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David Howells98870ab2008-11-14 10:39:26 +11001/* Credentials management - see Documentation/credentials.txt
David Howells9e2b2dc2008-08-13 16:20:04 +01002 *
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
David Howellsb6dff3e2008-11-14 10:39:16 +110015#include <linux/capability.h>
Alexey Dobriyanb2e1fea2009-05-28 14:34:20 -070016#include <linux/init.h>
David Howellsb6dff3e2008-11-14 10:39:16 +110017#include <linux/key.h>
Eric Parised868a52009-09-12 22:54:10 -040018#include <linux/selinux.h>
David Howellsb6dff3e2008-11-14 10:39:16 +110019#include <asm/atomic.h>
David Howells9e2b2dc2008-08-13 16:20:04 +010020
David Howellsb6dff3e2008-11-14 10:39:16 +110021struct user_struct;
22struct cred;
David Howells3a3b7ce2008-11-14 10:39:28 +110023struct inode;
David Howells9e2b2dc2008-08-13 16:20:04 +010024
David Howellsb6dff3e2008-11-14 10:39:16 +110025/*
26 * COW Supplementary groups list
27 */
28#define NGROUPS_SMALL 32
29#define NGROUPS_PER_BLOCK ((unsigned int)(PAGE_SIZE / sizeof(gid_t)))
30
31struct group_info {
32 atomic_t usage;
33 int ngroups;
34 int nblocks;
35 gid_t small_block[NGROUPS_SMALL];
36 gid_t *blocks[0];
37};
38
39/**
40 * get_group_info - Get a reference to a group info structure
41 * @group_info: The group info to reference
42 *
David Howells86a264a2008-11-14 10:39:18 +110043 * This gets a reference to a set of supplementary groups.
44 *
45 * If the caller is accessing a task's credentials, they must hold the RCU read
46 * lock when reading.
David Howellsb6dff3e2008-11-14 10:39:16 +110047 */
David Howells86a264a2008-11-14 10:39:18 +110048static inline struct group_info *get_group_info(struct group_info *gi)
49{
50 atomic_inc(&gi->usage);
51 return gi;
52}
David Howellsb6dff3e2008-11-14 10:39:16 +110053
54/**
55 * put_group_info - Release a reference to a group info structure
56 * @group_info: The group info to release
57 */
58#define put_group_info(group_info) \
59do { \
60 if (atomic_dec_and_test(&(group_info)->usage)) \
61 groups_free(group_info); \
62} while (0)
63
64extern struct group_info *groups_alloc(int);
Serge Hallyn18b6e042008-10-15 16:38:45 -050065extern struct group_info init_groups;
David Howellsb6dff3e2008-11-14 10:39:16 +110066extern void groups_free(struct group_info *);
67extern int set_current_groups(struct group_info *);
68extern int set_groups(struct cred *, struct group_info *);
David Howells86a264a2008-11-14 10:39:18 +110069extern int groups_search(const struct group_info *, gid_t);
David Howellsb6dff3e2008-11-14 10:39:16 +110070
71/* access the groups "array" with this macro */
72#define GROUP_AT(gi, i) \
73 ((gi)->blocks[(i) / NGROUPS_PER_BLOCK][(i) % NGROUPS_PER_BLOCK])
74
75extern int in_group_p(gid_t);
76extern int in_egroup_p(gid_t);
77
78/*
David Howellsbb952bb2008-11-14 10:39:20 +110079 * The common credentials for a thread group
80 * - shared by CLONE_THREAD
81 */
82#ifdef CONFIG_KEYS
83struct thread_group_cred {
84 atomic_t usage;
85 pid_t tgid; /* thread group process ID */
86 spinlock_t lock;
87 struct key *session_keyring; /* keyring inherited over fork */
88 struct key *process_keyring; /* keyring private to this process */
89 struct rcu_head rcu; /* RCU deletion hook */
90};
91#endif
92
93/*
David Howellsb6dff3e2008-11-14 10:39:16 +110094 * The security context of a task
95 *
96 * The parts of the context break down into two categories:
97 *
98 * (1) The objective context of a task. These parts are used when some other
99 * task is attempting to affect this one.
100 *
101 * (2) The subjective context. These details are used when the task is acting
102 * upon another object, be that a file, a task, a key or whatever.
103 *
104 * Note that some members of this structure belong to both categories - the
105 * LSM security pointer for instance.
106 *
107 * A task has two security pointers. task->real_cred points to the objective
108 * context that defines that task's actual details. The objective part of this
109 * context is used whenever that task is acted upon.
110 *
111 * task->cred points to the subjective context that defines the details of how
112 * that task is going to act upon another object. This may be overridden
113 * temporarily to point to another security context, but normally points to the
114 * same context as task->real_cred.
115 */
116struct cred {
117 atomic_t usage;
David Howellse0e81732009-09-02 09:13:40 +0100118#ifdef CONFIG_DEBUG_CREDENTIALS
119 atomic_t subscribers; /* number of processes subscribed */
120 void *put_addr;
121 unsigned magic;
122#define CRED_MAGIC 0x43736564
123#define CRED_MAGIC_DEAD 0x44656144
124#endif
David Howellsb6dff3e2008-11-14 10:39:16 +1100125 uid_t uid; /* real UID of the task */
126 gid_t gid; /* real GID of the task */
127 uid_t suid; /* saved UID of the task */
128 gid_t sgid; /* saved GID of the task */
129 uid_t euid; /* effective UID of the task */
130 gid_t egid; /* effective GID of the task */
131 uid_t fsuid; /* UID for VFS ops */
132 gid_t fsgid; /* GID for VFS ops */
133 unsigned securebits; /* SUID-less security management */
134 kernel_cap_t cap_inheritable; /* caps our children can inherit */
135 kernel_cap_t cap_permitted; /* caps we're permitted */
136 kernel_cap_t cap_effective; /* caps we can actually use */
137 kernel_cap_t cap_bset; /* capability bounding set */
138#ifdef CONFIG_KEYS
139 unsigned char jit_keyring; /* default keyring to attach requested
140 * keys to */
141 struct key *thread_keyring; /* keyring private to this thread */
142 struct key *request_key_auth; /* assumed request_key authority */
David Howellsbb952bb2008-11-14 10:39:20 +1100143 struct thread_group_cred *tgcred; /* thread-group shared credentials */
David Howellsb6dff3e2008-11-14 10:39:16 +1100144#endif
145#ifdef CONFIG_SECURITY
146 void *security; /* subjective LSM security */
147#endif
148 struct user_struct *user; /* real user ID subscription */
149 struct group_info *group_info; /* supplementary groups for euid/fsgid */
150 struct rcu_head rcu; /* RCU deletion hook */
David Howellsb6dff3e2008-11-14 10:39:16 +1100151};
152
David Howellsf1752ee2008-11-14 10:39:17 +1100153extern void __put_cred(struct cred *);
David Howellse0e81732009-09-02 09:13:40 +0100154extern void exit_creds(struct task_struct *);
David Howellsf1752ee2008-11-14 10:39:17 +1100155extern int copy_creds(struct task_struct *, unsigned long);
David Howellsee18d642009-09-02 09:14:21 +0100156extern struct cred *cred_alloc_blank(void);
David Howellsd84f4f92008-11-14 10:39:23 +1100157extern struct cred *prepare_creds(void);
David Howellsa6f76f22008-11-14 10:39:24 +1100158extern struct cred *prepare_exec_creds(void);
David Howellsd84f4f92008-11-14 10:39:23 +1100159extern struct cred *prepare_usermodehelper_creds(void);
160extern int commit_creds(struct cred *);
161extern void abort_creds(struct cred *);
David Howells3b11a1d2008-11-14 10:39:26 +1100162extern const struct cred *override_creds(const struct cred *);
163extern void revert_creds(const struct cred *);
David Howells3a3b7ce2008-11-14 10:39:28 +1100164extern struct cred *prepare_kernel_cred(struct task_struct *);
165extern int change_create_files_as(struct cred *, struct inode *);
166extern int set_security_override(struct cred *, u32);
167extern int set_security_override_from_ctx(struct cred *, const char *);
168extern int set_create_files_as(struct cred *, struct inode *);
David Howellsd84f4f92008-11-14 10:39:23 +1100169extern void __init cred_init(void);
170
David Howellse0e81732009-09-02 09:13:40 +0100171/*
172 * check for validity of credentials
173 */
174#ifdef CONFIG_DEBUG_CREDENTIALS
175extern void __invalid_creds(const struct cred *, const char *, unsigned);
176extern void __validate_process_creds(struct task_struct *,
177 const char *, unsigned);
178
179static inline bool creds_are_invalid(const struct cred *cred)
180{
181 if (cred->magic != CRED_MAGIC)
182 return true;
183 if (atomic_read(&cred->usage) < atomic_read(&cred->subscribers))
184 return true;
185#ifdef CONFIG_SECURITY_SELINUX
Eric Parised868a52009-09-12 22:54:10 -0400186 if (selinux_is_enabled()) {
187 if ((unsigned long) cred->security < PAGE_SIZE)
188 return true;
189 if ((*(u32 *)cred->security & 0xffffff00) ==
190 (POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8))
191 return true;
192 }
David Howellse0e81732009-09-02 09:13:40 +0100193#endif
194 return false;
195}
196
197static inline void __validate_creds(const struct cred *cred,
198 const char *file, unsigned line)
199{
200 if (unlikely(creds_are_invalid(cred)))
201 __invalid_creds(cred, file, line);
202}
203
204#define validate_creds(cred) \
205do { \
206 __validate_creds((cred), __FILE__, __LINE__); \
207} while(0)
208
209#define validate_process_creds() \
210do { \
211 __validate_process_creds(current, __FILE__, __LINE__); \
212} while(0)
213
214extern void validate_creds_for_do_exit(struct task_struct *);
215#else
216static inline void validate_creds(const struct cred *cred)
217{
218}
219static inline void validate_creds_for_do_exit(struct task_struct *tsk)
220{
221}
222static inline void validate_process_creds(void)
223{
224}
225#endif
226
David Howellsd84f4f92008-11-14 10:39:23 +1100227/**
228 * get_new_cred - Get a reference on a new set of credentials
229 * @cred: The new credentials to reference
230 *
231 * Get a reference on the specified set of new credentials. The caller must
232 * release the reference.
233 */
234static inline struct cred *get_new_cred(struct cred *cred)
235{
236 atomic_inc(&cred->usage);
237 return cred;
238}
David Howellsf1752ee2008-11-14 10:39:17 +1100239
240/**
241 * get_cred - Get a reference on a set of credentials
242 * @cred: The credentials to reference
243 *
244 * Get a reference on the specified set of credentials. The caller must
245 * release the reference.
David Howells98870ab2008-11-14 10:39:26 +1100246 *
247 * This is used to deal with a committed set of credentials. Although the
248 * pointer is const, this will temporarily discard the const and increment the
249 * usage count. The purpose of this is to attempt to catch at compile time the
250 * accidental alteration of a set of credentials that should be considered
251 * immutable.
David Howellsf1752ee2008-11-14 10:39:17 +1100252 */
David Howellsd84f4f92008-11-14 10:39:23 +1100253static inline const struct cred *get_cred(const struct cred *cred)
David Howellsf1752ee2008-11-14 10:39:17 +1100254{
Paul Menage1c388ad2009-07-17 16:16:18 -0700255 struct cred *nonconst_cred = (struct cred *) cred;
David Howellse0e81732009-09-02 09:13:40 +0100256 validate_creds(cred);
Paul Menage1c388ad2009-07-17 16:16:18 -0700257 return get_new_cred(nonconst_cred);
David Howellsf1752ee2008-11-14 10:39:17 +1100258}
259
260/**
261 * put_cred - Release a reference to a set of credentials
262 * @cred: The credentials to release
263 *
264 * Release a reference to a set of credentials, deleting them when the last ref
265 * is released.
David Howells98870ab2008-11-14 10:39:26 +1100266 *
267 * This takes a const pointer to a set of credentials because the credentials
268 * on task_struct are attached by const pointers to prevent accidental
269 * alteration of otherwise immutable credential sets.
David Howellsf1752ee2008-11-14 10:39:17 +1100270 */
David Howellsc69e8d92008-11-14 10:39:19 +1100271static inline void put_cred(const struct cred *_cred)
David Howellsf1752ee2008-11-14 10:39:17 +1100272{
David Howellsc69e8d92008-11-14 10:39:19 +1100273 struct cred *cred = (struct cred *) _cred;
David Howellsd84f4f92008-11-14 10:39:23 +1100274
David Howellse0e81732009-09-02 09:13:40 +0100275 validate_creds(cred);
David Howellsf1752ee2008-11-14 10:39:17 +1100276 if (atomic_dec_and_test(&(cred)->usage))
277 __put_cred(cred);
278}
279
David Howells86a264a2008-11-14 10:39:18 +1100280/**
David Howells3b11a1d2008-11-14 10:39:26 +1100281 * current_cred - Access the current task's subjective credentials
David Howells86a264a2008-11-14 10:39:18 +1100282 *
David Howells3b11a1d2008-11-14 10:39:26 +1100283 * Access the subjective credentials of the current task.
David Howells86a264a2008-11-14 10:39:18 +1100284 */
285#define current_cred() \
286 (current->cred)
287
288/**
David Howells3b11a1d2008-11-14 10:39:26 +1100289 * __task_cred - Access a task's objective credentials
David Howells86a264a2008-11-14 10:39:18 +1100290 * @task: The task to query
291 *
David Howells3b11a1d2008-11-14 10:39:26 +1100292 * Access the objective credentials of a task. The caller must hold the RCU
293 * readlock.
David Howells86a264a2008-11-14 10:39:18 +1100294 *
295 * The caller must make sure task doesn't go away, either by holding a ref on
296 * task or by holding tasklist_lock to prevent it from being unlinked.
297 */
298#define __task_cred(task) \
David Howells3b11a1d2008-11-14 10:39:26 +1100299 ((const struct cred *)(rcu_dereference((task)->real_cred)))
David Howells86a264a2008-11-14 10:39:18 +1100300
301/**
David Howells3b11a1d2008-11-14 10:39:26 +1100302 * get_task_cred - Get another task's objective credentials
David Howells86a264a2008-11-14 10:39:18 +1100303 * @task: The task to query
304 *
David Howells3b11a1d2008-11-14 10:39:26 +1100305 * Get the objective credentials of a task, pinning them so that they can't go
306 * away. Accessing a task's credentials directly is not permitted.
David Howells86a264a2008-11-14 10:39:18 +1100307 *
308 * The caller must make sure task doesn't go away, either by holding a ref on
309 * task or by holding tasklist_lock to prevent it from being unlinked.
310 */
311#define get_task_cred(task) \
312({ \
313 struct cred *__cred; \
314 rcu_read_lock(); \
315 __cred = (struct cred *) __task_cred((task)); \
316 get_cred(__cred); \
317 rcu_read_unlock(); \
318 __cred; \
319})
320
321/**
David Howells3b11a1d2008-11-14 10:39:26 +1100322 * get_current_cred - Get the current task's subjective credentials
David Howells86a264a2008-11-14 10:39:18 +1100323 *
David Howells3b11a1d2008-11-14 10:39:26 +1100324 * Get the subjective credentials of the current task, pinning them so that
325 * they can't go away. Accessing the current task's credentials directly is
326 * not permitted.
David Howells86a264a2008-11-14 10:39:18 +1100327 */
328#define get_current_cred() \
329 (get_cred(current_cred()))
330
331/**
332 * get_current_user - Get the current task's user_struct
333 *
334 * Get the user record of the current task, pinning it so that it can't go
335 * away.
336 */
337#define get_current_user() \
338({ \
339 struct user_struct *__u; \
340 struct cred *__cred; \
341 __cred = (struct cred *) current_cred(); \
342 __u = get_uid(__cred->user); \
343 __u; \
344})
345
346/**
347 * get_current_groups - Get the current task's supplementary group list
348 *
349 * Get the supplementary group list of the current task, pinning it so that it
350 * can't go away.
351 */
352#define get_current_groups() \
353({ \
354 struct group_info *__groups; \
355 struct cred *__cred; \
356 __cred = (struct cred *) current_cred(); \
357 __groups = get_group_info(__cred->group_info); \
358 __groups; \
359})
360
David Howellsd84f4f92008-11-14 10:39:23 +1100361#define task_cred_xxx(task, xxx) \
362({ \
363 __typeof__(((struct cred *)NULL)->xxx) ___val; \
364 rcu_read_lock(); \
365 ___val = __task_cred((task))->xxx; \
366 rcu_read_unlock(); \
367 ___val; \
David Howells86a264a2008-11-14 10:39:18 +1100368})
369
370#define task_uid(task) (task_cred_xxx((task), uid))
371#define task_euid(task) (task_cred_xxx((task), euid))
372
373#define current_cred_xxx(xxx) \
374({ \
375 current->cred->xxx; \
376})
377
378#define current_uid() (current_cred_xxx(uid))
379#define current_gid() (current_cred_xxx(gid))
380#define current_euid() (current_cred_xxx(euid))
381#define current_egid() (current_cred_xxx(egid))
382#define current_suid() (current_cred_xxx(suid))
383#define current_sgid() (current_cred_xxx(sgid))
384#define current_fsuid() (current_cred_xxx(fsuid))
385#define current_fsgid() (current_cred_xxx(fsgid))
386#define current_cap() (current_cred_xxx(cap_effective))
387#define current_user() (current_cred_xxx(user))
Serge Hallyn18b6e042008-10-15 16:38:45 -0500388#define current_user_ns() (current_cred_xxx(user)->user_ns)
David Howells86a264a2008-11-14 10:39:18 +1100389#define current_security() (current_cred_xxx(security))
390
391#define current_uid_gid(_uid, _gid) \
392do { \
393 const struct cred *__cred; \
394 __cred = current_cred(); \
395 *(_uid) = __cred->uid; \
396 *(_gid) = __cred->gid; \
397} while(0)
398
399#define current_euid_egid(_euid, _egid) \
400do { \
401 const struct cred *__cred; \
402 __cred = current_cred(); \
403 *(_euid) = __cred->euid; \
404 *(_egid) = __cred->egid; \
405} while(0)
406
407#define current_fsuid_fsgid(_fsuid, _fsgid) \
408do { \
409 const struct cred *__cred; \
410 __cred = current_cred(); \
411 *(_fsuid) = __cred->fsuid; \
412 *(_fsgid) = __cred->fsgid; \
413} while(0)
414
David Howells9e2b2dc2008-08-13 16:20:04 +0100415#endif /* _LINUX_CRED_H */