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[0];
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 extern struct group_info init_groups;
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_t usage;
113 #ifdef CONFIG_DEBUG_CREDENTIALS
114 atomic_t subscribers; /* number of processes subscribed */
115 void *put_addr;
116 unsigned magic;
117 #define CRED_MAGIC 0x43736564
118 #define CRED_MAGIC_DEAD 0x44656144
119 #endif
120 kuid_t uid; /* real UID of the task */
121 kgid_t gid; /* real GID of the task */
122 kuid_t suid; /* saved UID of the task */
123 kgid_t sgid; /* saved GID of the task */
124 kuid_t euid; /* effective UID of the task */
125 kgid_t egid; /* effective GID of the task */
126 kuid_t fsuid; /* UID for VFS ops */
127 kgid_t fsgid; /* GID for VFS ops */
128 unsigned securebits; /* SUID-less security management */
129 kernel_cap_t cap_inheritable; /* caps our children can inherit */
130 kernel_cap_t cap_permitted; /* caps we're permitted */
131 kernel_cap_t cap_effective; /* caps we can actually use */
132 kernel_cap_t cap_bset; /* capability bounding set */
133 kernel_cap_t cap_ambient; /* Ambient capability set */
134 #ifdef CONFIG_KEYS
135 unsigned char jit_keyring; /* default keyring to attach requested
136 * keys to */
137 struct key *session_keyring; /* keyring inherited over fork */
138 struct key *process_keyring; /* keyring private to this process */
139 struct key *thread_keyring; /* keyring private to this thread */
140 struct key *request_key_auth; /* assumed request_key authority */
141 #endif
142 #ifdef CONFIG_SECURITY
143 void *security; /* subjective LSM security */
144 #endif
145 struct user_struct *user; /* real user ID subscription */
146 struct user_namespace *user_ns; /* user_ns the caps and keyrings are relative to. */
147 struct group_info *group_info; /* supplementary groups for euid/fsgid */
148 /* RCU deletion */
149 union {
150 int non_rcu; /* Can we skip RCU deletion? */
151 struct rcu_head rcu; /* RCU deletion hook */
152 };
153 } __randomize_layout;
154
155 extern void __put_cred(struct cred *);
156 extern void exit_creds(struct task_struct *);
157 extern int copy_creds(struct task_struct *, unsigned long);
158 extern const struct cred *get_task_cred(struct task_struct *);
159 extern struct cred *cred_alloc_blank(void);
160 extern struct cred *prepare_creds(void);
161 extern struct cred *prepare_exec_creds(void);
162 extern int commit_creds(struct cred *);
163 extern void abort_creds(struct cred *);
164 extern const struct cred *override_creds(const struct cred *);
165 extern void revert_creds(const struct cred *);
166 extern struct cred *prepare_kernel_cred(struct task_struct *);
167 extern int change_create_files_as(struct cred *, struct inode *);
168 extern int set_security_override(struct cred *, u32);
169 extern int set_security_override_from_ctx(struct cred *, const char *);
170 extern int set_create_files_as(struct cred *, struct inode *);
171 extern int cred_fscmp(const struct cred *, const struct cred *);
172 extern void __init cred_init(void);
173
174 /*
175 * check for validity of credentials
176 */
177 #ifdef CONFIG_DEBUG_CREDENTIALS
178 extern void __invalid_creds(const struct cred *, const char *, unsigned);
179 extern void __validate_process_creds(struct task_struct *,
180 const char *, unsigned);
181
182 extern bool creds_are_invalid(const struct cred *cred);
183
__validate_creds(const struct cred * cred,const char * file,unsigned line)184 static 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) \
192 do { \
193 __validate_creds((cred), __FILE__, __LINE__); \
194 } while(0)
195
196 #define validate_process_creds() \
197 do { \
198 __validate_process_creds(current, __FILE__, __LINE__); \
199 } while(0)
200
201 extern void validate_creds_for_do_exit(struct task_struct *);
202 #else
validate_creds(const struct cred * cred)203 static inline void validate_creds(const struct cred *cred)
204 {
205 }
validate_creds_for_do_exit(struct task_struct * tsk)206 static inline void validate_creds_for_do_exit(struct task_struct *tsk)
207 {
208 }
validate_process_creds(void)209 static inline void validate_process_creds(void)
210 {
211 }
212 #endif
213
cap_ambient_invariant_ok(const struct cred * cred)214 static 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 */
get_new_cred(struct cred * cred)228 static 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. If %NULL is passed, it is returned with no action.
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 */
get_cred(const struct cred * cred)247 static inline const struct cred *get_cred(const struct cred *cred)
248 {
249 struct cred *nonconst_cred = (struct cred *) cred;
250 if (!cred)
251 return cred;
252 validate_creds(cred);
253 nonconst_cred->non_rcu = 0;
254 return get_new_cred(nonconst_cred);
255 }
256
get_cred_rcu(const struct cred * cred)257 static inline const struct cred *get_cred_rcu(const struct cred *cred)
258 {
259 struct cred *nonconst_cred = (struct cred *) cred;
260 if (!cred)
261 return NULL;
262 if (!atomic_inc_not_zero(&nonconst_cred->usage))
263 return NULL;
264 validate_creds(cred);
265 nonconst_cred->non_rcu = 0;
266 return cred;
267 }
268
269 /**
270 * put_cred - Release a reference to a set of credentials
271 * @cred: The credentials to release
272 *
273 * Release a reference to a set of credentials, deleting them when the last ref
274 * is released. If %NULL is passed, nothing is done.
275 *
276 * This takes a const pointer to a set of credentials because the credentials
277 * on task_struct are attached by const pointers to prevent accidental
278 * alteration of otherwise immutable credential sets.
279 */
put_cred(const struct cred * _cred)280 static inline void put_cred(const struct cred *_cred)
281 {
282 struct cred *cred = (struct cred *) _cred;
283
284 if (cred) {
285 validate_creds(cred);
286 if (atomic_dec_and_test(&(cred)->usage))
287 __put_cred(cred);
288 }
289 }
290
291 /**
292 * current_cred - Access the current task's subjective credentials
293 *
294 * Access the subjective credentials of the current task. RCU-safe,
295 * since nobody else can modify it.
296 */
297 #define current_cred() \
298 rcu_dereference_protected(current->cred, 1)
299
300 /**
301 * current_real_cred - Access the current task's objective credentials
302 *
303 * Access the objective credentials of the current task. RCU-safe,
304 * since nobody else can modify it.
305 */
306 #define current_real_cred() \
307 rcu_dereference_protected(current->real_cred, 1)
308
309 /**
310 * __task_cred - Access a task's objective credentials
311 * @task: The task to query
312 *
313 * Access the objective credentials of a task. The caller must hold the RCU
314 * readlock.
315 *
316 * The result of this function should not be passed directly to get_cred();
317 * rather get_task_cred() should be used instead.
318 */
319 #define __task_cred(task) \
320 rcu_dereference((task)->real_cred)
321
322 /**
323 * get_current_cred - Get the current task's subjective credentials
324 *
325 * Get the subjective credentials of the current task, pinning them so that
326 * they can't go away. Accessing the current task's credentials directly is
327 * not permitted.
328 */
329 #define get_current_cred() \
330 (get_cred(current_cred()))
331
332 /**
333 * get_current_user - Get the current task's user_struct
334 *
335 * Get the user record of the current task, pinning it so that it can't go
336 * away.
337 */
338 #define get_current_user() \
339 ({ \
340 struct user_struct *__u; \
341 const struct cred *__cred; \
342 __cred = current_cred(); \
343 __u = get_uid(__cred->user); \
344 __u; \
345 })
346
347 /**
348 * get_current_groups - Get the current task's supplementary group list
349 *
350 * Get the supplementary group list of the current task, pinning it so that it
351 * can't go away.
352 */
353 #define get_current_groups() \
354 ({ \
355 struct group_info *__groups; \
356 const struct cred *__cred; \
357 __cred = current_cred(); \
358 __groups = get_group_info(__cred->group_info); \
359 __groups; \
360 })
361
362 #define task_cred_xxx(task, xxx) \
363 ({ \
364 __typeof__(((struct cred *)NULL)->xxx) ___val; \
365 rcu_read_lock(); \
366 ___val = __task_cred((task))->xxx; \
367 rcu_read_unlock(); \
368 ___val; \
369 })
370
371 #define task_uid(task) (task_cred_xxx((task), uid))
372 #define task_euid(task) (task_cred_xxx((task), euid))
373
374 #define current_cred_xxx(xxx) \
375 ({ \
376 current_cred()->xxx; \
377 })
378
379 #define current_uid() (current_cred_xxx(uid))
380 #define current_gid() (current_cred_xxx(gid))
381 #define current_euid() (current_cred_xxx(euid))
382 #define current_egid() (current_cred_xxx(egid))
383 #define current_suid() (current_cred_xxx(suid))
384 #define current_sgid() (current_cred_xxx(sgid))
385 #define current_fsuid() (current_cred_xxx(fsuid))
386 #define current_fsgid() (current_cred_xxx(fsgid))
387 #define current_cap() (current_cred_xxx(cap_effective))
388 #define current_user() (current_cred_xxx(user))
389
390 extern struct user_namespace init_user_ns;
391 #ifdef CONFIG_USER_NS
392 #define current_user_ns() (current_cred_xxx(user_ns))
393 #else
current_user_ns(void)394 static inline struct user_namespace *current_user_ns(void)
395 {
396 return &init_user_ns;
397 }
398 #endif
399
400
401 #define current_uid_gid(_uid, _gid) \
402 do { \
403 const struct cred *__cred; \
404 __cred = current_cred(); \
405 *(_uid) = __cred->uid; \
406 *(_gid) = __cred->gid; \
407 } while(0)
408
409 #define current_euid_egid(_euid, _egid) \
410 do { \
411 const struct cred *__cred; \
412 __cred = current_cred(); \
413 *(_euid) = __cred->euid; \
414 *(_egid) = __cred->egid; \
415 } while(0)
416
417 #define current_fsuid_fsgid(_fsuid, _fsgid) \
418 do { \
419 const struct cred *__cred; \
420 __cred = current_cred(); \
421 *(_fsuid) = __cred->fsuid; \
422 *(_fsgid) = __cred->fsgid; \
423 } while(0)
424
425 #endif /* _LINUX_CRED_H */
426