1 /* Credentials management - see Documentation/security/credentials.rst
2 *
3 * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved.
4 * Written by David Howells (dhowells@redhat.com)
5 *
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public Licence
8 * as published by the Free Software Foundation; either version
9 * 2 of the Licence, or (at your option) any later version.
10 */
11
12 #ifndef _LINUX_CRED_H
13 #define _LINUX_CRED_H
14
15 #include <linux/capability.h>
16 #include <linux/init.h>
17 #include <linux/key.h>
18 #include <linux/selinux.h>
19 #include <linux/atomic.h>
20 #include <linux/uidgid.h>
21 #include <linux/sched.h>
22 #include <linux/sched/user.h>
23
24 struct cred;
25 struct inode;
26
27 /*
28 * COW Supplementary groups list
29 */
30 struct group_info {
31 atomic_t usage;
32 int ngroups;
33 kgid_t gid[0];
34 } __randomize_layout;
35
36 /**
37 * get_group_info - Get a reference to a group info structure
38 * @group_info: The group info to reference
39 *
40 * This gets a reference to a set of supplementary groups.
41 *
42 * If the caller is accessing a task's credentials, they must hold the RCU read
43 * lock when reading.
44 */
45 static inline struct group_info *get_group_info(struct group_info *gi)
46 {
47 atomic_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 (atomic_dec_and_test(&(group_info)->usage)) \
58 groups_free(group_info); \
59 } while (0)
60
61 extern struct group_info init_groups;
62 #ifdef CONFIG_MULTIUSER
63 extern struct group_info *groups_alloc(int);
64 extern void groups_free(struct group_info *);
65
66 extern int in_group_p(kgid_t);
67 extern int in_egroup_p(kgid_t);
68 #else
69 static inline void groups_free(struct group_info *group_info)
70 {
71 }
72
73 static inline int in_group_p(kgid_t grp)
74 {
75 return 1;
76 }
77 static inline int in_egroup_p(kgid_t grp)
78 {
79 return 1;
80 }
81 #endif
82 extern int set_current_groups(struct group_info *);
83 extern void set_groups(struct cred *, struct group_info *);
84 extern int groups_search(const struct group_info *, kgid_t);
85 extern bool may_setgroups(void);
86 extern void groups_sort(struct group_info *);
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 __rcu *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 struct rcu_head rcu; /* RCU deletion hook */
149 } __randomize_layout;
150
151 extern void __put_cred(struct cred *);
152 extern void exit_creds(struct task_struct *);
153 extern int copy_creds(struct task_struct *, unsigned long);
154 extern const struct cred *get_task_cred(struct task_struct *);
155 extern struct cred *cred_alloc_blank(void);
156 extern struct cred *prepare_creds(void);
157 extern struct cred *prepare_exec_creds(void);
158 extern int commit_creds(struct cred *);
159 extern void abort_creds(struct cred *);
160 extern const struct cred *override_creds(const struct cred *);
161 extern void revert_creds(const struct cred *);
162 extern struct cred *prepare_kernel_cred(struct task_struct *);
163 extern int change_create_files_as(struct cred *, struct inode *);
164 extern int set_security_override(struct cred *, u32);
165 extern int set_security_override_from_ctx(struct cred *, const char *);
166 extern int set_create_files_as(struct cred *, struct inode *);
167 extern void __init cred_init(void);
168
169 /*
170 * check for validity of credentials
171 */
172 #ifdef CONFIG_DEBUG_CREDENTIALS
173 extern void __invalid_creds(const struct cred *, const char *, unsigned);
174 extern void __validate_process_creds(struct task_struct *,
175 const char *, unsigned);
176
177 extern bool creds_are_invalid(const struct cred *cred);
178
179 static inline void __validate_creds(const struct cred *cred,
180 const char *file, unsigned line)
181 {
182 if (unlikely(creds_are_invalid(cred)))
183 __invalid_creds(cred, file, line);
184 }
185
186 #define validate_creds(cred) \
187 do { \
188 __validate_creds((cred), __FILE__, __LINE__); \
189 } while(0)
190
191 #define validate_process_creds() \
192 do { \
193 __validate_process_creds(current, __FILE__, __LINE__); \
194 } while(0)
195
196 extern void validate_creds_for_do_exit(struct task_struct *);
197 #else
198 static inline void validate_creds(const struct cred *cred)
199 {
200 }
201 static inline void validate_creds_for_do_exit(struct task_struct *tsk)
202 {
203 }
204 static inline void validate_process_creds(void)
205 {
206 }
207 #endif
208
209 static inline bool cap_ambient_invariant_ok(const struct cred *cred)
210 {
211 return cap_issubset(cred->cap_ambient,
212 cap_intersect(cred->cap_permitted,
213 cred->cap_inheritable));
214 }
215
216 /**
217 * get_new_cred - Get a reference on a new set of credentials
218 * @cred: The new credentials to reference
219 *
220 * Get a reference on the specified set of new credentials. The caller must
221 * release the reference.
222 */
223 static inline struct cred *get_new_cred(struct cred *cred)
224 {
225 atomic_inc(&cred->usage);
226 return cred;
227 }
228
229 /**
230 * get_cred - Get a reference on a set of credentials
231 * @cred: The credentials to reference
232 *
233 * Get a reference on the specified set of credentials. The caller must
234 * release the reference.
235 *
236 * This is used to deal with a committed set of credentials. Although the
237 * pointer is const, this will temporarily discard the const and increment the
238 * usage count. The purpose of this is to attempt to catch at compile time the
239 * accidental alteration of a set of credentials that should be considered
240 * immutable.
241 */
242 static inline const struct cred *get_cred(const struct cred *cred)
243 {
244 struct cred *nonconst_cred = (struct cred *) cred;
245 validate_creds(cred);
246 return get_new_cred(nonconst_cred);
247 }
248
249 /**
250 * put_cred - Release a reference to a set of credentials
251 * @cred: The credentials to release
252 *
253 * Release a reference to a set of credentials, deleting them when the last ref
254 * is released.
255 *
256 * This takes a const pointer to a set of credentials because the credentials
257 * on task_struct are attached by const pointers to prevent accidental
258 * alteration of otherwise immutable credential sets.
259 */
260 static inline void put_cred(const struct cred *_cred)
261 {
262 struct cred *cred = (struct cred *) _cred;
263
264 validate_creds(cred);
265 if (atomic_dec_and_test(&(cred)->usage))
266 __put_cred(cred);
267 }
268
269 /**
270 * current_cred - Access the current task's subjective credentials
271 *
272 * Access the subjective credentials of the current task. RCU-safe,
273 * since nobody else can modify it.
274 */
275 #define current_cred() \
276 rcu_dereference_protected(current->cred, 1)
277
278 /**
279 * current_real_cred - Access the current task's objective credentials
280 *
281 * Access the objective credentials of the current task. RCU-safe,
282 * since nobody else can modify it.
283 */
284 #define current_real_cred() \
285 rcu_dereference_protected(current->real_cred, 1)
286
287 /**
288 * __task_cred - Access a task's objective credentials
289 * @task: The task to query
290 *
291 * Access the objective credentials of a task. The caller must hold the RCU
292 * readlock.
293 *
294 * The result of this function should not be passed directly to get_cred();
295 * rather get_task_cred() should be used instead.
296 */
297 #define __task_cred(task) \
298 rcu_dereference((task)->real_cred)
299
300 /**
301 * get_current_cred - Get the current task's subjective credentials
302 *
303 * Get the subjective credentials of the current task, pinning them so that
304 * they can't go away. Accessing the current task's credentials directly is
305 * not permitted.
306 */
307 #define get_current_cred() \
308 (get_cred(current_cred()))
309
310 /**
311 * get_current_user - Get the current task's user_struct
312 *
313 * Get the user record of the current task, pinning it so that it can't go
314 * away.
315 */
316 #define get_current_user() \
317 ({ \
318 struct user_struct *__u; \
319 const struct cred *__cred; \
320 __cred = current_cred(); \
321 __u = get_uid(__cred->user); \
322 __u; \
323 })
324
325 /**
326 * get_current_groups - Get the current task's supplementary group list
327 *
328 * Get the supplementary group list of the current task, pinning it so that it
329 * can't go away.
330 */
331 #define get_current_groups() \
332 ({ \
333 struct group_info *__groups; \
334 const struct cred *__cred; \
335 __cred = current_cred(); \
336 __groups = get_group_info(__cred->group_info); \
337 __groups; \
338 })
339
340 #define task_cred_xxx(task, xxx) \
341 ({ \
342 __typeof__(((struct cred *)NULL)->xxx) ___val; \
343 rcu_read_lock(); \
344 ___val = __task_cred((task))->xxx; \
345 rcu_read_unlock(); \
346 ___val; \
347 })
348
349 #define task_uid(task) (task_cred_xxx((task), uid))
350 #define task_euid(task) (task_cred_xxx((task), euid))
351
352 #define current_cred_xxx(xxx) \
353 ({ \
354 current_cred()->xxx; \
355 })
356
357 #define current_uid() (current_cred_xxx(uid))
358 #define current_gid() (current_cred_xxx(gid))
359 #define current_euid() (current_cred_xxx(euid))
360 #define current_egid() (current_cred_xxx(egid))
361 #define current_suid() (current_cred_xxx(suid))
362 #define current_sgid() (current_cred_xxx(sgid))
363 #define current_fsuid() (current_cred_xxx(fsuid))
364 #define current_fsgid() (current_cred_xxx(fsgid))
365 #define current_cap() (current_cred_xxx(cap_effective))
366 #define current_user() (current_cred_xxx(user))
367 #define current_security() (current_cred_xxx(security))
368
369 extern struct user_namespace init_user_ns;
370 #ifdef CONFIG_USER_NS
371 #define current_user_ns() (current_cred_xxx(user_ns))
372 #else
373 static inline struct user_namespace *current_user_ns(void)
374 {
375 return &init_user_ns;
376 }
377 #endif
378
379
380 #define current_uid_gid(_uid, _gid) \
381 do { \
382 const struct cred *__cred; \
383 __cred = current_cred(); \
384 *(_uid) = __cred->uid; \
385 *(_gid) = __cred->gid; \
386 } while(0)
387
388 #define current_euid_egid(_euid, _egid) \
389 do { \
390 const struct cred *__cred; \
391 __cred = current_cred(); \
392 *(_euid) = __cred->euid; \
393 *(_egid) = __cred->egid; \
394 } while(0)
395
396 #define current_fsuid_fsgid(_fsuid, _fsgid) \
397 do { \
398 const struct cred *__cred; \
399 __cred = current_cred(); \
400 *(_fsuid) = __cred->fsuid; \
401 *(_fsgid) = __cred->fsgid; \
402 } while(0)
403
404 #endif /* _LINUX_CRED_H */
405
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