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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  */
get_group_info(struct group_info * gi)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  */
get_new_cred(struct cred * cred)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  */
get_cred(const struct cred * cred)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  */
put_cred(const struct cred * _cred)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 */
347