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 /*
24 * Leveraged for setting/resetting capabilities
25 */
26
27 const kernel_cap_t __cap_empty_set = CAP_EMPTY_SET;
28 EXPORT_SYMBOL(__cap_empty_set);
29
30 int file_caps_enabled = 1;
31
file_caps_disable(char * str)32 static int __init file_caps_disable(char *str)
33 {
34 file_caps_enabled = 0;
35 return 1;
36 }
37 __setup("no_file_caps", file_caps_disable);
38
39 #ifdef CONFIG_MULTIUSER
40 /*
41 * More recent versions of libcap are available from:
42 *
43 * http://www.kernel.org/pub/linux/libs/security/linux-privs/
44 */
45
warn_legacy_capability_use(void)46 static void warn_legacy_capability_use(void)
47 {
48 char name[sizeof(current->comm)];
49
50 pr_info_once("warning: `%s' uses 32-bit capabilities (legacy support in use)\n",
51 get_task_comm(name, current));
52 }
53
54 /*
55 * Version 2 capabilities worked fine, but the linux/capability.h file
56 * that accompanied their introduction encouraged their use without
57 * the necessary user-space source code changes. As such, we have
58 * created a version 3 with equivalent functionality to version 2, but
59 * with a header change to protect legacy source code from using
60 * version 2 when it wanted to use version 1. If your system has code
61 * that trips the following warning, it is using version 2 specific
62 * capabilities and may be doing so insecurely.
63 *
64 * The remedy is to either upgrade your version of libcap (to 2.10+,
65 * if the application is linked against it), or recompile your
66 * application with modern kernel headers and this warning will go
67 * away.
68 */
69
warn_deprecated_v2(void)70 static void warn_deprecated_v2(void)
71 {
72 char name[sizeof(current->comm)];
73
74 pr_info_once("warning: `%s' uses deprecated v2 capabilities in a way that may be insecure\n",
75 get_task_comm(name, current));
76 }
77
78 /*
79 * Version check. Return the number of u32s in each capability flag
80 * array, or a negative value on error.
81 */
cap_validate_magic(cap_user_header_t header,unsigned * tocopy)82 static int cap_validate_magic(cap_user_header_t header, unsigned *tocopy)
83 {
84 __u32 version;
85
86 if (get_user(version, &header->version))
87 return -EFAULT;
88
89 switch (version) {
90 case _LINUX_CAPABILITY_VERSION_1:
91 warn_legacy_capability_use();
92 *tocopy = _LINUX_CAPABILITY_U32S_1;
93 break;
94 case _LINUX_CAPABILITY_VERSION_2:
95 warn_deprecated_v2();
96 /* fall through - v3 is otherwise equivalent to v2. */
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 */
cap_get_target_pid(pid_t pid,kernel_cap_t * pEp,kernel_cap_t * pIp,kernel_cap_t * pPp)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 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 */
SYSCALL_DEFINE2(capget,cap_user_header_t,header,cap_user_data_t,dataptr)148 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 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 */
SYSCALL_DEFINE2(capset,cap_user_header_t,header,const cap_user_data_t,data)222 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 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 effective.cap[CAP_LAST_U32] &= CAP_LAST_U32_VALID_MASK;
262 permitted.cap[CAP_LAST_U32] &= CAP_LAST_U32_VALID_MASK;
263 inheritable.cap[CAP_LAST_U32] &= CAP_LAST_U32_VALID_MASK;
264
265 new = prepare_creds();
266 if (!new)
267 return -ENOMEM;
268
269 ret = security_capset(new, current_cred(),
270 &effective, &inheritable, &permitted);
271 if (ret < 0)
272 goto error;
273
274 audit_log_capset(new, current_cred());
275
276 return commit_creds(new);
277
278 error:
279 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 */
has_ns_capability(struct task_struct * t,struct user_namespace * ns,int cap)294 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 ret = security_capable(__task_cred(t), ns, cap, CAP_OPT_NONE);
301 rcu_read_unlock();
302
303 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 */
has_capability(struct task_struct * t,int cap)316 bool has_capability(struct task_struct *t, int cap)
317 {
318 return has_ns_capability(t, &init_user_ns, cap);
319 }
320 EXPORT_SYMBOL(has_capability);
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 */
has_ns_capability_noaudit(struct task_struct * t,struct user_namespace * ns,int cap)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(__task_cred(t), ns, cap, CAP_OPT_NOAUDIT);
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 */
has_capability_noaudit(struct task_struct * t,int cap)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
ns_capable_common(struct user_namespace * ns,int cap,unsigned int opts)364 static bool ns_capable_common(struct user_namespace *ns,
365 int cap,
366 unsigned int opts)
367 {
368 int capable;
369
370 if (unlikely(!cap_valid(cap))) {
371 pr_crit("capable() called with invalid cap=%u\n", cap);
372 BUG();
373 }
374
375 capable = security_capable(current_cred(), ns, cap, opts);
376 if (capable == 0) {
377 current->flags |= PF_SUPERPRIV;
378 return true;
379 }
380 return false;
381 }
382
383 /**
384 * ns_capable - Determine if the current task has a superior capability in effect
385 * @ns: The usernamespace we want the capability in
386 * @cap: The capability to be tested for
387 *
388 * Return true if the current task has the given superior capability currently
389 * available for use, false if not.
390 *
391 * This sets PF_SUPERPRIV on the task if the capability is available on the
392 * assumption that it's about to be used.
393 */
ns_capable(struct user_namespace * ns,int cap)394 bool ns_capable(struct user_namespace *ns, int cap)
395 {
396 return ns_capable_common(ns, cap, CAP_OPT_NONE);
397 }
398 EXPORT_SYMBOL(ns_capable);
399
400 /**
401 * ns_capable_noaudit - Determine if the current task has a superior capability
402 * (unaudited) in effect
403 * @ns: The usernamespace we want the capability in
404 * @cap: The capability to be tested for
405 *
406 * Return true if the current task has the given superior capability currently
407 * available for use, false if not.
408 *
409 * This sets PF_SUPERPRIV on the task if the capability is available on the
410 * assumption that it's about to be used.
411 */
ns_capable_noaudit(struct user_namespace * ns,int cap)412 bool ns_capable_noaudit(struct user_namespace *ns, int cap)
413 {
414 return ns_capable_common(ns, cap, CAP_OPT_NOAUDIT);
415 }
416 EXPORT_SYMBOL(ns_capable_noaudit);
417
418 /**
419 * ns_capable_setid - Determine if the current task has a superior capability
420 * in effect, while signalling that this check is being done from within a
421 * setid syscall.
422 * @ns: The usernamespace we want the capability in
423 * @cap: The capability to be tested for
424 *
425 * Return true if the current task has the given superior capability currently
426 * available for use, false if not.
427 *
428 * This sets PF_SUPERPRIV on the task if the capability is available on the
429 * assumption that it's about to be used.
430 */
ns_capable_setid(struct user_namespace * ns,int cap)431 bool ns_capable_setid(struct user_namespace *ns, int cap)
432 {
433 return ns_capable_common(ns, cap, CAP_OPT_INSETID);
434 }
435 EXPORT_SYMBOL(ns_capable_setid);
436
437 /**
438 * capable - Determine if the current task has a superior capability in effect
439 * @cap: The capability to be tested for
440 *
441 * Return true if the current task has the given superior capability currently
442 * available for use, false if not.
443 *
444 * This sets PF_SUPERPRIV on the task if the capability is available on the
445 * assumption that it's about to be used.
446 */
capable(int cap)447 bool capable(int cap)
448 {
449 return ns_capable(&init_user_ns, cap);
450 }
451 EXPORT_SYMBOL(capable);
452 #endif /* CONFIG_MULTIUSER */
453
454 /**
455 * file_ns_capable - Determine if the file's opener had a capability in effect
456 * @file: The file we want to check
457 * @ns: The usernamespace we want the capability in
458 * @cap: The capability to be tested for
459 *
460 * Return true if task that opened the file had a capability in effect
461 * when the file was opened.
462 *
463 * This does not set PF_SUPERPRIV because the caller may not
464 * actually be privileged.
465 */
file_ns_capable(const struct file * file,struct user_namespace * ns,int cap)466 bool file_ns_capable(const struct file *file, struct user_namespace *ns,
467 int cap)
468 {
469
470 if (WARN_ON_ONCE(!cap_valid(cap)))
471 return false;
472
473 if (security_capable(file->f_cred, ns, cap, CAP_OPT_NONE) == 0)
474 return true;
475
476 return false;
477 }
478 EXPORT_SYMBOL(file_ns_capable);
479
480 /**
481 * privileged_wrt_inode_uidgid - Do capabilities in the namespace work over the inode?
482 * @ns: The user namespace in question
483 * @inode: The inode in question
484 *
485 * Return true if the inode uid and gid are within the namespace.
486 */
privileged_wrt_inode_uidgid(struct user_namespace * ns,const struct inode * inode)487 bool privileged_wrt_inode_uidgid(struct user_namespace *ns, const struct inode *inode)
488 {
489 return kuid_has_mapping(ns, inode->i_uid) &&
490 kgid_has_mapping(ns, inode->i_gid);
491 }
492
493 /**
494 * capable_wrt_inode_uidgid - Check nsown_capable and uid and gid mapped
495 * @inode: The inode in question
496 * @cap: The capability in question
497 *
498 * Return true if the current task has the given capability targeted at
499 * its own user namespace and that the given inode's uid and gid are
500 * mapped into the current user namespace.
501 */
capable_wrt_inode_uidgid(const struct inode * inode,int cap)502 bool capable_wrt_inode_uidgid(const struct inode *inode, int cap)
503 {
504 struct user_namespace *ns = current_user_ns();
505
506 return ns_capable(ns, cap) && privileged_wrt_inode_uidgid(ns, inode);
507 }
508 EXPORT_SYMBOL(capable_wrt_inode_uidgid);
509
510 /**
511 * ptracer_capable - Determine if the ptracer holds CAP_SYS_PTRACE in the namespace
512 * @tsk: The task that may be ptraced
513 * @ns: The user namespace to search for CAP_SYS_PTRACE in
514 *
515 * Return true if the task that is ptracing the current task had CAP_SYS_PTRACE
516 * in the specified user namespace.
517 */
ptracer_capable(struct task_struct * tsk,struct user_namespace * ns)518 bool ptracer_capable(struct task_struct *tsk, struct user_namespace *ns)
519 {
520 int ret = 0; /* An absent tracer adds no restrictions */
521 const struct cred *cred;
522
523 rcu_read_lock();
524 cred = rcu_dereference(tsk->ptracer_cred);
525 if (cred)
526 ret = security_capable(cred, ns, CAP_SYS_PTRACE,
527 CAP_OPT_NOAUDIT);
528 rcu_read_unlock();
529 return (ret == 0);
530 }
531