Line data Source code
1 : /*
2 : * linux/kernel/capability.c
3 : *
4 : * Copyright (C) 1997 Andrew Main <zefram@fysh.org>
5 : *
6 : * Integrated into 2.1.97+, Andrew G. Morgan <morgan@kernel.org>
7 : * 30 May 2002: Cleanup, Robert M. Love <rml@tech9.net>
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 :
26 : const kernel_cap_t __cap_empty_set = CAP_EMPTY_SET;
27 : EXPORT_SYMBOL(__cap_empty_set);
28 :
29 : int file_caps_enabled = 1;
30 :
31 0 : static int __init file_caps_disable(char *str)
32 : {
33 0 : file_caps_enabled = 0;
34 0 : 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 :
44 0 : static void warn_legacy_capability_use(void)
45 : {
46 : char name[sizeof(current->comm)];
47 :
48 0 : pr_info_once("warning: `%s' uses 32-bit capabilities (legacy support in use)\n",
49 : get_task_comm(name, current));
50 0 : }
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 :
68 0 : static void warn_deprecated_v2(void)
69 : {
70 : char name[sizeof(current->comm)];
71 :
72 0 : pr_info_once("warning: `%s' uses deprecated v2 capabilities in a way that may be insecure\n",
73 : get_task_comm(name, current));
74 0 : }
75 :
76 : /*
77 : * Version check. Return the number of u32s in each capability flag
78 : * array, or a negative value on error.
79 : */
80 4 : static int cap_validate_magic(cap_user_header_t header, unsigned *tocopy)
81 : {
82 : __u32 version;
83 :
84 4 : if (get_user(version, &header->version))
85 : return -EFAULT;
86 :
87 4 : switch (version) {
88 : case _LINUX_CAPABILITY_VERSION_1:
89 0 : warn_legacy_capability_use();
90 0 : *tocopy = _LINUX_CAPABILITY_U32S_1;
91 0 : break;
92 : case _LINUX_CAPABILITY_VERSION_2:
93 0 : warn_deprecated_v2();
94 : /*
95 : * fall through - v3 is otherwise equivalent to v2.
96 : */
97 : case _LINUX_CAPABILITY_VERSION_3:
98 4 : *tocopy = _LINUX_CAPABILITY_U32S_3;
99 4 : 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 : 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 : 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 : 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 4 : 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 2 : ret = cap_validate_magic(header, &tocopy);
156 2 : if ((dataptr == NULL) || (ret != 0))
157 2 : 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 : 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 0 : * sizeof(struct __user_cap_data_struct))) {
197 0 : 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 : */
222 4 : 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 2 : ret = cap_validate_magic(header, &tocopy);
232 2 : if (ret != 0)
233 : return ret;
234 :
235 2 : if (get_user(pid, &header->pid))
236 : return -EFAULT;
237 :
238 : /* may only affect current now */
239 2 : if (pid != 0 && pid != task_pid_vnr(current))
240 : return -EPERM;
241 :
242 2 : copybytes = tocopy * sizeof(struct __user_cap_data_struct);
243 2 : if (copybytes > sizeof(kdata))
244 : return -EFAULT;
245 :
246 2 : if (copy_from_user(&kdata, data, copybytes))
247 : return -EFAULT;
248 :
249 4 : for (i = 0; i < tocopy; i++) {
250 4 : effective.cap[i] = kdata[i].effective;
251 4 : permitted.cap[i] = kdata[i].permitted;
252 4 : inheritable.cap[i] = kdata[i].inheritable;
253 : }
254 2 : 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 2 : effective.cap[CAP_LAST_U32] &= CAP_LAST_U32_VALID_MASK;
262 2 : permitted.cap[CAP_LAST_U32] &= CAP_LAST_U32_VALID_MASK;
263 2 : inheritable.cap[CAP_LAST_U32] &= CAP_LAST_U32_VALID_MASK;
264 :
265 2 : new = prepare_creds();
266 2 : if (!new)
267 : return -ENOMEM;
268 :
269 2 : ret = security_capset(new, current_cred(),
270 : &effective, &inheritable, &permitted);
271 2 : if (ret < 0)
272 : goto error;
273 :
274 : audit_log_capset(new, current_cred());
275 :
276 2 : return commit_creds(new);
277 :
278 : error:
279 0 : abort_creds(new);
280 : 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 : */
294 240 : bool has_ns_capability(struct task_struct *t,
295 : struct user_namespace *ns, int cap)
296 : {
297 : int ret;
298 :
299 : rcu_read_lock();
300 240 : ret = security_capable(__task_cred(t), ns, cap);
301 : rcu_read_unlock();
302 :
303 240 : 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 :
321 : /**
322 : * has_ns_capability_noaudit - Does a task have a capability (unaudited)
323 : * in a specific user ns.
324 : * @t: The task in question
325 : * @ns: target user namespace
326 : * @cap: The capability to be tested for
327 : *
328 : * Return true if the specified task has the given superior capability
329 : * currently in effect to the specified user namespace, false if not.
330 : * Do not write an audit message for the check.
331 : *
332 : * Note that this does not set PF_SUPERPRIV on the task.
333 : */
334 504 : bool has_ns_capability_noaudit(struct task_struct *t,
335 : struct user_namespace *ns, int cap)
336 : {
337 : int ret;
338 :
339 : rcu_read_lock();
340 504 : ret = security_capable_noaudit(__task_cred(t), ns, cap);
341 : rcu_read_unlock();
342 :
343 504 : return (ret == 0);
344 : }
345 :
346 : /**
347 : * has_capability_noaudit - Does a task have a capability (unaudited) in the
348 : * initial user ns
349 : * @t: The task in question
350 : * @cap: The capability to be tested for
351 : *
352 : * Return true if the specified task has the given superior capability
353 : * currently in effect to init_user_ns, false if not. Don't write an
354 : * audit message for the check.
355 : *
356 : * Note that this does not set PF_SUPERPRIV on the task.
357 : */
358 12 : bool has_capability_noaudit(struct task_struct *t, int cap)
359 : {
360 12 : return has_ns_capability_noaudit(t, &init_user_ns, cap);
361 : }
362 :
363 : /**
364 : * ns_capable - Determine if the current task has a superior capability in effect
365 : * @ns: The usernamespace we want the capability in
366 : * @cap: The capability to be tested for
367 : *
368 : * Return true if the current task has the given superior capability currently
369 : * available for use, false if not.
370 : *
371 : * This sets PF_SUPERPRIV on the task if the capability is available on the
372 : * assumption that it's about to be used.
373 : */
374 37420 : bool ns_capable(struct user_namespace *ns, int cap)
375 : {
376 37420 : if (unlikely(!cap_valid(cap))) {
377 0 : pr_crit("capable() called with invalid cap=%u\n", cap);
378 : BUG();
379 : }
380 :
381 74840 : if (security_capable(current_cred(), ns, cap) == 0) {
382 32066 : current->flags |= PF_SUPERPRIV;
383 32066 : return true;
384 : }
385 : return false;
386 : }
387 : EXPORT_SYMBOL(ns_capable);
388 :
389 : /**
390 : * file_ns_capable - Determine if the file's opener had a capability in effect
391 : * @file: The file we want to check
392 : * @ns: The usernamespace we want the capability in
393 : * @cap: The capability to be tested for
394 : *
395 : * Return true if task that opened the file had a capability in effect
396 : * when the file was opened.
397 : *
398 : * This does not set PF_SUPERPRIV because the caller may not
399 : * actually be privileged.
400 : */
401 2 : bool file_ns_capable(const struct file *file, struct user_namespace *ns,
402 : int cap)
403 : {
404 2 : if (WARN_ON_ONCE(!cap_valid(cap)))
405 : return false;
406 :
407 4 : if (security_capable(file->f_cred, ns, cap) == 0)
408 : return true;
409 :
410 0 : return false;
411 : }
412 : EXPORT_SYMBOL(file_ns_capable);
413 :
414 : /**
415 : * capable - Determine if the current task has a superior capability in effect
416 : * @cap: The capability to be tested for
417 : *
418 : * Return true if the current task has the given superior capability currently
419 : * available for use, false if not.
420 : *
421 : * This sets PF_SUPERPRIV on the task if the capability is available on the
422 : * assumption that it's about to be used.
423 : */
424 28936 : bool capable(int cap)
425 : {
426 28936 : return ns_capable(&init_user_ns, cap);
427 : }
428 : EXPORT_SYMBOL(capable);
429 :
430 : /**
431 : * capable_wrt_inode_uidgid - Check nsown_capable and uid and gid mapped
432 : * @inode: The inode in question
433 : * @cap: The capability in question
434 : *
435 : * Return true if the current task has the given capability targeted at
436 : * its own user namespace and that the given inode's uid and gid are
437 : * mapped into the current user namespace.
438 : */
439 5472 : bool capable_wrt_inode_uidgid(const struct inode *inode, int cap)
440 : {
441 : struct user_namespace *ns = current_user_ns();
442 :
443 5472 : return ns_capable(ns, cap) && kuid_has_mapping(ns, inode->i_uid) &&
444 : kgid_has_mapping(ns, inode->i_gid);
445 : }
446 : EXPORT_SYMBOL(capable_wrt_inode_uidgid);
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