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/uidgid.h>
16 #include <linux/sched.h>
17 #include <linux/sched/user.h>
18
19 struct cred;
20 struct inode;
21
22 /*
23 * COW Supplementary groups list
24 */
25 struct group_info {
26 atomic_t usage;
27 int ngroups;
28 kgid_t gid[];
29 } __randomize_layout;
30
31 /**
32 * get_group_info - Get a reference to a group info structure
33 * @group_info: The group info to reference
34 *
35 * This gets a reference to a set of supplementary groups.
36 *
37 * If the caller is accessing a task's credentials, they must hold the RCU read
38 * lock when reading.
39 */
get_group_info(struct group_info * gi)40 static inline struct group_info *get_group_info(struct group_info *gi)
41 {
42 atomic_inc(&gi->usage);
43 return gi;
44 }
45
46 /**
47 * put_group_info - Release a reference to a group info structure
48 * @group_info: The group info to release
49 */
50 #define put_group_info(group_info) \
51 do { \
52 if (atomic_dec_and_test(&(group_info)->usage)) \
53 groups_free(group_info); \
54 } while (0)
55
56 #ifdef CONFIG_MULTIUSER
57 extern struct group_info *groups_alloc(int);
58 extern void groups_free(struct group_info *);
59
60 extern int in_group_p(kgid_t);
61 extern int in_egroup_p(kgid_t);
62 extern int groups_search(const struct group_info *, kgid_t);
63
64 extern int set_current_groups(struct group_info *);
65 extern void set_groups(struct cred *, struct group_info *);
66 extern bool may_setgroups(void);
67 extern void groups_sort(struct group_info *);
68 #else
groups_free(struct group_info * group_info)69 static inline void groups_free(struct group_info *group_info)
70 {
71 }
72
in_group_p(kgid_t grp)73 static inline int in_group_p(kgid_t grp)
74 {
75 return 1;
76 }
in_egroup_p(kgid_t grp)77 static inline int in_egroup_p(kgid_t grp)
78 {
79 return 1;
80 }
groups_search(const struct group_info * group_info,kgid_t grp)81 static inline int groups_search(const struct group_info *group_info, kgid_t grp)
82 {
83 return 1;
84 }
85 #endif
86
87 /*
88 * The security context of a task
89 *
90 * The parts of the context break down into two categories:
91 *
92 * (1) The objective context of a task. These parts are used when some other
93 * task is attempting to affect this one.
94 *
95 * (2) The subjective context. These details are used when the task is acting
96 * upon another object, be that a file, a task, a key or whatever.
97 *
98 * Note that some members of this structure belong to both categories - the
99 * LSM security pointer for instance.
100 *
101 * A task has two security pointers. task->real_cred points to the objective
102 * context that defines that task's actual details. The objective part of this
103 * context is used whenever that task is acted upon.
104 *
105 * task->cred points to the subjective context that defines the details of how
106 * that task is going to act upon another object. This may be overridden
107 * temporarily to point to another security context, but normally points to the
108 * same context as task->real_cred.
109 */
110 struct cred {
111 atomic_t usage;
112 #ifdef CONFIG_DEBUG_CREDENTIALS
113 atomic_t subscribers; /* number of processes subscribed */
114 void *put_addr;
115 unsigned magic;
116 #define CRED_MAGIC 0x43736564
117 #define CRED_MAGIC_DEAD 0x44656144
118 #endif
119 kuid_t uid; /* real UID of the task */
120 kgid_t gid; /* real GID of the task */
121 kuid_t suid; /* saved UID of the task */
122 kgid_t sgid; /* saved GID of the task */
123 kuid_t euid; /* effective UID of the task */
124 kgid_t egid; /* effective GID of the task */
125 kuid_t fsuid; /* UID for VFS ops */
126 kgid_t fsgid; /* GID for VFS ops */
127 unsigned securebits; /* SUID-less security management */
128 kernel_cap_t cap_inheritable; /* caps our children can inherit */
129 kernel_cap_t cap_permitted; /* caps we're permitted */
130 kernel_cap_t cap_effective; /* caps we can actually use */
131 kernel_cap_t cap_bset; /* capability bounding set */
132 kernel_cap_t cap_ambient; /* Ambient capability set */
133 #ifdef CONFIG_KEYS
134 unsigned char jit_keyring; /* default keyring to attach requested
135 * keys to */
136 struct key *session_keyring; /* keyring inherited over fork */
137 struct key *process_keyring; /* keyring private to this process */
138 struct key *thread_keyring; /* keyring private to this thread */
139 struct key *request_key_auth; /* assumed request_key authority */
140 #endif
141 #ifdef CONFIG_SECURITY
142 void *security; /* LSM security */
143 #endif
144 struct user_struct *user; /* real user ID subscription */
145 struct user_namespace *user_ns; /* user_ns the caps and keyrings are relative to. */
146 struct group_info *group_info; /* supplementary groups for euid/fsgid */
147 /* RCU deletion */
148 union {
149 int non_rcu; /* Can we skip RCU deletion? */
150 struct rcu_head rcu; /* RCU deletion hook */
151 };
152 } __randomize_layout;
153
154 extern void __put_cred(struct cred *);
155 extern void exit_creds(struct task_struct *);
156 extern int copy_creds(struct task_struct *, unsigned long);
157 extern const struct cred *get_task_cred(struct task_struct *);
158 extern struct cred *cred_alloc_blank(void);
159 extern struct cred *prepare_creds(void);
160 extern struct cred *prepare_exec_creds(void);
161 extern int commit_creds(struct cred *);
162 extern void abort_creds(struct cred *);
163 extern const struct cred *override_creds(const struct cred *);
164 extern void revert_creds(const struct cred *);
165 extern struct cred *prepare_kernel_cred(struct task_struct *);
166 extern int change_create_files_as(struct cred *, struct inode *);
167 extern int set_security_override(struct cred *, u32);
168 extern int set_security_override_from_ctx(struct cred *, const char *);
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
173 /*
174 * check for validity of credentials
175 */
176 #ifdef CONFIG_DEBUG_CREDENTIALS
177 extern void __invalid_creds(const struct cred *, const char *, unsigned);
178 extern void __validate_process_creds(struct task_struct *,
179 const char *, unsigned);
180
181 extern bool creds_are_invalid(const struct cred *cred);
182
__validate_creds(const struct cred * cred,const char * file,unsigned line)183 static inline void __validate_creds(const struct cred *cred,
184 const char *file, unsigned line)
185 {
186 if (unlikely(creds_are_invalid(cred)))
187 __invalid_creds(cred, file, line);
188 }
189
190 #define validate_creds(cred) \
191 do { \
192 __validate_creds((cred), __FILE__, __LINE__); \
193 } while(0)
194
195 #define validate_process_creds() \
196 do { \
197 __validate_process_creds(current, __FILE__, __LINE__); \
198 } while(0)
199
200 extern void validate_creds_for_do_exit(struct task_struct *);
201 #else
validate_creds(const struct cred * cred)202 static inline void validate_creds(const struct cred *cred)
203 {
204 }
validate_creds_for_do_exit(struct task_struct * tsk)205 static inline void validate_creds_for_do_exit(struct task_struct *tsk)
206 {
207 }
validate_process_creds(void)208 static inline void validate_process_creds(void)
209 {
210 }
211 #endif
212
cap_ambient_invariant_ok(const struct cred * cred)213 static inline bool cap_ambient_invariant_ok(const struct cred *cred)
214 {
215 return cap_issubset(cred->cap_ambient,
216 cap_intersect(cred->cap_permitted,
217 cred->cap_inheritable));
218 }
219
220 /**
221 * get_new_cred - Get a reference on a new set of credentials
222 * @cred: The new credentials to reference
223 *
224 * Get a reference on the specified set of new credentials. The caller must
225 * release the reference.
226 */
get_new_cred(struct cred * cred)227 static inline struct cred *get_new_cred(struct cred *cred)
228 {
229 atomic_inc(&cred->usage);
230 return cred;
231 }
232
233 /**
234 * get_cred - Get a reference on a set of credentials
235 * @cred: The credentials to reference
236 *
237 * Get a reference on the specified set of credentials. The caller must
238 * release the reference. If %NULL is passed, it is returned with no action.
239 *
240 * This is used to deal with a committed set of credentials. Although the
241 * pointer is const, this will temporarily discard the const and increment the
242 * usage count. The purpose of this is to attempt to catch at compile time the
243 * accidental alteration of a set of credentials that should be considered
244 * immutable.
245 */
get_cred(const struct cred * cred)246 static inline const struct cred *get_cred(const struct cred *cred)
247 {
248 struct cred *nonconst_cred = (struct cred *) cred;
249 if (!cred)
250 return cred;
251 validate_creds(cred);
252 nonconst_cred->non_rcu = 0;
253 return get_new_cred(nonconst_cred);
254 }
255
get_cred_rcu(const struct cred * cred)256 static 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 nonconst_cred->non_rcu = 0;
265 return cred;
266 }
267
268 /**
269 * put_cred - Release a reference to a set of credentials
270 * @cred: The credentials to release
271 *
272 * Release a reference to a set of credentials, deleting them when the last ref
273 * is released. If %NULL is passed, nothing is done.
274 *
275 * This takes a const pointer to a set of credentials because the credentials
276 * on task_struct are attached by const pointers to prevent accidental
277 * alteration of otherwise immutable credential sets.
278 */
put_cred(const struct cred * _cred)279 static inline void put_cred(const struct cred *_cred)
280 {
281 struct cred *cred = (struct cred *) _cred;
282
283 if (cred) {
284 validate_creds(cred);
285 if (atomic_dec_and_test(&(cred)->usage))
286 __put_cred(cred);
287 }
288 }
289
290 /**
291 * current_cred - Access the current task's subjective credentials
292 *
293 * Access the subjective credentials of the current task. RCU-safe,
294 * since nobody else can modify it.
295 */
296 #define current_cred() \
297 rcu_dereference_protected(current->cred, 1)
298
299 /**
300 * current_real_cred - Access the current task's objective credentials
301 *
302 * Access the objective credentials of the current task. RCU-safe,
303 * since nobody else can modify it.
304 */
305 #define current_real_cred() \
306 rcu_dereference_protected(current->real_cred, 1)
307
308 /**
309 * __task_cred - Access a task's objective credentials
310 * @task: The task to query
311 *
312 * Access the objective credentials of a task. The caller must hold the RCU
313 * readlock.
314 *
315 * The result of this function should not be passed directly to get_cred();
316 * rather get_task_cred() should be used instead.
317 */
318 #define __task_cred(task) \
319 rcu_dereference((task)->real_cred)
320
321 /**
322 * get_current_cred - Get the current task's subjective credentials
323 *
324 * Get the subjective credentials of the current task, pinning them so that
325 * they can't go away. Accessing the current task's credentials directly is
326 * not permitted.
327 */
328 #define get_current_cred() \
329 (get_cred(current_cred()))
330
331 /**
332 * get_current_user - Get the current task's user_struct
333 *
334 * Get the user record of the current task, pinning it so that it can't go
335 * away.
336 */
337 #define get_current_user() \
338 ({ \
339 struct user_struct *__u; \
340 const struct cred *__cred; \
341 __cred = current_cred(); \
342 __u = get_uid(__cred->user); \
343 __u; \
344 })
345
346 /**
347 * get_current_groups - Get the current task's supplementary group list
348 *
349 * Get the supplementary group list of the current task, pinning it so that it
350 * can't go away.
351 */
352 #define get_current_groups() \
353 ({ \
354 struct group_info *__groups; \
355 const struct cred *__cred; \
356 __cred = current_cred(); \
357 __groups = get_group_info(__cred->group_info); \
358 __groups; \
359 })
360
361 #define task_cred_xxx(task, xxx) \
362 ({ \
363 __typeof__(((struct cred *)NULL)->xxx) ___val; \
364 rcu_read_lock(); \
365 ___val = __task_cred((task))->xxx; \
366 rcu_read_unlock(); \
367 ___val; \
368 })
369
370 #define task_uid(task) (task_cred_xxx((task), uid))
371 #define task_euid(task) (task_cred_xxx((task), euid))
372
373 #define current_cred_xxx(xxx) \
374 ({ \
375 current_cred()->xxx; \
376 })
377
378 #define current_uid() (current_cred_xxx(uid))
379 #define current_gid() (current_cred_xxx(gid))
380 #define current_euid() (current_cred_xxx(euid))
381 #define current_egid() (current_cred_xxx(egid))
382 #define current_suid() (current_cred_xxx(suid))
383 #define current_sgid() (current_cred_xxx(sgid))
384 #define current_fsuid() (current_cred_xxx(fsuid))
385 #define current_fsgid() (current_cred_xxx(fsgid))
386 #define current_cap() (current_cred_xxx(cap_effective))
387 #define current_user() (current_cred_xxx(user))
388
389 extern struct user_namespace init_user_ns;
390 #ifdef CONFIG_USER_NS
391 #define current_user_ns() (current_cred_xxx(user_ns))
392 #else
current_user_ns(void)393 static 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) \
401 do { \
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) \
409 do { \
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) \
417 do { \
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