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

source code of linux/include/linux/cred.h