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TOMOYO Linux Cross Reference
Linux/include/linux/cred.h

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  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  */
 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
 70 static inline void groups_free(struct group_info *group_info)
 71 {
 72 }
 73 
 74 static inline int in_group_p(kgid_t grp)
 75 {
 76         return 1;
 77 }
 78 static inline int in_egroup_p(kgid_t grp)
 79 {
 80         return 1;
 81 }
 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 
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
203 static inline void validate_creds(const struct cred *cred)
204 {
205 }
206 static inline void validate_creds_for_do_exit(struct task_struct *tsk)
207 {
208 }
209 static inline void validate_process_creds(void)
210 {
211 }
212 #endif
213 
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  */
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  */
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 
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  */
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
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 

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