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 : int file_caps_enabled = 1;
24 :
25 0 : static int __init file_caps_disable(char *str)
26 : {
27 0 : file_caps_enabled = 0;
28 0 : 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 0 : static void warn_legacy_capability_use(void)
40 : {
41 : char name[sizeof(current->comm)];
42 :
43 0 : pr_info_once("warning: `%s' uses 32-bit capabilities (legacy support in use)\n",
44 : get_task_comm(name, current));
45 0 : }
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 0 : static void warn_deprecated_v2(void)
64 : {
65 : char name[sizeof(current->comm)];
66 :
67 0 : pr_info_once("warning: `%s' uses deprecated v2 capabilities in a way that may be insecure\n",
68 : get_task_comm(name, current));
69 0 : }
70 :
71 : /*
72 : * Version check. Return the number of u32s in each capability flag
73 : * array, or a negative value on error.
74 : */
75 0 : static int cap_validate_magic(cap_user_header_t header, unsigned *tocopy)
76 : {
77 : __u32 version;
78 :
79 0 : if (get_user(version, &header->version))
80 : return -EFAULT;
81 :
82 0 : switch (version) {
83 : case _LINUX_CAPABILITY_VERSION_1:
84 0 : warn_legacy_capability_use();
85 0 : *tocopy = _LINUX_CAPABILITY_U32S_1;
86 0 : break;
87 : case _LINUX_CAPABILITY_VERSION_2:
88 0 : warn_deprecated_v2();
89 : fallthrough; /* v3 is otherwise equivalent to v2 */
90 : case _LINUX_CAPABILITY_VERSION_3:
91 0 : *tocopy = _LINUX_CAPABILITY_U32S_3;
92 0 : break;
93 : default:
94 0 : if (put_user((u32)_KERNEL_CAPABILITY_VERSION, &header->version))
95 : return -EFAULT;
96 0 : 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 0 : 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 0 : if (pid && (pid != task_pid_vnr(current))) {
115 : struct task_struct *target;
116 :
117 : rcu_read_lock();
118 :
119 0 : target = find_task_by_vpid(pid);
120 0 : if (!target)
121 : ret = -ESRCH;
122 : else
123 0 : ret = security_capget(target, pEp, pIp, pPp);
124 :
125 : rcu_read_unlock();
126 : } else
127 0 : ret = security_capget(current, pEp, pIp, pPp);
128 :
129 0 : 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 0 : SYSCALL_DEFINE2(capget, cap_user_header_t, header, cap_user_data_t, dataptr)
142 : {
143 0 : 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 0 : ret = cap_validate_magic(header, &tocopy);
150 0 : if ((dataptr == NULL) || (ret != 0))
151 0 : return ((dataptr == NULL) && (ret == -EINVAL)) ? 0 : ret;
152 :
153 0 : if (get_user(pid, &header->pid))
154 : return -EFAULT;
155 :
156 0 : if (pid < 0)
157 : return -EINVAL;
158 :
159 0 : ret = cap_get_target_pid(pid, &pE, &pI, &pP);
160 0 : if (ret)
161 0 : 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 0 : kdata[0].effective = pE.val; kdata[1].effective = pE.val >> 32;
169 0 : kdata[0].permitted = pP.val; kdata[1].permitted = pP.val >> 32;
170 0 : 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 0 : if (copy_to_user(dataptr, kdata, tocopy * sizeof(kdata[0])))
192 : return -EFAULT;
193 :
194 0 : return 0;
195 : }
196 :
197 : static kernel_cap_t mk_kernel_cap(u32 low, u32 high)
198 : {
199 0 : 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 0 : SYSCALL_DEFINE2(capset, cap_user_header_t, header, const cap_user_data_t, data)
221 : {
222 0 : 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 0 : ret = cap_validate_magic(header, &tocopy);
230 0 : if (ret != 0)
231 0 : return ret;
232 :
233 0 : if (get_user(pid, &header->pid))
234 : return -EFAULT;
235 :
236 : /* may only affect current now */
237 0 : if (pid != 0 && pid != task_pid_vnr(current))
238 : return -EPERM;
239 :
240 0 : copybytes = tocopy * sizeof(struct __user_cap_data_struct);
241 0 : if (copybytes > sizeof(kdata))
242 : return -EFAULT;
243 :
244 0 : if (copy_from_user(&kdata, data, copybytes))
245 : return -EFAULT;
246 :
247 0 : effective = mk_kernel_cap(kdata[0].effective, kdata[1].effective);
248 0 : permitted = mk_kernel_cap(kdata[0].permitted, kdata[1].permitted);
249 0 : inheritable = mk_kernel_cap(kdata[0].inheritable, kdata[1].inheritable);
250 :
251 0 : new = prepare_creds();
252 0 : if (!new)
253 : return -ENOMEM;
254 :
255 0 : ret = security_capset(new, current_cred(),
256 : &effective, &inheritable, &permitted);
257 0 : if (ret < 0)
258 : goto error;
259 :
260 0 : audit_log_capset(new, current_cred());
261 :
262 0 : return commit_creds(new);
263 :
264 : error:
265 0 : abort_creds(new);
266 0 : 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 0 : 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 0 : ret = security_capable(__task_cred(t), ns, cap, CAP_OPT_NONE);
287 : rcu_read_unlock();
288 :
289 0 : 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 0 : bool has_capability(struct task_struct *t, int cap)
303 : {
304 0 : return has_ns_capability(t, &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 0 : 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 0 : ret = security_capable(__task_cred(t), ns, cap, CAP_OPT_NOAUDIT);
328 : rcu_read_unlock();
329 :
330 0 : 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 0 : bool has_capability_noaudit(struct task_struct *t, int cap)
346 : {
347 0 : return has_ns_capability_noaudit(t, &init_user_ns, cap);
348 : }
349 : EXPORT_SYMBOL(has_capability_noaudit);
350 :
351 1 : static bool ns_capable_common(struct user_namespace *ns,
352 : int cap,
353 : unsigned int opts)
354 : {
355 : int capable;
356 :
357 1 : if (unlikely(!cap_valid(cap))) {
358 0 : pr_crit("capable() called with invalid cap=%u\n", cap);
359 0 : BUG();
360 : }
361 :
362 2 : capable = security_capable(current_cred(), ns, cap, opts);
363 1 : if (capable == 0) {
364 1 : current->flags |= PF_SUPERPRIV;
365 1 : 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 0 : bool ns_capable(struct user_namespace *ns, int cap)
382 : {
383 1 : 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 0 : bool ns_capable_noaudit(struct user_namespace *ns, int cap)
400 : {
401 0 : 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 0 : bool ns_capable_setid(struct user_namespace *ns, int cap)
419 : {
420 0 : 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 1 : bool capable(int cap)
435 : {
436 1 : 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 0 : bool file_ns_capable(const struct file *file, struct user_namespace *ns,
454 : int cap)
455 : {
456 :
457 0 : if (WARN_ON_ONCE(!cap_valid(cap)))
458 : return false;
459 :
460 0 : if (security_capable(file->f_cred, ns, cap, CAP_OPT_NONE) == 0)
461 : return true;
462 :
463 0 : 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 : * @inode: The inode in question
471 : *
472 : * Return true if the inode uid and gid are within the namespace.
473 : */
474 0 : bool privileged_wrt_inode_uidgid(struct user_namespace *ns,
475 : struct mnt_idmap *idmap,
476 : const struct inode *inode)
477 : {
478 0 : return vfsuid_has_mapping(ns, i_uid_into_vfsuid(idmap, inode)) &&
479 0 : vfsgid_has_mapping(ns, i_gid_into_vfsgid(idmap, inode));
480 : }
481 :
482 : /**
483 : * capable_wrt_inode_uidgid - Check nsown_capable and uid and gid mapped
484 : * @inode: The inode in question
485 : * @cap: The capability in question
486 : *
487 : * Return true if the current task has the given capability targeted at
488 : * its own user namespace and that the given inode's uid and gid are
489 : * mapped into the current user namespace.
490 : */
491 0 : bool capable_wrt_inode_uidgid(struct mnt_idmap *idmap,
492 : const struct inode *inode, int cap)
493 : {
494 0 : struct user_namespace *ns = current_user_ns();
495 :
496 0 : return ns_capable(ns, cap) &&
497 0 : privileged_wrt_inode_uidgid(ns, idmap, inode);
498 : }
499 : EXPORT_SYMBOL(capable_wrt_inode_uidgid);
500 :
501 : /**
502 : * ptracer_capable - Determine if the ptracer holds CAP_SYS_PTRACE in the namespace
503 : * @tsk: The task that may be ptraced
504 : * @ns: The user namespace to search for CAP_SYS_PTRACE in
505 : *
506 : * Return true if the task that is ptracing the current task had CAP_SYS_PTRACE
507 : * in the specified user namespace.
508 : */
509 0 : bool ptracer_capable(struct task_struct *tsk, struct user_namespace *ns)
510 : {
511 0 : int ret = 0; /* An absent tracer adds no restrictions */
512 : const struct cred *cred;
513 :
514 : rcu_read_lock();
515 0 : cred = rcu_dereference(tsk->ptracer_cred);
516 0 : if (cred)
517 0 : ret = security_capable(cred, ns, CAP_SYS_PTRACE,
518 : CAP_OPT_NOAUDIT);
519 : rcu_read_unlock();
520 0 : return (ret == 0);
521 : }
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