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

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