projects/linux·blob v4.10-rc1 · refs

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1/*
2 * linux/kernel/capability.c
3 *
4 * Copyright (C) 1997 Andrew Main <[email protected]>
5 *
6 * Integrated into 2.1.97+, Andrew G. Morgan <[email protected]>
7 * 30 May 2002: Cleanup, Robert M. Love <[email protected]>
8 */
9
10#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
11
12#include <linux/audit.h>
13#include <linux/capability.h>
14#include <linux/mm.h>
15#include <linux/export.h>
16#include <linux/security.h>
17#include <linux/syscalls.h>
18#include <linux/pid_namespace.h>
19#include <linux/user_namespace.h>
20#include <linux/uaccess.h>
21
22/*
23 * Leveraged for setting/resetting capabilities
24 */
25
26const kernel_cap_t __cap_empty_set = CAP_EMPTY_SET;
27EXPORT_SYMBOL(__cap_empty_set);
28
29int file_caps_enabled = 1;
30
31static int __init file_caps_disable(char *str)
32{
33 file_caps_enabled = 0;
34 return 1;
35}
36__setup("no_file_caps", file_caps_disable);
37
38#ifdef CONFIG_MULTIUSER
39/*
40 * More recent versions of libcap are available from:
41 *
42 * http://www.kernel.org/pub/linux/libs/security/linux-privs/
43 */
44
45static void warn_legacy_capability_use(void)
46{
47 char name[sizeof(current->comm)];
48
49 pr_info_once("warning: `%s' uses 32-bit capabilities (legacy support in use)\n",
50 get_task_comm(name, current));
51}
52
53/*
54 * Version 2 capabilities worked fine, but the linux/capability.h file
55 * that accompanied their introduction encouraged their use without
56 * the necessary user-space source code changes. As such, we have
57 * created a version 3 with equivalent functionality to version 2, but
58 * with a header change to protect legacy source code from using
59 * version 2 when it wanted to use version 1. If your system has code
60 * that trips the following warning, it is using version 2 specific
61 * capabilities and may be doing so insecurely.
62 *
63 * The remedy is to either upgrade your version of libcap (to 2.10+,
64 * if the application is linked against it), or recompile your
65 * application with modern kernel headers and this warning will go
66 * away.
67 */
68
69static void warn_deprecated_v2(void)
70{
71 char name[sizeof(current->comm)];
72
73 pr_info_once("warning: `%s' uses deprecated v2 capabilities in a way that may be insecure\n",
74 get_task_comm(name, current));
75}
76
77/*
78 * Version check. Return the number of u32s in each capability flag
79 * array, or a negative value on error.
80 */
81static int cap_validate_magic(cap_user_header_t header, unsigned *tocopy)
82{
83 __u32 version;
84
85 if (get_user(version, &header->version))
86 return -EFAULT;
87
88 switch (version) {
89 case _LINUX_CAPABILITY_VERSION_1:
90 warn_legacy_capability_use();
91 *tocopy = _LINUX_CAPABILITY_U32S_1;
92 break;
93 case _LINUX_CAPABILITY_VERSION_2:
94 warn_deprecated_v2();
95 /*
96 * fall through - v3 is otherwise equivalent to v2.
97 */
98 case _LINUX_CAPABILITY_VERSION_3:
99 *tocopy = _LINUX_CAPABILITY_U32S_3;
100 break;
101 default:
102 if (put_user((u32)_KERNEL_CAPABILITY_VERSION, &header->version))
103 return -EFAULT;
104 return -EINVAL;
105 }
106
107 return 0;
108}
109
110/*
111 * The only thing that can change the capabilities of the current
112 * process is the current process. As such, we can't be in this code
113 * at the same time as we are in the process of setting capabilities
114 * in this process. The net result is that we can limit our use of
115 * locks to when we are reading the caps of another process.
116 */
117static inline int cap_get_target_pid(pid_t pid, kernel_cap_t *pEp,
118 kernel_cap_t *pIp, kernel_cap_t *pPp)
119{
120 int ret;
121
122 if (pid && (pid != task_pid_vnr(current))) {
123 struct task_struct *target;
124
125 rcu_read_lock();
126
127 target = find_task_by_vpid(pid);
128 if (!target)
129 ret = -ESRCH;
130 else
131 ret = security_capget(target, pEp, pIp, pPp);
132
133 rcu_read_unlock();
134 } else
135 ret = security_capget(current, pEp, pIp, pPp);
136
137 return ret;
138}
139
140/**
141 * sys_capget - get the capabilities of a given process.
142 * @header: pointer to struct that contains capability version and
143 * target pid data
144 * @dataptr: pointer to struct that contains the effective, permitted,
145 * and inheritable capabilities that are returned
146 *
147 * Returns 0 on success and < 0 on error.
148 */
149SYSCALL_DEFINE2(capget, cap_user_header_t, header, cap_user_data_t, dataptr)
150{
151 int ret = 0;
152 pid_t pid;
153 unsigned tocopy;
154 kernel_cap_t pE, pI, pP;
155
156 ret = cap_validate_magic(header, &tocopy);
157 if ((dataptr == NULL) || (ret != 0))
158 return ((dataptr == NULL) && (ret == -EINVAL)) ? 0 : ret;
159
160 if (get_user(pid, &header->pid))
161 return -EFAULT;
162
163 if (pid < 0)
164 return -EINVAL;
165
166 ret = cap_get_target_pid(pid, &pE, &pI, &pP);
167 if (!ret) {
168 struct __user_cap_data_struct kdata[_KERNEL_CAPABILITY_U32S];
169 unsigned i;
170
171 for (i = 0; i < tocopy; i++) {
172 kdata[i].effective = pE.cap[i];
173 kdata[i].permitted = pP.cap[i];
174 kdata[i].inheritable = pI.cap[i];
175 }
176
177 /*
178 * Note, in the case, tocopy < _KERNEL_CAPABILITY_U32S,
179 * we silently drop the upper capabilities here. This
180 * has the effect of making older libcap
181 * implementations implicitly drop upper capability
182 * bits when they perform a: capget/modify/capset
183 * sequence.
184 *
185 * This behavior is considered fail-safe
186 * behavior. Upgrading the application to a newer
187 * version of libcap will enable access to the newer
188 * capabilities.
189 *
190 * An alternative would be to return an error here
191 * (-ERANGE), but that causes legacy applications to
192 * unexpectedly fail; the capget/modify/capset aborts
193 * before modification is attempted and the application
194 * fails.
195 */
196 if (copy_to_user(dataptr, kdata, tocopy
197 * sizeof(struct __user_cap_data_struct))) {
198 return -EFAULT;
199 }
200 }
201
202 return ret;
203}
204
205/**
206 * sys_capset - set capabilities for a process or (*) a group of processes
207 * @header: pointer to struct that contains capability version and
208 * target pid data
209 * @data: pointer to struct that contains the effective, permitted,
210 * and inheritable capabilities
211 *
212 * Set capabilities for the current process only. The ability to any other
213 * process(es) has been deprecated and removed.
214 *
215 * The restrictions on setting capabilities are specified as:
216 *
217 * I: any raised capabilities must be a subset of the old permitted
218 * P: any raised capabilities must be a subset of the old permitted
219 * E: must be set to a subset of new permitted
220 *
221 * Returns 0 on success and < 0 on error.
222 */
223SYSCALL_DEFINE2(capset, cap_user_header_t, header, const cap_user_data_t, data)
224{
225 struct __user_cap_data_struct kdata[_KERNEL_CAPABILITY_U32S];
226 unsigned i, tocopy, copybytes;
227 kernel_cap_t inheritable, permitted, effective;
228 struct cred *new;
229 int ret;
230 pid_t pid;
231
232 ret = cap_validate_magic(header, &tocopy);
233 if (ret != 0)
234 return ret;
235
236 if (get_user(pid, &header->pid))
237 return -EFAULT;
238
239 /* may only affect current now */
240 if (pid != 0 && pid != task_pid_vnr(current))
241 return -EPERM;
242
243 copybytes = tocopy * sizeof(struct __user_cap_data_struct);
244 if (copybytes > sizeof(kdata))
245 return -EFAULT;
246
247 if (copy_from_user(&kdata, data, copybytes))
248 return -EFAULT;
249
250 for (i = 0; i < tocopy; i++) {
251 effective.cap[i] = kdata[i].effective;
252 permitted.cap[i] = kdata[i].permitted;
253 inheritable.cap[i] = kdata[i].inheritable;
254 }
255 while (i < _KERNEL_CAPABILITY_U32S) {
256 effective.cap[i] = 0;
257 permitted.cap[i] = 0;
258 inheritable.cap[i] = 0;
259 i++;
260 }
261
262 effective.cap[CAP_LAST_U32] &= CAP_LAST_U32_VALID_MASK;
263 permitted.cap[CAP_LAST_U32] &= CAP_LAST_U32_VALID_MASK;
264 inheritable.cap[CAP_LAST_U32] &= CAP_LAST_U32_VALID_MASK;
265
266 new = prepare_creds();
267 if (!new)
268 return -ENOMEM;
269
270 ret = security_capset(new, current_cred(),
271 &effective, &inheritable, &permitted);
272 if (ret < 0)
273 goto error;
274
275 audit_log_capset(new, current_cred());
276
277 return commit_creds(new);
278
279error:
280 abort_creds(new);
281 return ret;
282}
283
284/**
285 * has_ns_capability - Does a task have a capability in a specific user ns
286 * @t: The task in question
287 * @ns: target user namespace
288 * @cap: The capability to be tested for
289 *
290 * Return true if the specified task has the given superior capability
291 * currently in effect to the specified user namespace, false if not.
292 *
293 * Note that this does not set PF_SUPERPRIV on the task.
294 */
295bool has_ns_capability(struct task_struct *t,
296 struct user_namespace *ns, int cap)
297{
298 int ret;
299
300 rcu_read_lock();
301 ret = security_capable(__task_cred(t), ns, cap);
302 rcu_read_unlock();
303
304 return (ret == 0);
305}
306
307/**
308 * has_capability - Does a task have a capability in init_user_ns
309 * @t: The task in question
310 * @cap: The capability to be tested for
311 *
312 * Return true if the specified task has the given superior capability
313 * currently in effect to the initial user namespace, false if not.
314 *
315 * Note that this does not set PF_SUPERPRIV on the task.
316 */
317bool has_capability(struct task_struct *t, int cap)
318{
319 return has_ns_capability(t, &init_user_ns, cap);
320}
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 */
335bool 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 ret = security_capable_noaudit(__task_cred(t), ns, cap);
342 rcu_read_unlock();
343
344 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 */
359bool has_capability_noaudit(struct task_struct *t, int cap)
360{
361 return has_ns_capability_noaudit(t, &init_user_ns, cap);
362}
363
364static bool ns_capable_common(struct user_namespace *ns, int cap, bool audit)
365{
366 int capable;
367
368 if (unlikely(!cap_valid(cap))) {
369 pr_crit("capable() called with invalid cap=%u\n", cap);
370 BUG();
371 }
372
373 capable = audit ? security_capable(current_cred(), ns, cap) :
374 security_capable_noaudit(current_cred(), ns, cap);
375 if (capable == 0) {
376 current->flags |= PF_SUPERPRIV;
377 return true;
378 }
379 return false;
380}
381
382/**
383 * ns_capable - Determine if the current task has a superior capability in effect
384 * @ns: The usernamespace we want the capability in
385 * @cap: The capability to be tested for
386 *
387 * Return true if the current task has the given superior capability currently
388 * available for use, false if not.
389 *
390 * This sets PF_SUPERPRIV on the task if the capability is available on the
391 * assumption that it's about to be used.
392 */
393bool ns_capable(struct user_namespace *ns, int cap)
394{
395 return ns_capable_common(ns, cap, true);
396}
397EXPORT_SYMBOL(ns_capable);
398
399/**
400 * ns_capable_noaudit - Determine if the current task has a superior capability
401 * (unaudited) in effect
402 * @ns: The usernamespace we want the capability in
403 * @cap: The capability to be tested for
404 *
405 * Return true if the current task has the given superior capability currently
406 * available for use, false if not.
407 *
408 * This sets PF_SUPERPRIV on the task if the capability is available on the
409 * assumption that it's about to be used.
410 */
411bool ns_capable_noaudit(struct user_namespace *ns, int cap)
412{
413 return ns_capable_common(ns, cap, false);
414}
415EXPORT_SYMBOL(ns_capable_noaudit);
416
417/**
418 * capable - Determine if the current task has a superior capability in effect
419 * @cap: The capability to be tested for
420 *
421 * Return true if the current task has the given superior capability currently
422 * available for use, false if not.
423 *
424 * This sets PF_SUPERPRIV on the task if the capability is available on the
425 * assumption that it's about to be used.
426 */
427bool capable(int cap)
428{
429 return ns_capable(&init_user_ns, cap);
430}
431EXPORT_SYMBOL(capable);
432#endif /* CONFIG_MULTIUSER */
433
434/**
435 * file_ns_capable - Determine if the file's opener had a capability in effect
436 * @file: The file we want to check
437 * @ns: The usernamespace we want the capability in
438 * @cap: The capability to be tested for
439 *
440 * Return true if task that opened the file had a capability in effect
441 * when the file was opened.
442 *
443 * This does not set PF_SUPERPRIV because the caller may not
444 * actually be privileged.
445 */
446bool file_ns_capable(const struct file *file, struct user_namespace *ns,
447 int cap)
448{
449 if (WARN_ON_ONCE(!cap_valid(cap)))
450 return false;
451
452 if (security_capable(file->f_cred, ns, cap) == 0)
453 return true;
454
455 return false;
456}
457EXPORT_SYMBOL(file_ns_capable);
458
459/**
460 * privileged_wrt_inode_uidgid - Do capabilities in the namespace work over the inode?
461 * @ns: The user namespace in question
462 * @inode: The inode in question
463 *
464 * Return true if the inode uid and gid are within the namespace.
465 */
466bool privileged_wrt_inode_uidgid(struct user_namespace *ns, const struct inode *inode)
467{
468 return kuid_has_mapping(ns, inode->i_uid) &&
469 kgid_has_mapping(ns, inode->i_gid);
470}
471
472/**
473 * capable_wrt_inode_uidgid - Check nsown_capable and uid and gid mapped
474 * @inode: The inode in question
475 * @cap: The capability in question
476 *
477 * Return true if the current task has the given capability targeted at
478 * its own user namespace and that the given inode's uid and gid are
479 * mapped into the current user namespace.
480 */
481bool capable_wrt_inode_uidgid(const struct inode *inode, int cap)
482{
483 struct user_namespace *ns = current_user_ns();
484
485 return ns_capable(ns, cap) && privileged_wrt_inode_uidgid(ns, inode);
486}
487EXPORT_SYMBOL(capable_wrt_inode_uidgid);
488
489/**
490 * ptracer_capable - Determine if the ptracer holds CAP_SYS_PTRACE in the namespace
491 * @tsk: The task that may be ptraced
492 * @ns: The user namespace to search for CAP_SYS_PTRACE in
493 *
494 * Return true if the task that is ptracing the current task had CAP_SYS_PTRACE
495 * in the specified user namespace.
496 */
497bool ptracer_capable(struct task_struct *tsk, struct user_namespace *ns)
498{
499 int ret = 0; /* An absent tracer adds no restrictions */
500 const struct cred *cred;
501 rcu_read_lock();
502 cred = rcu_dereference(tsk->ptracer_cred);
503 if (cred)
504 ret = security_capable_noaudit(cred, ns, CAP_SYS_PTRACE);
505 rcu_read_unlock();
506 return (ret == 0);
507}