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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/init.h>
17 #include <linux/key.h>
18 #include <asm/atomic.h>
19
20 struct user_struct;
21 struct cred;
22 struct inode;
23
24 /*
25  * COW Supplementary groups list
26  */
27 #define NGROUPS_SMALL           32
28 #define NGROUPS_PER_BLOCK       ((unsigned int)(PAGE_SIZE / sizeof(gid_t)))
29
30 struct group_info {
31         atomic_t        usage;
32         int             ngroups;
33         int             nblocks;
34         gid_t           small_block[NGROUPS_SMALL];
35         gid_t           *blocks[0];
36 };
37
38 /**
39  * get_group_info - Get a reference to a group info structure
40  * @group_info: The group info to reference
41  *
42  * This gets a reference to a set of supplementary groups.
43  *
44  * If the caller is accessing a task's credentials, they must hold the RCU read
45  * lock when reading.
46  */
47 static inline struct group_info *get_group_info(struct group_info *gi)
48 {
49         atomic_inc(&gi->usage);
50         return gi;
51 }
52
53 /**
54  * put_group_info - Release a reference to a group info structure
55  * @group_info: The group info to release
56  */
57 #define put_group_info(group_info)                      \
58 do {                                                    \
59         if (atomic_dec_and_test(&(group_info)->usage))  \
60                 groups_free(group_info);                \
61 } while (0)
62
63 extern struct group_info *groups_alloc(int);
64 extern struct group_info init_groups;
65 extern void groups_free(struct group_info *);
66 extern int set_current_groups(struct group_info *);
67 extern int set_groups(struct cred *, struct group_info *);
68 extern int groups_search(const struct group_info *, gid_t);
69
70 /* access the groups "array" with this macro */
71 #define GROUP_AT(gi, i) \
72         ((gi)->blocks[(i) / NGROUPS_PER_BLOCK][(i) % NGROUPS_PER_BLOCK])
73
74 extern int in_group_p(gid_t);
75 extern int in_egroup_p(gid_t);
76
77 /*
78  * The common credentials for a thread group
79  * - shared by CLONE_THREAD
80  */
81 #ifdef CONFIG_KEYS
82 struct thread_group_cred {
83         atomic_t        usage;
84         pid_t           tgid;                   /* thread group process ID */
85         spinlock_t      lock;
86         struct key      *session_keyring;       /* keyring inherited over fork */
87         struct key      *process_keyring;       /* keyring private to this process */
88         struct rcu_head rcu;                    /* RCU deletion hook */
89 };
90 #endif
91
92 /*
93  * The security context of a task
94  *
95  * The parts of the context break down into two categories:
96  *
97  *  (1) The objective context of a task.  These parts are used when some other
98  *      task is attempting to affect this one.
99  *
100  *  (2) The subjective context.  These details are used when the task is acting
101  *      upon another object, be that a file, a task, a key or whatever.
102  *
103  * Note that some members of this structure belong to both categories - the
104  * LSM security pointer for instance.
105  *
106  * A task has two security pointers.  task->real_cred points to the objective
107  * context that defines that task's actual details.  The objective part of this
108  * context is used whenever that task is acted upon.
109  *
110  * task->cred points to the subjective context that defines the details of how
111  * that task is going to act upon another object.  This may be overridden
112  * temporarily to point to another security context, but normally points to the
113  * same context as task->real_cred.
114  */
115 struct cred {
116         atomic_t        usage;
117         uid_t           uid;            /* real UID of the task */
118         gid_t           gid;            /* real GID of the task */
119         uid_t           suid;           /* saved UID of the task */
120         gid_t           sgid;           /* saved GID of the task */
121         uid_t           euid;           /* effective UID of the task */
122         gid_t           egid;           /* effective GID of the task */
123         uid_t           fsuid;          /* UID for VFS ops */
124         gid_t           fsgid;          /* GID for VFS ops */
125         unsigned        securebits;     /* SUID-less security management */
126         kernel_cap_t    cap_inheritable; /* caps our children can inherit */
127         kernel_cap_t    cap_permitted;  /* caps we're permitted */
128         kernel_cap_t    cap_effective;  /* caps we can actually use */
129         kernel_cap_t    cap_bset;       /* capability bounding set */
130 #ifdef CONFIG_KEYS
131         unsigned char   jit_keyring;    /* default keyring to attach requested
132                                          * keys to */
133         struct key      *thread_keyring; /* keyring private to this thread */
134         struct key      *request_key_auth; /* assumed request_key authority */
135         struct thread_group_cred *tgcred; /* thread-group shared credentials */
136 #endif
137 #ifdef CONFIG_SECURITY
138         void            *security;      /* subjective LSM security */
139 #endif
140         struct user_struct *user;       /* real user ID subscription */
141         struct group_info *group_info;  /* supplementary groups for euid/fsgid */
142         struct rcu_head rcu;            /* RCU deletion hook */
143 };
144
145 extern void __put_cred(struct cred *);
146 extern int copy_creds(struct task_struct *, unsigned long);
147 extern struct cred *prepare_creds(void);
148 extern struct cred *prepare_exec_creds(void);
149 extern struct cred *prepare_usermodehelper_creds(void);
150 extern int commit_creds(struct cred *);
151 extern void abort_creds(struct cred *);
152 extern const struct cred *override_creds(const struct cred *);
153 extern void revert_creds(const struct cred *);
154 extern struct cred *prepare_kernel_cred(struct task_struct *);
155 extern int change_create_files_as(struct cred *, struct inode *);
156 extern int set_security_override(struct cred *, u32);
157 extern int set_security_override_from_ctx(struct cred *, const char *);
158 extern int set_create_files_as(struct cred *, struct inode *);
159 extern void __init cred_init(void);
160
161 /**
162  * get_new_cred - Get a reference on a new set of credentials
163  * @cred: The new credentials to reference
164  *
165  * Get a reference on the specified set of new credentials.  The caller must
166  * release the reference.
167  */
168 static inline struct cred *get_new_cred(struct cred *cred)
169 {
170         atomic_inc(&cred->usage);
171         return cred;
172 }
173
174 /**
175  * get_cred - Get a reference on a set of credentials
176  * @cred: The credentials to reference
177  *
178  * Get a reference on the specified set of credentials.  The caller must
179  * release the reference.
180  *
181  * This is used to deal with a committed set of credentials.  Although the
182  * pointer is const, this will temporarily discard the const and increment the
183  * usage count.  The purpose of this is to attempt to catch at compile time the
184  * accidental alteration of a set of credentials that should be considered
185  * immutable.
186  */
187 static inline const struct cred *get_cred(const struct cred *cred)
188 {
189         return get_new_cred((struct cred *) cred);
190 }
191
192 /**
193  * put_cred - Release a reference to a set of credentials
194  * @cred: The credentials to release
195  *
196  * Release a reference to a set of credentials, deleting them when the last ref
197  * is released.
198  *
199  * This takes a const pointer to a set of credentials because the credentials
200  * on task_struct are attached by const pointers to prevent accidental
201  * alteration of otherwise immutable credential sets.
202  */
203 static inline void put_cred(const struct cred *_cred)
204 {
205         struct cred *cred = (struct cred *) _cred;
206
207         BUG_ON(atomic_read(&(cred)->usage) <= 0);
208         if (atomic_dec_and_test(&(cred)->usage))
209                 __put_cred(cred);
210 }
211
212 /**
213  * current_cred - Access the current task's subjective credentials
214  *
215  * Access the subjective credentials of the current task.
216  */
217 #define current_cred() \
218         (current->cred)
219
220 /**
221  * __task_cred - Access a task's objective credentials
222  * @task: The task to query
223  *
224  * Access the objective credentials of a task.  The caller must hold the RCU
225  * readlock.
226  *
227  * The caller must make sure task doesn't go away, either by holding a ref on
228  * task or by holding tasklist_lock to prevent it from being unlinked.
229  */
230 #define __task_cred(task) \
231         ((const struct cred *)(rcu_dereference((task)->real_cred)))
232
233 /**
234  * get_task_cred - Get another task's objective credentials
235  * @task: The task to query
236  *
237  * Get the objective credentials of a task, pinning them so that they can't go
238  * away.  Accessing a task's credentials directly is not permitted.
239  *
240  * The caller must make sure task doesn't go away, either by holding a ref on
241  * task or by holding tasklist_lock to prevent it from being unlinked.
242  */
243 #define get_task_cred(task)                             \
244 ({                                                      \
245         struct cred *__cred;                            \
246         rcu_read_lock();                                \
247         __cred = (struct cred *) __task_cred((task));   \
248         get_cred(__cred);                               \
249         rcu_read_unlock();                              \
250         __cred;                                         \
251 })
252
253 /**
254  * get_current_cred - Get the current task's subjective credentials
255  *
256  * Get the subjective credentials of the current task, pinning them so that
257  * they can't go away.  Accessing the current task's credentials directly is
258  * not permitted.
259  */
260 #define get_current_cred()                              \
261         (get_cred(current_cred()))
262
263 /**
264  * get_current_user - Get the current task's user_struct
265  *
266  * Get the user record of the current task, pinning it so that it can't go
267  * away.
268  */
269 #define get_current_user()                              \
270 ({                                                      \
271         struct user_struct *__u;                        \
272         struct cred *__cred;                            \
273         __cred = (struct cred *) current_cred();        \
274         __u = get_uid(__cred->user);                    \
275         __u;                                            \
276 })
277
278 /**
279  * get_current_groups - Get the current task's supplementary group list
280  *
281  * Get the supplementary group list of the current task, pinning it so that it
282  * can't go away.
283  */
284 #define get_current_groups()                            \
285 ({                                                      \
286         struct group_info *__groups;                    \
287         struct cred *__cred;                            \
288         __cred = (struct cred *) current_cred();        \
289         __groups = get_group_info(__cred->group_info);  \
290         __groups;                                       \
291 })
292
293 #define task_cred_xxx(task, xxx)                        \
294 ({                                                      \
295         __typeof__(((struct cred *)NULL)->xxx) ___val;  \
296         rcu_read_lock();                                \
297         ___val = __task_cred((task))->xxx;              \
298         rcu_read_unlock();                              \
299         ___val;                                         \
300 })
301
302 #define task_uid(task)          (task_cred_xxx((task), uid))
303 #define task_euid(task)         (task_cred_xxx((task), euid))
304
305 #define current_cred_xxx(xxx)                   \
306 ({                                              \
307         current->cred->xxx;                     \
308 })
309
310 #define current_uid()           (current_cred_xxx(uid))
311 #define current_gid()           (current_cred_xxx(gid))
312 #define current_euid()          (current_cred_xxx(euid))
313 #define current_egid()          (current_cred_xxx(egid))
314 #define current_suid()          (current_cred_xxx(suid))
315 #define current_sgid()          (current_cred_xxx(sgid))
316 #define current_fsuid()         (current_cred_xxx(fsuid))
317 #define current_fsgid()         (current_cred_xxx(fsgid))
318 #define current_cap()           (current_cred_xxx(cap_effective))
319 #define current_user()          (current_cred_xxx(user))
320 #define current_user_ns()       (current_cred_xxx(user)->user_ns)
321 #define current_security()      (current_cred_xxx(security))
322
323 #define current_uid_gid(_uid, _gid)             \
324 do {                                            \
325         const struct cred *__cred;              \
326         __cred = current_cred();                \
327         *(_uid) = __cred->uid;                  \
328         *(_gid) = __cred->gid;                  \
329 } while(0)
330
331 #define current_euid_egid(_euid, _egid)         \
332 do {                                            \
333         const struct cred *__cred;              \
334         __cred = current_cred();                \
335         *(_euid) = __cred->euid;                \
336         *(_egid) = __cred->egid;                \
337 } while(0)
338
339 #define current_fsuid_fsgid(_fsuid, _fsgid)     \
340 do {                                            \
341         const struct cred *__cred;              \
342         __cred = current_cred();                \
343         *(_fsuid) = __cred->fsuid;              \
344         *(_fsgid) = __cred->fsgid;              \
345 } while(0)
346
347 #endif /* _LINUX_CRED_H */