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