritable capabilities |
208 | * |
209 | * Set capabilities for the current process only. The ability to any other |
210 | * process(es) has been deprecated and removed. |
211 | * |
212 | * The restrictions on setting capabilities are specified as: |
213 | * |
214 | * I: any raised capabilities must be a subset of the old permitted |
215 | * P: any raised capabilities must be a subset of the old permitted |
216 | * E: must be set to a subset of new permitted |
217 | * |
218 | * Returns 0 on success and < 0 on error. |
219 | */ |
220 | SYSCALL_DEFINE2(capset, cap_user_header_t, , const cap_user_data_t, data) |
221 | { |
222 | struct __user_cap_data_struct kdata[2] = { { 0, }, }; |
223 | unsigned tocopy, copybytes; |
224 | kernel_cap_t inheritable, permitted, effective; |
225 | struct cred *new; |
226 | int ret; |
227 | pid_t pid; |
228 | |
229 | ret = cap_validate_magic(header, tocopy: &tocopy); |
230 | if (ret != 0) |
231 | return ret; |
232 | |
233 | if (get_user(pid, &header->pid)) |
234 | return -EFAULT; |
235 | |
236 | /* may only affect current now */ |
237 | if (pid != 0 && pid != task_pid_vnr(current)) |
238 | return -EPERM; |
239 | |
240 | copybytes = tocopy * sizeof(struct __user_cap_data_struct); |
241 | if (copybytes > sizeof(kdata)) |
242 | return -EFAULT; |
243 | |
244 | if (copy_from_user(to: &kdata, from: data, n: copybytes)) |
245 | return -EFAULT; |
246 | |
247 | effective = mk_kernel_cap(low: kdata[0].effective, high: kdata[1].effective); |
248 | permitted = mk_kernel_cap(low: kdata[0].permitted, high: kdata[1].permitted); |
249 | inheritable = mk_kernel_cap(low: kdata[0].inheritable, high: kdata[1].inheritable); |
250 | |
251 | new = prepare_creds(); |
252 | if (!new) |
253 | return -ENOMEM; |
254 | |
255 | ret = security_capset(new, current_cred(), |
256 | effective: &effective, inheritable: &inheritable, permitted: &permitted); |
257 | if (ret < 0) |
258 | goto error; |
259 | |
260 | audit_log_capset(new, current_cred()); |
261 | |
262 | return commit_creds(new); |
263 | |
264 | error: |
265 | abort_creds(new); |
266 | return ret; |
267 | } |
268 | |
269 | /** |
270 | * has_ns_capability - Does a task have a capability in a specific user ns |
271 | * @t: The task in question |
272 | * @ns: target user namespace |
273 | * @cap: The capability to be tested for |
274 | * |
275 | * Return true if the specified task has the given superior capability |
276 | * currently in effect to the specified user namespace, false if not. |
277 | * |
278 | * Note that this does not set PF_SUPERPRIV on the task. |
279 | */ |
280 | bool has_ns_capability(struct task_struct *t, |
281 | struct user_namespace *ns, int cap) |
282 | { |
283 | int ret; |
284 | |
285 | rcu_read_lock(); |
286 | ret = security_capable(__task_cred(t), ns, cap, CAP_OPT_NONE); |
287 | rcu_read_unlock(); |
288 | |
289 | return (ret == 0); |
290 | } |
291 | |
292 | /** |
293 | * has_capability - Does a task have a capability in init_user_ns |
294 | * @t: The task in question |
295 | * @cap: The capability to be tested for |
296 | * |
297 | * Return true if the specified task has the given superior capability |
298 | * currently in effect to the initial user namespace, false if not. |
299 | * |
300 | * Note that this does not set PF_SUPERPRIV on the task. |
301 | */ |
302 | bool has_capability(struct task_struct *t, int cap) |
303 | { |
304 | return has_ns_capability(t, ns: &init_user_ns, cap); |
305 | } |
306 | EXPORT_SYMBOL(has_capability); |
307 | |
308 | /** |
309 | * has_ns_capability_noaudit - Does a task have a capability (unaudited) |
310 | * in a specific user ns. |
311 | * @t: The task in question |
312 | * @ns: target user namespace |
313 | * @cap: The capability to be tested for |
314 | * |
315 | * Return true if the specified task has the given superior capability |
316 | * currently in effect to the specified user namespace, false if not. |
317 | * Do not write an audit message for the check. |
318 | * |
319 | * Note that this does not set PF_SUPERPRIV on the task. |
320 | */ |
321 | bool has_ns_capability_noaudit(struct task_struct *t, |
322 | struct user_namespace *ns, int cap) |
323 | { |
324 | int ret; |
325 | |
326 | rcu_read_lock(); |
327 | ret = security_capable(__task_cred(t), ns, cap, CAP_OPT_NOAUDIT); |
328 | rcu_read_unlock(); |
329 | |
330 | return (ret == 0); |
331 | } |
332 | |
333 | /** |
334 | * has_capability_noaudit - Does a task have a capability (unaudited) in the |
335 | * initial user ns |
336 | * @t: The task in question |
337 | * @cap: The capability to be tested for |
338 | * |
339 | * Return true if the specified task has the given superior capability |
340 | * currently in effect to init_user_ns, false if not. Don't write an |
341 | * audit message for the check. |
342 | * |
343 | * Note that this does not set PF_SUPERPRIV on the task. |
344 | */ |
345 | bool has_capability_noaudit(struct task_struct *t, int cap) |
346 | { |
347 | return has_ns_capability_noaudit(t, ns: &init_user_ns, cap); |
348 | } |
349 | EXPORT_SYMBOL(has_capability_noaudit); |
350 | |
351 | static bool ns_capable_common(struct user_namespace *ns, |
352 | int cap, |
353 | unsigned int opts) |
354 | { |
355 | int capable; |
356 | |
357 | if (unlikely(!cap_valid(cap))) { |
358 | pr_crit("capable() called with invalid cap=%u\n" , cap); |
359 | BUG(); |
360 | } |
361 | |
362 | capable = security_capable(current_cred(), ns, cap, opts); |
363 | if (capable == 0) { |
364 | current->flags |= PF_SUPERPRIV; |
365 | return true; |
366 | } |
367 | return false; |
368 | } |
369 | |
370 | /** |
371 | * ns_capable - Determine if the current task has a superior capability in effect |
372 | * @ns: The usernamespace we want the capability in |
373 | * @cap: The capability to be tested for |
374 | * |
375 | * Return true if the current task has the given superior capability currently |
376 | * available for use, false if not. |
377 | * |
378 | * This sets PF_SUPERPRIV on the task if the capability is available on the |
379 | * assumption that it's about to be used. |
380 | */ |
381 | bool ns_capable(struct user_namespace *ns, int cap) |
382 | { |
383 | return ns_capable_common(ns, cap, CAP_OPT_NONE); |
384 | } |
385 | EXPORT_SYMBOL(ns_capable); |
386 | |
387 | /** |
388 | * ns_capable_noaudit - Determine if the current task has a superior capability |
389 | * (unaudited) in effect |
390 | * @ns: The usernamespace we want the capability in |
391 | * @cap: The capability to be tested for |
392 | * |
393 | * Return true if the current task has the given superior capability currently |
394 | * available for use, false if not. |
395 | * |
396 | * This sets PF_SUPERPRIV on the task if the capability is available on the |
397 | * assumption that it's about to be used. |
398 | */ |
399 | bool ns_capable_noaudit(struct user_namespace *ns, int cap) |
400 | { |
401 | return ns_capable_common(ns, cap, CAP_OPT_NOAUDIT); |
402 | } |
403 | EXPORT_SYMBOL(ns_capable_noaudit); |
404 | |
405 | /** |
406 | * ns_capable_setid - Determine if the current task has a superior capability |
407 | * in effect, while signalling that this check is being done from within a |
408 | * setid or setgroups syscall. |
409 | * @ns: The usernamespace we want the capability in |
410 | * @cap: The capability to be tested for |
411 | * |
412 | * Return true if the current task has the given superior capability currently |
413 | * available for use, false if not. |
414 | * |
415 | * This sets PF_SUPERPRIV on the task if the capability is available on the |
416 | * assumption that it's about to be used. |
417 | */ |
418 | bool ns_capable_setid(struct user_namespace *ns, int cap) |
419 | { |
420 | return ns_capable_common(ns, cap, CAP_OPT_INSETID); |
421 | } |
422 | EXPORT_SYMBOL(ns_capable_setid); |
423 | |
424 | /** |
425 | * capable - Determine if the current task has a superior capability in effect |
426 | * @cap: The capability to be tested for |
427 | * |
428 | * Return true if the current task has the given superior capability currently |
429 | * available for use, false if not. |
430 | * |
431 | * This sets PF_SUPERPRIV on the task if the capability is available on the |
432 | * assumption that it's about to be used. |
433 | */ |
434 | bool capable(int cap) |
435 | { |
436 | return ns_capable(&init_user_ns, cap); |
437 | } |
438 | EXPORT_SYMBOL(capable); |
439 | #endif /* CONFIG_MULTIUSER */ |
440 | |
441 | /** |
442 | * file_ns_capable - Determine if the file's opener had a capability in effect |
443 | * @file: The file we want to check |
444 | * @ns: The usernamespace we want the capability in |
445 | * @cap: The capability to be tested for |
446 | * |
447 | * Return true if task that opened the file had a capability in effect |
448 | * when the file was opened. |
449 | * |
450 | * This does not set PF_SUPERPRIV because the caller may not |
451 | * actually be privileged. |
452 | */ |
453 | bool file_ns_capable(const struct file *file, struct user_namespace *ns, |
454 | int cap) |
455 | { |
456 | |
457 | if (WARN_ON_ONCE(!cap_valid(cap))) |
458 | return false; |
459 | |
460 | if (security_capable(cred: file->f_cred, ns, cap, CAP_OPT_NONE) == 0) |
461 | return true; |
462 | |
463 | return false; |
464 | } |
465 | EXPORT_SYMBOL(file_ns_capable); |
466 | |
467 | /** |
468 | * privileged_wrt_inode_uidgid - Do capabilities in the namespace work over the inode? |
469 | * @ns: The user namespace in question |
470 | * @idmap: idmap of the mount @inode was found from |
471 | * @inode: The inode in question |
472 | * |
473 | * Return true if the inode uid and gid are within the namespace. |
474 | */ |
475 | bool privileged_wrt_inode_uidgid(struct user_namespace *ns, |
476 | struct mnt_idmap *idmap, |
477 | const struct inode *inode) |
478 | { |
479 | return vfsuid_has_mapping(userns: ns, vfsuid: i_uid_into_vfsuid(idmap, inode)) && |
480 | vfsgid_has_mapping(userns: ns, vfsgid: i_gid_into_vfsgid(idmap, inode)); |
481 | } |
482 | |
483 | /** |
484 | * capable_wrt_inode_uidgid - Check nsown_capable and uid and gid mapped |
485 | * @idmap: idmap of the mount @inode was found from |
486 | * @inode: The inode in question |
487 | * @cap: The capability in question |
488 | * |
489 | * Return true if the current task has the given capability targeted at |
490 | * its own user namespace and that the given inode's uid and gid are |
491 | * mapped into the current user namespace. |
492 | */ |
493 | bool capable_wrt_inode_uidgid(struct mnt_idmap *idmap, |
494 | const struct inode *inode, int cap) |
495 | { |
496 | struct user_namespace *ns = current_user_ns(); |
497 | |
498 | return ns_capable(ns, cap) && |
499 | privileged_wrt_inode_uidgid(ns, idmap, inode); |
500 | } |
501 | EXPORT_SYMBOL(capable_wrt_inode_uidgid); |
502 | |
503 | /** |
504 | * ptracer_capable - Determine if the ptracer holds CAP_SYS_PTRACE in the namespace |
505 | * @tsk: The task that may be ptraced |
506 | * @ns: The user namespace to search for CAP_SYS_PTRACE in |
507 | * |
508 | * Return true if the task that is ptracing the current task had CAP_SYS_PTRACE |
509 | * in the specified user namespace. |
510 | */ |
511 | bool ptracer_capable(struct task_struct *tsk, struct user_namespace *ns) |
512 | { |
513 | int ret = 0; /* An absent tracer adds no restrictions */ |
514 | const struct cred *cred; |
515 | |
516 | rcu_read_lock(); |
517 | cred = rcu_dereference(tsk->ptracer_cred); |
518 | if (cred) |
519 | ret = security_capable(cred, ns, CAP_SYS_PTRACE, |
520 | CAP_OPT_NOAUDIT); |
521 | rcu_read_unlock(); |
522 | return (ret == 0); |
523 | } |
524 | |