1/* Credentials management - see Documentation/security/credentials.rst
2 *
3 * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved.
4 * Written by David Howells (dhowells@redhat.com)
5 *
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public Licence
8 * as published by the Free Software Foundation; either version
9 * 2 of the Licence, or (at your option) any later version.
10 */
11
12#ifndef _LINUX_CRED_H
13#define _LINUX_CRED_H
14
15#include <linux/capability.h>
16#include <linux/init.h>
17#include <linux/key.h>
18#include <linux/atomic.h>
19#include <linux/uidgid.h>
20#include <linux/sched.h>
21#include <linux/sched/user.h>
22
23struct cred;
24struct inode;
25
26/*
27 * COW Supplementary groups list
28 */
29struct group_info {
30 atomic_t usage;
31 int ngroups;
32 kgid_t gid[0];
33} __randomize_layout;
34
35/**
36 * get_group_info - Get a reference to a group info structure
37 * @group_info: The group info to reference
38 *
39 * This gets a reference to a set of supplementary groups.
40 *
41 * If the caller is accessing a task's credentials, they must hold the RCU read
42 * lock when reading.
43 */
44static inline struct group_info *get_group_info(struct group_info *gi)
45{
46 atomic_inc(&gi->usage);
47 return gi;
48}
49
50/**
51 * put_group_info - Release a reference to a group info structure
52 * @group_info: The group info to release
53 */
54#define put_group_info(group_info) \
55do { \
56 if (atomic_dec_and_test(&(group_info)->usage)) \
57 groups_free(group_info); \
58} while (0)
59
60extern struct group_info init_groups;
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_t usage;
117#ifdef CONFIG_DEBUG_CREDENTIALS
118 atomic_t subscribers; /* number of processes subscribed */
119 void *put_addr;
120 unsigned magic;
121#define CRED_MAGIC 0x43736564
122#define CRED_MAGIC_DEAD 0x44656144
123#endif
124 kuid_t uid; /* real UID of the task */
125 kgid_t gid; /* real GID of the task */
126 kuid_t suid; /* saved UID of the task */
127 kgid_t sgid; /* saved GID of the task */
128 kuid_t euid; /* effective UID of the task */
129 kgid_t egid; /* effective GID of the task */
130 kuid_t fsuid; /* UID for VFS ops */
131 kgid_t fsgid; /* GID for VFS ops */
132 unsigned securebits; /* SUID-less security management */
133 kernel_cap_t cap_inheritable; /* caps our children can inherit */
134 kernel_cap_t cap_permitted; /* caps we're permitted */
135 kernel_cap_t cap_effective; /* caps we can actually use */
136 kernel_cap_t cap_bset; /* capability bounding set */
137 kernel_cap_t cap_ambient; /* Ambient capability set */
138#ifdef CONFIG_KEYS
139 unsigned char jit_keyring; /* default keyring to attach requested
140 * keys to */
141 struct key __rcu *session_keyring; /* keyring inherited over fork */
142 struct key *process_keyring; /* keyring private to this process */
143 struct key *thread_keyring; /* keyring private to this thread */
144 struct key *request_key_auth; /* assumed request_key authority */
145#endif
146#ifdef CONFIG_SECURITY
147 void *security; /* subjective LSM security */
148#endif
149 struct user_struct *user; /* real user ID subscription */
150 struct user_namespace *user_ns; /* user_ns the caps and keyrings are relative to. */
151 struct group_info *group_info; /* supplementary groups for euid/fsgid */
152 struct rcu_head rcu; /* RCU deletion hook */
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);
173
174/*
175 * check for validity of credentials
176 */
177#ifdef CONFIG_DEBUG_CREDENTIALS
178extern void __invalid_creds(const struct cred *, const char *, unsigned);
179extern void __validate_process_creds(struct task_struct *,
180 const char *, unsigned);
181
182extern bool creds_are_invalid(const struct cred *cred);
183
184static inline void __validate_creds(const struct cred *cred,
185 const char *file, unsigned line)
186{
187 if (unlikely(creds_are_invalid(cred)))
188 __invalid_creds(cred, file, line);
189}
190
191#define validate_creds(cred) \
192do { \
193 __validate_creds((cred), __FILE__, __LINE__); \
194} while(0)
195
196#define validate_process_creds() \
197do { \
198 __validate_process_creds(current, __FILE__, __LINE__); \
199} while(0)
200
201extern void validate_creds_for_do_exit(struct task_struct *);
202#else
203static inline void validate_creds(const struct cred *cred)
204{
205}
206static inline void validate_creds_for_do_exit(struct task_struct *tsk)
207{
208}
209static inline void validate_process_creds(void)
210{
211}
212#endif
213
214static inline bool cap_ambient_invariant_ok(const struct cred *cred)
215{
216 return cap_issubset(cred->cap_ambient,
217 cap_intersect(cred->cap_permitted,
218 cred->cap_inheritable));
219}
220
221/**
222 * get_new_cred - Get a reference on a new set of credentials
223 * @cred: The new credentials to reference
224 *
225 * Get a reference on the specified set of new credentials. The caller must
226 * release the reference.
227 */
228static inline struct cred *get_new_cred(struct cred *cred)
229{
230 atomic_inc(&cred->usage);
231 return cred;
232}
233
234/**
235 * get_cred - Get a reference on a set of credentials
236 * @cred: The credentials to reference
237 *
238 * Get a reference on the specified set of credentials. The caller must
239 * release the reference. If %NULL is passed, it is returned with no action.
240 *
241 * This is used to deal with a committed set of credentials. Although the
242 * pointer is const, this will temporarily discard the const and increment the
243 * usage count. The purpose of this is to attempt to catch at compile time the
244 * accidental alteration of a set of credentials that should be considered
245 * immutable.
246 */
247static inline const struct cred *get_cred(const struct cred *cred)
248{
249 struct cred *nonconst_cred = (struct cred *) cred;
250 if (!cred)
251 return cred;
252 validate_creds(cred);
253 return get_new_cred(nonconst_cred);
254}
255
256static inline const struct cred *get_cred_rcu(const struct cred *cred)
257{
258 struct cred *nonconst_cred = (struct cred *) cred;
259 if (!cred)
260 return NULL;
261 if (!atomic_inc_not_zero(&nonconst_cred->usage))
262 return NULL;
263 validate_creds(cred);
264 return cred;
265}
266
267/**
268 * put_cred - Release a reference to a set of credentials
269 * @cred: The credentials to release
270 *
271 * Release a reference to a set of credentials, deleting them when the last ref
272 * is released. If %NULL is passed, nothing is done.
273 *
274 * This takes a const pointer to a set of credentials because the credentials
275 * on task_struct are attached by const pointers to prevent accidental
276 * alteration of otherwise immutable credential sets.
277 */
278static inline void put_cred(const struct cred *_cred)
279{
280 struct cred *cred = (struct cred *) _cred;
281
282 if (cred) {
283 validate_creds(cred);
284 if (atomic_dec_and_test(&(cred)->usage))
285 __put_cred(cred);
286 }
287}
288
289/**
290 * current_cred - Access the current task's subjective credentials
291 *
292 * Access the subjective credentials of the current task. RCU-safe,
293 * since nobody else can modify it.
294 */
295#define current_cred() \
296 rcu_dereference_protected(current->cred, 1)
297
298/**
299 * current_real_cred - Access the current task's objective credentials
300 *
301 * Access the objective credentials of the current task. RCU-safe,
302 * since nobody else can modify it.
303 */
304#define current_real_cred() \
305 rcu_dereference_protected(current->real_cred, 1)
306
307/**
308 * __task_cred - Access a task's objective credentials
309 * @task: The task to query
310 *
311 * Access the objective credentials of a task. The caller must hold the RCU
312 * readlock.
313 *
314 * The result of this function should not be passed directly to get_cred();
315 * rather get_task_cred() should be used instead.
316 */
317#define __task_cred(task) \
318 rcu_dereference((task)->real_cred)
319
320/**
321 * get_current_cred - Get the current task's subjective credentials
322 *
323 * Get the subjective credentials of the current task, pinning them so that
324 * they can't go away. Accessing the current task's credentials directly is
325 * not permitted.
326 */
327#define get_current_cred() \
328 (get_cred(current_cred()))
329
330/**
331 * get_current_user - Get the current task's user_struct
332 *
333 * Get the user record of the current task, pinning it so that it can't go
334 * away.
335 */
336#define get_current_user() \
337({ \
338 struct user_struct *__u; \
339 const struct cred *__cred; \
340 __cred = current_cred(); \
341 __u = get_uid(__cred->user); \
342 __u; \
343})
344
345/**
346 * get_current_groups - Get the current task's supplementary group list
347 *
348 * Get the supplementary group list of the current task, pinning it so that it
349 * can't go away.
350 */
351#define get_current_groups() \
352({ \
353 struct group_info *__groups; \
354 const struct cred *__cred; \
355 __cred = current_cred(); \
356 __groups = get_group_info(__cred->group_info); \
357 __groups; \
358})
359
360#define task_cred_xxx(task, xxx) \
361({ \
362 __typeof__(((struct cred *)NULL)->xxx) ___val; \
363 rcu_read_lock(); \
364 ___val = __task_cred((task))->xxx; \
365 rcu_read_unlock(); \
366 ___val; \
367})
368
369#define task_uid(task) (task_cred_xxx((task), uid))
370#define task_euid(task) (task_cred_xxx((task), euid))
371
372#define current_cred_xxx(xxx) \
373({ \
374 current_cred()->xxx; \
375})
376
377#define current_uid() (current_cred_xxx(uid))
378#define current_gid() (current_cred_xxx(gid))
379#define current_euid() (current_cred_xxx(euid))
380#define current_egid() (current_cred_xxx(egid))
381#define current_suid() (current_cred_xxx(suid))
382#define current_sgid() (current_cred_xxx(sgid))
383#define current_fsuid() (current_cred_xxx(fsuid))
384#define current_fsgid() (current_cred_xxx(fsgid))
385#define current_cap() (current_cred_xxx(cap_effective))
386#define current_user() (current_cred_xxx(user))
387#define current_security() (current_cred_xxx(security))
388
389extern struct user_namespace init_user_ns;
390#ifdef CONFIG_USER_NS
391#define current_user_ns() (current_cred_xxx(user_ns))
392#else
393static inline struct user_namespace *current_user_ns(void)
394{
395 return &init_user_ns;
396}
397#endif
398
399
400#define current_uid_gid(_uid, _gid) \
401do { \
402 const struct cred *__cred; \
403 __cred = current_cred(); \
404 *(_uid) = __cred->uid; \
405 *(_gid) = __cred->gid; \
406} while(0)
407
408#define current_euid_egid(_euid, _egid) \
409do { \
410 const struct cred *__cred; \
411 __cred = current_cred(); \
412 *(_euid) = __cred->euid; \
413 *(_egid) = __cred->egid; \
414} while(0)
415
416#define current_fsuid_fsgid(_fsuid, _fsgid) \
417do { \
418 const struct cred *__cred; \
419 __cred = current_cred(); \
420 *(_fsuid) = __cred->fsuid; \
421 *(_fsgid) = __cred->fsgid; \
422} while(0)
423
424#endif /* _LINUX_CRED_H */
425