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1 /* Credentials management - see Documentation/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/key.h>
17 #include <asm/atomic.h>
18
19 struct user_struct;
20 struct cred;
21 struct inode;
22
23 /*
24  * COW Supplementary groups list
25  */
26 #define NGROUPS_SMALL           32
27 #define NGROUPS_PER_BLOCK       ((unsigned int)(PAGE_SIZE / sizeof(gid_t)))
28
29 struct group_info {
30         atomic_t        usage;
31         int             ngroups;
32         int             nblocks;
33         gid_t           small_block[NGROUPS_SMALL];
34         gid_t           *blocks[0];
35 };
36
37 /**
38  * get_group_info - Get a reference to a group info structure
39  * @group_info: The group info to reference
40  *
41  * This gets a reference to a set of supplementary groups.
42  *
43  * If the caller is accessing a task's credentials, they must hold the RCU read
44  * lock when reading.
45  */
46 static inline struct group_info *get_group_info(struct group_info *gi)
47 {
48         atomic_inc(&gi->usage);
49         return gi;
50 }
51
52 /**
53  * put_group_info - Release a reference to a group info structure
54  * @group_info: The group info to release
55  */
56 #define put_group_info(group_info)                      \
57 do {                                                    \
58         if (atomic_dec_and_test(&(group_info)->usage))  \
59                 groups_free(group_info);                \
60 } while (0)
61
62 extern struct group_info *groups_alloc(int);
63 extern struct group_info init_groups;
64 extern void groups_free(struct group_info *);
65 extern int set_current_groups(struct group_info *);
66 extern int set_groups(struct cred *, struct group_info *);
67 extern int groups_search(const struct group_info *, gid_t);
68
69 /* access the groups "array" with this macro */
70 #define GROUP_AT(gi, i) \
71         ((gi)->blocks[(i) / NGROUPS_PER_BLOCK][(i) % NGROUPS_PER_BLOCK])
72
73 extern int in_group_p(gid_t);
74 extern int in_egroup_p(gid_t);
75
76 /*
77  * The common credentials for a thread group
78  * - shared by CLONE_THREAD
79  */
80 #ifdef CONFIG_KEYS
81 struct thread_group_cred {
82         atomic_t        usage;
83         pid_t           tgid;                   /* thread group process ID */
84         spinlock_t      lock;
85         struct key      *session_keyring;       /* keyring inherited over fork */
86         struct key      *process_keyring;       /* keyring private to this process */
87         struct rcu_head rcu;                    /* RCU deletion hook */
88 };
89 #endif
90
91 /*
92  * The security context of a task
93  *
94  * The parts of the context break down into two categories:
95  *
96  *  (1) The objective context of a task.  These parts are used when some other
97  *      task is attempting to affect this one.
98  *
99  *  (2) The subjective context.  These details are used when the task is acting
100  *      upon another object, be that a file, a task, a key or whatever.
101  *
102  * Note that some members of this structure belong to both categories - the
103  * LSM security pointer for instance.
104  *
105  * A task has two security pointers.  task->real_cred points to the objective
106  * context that defines that task's actual details.  The objective part of this
107  * context is used whenever that task is acted upon.
108  *
109  * task->cred points to the subjective context that defines the details of how
110  * that task is going to act upon another object.  This may be overridden
111  * temporarily to point to another security context, but normally points to the
112  * same context as task->real_cred.
113  */
114 struct cred {
115         atomic_t        usage;
116         uid_t           uid;            /* real UID of the task */
117         gid_t           gid;            /* real GID of the task */
118         uid_t           suid;           /* saved UID of the task */
119         gid_t           sgid;           /* saved GID of the task */
120         uid_t           euid;           /* effective UID of the task */
121         gid_t           egid;           /* effective GID of the task */
122         uid_t           fsuid;          /* UID for VFS ops */
123         gid_t           fsgid;          /* GID for VFS ops */
124         unsigned        securebits;     /* SUID-less security management */
125         kernel_cap_t    cap_inheritable; /* caps our children can inherit */
126         kernel_cap_t    cap_permitted;  /* caps we're permitted */
127         kernel_cap_t    cap_effective;  /* caps we can actually use */
128         kernel_cap_t    cap_bset;       /* capability bounding set */
129 #ifdef CONFIG_KEYS
130         unsigned char   jit_keyring;    /* default keyring to attach requested
131                                          * keys to */
132         struct key      *thread_keyring; /* keyring private to this thread */
133         struct key      *request_key_auth; /* assumed request_key authority */
134         struct thread_group_cred *tgcred; /* thread-group shared credentials */
135 #endif
136 #ifdef CONFIG_SECURITY
137         void            *security;      /* subjective LSM security */
138 #endif
139         struct user_struct *user;       /* real user ID subscription */
140         struct group_info *group_info;  /* supplementary groups for euid/fsgid */
141         struct rcu_head rcu;            /* RCU deletion hook */
142 };
143
144 extern void __put_cred(struct cred *);
145 extern int copy_creds(struct task_struct *, unsigned long);
146 extern struct cred *prepare_creds(void);
147 extern struct cred *prepare_exec_creds(void);
148 extern struct cred *prepare_usermodehelper_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  * get_new_cred - Get a reference on a new set of credentials
162  * @cred: The new credentials to reference
163  *
164  * Get a reference on the specified set of new credentials.  The caller must
165  * release the reference.
166  */
167 static inline struct cred *get_new_cred(struct cred *cred)
168 {
169         atomic_inc(&cred->usage);
170         return cred;
171 }
172
173 /**
174  * get_cred - Get a reference on a set of credentials
175  * @cred: The credentials to reference
176  *
177  * Get a reference on the specified set of credentials.  The caller must
178  * release the reference.
179  *
180  * This is used to deal with a committed set of credentials.  Although the
181  * pointer is const, this will temporarily discard the const and increment the
182  * usage count.  The purpose of this is to attempt to catch at compile time the
183  * accidental alteration of a set of credentials that should be considered
184  * immutable.
185  */
186 static inline const struct cred *get_cred(const struct cred *cred)
187 {
188         return get_new_cred((struct cred *) cred);
189 }
190
191 /**
192  * put_cred - Release a reference to a set of credentials
193  * @cred: The credentials to release
194  *
195  * Release a reference to a set of credentials, deleting them when the last ref
196  * is released.
197  *
198  * This takes a const pointer to a set of credentials because the credentials
199  * on task_struct are attached by const pointers to prevent accidental
200  * alteration of otherwise immutable credential sets.
201  */
202 static inline void put_cred(const struct cred *_cred)
203 {
204         struct cred *cred = (struct cred *) _cred;
205
206         BUG_ON(atomic_read(&(cred)->usage) <= 0);
207         if (atomic_dec_and_test(&(cred)->usage))
208                 __put_cred(cred);
209 }
210
211 /**
212  * current_cred - Access the current task's subjective credentials
213  *
214  * Access the subjective credentials of the current task.
215  */
216 #define current_cred() \
217         (current->cred)
218
219 /**
220  * __task_cred - Access a task's objective credentials
221  * @task: The task to query
222  *
223  * Access the objective credentials of a task.  The caller must hold the RCU
224  * readlock.
225  *
226  * The caller must make sure task doesn't go away, either by holding a ref on
227  * task or by holding tasklist_lock to prevent it from being unlinked.
228  */
229 #define __task_cred(task) \
230         ((const struct cred *)(rcu_dereference((task)->real_cred)))
231
232 /**
233  * get_task_cred - Get another task's objective credentials
234  * @task: The task to query
235  *
236  * Get the objective credentials of a task, pinning them so that they can't go
237  * away.  Accessing a task's credentials directly is not permitted.
238  *
239  * The caller must make sure task doesn't go away, either by holding a ref on
240  * task or by holding tasklist_lock to prevent it from being unlinked.
241  */
242 #define get_task_cred(task)                             \
243 ({                                                      \
244         struct cred *__cred;                            \
245         rcu_read_lock();                                \
246         __cred = (struct cred *) __task_cred((task));   \
247         get_cred(__cred);                               \
248         rcu_read_unlock();                              \
249         __cred;                                         \
250 })
251
252 /**
253  * get_current_cred - Get the current task's subjective credentials
254  *
255  * Get the subjective credentials of the current task, pinning them so that
256  * they can't go away.  Accessing the current task's credentials directly is
257  * not permitted.
258  */
259 #define get_current_cred()                              \
260         (get_cred(current_cred()))
261
262 /**
263  * get_current_user - Get the current task's user_struct
264  *
265  * Get the user record of the current task, pinning it so that it can't go
266  * away.
267  */
268 #define get_current_user()                              \
269 ({                                                      \
270         struct user_struct *__u;                        \
271         struct cred *__cred;                            \
272         __cred = (struct cred *) current_cred();        \
273         __u = get_uid(__cred->user);                    \
274         __u;                                            \
275 })
276
277 /**
278  * get_current_groups - Get the current task's supplementary group list
279  *
280  * Get the supplementary group list of the current task, pinning it so that it
281  * can't go away.
282  */
283 #define get_current_groups()                            \
284 ({                                                      \
285         struct group_info *__groups;                    \
286         struct cred *__cred;                            \
287         __cred = (struct cred *) current_cred();        \
288         __groups = get_group_info(__cred->group_info);  \
289         __groups;                                       \
290 })
291
292 #define task_cred_xxx(task, xxx)                        \
293 ({                                                      \
294         __typeof__(((struct cred *)NULL)->xxx) ___val;  \
295         rcu_read_lock();                                \
296         ___val = __task_cred((task))->xxx;              \
297         rcu_read_unlock();                              \
298         ___val;                                         \
299 })
300
301 #define task_uid(task)          (task_cred_xxx((task), uid))
302 #define task_euid(task)         (task_cred_xxx((task), euid))
303
304 #define current_cred_xxx(xxx)                   \
305 ({                                              \
306         current->cred->xxx;                     \
307 })
308
309 #define current_uid()           (current_cred_xxx(uid))
310 #define current_gid()           (current_cred_xxx(gid))
311 #define current_euid()          (current_cred_xxx(euid))
312 #define current_egid()          (current_cred_xxx(egid))
313 #define current_suid()          (current_cred_xxx(suid))
314 #define current_sgid()          (current_cred_xxx(sgid))
315 #define current_fsuid()         (current_cred_xxx(fsuid))
316 #define current_fsgid()         (current_cred_xxx(fsgid))
317 #define current_cap()           (current_cred_xxx(cap_effective))
318 #define current_user()          (current_cred_xxx(user))
319 #define current_user_ns()       (current_cred_xxx(user)->user_ns)
320 #define current_security()      (current_cred_xxx(security))
321
322 #define current_uid_gid(_uid, _gid)             \
323 do {                                            \
324         const struct cred *__cred;              \
325         __cred = current_cred();                \
326         *(_uid) = __cred->uid;                  \
327         *(_gid) = __cred->gid;                  \
328 } while(0)
329
330 #define current_euid_egid(_euid, _egid)         \
331 do {                                            \
332         const struct cred *__cred;              \
333         __cred = current_cred();                \
334         *(_euid) = __cred->euid;                \
335         *(_egid) = __cred->egid;                \
336 } while(0)
337
338 #define current_fsuid_fsgid(_fsuid, _fsgid)     \
339 do {                                            \
340         const struct cred *__cred;              \
341         __cred = current_cred();                \
342         *(_fsuid) = __cred->fsuid;              \
343         *(_fsgid) = __cred->fsgid;              \
344 } while(0)
345
346 #endif /* _LINUX_CRED_H */