Linux kernel mirror (for testing)
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1/* SPDX-License-Identifier: GPL-2.0-or-later */
2/* Credentials management - see Documentation/security/credentials.rst
3 *
4 * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved.
5 * Written by David Howells (dhowells@redhat.com)
6 */
7
8#ifndef _LINUX_CRED_H
9#define _LINUX_CRED_H
10
11#include <linux/capability.h>
12#include <linux/init.h>
13#include <linux/key.h>
14#include <linux/atomic.h>
15#include <linux/refcount.h>
16#include <linux/uidgid.h>
17#include <linux/sched.h>
18#include <linux/sched/user.h>
19
20struct cred;
21struct inode;
22
23extern struct task_struct init_task;
24
25/*
26 * COW Supplementary groups list
27 */
28struct group_info {
29 refcount_t usage;
30 int ngroups;
31 kgid_t gid[];
32} __randomize_layout;
33
34/**
35 * get_group_info - Get a reference to a group info structure
36 * @gi: The group info to reference
37 *
38 * This gets a reference to a set of supplementary groups.
39 *
40 * If the caller is accessing a task's credentials, they must hold the RCU read
41 * lock when reading.
42 *
43 * Returns: @gi
44 */
45static inline struct group_info *get_group_info(struct group_info *gi)
46{
47 refcount_inc(&gi->usage);
48 return gi;
49}
50
51/**
52 * put_group_info - Release a reference to a group info structure
53 * @group_info: The group info to release
54 */
55#define put_group_info(group_info) \
56do { \
57 if (refcount_dec_and_test(&(group_info)->usage)) \
58 groups_free(group_info); \
59} while (0)
60
61#ifdef CONFIG_MULTIUSER
62extern struct group_info *groups_alloc(int);
63extern void groups_free(struct group_info *);
64
65extern int in_group_p(kgid_t);
66extern int in_egroup_p(kgid_t);
67extern int groups_search(const struct group_info *, kgid_t);
68
69extern int set_current_groups(struct group_info *);
70extern void set_groups(struct cred *, struct group_info *);
71extern bool may_setgroups(void);
72extern void groups_sort(struct group_info *);
73#else
74static inline void groups_free(struct group_info *group_info)
75{
76}
77
78static inline int in_group_p(kgid_t grp)
79{
80 return 1;
81}
82static inline int in_egroup_p(kgid_t grp)
83{
84 return 1;
85}
86static inline int groups_search(const struct group_info *group_info, kgid_t grp)
87{
88 return 1;
89}
90#endif
91
92/*
93 * The security context of a task
94 *
95 * The parts of the context break down into two categories:
96 *
97 * (1) The objective context of a task. These parts are used when some other
98 * task is attempting to affect this one.
99 *
100 * (2) The subjective context. These details are used when the task is acting
101 * upon another object, be that a file, a task, a key or whatever.
102 *
103 * Note that some members of this structure belong to both categories - the
104 * LSM security pointer for instance.
105 *
106 * A task has two security pointers. task->real_cred points to the objective
107 * context that defines that task's actual details. The objective part of this
108 * context is used whenever that task is acted upon.
109 *
110 * task->cred points to the subjective context that defines the details of how
111 * that task is going to act upon another object. This may be overridden
112 * temporarily to point to another security context, but normally points to the
113 * same context as task->real_cred.
114 */
115struct cred {
116 atomic_long_t usage;
117 kuid_t uid; /* real UID of the task */
118 kgid_t gid; /* real GID of the task */
119 kuid_t suid; /* saved UID of the task */
120 kgid_t sgid; /* saved GID of the task */
121 kuid_t euid; /* effective UID of the task */
122 kgid_t egid; /* effective GID of the task */
123 kuid_t fsuid; /* UID for VFS ops */
124 kgid_t fsgid; /* GID for VFS ops */
125 unsigned securebits; /* SUID-less security management */
126 kernel_cap_t cap_inheritable; /* caps our children can inherit */
127 kernel_cap_t cap_permitted; /* caps we're permitted */
128 kernel_cap_t cap_effective; /* caps we can actually use */
129 kernel_cap_t cap_bset; /* capability bounding set */
130 kernel_cap_t cap_ambient; /* Ambient capability set */
131#ifdef CONFIG_KEYS
132 unsigned char jit_keyring; /* default keyring to attach requested
133 * keys to */
134 struct key *session_keyring; /* keyring inherited over fork */
135 struct key *process_keyring; /* keyring private to this process */
136 struct key *thread_keyring; /* keyring private to this thread */
137 struct key *request_key_auth; /* assumed request_key authority */
138#endif
139#ifdef CONFIG_SECURITY
140 void *security; /* LSM security */
141#endif
142 struct user_struct *user; /* real user ID subscription */
143 struct user_namespace *user_ns; /* user_ns the caps and keyrings are relative to. */
144 struct ucounts *ucounts;
145 struct group_info *group_info; /* supplementary groups for euid/fsgid */
146 /* RCU deletion */
147 union {
148 int non_rcu; /* Can we skip RCU deletion? */
149 struct rcu_head rcu; /* RCU deletion hook */
150 };
151} __randomize_layout;
152
153extern void __put_cred(struct cred *);
154extern void exit_creds(struct task_struct *);
155extern int copy_creds(struct task_struct *, u64);
156extern const struct cred *get_task_cred(struct task_struct *);
157extern struct cred *cred_alloc_blank(void);
158extern struct cred *prepare_creds(void);
159extern struct cred *prepare_exec_creds(void);
160extern int commit_creds(struct cred *);
161extern void abort_creds(struct cred *);
162extern struct cred *prepare_kernel_cred(struct task_struct *);
163static inline const struct cred *kernel_cred(void)
164{
165 /* shut up sparse */
166 return rcu_dereference_raw(init_task.cred);
167}
168extern int set_security_override(struct cred *, u32);
169extern int set_create_files_as(struct cred *, struct inode *);
170extern int cred_fscmp(const struct cred *, const struct cred *);
171extern void __init cred_init(void);
172extern int set_cred_ucounts(struct cred *);
173
174static inline bool cap_ambient_invariant_ok(const struct cred *cred)
175{
176 return cap_issubset(cred->cap_ambient,
177 cap_intersect(cred->cap_permitted,
178 cred->cap_inheritable));
179}
180
181static inline const struct cred *override_creds(const struct cred *override_cred)
182{
183 return rcu_replace_pointer(current->cred, override_cred, 1);
184}
185
186static inline const struct cred *revert_creds(const struct cred *revert_cred)
187{
188 return rcu_replace_pointer(current->cred, revert_cred, 1);
189}
190
191DEFINE_CLASS(override_creds,
192 const struct cred *,
193 revert_creds(_T),
194 override_creds(override_cred), const struct cred *override_cred)
195
196#define scoped_with_creds(cred) \
197 scoped_class(override_creds, __UNIQUE_ID(label), cred)
198
199#define scoped_with_kernel_creds() scoped_with_creds(kernel_cred())
200
201/**
202 * get_cred_many - Get references on a set of credentials
203 * @cred: The credentials to reference
204 * @nr: Number of references to acquire
205 *
206 * Get references on the specified set of credentials. The caller must release
207 * all acquired reference. If %NULL is passed, it is returned with no action.
208 *
209 * This is used to deal with a committed set of credentials. Although the
210 * pointer is const, this will temporarily discard the const and increment the
211 * usage count. The purpose of this is to attempt to catch at compile time the
212 * accidental alteration of a set of credentials that should be considered
213 * immutable.
214 *
215 * Returns: @cred when the references are acquired, NULL otherwise.
216 */
217static inline const struct cred *get_cred_many(const struct cred *cred, int nr)
218{
219 struct cred *nonconst_cred = (struct cred *) cred;
220 if (!cred)
221 return cred;
222 nonconst_cred->non_rcu = 0;
223 atomic_long_add(nr, &nonconst_cred->usage);
224 return cred;
225}
226
227/*
228 * get_cred - Get a reference on a set of credentials
229 * @cred: The credentials to reference
230 *
231 * Get a reference on the specified set of credentials. The caller must
232 * release the reference. If %NULL is passed, it is returned with no action.
233 *
234 * This is used to deal with a committed set of credentials.
235 */
236static inline const struct cred *get_cred(const struct cred *cred)
237{
238 return get_cred_many(cred, 1);
239}
240
241static inline const struct cred *get_cred_rcu(const struct cred *cred)
242{
243 struct cred *nonconst_cred = (struct cred *) cred;
244 if (!cred)
245 return NULL;
246 if (!atomic_long_inc_not_zero(&nonconst_cred->usage))
247 return NULL;
248 nonconst_cred->non_rcu = 0;
249 return cred;
250}
251
252/**
253 * put_cred_many - Release a reference to a set of credentials
254 * @_cred: The credentials to release
255 * @nr: Number of references to release
256 *
257 * Release a reference to a set of credentials, deleting them when the last ref
258 * is released. If %NULL is passed, nothing is done.
259 *
260 * This takes a const pointer to a set of credentials because the credentials
261 * on task_struct are attached by const pointers to prevent accidental
262 * alteration of otherwise immutable credential sets.
263 */
264static inline void put_cred_many(const struct cred *_cred, int nr)
265{
266 struct cred *cred = (struct cred *) _cred;
267
268 if (cred) {
269 if (atomic_long_sub_and_test(nr, &cred->usage))
270 __put_cred(cred);
271 }
272}
273
274/*
275 * put_cred - Release a reference to a set of credentials
276 * @cred: The credentials to release
277 *
278 * Release a reference to a set of credentials, deleting them when the last ref
279 * is released. If %NULL is passed, nothing is done.
280 */
281static inline void put_cred(const struct cred *cred)
282{
283 put_cred_many(cred, 1);
284}
285
286DEFINE_CLASS(prepare_creds,
287 struct cred *,
288 if (_T) put_cred(_T),
289 prepare_creds(), void)
290
291DEFINE_FREE(put_cred, struct cred *, if (!IS_ERR_OR_NULL(_T)) put_cred(_T))
292
293/**
294 * current_cred - Access the current task's subjective credentials
295 *
296 * Access the subjective credentials of the current task. RCU-safe,
297 * since nobody else can modify it.
298 */
299#define current_cred() \
300 rcu_dereference_protected(current->cred, 1)
301
302/**
303 * current_real_cred - Access the current task's objective credentials
304 *
305 * Access the objective credentials of the current task. RCU-safe,
306 * since nobody else can modify it.
307 */
308#define current_real_cred() \
309 rcu_dereference_protected(current->real_cred, 1)
310
311/**
312 * __task_cred - Access a task's objective credentials
313 * @task: The task to query
314 *
315 * Access the objective credentials of a task. The caller must hold the RCU
316 * readlock.
317 *
318 * The result of this function should not be passed directly to get_cred();
319 * rather get_task_cred() should be used instead.
320 */
321#define __task_cred(task) \
322 rcu_dereference((task)->real_cred)
323
324/**
325 * get_current_cred - Get the current task's subjective credentials
326 *
327 * Get the subjective credentials of the current task, pinning them so that
328 * they can't go away. Accessing the current task's credentials directly is
329 * not permitted.
330 */
331#define get_current_cred() \
332 (get_cred(current_cred()))
333
334/**
335 * get_current_user - Get the current task's user_struct
336 *
337 * Get the user record of the current task, pinning it so that it can't go
338 * away.
339 */
340#define get_current_user() \
341({ \
342 struct user_struct *__u; \
343 const struct cred *__cred; \
344 __cred = current_cred(); \
345 __u = get_uid(__cred->user); \
346 __u; \
347})
348
349/**
350 * get_current_groups - Get the current task's supplementary group list
351 *
352 * Get the supplementary group list of the current task, pinning it so that it
353 * can't go away.
354 */
355#define get_current_groups() \
356({ \
357 struct group_info *__groups; \
358 const struct cred *__cred; \
359 __cred = current_cred(); \
360 __groups = get_group_info(__cred->group_info); \
361 __groups; \
362})
363
364#define task_cred_xxx(task, xxx) \
365({ \
366 __typeof__(((struct cred *)NULL)->xxx) ___val; \
367 rcu_read_lock(); \
368 ___val = __task_cred((task))->xxx; \
369 rcu_read_unlock(); \
370 ___val; \
371})
372
373#define task_uid(task) (task_cred_xxx((task), uid))
374#define task_euid(task) (task_cred_xxx((task), euid))
375#define task_ucounts(task) (task_cred_xxx((task), ucounts))
376
377#define current_cred_xxx(xxx) \
378({ \
379 current_cred()->xxx; \
380})
381
382#define current_uid() (current_cred_xxx(uid))
383#define current_gid() (current_cred_xxx(gid))
384#define current_euid() (current_cred_xxx(euid))
385#define current_egid() (current_cred_xxx(egid))
386#define current_suid() (current_cred_xxx(suid))
387#define current_sgid() (current_cred_xxx(sgid))
388#define current_fsuid() (current_cred_xxx(fsuid))
389#define current_fsgid() (current_cred_xxx(fsgid))
390#define current_cap() (current_cred_xxx(cap_effective))
391#define current_user() (current_cred_xxx(user))
392#define current_ucounts() (current_cred_xxx(ucounts))
393
394extern struct user_namespace init_user_ns;
395#ifdef CONFIG_USER_NS
396#define current_user_ns() (current_cred_xxx(user_ns))
397#else
398static inline struct user_namespace *current_user_ns(void)
399{
400 return &init_user_ns;
401}
402#endif
403
404
405#define current_uid_gid(_uid, _gid) \
406do { \
407 const struct cred *__cred; \
408 __cred = current_cred(); \
409 *(_uid) = __cred->uid; \
410 *(_gid) = __cred->gid; \
411} while(0)
412
413#define current_euid_egid(_euid, _egid) \
414do { \
415 const struct cred *__cred; \
416 __cred = current_cred(); \
417 *(_euid) = __cred->euid; \
418 *(_egid) = __cred->egid; \
419} while(0)
420
421#define current_fsuid_fsgid(_fsuid, _fsgid) \
422do { \
423 const struct cred *__cred; \
424 __cred = current_cred(); \
425 *(_fsuid) = __cred->fsuid; \
426 *(_fsgid) = __cred->fsgid; \
427} while(0)
428
429#endif /* _LINUX_CRED_H */