Line data Source code
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 : /*
24 : * Leveraged for setting/resetting capabilities
25 : */
26 :
27 : const kernel_cap_t __cap_empty_set = CAP_EMPTY_SET;
28 : EXPORT_SYMBOL(__cap_empty_set);
29 :
30 : int file_caps_enabled = 1;
31 :
32 0 : static int __init file_caps_disable(char *str)
33 : {
34 0 : file_caps_enabled = 0;
35 0 : return 1;
36 : }
37 : __setup("no_file_caps", file_caps_disable);
38 :
39 : #ifdef CONFIG_MULTIUSER
40 : /*
41 : * More recent versions of libcap are available from:
42 : *
43 : * http://www.kernel.org/pub/linux/libs/security/linux-privs/
44 : */
45 :
46 0 : static void warn_legacy_capability_use(void)
47 : {
48 : char name[sizeof(current->comm)];
49 :
50 0 : pr_info_once("warning: `%s' uses 32-bit capabilities (legacy support in use)\n",
51 : get_task_comm(name, current));
52 0 : }
53 :
54 : /*
55 : * Version 2 capabilities worked fine, but the linux/capability.h file
56 : * that accompanied their introduction encouraged their use without
57 : * the necessary user-space source code changes. As such, we have
58 : * created a version 3 with equivalent functionality to version 2, but
59 : * with a header change to protect legacy source code from using
60 : * version 2 when it wanted to use version 1. If your system has code
61 : * that trips the following warning, it is using version 2 specific
62 : * capabilities and may be doing so insecurely.
63 : *
64 : * The remedy is to either upgrade your version of libcap (to 2.10+,
65 : * if the application is linked against it), or recompile your
66 : * application with modern kernel headers and this warning will go
67 : * away.
68 : */
69 :
70 0 : static void warn_deprecated_v2(void)
71 : {
72 : char name[sizeof(current->comm)];
73 :
74 0 : pr_info_once("warning: `%s' uses deprecated v2 capabilities in a way that may be insecure\n",
75 : get_task_comm(name, current));
76 0 : }
77 :
78 : /*
79 : * Version check. Return the number of u32s in each capability flag
80 : * array, or a negative value on error.
81 : */
82 0 : static int cap_validate_magic(cap_user_header_t header, unsigned *tocopy)
83 : {
84 : __u32 version;
85 :
86 0 : if (get_user(version, &header->version))
87 : return -EFAULT;
88 :
89 0 : switch (version) {
90 : case _LINUX_CAPABILITY_VERSION_1:
91 0 : warn_legacy_capability_use();
92 0 : *tocopy = _LINUX_CAPABILITY_U32S_1;
93 0 : break;
94 : case _LINUX_CAPABILITY_VERSION_2:
95 0 : warn_deprecated_v2();
96 : fallthrough; /* v3 is otherwise equivalent to v2 */
97 : case _LINUX_CAPABILITY_VERSION_3:
98 0 : *tocopy = _LINUX_CAPABILITY_U32S_3;
99 0 : break;
100 : default:
101 0 : if (put_user((u32)_KERNEL_CAPABILITY_VERSION, &header->version))
102 : return -EFAULT;
103 0 : return -EINVAL;
104 : }
105 :
106 : return 0;
107 : }
108 :
109 : /*
110 : * The only thing that can change the capabilities of the current
111 : * process is the current process. As such, we can't be in this code
112 : * at the same time as we are in the process of setting capabilities
113 : * in this process. The net result is that we can limit our use of
114 : * locks to when we are reading the caps of another process.
115 : */
116 0 : static inline int cap_get_target_pid(pid_t pid, kernel_cap_t *pEp,
117 : kernel_cap_t *pIp, kernel_cap_t *pPp)
118 : {
119 : int ret;
120 :
121 0 : if (pid && (pid != task_pid_vnr(current))) {
122 : struct task_struct *target;
123 :
124 : rcu_read_lock();
125 :
126 0 : target = find_task_by_vpid(pid);
127 0 : if (!target)
128 : ret = -ESRCH;
129 : else
130 0 : ret = security_capget(target, pEp, pIp, pPp);
131 :
132 : rcu_read_unlock();
133 : } else
134 0 : ret = security_capget(current, pEp, pIp, pPp);
135 :
136 0 : return ret;
137 : }
138 :
139 : /**
140 : * sys_capget - get the capabilities of a given process.
141 : * @header: pointer to struct that contains capability version and
142 : * target pid data
143 : * @dataptr: pointer to struct that contains the effective, permitted,
144 : * and inheritable capabilities that are returned
145 : *
146 : * Returns 0 on success and < 0 on error.
147 : */
148 0 : SYSCALL_DEFINE2(capget, cap_user_header_t, header, cap_user_data_t, dataptr)
149 : {
150 0 : int ret = 0;
151 : pid_t pid;
152 : unsigned tocopy;
153 : kernel_cap_t pE, pI, pP;
154 :
155 0 : ret = cap_validate_magic(header, &tocopy);
156 0 : if ((dataptr == NULL) || (ret != 0))
157 0 : return ((dataptr == NULL) && (ret == -EINVAL)) ? 0 : ret;
158 :
159 0 : if (get_user(pid, &header->pid))
160 : return -EFAULT;
161 :
162 0 : if (pid < 0)
163 : return -EINVAL;
164 :
165 0 : ret = cap_get_target_pid(pid, &pE, &pI, &pP);
166 0 : if (!ret) {
167 : struct __user_cap_data_struct kdata[_KERNEL_CAPABILITY_U32S];
168 : unsigned i;
169 :
170 0 : for (i = 0; i < tocopy; i++) {
171 0 : kdata[i].effective = pE.cap[i];
172 0 : kdata[i].permitted = pP.cap[i];
173 0 : kdata[i].inheritable = pI.cap[i];
174 : }
175 :
176 : /*
177 : * Note, in the case, tocopy < _KERNEL_CAPABILITY_U32S,
178 : * we silently drop the upper capabilities here. This
179 : * has the effect of making older libcap
180 : * implementations implicitly drop upper capability
181 : * bits when they perform a: capget/modify/capset
182 : * sequence.
183 : *
184 : * This behavior is considered fail-safe
185 : * behavior. Upgrading the application to a newer
186 : * version of libcap will enable access to the newer
187 : * capabilities.
188 : *
189 : * An alternative would be to return an error here
190 : * (-ERANGE), but that causes legacy applications to
191 : * unexpectedly fail; the capget/modify/capset aborts
192 : * before modification is attempted and the application
193 : * fails.
194 : */
195 0 : if (copy_to_user(dataptr, kdata, tocopy
196 : * sizeof(struct __user_cap_data_struct))) {
197 0 : return -EFAULT;
198 : }
199 : }
200 :
201 0 : return ret;
202 : }
203 :
204 : /**
205 : * sys_capset - set capabilities for a process or (*) a group of processes
206 : * @header: pointer to struct that contains capability version and
207 : * target pid data
208 : * @data: pointer to struct that contains the effective, permitted,
209 : * and inheritable capabilities
210 : *
211 : * Set capabilities for the current process only. The ability to any other
212 : * process(es) has been deprecated and removed.
213 : *
214 : * The restrictions on setting capabilities are specified as:
215 : *
216 : * I: any raised capabilities must be a subset of the old permitted
217 : * P: any raised capabilities must be a subset of the old permitted
218 : * E: must be set to a subset of new permitted
219 : *
220 : * Returns 0 on success and < 0 on error.
221 : */
222 0 : SYSCALL_DEFINE2(capset, cap_user_header_t, header, const cap_user_data_t, data)
223 : {
224 : struct __user_cap_data_struct kdata[_KERNEL_CAPABILITY_U32S];
225 : unsigned i, tocopy, copybytes;
226 : kernel_cap_t inheritable, permitted, effective;
227 : struct cred *new;
228 : int ret;
229 : pid_t pid;
230 :
231 0 : ret = cap_validate_magic(header, &tocopy);
232 0 : if (ret != 0)
233 0 : return ret;
234 :
235 0 : if (get_user(pid, &header->pid))
236 : return -EFAULT;
237 :
238 : /* may only affect current now */
239 0 : if (pid != 0 && pid != task_pid_vnr(current))
240 : return -EPERM;
241 :
242 0 : copybytes = tocopy * sizeof(struct __user_cap_data_struct);
243 0 : if (copybytes > sizeof(kdata))
244 : return -EFAULT;
245 :
246 0 : if (copy_from_user(&kdata, data, copybytes))
247 : return -EFAULT;
248 :
249 0 : for (i = 0; i < tocopy; i++) {
250 0 : effective.cap[i] = kdata[i].effective;
251 0 : permitted.cap[i] = kdata[i].permitted;
252 0 : inheritable.cap[i] = kdata[i].inheritable;
253 : }
254 0 : while (i < _KERNEL_CAPABILITY_U32S) {
255 0 : effective.cap[i] = 0;
256 0 : permitted.cap[i] = 0;
257 0 : inheritable.cap[i] = 0;
258 0 : i++;
259 : }
260 :
261 0 : effective.cap[CAP_LAST_U32] &= CAP_LAST_U32_VALID_MASK;
262 0 : permitted.cap[CAP_LAST_U32] &= CAP_LAST_U32_VALID_MASK;
263 0 : inheritable.cap[CAP_LAST_U32] &= CAP_LAST_U32_VALID_MASK;
264 :
265 0 : new = prepare_creds();
266 0 : if (!new)
267 : return -ENOMEM;
268 :
269 0 : ret = security_capset(new, current_cred(),
270 : &effective, &inheritable, &permitted);
271 0 : if (ret < 0)
272 : goto error;
273 :
274 0 : audit_log_capset(new, current_cred());
275 :
276 0 : return commit_creds(new);
277 :
278 : error:
279 0 : abort_creds(new);
280 0 : return ret;
281 : }
282 :
283 : /**
284 : * has_ns_capability - Does a task have a capability in a specific user ns
285 : * @t: The task in question
286 : * @ns: target user namespace
287 : * @cap: The capability to be tested for
288 : *
289 : * Return true if the specified task has the given superior capability
290 : * currently in effect to the specified user namespace, false if not.
291 : *
292 : * Note that this does not set PF_SUPERPRIV on the task.
293 : */
294 0 : bool has_ns_capability(struct task_struct *t,
295 : struct user_namespace *ns, int cap)
296 : {
297 : int ret;
298 :
299 : rcu_read_lock();
300 0 : ret = security_capable(__task_cred(t), ns, cap, CAP_OPT_NONE);
301 : rcu_read_unlock();
302 :
303 0 : return (ret == 0);
304 : }
305 :
306 : /**
307 : * has_capability - Does a task have a capability in init_user_ns
308 : * @t: The task in question
309 : * @cap: The capability to be tested for
310 : *
311 : * Return true if the specified task has the given superior capability
312 : * currently in effect to the initial user namespace, false if not.
313 : *
314 : * Note that this does not set PF_SUPERPRIV on the task.
315 : */
316 0 : bool has_capability(struct task_struct *t, int cap)
317 : {
318 0 : return has_ns_capability(t, &init_user_ns, cap);
319 : }
320 : EXPORT_SYMBOL(has_capability);
321 :
322 : /**
323 : * has_ns_capability_noaudit - Does a task have a capability (unaudited)
324 : * in a specific user ns.
325 : * @t: The task in question
326 : * @ns: target user namespace
327 : * @cap: The capability to be tested for
328 : *
329 : * Return true if the specified task has the given superior capability
330 : * currently in effect to the specified user namespace, false if not.
331 : * Do not write an audit message for the check.
332 : *
333 : * Note that this does not set PF_SUPERPRIV on the task.
334 : */
335 0 : bool has_ns_capability_noaudit(struct task_struct *t,
336 : struct user_namespace *ns, int cap)
337 : {
338 : int ret;
339 :
340 : rcu_read_lock();
341 0 : ret = security_capable(__task_cred(t), ns, cap, CAP_OPT_NOAUDIT);
342 : rcu_read_unlock();
343 :
344 0 : return (ret == 0);
345 : }
346 :
347 : /**
348 : * has_capability_noaudit - Does a task have a capability (unaudited) in the
349 : * initial user ns
350 : * @t: The task in question
351 : * @cap: The capability to be tested for
352 : *
353 : * Return true if the specified task has the given superior capability
354 : * currently in effect to init_user_ns, false if not. Don't write an
355 : * audit message for the check.
356 : *
357 : * Note that this does not set PF_SUPERPRIV on the task.
358 : */
359 0 : bool has_capability_noaudit(struct task_struct *t, int cap)
360 : {
361 0 : return has_ns_capability_noaudit(t, &init_user_ns, cap);
362 : }
363 : EXPORT_SYMBOL(has_capability_noaudit);
364 :
365 1 : static bool ns_capable_common(struct user_namespace *ns,
366 : int cap,
367 : unsigned int opts)
368 : {
369 : int capable;
370 :
371 1 : if (unlikely(!cap_valid(cap))) {
372 0 : pr_crit("capable() called with invalid cap=%u\n", cap);
373 0 : BUG();
374 : }
375 :
376 2 : capable = security_capable(current_cred(), ns, cap, opts);
377 1 : if (capable == 0) {
378 1 : current->flags |= PF_SUPERPRIV;
379 1 : return true;
380 : }
381 : return false;
382 : }
383 :
384 : /**
385 : * ns_capable - Determine if the current task has a superior capability in effect
386 : * @ns: The usernamespace we want the capability in
387 : * @cap: The capability to be tested for
388 : *
389 : * Return true if the current task has the given superior capability currently
390 : * available for use, false if not.
391 : *
392 : * This sets PF_SUPERPRIV on the task if the capability is available on the
393 : * assumption that it's about to be used.
394 : */
395 0 : bool ns_capable(struct user_namespace *ns, int cap)
396 : {
397 1 : return ns_capable_common(ns, cap, CAP_OPT_NONE);
398 : }
399 : EXPORT_SYMBOL(ns_capable);
400 :
401 : /**
402 : * ns_capable_noaudit - Determine if the current task has a superior capability
403 : * (unaudited) in effect
404 : * @ns: The usernamespace we want the capability in
405 : * @cap: The capability to be tested for
406 : *
407 : * Return true if the current task has the given superior capability currently
408 : * available for use, false if not.
409 : *
410 : * This sets PF_SUPERPRIV on the task if the capability is available on the
411 : * assumption that it's about to be used.
412 : */
413 0 : bool ns_capable_noaudit(struct user_namespace *ns, int cap)
414 : {
415 0 : return ns_capable_common(ns, cap, CAP_OPT_NOAUDIT);
416 : }
417 : EXPORT_SYMBOL(ns_capable_noaudit);
418 :
419 : /**
420 : * ns_capable_setid - Determine if the current task has a superior capability
421 : * in effect, while signalling that this check is being done from within a
422 : * setid or setgroups syscall.
423 : * @ns: The usernamespace we want the capability in
424 : * @cap: The capability to be tested for
425 : *
426 : * Return true if the current task has the given superior capability currently
427 : * available for use, false if not.
428 : *
429 : * This sets PF_SUPERPRIV on the task if the capability is available on the
430 : * assumption that it's about to be used.
431 : */
432 0 : bool ns_capable_setid(struct user_namespace *ns, int cap)
433 : {
434 0 : return ns_capable_common(ns, cap, CAP_OPT_INSETID);
435 : }
436 : EXPORT_SYMBOL(ns_capable_setid);
437 :
438 : /**
439 : * capable - Determine if the current task has a superior capability in effect
440 : * @cap: The capability to be tested for
441 : *
442 : * Return true if the current task has the given superior capability currently
443 : * available for use, false if not.
444 : *
445 : * This sets PF_SUPERPRIV on the task if the capability is available on the
446 : * assumption that it's about to be used.
447 : */
448 1 : bool capable(int cap)
449 : {
450 1 : return ns_capable(&init_user_ns, cap);
451 : }
452 : EXPORT_SYMBOL(capable);
453 : #endif /* CONFIG_MULTIUSER */
454 :
455 : /**
456 : * file_ns_capable - Determine if the file's opener had a capability in effect
457 : * @file: The file we want to check
458 : * @ns: The usernamespace we want the capability in
459 : * @cap: The capability to be tested for
460 : *
461 : * Return true if task that opened the file had a capability in effect
462 : * when the file was opened.
463 : *
464 : * This does not set PF_SUPERPRIV because the caller may not
465 : * actually be privileged.
466 : */
467 0 : bool file_ns_capable(const struct file *file, struct user_namespace *ns,
468 : int cap)
469 : {
470 :
471 0 : if (WARN_ON_ONCE(!cap_valid(cap)))
472 : return false;
473 :
474 0 : if (security_capable(file->f_cred, ns, cap, CAP_OPT_NONE) == 0)
475 : return true;
476 :
477 0 : return false;
478 : }
479 : EXPORT_SYMBOL(file_ns_capable);
480 :
481 : /**
482 : * privileged_wrt_inode_uidgid - Do capabilities in the namespace work over the inode?
483 : * @ns: The user namespace in question
484 : * @inode: The inode in question
485 : *
486 : * Return true if the inode uid and gid are within the namespace.
487 : */
488 0 : bool privileged_wrt_inode_uidgid(struct user_namespace *ns,
489 : struct user_namespace *mnt_userns,
490 : const struct inode *inode)
491 : {
492 0 : return kuid_has_mapping(ns, i_uid_into_mnt(mnt_userns, inode)) &&
493 0 : kgid_has_mapping(ns, i_gid_into_mnt(mnt_userns, inode));
494 : }
495 :
496 : /**
497 : * capable_wrt_inode_uidgid - Check nsown_capable and uid and gid mapped
498 : * @inode: The inode in question
499 : * @cap: The capability in question
500 : *
501 : * Return true if the current task has the given capability targeted at
502 : * its own user namespace and that the given inode's uid and gid are
503 : * mapped into the current user namespace.
504 : */
505 0 : bool capable_wrt_inode_uidgid(struct user_namespace *mnt_userns,
506 : const struct inode *inode, int cap)
507 : {
508 0 : struct user_namespace *ns = current_user_ns();
509 :
510 0 : return ns_capable(ns, cap) &&
511 0 : privileged_wrt_inode_uidgid(ns, mnt_userns, inode);
512 : }
513 : EXPORT_SYMBOL(capable_wrt_inode_uidgid);
514 :
515 : /**
516 : * ptracer_capable - Determine if the ptracer holds CAP_SYS_PTRACE in the namespace
517 : * @tsk: The task that may be ptraced
518 : * @ns: The user namespace to search for CAP_SYS_PTRACE in
519 : *
520 : * Return true if the task that is ptracing the current task had CAP_SYS_PTRACE
521 : * in the specified user namespace.
522 : */
523 0 : bool ptracer_capable(struct task_struct *tsk, struct user_namespace *ns)
524 : {
525 0 : int ret = 0; /* An absent tracer adds no restrictions */
526 : const struct cred *cred;
527 :
528 : rcu_read_lock();
529 0 : cred = rcu_dereference(tsk->ptracer_cred);
530 0 : if (cred)
531 0 : ret = security_capable(cred, ns, CAP_SYS_PTRACE,
532 : CAP_OPT_NOAUDIT);
533 : rcu_read_unlock();
534 0 : return (ret == 0);
535 : }
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