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 */
get_group_info(struct group_info * gi)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 extern int groups_search(const struct group_info *, kgid_t);
69
70 extern int set_current_groups(struct group_info *);
71 extern void set_groups(struct cred *, struct group_info *);
72 extern bool may_setgroups(void);
73 extern void groups_sort(struct group_info *);
74 #else
groups_free(struct group_info * group_info)75 static inline void groups_free(struct group_info *group_info)
76 {
77 }
78
in_group_p(kgid_t grp)79 static inline int in_group_p(kgid_t grp)
80 {
81 return 1;
82 }
in_egroup_p(kgid_t grp)83 static inline int in_egroup_p(kgid_t grp)
84 {
85 return 1;
86 }
groups_search(const struct group_info * group_info,kgid_t grp)87 static inline int groups_search(const struct group_info *group_info, kgid_t grp)
88 {
89 return 1;
90 }
91 #endif
92
93 /*
94 * The security context of a task
95 *
96 * The parts of the context break down into two categories:
97 *
98 * (1) The objective context of a task. These parts are used when some other
99 * task is attempting to affect this one.
100 *
101 * (2) The subjective context. These details are used when the task is acting
102 * upon another object, be that a file, a task, a key or whatever.
103 *
104 * Note that some members of this structure belong to both categories - the
105 * LSM security pointer for instance.
106 *
107 * A task has two security pointers. task->real_cred points to the objective
108 * context that defines that task's actual details. The objective part of this
109 * context is used whenever that task is acted upon.
110 *
111 * task->cred points to the subjective context that defines the details of how
112 * that task is going to act upon another object. This may be overridden
113 * temporarily to point to another security context, but normally points to the
114 * same context as task->real_cred.
115 */
116 struct cred {
117 atomic_t usage;
118 #ifdef CONFIG_DEBUG_CREDENTIALS
119 atomic_t subscribers; /* number of processes subscribed */
120 void *put_addr;
121 unsigned magic;
122 #define CRED_MAGIC 0x43736564
123 #define CRED_MAGIC_DEAD 0x44656144
124 #endif
125 kuid_t uid; /* real UID of the task */
126 kgid_t gid; /* real GID of the task */
127 kuid_t suid; /* saved UID of the task */
128 kgid_t sgid; /* saved GID of the task */
129 kuid_t euid; /* effective UID of the task */
130 kgid_t egid; /* effective GID of the task */
131 kuid_t fsuid; /* UID for VFS ops */
132 kgid_t fsgid; /* GID for VFS ops */
133 unsigned securebits; /* SUID-less security management */
134 kernel_cap_t cap_inheritable; /* caps our children can inherit */
135 kernel_cap_t cap_permitted; /* caps we're permitted */
136 kernel_cap_t cap_effective; /* caps we can actually use */
137 kernel_cap_t cap_bset; /* capability bounding set */
138 kernel_cap_t cap_ambient; /* Ambient capability set */
139 #ifdef CONFIG_KEYS
140 unsigned char jit_keyring; /* default keyring to attach requested
141 * keys to */
142 struct key __rcu *session_keyring; /* keyring inherited over fork */
143 struct key *process_keyring; /* keyring private to this process */
144 struct key *thread_keyring; /* keyring private to this thread */
145 struct key *request_key_auth; /* assumed request_key authority */
146 #endif
147 #ifdef CONFIG_SECURITY
148 void *security; /* subjective LSM security */
149 #endif
150 struct user_struct *user; /* real user ID subscription */
151 struct user_namespace *user_ns; /* user_ns the caps and keyrings are relative to. */
152 struct group_info *group_info; /* supplementary groups for euid/fsgid */
153 /* RCU deletion */
154 union {
155 int non_rcu; /* Can we skip RCU deletion? */
156 struct rcu_head rcu; /* RCU deletion hook */
157 };
158 } __randomize_layout;
159
160 extern void __put_cred(struct cred *);
161 extern void exit_creds(struct task_struct *);
162 extern int copy_creds(struct task_struct *, unsigned long);
163 extern const struct cred *get_task_cred(struct task_struct *);
164 extern struct cred *cred_alloc_blank(void);
165 extern struct cred *prepare_creds(void);
166 extern struct cred *prepare_exec_creds(void);
167 extern int commit_creds(struct cred *);
168 extern void abort_creds(struct cred *);
169 extern const struct cred *override_creds(const struct cred *);
170 extern void revert_creds(const struct cred *);
171 extern struct cred *prepare_kernel_cred(struct task_struct *);
172 extern int change_create_files_as(struct cred *, struct inode *);
173 extern int set_security_override(struct cred *, u32);
174 extern int set_security_override_from_ctx(struct cred *, const char *);
175 extern int set_create_files_as(struct cred *, struct inode *);
176 extern void __init cred_init(void);
177
178 /*
179 * check for validity of credentials
180 */
181 #ifdef CONFIG_DEBUG_CREDENTIALS
182 extern void __invalid_creds(const struct cred *, const char *, unsigned);
183 extern void __validate_process_creds(struct task_struct *,
184 const char *, unsigned);
185
186 extern bool creds_are_invalid(const struct cred *cred);
187
__validate_creds(const struct cred * cred,const char * file,unsigned line)188 static inline void __validate_creds(const struct cred *cred,
189 const char *file, unsigned line)
190 {
191 if (unlikely(creds_are_invalid(cred)))
192 __invalid_creds(cred, file, line);
193 }
194
195 #define validate_creds(cred) \
196 do { \
197 __validate_creds((cred), __FILE__, __LINE__); \
198 } while(0)
199
200 #define validate_process_creds() \
201 do { \
202 __validate_process_creds(current, __FILE__, __LINE__); \
203 } while(0)
204
205 extern void validate_creds_for_do_exit(struct task_struct *);
206 #else
validate_creds(const struct cred * cred)207 static inline void validate_creds(const struct cred *cred)
208 {
209 }
validate_creds_for_do_exit(struct task_struct * tsk)210 static inline void validate_creds_for_do_exit(struct task_struct *tsk)
211 {
212 }
validate_process_creds(void)213 static inline void validate_process_creds(void)
214 {
215 }
216 #endif
217
cap_ambient_invariant_ok(const struct cred * cred)218 static inline bool cap_ambient_invariant_ok(const struct cred *cred)
219 {
220 return cap_issubset(cred->cap_ambient,
221 cap_intersect(cred->cap_permitted,
222 cred->cap_inheritable));
223 }
224
225 /**
226 * get_new_cred - Get a reference on a new set of credentials
227 * @cred: The new credentials to reference
228 *
229 * Get a reference on the specified set of new credentials. The caller must
230 * release the reference.
231 */
get_new_cred(struct cred * cred)232 static inline struct cred *get_new_cred(struct cred *cred)
233 {
234 atomic_inc(&cred->usage);
235 return cred;
236 }
237
238 /**
239 * get_cred - Get a reference on a set of credentials
240 * @cred: The credentials to reference
241 *
242 * Get a reference on the specified set of credentials. The caller must
243 * release the reference.
244 *
245 * This is used to deal with a committed set of credentials. Although the
246 * pointer is const, this will temporarily discard the const and increment the
247 * usage count. The purpose of this is to attempt to catch at compile time the
248 * accidental alteration of a set of credentials that should be considered
249 * immutable.
250 */
get_cred(const struct cred * cred)251 static inline const struct cred *get_cred(const struct cred *cred)
252 {
253 struct cred *nonconst_cred = (struct cred *) cred;
254 validate_creds(cred);
255 nonconst_cred->non_rcu = 0;
256 return get_new_cred(nonconst_cred);
257 }
258
259 /**
260 * put_cred - Release a reference to a set of credentials
261 * @cred: The credentials to release
262 *
263 * Release a reference to a set of credentials, deleting them when the last ref
264 * is released.
265 *
266 * This takes a const pointer to a set of credentials because the credentials
267 * on task_struct are attached by const pointers to prevent accidental
268 * alteration of otherwise immutable credential sets.
269 */
put_cred(const struct cred * _cred)270 static inline void put_cred(const struct cred *_cred)
271 {
272 struct cred *cred = (struct cred *) _cred;
273
274 validate_creds(cred);
275 if (atomic_dec_and_test(&(cred)->usage))
276 __put_cred(cred);
277 }
278
279 /**
280 * current_cred - Access the current task's subjective credentials
281 *
282 * Access the subjective credentials of the current task. RCU-safe,
283 * since nobody else can modify it.
284 */
285 #define current_cred() \
286 rcu_dereference_protected(current->cred, 1)
287
288 /**
289 * current_real_cred - Access the current task's objective credentials
290 *
291 * Access the objective credentials of the current task. RCU-safe,
292 * since nobody else can modify it.
293 */
294 #define current_real_cred() \
295 rcu_dereference_protected(current->real_cred, 1)
296
297 /**
298 * __task_cred - Access a task's objective credentials
299 * @task: The task to query
300 *
301 * Access the objective credentials of a task. The caller must hold the RCU
302 * readlock.
303 *
304 * The result of this function should not be passed directly to get_cred();
305 * rather get_task_cred() should be used instead.
306 */
307 #define __task_cred(task) \
308 rcu_dereference((task)->real_cred)
309
310 /**
311 * get_current_cred - Get the current task's subjective credentials
312 *
313 * Get the subjective credentials of the current task, pinning them so that
314 * they can't go away. Accessing the current task's credentials directly is
315 * not permitted.
316 */
317 #define get_current_cred() \
318 (get_cred(current_cred()))
319
320 /**
321 * get_current_user - Get the current task's user_struct
322 *
323 * Get the user record of the current task, pinning it so that it can't go
324 * away.
325 */
326 #define get_current_user() \
327 ({ \
328 struct user_struct *__u; \
329 const struct cred *__cred; \
330 __cred = current_cred(); \
331 __u = get_uid(__cred->user); \
332 __u; \
333 })
334
335 /**
336 * get_current_groups - Get the current task's supplementary group list
337 *
338 * Get the supplementary group list of the current task, pinning it so that it
339 * can't go away.
340 */
341 #define get_current_groups() \
342 ({ \
343 struct group_info *__groups; \
344 const struct cred *__cred; \
345 __cred = current_cred(); \
346 __groups = get_group_info(__cred->group_info); \
347 __groups; \
348 })
349
350 #define task_cred_xxx(task, xxx) \
351 ({ \
352 __typeof__(((struct cred *)NULL)->xxx) ___val; \
353 rcu_read_lock(); \
354 ___val = __task_cred((task))->xxx; \
355 rcu_read_unlock(); \
356 ___val; \
357 })
358
359 #define task_uid(task) (task_cred_xxx((task), uid))
360 #define task_euid(task) (task_cred_xxx((task), euid))
361
362 #define current_cred_xxx(xxx) \
363 ({ \
364 current_cred()->xxx; \
365 })
366
367 #define current_uid() (current_cred_xxx(uid))
368 #define current_gid() (current_cred_xxx(gid))
369 #define current_euid() (current_cred_xxx(euid))
370 #define current_egid() (current_cred_xxx(egid))
371 #define current_suid() (current_cred_xxx(suid))
372 #define current_sgid() (current_cred_xxx(sgid))
373 #define current_fsuid() (current_cred_xxx(fsuid))
374 #define current_fsgid() (current_cred_xxx(fsgid))
375 #define current_cap() (current_cred_xxx(cap_effective))
376 #define current_user() (current_cred_xxx(user))
377 #define current_security() (current_cred_xxx(security))
378
379 extern struct user_namespace init_user_ns;
380 #ifdef CONFIG_USER_NS
381 #define current_user_ns() (current_cred_xxx(user_ns))
382 #else
current_user_ns(void)383 static inline struct user_namespace *current_user_ns(void)
384 {
385 return &init_user_ns;
386 }
387 #endif
388
389
390 #define current_uid_gid(_uid, _gid) \
391 do { \
392 const struct cred *__cred; \
393 __cred = current_cred(); \
394 *(_uid) = __cred->uid; \
395 *(_gid) = __cred->gid; \
396 } while(0)
397
398 #define current_euid_egid(_euid, _egid) \
399 do { \
400 const struct cred *__cred; \
401 __cred = current_cred(); \
402 *(_euid) = __cred->euid; \
403 *(_egid) = __cred->egid; \
404 } while(0)
405
406 #define current_fsuid_fsgid(_fsuid, _fsgid) \
407 do { \
408 const struct cred *__cred; \
409 __cred = current_cred(); \
410 *(_fsuid) = __cred->fsuid; \
411 *(_fsgid) = __cred->fsgid; \
412 } while(0)
413
414 #endif /* _LINUX_CRED_H */
415