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 extern struct task_struct init_task;
24
25 /*
26 * COW Supplementary groups list
27 */
28 struct 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 * @gi: 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 *
43 * Returns: @gi
44 */
get_group_info(struct group_info * gi)45 static inline struct group_info *get_group_info(struct group_info *gi)
46 {
47 refcount_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) \
56 do { \
57 if (refcount_dec_and_test(&(group_info)->usage)) \
58 groups_free(group_info); \
59 } while (0)
60
61 #ifdef CONFIG_MULTIUSER
62 extern struct group_info *groups_alloc(int);
63 extern void groups_free(struct group_info *);
64
65 extern int in_group_p(kgid_t);
66 extern int in_egroup_p(kgid_t);
67 extern int groups_search(const struct group_info *, kgid_t);
68
69 extern int set_current_groups(struct group_info *);
70 extern void set_groups(struct cred *, struct group_info *);
71 extern bool may_setgroups(void);
72 extern void groups_sort(struct group_info *);
73 #else
groups_free(struct group_info * group_info)74 static inline void groups_free(struct group_info *group_info)
75 {
76 }
77
in_group_p(kgid_t grp)78 static inline int in_group_p(kgid_t grp)
79 {
80 return 1;
81 }
in_egroup_p(kgid_t grp)82 static inline int in_egroup_p(kgid_t grp)
83 {
84 return 1;
85 }
groups_search(const struct group_info * group_info,kgid_t grp)86 static 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 */
115 struct cred {
116 atomic_long_t usage;
117 kuid_t uid; /* real UID of the task */
118 kgid_t gid; /* real GID of the task */
119 kuid_t suid; /* saved UID of the task */
120 kgid_t sgid; /* saved GID of the task */
121 kuid_t euid; /* effective UID of the task */
122 kgid_t egid; /* effective GID of the task */
123 kuid_t fsuid; /* UID for VFS ops */
124 kgid_t fsgid; /* GID for VFS ops */
125 unsigned securebits; /* SUID-less security management */
126 kernel_cap_t cap_inheritable; /* caps our children can inherit */
127 kernel_cap_t cap_permitted; /* caps we're permitted */
128 kernel_cap_t cap_effective; /* caps we can actually use */
129 kernel_cap_t cap_bset; /* capability bounding set */
130 kernel_cap_t cap_ambient; /* Ambient capability set */
131 #ifdef CONFIG_KEYS
132 unsigned char jit_keyring; /* default keyring to attach requested
133 * keys to */
134 struct key *session_keyring; /* keyring inherited over fork */
135 struct key *process_keyring; /* keyring private to this process */
136 struct key *thread_keyring; /* keyring private to this thread */
137 struct key *request_key_auth; /* assumed request_key authority */
138 #endif
139 #ifdef CONFIG_SECURITY
140 void *security; /* LSM security */
141 #endif
142 struct user_struct *user; /* real user ID subscription */
143 struct user_namespace *user_ns; /* user_ns the caps and keyrings are relative to. */
144 struct ucounts *ucounts;
145 struct group_info *group_info; /* supplementary groups for euid/fsgid */
146 /* RCU deletion */
147 union {
148 int non_rcu; /* Can we skip RCU deletion? */
149 struct rcu_head rcu; /* RCU deletion hook */
150 };
151 } __randomize_layout;
152
153 extern void __put_cred(struct cred *);
154 extern void exit_creds(struct task_struct *);
155 extern int copy_creds(struct task_struct *, u64);
156 extern const struct cred *get_task_cred(struct task_struct *);
157 extern struct cred *cred_alloc_blank(void);
158 extern struct cred *prepare_creds(void);
159 extern struct cred *prepare_exec_creds(void);
160 extern int commit_creds(struct cred *);
161 extern void abort_creds(struct cred *);
162 extern struct cred *prepare_kernel_cred(struct task_struct *);
kernel_cred(void)163 static inline const struct cred *kernel_cred(void)
164 {
165 /* shut up sparse */
166 return rcu_dereference_raw(init_task.cred);
167 }
168 extern int set_security_override(struct cred *, u32);
169 extern int set_create_files_as(struct cred *, struct inode *);
170 extern int cred_fscmp(const struct cred *, const struct cred *);
171 extern void __init cred_init(void);
172 extern int set_cred_ucounts(struct cred *);
173
cap_ambient_invariant_ok(const struct cred * cred)174 static inline bool cap_ambient_invariant_ok(const struct cred *cred)
175 {
176 return cap_issubset(cred->cap_ambient,
177 cap_intersect(cred->cap_permitted,
178 cred->cap_inheritable));
179 }
180
override_creds(const struct cred * override_cred)181 static inline const struct cred *override_creds(const struct cred *override_cred)
182 {
183 return rcu_replace_pointer(current->cred, override_cred, 1);
184 }
185
revert_creds(const struct cred * revert_cred)186 static inline const struct cred *revert_creds(const struct cred *revert_cred)
187 {
188 return rcu_replace_pointer(current->cred, revert_cred, 1);
189 }
190
DEFINE_CLASS(override_creds,const struct cred *,revert_creds (_T),override_creds (override_cred),const struct cred * override_cred)191 DEFINE_CLASS(override_creds,
192 const struct cred *,
193 revert_creds(_T),
194 override_creds(override_cred), const struct cred *override_cred)
195
196 #define scoped_with_creds(cred) \
197 scoped_class(override_creds, __UNIQUE_ID(label), cred)
198
199 #define scoped_with_kernel_creds() scoped_with_creds(kernel_cred())
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 * Returns: @cred when the references are acquired, NULL otherwise.
216 */
217 static inline const struct cred *get_cred_many(const struct cred *cred, int nr)
218 {
219 struct cred *nonconst_cred = (struct cred *) cred;
220 if (!cred)
221 return cred;
222 nonconst_cred->non_rcu = 0;
223 atomic_long_add(nr, &nonconst_cred->usage);
224 return cred;
225 }
226
227 /*
228 * get_cred - Get a reference on a set of credentials
229 * @cred: The credentials to reference
230 *
231 * Get a reference on the specified set of credentials. The caller must
232 * release the reference. If %NULL is passed, it is returned with no action.
233 *
234 * This is used to deal with a committed set of credentials.
235 */
get_cred(const struct cred * cred)236 static inline const struct cred *get_cred(const struct cred *cred)
237 {
238 return get_cred_many(cred, 1);
239 }
240
get_cred_rcu(const struct cred * cred)241 static inline const struct cred *get_cred_rcu(const struct cred *cred)
242 {
243 struct cred *nonconst_cred = (struct cred *) cred;
244 if (!cred)
245 return NULL;
246 if (!atomic_long_inc_not_zero(&nonconst_cred->usage))
247 return NULL;
248 nonconst_cred->non_rcu = 0;
249 return cred;
250 }
251
252 /**
253 * put_cred_many - Release a reference to a set of credentials
254 * @_cred: The credentials to release
255 * @nr: Number of references to release
256 *
257 * Release a reference to a set of credentials, deleting them when the last ref
258 * is released. If %NULL is passed, nothing is done.
259 *
260 * This takes a const pointer to a set of credentials because the credentials
261 * on task_struct are attached by const pointers to prevent accidental
262 * alteration of otherwise immutable credential sets.
263 */
put_cred_many(const struct cred * _cred,int nr)264 static inline void put_cred_many(const struct cred *_cred, int nr)
265 {
266 struct cred *cred = (struct cred *) _cred;
267
268 if (cred) {
269 if (atomic_long_sub_and_test(nr, &cred->usage))
270 __put_cred(cred);
271 }
272 }
273
274 /*
275 * put_cred - Release a reference to a set of credentials
276 * @cred: The credentials to release
277 *
278 * Release a reference to a set of credentials, deleting them when the last ref
279 * is released. If %NULL is passed, nothing is done.
280 */
put_cred(const struct cred * cred)281 static inline void put_cred(const struct cred *cred)
282 {
283 put_cred_many(cred, 1);
284 }
285
286 DEFINE_CLASS(prepare_creds,
287 struct cred *,
288 if (_T) put_cred(_T),
289 prepare_creds(), void)
290
291 DEFINE_FREE(put_cred, struct cred *, if (!IS_ERR_OR_NULL(_T)) put_cred(_T))
292
293 /**
294 * current_cred - Access the current task's subjective credentials
295 *
296 * Access the subjective credentials of the current task. RCU-safe,
297 * since nobody else can modify it.
298 */
299 #define current_cred() \
300 rcu_dereference_protected(current->cred, 1)
301
302 /**
303 * current_real_cred - Access the current task's objective credentials
304 *
305 * Access the objective credentials of the current task. RCU-safe,
306 * since nobody else can modify it.
307 */
308 #define current_real_cred() \
309 rcu_dereference_protected(current->real_cred, 1)
310
311 /**
312 * __task_cred - Access a task's objective credentials
313 * @task: The task to query
314 *
315 * Access the objective credentials of a task. The caller must hold the RCU
316 * readlock.
317 *
318 * The result of this function should not be passed directly to get_cred();
319 * rather get_task_cred() should be used instead.
320 */
321 #define __task_cred(task) \
322 rcu_dereference((task)->real_cred)
323
324 /**
325 * get_current_cred - Get the current task's subjective credentials
326 *
327 * Get the subjective credentials of the current task, pinning them so that
328 * they can't go away. Accessing the current task's credentials directly is
329 * not permitted.
330 */
331 #define get_current_cred() \
332 (get_cred(current_cred()))
333
334 /**
335 * get_current_user - Get the current task's user_struct
336 *
337 * Get the user record of the current task, pinning it so that it can't go
338 * away.
339 */
340 #define get_current_user() \
341 ({ \
342 struct user_struct *__u; \
343 const struct cred *__cred; \
344 __cred = current_cred(); \
345 __u = get_uid(__cred->user); \
346 __u; \
347 })
348
349 /**
350 * get_current_groups - Get the current task's supplementary group list
351 *
352 * Get the supplementary group list of the current task, pinning it so that it
353 * can't go away.
354 */
355 #define get_current_groups() \
356 ({ \
357 struct group_info *__groups; \
358 const struct cred *__cred; \
359 __cred = current_cred(); \
360 __groups = get_group_info(__cred->group_info); \
361 __groups; \
362 })
363
364 #define task_cred_xxx(task, xxx) \
365 ({ \
366 __typeof__(((struct cred *)NULL)->xxx) ___val; \
367 rcu_read_lock(); \
368 ___val = __task_cred((task))->xxx; \
369 rcu_read_unlock(); \
370 ___val; \
371 })
372
373 #define task_uid(task) (task_cred_xxx((task), uid))
374 #define task_euid(task) (task_cred_xxx((task), euid))
375 #define task_ucounts(task) (task_cred_xxx((task), ucounts))
376
377 #define current_cred_xxx(xxx) \
378 ({ \
379 current_cred()->xxx; \
380 })
381
382 #define current_uid() (current_cred_xxx(uid))
383 #define current_gid() (current_cred_xxx(gid))
384 #define current_euid() (current_cred_xxx(euid))
385 #define current_egid() (current_cred_xxx(egid))
386 #define current_suid() (current_cred_xxx(suid))
387 #define current_sgid() (current_cred_xxx(sgid))
388 #define current_fsuid() (current_cred_xxx(fsuid))
389 #define current_fsgid() (current_cred_xxx(fsgid))
390 #define current_cap() (current_cred_xxx(cap_effective))
391 #define current_user() (current_cred_xxx(user))
392 #define current_ucounts() (current_cred_xxx(ucounts))
393
394 extern struct user_namespace init_user_ns;
395 #ifdef CONFIG_USER_NS
396 #define current_user_ns() (current_cred_xxx(user_ns))
397 #else
current_user_ns(void)398 static inline struct user_namespace *current_user_ns(void)
399 {
400 return &init_user_ns;
401 }
402 #endif
403
404
405 #define current_uid_gid(_uid, _gid) \
406 do { \
407 const struct cred *__cred; \
408 __cred = current_cred(); \
409 *(_uid) = __cred->uid; \
410 *(_gid) = __cred->gid; \
411 } while(0)
412
413 #define current_euid_egid(_euid, _egid) \
414 do { \
415 const struct cred *__cred; \
416 __cred = current_cred(); \
417 *(_euid) = __cred->euid; \
418 *(_egid) = __cred->egid; \
419 } while(0)
420
421 #define current_fsuid_fsgid(_fsuid, _fsgid) \
422 do { \
423 const struct cred *__cred; \
424 __cred = current_cred(); \
425 *(_fsuid) = __cred->fsuid; \
426 *(_fsgid) = __cred->fsgid; \
427 } while(0)
428
429 #endif /* _LINUX_CRED_H */
430