projects/linux·blob v3.16-rc5 · refs

442 lines · 11.8 KiB

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 <asm/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/*
39 * More recent versions of libcap are available from:
40 *
41 * http://www.kernel.org/pub/linux/libs/security/linux-privs/
42 */
43
44static void warn_legacy_capability_use(void)
45{
46 char name[sizeof(current->comm)];
47
48 pr_info_once("warning: `%s' uses 32-bit capabilities (legacy support in use)\n",
49 get_task_comm(name, current));
50}
51
52/*
53 * Version 2 capabilities worked fine, but the linux/capability.h file
54 * that accompanied their introduction encouraged their use without
55 * the necessary user-space source code changes. As such, we have
56 * created a version 3 with equivalent functionality to version 2, but
57 * with a header change to protect legacy source code from using
58 * version 2 when it wanted to use version 1. If your system has code
59 * that trips the following warning, it is using version 2 specific
60 * capabilities and may be doing so insecurely.
61 *
62 * The remedy is to either upgrade your version of libcap (to 2.10+,
63 * if the application is linked against it), or recompile your
64 * application with modern kernel headers and this warning will go
65 * away.
66 */
67
68static void warn_deprecated_v2(void)
69{
70 char name[sizeof(current->comm)];
71
72 pr_info_once("warning: `%s' uses deprecated v2 capabilities in a way that may be insecure\n",
73 get_task_comm(name, current));
74}
75
76/*
77 * Version check. Return the number of u32s in each capability flag
78 * array, or a negative value on error.
79 */
80static int cap_validate_magic(cap_user_header_t header, unsigned *tocopy)
81{
82 __u32 version;
83
84 if (get_user(version, &header->version))
85 return -EFAULT;
86
87 switch (version) {
88 case _LINUX_CAPABILITY_VERSION_1:
89 warn_legacy_capability_use();
90 *tocopy = _LINUX_CAPABILITY_U32S_1;
91 break;
92 case _LINUX_CAPABILITY_VERSION_2:
93 warn_deprecated_v2();
94 /*
95 * fall through - v3 is otherwise equivalent to v2.
96 */
97 case _LINUX_CAPABILITY_VERSION_3:
98 *tocopy = _LINUX_CAPABILITY_U32S_3;
99 break;
100 default:
101 if (put_user((u32)_KERNEL_CAPABILITY_VERSION, &header->version))
102 return -EFAULT;
103 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 */
116static 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 if (pid && (pid != task_pid_vnr(current))) {
122 struct task_struct *target;
123
124 rcu_read_lock();
125
126 target = find_task_by_vpid(pid);
127 if (!target)
128 ret = -ESRCH;
129 else
130 ret = security_capget(target, pEp, pIp, pPp);
131
132 rcu_read_unlock();
133 } else
134 ret = security_capget(current, pEp, pIp, pPp);
135
136 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 */
148SYSCALL_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 ret = cap_validate_magic(header, &tocopy);
156 if ((dataptr == NULL) || (ret != 0))
157 return ((dataptr == NULL) && (ret == -EINVAL)) ? 0 : ret;
158
159 if (get_user(pid, &header->pid))
160 return -EFAULT;
161
162 if (pid < 0)
163 return -EINVAL;
164
165 ret = cap_get_target_pid(pid, &pE, &pI, &pP);
166 if (!ret) {
167 struct __user_cap_data_struct kdata[_KERNEL_CAPABILITY_U32S];
168 unsigned i;
169
170 for (i = 0; i < tocopy; i++) {
171 kdata[i].effective = pE.cap[i];
172 kdata[i].permitted = pP.cap[i];
173 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 if (copy_to_user(dataptr, kdata, tocopy
196 * sizeof(struct __user_cap_data_struct))) {
197 return -EFAULT;
198 }
199 }
200
201 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 */
222SYSCALL_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 ret = cap_validate_magic(header, &tocopy);
232 if (ret != 0)
233 return ret;
234
235 if (get_user(pid, &header->pid))
236 return -EFAULT;
237
238 /* may only affect current now */
239 if (pid != 0 && pid != task_pid_vnr(current))
240 return -EPERM;
241
242 copybytes = tocopy * sizeof(struct __user_cap_data_struct);
243 if (copybytes > sizeof(kdata))
244 return -EFAULT;
245
246 if (copy_from_user(&kdata, data, copybytes))
247 return -EFAULT;
248
249 for (i = 0; i < tocopy; i++) {
250 effective.cap[i] = kdata[i].effective;
251 permitted.cap[i] = kdata[i].permitted;
252 inheritable.cap[i] = kdata[i].inheritable;
253 }
254 while (i < _KERNEL_CAPABILITY_U32S) {
255 effective.cap[i] = 0;
256 permitted.cap[i] = 0;
257 inheritable.cap[i] = 0;
258 i++;
259 }
260
261 new = prepare_creds();
262 if (!new)
263 return -ENOMEM;
264
265 ret = security_capset(new, current_cred(),
266 &effective, &inheritable, &permitted);
267 if (ret < 0)
268 goto error;
269
270 audit_log_capset(new, current_cred());
271
272 return commit_creds(new);
273
274error:
275 abort_creds(new);
276 return ret;
277}
278
279/**
280 * has_ns_capability - Does a task have a capability in a specific user ns
281 * @t: The task in question
282 * @ns: target user namespace
283 * @cap: The capability to be tested for
284 *
285 * Return true if the specified task has the given superior capability
286 * currently in effect to the specified user namespace, false if not.
287 *
288 * Note that this does not set PF_SUPERPRIV on the task.
289 */
290bool has_ns_capability(struct task_struct *t,
291 struct user_namespace *ns, int cap)
292{
293 int ret;
294
295 rcu_read_lock();
296 ret = security_capable(__task_cred(t), ns, cap);
297 rcu_read_unlock();
298
299 return (ret == 0);
300}
301
302/**
303 * has_capability - Does a task have a capability in init_user_ns
304 * @t: The task in question
305 * @cap: The capability to be tested for
306 *
307 * Return true if the specified task has the given superior capability
308 * currently in effect to the initial user namespace, false if not.
309 *
310 * Note that this does not set PF_SUPERPRIV on the task.
311 */
312bool has_capability(struct task_struct *t, int cap)
313{
314 return has_ns_capability(t, &init_user_ns, cap);
315}
316
317/**
318 * has_ns_capability_noaudit - Does a task have a capability (unaudited)
319 * in a specific user ns.
320 * @t: The task in question
321 * @ns: target user namespace
322 * @cap: The capability to be tested for
323 *
324 * Return true if the specified task has the given superior capability
325 * currently in effect to the specified user namespace, false if not.
326 * Do not write an audit message for the check.
327 *
328 * Note that this does not set PF_SUPERPRIV on the task.
329 */
330bool has_ns_capability_noaudit(struct task_struct *t,
331 struct user_namespace *ns, int cap)
332{
333 int ret;
334
335 rcu_read_lock();
336 ret = security_capable_noaudit(__task_cred(t), ns, cap);
337 rcu_read_unlock();
338
339 return (ret == 0);
340}
341
342/**
343 * has_capability_noaudit - Does a task have a capability (unaudited) in the
344 * initial user ns
345 * @t: The task in question
346 * @cap: The capability to be tested for
347 *
348 * Return true if the specified task has the given superior capability
349 * currently in effect to init_user_ns, false if not. Don't write an
350 * audit message for the check.
351 *
352 * Note that this does not set PF_SUPERPRIV on the task.
353 */
354bool has_capability_noaudit(struct task_struct *t, int cap)
355{
356 return has_ns_capability_noaudit(t, &init_user_ns, cap);
357}
358
359/**
360 * ns_capable - Determine if the current task has a superior capability in effect
361 * @ns: The usernamespace we want the capability in
362 * @cap: The capability to be tested for
363 *
364 * Return true if the current task has the given superior capability currently
365 * available for use, false if not.
366 *
367 * This sets PF_SUPERPRIV on the task if the capability is available on the
368 * assumption that it's about to be used.
369 */
370bool ns_capable(struct user_namespace *ns, int cap)
371{
372 if (unlikely(!cap_valid(cap))) {
373 pr_crit("capable() called with invalid cap=%u\n", cap);
374 BUG();
375 }
376
377 if (security_capable(current_cred(), ns, cap) == 0) {
378 current->flags |= PF_SUPERPRIV;
379 return true;
380 }
381 return false;
382}
383EXPORT_SYMBOL(ns_capable);
384
385/**
386 * file_ns_capable - Determine if the file's opener had a capability in effect
387 * @file: The file we want to check
388 * @ns: The usernamespace we want the capability in
389 * @cap: The capability to be tested for
390 *
391 * Return true if task that opened the file had a capability in effect
392 * when the file was opened.
393 *
394 * This does not set PF_SUPERPRIV because the caller may not
395 * actually be privileged.
396 */
397bool file_ns_capable(const struct file *file, struct user_namespace *ns,
398 int cap)
399{
400 if (WARN_ON_ONCE(!cap_valid(cap)))
401 return false;
402
403 if (security_capable(file->f_cred, ns, cap) == 0)
404 return true;
405
406 return false;
407}
408EXPORT_SYMBOL(file_ns_capable);
409
410/**
411 * capable - Determine if the current task has a superior capability in effect
412 * @cap: The capability to be tested for
413 *
414 * Return true if the current task has the given superior capability currently
415 * available for use, false if not.
416 *
417 * This sets PF_SUPERPRIV on the task if the capability is available on the
418 * assumption that it's about to be used.
419 */
420bool capable(int cap)
421{
422 return ns_capable(&init_user_ns, cap);
423}
424EXPORT_SYMBOL(capable);
425
426/**
427 * capable_wrt_inode_uidgid - Check nsown_capable and uid and gid mapped
428 * @inode: The inode in question
429 * @cap: The capability in question
430 *
431 * Return true if the current task has the given capability targeted at
432 * its own user namespace and that the given inode's uid and gid are
433 * mapped into the current user namespace.
434 */
435bool capable_wrt_inode_uidgid(const struct inode *inode, int cap)
436{
437 struct user_namespace *ns = current_user_ns();
438
439 return ns_capable(ns, cap) && kuid_has_mapping(ns, inode->i_uid) &&
440 kgid_has_mapping(ns, inode->i_gid);
441}
442EXPORT_SYMBOL(capable_wrt_inode_uidgid);