CRED: Make execve() take advantage of copy-on-write credentials
[linux-3.10.git] / include / linux / cred.h
1 /* Credentials management
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
22 /*
23  * COW Supplementary groups list
24  */
25 #define NGROUPS_SMALL           32
26 #define NGROUPS_PER_BLOCK       ((unsigned int)(PAGE_SIZE / sizeof(gid_t)))
27
28 struct group_info {
29         atomic_t        usage;
30         int             ngroups;
31         int             nblocks;
32         gid_t           small_block[NGROUPS_SMALL];
33         gid_t           *blocks[0];
34 };
35
36 /**
37  * get_group_info - Get a reference to a group info structure
38  * @group_info: The group info to reference
39  *
40  * This gets a reference to a set of supplementary groups.
41  *
42  * If the caller is accessing a task's credentials, they must hold the RCU read
43  * lock when reading.
44  */
45 static inline struct group_info *get_group_info(struct group_info *gi)
46 {
47         atomic_inc(&gi->usage);
48         return gi;
49 }
50
51 /**
52  * put_group_info - Release a reference to a group info structure
53  * @group_info: The group info to release
54  */
55 #define put_group_info(group_info)                      \
56 do {                                                    \
57         if (atomic_dec_and_test(&(group_info)->usage))  \
58                 groups_free(group_info);                \
59 } while (0)
60
61 extern struct group_info *groups_alloc(int);
62 extern void groups_free(struct group_info *);
63 extern int set_current_groups(struct group_info *);
64 extern int set_groups(struct cred *, struct group_info *);
65 extern int groups_search(const struct group_info *, gid_t);
66
67 /* access the groups "array" with this macro */
68 #define GROUP_AT(gi, i) \
69         ((gi)->blocks[(i) / NGROUPS_PER_BLOCK][(i) % NGROUPS_PER_BLOCK])
70
71 extern int in_group_p(gid_t);
72 extern int in_egroup_p(gid_t);
73
74 /*
75  * The common credentials for a thread group
76  * - shared by CLONE_THREAD
77  */
78 #ifdef CONFIG_KEYS
79 struct thread_group_cred {
80         atomic_t        usage;
81         pid_t           tgid;                   /* thread group process ID */
82         spinlock_t      lock;
83         struct key      *session_keyring;       /* keyring inherited over fork */
84         struct key      *process_keyring;       /* keyring private to this process */
85         struct rcu_head rcu;                    /* RCU deletion hook */
86 };
87 #endif
88
89 /*
90  * The security context of a task
91  *
92  * The parts of the context break down into two categories:
93  *
94  *  (1) The objective context of a task.  These parts are used when some other
95  *      task is attempting to affect this one.
96  *
97  *  (2) The subjective context.  These details are used when the task is acting
98  *      upon another object, be that a file, a task, a key or whatever.
99  *
100  * Note that some members of this structure belong to both categories - the
101  * LSM security pointer for instance.
102  *
103  * A task has two security pointers.  task->real_cred points to the objective
104  * context that defines that task's actual details.  The objective part of this
105  * context is used whenever that task is acted upon.
106  *
107  * task->cred points to the subjective context that defines the details of how
108  * that task is going to act upon another object.  This may be overridden
109  * temporarily to point to another security context, but normally points to the
110  * same context as task->real_cred.
111  */
112 struct cred {
113         atomic_t        usage;
114         uid_t           uid;            /* real UID of the task */
115         gid_t           gid;            /* real GID of the task */
116         uid_t           suid;           /* saved UID of the task */
117         gid_t           sgid;           /* saved GID of the task */
118         uid_t           euid;           /* effective UID of the task */
119         gid_t           egid;           /* effective GID of the task */
120         uid_t           fsuid;          /* UID for VFS ops */
121         gid_t           fsgid;          /* GID for VFS ops */
122         unsigned        securebits;     /* SUID-less security management */
123         kernel_cap_t    cap_inheritable; /* caps our children can inherit */
124         kernel_cap_t    cap_permitted;  /* caps we're permitted */
125         kernel_cap_t    cap_effective;  /* caps we can actually use */
126         kernel_cap_t    cap_bset;       /* capability bounding set */
127 #ifdef CONFIG_KEYS
128         unsigned char   jit_keyring;    /* default keyring to attach requested
129                                          * keys to */
130         struct key      *thread_keyring; /* keyring private to this thread */
131         struct key      *request_key_auth; /* assumed request_key authority */
132         struct thread_group_cred *tgcred; /* thread-group shared credentials */
133 #endif
134 #ifdef CONFIG_SECURITY
135         void            *security;      /* subjective LSM security */
136 #endif
137         struct user_struct *user;       /* real user ID subscription */
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 int copy_creds(struct task_struct *, unsigned long);
144 extern struct cred *prepare_creds(void);
145 extern struct cred *prepare_exec_creds(void);
146 extern struct cred *prepare_usermodehelper_creds(void);
147 extern int commit_creds(struct cred *);
148 extern void abort_creds(struct cred *);
149 extern const struct cred *override_creds(const struct cred *) __deprecated;
150 extern void revert_creds(const struct cred *) __deprecated;
151 extern void __init cred_init(void);
152
153 /**
154  * get_new_cred - Get a reference on a new set of credentials
155  * @cred: The new credentials to reference
156  *
157  * Get a reference on the specified set of new credentials.  The caller must
158  * release the reference.
159  */
160 static inline struct cred *get_new_cred(struct cred *cred)
161 {
162         atomic_inc(&cred->usage);
163         return cred;
164 }
165
166 /**
167  * get_cred - Get a reference on a set of credentials
168  * @cred: The credentials to reference
169  *
170  * Get a reference on the specified set of credentials.  The caller must
171  * release the reference.
172  */
173 static inline const struct cred *get_cred(const struct cred *cred)
174 {
175         return get_new_cred((struct cred *) cred);
176 }
177
178 /**
179  * put_cred - Release a reference to a set of credentials
180  * @cred: The credentials to release
181  *
182  * Release a reference to a set of credentials, deleting them when the last ref
183  * is released.
184  */
185 static inline void put_cred(const struct cred *_cred)
186 {
187         struct cred *cred = (struct cred *) _cred;
188
189         BUG_ON(atomic_read(&(cred)->usage) <= 0);
190         if (atomic_dec_and_test(&(cred)->usage))
191                 __put_cred(cred);
192 }
193
194 /**
195  * current_cred - Access the current task's credentials
196  *
197  * Access the credentials of the current task.
198  */
199 #define current_cred() \
200         (current->cred)
201
202 /**
203  * __task_cred - Access another task's credentials
204  * @task: The task to query
205  *
206  * Access the credentials of another task.  The caller must hold the
207  * RCU readlock.
208  *
209  * The caller must make sure task doesn't go away, either by holding a ref on
210  * task or by holding tasklist_lock to prevent it from being unlinked.
211  */
212 #define __task_cred(task) \
213         ((const struct cred *)(rcu_dereference((task)->cred)))
214
215 /**
216  * get_task_cred - Get another task's credentials
217  * @task: The task to query
218  *
219  * Get the credentials of a task, pinning them so that they can't go away.
220  * Accessing a task's credentials directly is not permitted.
221  *
222  * The caller must make sure task doesn't go away, either by holding a ref on
223  * task or by holding tasklist_lock to prevent it from being unlinked.
224  */
225 #define get_task_cred(task)                             \
226 ({                                                      \
227         struct cred *__cred;                            \
228         rcu_read_lock();                                \
229         __cred = (struct cred *) __task_cred((task));   \
230         get_cred(__cred);                               \
231         rcu_read_unlock();                              \
232         __cred;                                         \
233 })
234
235 /**
236  * get_current_cred - Get the current task's credentials
237  *
238  * Get the credentials of the current task, pinning them so that they can't go
239  * away.  Accessing the current task's credentials directly is not permitted.
240  */
241 #define get_current_cred()                              \
242         (get_cred(current_cred()))
243
244 /**
245  * get_current_user - Get the current task's user_struct
246  *
247  * Get the user record of the current task, pinning it so that it can't go
248  * away.
249  */
250 #define get_current_user()                              \
251 ({                                                      \
252         struct user_struct *__u;                        \
253         struct cred *__cred;                            \
254         __cred = (struct cred *) current_cred();        \
255         __u = get_uid(__cred->user);                    \
256         __u;                                            \
257 })
258
259 /**
260  * get_current_groups - Get the current task's supplementary group list
261  *
262  * Get the supplementary group list of the current task, pinning it so that it
263  * can't go away.
264  */
265 #define get_current_groups()                            \
266 ({                                                      \
267         struct group_info *__groups;                    \
268         struct cred *__cred;                            \
269         __cred = (struct cred *) current_cred();        \
270         __groups = get_group_info(__cred->group_info);  \
271         __groups;                                       \
272 })
273
274 #define task_cred_xxx(task, xxx)                        \
275 ({                                                      \
276         __typeof__(((struct cred *)NULL)->xxx) ___val;  \
277         rcu_read_lock();                                \
278         ___val = __task_cred((task))->xxx;              \
279         rcu_read_unlock();                              \
280         ___val;                                         \
281 })
282
283 #define task_uid(task)          (task_cred_xxx((task), uid))
284 #define task_euid(task)         (task_cred_xxx((task), euid))
285
286 #define current_cred_xxx(xxx)                   \
287 ({                                              \
288         current->cred->xxx;                     \
289 })
290
291 #define current_uid()           (current_cred_xxx(uid))
292 #define current_gid()           (current_cred_xxx(gid))
293 #define current_euid()          (current_cred_xxx(euid))
294 #define current_egid()          (current_cred_xxx(egid))
295 #define current_suid()          (current_cred_xxx(suid))
296 #define current_sgid()          (current_cred_xxx(sgid))
297 #define current_fsuid()         (current_cred_xxx(fsuid))
298 #define current_fsgid()         (current_cred_xxx(fsgid))
299 #define current_cap()           (current_cred_xxx(cap_effective))
300 #define current_user()          (current_cred_xxx(user))
301 #define current_security()      (current_cred_xxx(security))
302
303 #define current_uid_gid(_uid, _gid)             \
304 do {                                            \
305         const struct cred *__cred;              \
306         __cred = current_cred();                \
307         *(_uid) = __cred->uid;                  \
308         *(_gid) = __cred->gid;                  \
309 } while(0)
310
311 #define current_euid_egid(_euid, _egid)         \
312 do {                                            \
313         const struct cred *__cred;              \
314         __cred = current_cred();                \
315         *(_euid) = __cred->euid;                \
316         *(_egid) = __cred->egid;                \
317 } while(0)
318
319 #define current_fsuid_fsgid(_fsuid, _fsgid)     \
320 do {                                            \
321         const struct cred *__cred;              \
322         __cred = current_cred();                \
323         *(_fsuid) = __cred->fsuid;              \
324         *(_fsgid) = __cred->fsgid;              \
325 } while(0)
326
327 #endif /* _LINUX_CRED_H */