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Linux/include/linux/cred.h

  1 /* Credentials management - see Documentation/security/credentials.txt
  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 
 22 struct user_struct;
 23 struct cred;
 24 struct inode;
 25 
 26 /*
 27  * COW Supplementary groups list
 28  */
 29 #define NGROUPS_SMALL           32
 30 #define NGROUPS_PER_BLOCK       ((unsigned int)(PAGE_SIZE / sizeof(kgid_t)))
 31 
 32 struct group_info {
 33         atomic_t        usage;
 34         int             ngroups;
 35         int             nblocks;
 36         kgid_t          small_block[NGROUPS_SMALL];
 37         kgid_t          *blocks[0];
 38 };
 39 
 40 /**
 41  * get_group_info - Get a reference to a group info structure
 42  * @group_info: The group info to reference
 43  *
 44  * This gets a reference to a set of supplementary groups.
 45  *
 46  * If the caller is accessing a task's credentials, they must hold the RCU read
 47  * lock when reading.
 48  */
 49 static inline struct group_info *get_group_info(struct group_info *gi)
 50 {
 51         atomic_inc(&gi->usage);
 52         return gi;
 53 }
 54 
 55 /**
 56  * put_group_info - Release a reference to a group info structure
 57  * @group_info: The group info to release
 58  */
 59 #define put_group_info(group_info)                      \
 60 do {                                                    \
 61         if (atomic_dec_and_test(&(group_info)->usage))  \
 62                 groups_free(group_info);                \
 63 } while (0)
 64 
 65 extern struct group_info *groups_alloc(int);
 66 extern struct group_info init_groups;
 67 extern void groups_free(struct group_info *);
 68 extern int set_current_groups(struct group_info *);
 69 extern int set_groups(struct cred *, struct group_info *);
 70 extern int groups_search(const struct group_info *, kgid_t);
 71 
 72 /* access the groups "array" with this macro */
 73 #define GROUP_AT(gi, i) \
 74         ((gi)->blocks[(i) / NGROUPS_PER_BLOCK][(i) % NGROUPS_PER_BLOCK])
 75 
 76 extern int in_group_p(kgid_t);
 77 extern int in_egroup_p(kgid_t);
 78 
 79 /*
 80  * The security context of a task
 81  *
 82  * The parts of the context break down into two categories:
 83  *
 84  *  (1) The objective context of a task.  These parts are used when some other
 85  *      task is attempting to affect this one.
 86  *
 87  *  (2) The subjective context.  These details are used when the task is acting
 88  *      upon another object, be that a file, a task, a key or whatever.
 89  *
 90  * Note that some members of this structure belong to both categories - the
 91  * LSM security pointer for instance.
 92  *
 93  * A task has two security pointers.  task->real_cred points to the objective
 94  * context that defines that task's actual details.  The objective part of this
 95  * context is used whenever that task is acted upon.
 96  *
 97  * task->cred points to the subjective context that defines the details of how
 98  * that task is going to act upon another object.  This may be overridden
 99  * temporarily to point to another security context, but normally points to the
100  * same context as task->real_cred.
101  */
102 struct cred {
103         atomic_t        usage;
104 #ifdef CONFIG_DEBUG_CREDENTIALS
105         atomic_t        subscribers;    /* number of processes subscribed */
106         void            *put_addr;
107         unsigned        magic;
108 #define CRED_MAGIC      0x43736564
109 #define CRED_MAGIC_DEAD 0x44656144
110 #endif
111         kuid_t          uid;            /* real UID of the task */
112         kgid_t          gid;            /* real GID of the task */
113         kuid_t          suid;           /* saved UID of the task */
114         kgid_t          sgid;           /* saved GID of the task */
115         kuid_t          euid;           /* effective UID of the task */
116         kgid_t          egid;           /* effective GID of the task */
117         kuid_t          fsuid;          /* UID for VFS ops */
118         kgid_t          fsgid;          /* GID for VFS ops */
119         unsigned        securebits;     /* SUID-less security management */
120         kernel_cap_t    cap_inheritable; /* caps our children can inherit */
121         kernel_cap_t    cap_permitted;  /* caps we're permitted */
122         kernel_cap_t    cap_effective;  /* caps we can actually use */
123         kernel_cap_t    cap_bset;       /* capability bounding set */
124 #ifdef CONFIG_KEYS
125         unsigned char   jit_keyring;    /* default keyring to attach requested
126                                          * keys to */
127         struct key __rcu *session_keyring; /* keyring inherited over fork */
128         struct key      *process_keyring; /* keyring private to this process */
129         struct key      *thread_keyring; /* keyring private to this thread */
130         struct key      *request_key_auth; /* assumed request_key authority */
131 #endif
132 #ifdef CONFIG_SECURITY
133         void            *security;      /* subjective LSM security */
134 #endif
135         struct user_struct *user;       /* real user ID subscription */
136         struct user_namespace *user_ns; /* user_ns the caps and keyrings are relative to. */
137         struct group_info *group_info;  /* supplementary groups for euid/fsgid */
138         struct rcu_head rcu;            /* RCU deletion hook */
139 };
140 
141 extern void __put_cred(struct cred *);
142 extern void exit_creds(struct task_struct *);
143 extern int copy_creds(struct task_struct *, unsigned long);
144 extern const struct cred *get_task_cred(struct task_struct *);
145 extern struct cred *cred_alloc_blank(void);
146 extern struct cred *prepare_creds(void);
147 extern struct cred *prepare_exec_creds(void);
148 extern int commit_creds(struct cred *);
149 extern void abort_creds(struct cred *);
150 extern const struct cred *override_creds(const struct cred *);
151 extern void revert_creds(const struct cred *);
152 extern struct cred *prepare_kernel_cred(struct task_struct *);
153 extern int change_create_files_as(struct cred *, struct inode *);
154 extern int set_security_override(struct cred *, u32);
155 extern int set_security_override_from_ctx(struct cred *, const char *);
156 extern int set_create_files_as(struct cred *, struct inode *);
157 extern void __init cred_init(void);
158 
159 /*
160  * check for validity of credentials
161  */
162 #ifdef CONFIG_DEBUG_CREDENTIALS
163 extern void __invalid_creds(const struct cred *, const char *, unsigned);
164 extern void __validate_process_creds(struct task_struct *,
165                                      const char *, unsigned);
166 
167 extern bool creds_are_invalid(const struct cred *cred);
168 
169 static inline void __validate_creds(const struct cred *cred,
170                                     const char *file, unsigned line)
171 {
172         if (unlikely(creds_are_invalid(cred)))
173                 __invalid_creds(cred, file, line);
174 }
175 
176 #define validate_creds(cred)                            \
177 do {                                                    \
178         __validate_creds((cred), __FILE__, __LINE__);   \
179 } while(0)
180 
181 #define validate_process_creds()                                \
182 do {                                                            \
183         __validate_process_creds(current, __FILE__, __LINE__);  \
184 } while(0)
185 
186 extern void validate_creds_for_do_exit(struct task_struct *);
187 #else
188 static inline void validate_creds(const struct cred *cred)
189 {
190 }
191 static inline void validate_creds_for_do_exit(struct task_struct *tsk)
192 {
193 }
194 static inline void validate_process_creds(void)
195 {
196 }
197 #endif
198 
199 /**
200  * get_new_cred - Get a reference on a new set of credentials
201  * @cred: The new credentials to reference
202  *
203  * Get a reference on the specified set of new credentials.  The caller must
204  * release the reference.
205  */
206 static inline struct cred *get_new_cred(struct cred *cred)
207 {
208         atomic_inc(&cred->usage);
209         return cred;
210 }
211 
212 /**
213  * get_cred - Get a reference on a set of credentials
214  * @cred: The credentials to reference
215  *
216  * Get a reference on the specified set of credentials.  The caller must
217  * release the reference.
218  *
219  * This is used to deal with a committed set of credentials.  Although the
220  * pointer is const, this will temporarily discard the const and increment the
221  * usage count.  The purpose of this is to attempt to catch at compile time the
222  * accidental alteration of a set of credentials that should be considered
223  * immutable.
224  */
225 static inline const struct cred *get_cred(const struct cred *cred)
226 {
227         struct cred *nonconst_cred = (struct cred *) cred;
228         validate_creds(cred);
229         return get_new_cred(nonconst_cred);
230 }
231 
232 /**
233  * put_cred - Release a reference to a set of credentials
234  * @cred: The credentials to release
235  *
236  * Release a reference to a set of credentials, deleting them when the last ref
237  * is released.
238  *
239  * This takes a const pointer to a set of credentials because the credentials
240  * on task_struct are attached by const pointers to prevent accidental
241  * alteration of otherwise immutable credential sets.
242  */
243 static inline void put_cred(const struct cred *_cred)
244 {
245         struct cred *cred = (struct cred *) _cred;
246 
247         validate_creds(cred);
248         if (atomic_dec_and_test(&(cred)->usage))
249                 __put_cred(cred);
250 }
251 
252 /**
253  * current_cred - Access the current task's subjective credentials
254  *
255  * Access the subjective credentials of the current task.  RCU-safe,
256  * since nobody else can modify it.
257  */
258 #define current_cred() \
259         rcu_dereference_protected(current->cred, 1)
260 
261 /**
262  * __task_cred - Access a task's objective credentials
263  * @task: The task to query
264  *
265  * Access the objective credentials of a task.  The caller must hold the RCU
266  * readlock.
267  *
268  * The result of this function should not be passed directly to get_cred();
269  * rather get_task_cred() should be used instead.
270  */
271 #define __task_cred(task)       \
272         rcu_dereference((task)->real_cred)
273 
274 /**
275  * get_current_cred - Get the current task's subjective credentials
276  *
277  * Get the subjective credentials of the current task, pinning them so that
278  * they can't go away.  Accessing the current task's credentials directly is
279  * not permitted.
280  */
281 #define get_current_cred()                              \
282         (get_cred(current_cred()))
283 
284 /**
285  * get_current_user - Get the current task's user_struct
286  *
287  * Get the user record of the current task, pinning it so that it can't go
288  * away.
289  */
290 #define get_current_user()                              \
291 ({                                                      \
292         struct user_struct *__u;                        \
293         const struct cred *__cred;                      \
294         __cred = current_cred();                        \
295         __u = get_uid(__cred->user);                    \
296         __u;                                            \
297 })
298 
299 /**
300  * get_current_groups - Get the current task's supplementary group list
301  *
302  * Get the supplementary group list of the current task, pinning it so that it
303  * can't go away.
304  */
305 #define get_current_groups()                            \
306 ({                                                      \
307         struct group_info *__groups;                    \
308         const struct cred *__cred;                      \
309         __cred = current_cred();                        \
310         __groups = get_group_info(__cred->group_info);  \
311         __groups;                                       \
312 })
313 
314 #define task_cred_xxx(task, xxx)                        \
315 ({                                                      \
316         __typeof__(((struct cred *)NULL)->xxx) ___val;  \
317         rcu_read_lock();                                \
318         ___val = __task_cred((task))->xxx;              \
319         rcu_read_unlock();                              \
320         ___val;                                         \
321 })
322 
323 #define task_uid(task)          (task_cred_xxx((task), uid))
324 #define task_euid(task)         (task_cred_xxx((task), euid))
325 
326 #define current_cred_xxx(xxx)                   \
327 ({                                              \
328         current_cred()->xxx;                    \
329 })
330 
331 #define current_uid()           (current_cred_xxx(uid))
332 #define current_gid()           (current_cred_xxx(gid))
333 #define current_euid()          (current_cred_xxx(euid))
334 #define current_egid()          (current_cred_xxx(egid))
335 #define current_suid()          (current_cred_xxx(suid))
336 #define current_sgid()          (current_cred_xxx(sgid))
337 #define current_fsuid()         (current_cred_xxx(fsuid))
338 #define current_fsgid()         (current_cred_xxx(fsgid))
339 #define current_cap()           (current_cred_xxx(cap_effective))
340 #define current_user()          (current_cred_xxx(user))
341 #define current_security()      (current_cred_xxx(security))
342 
343 extern struct user_namespace init_user_ns;
344 #ifdef CONFIG_USER_NS
345 #define current_user_ns()       (current_cred_xxx(user_ns))
346 #else
347 #define current_user_ns()       (&init_user_ns)
348 #endif
349 
350 
351 #define current_uid_gid(_uid, _gid)             \
352 do {                                            \
353         const struct cred *__cred;              \
354         __cred = current_cred();                \
355         *(_uid) = __cred->uid;                  \
356         *(_gid) = __cred->gid;                  \
357 } while(0)
358 
359 #define current_euid_egid(_euid, _egid)         \
360 do {                                            \
361         const struct cred *__cred;              \
362         __cred = current_cred();                \
363         *(_euid) = __cred->euid;                \
364         *(_egid) = __cred->egid;                \
365 } while(0)
366 
367 #define current_fsuid_fsgid(_fsuid, _fsgid)     \
368 do {                                            \
369         const struct cred *__cred;              \
370         __cred = current_cred();                \
371         *(_fsuid) = __cred->fsuid;              \
372         *(_fsgid) = __cred->fsgid;              \
373 } while(0)
374 
375 #endif /* _LINUX_CRED_H */
376 

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