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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 : 3 : static int cap_validate_magic(cap_user_header_t header, unsigned *tocopy)
83 : : {
84 : : __u32 version;
85 : :
86 : 3 : if (get_user(version, &header->version))
87 : : return -EFAULT;
88 : :
89 : 3 : 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 : : /* fall through - v3 is otherwise equivalent to v2. */
97 : : case _LINUX_CAPABILITY_VERSION_3:
98 : 3 : *tocopy = _LINUX_CAPABILITY_U32S_3;
99 : 3 : break;
100 : : default:
101 : 3 : if (put_user((u32)_KERNEL_CAPABILITY_VERSION, &header->version))
102 : : return -EFAULT;
103 : 3 : 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 : 3 : 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 : 3 : 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 : 3 : ret = security_capget(current, pEp, pIp, pPp);
135 : :
136 : 3 : 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 : 3 : SYSCALL_DEFINE2(capget, cap_user_header_t, header, cap_user_data_t, dataptr)
149 : : {
150 : : int ret = 0;
151 : : pid_t pid;
152 : : unsigned tocopy;
153 : : kernel_cap_t pE, pI, pP;
154 : :
155 : 3 : ret = cap_validate_magic(header, &tocopy);
156 : 3 : if ((dataptr == NULL) || (ret != 0))
157 : 3 : return ((dataptr == NULL) && (ret == -EINVAL)) ? 0 : ret;
158 : :
159 : 3 : if (get_user(pid, &header->pid))
160 : : return -EFAULT;
161 : :
162 : 3 : if (pid < 0)
163 : : return -EINVAL;
164 : :
165 : 3 : ret = cap_get_target_pid(pid, &pE, &pI, &pP);
166 : 3 : if (!ret) {
167 : : struct __user_cap_data_struct kdata[_KERNEL_CAPABILITY_U32S];
168 : : unsigned i;
169 : :
170 : 3 : for (i = 0; i < tocopy; i++) {
171 : 3 : kdata[i].effective = pE.cap[i];
172 : 3 : kdata[i].permitted = pP.cap[i];
173 : 3 : 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 : 3 : if (copy_to_user(dataptr, kdata, tocopy
196 : 3 : * sizeof(struct __user_cap_data_struct))) {
197 : 0 : return -EFAULT;
198 : : }
199 : : }
200 : :
201 : 3 : 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 : 3 : 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 : 3 : ret = cap_validate_magic(header, &tocopy);
232 : 3 : if (ret != 0)
233 : : return ret;
234 : :
235 : 3 : if (get_user(pid, &header->pid))
236 : : return -EFAULT;
237 : :
238 : : /* may only affect current now */
239 : 3 : if (pid != 0 && pid != task_pid_vnr(current))
240 : : return -EPERM;
241 : :
242 : 3 : copybytes = tocopy * sizeof(struct __user_cap_data_struct);
243 : 3 : if (copybytes > sizeof(kdata))
244 : : return -EFAULT;
245 : :
246 : 3 : if (copy_from_user(&kdata, data, copybytes))
247 : : return -EFAULT;
248 : :
249 : 3 : for (i = 0; i < tocopy; i++) {
250 : 3 : effective.cap[i] = kdata[i].effective;
251 : 3 : permitted.cap[i] = kdata[i].permitted;
252 : 3 : inheritable.cap[i] = kdata[i].inheritable;
253 : : }
254 : 3 : 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 : 3 : effective.cap[CAP_LAST_U32] &= CAP_LAST_U32_VALID_MASK;
262 : 3 : permitted.cap[CAP_LAST_U32] &= CAP_LAST_U32_VALID_MASK;
263 : 3 : inheritable.cap[CAP_LAST_U32] &= CAP_LAST_U32_VALID_MASK;
264 : :
265 : 3 : new = prepare_creds();
266 : 3 : if (!new)
267 : : return -ENOMEM;
268 : :
269 : 3 : ret = security_capset(new, current_cred(),
270 : : &effective, &inheritable, &permitted);
271 : 3 : if (ret < 0)
272 : : goto error;
273 : :
274 : 3 : audit_log_capset(new, current_cred());
275 : :
276 : 3 : 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 : 3 : 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 : 3 : ret = security_capable(__task_cred(t), ns, cap, CAP_OPT_NOAUDIT);
342 : : rcu_read_unlock();
343 : :
344 : 3 : 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 : 3 : bool has_capability_noaudit(struct task_struct *t, int cap)
360 : : {
361 : 3 : return has_ns_capability_noaudit(t, &init_user_ns, cap);
362 : : }
363 : :
364 : 3 : static bool ns_capable_common(struct user_namespace *ns,
365 : : int cap,
366 : : unsigned int opts)
367 : : {
368 : : int capable;
369 : :
370 : 3 : if (unlikely(!cap_valid(cap))) {
371 : 0 : pr_crit("capable() called with invalid cap=%u\n", cap);
372 : 0 : BUG();
373 : : }
374 : :
375 : 3 : capable = security_capable(current_cred(), ns, cap, opts);
376 : 3 : if (capable == 0) {
377 : 3 : current->flags |= PF_SUPERPRIV;
378 : 3 : return true;
379 : : }
380 : : return false;
381 : : }
382 : :
383 : : /**
384 : : * ns_capable - Determine if the current task has a superior capability in effect
385 : : * @ns: The usernamespace we want the capability in
386 : : * @cap: The capability to be tested for
387 : : *
388 : : * Return true if the current task has the given superior capability currently
389 : : * available for use, false if not.
390 : : *
391 : : * This sets PF_SUPERPRIV on the task if the capability is available on the
392 : : * assumption that it's about to be used.
393 : : */
394 : 3 : bool ns_capable(struct user_namespace *ns, int cap)
395 : : {
396 : 3 : return ns_capable_common(ns, cap, CAP_OPT_NONE);
397 : : }
398 : : EXPORT_SYMBOL(ns_capable);
399 : :
400 : : /**
401 : : * ns_capable_noaudit - Determine if the current task has a superior capability
402 : : * (unaudited) in effect
403 : : * @ns: The usernamespace we want the capability in
404 : : * @cap: The capability to be tested for
405 : : *
406 : : * Return true if the current task has the given superior capability currently
407 : : * available for use, false if not.
408 : : *
409 : : * This sets PF_SUPERPRIV on the task if the capability is available on the
410 : : * assumption that it's about to be used.
411 : : */
412 : 3 : bool ns_capable_noaudit(struct user_namespace *ns, int cap)
413 : : {
414 : 3 : return ns_capable_common(ns, cap, CAP_OPT_NOAUDIT);
415 : : }
416 : : EXPORT_SYMBOL(ns_capable_noaudit);
417 : :
418 : : /**
419 : : * ns_capable_setid - Determine if the current task has a superior capability
420 : : * in effect, while signalling that this check is being done from within a
421 : : * setid syscall.
422 : : * @ns: The usernamespace we want the capability in
423 : : * @cap: The capability to be tested for
424 : : *
425 : : * Return true if the current task has the given superior capability currently
426 : : * available for use, false if not.
427 : : *
428 : : * This sets PF_SUPERPRIV on the task if the capability is available on the
429 : : * assumption that it's about to be used.
430 : : */
431 : 3 : bool ns_capable_setid(struct user_namespace *ns, int cap)
432 : : {
433 : 3 : return ns_capable_common(ns, cap, CAP_OPT_INSETID);
434 : : }
435 : : EXPORT_SYMBOL(ns_capable_setid);
436 : :
437 : : /**
438 : : * capable - Determine if the current task has a superior capability in effect
439 : : * @cap: The capability to be tested for
440 : : *
441 : : * Return true if the current task has the given superior capability currently
442 : : * available for use, false if not.
443 : : *
444 : : * This sets PF_SUPERPRIV on the task if the capability is available on the
445 : : * assumption that it's about to be used.
446 : : */
447 : 3 : bool capable(int cap)
448 : : {
449 : 3 : return ns_capable(&init_user_ns, cap);
450 : : }
451 : : EXPORT_SYMBOL(capable);
452 : : #endif /* CONFIG_MULTIUSER */
453 : :
454 : : /**
455 : : * file_ns_capable - Determine if the file's opener had a capability in effect
456 : : * @file: The file we want to check
457 : : * @ns: The usernamespace we want the capability in
458 : : * @cap: The capability to be tested for
459 : : *
460 : : * Return true if task that opened the file had a capability in effect
461 : : * when the file was opened.
462 : : *
463 : : * This does not set PF_SUPERPRIV because the caller may not
464 : : * actually be privileged.
465 : : */
466 : 3 : bool file_ns_capable(const struct file *file, struct user_namespace *ns,
467 : : int cap)
468 : : {
469 : :
470 : 3 : if (WARN_ON_ONCE(!cap_valid(cap)))
471 : : return false;
472 : :
473 : 3 : if (security_capable(file->f_cred, ns, cap, CAP_OPT_NONE) == 0)
474 : : return true;
475 : :
476 : 0 : return false;
477 : : }
478 : : EXPORT_SYMBOL(file_ns_capable);
479 : :
480 : : /**
481 : : * privileged_wrt_inode_uidgid - Do capabilities in the namespace work over the inode?
482 : : * @ns: The user namespace in question
483 : : * @inode: The inode in question
484 : : *
485 : : * Return true if the inode uid and gid are within the namespace.
486 : : */
487 : 3 : bool privileged_wrt_inode_uidgid(struct user_namespace *ns, const struct inode *inode)
488 : : {
489 : 3 : return kuid_has_mapping(ns, inode->i_uid) &&
490 : : kgid_has_mapping(ns, inode->i_gid);
491 : : }
492 : :
493 : : /**
494 : : * capable_wrt_inode_uidgid - Check nsown_capable and uid and gid mapped
495 : : * @inode: The inode in question
496 : : * @cap: The capability in question
497 : : *
498 : : * Return true if the current task has the given capability targeted at
499 : : * its own user namespace and that the given inode's uid and gid are
500 : : * mapped into the current user namespace.
501 : : */
502 : 3 : bool capable_wrt_inode_uidgid(const struct inode *inode, int cap)
503 : : {
504 : 3 : struct user_namespace *ns = current_user_ns();
505 : :
506 : 3 : return ns_capable(ns, cap) && privileged_wrt_inode_uidgid(ns, inode);
507 : : }
508 : : EXPORT_SYMBOL(capable_wrt_inode_uidgid);
509 : :
510 : : /**
511 : : * ptracer_capable - Determine if the ptracer holds CAP_SYS_PTRACE in the namespace
512 : : * @tsk: The task that may be ptraced
513 : : * @ns: The user namespace to search for CAP_SYS_PTRACE in
514 : : *
515 : : * Return true if the task that is ptracing the current task had CAP_SYS_PTRACE
516 : : * in the specified user namespace.
517 : : */
518 : 3 : bool ptracer_capable(struct task_struct *tsk, struct user_namespace *ns)
519 : : {
520 : : int ret = 0; /* An absent tracer adds no restrictions */
521 : : const struct cred *cred;
522 : :
523 : : rcu_read_lock();
524 : 3 : cred = rcu_dereference(tsk->ptracer_cred);
525 : 3 : if (cred)
526 : 0 : ret = security_capable(cred, ns, CAP_SYS_PTRACE,
527 : : CAP_OPT_NOAUDIT);
528 : : rcu_read_unlock();
529 : 3 : return (ret == 0);
530 : : }
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