blob: 4984e1f552ebfb97fa460b527b35c67ebd0f324d
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 | static 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 | |
45 | static 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 | |
69 | static 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 | */ |
81 | static 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 | */ |
117 | static 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 | */ |
149 | SYSCALL_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 | */ |
223 | SYSCALL_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 | |
279 | error: |
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 | */ |
295 | bool 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 | */ |
317 | bool 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 | */ |
335 | 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 | 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 | */ |
359 | bool has_capability_noaudit(struct task_struct *t, int cap) |
360 | { |
361 | return has_ns_capability_noaudit(t, &init_user_ns, cap); |
362 | } |
363 | |
364 | static 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 | */ |
393 | bool ns_capable(struct user_namespace *ns, int cap) |
394 | { |
395 | return ns_capable_common(ns, cap, true); |
396 | } |
397 | EXPORT_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 | */ |
411 | bool ns_capable_noaudit(struct user_namespace *ns, int cap) |
412 | { |
413 | return ns_capable_common(ns, cap, false); |
414 | } |
415 | EXPORT_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 | */ |
427 | bool capable(int cap) |
428 | { |
429 | return ns_capable(&init_user_ns, cap); |
430 | } |
431 | EXPORT_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 | */ |
446 | bool 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 | } |
457 | EXPORT_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 | */ |
466 | bool 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 | */ |
481 | bool 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 | } |
487 | EXPORT_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 | */ |
497 | bool 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 | } |
508 |