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/uidgid.h>
16#include <linux/sched.h>
17#include <linux/sched/user.h>
18
19struct cred;
20struct inode;
21
22/*
23 * COW Supplementary groups list
24 */
25struct group_info {
26 atomic_t usage;
27 int ngroups;
28 kgid_t gid[];
29} __randomize_layout;
30
31/**
32 * get_group_info - Get a reference to a group info structure
33 * @group_info: The group info to reference
34 *
35 * This gets a reference to a set of supplementary groups.
36 *
37 * If the caller is accessing a task's credentials, they must hold the RCU read
38 * lock when reading.
39 */
40static inline struct group_info *get_group_info(struct group_info *gi)
41{
42 atomic_inc(&gi->usage);
43 return gi;
44}
45
46/**
47 * put_group_info - Release a reference to a group info structure
48 * @group_info: The group info to release
49 */
50#define put_group_info(group_info) \
51do { \
52 if (atomic_dec_and_test(&(group_info)->usage)) \
53 groups_free(group_info); \
54} while (0)
55
56#ifdef CONFIG_MULTIUSER
57extern struct group_info *groups_alloc(int);
58extern void groups_free(struct group_info *);
59
60extern int in_group_p(kgid_t);
61extern int in_egroup_p(kgid_t);
62extern int groups_search(const struct group_info *, kgid_t);
63
64extern int set_current_groups(struct group_info *);
65extern void set_groups(struct cred *, struct group_info *);
66extern bool may_setgroups(void);
67extern void groups_sort(struct group_info *);
68#else
69static inline void groups_free(struct group_info *group_info)
70{
71}
72
73static inline int in_group_p(kgid_t grp)
74{
75 return 1;
76}
77static inline int in_egroup_p(kgid_t grp)
78{
79 return 1;
80}
81static inline int groups_search(const struct group_info *group_info, kgid_t grp)
82{
83 return 1;
84}
85#endif
86
87/*
88 * The security context of a task
89 *
90 * The parts of the context break down into two categories:
91 *
92 * (1) The objective context of a task. These parts are used when some other
93 * task is attempting to affect this one.
94 *
95 * (2) The subjective context. These details are used when the task is acting
96 * upon another object, be that a file, a task, a key or whatever.
97 *
98 * Note that some members of this structure belong to both categories - the
99 * LSM security pointer for instance.
100 *
101 * A task has two security pointers. task->real_cred points to the objective
102 * context that defines that task's actual details. The objective part of this
103 * context is used whenever that task is acted upon.
104 *
105 * task->cred points to the subjective context that defines the details of how
106 * that task is going to act upon another object. This may be overridden
107 * temporarily to point to another security context, but normally points to the
108 * same context as task->real_cred.
109 */
110struct cred {
111 atomic_t usage;
112#ifdef CONFIG_DEBUG_CREDENTIALS
113 atomic_t subscribers; /* number of processes subscribed */
114 void *put_addr;
115 unsigned magic;
116#define CRED_MAGIC 0x43736564
117#define CRED_MAGIC_DEAD 0x44656144
118#endif
119 kuid_t uid; /* real UID of the task */
120 kgid_t gid; /* real GID of the task */
121 kuid_t suid; /* saved UID of the task */
122 kgid_t sgid; /* saved GID of the task */
123 kuid_t euid; /* effective UID of the task */
124 kgid_t egid; /* effective GID of the task */
125 kuid_t fsuid; /* UID for VFS ops */
126 kgid_t fsgid; /* GID for VFS ops */
127 unsigned securebits; /* SUID-less security management */
128 kernel_cap_t cap_inheritable; /* caps our children can inherit */
129 kernel_cap_t cap_permitted; /* caps we're permitted */
130 kernel_cap_t cap_effective; /* caps we can actually use */
131 kernel_cap_t cap_bset; /* capability bounding set */
132 kernel_cap_t cap_ambient; /* Ambient capability set */
133#ifdef CONFIG_KEYS
134 unsigned char jit_keyring; /* default keyring to attach requested
135 * keys to */
136 struct key *session_keyring; /* keyring inherited over fork */
137 struct key *process_keyring; /* keyring private to this process */
138 struct key *thread_keyring; /* keyring private to this thread */
139 struct key *request_key_auth; /* assumed request_key authority */
140#endif
141#ifdef CONFIG_SECURITY
142 void *security; /* LSM security */
143#endif
144 struct user_struct *user; /* real user ID subscription */
145 struct user_namespace *user_ns; /* user_ns the caps and keyrings are relative to. */
146 struct ucounts *ucounts;
147 struct group_info *group_info; /* supplementary groups for euid/fsgid */
148 /* RCU deletion */
149 union {
150 int non_rcu; /* Can we skip RCU deletion? */
151 struct rcu_head rcu; /* RCU deletion hook */
152 };
153} __randomize_layout;
154
155extern void __put_cred(struct cred *);
156extern void exit_creds(struct task_struct *);
157extern int copy_creds(struct task_struct *, unsigned long);
158extern const struct cred *get_task_cred(struct task_struct *);
159extern struct cred *cred_alloc_blank(void);
160extern struct cred *prepare_creds(void);
161extern struct cred *prepare_exec_creds(void);
162extern int commit_creds(struct cred *);
163extern void abort_creds(struct cred *);
164extern const struct cred *override_creds(const struct cred *);
165extern void revert_creds(const struct cred *);
166extern struct cred *prepare_kernel_cred(struct task_struct *);
167extern int change_create_files_as(struct cred *, struct inode *);
168extern int set_security_override(struct cred *, u32);
169extern int set_security_override_from_ctx(struct cred *, const char *);
170extern int set_create_files_as(struct cred *, struct inode *);
171extern int cred_fscmp(const struct cred *, const struct cred *);
172extern void __init cred_init(void);
173extern int set_cred_ucounts(struct cred *);
174
175/*
176 * check for validity of credentials
177 */
178#ifdef CONFIG_DEBUG_CREDENTIALS
179extern void __noreturn __invalid_creds(const struct cred *, const char *, unsigned);
180extern void __validate_process_creds(struct task_struct *,
181 const char *, unsigned);
182
183extern bool creds_are_invalid(const struct cred *cred);
184
185static inline void __validate_creds(const struct cred *cred,
186 const char *file, unsigned line)
187{
188 if (unlikely(creds_are_invalid(cred)))
189 __invalid_creds(cred, file, line);
190}
191
192#define validate_creds(cred) \
193do { \
194 __validate_creds((cred), __FILE__, __LINE__); \
195} while(0)
196
197#define validate_process_creds() \
198do { \
199 __validate_process_creds(current, __FILE__, __LINE__); \
200} while(0)
201
202extern void validate_creds_for_do_exit(struct task_struct *);
203#else
204static inline void validate_creds(const struct cred *cred)
205{
206}
207static inline void validate_creds_for_do_exit(struct task_struct *tsk)
208{
209}
210static inline void validate_process_creds(void)
211{
212}
213#endif
214
215static inline bool cap_ambient_invariant_ok(const struct cred *cred)
216{
217 return cap_issubset(cred->cap_ambient,
218 cap_intersect(cred->cap_permitted,
219 cred->cap_inheritable));
220}
221
222/**
223 * get_new_cred - Get a reference on a new set of credentials
224 * @cred: The new credentials to reference
225 *
226 * Get a reference on the specified set of new credentials. The caller must
227 * release the reference.
228 */
229static inline struct cred *get_new_cred(struct cred *cred)
230{
231 atomic_inc(&cred->usage);
232 return cred;
233}
234
235/**
236 * get_cred - Get a reference on a set of credentials
237 * @cred: The credentials to reference
238 *
239 * Get a reference on the specified set of credentials. The caller must
240 * release the reference. If %NULL is passed, it is returned with no action.
241 *
242 * This is used to deal with a committed set of credentials. Although the
243 * pointer is const, this will temporarily discard the const and increment the
244 * usage count. The purpose of this is to attempt to catch at compile time the
245 * accidental alteration of a set of credentials that should be considered
246 * immutable.
247 */
248static inline const struct cred *get_cred(const struct cred *cred)
249{
250 struct cred *nonconst_cred = (struct cred *) cred;
251 if (!cred)
252 return cred;
253 validate_creds(cred);
254 nonconst_cred->non_rcu = 0;
255 return get_new_cred(nonconst_cred);
256}
257
258static inline const struct cred *get_cred_rcu(const struct cred *cred)
259{
260 struct cred *nonconst_cred = (struct cred *) cred;
261 if (!cred)
262 return NULL;
263 if (!atomic_inc_not_zero(&nonconst_cred->usage))
264 return NULL;
265 validate_creds(cred);
266 nonconst_cred->non_rcu = 0;
267 return cred;
268}
269
270/**
271 * put_cred - Release a reference to a set of credentials
272 * @cred: The credentials to release
273 *
274 * Release a reference to a set of credentials, deleting them when the last ref
275 * is released. If %NULL is passed, nothing is done.
276 *
277 * This takes a const pointer to a set of credentials because the credentials
278 * on task_struct are attached by const pointers to prevent accidental
279 * alteration of otherwise immutable credential sets.
280 */
281static inline void put_cred(const struct cred *_cred)
282{
283 struct cred *cred = (struct cred *) _cred;
284
285 if (cred) {
286 validate_creds(cred);
287 if (atomic_dec_and_test(&(cred)->usage))
288 __put_cred(cred);
289 }
290}
291
292/**
293 * current_cred - Access the current task's subjective credentials
294 *
295 * Access the subjective credentials of the current task. RCU-safe,
296 * since nobody else can modify it.
297 */
298#define current_cred() \
299 rcu_dereference_protected(current->cred, 1)
300
301/**
302 * current_real_cred - Access the current task's objective credentials
303 *
304 * Access the objective credentials of the current task. RCU-safe,
305 * since nobody else can modify it.
306 */
307#define current_real_cred() \
308 rcu_dereference_protected(current->real_cred, 1)
309
310/**
311 * __task_cred - Access a task's objective credentials
312 * @task: The task to query
313 *
314 * Access the objective credentials of a task. The caller must hold the RCU
315 * readlock.
316 *
317 * The result of this function should not be passed directly to get_cred();
318 * rather get_task_cred() should be used instead.
319 */
320#define __task_cred(task) \
321 rcu_dereference((task)->real_cred)
322
323/**
324 * get_current_cred - Get the current task's subjective credentials
325 *
326 * Get the subjective credentials of the current task, pinning them so that
327 * they can't go away. Accessing the current task's credentials directly is
328 * not permitted.
329 */
330#define get_current_cred() \
331 (get_cred(current_cred()))
332
333/**
334 * get_current_user - Get the current task's user_struct
335 *
336 * Get the user record of the current task, pinning it so that it can't go
337 * away.
338 */
339#define get_current_user() \
340({ \
341 struct user_struct *__u; \
342 const struct cred *__cred; \
343 __cred = current_cred(); \
344 __u = get_uid(__cred->user); \
345 __u; \
346})
347
348/**
349 * get_current_groups - Get the current task's supplementary group list
350 *
351 * Get the supplementary group list of the current task, pinning it so that it
352 * can't go away.
353 */
354#define get_current_groups() \
355({ \
356 struct group_info *__groups; \
357 const struct cred *__cred; \
358 __cred = current_cred(); \
359 __groups = get_group_info(__cred->group_info); \
360 __groups; \
361})
362
363#define task_cred_xxx(task, xxx) \
364({ \
365 __typeof__(((struct cred *)NULL)->xxx) ___val; \
366 rcu_read_lock(); \
367 ___val = __task_cred((task))->xxx; \
368 rcu_read_unlock(); \
369 ___val; \
370})
371
372#define task_uid(task) (task_cred_xxx((task), uid))
373#define task_euid(task) (task_cred_xxx((task), euid))
374#define task_ucounts(task) (task_cred_xxx((task), ucounts))
375
376#define current_cred_xxx(xxx) \
377({ \
378 current_cred()->xxx; \
379})
380
381#define current_uid() (current_cred_xxx(uid))
382#define current_gid() (current_cred_xxx(gid))
383#define current_euid() (current_cred_xxx(euid))
384#define current_egid() (current_cred_xxx(egid))
385#define current_suid() (current_cred_xxx(suid))
386#define current_sgid() (current_cred_xxx(sgid))
387#define current_fsuid() (current_cred_xxx(fsuid))
388#define current_fsgid() (current_cred_xxx(fsgid))
389#define current_cap() (current_cred_xxx(cap_effective))
390#define current_user() (current_cred_xxx(user))
391#define current_ucounts() (current_cred_xxx(ucounts))
392
393extern struct user_namespace init_user_ns;
394#ifdef CONFIG_USER_NS
395#define current_user_ns() (current_cred_xxx(user_ns))
396#else
397static inline struct user_namespace *current_user_ns(void)
398{
399 return &init_user_ns;
400}
401#endif
402
403
404#define current_uid_gid(_uid, _gid) \
405do { \
406 const struct cred *__cred; \
407 __cred = current_cred(); \
408 *(_uid) = __cred->uid; \
409 *(_gid) = __cred->gid; \
410} while(0)
411
412#define current_euid_egid(_euid, _egid) \
413do { \
414 const struct cred *__cred; \
415 __cred = current_cred(); \
416 *(_euid) = __cred->euid; \
417 *(_egid) = __cred->egid; \
418} while(0)
419
420#define current_fsuid_fsgid(_fsuid, _fsgid) \
421do { \
422 const struct cred *__cred; \
423 __cred = current_cred(); \
424 *(_fsuid) = __cred->fsuid; \
425 *(_fsgid) = __cred->fsgid; \
426} while(0)
427
428#endif /* _LINUX_CRED_H */
429

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