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/selinux.h>
19#include <linux/atomic.h>
20#include <linux/uidgid.h>
21#include <linux/sched.h>
22#include <linux/sched/user.h>
23
24struct cred;
25struct inode;
26
27/*
28 * COW Supplementary groups list
29 */
30struct group_info {
31 atomic_t usage;
32 int ngroups;
33 kgid_t gid[0];
34} __randomize_layout;
35
36/**
37 * get_group_info - Get a reference to a group info structure
38 * @group_info: The group info to reference
39 *
40 * This gets a reference to a set of supplementary groups.
41 *
42 * If the caller is accessing a task's credentials, they must hold the RCU read
43 * lock when reading.
44 */
45static inline struct group_info *get_group_info(struct group_info *gi)
46{
47 atomic_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 (atomic_dec_and_test(&(group_info)->usage)) \
58 groups_free(group_info); \
59} while (0)
60
61extern struct group_info init_groups;
62#ifdef CONFIG_MULTIUSER
63extern struct group_info *groups_alloc(int);
64extern void groups_free(struct group_info *);
65
66extern int in_group_p(kgid_t);
67extern int in_egroup_p(kgid_t);
68extern int groups_search(const struct group_info *, kgid_t);
69
70extern int set_current_groups(struct group_info *);
71extern void set_groups(struct cred *, struct group_info *);
72extern bool may_setgroups(void);
73extern void groups_sort(struct group_info *);
74#else
75static inline void groups_free(struct group_info *group_info)
76{
77}
78
79static inline int in_group_p(kgid_t grp)
80{
81 return 1;
82}
83static inline int in_egroup_p(kgid_t grp)
84{
85 return 1;
86}
87static inline int groups_search(const struct group_info *group_info, kgid_t grp)
88{
89 return 1;
90}
91#endif
92
93/*
94 * The security context of a task
95 *
96 * The parts of the context break down into two categories:
97 *
98 * (1) The objective context of a task. These parts are used when some other
99 * task is attempting to affect this one.
100 *
101 * (2) The subjective context. These details are used when the task is acting
102 * upon another object, be that a file, a task, a key or whatever.
103 *
104 * Note that some members of this structure belong to both categories - the
105 * LSM security pointer for instance.
106 *
107 * A task has two security pointers. task->real_cred points to the objective
108 * context that defines that task's actual details. The objective part of this
109 * context is used whenever that task is acted upon.
110 *
111 * task->cred points to the subjective context that defines the details of how
112 * that task is going to act upon another object. This may be overridden
113 * temporarily to point to another security context, but normally points to the
114 * same context as task->real_cred.
115 */
116struct cred {
117 atomic_t usage;
118#ifdef CONFIG_DEBUG_CREDENTIALS
119 atomic_t subscribers; /* number of processes subscribed */
120 void *put_addr;
121 unsigned magic;
122#define CRED_MAGIC 0x43736564
123#define CRED_MAGIC_DEAD 0x44656144
124#endif
125 kuid_t uid; /* real UID of the task */
126 kgid_t gid; /* real GID of the task */
127 kuid_t suid; /* saved UID of the task */
128 kgid_t sgid; /* saved GID of the task */
129 kuid_t euid; /* effective UID of the task */
130 kgid_t egid; /* effective GID of the task */
131 kuid_t fsuid; /* UID for VFS ops */
132 kgid_t fsgid; /* GID for VFS ops */
133 unsigned securebits; /* SUID-less security management */
134 kernel_cap_t cap_inheritable; /* caps our children can inherit */
135 kernel_cap_t cap_permitted; /* caps we're permitted */
136 kernel_cap_t cap_effective; /* caps we can actually use */
137 kernel_cap_t cap_bset; /* capability bounding set */
138 kernel_cap_t cap_ambient; /* Ambient capability set */
139#ifdef CONFIG_KEYS
140 unsigned char jit_keyring; /* default keyring to attach requested
141 * keys to */
142 struct key __rcu *session_keyring; /* keyring inherited over fork */
143 struct key *process_keyring; /* keyring private to this process */
144 struct key *thread_keyring; /* keyring private to this thread */
145 struct key *request_key_auth; /* assumed request_key authority */
146#endif
147#ifdef CONFIG_SECURITY
148 void *security; /* subjective LSM security */
149#endif
150 struct user_struct *user; /* real user ID subscription */
151 struct user_namespace *user_ns; /* user_ns the caps and keyrings are relative to. */
152 struct group_info *group_info; /* supplementary groups for euid/fsgid */
153 struct rcu_head rcu; /* RCU deletion hook */
154} __randomize_layout;
155
156extern void __put_cred(struct cred *);
157extern void exit_creds(struct task_struct *);
158extern int copy_creds(struct task_struct *, unsigned long);
159extern const struct cred *get_task_cred(struct task_struct *);
160extern struct cred *cred_alloc_blank(void);
161extern struct cred *prepare_creds(void);
162extern struct cred *prepare_exec_creds(void);
163extern int commit_creds(struct cred *);
164extern void abort_creds(struct cred *);
165extern const struct cred *override_creds(const struct cred *);
166extern void revert_creds(const struct cred *);
167extern struct cred *prepare_kernel_cred(struct task_struct *);
168extern int change_create_files_as(struct cred *, struct inode *);
169extern int set_security_override(struct cred *, u32);
170extern int set_security_override_from_ctx(struct cred *, const char *);
171extern int set_create_files_as(struct cred *, struct inode *);
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.
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 validate_creds(cred);
251 return get_new_cred(nonconst_cred);
252}
253
254/**
255 * put_cred - Release a reference to a set of credentials
256 * @cred: The credentials to release
257 *
258 * Release a reference to a set of credentials, deleting them when the last ref
259 * is released.
260 *
261 * This takes a const pointer to a set of credentials because the credentials
262 * on task_struct are attached by const pointers to prevent accidental
263 * alteration of otherwise immutable credential sets.
264 */
265static inline void put_cred(const struct cred *_cred)
266{
267 struct cred *cred = (struct cred *) _cred;
268
269 validate_creds(cred);
270 if (atomic_dec_and_test(&(cred)->usage))
271 __put_cred(cred);
272}
273
274/**
275 * current_cred - Access the current task's subjective credentials
276 *
277 * Access the subjective credentials of the current task. RCU-safe,
278 * since nobody else can modify it.
279 */
280#define current_cred() \
281 rcu_dereference_protected(current->cred, 1)
282
283/**
284 * current_real_cred - Access the current task's objective credentials
285 *
286 * Access the objective credentials of the current task. RCU-safe,
287 * since nobody else can modify it.
288 */
289#define current_real_cred() \
290 rcu_dereference_protected(current->real_cred, 1)
291
292/**
293 * __task_cred - Access a task's objective credentials
294 * @task: The task to query
295 *
296 * Access the objective credentials of a task. The caller must hold the RCU
297 * readlock.
298 *
299 * The result of this function should not be passed directly to get_cred();
300 * rather get_task_cred() should be used instead.
301 */
302#define __task_cred(task) \
303 rcu_dereference((task)->real_cred)
304
305/**
306 * get_current_cred - Get the current task's subjective credentials
307 *
308 * Get the subjective credentials of the current task, pinning them so that
309 * they can't go away. Accessing the current task's credentials directly is
310 * not permitted.
311 */
312#define get_current_cred() \
313 (get_cred(current_cred()))
314
315/**
316 * get_current_user - Get the current task's user_struct
317 *
318 * Get the user record of the current task, pinning it so that it can't go
319 * away.
320 */
321#define get_current_user() \
322({ \
323 struct user_struct *__u; \
324 const struct cred *__cred; \
325 __cred = current_cred(); \
326 __u = get_uid(__cred->user); \
327 __u; \
328})
329
330/**
331 * get_current_groups - Get the current task's supplementary group list
332 *
333 * Get the supplementary group list of the current task, pinning it so that it
334 * can't go away.
335 */
336#define get_current_groups() \
337({ \
338 struct group_info *__groups; \
339 const struct cred *__cred; \
340 __cred = current_cred(); \
341 __groups = get_group_info(__cred->group_info); \
342 __groups; \
343})
344
345#define task_cred_xxx(task, xxx) \
346({ \
347 __typeof__(((struct cred *)NULL)->xxx) ___val; \
348 rcu_read_lock(); \
349 ___val = __task_cred((task))->xxx; \
350 rcu_read_unlock(); \
351 ___val; \
352})
353
354#define task_uid(task) (task_cred_xxx((task), uid))
355#define task_euid(task) (task_cred_xxx((task), euid))
356
357#define current_cred_xxx(xxx) \
358({ \
359 current_cred()->xxx; \
360})
361
362#define current_uid() (current_cred_xxx(uid))
363#define current_gid() (current_cred_xxx(gid))
364#define current_euid() (current_cred_xxx(euid))
365#define current_egid() (current_cred_xxx(egid))
366#define current_suid() (current_cred_xxx(suid))
367#define current_sgid() (current_cred_xxx(sgid))
368#define current_fsuid() (current_cred_xxx(fsuid))
369#define current_fsgid() (current_cred_xxx(fsgid))
370#define current_cap() (current_cred_xxx(cap_effective))
371#define current_user() (current_cred_xxx(user))
372#define current_security() (current_cred_xxx(security))
373
374extern struct user_namespace init_user_ns;
375#ifdef CONFIG_USER_NS
376#define current_user_ns() (current_cred_xxx(user_ns))
377#else
378static inline struct user_namespace *current_user_ns(void)
379{
380 return &init_user_ns;
381}
382#endif
383
384
385#define current_uid_gid(_uid, _gid) \
386do { \
387 const struct cred *__cred; \
388 __cred = current_cred(); \
389 *(_uid) = __cred->uid; \
390 *(_gid) = __cred->gid; \
391} while(0)
392
393#define current_euid_egid(_euid, _egid) \
394do { \
395 const struct cred *__cred; \
396 __cred = current_cred(); \
397 *(_euid) = __cred->euid; \
398 *(_egid) = __cred->egid; \
399} while(0)
400
401#define current_fsuid_fsgid(_fsuid, _fsgid) \
402do { \
403 const struct cred *__cred; \
404 __cred = current_cred(); \
405 *(_fsuid) = __cred->fsuid; \
406 *(_fsgid) = __cred->fsgid; \
407} while(0)
408
409#endif /* _LINUX_CRED_H */
410