1 /* Credentials management - see Documentation/credentials.txt
3 * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved.
4 * Written by David Howells (dhowells@redhat.com)
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.
15 #include <linux/capability.h>
16 #include <linux/init.h>
17 #include <linux/key.h>
18 #include <asm/atomic.h>
25 * COW Supplementary groups list
27 #define NGROUPS_SMALL 32
28 #define NGROUPS_PER_BLOCK ((unsigned int)(PAGE_SIZE / sizeof(gid_t)))
34 gid_t small_block[NGROUPS_SMALL];
39 * get_group_info - Get a reference to a group info structure
40 * @group_info: The group info to reference
42 * This gets a reference to a set of supplementary groups.
44 * If the caller is accessing a task's credentials, they must hold the RCU read
47 static inline struct group_info *get_group_info(struct group_info *gi)
49 atomic_inc(&gi->usage);
54 * put_group_info - Release a reference to a group info structure
55 * @group_info: The group info to release
57 #define put_group_info(group_info) \
59 if (atomic_dec_and_test(&(group_info)->usage)) \
60 groups_free(group_info); \
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);
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])
74 extern int in_group_p(gid_t);
75 extern int in_egroup_p(gid_t);
78 * The common credentials for a thread group
79 * - shared by CLONE_THREAD
82 struct thread_group_cred {
84 pid_t tgid; /* thread group process ID */
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 */
93 * The security context of a task
95 * The parts of the context break down into two categories:
97 * (1) The objective context of a task. These parts are used when some other
98 * task is attempting to affect this one.
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.
103 * Note that some members of this structure belong to both categories - the
104 * LSM security pointer for instance.
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.
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.
117 #ifdef CONFIG_DEBUG_CREDENTIALS
118 atomic_t subscribers; /* number of processes subscribed */
121 #define CRED_MAGIC 0x43736564
122 #define CRED_MAGIC_DEAD 0x44656144
124 uid_t uid; /* real UID of the task */
125 gid_t gid; /* real GID of the task */
126 uid_t suid; /* saved UID of the task */
127 gid_t sgid; /* saved GID of the task */
128 uid_t euid; /* effective UID of the task */
129 gid_t egid; /* effective GID of the task */
130 uid_t fsuid; /* UID for VFS ops */
131 gid_t fsgid; /* GID for VFS ops */
132 unsigned securebits; /* SUID-less security management */
133 kernel_cap_t cap_inheritable; /* caps our children can inherit */
134 kernel_cap_t cap_permitted; /* caps we're permitted */
135 kernel_cap_t cap_effective; /* caps we can actually use */
136 kernel_cap_t cap_bset; /* capability bounding set */
138 unsigned char jit_keyring; /* default keyring to attach requested
140 struct key *thread_keyring; /* keyring private to this thread */
141 struct key *request_key_auth; /* assumed request_key authority */
142 struct thread_group_cred *tgcred; /* thread-group shared credentials */
144 #ifdef CONFIG_SECURITY
145 void *security; /* subjective LSM security */
147 struct user_struct *user; /* real user ID subscription */
148 struct group_info *group_info; /* supplementary groups for euid/fsgid */
149 struct rcu_head rcu; /* RCU deletion hook */
152 extern void __put_cred(struct cred *);
153 extern void exit_creds(struct task_struct *);
154 extern int copy_creds(struct task_struct *, unsigned long);
155 extern struct cred *prepare_creds(void);
156 extern struct cred *prepare_exec_creds(void);
157 extern struct cred *prepare_usermodehelper_creds(void);
158 extern int commit_creds(struct cred *);
159 extern void abort_creds(struct cred *);
160 extern const struct cred *override_creds(const struct cred *);
161 extern void revert_creds(const struct cred *);
162 extern struct cred *prepare_kernel_cred(struct task_struct *);
163 extern int change_create_files_as(struct cred *, struct inode *);
164 extern int set_security_override(struct cred *, u32);
165 extern int set_security_override_from_ctx(struct cred *, const char *);
166 extern int set_create_files_as(struct cred *, struct inode *);
167 extern void __init cred_init(void);
170 * check for validity of credentials
172 #ifdef CONFIG_DEBUG_CREDENTIALS
173 extern void __invalid_creds(const struct cred *, const char *, unsigned);
174 extern void __validate_process_creds(struct task_struct *,
175 const char *, unsigned);
177 static inline bool creds_are_invalid(const struct cred *cred)
179 if (cred->magic != CRED_MAGIC)
181 if (atomic_read(&cred->usage) < atomic_read(&cred->subscribers))
183 #ifdef CONFIG_SECURITY_SELINUX
184 if ((unsigned long) cred->security < PAGE_SIZE)
186 if ((*(u32*)cred->security & 0xffffff00) ==
187 (POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8))
193 static inline void __validate_creds(const struct cred *cred,
194 const char *file, unsigned line)
196 if (unlikely(creds_are_invalid(cred)))
197 __invalid_creds(cred, file, line);
200 #define validate_creds(cred) \
202 __validate_creds((cred), __FILE__, __LINE__); \
205 #define validate_process_creds() \
207 __validate_process_creds(current, __FILE__, __LINE__); \
210 extern void validate_creds_for_do_exit(struct task_struct *);
212 static inline void validate_creds(const struct cred *cred)
215 static inline void validate_creds_for_do_exit(struct task_struct *tsk)
218 static inline void validate_process_creds(void)
224 * get_new_cred - Get a reference on a new set of credentials
225 * @cred: The new credentials to reference
227 * Get a reference on the specified set of new credentials. The caller must
228 * release the reference.
230 static inline struct cred *get_new_cred(struct cred *cred)
232 atomic_inc(&cred->usage);
237 * get_cred - Get a reference on a set of credentials
238 * @cred: The credentials to reference
240 * Get a reference on the specified set of credentials. The caller must
241 * release the reference.
243 * This is used to deal with a committed set of credentials. Although the
244 * pointer is const, this will temporarily discard the const and increment the
245 * usage count. The purpose of this is to attempt to catch at compile time the
246 * accidental alteration of a set of credentials that should be considered
249 static inline const struct cred *get_cred(const struct cred *cred)
251 struct cred *nonconst_cred = (struct cred *) cred;
252 validate_creds(cred);
253 return get_new_cred(nonconst_cred);
257 * put_cred - Release a reference to a set of credentials
258 * @cred: The credentials to release
260 * Release a reference to a set of credentials, deleting them when the last ref
263 * This takes a const pointer to a set of credentials because the credentials
264 * on task_struct are attached by const pointers to prevent accidental
265 * alteration of otherwise immutable credential sets.
267 static inline void put_cred(const struct cred *_cred)
269 struct cred *cred = (struct cred *) _cred;
271 validate_creds(cred);
272 if (atomic_dec_and_test(&(cred)->usage))
277 * current_cred - Access the current task's subjective credentials
279 * Access the subjective credentials of the current task.
281 #define current_cred() \
285 * __task_cred - Access a task's objective credentials
286 * @task: The task to query
288 * Access the objective credentials of a task. The caller must hold the RCU
291 * The caller must make sure task doesn't go away, either by holding a ref on
292 * task or by holding tasklist_lock to prevent it from being unlinked.
294 #define __task_cred(task) \
295 ((const struct cred *)(rcu_dereference((task)->real_cred)))
298 * get_task_cred - Get another task's objective credentials
299 * @task: The task to query
301 * Get the objective credentials of a task, pinning them so that they can't go
302 * away. Accessing a task's credentials directly is not permitted.
304 * The caller must make sure task doesn't go away, either by holding a ref on
305 * task or by holding tasklist_lock to prevent it from being unlinked.
307 #define get_task_cred(task) \
309 struct cred *__cred; \
311 __cred = (struct cred *) __task_cred((task)); \
318 * get_current_cred - Get the current task's subjective credentials
320 * Get the subjective credentials of the current task, pinning them so that
321 * they can't go away. Accessing the current task's credentials directly is
324 #define get_current_cred() \
325 (get_cred(current_cred()))
328 * get_current_user - Get the current task's user_struct
330 * Get the user record of the current task, pinning it so that it can't go
333 #define get_current_user() \
335 struct user_struct *__u; \
336 struct cred *__cred; \
337 __cred = (struct cred *) current_cred(); \
338 __u = get_uid(__cred->user); \
343 * get_current_groups - Get the current task's supplementary group list
345 * Get the supplementary group list of the current task, pinning it so that it
348 #define get_current_groups() \
350 struct group_info *__groups; \
351 struct cred *__cred; \
352 __cred = (struct cred *) current_cred(); \
353 __groups = get_group_info(__cred->group_info); \
357 #define task_cred_xxx(task, xxx) \
359 __typeof__(((struct cred *)NULL)->xxx) ___val; \
361 ___val = __task_cred((task))->xxx; \
366 #define task_uid(task) (task_cred_xxx((task), uid))
367 #define task_euid(task) (task_cred_xxx((task), euid))
369 #define current_cred_xxx(xxx) \
371 current->cred->xxx; \
374 #define current_uid() (current_cred_xxx(uid))
375 #define current_gid() (current_cred_xxx(gid))
376 #define current_euid() (current_cred_xxx(euid))
377 #define current_egid() (current_cred_xxx(egid))
378 #define current_suid() (current_cred_xxx(suid))
379 #define current_sgid() (current_cred_xxx(sgid))
380 #define current_fsuid() (current_cred_xxx(fsuid))
381 #define current_fsgid() (current_cred_xxx(fsgid))
382 #define current_cap() (current_cred_xxx(cap_effective))
383 #define current_user() (current_cred_xxx(user))
384 #define current_user_ns() (current_cred_xxx(user)->user_ns)
385 #define current_security() (current_cred_xxx(security))
387 #define current_uid_gid(_uid, _gid) \
389 const struct cred *__cred; \
390 __cred = current_cred(); \
391 *(_uid) = __cred->uid; \
392 *(_gid) = __cred->gid; \
395 #define current_euid_egid(_euid, _egid) \
397 const struct cred *__cred; \
398 __cred = current_cred(); \
399 *(_euid) = __cred->euid; \
400 *(_egid) = __cred->egid; \
403 #define current_fsuid_fsgid(_fsuid, _fsgid) \
405 const struct cred *__cred; \
406 __cred = current_cred(); \
407 *(_fsuid) = __cred->fsuid; \
408 *(_fsgid) = __cred->fsgid; \
411 #endif /* _LINUX_CRED_H */