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 common credentials for a thread group
  76  * - shared by CLONE_THREAD
  77  */
  78 #ifdef CONFIG_KEYS
  79 struct thread_group_cred {
  80         atomic_t        usage;
  81         pid_t           tgid;                   /* thread group process ID */
  82         spinlock_t      lock;
  83         struct key      *session_keyring;       /* keyring inherited over fork */
  84         struct key      *process_keyring;       /* keyring private to this process */
  85         struct rcu_head rcu;                    /* RCU deletion hook */
  86 };
  87 #endif
  88
  89 /*
  90  * The security context of a task
  91  *
  92  * The parts of the context break down into two categories:
  93  *
  94  *  (1) The objective context of a task.  These parts are used when some other
  95  *      task is attempting to affect this one.
  96  *
  97  *  (2) The subjective context.  These details are used when the task is acting
  98  *      upon another object, be that a file, a task, a key or whatever.
  99  *
 100  * Note that some members of this structure belong to both categories - the
 101  * LSM security pointer for instance.
 102  *
 103  * A task has two security pointers.  task->real_cred points to the objective
 104  * context that defines that task's actual details.  The objective part of this
 105  * context is used whenever that task is acted upon.
 106  *
 107  * task->cred points to the subjective context that defines the details of how
 108  * that task is going to act upon another object.  This may be overridden
 109  * temporarily to point to another security context, but normally points to the
 110  * same context as task->real_cred.
 111  */
 112 struct cred {
 113         atomic_t        usage;
 114         uid_t           uid;            /* real UID of the task */
 115         gid_t           gid;            /* real GID of the task */
 116         uid_t           suid;           /* saved UID of the task */
 117         gid_t           sgid;           /* saved GID of the task */
 118         uid_t           euid;           /* effective UID of the task */
 119         gid_t           egid;           /* effective GID of the task */
 120         uid_t           fsuid;          /* UID for VFS ops */
 121         gid_t           fsgid;          /* GID for VFS ops */
 122         unsigned        securebits;     /* SUID-less security management */
 123         kernel_cap_t    cap_inheritable; /* caps our children can inherit */
 124         kernel_cap_t    cap_permitted;  /* caps we're permitted */
 125         kernel_cap_t    cap_effective;  /* caps we can actually use */
 126         kernel_cap_t    cap_bset;       /* capability bounding set */
 127 #ifdef CONFIG_KEYS
 128         unsigned char   jit_keyring;    /* default keyring to attach requested
 129                                          * keys to */
 130         struct key      *thread_keyring; /* keyring private to this thread */
 131         struct key      *request_key_auth; /* assumed request_key authority */
 132         struct thread_group_cred *tgcred; /* thread-group shared credentials */
 133 #endif
 134 #ifdef CONFIG_SECURITY
 135         void            *security;      /* subjective LSM security */
 136 #endif
 137         struct user_struct *user;       /* real user ID subscription */
 138         struct group_info *group_info;  /* supplementary groups for euid/fsgid */
 139         struct rcu_head rcu;            /* RCU deletion hook */
 140         spinlock_t      lock;           /* lock for pointer changes */
 141 };
 142
 143 extern void __put_cred(struct cred *);
 144 extern int copy_creds(struct task_struct *, unsigned long);
 145
 146 /**
 147  * get_cred - Get a reference on a set of credentials
 148  * @cred: The credentials to reference
 149  *
 150  * Get a reference on the specified set of credentials.  The caller must
 151  * release the reference.
 152  */
 153 static inline struct cred *get_cred(struct cred *cred)
 154 {
 155         atomic_inc(&cred->usage);
 156         return cred;
 157 }
 158
 159 /**
 160  * put_cred - Release a reference to a set of credentials
 161  * @cred: The credentials to release
 162  *
 163  * Release a reference to a set of credentials, deleting them when the last ref
 164  * is released.
 165  */
 166 static inline void put_cred(const struct cred *_cred)
 167 {
 168         struct cred *cred = (struct cred *) _cred;
 169         if (atomic_dec_and_test(&(cred)->usage))
 170                 __put_cred(cred);
 171 }
 172
 173 /**
 174  * current_cred - Access the current task's credentials
 175  *
 176  * Access the credentials of the current task.
 177  */
 178 #define current_cred() \
 179         (current->cred)
 180
 181 /**
 182  * __task_cred - Access another task's credentials
 183  * @task: The task to query
 184  *
 185  * Access the credentials of another task.  The caller must hold the
 186  * RCU readlock.
 187  *
 188  * The caller must make sure task doesn't go away, either by holding a ref on
 189  * task or by holding tasklist_lock to prevent it from being unlinked.
 190  */
 191 #define __task_cred(task) \
 192         ((const struct cred *)(rcu_dereference((task)->cred)))
 193
 194 /**
 195  * get_task_cred - Get another task's credentials
 196  * @task: The task to query
 197  *
 198  * Get the credentials of a task, pinning them so that they can't go away.
 199  * Accessing a task's credentials directly is not permitted.
 200  *
 201  * The caller must make sure task doesn't go away, either by holding a ref on
 202  * task or by holding tasklist_lock to prevent it from being unlinked.
 203  */
 204 #define get_task_cred(task)                             \
 205 ({                                                      \
 206         struct cred *__cred;                            \
 207         rcu_read_lock();                                \
 208         __cred = (struct cred *) __task_cred((task));   \
 209         get_cred(__cred);                               \
 210         rcu_read_unlock();                              \
 211         __cred;                                         \
 212 })
 213
 214 /**
 215  * get_current_cred - Get the current task's credentials
 216  *
 217  * Get the credentials of the current task, pinning them so that they can't go
 218  * away.  Accessing the current task's credentials directly is not permitted.
 219  */
 220 #define get_current_cred()                              \
 221         (get_cred(current_cred()))
 222
 223 /**
 224  * get_current_user - Get the current task's user_struct
 225  *
 226  * Get the user record of the current task, pinning it so that it can't go
 227  * away.
 228  */
 229 #define get_current_user()                              \
 230 ({                                                      \
 231         struct user_struct *__u;                        \
 232         struct cred *__cred;                            \
 233         __cred = (struct cred *) current_cred();        \
 234         __u = get_uid(__cred->user);                    \
 235         __u;                                            \
 236 })
 237
 238 /**
 239  * get_current_groups - Get the current task's supplementary group list
 240  *
 241  * Get the supplementary group list of the current task, pinning it so that it
 242  * can't go away.
 243  */
 244 #define get_current_groups()                            \
 245 ({                                                      \
 246         struct group_info *__groups;                    \
 247         struct cred *__cred;                            \
 248         __cred = (struct cred *) current_cred();        \
 249         __groups = get_group_info(__cred->group_info);  \
 250         __groups;                                       \
 251 })
 252
 253 #define task_cred_xxx(task, xxx)                \
 254 ({                                              \
 255         __typeof__(task->cred->xxx) ___val;     \
 256         rcu_read_lock();                        \
 257         ___val = __task_cred((task))->xxx;      \
 258         rcu_read_unlock();                      \
 259         ___val;                                 \
 260 })
 261
 262 #define task_uid(task)          (task_cred_xxx((task), uid))
 263 #define task_euid(task)         (task_cred_xxx((task), euid))
 264
 265 #define current_cred_xxx(xxx)                   \
 266 ({                                              \
 267         current->cred->xxx;                     \
 268 })
 269
 270 #define current_uid()           (current_cred_xxx(uid))
 271 #define current_gid()           (current_cred_xxx(gid))
 272 #define current_euid()          (current_cred_xxx(euid))
 273 #define current_egid()          (current_cred_xxx(egid))
 274 #define current_suid()          (current_cred_xxx(suid))
 275 #define current_sgid()          (current_cred_xxx(sgid))
 276 #define current_fsuid()         (current_cred_xxx(fsuid))
 277 #define current_fsgid()         (current_cred_xxx(fsgid))
 278 #define current_cap()           (current_cred_xxx(cap_effective))
 279 #define current_user()          (current_cred_xxx(user))
 280 #define current_security()      (current_cred_xxx(security))
 281
 282 #define current_uid_gid(_uid, _gid)             \
 283 do {                                            \
 284         const struct cred *__cred;              \
 285         __cred = current_cred();                \
 286         *(_uid) = __cred->uid;                  \
 287         *(_gid) = __cred->gid;                  \
 288 } while(0)
 289
 290 #define current_euid_egid(_euid, _egid)         \
 291 do {                                            \
 292         const struct cred *__cred;              \
 293         __cred = current_cred();                \
 294         *(_euid) = __cred->euid;                \
 295         *(_egid) = __cred->egid;                \
 296 } while(0)
 297
 298 #define current_fsuid_fsgid(_fsuid, _fsgid)     \
 299 do {                                            \
 300         const struct cred *__cred;              \
 301         __cred = current_cred();                \
 302         *(_fsuid) = __cred->fsuid;              \
 303         *(_fsgid) = __cred->fsgid;              \
 304 } while(0)
 305
 306 #endif /* _LINUX_CRED_H */