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 struct group_info init_groups;
  64 extern void groups_free(struct group_info *);
  65 extern int set_current_groups(struct group_info *);
  66 extern int set_groups(struct cred *, struct group_info *);
  67 extern int groups_search(const struct group_info *, gid_t);
  68
  69 /* access the groups "array" with this macro */
  70 #define GROUP_AT(gi, i) \
  71         ((gi)->blocks[(i) / NGROUPS_PER_BLOCK][(i) % NGROUPS_PER_BLOCK])
  72
  73 extern int in_group_p(gid_t);
  74 extern int in_egroup_p(gid_t);
  75
  76 /*
  77  * The common credentials for a thread group
  78  * - shared by CLONE_THREAD
  79  */
  80 #ifdef CONFIG_KEYS
  81 struct thread_group_cred {
  82         atomic_t        usage;
  83         pid_t           tgid;                   /* thread group process ID */
  84         spinlock_t      lock;
  85         struct key      *session_keyring;       /* keyring inherited over fork */
  86         struct key      *process_keyring;       /* keyring private to this process */
  87         struct rcu_head rcu;                    /* RCU deletion hook */
  88 };
  89 #endif
  90
  91 /*
  92  * The security context of a task
  93  *
  94  * The parts of the context break down into two categories:
  95  *
  96  *  (1) The objective context of a task.  These parts are used when some other
  97  *      task is attempting to affect this one.
  98  *
  99  *  (2) The subjective context.  These details are used when the task is acting
 100  *      upon another object, be that a file, a task, a key or whatever.
 101  *
 102  * Note that some members of this structure belong to both categories - the
 103  * LSM security pointer for instance.
 104  *
 105  * A task has two security pointers.  task->real_cred points to the objective
 106  * context that defines that task's actual details.  The objective part of this
 107  * context is used whenever that task is acted upon.
 108  *
 109  * task->cred points to the subjective context that defines the details of how
 110  * that task is going to act upon another object.  This may be overridden
 111  * temporarily to point to another security context, but normally points to the
 112  * same context as task->real_cred.
 113  */
 114 struct cred {
 115         atomic_t        usage;
 116         uid_t           uid;            /* real UID of the task */
 117         gid_t           gid;            /* real GID of the task */
 118         uid_t           suid;           /* saved UID of the task */
 119         gid_t           sgid;           /* saved GID of the task */
 120         uid_t           euid;           /* effective UID of the task */
 121         gid_t           egid;           /* effective GID of the task */
 122         uid_t           fsuid;          /* UID for VFS ops */
 123         gid_t           fsgid;          /* GID for VFS ops */
 124         unsigned        securebits;     /* SUID-less security management */
 125         kernel_cap_t    cap_inheritable; /* caps our children can inherit */
 126         kernel_cap_t    cap_permitted;  /* caps we're permitted */
 127         kernel_cap_t    cap_effective;  /* caps we can actually use */
 128         kernel_cap_t    cap_bset;       /* capability bounding set */
 129 #ifdef CONFIG_KEYS
 130         unsigned char   jit_keyring;    /* default keyring to attach requested
 131                                          * keys to */
 132         struct key      *thread_keyring; /* keyring private to this thread */
 133         struct key      *request_key_auth; /* assumed request_key authority */
 134         struct thread_group_cred *tgcred; /* thread-group shared credentials */
 135 #endif
 136 #ifdef CONFIG_SECURITY
 137         void            *security;      /* subjective LSM security */
 138 #endif
 139         struct user_struct *user;       /* real user ID subscription */
 140         struct group_info *group_info;  /* supplementary groups for euid/fsgid */
 141         struct rcu_head rcu;            /* RCU deletion hook */
 142 };
 143
 144 extern void __put_cred(struct cred *);
 145 extern int copy_creds(struct task_struct *, unsigned long);
 146 extern struct cred *prepare_creds(void);
 147 extern struct cred *prepare_exec_creds(void);
 148 extern struct cred *prepare_usermodehelper_creds(void);
 149 extern int commit_creds(struct cred *);
 150 extern void abort_creds(struct cred *);
 151 extern const struct cred *override_creds(const struct cred *);
 152 extern void revert_creds(const struct cred *);
 153 extern struct cred *prepare_kernel_cred(struct task_struct *);
 154 extern int change_create_files_as(struct cred *, struct inode *);
 155 extern int set_security_override(struct cred *, u32);
 156 extern int set_security_override_from_ctx(struct cred *, const char *);
 157 extern int set_create_files_as(struct cred *, struct inode *);
 158 extern void __init cred_init(void);
 159
 160 /**
 161  * get_new_cred - Get a reference on a new set of credentials
 162  * @cred: The new credentials to reference
 163  *
 164  * Get a reference on the specified set of new credentials.  The caller must
 165  * release the reference.
 166  */
 167 static inline struct cred *get_new_cred(struct cred *cred)
 168 {
 169         atomic_inc(&cred->usage);
 170         return cred;
 171 }
 172
 173 /**
 174  * get_cred - Get a reference on a set of credentials
 175  * @cred: The credentials to reference
 176  *
 177  * Get a reference on the specified set of credentials.  The caller must
 178  * release the reference.
 179  *
 180  * This is used to deal with a committed set of credentials.  Although the
 181  * pointer is const, this will temporarily discard the const and increment the
 182  * usage count.  The purpose of this is to attempt to catch at compile time the
 183  * accidental alteration of a set of credentials that should be considered
 184  * immutable.
 185  */
 186 static inline const struct cred *get_cred(const struct cred *cred)
 187 {
 188         return get_new_cred((struct cred *) cred);
 189 }
 190
 191 /**
 192  * put_cred - Release a reference to a set of credentials
 193  * @cred: The credentials to release
 194  *
 195  * Release a reference to a set of credentials, deleting them when the last ref
 196  * is released.
 197  *
 198  * This takes a const pointer to a set of credentials because the credentials
 199  * on task_struct are attached by const pointers to prevent accidental
 200  * alteration of otherwise immutable credential sets.
 201  */
 202 static inline void put_cred(const struct cred *_cred)
 203 {
 204         struct cred *cred = (struct cred *) _cred;
 205
 206         BUG_ON(atomic_read(&(cred)->usage) <= 0);
 207         if (atomic_dec_and_test(&(cred)->usage))
 208                 __put_cred(cred);
 209 }
 210
 211 /**
 212  * current_cred - Access the current task's subjective credentials
 213  *
 214  * Access the subjective credentials of the current task.
 215  */
 216 #define current_cred() \
 217         (current->cred)
 218
 219 /**
 220  * __task_cred - Access a task's objective credentials
 221  * @task: The task to query
 222  *
 223  * Access the objective credentials of a task.  The caller must hold the RCU
 224  * readlock.
 225  *
 226  * The caller must make sure task doesn't go away, either by holding a ref on
 227  * task or by holding tasklist_lock to prevent it from being unlinked.
 228  */
 229 #define __task_cred(task) \
 230         ((const struct cred *)(rcu_dereference((task)->real_cred)))
 231
 232 /**
 233  * get_task_cred - Get another task's objective credentials
 234  * @task: The task to query
 235  *
 236  * Get the objective credentials of a task, pinning them so that they can't go
 237  * away.  Accessing a task's credentials directly is not permitted.
 238  *
 239  * The caller must make sure task doesn't go away, either by holding a ref on
 240  * task or by holding tasklist_lock to prevent it from being unlinked.
 241  */
 242 #define get_task_cred(task)                             \
 243 ({                                                      \
 244         struct cred *__cred;                            \
 245         rcu_read_lock();                                \
 246         __cred = (struct cred *) __task_cred((task));   \
 247         get_cred(__cred);                               \
 248         rcu_read_unlock();                              \
 249         __cred;                                         \
 250 })
 251
 252 /**
 253  * get_current_cred - Get the current task's subjective credentials
 254  *
 255  * Get the subjective credentials of the current task, pinning them so that
 256  * they can't go away.  Accessing the current task's credentials directly is
 257  * not permitted.
 258  */
 259 #define get_current_cred()                              \
 260         (get_cred(current_cred()))
 261
 262 /**
 263  * get_current_user - Get the current task's user_struct
 264  *
 265  * Get the user record of the current task, pinning it so that it can't go
 266  * away.
 267  */
 268 #define get_current_user()                              \
 269 ({                                                      \
 270         struct user_struct *__u;                        \
 271         struct cred *__cred;                            \
 272         __cred = (struct cred *) current_cred();        \
 273         __u = get_uid(__cred->user);                    \
 274         __u;                                            \
 275 })
 276
 277 /**
 278  * get_current_groups - Get the current task's supplementary group list
 279  *
 280  * Get the supplementary group list of the current task, pinning it so that it
 281  * can't go away.
 282  */
 283 #define get_current_groups()                            \
 284 ({                                                      \
 285         struct group_info *__groups;                    \
 286         struct cred *__cred;                            \
 287         __cred = (struct cred *) current_cred();        \
 288         __groups = get_group_info(__cred->group_info);  \
 289         __groups;                                       \
 290 })
 291
 292 #define task_cred_xxx(task, xxx)                        \
 293 ({                                                      \
 294         __typeof__(((struct cred *)NULL)->xxx) ___val;  \
 295         rcu_read_lock();                                \
 296         ___val = __task_cred((task))->xxx;              \
 297         rcu_read_unlock();                              \
 298         ___val;                                         \
 299 })
 300
 301 #define task_uid(task)          (task_cred_xxx((task), uid))
 302 #define task_euid(task)         (task_cred_xxx((task), euid))
 303
 304 #define current_cred_xxx(xxx)                   \
 305 ({                                              \
 306         current->cred->xxx;                     \
 307 })
 308
 309 #define current_uid()           (current_cred_xxx(uid))
 310 #define current_gid()           (current_cred_xxx(gid))
 311 #define current_euid()          (current_cred_xxx(euid))
 312 #define current_egid()          (current_cred_xxx(egid))
 313 #define current_suid()          (current_cred_xxx(suid))
 314 #define current_sgid()          (current_cred_xxx(sgid))
 315 #define current_fsuid()         (current_cred_xxx(fsuid))
 316 #define current_fsgid()         (current_cred_xxx(fsgid))
 317 #define current_cap()           (current_cred_xxx(cap_effective))
 318 #define current_user()          (current_cred_xxx(user))
 319 #define current_user_ns()       (current_cred_xxx(user)->user_ns)
 320 #define current_security()      (current_cred_xxx(security))
 321
 322 #define current_uid_gid(_uid, _gid)             \
 323 do {                                            \
 324         const struct cred *__cred;              \
 325         __cred = current_cred();                \
 326         *(_uid) = __cred->uid;                  \
 327         *(_gid) = __cred->gid;                  \
 328 } while(0)
 329
 330 #define current_euid_egid(_euid, _egid)         \
 331 do {                                            \
 332         const struct cred *__cred;              \
 333         __cred = current_cred();                \
 334         *(_euid) = __cred->euid;                \
 335         *(_egid) = __cred->egid;                \
 336 } while(0)
 337
 338 #define current_fsuid_fsgid(_fsuid, _fsgid)     \
 339 do {                                            \
 340         const struct cred *__cred;              \
 341         __cred = current_cred();                \
 342         *(_fsuid) = __cred->fsuid;              \
 343         *(_fsgid) = __cred->fsgid;              \
 344 } while(0)
 345
 346 #endif /* _LINUX_CRED_H */