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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 #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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