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

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