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Linux/include/linux/cred.h

  1 /* Credentials management - see Documentation/security/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/init.h>
 17 #include <linux/key.h>
 18 #include <linux/selinux.h>
 19 #include <linux/atomic.h>
 20 #include <linux/uidgid.h>
 21 
 22 struct user_struct;
 23 struct cred;
 24 struct inode;
 25 
 26 /*
 27  * COW Supplementary groups list
 28  */
 29 #define NGROUPS_SMALL           32
 30 #define NGROUPS_PER_BLOCK       ((unsigned int)(PAGE_SIZE / sizeof(kgid_t)))
 31 
 32 struct group_info {
 33         atomic_t        usage;
 34         int             ngroups;
 35         int             nblocks;
 36         kgid_t          small_block[NGROUPS_SMALL];
 37         kgid_t          *blocks[0];
 38 };
 39 
 40 /**
 41  * get_group_info - Get a reference to a group info structure
 42  * @group_info: The group info to reference
 43  *
 44  * This gets a reference to a set of supplementary groups.
 45  *
 46  * If the caller is accessing a task's credentials, they must hold the RCU read
 47  * lock when reading.
 48  */
 49 static inline struct group_info *get_group_info(struct group_info *gi)
 50 {
 51         atomic_inc(&gi->usage);
 52         return gi;
 53 }
 54 
 55 /**
 56  * put_group_info - Release a reference to a group info structure
 57  * @group_info: The group info to release
 58  */
 59 #define put_group_info(group_info)                      \
 60 do {                                                    \
 61         if (atomic_dec_and_test(&(group_info)->usage))  \
 62                 groups_free(group_info);                \
 63 } while (0)
 64 
 65 extern struct group_info init_groups;
 66 #ifdef CONFIG_MULTIUSER
 67 extern struct group_info *groups_alloc(int);
 68 extern void groups_free(struct group_info *);
 69 
 70 extern int in_group_p(kgid_t);
 71 extern int in_egroup_p(kgid_t);
 72 #else
 73 static inline void groups_free(struct group_info *group_info)
 74 {
 75 }
 76 
 77 static inline int in_group_p(kgid_t grp)
 78 {
 79         return 1;
 80 }
 81 static inline int in_egroup_p(kgid_t grp)
 82 {
 83         return 1;
 84 }
 85 #endif
 86 extern int set_current_groups(struct group_info *);
 87 extern void set_groups(struct cred *, struct group_info *);
 88 extern int groups_search(const struct group_info *, kgid_t);
 89 extern bool may_setgroups(void);
 90 
 91 /* access the groups "array" with this macro */
 92 #define GROUP_AT(gi, i) \
 93         ((gi)->blocks[(i) / NGROUPS_PER_BLOCK][(i) % NGROUPS_PER_BLOCK])
 94 
 95 /*
 96  * The security context of a task
 97  *
 98  * The parts of the context break down into two categories:
 99  *
100  *  (1) The objective context of a task.  These parts are used when some other
101  *      task is attempting to affect this one.
102  *
103  *  (2) The subjective context.  These details are used when the task is acting
104  *      upon another object, be that a file, a task, a key or whatever.
105  *
106  * Note that some members of this structure belong to both categories - the
107  * LSM security pointer for instance.
108  *
109  * A task has two security pointers.  task->real_cred points to the objective
110  * context that defines that task's actual details.  The objective part of this
111  * context is used whenever that task is acted upon.
112  *
113  * task->cred points to the subjective context that defines the details of how
114  * that task is going to act upon another object.  This may be overridden
115  * temporarily to point to another security context, but normally points to the
116  * same context as task->real_cred.
117  */
118 struct cred {
119         atomic_t        usage;
120 #ifdef CONFIG_DEBUG_CREDENTIALS
121         atomic_t        subscribers;    /* number of processes subscribed */
122         void            *put_addr;
123         unsigned        magic;
124 #define CRED_MAGIC      0x43736564
125 #define CRED_MAGIC_DEAD 0x44656144
126 #endif
127         kuid_t          uid;            /* real UID of the task */
128         kgid_t          gid;            /* real GID of the task */
129         kuid_t          suid;           /* saved UID of the task */
130         kgid_t          sgid;           /* saved GID of the task */
131         kuid_t          euid;           /* effective UID of the task */
132         kgid_t          egid;           /* effective GID of the task */
133         kuid_t          fsuid;          /* UID for VFS ops */
134         kgid_t          fsgid;          /* GID for VFS ops */
135         unsigned        securebits;     /* SUID-less security management */
136         kernel_cap_t    cap_inheritable; /* caps our children can inherit */
137         kernel_cap_t    cap_permitted;  /* caps we're permitted */
138         kernel_cap_t    cap_effective;  /* caps we can actually use */
139         kernel_cap_t    cap_bset;       /* capability bounding set */
140         kernel_cap_t    cap_ambient;    /* Ambient capability set */
141 #ifdef CONFIG_KEYS
142         unsigned char   jit_keyring;    /* default keyring to attach requested
143                                          * keys to */
144         struct key __rcu *session_keyring; /* keyring inherited over fork */
145         struct key      *process_keyring; /* keyring private to this process */
146         struct key      *thread_keyring; /* keyring private to this thread */
147         struct key      *request_key_auth; /* assumed request_key authority */
148 #endif
149 #ifdef CONFIG_SECURITY
150         void            *security;      /* subjective LSM security */
151 #endif
152         struct user_struct *user;       /* real user ID subscription */
153         struct user_namespace *user_ns; /* user_ns the caps and keyrings are relative to. */
154         struct group_info *group_info;  /* supplementary groups for euid/fsgid */
155         struct rcu_head rcu;            /* RCU deletion hook */
156 };
157 
158 extern void __put_cred(struct cred *);
159 extern void exit_creds(struct task_struct *);
160 extern int copy_creds(struct task_struct *, unsigned long);
161 extern const struct cred *get_task_cred(struct task_struct *);
162 extern struct cred *cred_alloc_blank(void);
163 extern struct cred *prepare_creds(void);
164 extern struct cred *prepare_exec_creds(void);
165 extern int commit_creds(struct cred *);
166 extern void abort_creds(struct cred *);
167 extern const struct cred *override_creds(const struct cred *);
168 extern void revert_creds(const struct cred *);
169 extern struct cred *prepare_kernel_cred(struct task_struct *);
170 extern int change_create_files_as(struct cred *, struct inode *);
171 extern int set_security_override(struct cred *, u32);
172 extern int set_security_override_from_ctx(struct cred *, const char *);
173 extern int set_create_files_as(struct cred *, struct inode *);
174 extern void __init cred_init(void);
175 
176 /*
177  * check for validity of credentials
178  */
179 #ifdef CONFIG_DEBUG_CREDENTIALS
180 extern void __invalid_creds(const struct cred *, const char *, unsigned);
181 extern void __validate_process_creds(struct task_struct *,
182                                      const char *, unsigned);
183 
184 extern bool creds_are_invalid(const struct cred *cred);
185 
186 static inline void __validate_creds(const struct cred *cred,
187                                     const char *file, unsigned line)
188 {
189         if (unlikely(creds_are_invalid(cred)))
190                 __invalid_creds(cred, file, line);
191 }
192 
193 #define validate_creds(cred)                            \
194 do {                                                    \
195         __validate_creds((cred), __FILE__, __LINE__);   \
196 } while(0)
197 
198 #define validate_process_creds()                                \
199 do {                                                            \
200         __validate_process_creds(current, __FILE__, __LINE__);  \
201 } while(0)
202 
203 extern void validate_creds_for_do_exit(struct task_struct *);
204 #else
205 static inline void validate_creds(const struct cred *cred)
206 {
207 }
208 static inline void validate_creds_for_do_exit(struct task_struct *tsk)
209 {
210 }
211 static inline void validate_process_creds(void)
212 {
213 }
214 #endif
215 
216 static inline bool cap_ambient_invariant_ok(const struct cred *cred)
217 {
218         return cap_issubset(cred->cap_ambient,
219                             cap_intersect(cred->cap_permitted,
220                                           cred->cap_inheritable));
221 }
222 
223 /**
224  * get_new_cred - Get a reference on a new set of credentials
225  * @cred: The new credentials to reference
226  *
227  * Get a reference on the specified set of new credentials.  The caller must
228  * release the reference.
229  */
230 static inline struct cred *get_new_cred(struct cred *cred)
231 {
232         atomic_inc(&cred->usage);
233         return cred;
234 }
235 
236 /**
237  * get_cred - Get a reference on a set of credentials
238  * @cred: The credentials to reference
239  *
240  * Get a reference on the specified set of credentials.  The caller must
241  * release the reference.
242  *
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
247  * immutable.
248  */
249 static inline const struct cred *get_cred(const struct cred *cred)
250 {
251         struct cred *nonconst_cred = (struct cred *) cred;
252         validate_creds(cred);
253         return get_new_cred(nonconst_cred);
254 }
255 
256 /**
257  * put_cred - Release a reference to a set of credentials
258  * @cred: The credentials to release
259  *
260  * Release a reference to a set of credentials, deleting them when the last ref
261  * is released.
262  *
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.
266  */
267 static inline void put_cred(const struct cred *_cred)
268 {
269         struct cred *cred = (struct cred *) _cred;
270 
271         validate_creds(cred);
272         if (atomic_dec_and_test(&(cred)->usage))
273                 __put_cred(cred);
274 }
275 
276 /**
277  * current_cred - Access the current task's subjective credentials
278  *
279  * Access the subjective credentials of the current task.  RCU-safe,
280  * since nobody else can modify it.
281  */
282 #define current_cred() \
283         rcu_dereference_protected(current->cred, 1)
284 
285 /**
286  * current_real_cred - Access the current task's objective credentials
287  *
288  * Access the objective credentials of the current task.  RCU-safe,
289  * since nobody else can modify it.
290  */
291 #define current_real_cred() \
292         rcu_dereference_protected(current->real_cred, 1)
293 
294 /**
295  * __task_cred - Access a task's objective credentials
296  * @task: The task to query
297  *
298  * Access the objective credentials of a task.  The caller must hold the RCU
299  * readlock.
300  *
301  * The result of this function should not be passed directly to get_cred();
302  * rather get_task_cred() should be used instead.
303  */
304 #define __task_cred(task)       \
305         rcu_dereference((task)->real_cred)
306 
307 /**
308  * get_current_cred - Get the current task's subjective credentials
309  *
310  * Get the subjective credentials of the current task, pinning them so that
311  * they can't go away.  Accessing the current task's credentials directly is
312  * not permitted.
313  */
314 #define get_current_cred()                              \
315         (get_cred(current_cred()))
316 
317 /**
318  * get_current_user - Get the current task's user_struct
319  *
320  * Get the user record of the current task, pinning it so that it can't go
321  * away.
322  */
323 #define get_current_user()                              \
324 ({                                                      \
325         struct user_struct *__u;                        \
326         const struct cred *__cred;                      \
327         __cred = current_cred();                        \
328         __u = get_uid(__cred->user);                    \
329         __u;                                            \
330 })
331 
332 /**
333  * get_current_groups - Get the current task's supplementary group list
334  *
335  * Get the supplementary group list of the current task, pinning it so that it
336  * can't go away.
337  */
338 #define get_current_groups()                            \
339 ({                                                      \
340         struct group_info *__groups;                    \
341         const struct cred *__cred;                      \
342         __cred = current_cred();                        \
343         __groups = get_group_info(__cred->group_info);  \
344         __groups;                                       \
345 })
346 
347 #define task_cred_xxx(task, xxx)                        \
348 ({                                                      \
349         __typeof__(((struct cred *)NULL)->xxx) ___val;  \
350         rcu_read_lock();                                \
351         ___val = __task_cred((task))->xxx;              \
352         rcu_read_unlock();                              \
353         ___val;                                         \
354 })
355 
356 #define task_uid(task)          (task_cred_xxx((task), uid))
357 #define task_euid(task)         (task_cred_xxx((task), euid))
358 
359 #define current_cred_xxx(xxx)                   \
360 ({                                              \
361         current_cred()->xxx;                    \
362 })
363 
364 #define current_uid()           (current_cred_xxx(uid))
365 #define current_gid()           (current_cred_xxx(gid))
366 #define current_euid()          (current_cred_xxx(euid))
367 #define current_egid()          (current_cred_xxx(egid))
368 #define current_suid()          (current_cred_xxx(suid))
369 #define current_sgid()          (current_cred_xxx(sgid))
370 #define current_fsuid()         (current_cred_xxx(fsuid))
371 #define current_fsgid()         (current_cred_xxx(fsgid))
372 #define current_cap()           (current_cred_xxx(cap_effective))
373 #define current_user()          (current_cred_xxx(user))
374 #define current_security()      (current_cred_xxx(security))
375 
376 extern struct user_namespace init_user_ns;
377 #ifdef CONFIG_USER_NS
378 #define current_user_ns()       (current_cred_xxx(user_ns))
379 #else
380 static inline struct user_namespace *current_user_ns(void)
381 {
382         return &init_user_ns;
383 }
384 #endif
385 
386 
387 #define current_uid_gid(_uid, _gid)             \
388 do {                                            \
389         const struct cred *__cred;              \
390         __cred = current_cred();                \
391         *(_uid) = __cred->uid;                  \
392         *(_gid) = __cred->gid;                  \
393 } while(0)
394 
395 #define current_euid_egid(_euid, _egid)         \
396 do {                                            \
397         const struct cred *__cred;              \
398         __cred = current_cred();                \
399         *(_euid) = __cred->euid;                \
400         *(_egid) = __cred->egid;                \
401 } while(0)
402 
403 #define current_fsuid_fsgid(_fsuid, _fsgid)     \
404 do {                                            \
405         const struct cred *__cred;              \
406         __cred = current_cred();                \
407         *(_fsuid) = __cred->fsuid;              \
408         *(_fsgid) = __cred->fsgid;              \
409 } while(0)
410 
411 #endif /* _LINUX_CRED_H */
412 

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