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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 struct group_info {
 30         atomic_t        usage;
 31         int             ngroups;
 32         kgid_t          gid[0];
 33 };
 34 
 35 /**
 36  * get_group_info - Get a reference to a group info structure
 37  * @group_info: The group info to reference
 38  *
 39  * This gets a reference to a set of supplementary groups.
 40  *
 41  * If the caller is accessing a task's credentials, they must hold the RCU read
 42  * lock when reading.
 43  */
 44 static inline struct group_info *get_group_info(struct group_info *gi)
 45 {
 46         atomic_inc(&gi->usage);
 47         return gi;
 48 }
 49 
 50 /**
 51  * put_group_info - Release a reference to a group info structure
 52  * @group_info: The group info to release
 53  */
 54 #define put_group_info(group_info)                      \
 55 do {                                                    \
 56         if (atomic_dec_and_test(&(group_info)->usage))  \
 57                 groups_free(group_info);                \
 58 } while (0)
 59 
 60 extern struct group_info init_groups;
 61 #ifdef CONFIG_MULTIUSER
 62 extern struct group_info *groups_alloc(int);
 63 extern void groups_free(struct group_info *);
 64 
 65 extern int in_group_p(kgid_t);
 66 extern int in_egroup_p(kgid_t);
 67 #else
 68 static inline void groups_free(struct group_info *group_info)
 69 {
 70 }
 71 
 72 static inline int in_group_p(kgid_t grp)
 73 {
 74         return 1;
 75 }
 76 static inline int in_egroup_p(kgid_t grp)
 77 {
 78         return 1;
 79 }
 80 #endif
 81 extern int set_current_groups(struct group_info *);
 82 extern void set_groups(struct cred *, struct group_info *);
 83 extern int groups_search(const struct group_info *, kgid_t);
 84 extern bool may_setgroups(void);
 85 
 86 /*
 87  * The security context of a task
 88  *
 89  * The parts of the context break down into two categories:
 90  *
 91  *  (1) The objective context of a task.  These parts are used when some other
 92  *      task is attempting to affect this one.
 93  *
 94  *  (2) The subjective context.  These details are used when the task is acting
 95  *      upon another object, be that a file, a task, a key or whatever.
 96  *
 97  * Note that some members of this structure belong to both categories - the
 98  * LSM security pointer for instance.
 99  *
100  * A task has two security pointers.  task->real_cred points to the objective
101  * context that defines that task's actual details.  The objective part of this
102  * context is used whenever that task is acted upon.
103  *
104  * task->cred points to the subjective context that defines the details of how
105  * that task is going to act upon another object.  This may be overridden
106  * temporarily to point to another security context, but normally points to the
107  * same context as task->real_cred.
108  */
109 struct cred {
110         atomic_t        usage;
111 #ifdef CONFIG_DEBUG_CREDENTIALS
112         atomic_t        subscribers;    /* number of processes subscribed */
113         void            *put_addr;
114         unsigned        magic;
115 #define CRED_MAGIC      0x43736564
116 #define CRED_MAGIC_DEAD 0x44656144
117 #endif
118         kuid_t          uid;            /* real UID of the task */
119         kgid_t          gid;            /* real GID of the task */
120         kuid_t          suid;           /* saved UID of the task */
121         kgid_t          sgid;           /* saved GID of the task */
122         kuid_t          euid;           /* effective UID of the task */
123         kgid_t          egid;           /* effective GID of the task */
124         kuid_t          fsuid;          /* UID for VFS ops */
125         kgid_t          fsgid;          /* GID for VFS ops */
126         unsigned        securebits;     /* SUID-less security management */
127         kernel_cap_t    cap_inheritable; /* caps our children can inherit */
128         kernel_cap_t    cap_permitted;  /* caps we're permitted */
129         kernel_cap_t    cap_effective;  /* caps we can actually use */
130         kernel_cap_t    cap_bset;       /* capability bounding set */
131         kernel_cap_t    cap_ambient;    /* Ambient capability set */
132 #ifdef CONFIG_KEYS
133         unsigned char   jit_keyring;    /* default keyring to attach requested
134                                          * keys to */
135         struct key __rcu *session_keyring; /* keyring inherited over fork */
136         struct key      *process_keyring; /* keyring private to this process */
137         struct key      *thread_keyring; /* keyring private to this thread */
138         struct key      *request_key_auth; /* assumed request_key authority */
139 #endif
140 #ifdef CONFIG_SECURITY
141         void            *security;      /* subjective LSM security */
142 #endif
143         struct user_struct *user;       /* real user ID subscription */
144         struct user_namespace *user_ns; /* user_ns the caps and keyrings are relative to. */
145         struct group_info *group_info;  /* supplementary groups for euid/fsgid */
146         struct rcu_head rcu;            /* RCU deletion hook */
147 };
148 
149 extern void __put_cred(struct cred *);
150 extern void exit_creds(struct task_struct *);
151 extern int copy_creds(struct task_struct *, unsigned long);
152 extern const struct cred *get_task_cred(struct task_struct *);
153 extern struct cred *cred_alloc_blank(void);
154 extern struct cred *prepare_creds(void);
155 extern struct cred *prepare_exec_creds(void);
156 extern int commit_creds(struct cred *);
157 extern void abort_creds(struct cred *);
158 extern const struct cred *override_creds(const struct cred *);
159 extern void revert_creds(const struct cred *);
160 extern struct cred *prepare_kernel_cred(struct task_struct *);
161 extern int change_create_files_as(struct cred *, struct inode *);
162 extern int set_security_override(struct cred *, u32);
163 extern int set_security_override_from_ctx(struct cred *, const char *);
164 extern int set_create_files_as(struct cred *, struct inode *);
165 extern void __init cred_init(void);
166 
167 /*
168  * check for validity of credentials
169  */
170 #ifdef CONFIG_DEBUG_CREDENTIALS
171 extern void __invalid_creds(const struct cred *, const char *, unsigned);
172 extern void __validate_process_creds(struct task_struct *,
173                                      const char *, unsigned);
174 
175 extern bool creds_are_invalid(const struct cred *cred);
176 
177 static inline void __validate_creds(const struct cred *cred,
178                                     const char *file, unsigned line)
179 {
180         if (unlikely(creds_are_invalid(cred)))
181                 __invalid_creds(cred, file, line);
182 }
183 
184 #define validate_creds(cred)                            \
185 do {                                                    \
186         __validate_creds((cred), __FILE__, __LINE__);   \
187 } while(0)
188 
189 #define validate_process_creds()                                \
190 do {                                                            \
191         __validate_process_creds(current, __FILE__, __LINE__);  \
192 } while(0)
193 
194 extern void validate_creds_for_do_exit(struct task_struct *);
195 #else
196 static inline void validate_creds(const struct cred *cred)
197 {
198 }
199 static inline void validate_creds_for_do_exit(struct task_struct *tsk)
200 {
201 }
202 static inline void validate_process_creds(void)
203 {
204 }
205 #endif
206 
207 static inline bool cap_ambient_invariant_ok(const struct cred *cred)
208 {
209         return cap_issubset(cred->cap_ambient,
210                             cap_intersect(cred->cap_permitted,
211                                           cred->cap_inheritable));
212 }
213 
214 /**
215  * get_new_cred - Get a reference on a new set of credentials
216  * @cred: The new credentials to reference
217  *
218  * Get a reference on the specified set of new credentials.  The caller must
219  * release the reference.
220  */
221 static inline struct cred *get_new_cred(struct cred *cred)
222 {
223         atomic_inc(&cred->usage);
224         return cred;
225 }
226 
227 /**
228  * get_cred - Get a reference on a set of credentials
229  * @cred: The credentials to reference
230  *
231  * Get a reference on the specified set of credentials.  The caller must
232  * release the reference.
233  *
234  * This is used to deal with a committed set of credentials.  Although the
235  * pointer is const, this will temporarily discard the const and increment the
236  * usage count.  The purpose of this is to attempt to catch at compile time the
237  * accidental alteration of a set of credentials that should be considered
238  * immutable.
239  */
240 static inline const struct cred *get_cred(const struct cred *cred)
241 {
242         struct cred *nonconst_cred = (struct cred *) cred;
243         validate_creds(cred);
244         return get_new_cred(nonconst_cred);
245 }
246 
247 /**
248  * put_cred - Release a reference to a set of credentials
249  * @cred: The credentials to release
250  *
251  * Release a reference to a set of credentials, deleting them when the last ref
252  * is released.
253  *
254  * This takes a const pointer to a set of credentials because the credentials
255  * on task_struct are attached by const pointers to prevent accidental
256  * alteration of otherwise immutable credential sets.
257  */
258 static inline void put_cred(const struct cred *_cred)
259 {
260         struct cred *cred = (struct cred *) _cred;
261 
262         validate_creds(cred);
263         if (atomic_dec_and_test(&(cred)->usage))
264                 __put_cred(cred);
265 }
266 
267 /**
268  * current_cred - Access the current task's subjective credentials
269  *
270  * Access the subjective credentials of the current task.  RCU-safe,
271  * since nobody else can modify it.
272  */
273 #define current_cred() \
274         rcu_dereference_protected(current->cred, 1)
275 
276 /**
277  * current_real_cred - Access the current task's objective credentials
278  *
279  * Access the objective credentials of the current task.  RCU-safe,
280  * since nobody else can modify it.
281  */
282 #define current_real_cred() \
283         rcu_dereference_protected(current->real_cred, 1)
284 
285 /**
286  * __task_cred - Access a task's objective credentials
287  * @task: The task to query
288  *
289  * Access the objective credentials of a task.  The caller must hold the RCU
290  * readlock.
291  *
292  * The result of this function should not be passed directly to get_cred();
293  * rather get_task_cred() should be used instead.
294  */
295 #define __task_cred(task)       \
296         rcu_dereference((task)->real_cred)
297 
298 /**
299  * get_current_cred - Get the current task's subjective credentials
300  *
301  * Get the subjective credentials of the current task, pinning them so that
302  * they can't go away.  Accessing the current task's credentials directly is
303  * not permitted.
304  */
305 #define get_current_cred()                              \
306         (get_cred(current_cred()))
307 
308 /**
309  * get_current_user - Get the current task's user_struct
310  *
311  * Get the user record of the current task, pinning it so that it can't go
312  * away.
313  */
314 #define get_current_user()                              \
315 ({                                                      \
316         struct user_struct *__u;                        \
317         const struct cred *__cred;                      \
318         __cred = current_cred();                        \
319         __u = get_uid(__cred->user);                    \
320         __u;                                            \
321 })
322 
323 /**
324  * get_current_groups - Get the current task's supplementary group list
325  *
326  * Get the supplementary group list of the current task, pinning it so that it
327  * can't go away.
328  */
329 #define get_current_groups()                            \
330 ({                                                      \
331         struct group_info *__groups;                    \
332         const struct cred *__cred;                      \
333         __cred = current_cred();                        \
334         __groups = get_group_info(__cred->group_info);  \
335         __groups;                                       \
336 })
337 
338 #define task_cred_xxx(task, xxx)                        \
339 ({                                                      \
340         __typeof__(((struct cred *)NULL)->xxx) ___val;  \
341         rcu_read_lock();                                \
342         ___val = __task_cred((task))->xxx;              \
343         rcu_read_unlock();                              \
344         ___val;                                         \
345 })
346 
347 #define task_uid(task)          (task_cred_xxx((task), uid))
348 #define task_euid(task)         (task_cred_xxx((task), euid))
349 
350 #define current_cred_xxx(xxx)                   \
351 ({                                              \
352         current_cred()->xxx;                    \
353 })
354 
355 #define current_uid()           (current_cred_xxx(uid))
356 #define current_gid()           (current_cred_xxx(gid))
357 #define current_euid()          (current_cred_xxx(euid))
358 #define current_egid()          (current_cred_xxx(egid))
359 #define current_suid()          (current_cred_xxx(suid))
360 #define current_sgid()          (current_cred_xxx(sgid))
361 #define current_fsuid()         (current_cred_xxx(fsuid))
362 #define current_fsgid()         (current_cred_xxx(fsgid))
363 #define current_cap()           (current_cred_xxx(cap_effective))
364 #define current_user()          (current_cred_xxx(user))
365 #define current_security()      (current_cred_xxx(security))
366 
367 extern struct user_namespace init_user_ns;
368 #ifdef CONFIG_USER_NS
369 #define current_user_ns()       (current_cred_xxx(user_ns))
370 #else
371 static inline struct user_namespace *current_user_ns(void)
372 {
373         return &init_user_ns;
374 }
375 #endif
376 
377 
378 #define current_uid_gid(_uid, _gid)             \
379 do {                                            \
380         const struct cred *__cred;              \
381         __cred = current_cred();                \
382         *(_uid) = __cred->uid;                  \
383         *(_gid) = __cred->gid;                  \
384 } while(0)
385 
386 #define current_euid_egid(_euid, _egid)         \
387 do {                                            \
388         const struct cred *__cred;              \
389         __cred = current_cred();                \
390         *(_euid) = __cred->euid;                \
391         *(_egid) = __cred->egid;                \
392 } while(0)
393 
394 #define current_fsuid_fsgid(_fsuid, _fsgid)     \
395 do {                                            \
396         const struct cred *__cred;              \
397         __cred = current_cred();                \
398         *(_fsuid) = __cred->fsuid;              \
399         *(_fsgid) = __cred->fsgid;              \
400 } while(0)
401 
402 #endif /* _LINUX_CRED_H */
403 

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