include/linux/cred.h

   1 /* Credentials management
   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
  22 /*
  23  * COW Supplementary groups list
  24  */
  25 #define NGROUPS_SMALL           32
  26 #define NGROUPS_PER_BLOCK       ((unsigned int)(PAGE_SIZE / sizeof(gid_t)))
  27
  28 struct group_info {
  29         atomic_t        usage;
  30         int             ngroups;
  31         int             nblocks;
  32         gid_t           small_block[NGROUPS_SMALL];
  33         gid_t           *blocks[0];
  34 };
  35
  36 /**
  37  * get_group_info - Get a reference to a group info structure
  38  * @group_info: The group info to reference
  39  *
  40  * This gets a reference to a set of supplementary groups.
  41  *
  42  * If the caller is accessing a task's credentials, they must hold the RCU read
  43  * lock when reading.
  44  */
  45 static inline struct group_info *get_group_info(struct group_info *gi)
  46 {
  47         atomic_inc(&gi->usage);
  48         return gi;
  49 }
  50
  51 /**
  52  * put_group_info - Release a reference to a group info structure
  53  * @group_info: The group info to release
  54  */
  55 #define put_group_info(group_info)                      \
  56 do {                                                    \
  57         if (atomic_dec_and_test(&(group_info)->usage))  \
  58                 groups_free(group_info);                \
  59 } while (0)
  60
  61 extern struct group_info *groups_alloc(int);
  62 extern void groups_free(struct group_info *);
  63 extern int set_current_groups(struct group_info *);
  64 extern int set_groups(struct cred *, struct group_info *);
  65 extern int groups_search(const struct group_info *, gid_t);
  66
  67 /* access the groups "array" with this macro */
  68 #define GROUP_AT(gi, i) \
  69         ((gi)->blocks[(i) / NGROUPS_PER_BLOCK][(i) % NGROUPS_PER_BLOCK])
  70
  71 extern int in_group_p(gid_t);
  72 extern int in_egroup_p(gid_t);
  73
  74 /*
  75  * The security context of a task
  76  *
  77  * The parts of the context break down into two categories:
  78  *
  79  *  (1) The objective context of a task.  These parts are used when some other
  80  *      task is attempting to affect this one.
  81  *
  82  *  (2) The subjective context.  These details are used when the task is acting
  83  *      upon another object, be that a file, a task, a key or whatever.
  84  *
  85  * Note that some members of this structure belong to both categories - the
  86  * LSM security pointer for instance.
  87  *
  88  * A task has two security pointers.  task->real_cred points to the objective
  89  * context that defines that task's actual details.  The objective part of this
  90  * context is used whenever that task is acted upon.
  91  *
  92  * task->cred points to the subjective context that defines the details of how
  93  * that task is going to act upon another object.  This may be overridden
  94  * temporarily to point to another security context, but normally points to the
  95  * same context as task->real_cred.
  96  */
  97 struct cred {
  98         atomic_t        usage;
  99         uid_t           uid;            /* real UID of the task */
 100         gid_t           gid;            /* real GID of the task */
 101         uid_t           suid;           /* saved UID of the task */
 102         gid_t           sgid;           /* saved GID of the task */
 103         uid_t           euid;           /* effective UID of the task */
 104         gid_t           egid;           /* effective GID of the task */
 105         uid_t           fsuid;          /* UID for VFS ops */
 106         gid_t           fsgid;          /* GID for VFS ops */
 107         unsigned        securebits;     /* SUID-less security management */
 108         kernel_cap_t    cap_inheritable; /* caps our children can inherit */
 109         kernel_cap_t    cap_permitted;  /* caps we're permitted */
 110         kernel_cap_t    cap_effective;  /* caps we can actually use */
 111         kernel_cap_t    cap_bset;       /* capability bounding set */
 112 #ifdef CONFIG_KEYS
 113         unsigned char   jit_keyring;    /* default keyring to attach requested
 114                                          * keys to */
 115         struct key      *thread_keyring; /* keyring private to this thread */
 116         struct key      *request_key_auth; /* assumed request_key authority */
 117 #endif
 118 #ifdef CONFIG_SECURITY
 119         void            *security;      /* subjective LSM security */
 120 #endif
 121         struct user_struct *user;       /* real user ID subscription */
 122         struct group_info *group_info;  /* supplementary groups for euid/fsgid */
 123         struct rcu_head rcu;            /* RCU deletion hook */
 124         spinlock_t      lock;           /* lock for pointer changes */
 125 };
 126
 127 extern void __put_cred(struct cred *);
 128 extern int copy_creds(struct task_struct *, unsigned long);
 129
 130 /**
 131  * get_cred - Get a reference on a set of credentials
 132  * @cred: The credentials to reference
 133  *
 134  * Get a reference on the specified set of credentials.  The caller must
 135  * release the reference.
 136  */
 137 static inline struct cred *get_cred(struct cred *cred)
 138 {
 139         atomic_inc(&cred->usage);
 140         return cred;
 141 }
 142
 143 /**
 144  * put_cred - Release a reference to a set of credentials
 145  * @cred: The credentials to release
 146  *
 147  * Release a reference to a set of credentials, deleting them when the last ref
 148  * is released.
 149  */
 150 static inline void put_cred(const struct cred *_cred)
 151 {
 152         struct cred *cred = (struct cred *) _cred;
 153         if (atomic_dec_and_test(&(cred)->usage))
 154                 __put_cred(cred);
 155 }
 156
 157 /**
 158  * current_cred - Access the current task's credentials
 159  *
 160  * Access the credentials of the current task.
 161  */
 162 #define current_cred() \
 163         (current->cred)
 164
 165 /**
 166  * __task_cred - Access another task's credentials
 167  * @task: The task to query
 168  *
 169  * Access the credentials of another task.  The caller must hold the
 170  * RCU readlock.
 171  *
 172  * The caller must make sure task doesn't go away, either by holding a ref on
 173  * task or by holding tasklist_lock to prevent it from being unlinked.
 174  */
 175 #define __task_cred(task) \
 176         ((const struct cred *)(rcu_dereference((task)->cred)))
 177
 178 /**
 179  * get_task_cred - Get another task's credentials
 180  * @task: The task to query
 181  *
 182  * Get the credentials of a task, pinning them so that they can't go away.
 183  * Accessing a task's credentials directly is not permitted.
 184  *
 185  * The caller must make sure task doesn't go away, either by holding a ref on
 186  * task or by holding tasklist_lock to prevent it from being unlinked.
 187  */
 188 #define get_task_cred(task)                             \
 189 ({                                                      \
 190         struct cred *__cred;                            \
 191         rcu_read_lock();                                \
 192         __cred = (struct cred *) __task_cred((task));   \
 193         get_cred(__cred);                               \
 194         rcu_read_unlock();                              \
 195         __cred;                                         \
 196 })
 197
 198 /**
 199  * get_current_cred - Get the current task's credentials
 200  *
 201  * Get the credentials of the current task, pinning them so that they can't go
 202  * away.  Accessing the current task's credentials directly is not permitted.
 203  */
 204 #define get_current_cred()                              \
 205         (get_cred(current_cred()))
 206
 207 /**
 208  * get_current_user - Get the current task's user_struct
 209  *
 210  * Get the user record of the current task, pinning it so that it can't go
 211  * away.
 212  */
 213 #define get_current_user()                              \
 214 ({                                                      \
 215         struct user_struct *__u;                        \
 216         struct cred *__cred;                            \
 217         __cred = (struct cred *) current_cred();        \
 218         __u = get_uid(__cred->user);                    \
 219         __u;                                            \
 220 })
 221
 222 /**
 223  * get_current_groups - Get the current task's supplementary group list
 224  *
 225  * Get the supplementary group list of the current task, pinning it so that it
 226  * can't go away.
 227  */
 228 #define get_current_groups()                            \
 229 ({                                                      \
 230         struct group_info *__groups;                    \
 231         struct cred *__cred;                            \
 232         __cred = (struct cred *) current_cred();        \
 233         __groups = get_group_info(__cred->group_info);  \
 234         __groups;                                       \
 235 })
 236
 237 #define task_cred_xxx(task, xxx)                \
 238 ({                                              \
 239         __typeof__(task->cred->xxx) ___val;     \
 240         rcu_read_lock();                        \
 241         ___val = __task_cred((task))->xxx;      \
 242         rcu_read_unlock();                      \
 243         ___val;                                 \
 244 })
 245
 246 #define task_uid(task)          (task_cred_xxx((task), uid))
 247 #define task_euid(task)         (task_cred_xxx((task), euid))
 248
 249 #define current_cred_xxx(xxx)                   \
 250 ({                                              \
 251         current->cred->xxx;                     \
 252 })
 253
 254 #define current_uid()           (current_cred_xxx(uid))
 255 #define current_gid()           (current_cred_xxx(gid))
 256 #define current_euid()          (current_cred_xxx(euid))
 257 #define current_egid()          (current_cred_xxx(egid))
 258 #define current_suid()          (current_cred_xxx(suid))
 259 #define current_sgid()          (current_cred_xxx(sgid))
 260 #define current_fsuid()         (current_cred_xxx(fsuid))
 261 #define current_fsgid()         (current_cred_xxx(fsgid))
 262 #define current_cap()           (current_cred_xxx(cap_effective))
 263 #define current_user()          (current_cred_xxx(user))
 264 #define current_security()      (current_cred_xxx(security))
 265
 266 #define current_uid_gid(_uid, _gid)             \
 267 do {                                            \
 268         const struct cred *__cred;              \
 269         __cred = current_cred();                \
 270         *(_uid) = __cred->uid;                  \
 271         *(_gid) = __cred->gid;                  \
 272 } while(0)
 273
 274 #define current_euid_egid(_euid, _egid)         \
 275 do {                                            \
 276         const struct cred *__cred;              \
 277         __cred = current_cred();                \
 278         *(_euid) = __cred->euid;                \
 279         *(_egid) = __cred->egid;                \
 280 } while(0)
 281
 282 #define current_fsuid_fsgid(_fsuid, _fsgid)     \
 283 do {                                            \
 284         const struct cred *__cred;              \
 285         __cred = current_cred();                \
 286         *(_fsuid) = __cred->fsuid;              \
 287         *(_fsgid) = __cred->fsgid;              \
 288 } while(0)
 289
 290 #endif /* _LINUX_CRED_H */