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 */
get_group_info(struct group_info * gi)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
groups_free(struct group_info * group_info)70 static inline void groups_free(struct group_info *group_info)
71 {
72 }
73
in_group_p(kgid_t grp)74 static inline int in_group_p(kgid_t grp)
75 {
76 return 1;
77 }
in_egroup_p(kgid_t grp)78 static inline int in_egroup_p(kgid_t grp)
79 {
80 return 1;
81 }
groups_search(const struct group_info * group_info,kgid_t grp)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 struct cred *prepare_kernel_cred(struct task_struct *);
159 extern int set_security_override(struct cred *, u32);
160 extern int set_security_override_from_ctx(struct cred *, const char *);
161 extern int set_create_files_as(struct cred *, struct inode *);
162 extern int cred_fscmp(const struct cred *, const struct cred *);
163 extern void __init cred_init(void);
164 extern int set_cred_ucounts(struct cred *);
165
cap_ambient_invariant_ok(const struct cred * cred)166 static inline bool cap_ambient_invariant_ok(const struct cred *cred)
167 {
168 return cap_issubset(cred->cap_ambient,
169 cap_intersect(cred->cap_permitted,
170 cred->cap_inheritable));
171 }
172
override_creds(const struct cred * override_cred)173 static inline const struct cred *override_creds(const struct cred *override_cred)
174 {
175 return rcu_replace_pointer(current->cred, override_cred, 1);
176 }
177
revert_creds(const struct cred * revert_cred)178 static inline const struct cred *revert_creds(const struct cred *revert_cred)
179 {
180 return rcu_replace_pointer(current->cred, revert_cred, 1);
181 }
182
183 /**
184 * get_cred_many - Get references on a set of credentials
185 * @cred: The credentials to reference
186 * @nr: Number of references to acquire
187 *
188 * Get references on the specified set of credentials. The caller must release
189 * all acquired reference. If %NULL is passed, it is returned with no action.
190 *
191 * This is used to deal with a committed set of credentials. Although the
192 * pointer is const, this will temporarily discard the const and increment the
193 * usage count. The purpose of this is to attempt to catch at compile time the
194 * accidental alteration of a set of credentials that should be considered
195 * immutable.
196 */
get_cred_many(const struct cred * cred,int nr)197 static inline const struct cred *get_cred_many(const struct cred *cred, int nr)
198 {
199 struct cred *nonconst_cred = (struct cred *) cred;
200 if (!cred)
201 return cred;
202 nonconst_cred->non_rcu = 0;
203 atomic_long_add(nr, &nonconst_cred->usage);
204 return cred;
205 }
206
207 /*
208 * get_cred - Get a reference on a set of credentials
209 * @cred: The credentials to reference
210 *
211 * Get a reference on the specified set of credentials. The caller must
212 * release the reference. If %NULL is passed, it is returned with no action.
213 *
214 * This is used to deal with a committed set of credentials.
215 */
get_cred(const struct cred * cred)216 static inline const struct cred *get_cred(const struct cred *cred)
217 {
218 return get_cred_many(cred, 1);
219 }
220
get_cred_rcu(const struct cred * cred)221 static inline const struct cred *get_cred_rcu(const struct cred *cred)
222 {
223 struct cred *nonconst_cred = (struct cred *) cred;
224 if (!cred)
225 return NULL;
226 if (!atomic_long_inc_not_zero(&nonconst_cred->usage))
227 return NULL;
228 nonconst_cred->non_rcu = 0;
229 return cred;
230 }
231
232 /**
233 * put_cred - Release a reference to a set of credentials
234 * @cred: The credentials to release
235 * @nr: Number of references to release
236 *
237 * Release a reference to a set of credentials, deleting them when the last ref
238 * is released. If %NULL is passed, nothing is done.
239 *
240 * This takes a const pointer to a set of credentials because the credentials
241 * on task_struct are attached by const pointers to prevent accidental
242 * alteration of otherwise immutable credential sets.
243 */
put_cred_many(const struct cred * _cred,int nr)244 static inline void put_cred_many(const struct cred *_cred, int nr)
245 {
246 struct cred *cred = (struct cred *) _cred;
247
248 if (cred) {
249 if (atomic_long_sub_and_test(nr, &cred->usage))
250 __put_cred(cred);
251 }
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. If %NULL is passed, nothing is done.
260 */
put_cred(const struct cred * cred)261 static inline void put_cred(const struct cred *cred)
262 {
263 put_cred_many(cred, 1);
264 }
265
266 /**
267 * current_cred - Access the current task's subjective credentials
268 *
269 * Access the subjective credentials of the current task. RCU-safe,
270 * since nobody else can modify it.
271 */
272 #define current_cred() \
273 rcu_dereference_protected(current->cred, 1)
274
275 /**
276 * current_real_cred - Access the current task's objective credentials
277 *
278 * Access the objective credentials of the current task. RCU-safe,
279 * since nobody else can modify it.
280 */
281 #define current_real_cred() \
282 rcu_dereference_protected(current->real_cred, 1)
283
284 /**
285 * __task_cred - Access a task's objective credentials
286 * @task: The task to query
287 *
288 * Access the objective credentials of a task. The caller must hold the RCU
289 * readlock.
290 *
291 * The result of this function should not be passed directly to get_cred();
292 * rather get_task_cred() should be used instead.
293 */
294 #define __task_cred(task) \
295 rcu_dereference((task)->real_cred)
296
297 /**
298 * get_current_cred - Get the current task's subjective credentials
299 *
300 * Get the subjective credentials of the current task, pinning them so that
301 * they can't go away. Accessing the current task's credentials directly is
302 * not permitted.
303 */
304 #define get_current_cred() \
305 (get_cred(current_cred()))
306
307 /**
308 * get_current_user - Get the current task's user_struct
309 *
310 * Get the user record of the current task, pinning it so that it can't go
311 * away.
312 */
313 #define get_current_user() \
314 ({ \
315 struct user_struct *__u; \
316 const struct cred *__cred; \
317 __cred = current_cred(); \
318 __u = get_uid(__cred->user); \
319 __u; \
320 })
321
322 /**
323 * get_current_groups - Get the current task's supplementary group list
324 *
325 * Get the supplementary group list of the current task, pinning it so that it
326 * can't go away.
327 */
328 #define get_current_groups() \
329 ({ \
330 struct group_info *__groups; \
331 const struct cred *__cred; \
332 __cred = current_cred(); \
333 __groups = get_group_info(__cred->group_info); \
334 __groups; \
335 })
336
337 #define task_cred_xxx(task, xxx) \
338 ({ \
339 __typeof__(((struct cred *)NULL)->xxx) ___val; \
340 rcu_read_lock(); \
341 ___val = __task_cred((task))->xxx; \
342 rcu_read_unlock(); \
343 ___val; \
344 })
345
346 #define task_uid(task) (task_cred_xxx((task), uid))
347 #define task_euid(task) (task_cred_xxx((task), euid))
348 #define task_ucounts(task) (task_cred_xxx((task), ucounts))
349
350 #define current_cred_xxx(xxx) \
351 ({ \
352 current_cred()->xxx; \
353 })
354
355 #define current_uid() (current_cred_xxx(uid))
356 #define current_gid() (current_cred_xxx(gid))
357 #define current_euid() (current_cred_xxx(euid))
358 #define current_egid() (current_cred_xxx(egid))
359 #define current_suid() (current_cred_xxx(suid))
360 #define current_sgid() (current_cred_xxx(sgid))
361 #define current_fsuid() (current_cred_xxx(fsuid))
362 #define current_fsgid() (current_cred_xxx(fsgid))
363 #define current_cap() (current_cred_xxx(cap_effective))
364 #define current_user() (current_cred_xxx(user))
365 #define current_ucounts() (current_cred_xxx(ucounts))
366
367 extern struct user_namespace init_user_ns;
368 #ifdef CONFIG_USER_NS
369 #define current_user_ns() (current_cred_xxx(user_ns))
370 #else
current_user_ns(void)371 static inline struct user_namespace *current_user_ns(void)
372 {
373 return &init_user_ns;
374 }
375 #endif
376
377
378 #define current_uid_gid(_uid, _gid) \
379 do { \
380 const struct cred *__cred; \
381 __cred = current_cred(); \
382 *(_uid) = __cred->uid; \
383 *(_gid) = __cred->gid; \
384 } while(0)
385
386 #define current_euid_egid(_euid, _egid) \
387 do { \
388 const struct cred *__cred; \
389 __cred = current_cred(); \
390 *(_euid) = __cred->euid; \
391 *(_egid) = __cred->egid; \
392 } while(0)
393
394 #define current_fsuid_fsgid(_fsuid, _fsgid) \
395 do { \
396 const struct cred *__cred; \
397 __cred = current_cred(); \
398 *(_fsuid) = __cred->fsuid; \
399 *(_fsgid) = __cred->fsgid; \
400 } while(0)
401
402 #endif /* _LINUX_CRED_H */
403