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

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  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 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
 75 static inline void groups_free(struct group_info *group_info)
 76 {
 77 }
 78 
 79 static inline int in_group_p(kgid_t grp)
 80 {
 81         return 1;
 82 }
 83 static inline int in_egroup_p(kgid_t grp)
 84 {
 85         return 1;
 86 }
 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         struct rcu_head rcu;            /* RCU deletion hook */
154 } __randomize_layout;
155 
156 extern void __put_cred(struct cred *);
157 extern void exit_creds(struct task_struct *);
158 extern int copy_creds(struct task_struct *, unsigned long);
159 extern const struct cred *get_task_cred(struct task_struct *);
160 extern struct cred *cred_alloc_blank(void);
161 extern struct cred *prepare_creds(void);
162 extern struct cred *prepare_exec_creds(void);
163 extern int commit_creds(struct cred *);
164 extern void abort_creds(struct cred *);
165 extern const struct cred *override_creds(const struct cred *);
166 extern void revert_creds(const struct cred *);
167 extern struct cred *prepare_kernel_cred(struct task_struct *);
168 extern int change_create_files_as(struct cred *, struct inode *);
169 extern int set_security_override(struct cred *, u32);
170 extern int set_security_override_from_ctx(struct cred *, const char *);
171 extern int set_create_files_as(struct cred *, struct inode *);
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.
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         validate_creds(cred);
251         return get_new_cred(nonconst_cred);
252 }
253 
254 /**
255  * put_cred - Release a reference to a set of credentials
256  * @cred: The credentials to release
257  *
258  * Release a reference to a set of credentials, deleting them when the last ref
259  * is released.
260  *
261  * This takes a const pointer to a set of credentials because the credentials
262  * on task_struct are attached by const pointers to prevent accidental
263  * alteration of otherwise immutable credential sets.
264  */
265 static inline void put_cred(const struct cred *_cred)
266 {
267         struct cred *cred = (struct cred *) _cred;
268 
269         validate_creds(cred);
270         if (atomic_dec_and_test(&(cred)->usage))
271                 __put_cred(cred);
272 }
273 
274 /**
275  * current_cred - Access the current task's subjective credentials
276  *
277  * Access the subjective credentials of the current task.  RCU-safe,
278  * since nobody else can modify it.
279  */
280 #define current_cred() \
281         rcu_dereference_protected(current->cred, 1)
282 
283 /**
284  * current_real_cred - Access the current task's objective credentials
285  *
286  * Access the objective credentials of the current task.  RCU-safe,
287  * since nobody else can modify it.
288  */
289 #define current_real_cred() \
290         rcu_dereference_protected(current->real_cred, 1)
291 
292 /**
293  * __task_cred - Access a task's objective credentials
294  * @task: The task to query
295  *
296  * Access the objective credentials of a task.  The caller must hold the RCU
297  * readlock.
298  *
299  * The result of this function should not be passed directly to get_cred();
300  * rather get_task_cred() should be used instead.
301  */
302 #define __task_cred(task)       \
303         rcu_dereference((task)->real_cred)
304 
305 /**
306  * get_current_cred - Get the current task's subjective credentials
307  *
308  * Get the subjective credentials of the current task, pinning them so that
309  * they can't go away.  Accessing the current task's credentials directly is
310  * not permitted.
311  */
312 #define get_current_cred()                              \
313         (get_cred(current_cred()))
314 
315 /**
316  * get_current_user - Get the current task's user_struct
317  *
318  * Get the user record of the current task, pinning it so that it can't go
319  * away.
320  */
321 #define get_current_user()                              \
322 ({                                                      \
323         struct user_struct *__u;                        \
324         const struct cred *__cred;                      \
325         __cred = current_cred();                        \
326         __u = get_uid(__cred->user);                    \
327         __u;                                            \
328 })
329 
330 /**
331  * get_current_groups - Get the current task's supplementary group list
332  *
333  * Get the supplementary group list of the current task, pinning it so that it
334  * can't go away.
335  */
336 #define get_current_groups()                            \
337 ({                                                      \
338         struct group_info *__groups;                    \
339         const struct cred *__cred;                      \
340         __cred = current_cred();                        \
341         __groups = get_group_info(__cred->group_info);  \
342         __groups;                                       \
343 })
344 
345 #define task_cred_xxx(task, xxx)                        \
346 ({                                                      \
347         __typeof__(((struct cred *)NULL)->xxx) ___val;  \
348         rcu_read_lock();                                \
349         ___val = __task_cred((task))->xxx;              \
350         rcu_read_unlock();                              \
351         ___val;                                         \
352 })
353 
354 #define task_uid(task)          (task_cred_xxx((task), uid))
355 #define task_euid(task)         (task_cred_xxx((task), euid))
356 
357 #define current_cred_xxx(xxx)                   \
358 ({                                              \
359         current_cred()->xxx;                    \
360 })
361 
362 #define current_uid()           (current_cred_xxx(uid))
363 #define current_gid()           (current_cred_xxx(gid))
364 #define current_euid()          (current_cred_xxx(euid))
365 #define current_egid()          (current_cred_xxx(egid))
366 #define current_suid()          (current_cred_xxx(suid))
367 #define current_sgid()          (current_cred_xxx(sgid))
368 #define current_fsuid()         (current_cred_xxx(fsuid))
369 #define current_fsgid()         (current_cred_xxx(fsgid))
370 #define current_cap()           (current_cred_xxx(cap_effective))
371 #define current_user()          (current_cred_xxx(user))
372 #define current_security()      (current_cred_xxx(security))
373 
374 extern struct user_namespace init_user_ns;
375 #ifdef CONFIG_USER_NS
376 #define current_user_ns()       (current_cred_xxx(user_ns))
377 #else
378 static inline struct user_namespace *current_user_ns(void)
379 {
380         return &init_user_ns;
381 }
382 #endif
383 
384 
385 #define current_uid_gid(_uid, _gid)             \
386 do {                                            \
387         const struct cred *__cred;              \
388         __cred = current_cred();                \
389         *(_uid) = __cred->uid;                  \
390         *(_gid) = __cred->gid;                  \
391 } while(0)
392 
393 #define current_euid_egid(_euid, _egid)         \
394 do {                                            \
395         const struct cred *__cred;              \
396         __cred = current_cred();                \
397         *(_euid) = __cred->euid;                \
398         *(_egid) = __cred->egid;                \
399 } while(0)
400 
401 #define current_fsuid_fsgid(_fsuid, _fsgid)     \
402 do {                                            \
403         const struct cred *__cred;              \
404         __cred = current_cred();                \
405         *(_fsuid) = __cred->fsuid;              \
406         *(_fsgid) = __cred->fsgid;              \
407 } while(0)
408 
409 #endif /* _LINUX_CRED_H */
410 

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