include/linux/cred.h

   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  */
  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 void groups_free(struct group_info *);
  64 extern int set_current_groups(struct group_info *);
  65 extern int set_groups(struct cred *, struct group_info *);
  66 extern int groups_search(const struct group_info *, gid_t);
  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
  72 extern int in_group_p(gid_t);
  73 extern int in_egroup_p(gid_t);
  74
  75 /*
  76  * The common credentials for a thread group
  77  * - shared by CLONE_THREAD
  78  */
  79 #ifdef CONFIG_KEYS
  80 struct 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
  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  */
 113 struct 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 */
 133         struct thread_group_cred *tgcred; /* thread-group shared credentials */
 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 */
 141 };
 142
 143 extern void __put_cred(struct cred *);
 144 extern int copy_creds(struct task_struct *, unsigned long);
 145 extern struct cred *prepare_creds(void);
 146 extern struct cred *prepare_exec_creds(void);
 147 extern struct cred *prepare_usermodehelper_creds(void);
 148 extern int commit_creds(struct cred *);
 149 extern void abort_creds(struct cred *);
 150 extern const struct cred *override_creds(const struct cred *);
 151 extern void revert_creds(const struct cred *);
 152 extern struct cred *prepare_kernel_cred(struct task_struct *);
 153 extern int change_create_files_as(struct cred *, struct inode *);
 154 extern int set_security_override(struct cred *, u32);
 155 extern int set_security_override_from_ctx(struct cred *, const char *);
 156 extern int set_create_files_as(struct cred *, struct inode *);
 157 extern 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  */
 166 static inline struct cred *get_new_cred(struct cred *cred)
 167 {
 168         atomic_inc(&cred->usage);
 169         return cred;
 170 }
 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.
 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.
 184  */
 185 static inline const struct cred *get_cred(const struct cred *cred)
 186 {
 187         return get_new_cred((struct cred *) cred);
 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.
 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.
 200  */
 201 static inline void put_cred(const struct cred *_cred)
 202 {
 203         struct cred *cred = (struct cred *) _cred;
 204
 205         BUG_ON(atomic_read(&(cred)->usage) <= 0);
 206         if (atomic_dec_and_test(&(cred)->usage))
 207                 __put_cred(cred);
 208 }
 209
 210 /**
 211  * current_cred - Access the current task's subjective credentials
 212  *
 213  * Access the subjective credentials of the current task.
 214  */
 215 #define current_cred() \
 216         (current->cred)
 217
 218 /**
 219  * __task_cred - Access a task's objective credentials
 220  * @task: The task to query
 221  *
 222  * Access the objective credentials of a task.  The caller must hold the RCU
 223  * readlock.
 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) \
 229         ((const struct cred *)(rcu_dereference((task)->real_cred)))
 230
 231 /**
 232  * get_task_cred - Get another task's objective credentials
 233  * @task: The task to query
 234  *
 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.
 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 /**
 252  * get_current_cred - Get the current task's subjective credentials
 253  *
 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.
 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
 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;                                         \
 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)             \
 321 do {                                            \
 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)         \
 329 do {                                            \
 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)     \
 337 do {                                            \
 338         const struct cred *__cred;              \
 339         __cred = current_cred();                \
 340         *(_fsuid) = __cred->fsuid;              \
 341         *(_fsgid) = __cred->fsgid;              \
 342 } while(0)
 343
 344 #endif /* _LINUX_CRED_H */