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98870ab0 1/* Credentials management - see Documentation/credentials.txt
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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
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15#include <linux/capability.h>
16#include <linux/key.h>
17#include <asm/atomic.h>
18
19struct user_struct;
20struct cred;
3a3b7ce9 21struct inode;
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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
29struct 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 *
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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.
b6dff3ec 45 */
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46static inline struct group_info *get_group_info(struct group_info *gi)
47{
48 atomic_inc(&gi->usage);
49 return gi;
50}
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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) \
57do { \
58 if (atomic_dec_and_test(&(group_info)->usage)) \
59 groups_free(group_info); \
60} while (0)
61
62extern struct group_info *groups_alloc(int);
63extern void groups_free(struct group_info *);
64extern int set_current_groups(struct group_info *);
65extern int set_groups(struct cred *, struct group_info *);
86a264ab 66extern int groups_search(const struct group_info *, gid_t);
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67
68/* access the groups "array" with this macro */
69#define GROUP_AT(gi, i) \
70 ((gi)->blocks[(i) / NGROUPS_PER_BLOCK][(i) % NGROUPS_PER_BLOCK])
71
72extern int in_group_p(gid_t);
73extern int in_egroup_p(gid_t);
74
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75/*
76 * The common credentials for a thread group
77 * - shared by CLONE_THREAD
78 */
79#ifdef CONFIG_KEYS
80struct thread_group_cred {
81 atomic_t usage;
82 pid_t tgid; /* thread group process ID */
83 spinlock_t lock;
84 struct key *session_keyring; /* keyring inherited over fork */
85 struct key *process_keyring; /* keyring private to this process */
86 struct rcu_head rcu; /* RCU deletion hook */
87};
88#endif
89
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90/*
91 * The security context of a task
92 *
93 * The parts of the context break down into two categories:
94 *
95 * (1) The objective context of a task. These parts are used when some other
96 * task is attempting to affect this one.
97 *
98 * (2) The subjective context. These details are used when the task is acting
99 * upon another object, be that a file, a task, a key or whatever.
100 *
101 * Note that some members of this structure belong to both categories - the
102 * LSM security pointer for instance.
103 *
104 * A task has two security pointers. task->real_cred points to the objective
105 * context that defines that task's actual details. The objective part of this
106 * context is used whenever that task is acted upon.
107 *
108 * task->cred points to the subjective context that defines the details of how
109 * that task is going to act upon another object. This may be overridden
110 * temporarily to point to another security context, but normally points to the
111 * same context as task->real_cred.
112 */
113struct cred {
114 atomic_t usage;
115 uid_t uid; /* real UID of the task */
116 gid_t gid; /* real GID of the task */
117 uid_t suid; /* saved UID of the task */
118 gid_t sgid; /* saved GID of the task */
119 uid_t euid; /* effective UID of the task */
120 gid_t egid; /* effective GID of the task */
121 uid_t fsuid; /* UID for VFS ops */
122 gid_t fsgid; /* GID for VFS ops */
123 unsigned securebits; /* SUID-less security management */
124 kernel_cap_t cap_inheritable; /* caps our children can inherit */
125 kernel_cap_t cap_permitted; /* caps we're permitted */
126 kernel_cap_t cap_effective; /* caps we can actually use */
127 kernel_cap_t cap_bset; /* capability bounding set */
128#ifdef CONFIG_KEYS
129 unsigned char jit_keyring; /* default keyring to attach requested
130 * keys to */
131 struct key *thread_keyring; /* keyring private to this thread */
132 struct key *request_key_auth; /* assumed request_key authority */
bb952bb9 133 struct thread_group_cred *tgcred; /* thread-group shared credentials */
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134#endif
135#ifdef CONFIG_SECURITY
136 void *security; /* subjective LSM security */
137#endif
138 struct user_struct *user; /* real user ID subscription */
139 struct group_info *group_info; /* supplementary groups for euid/fsgid */
140 struct rcu_head rcu; /* RCU deletion hook */
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141};
142
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143extern void __put_cred(struct cred *);
144extern int copy_creds(struct task_struct *, unsigned long);
d84f4f99 145extern struct cred *prepare_creds(void);
a6f76f23 146extern struct cred *prepare_exec_creds(void);
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147extern struct cred *prepare_usermodehelper_creds(void);
148extern int commit_creds(struct cred *);
149extern void abort_creds(struct cred *);
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150extern const struct cred *override_creds(const struct cred *);
151extern void revert_creds(const struct cred *);
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152extern struct cred *prepare_kernel_cred(struct task_struct *);
153extern int change_create_files_as(struct cred *, struct inode *);
154extern int set_security_override(struct cred *, u32);
155extern int set_security_override_from_ctx(struct cred *, const char *);
156extern int set_create_files_as(struct cred *, struct inode *);
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157extern void __init cred_init(void);
158
159/**
160 * get_new_cred - Get a reference on a new set of credentials
161 * @cred: The new credentials to reference
162 *
163 * Get a reference on the specified set of new credentials. The caller must
164 * release the reference.
165 */
166static inline struct cred *get_new_cred(struct cred *cred)
167{
168 atomic_inc(&cred->usage);
169 return cred;
170}
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171
172/**
173 * get_cred - Get a reference on a set of credentials
174 * @cred: The credentials to reference
175 *
176 * Get a reference on the specified set of credentials. The caller must
177 * release the reference.
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178 *
179 * This is used to deal with a committed set of credentials. Although the
180 * pointer is const, this will temporarily discard the const and increment the
181 * usage count. The purpose of this is to attempt to catch at compile time the
182 * accidental alteration of a set of credentials that should be considered
183 * immutable.
f1752eec 184 */
d84f4f99 185static inline const struct cred *get_cred(const struct cred *cred)
f1752eec 186{
d84f4f99 187 return get_new_cred((struct cred *) cred);
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188}
189
190/**
191 * put_cred - Release a reference to a set of credentials
192 * @cred: The credentials to release
193 *
194 * Release a reference to a set of credentials, deleting them when the last ref
195 * is released.
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196 *
197 * This takes a const pointer to a set of credentials because the credentials
198 * on task_struct are attached by const pointers to prevent accidental
199 * alteration of otherwise immutable credential sets.
f1752eec 200 */
c69e8d9c 201static inline void put_cred(const struct cred *_cred)
f1752eec 202{
c69e8d9c 203 struct cred *cred = (struct cred *) _cred;
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204
205 BUG_ON(atomic_read(&(cred)->usage) <= 0);
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206 if (atomic_dec_and_test(&(cred)->usage))
207 __put_cred(cred);
208}
209
86a264ab 210/**
3b11a1de 211 * current_cred - Access the current task's subjective credentials
86a264ab 212 *
3b11a1de 213 * Access the subjective credentials of the current task.
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214 */
215#define current_cred() \
216 (current->cred)
217
218/**
3b11a1de 219 * __task_cred - Access a task's objective credentials
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220 * @task: The task to query
221 *
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222 * Access the objective credentials of a task. The caller must hold the RCU
223 * readlock.
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224 *
225 * The caller must make sure task doesn't go away, either by holding a ref on
226 * task or by holding tasklist_lock to prevent it from being unlinked.
227 */
228#define __task_cred(task) \
3b11a1de 229 ((const struct cred *)(rcu_dereference((task)->real_cred)))
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230
231/**
3b11a1de 232 * get_task_cred - Get another task's objective credentials
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233 * @task: The task to query
234 *
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235 * Get the objective credentials of a task, pinning them so that they can't go
236 * away. Accessing a task's credentials directly is not permitted.
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237 *
238 * The caller must make sure task doesn't go away, either by holding a ref on
239 * task or by holding tasklist_lock to prevent it from being unlinked.
240 */
241#define get_task_cred(task) \
242({ \
243 struct cred *__cred; \
244 rcu_read_lock(); \
245 __cred = (struct cred *) __task_cred((task)); \
246 get_cred(__cred); \
247 rcu_read_unlock(); \
248 __cred; \
249})
250
251/**
3b11a1de 252 * get_current_cred - Get the current task's subjective credentials
86a264ab 253 *
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254 * Get the subjective credentials of the current task, pinning them so that
255 * they can't go away. Accessing the current task's credentials directly is
256 * not permitted.
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257 */
258#define get_current_cred() \
259 (get_cred(current_cred()))
260
261/**
262 * get_current_user - Get the current task's user_struct
263 *
264 * Get the user record of the current task, pinning it so that it can't go
265 * away.
266 */
267#define get_current_user() \
268({ \
269 struct user_struct *__u; \
270 struct cred *__cred; \
271 __cred = (struct cred *) current_cred(); \
272 __u = get_uid(__cred->user); \
273 __u; \
274})
275
276/**
277 * get_current_groups - Get the current task's supplementary group list
278 *
279 * Get the supplementary group list of the current task, pinning it so that it
280 * can't go away.
281 */
282#define get_current_groups() \
283({ \
284 struct group_info *__groups; \
285 struct cred *__cred; \
286 __cred = (struct cred *) current_cred(); \
287 __groups = get_group_info(__cred->group_info); \
288 __groups; \
289})
290
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291#define task_cred_xxx(task, xxx) \
292({ \
293 __typeof__(((struct cred *)NULL)->xxx) ___val; \
294 rcu_read_lock(); \
295 ___val = __task_cred((task))->xxx; \
296 rcu_read_unlock(); \
297 ___val; \
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298})
299
300#define task_uid(task) (task_cred_xxx((task), uid))
301#define task_euid(task) (task_cred_xxx((task), euid))
302
303#define current_cred_xxx(xxx) \
304({ \
305 current->cred->xxx; \
306})
307
308#define current_uid() (current_cred_xxx(uid))
309#define current_gid() (current_cred_xxx(gid))
310#define current_euid() (current_cred_xxx(euid))
311#define current_egid() (current_cred_xxx(egid))
312#define current_suid() (current_cred_xxx(suid))
313#define current_sgid() (current_cred_xxx(sgid))
314#define current_fsuid() (current_cred_xxx(fsuid))
315#define current_fsgid() (current_cred_xxx(fsgid))
316#define current_cap() (current_cred_xxx(cap_effective))
317#define current_user() (current_cred_xxx(user))
318#define current_security() (current_cred_xxx(security))
319
320#define current_uid_gid(_uid, _gid) \
321do { \
322 const struct cred *__cred; \
323 __cred = current_cred(); \
324 *(_uid) = __cred->uid; \
325 *(_gid) = __cred->gid; \
326} while(0)
327
328#define current_euid_egid(_euid, _egid) \
329do { \
330 const struct cred *__cred; \
331 __cred = current_cred(); \
332 *(_euid) = __cred->euid; \
333 *(_egid) = __cred->egid; \
334} while(0)
335
336#define current_fsuid_fsgid(_fsuid, _fsgid) \
337do { \
338 const struct cred *__cred; \
339 __cred = current_cred(); \
340 *(_fsuid) = __cred->fsuid; \
341 *(_fsgid) = __cred->fsgid; \
342} while(0)
343
9e2b2dc4 344#endif /* _LINUX_CRED_H */