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/init.h>
  17 #include <linux/key.h>
  18 #include <asm/atomic.h>
  19
  20 struct user_struct;
  21 struct cred;
  22 struct inode;
  23
  24 /*
  25  * COW Supplementary groups list
  26  */
  27 #define NGROUPS_SMALL           32
  28 #define NGROUPS_PER_BLOCK       ((unsigned int)(PAGE_SIZE / sizeof(gid_t)))
  29
  30 struct group_info {
  31         atomic_t        usage;
  32         int             ngroups;
  33         int             nblocks;
  34         gid_t           small_block[NGROUPS_SMALL];
  35         gid_t           *blocks[0];
  36 };
  37
  38 /**
  39  * get_group_info - Get a reference to a group info structure
  40  * @group_info: The group info to reference
  41  *
  42  * This gets a reference to a set of supplementary groups.
  43  *
  44  * If the caller is accessing a task's credentials, they must hold the RCU read
  45  * lock when reading.
  46  */
  47 static inline struct group_info *get_group_info(struct group_info *gi)
  48 {
  49         atomic_inc(&gi->usage);
  50         return gi;
  51 }
  52
  53 /**
  54  * put_group_info - Release a reference to a group info structure
  55  * @group_info: The group info to release
  56  */
  57 #define put_group_info(group_info)                      \
  58 do {                                                    \
  59         if (atomic_dec_and_test(&(group_info)->usage))  \
  60                 groups_free(group_info);                \
  61 } while (0)
  62
  63 extern struct group_info *groups_alloc(int);
  64 extern struct group_info init_groups;
  65 extern void groups_free(struct group_info *);
  66 extern int set_current_groups(struct group_info *);
  67 extern int set_groups(struct cred *, struct group_info *);
  68 extern int groups_search(const struct group_info *, gid_t);
  69
  70 /* access the groups "array" with this macro */
  71 #define GROUP_AT(gi, i) \
  72         ((gi)->blocks[(i) / NGROUPS_PER_BLOCK][(i) % NGROUPS_PER_BLOCK])
  73
  74 extern int in_group_p(gid_t);
  75 extern int in_egroup_p(gid_t);
  76
  77 /*
  78  * The common credentials for a thread group
  79  * - shared by CLONE_THREAD
  80  */
  81 #ifdef CONFIG_KEYS
  82 struct thread_group_cred {
  83         atomic_t        usage;
  84         pid_t           tgid;                   /* thread group process ID */
  85         spinlock_t      lock;
  86         struct key      *session_keyring;       /* keyring inherited over fork */
  87         struct key      *process_keyring;       /* keyring private to this process */
  88         struct rcu_head rcu;                    /* RCU deletion hook */
  89 };
  90 #endif
  91
  92 /*
  93  * The security context of a task
  94  *
  95  * The parts of the context break down into two categories:
  96  *
  97  *  (1) The objective context of a task.  These parts are used when some other
  98  *      task is attempting to affect this one.
  99  *
 100  *  (2) The subjective context.  These details are used when the task is acting
 101  *      upon another object, be that a file, a task, a key or whatever.
 102  *
 103  * Note that some members of this structure belong to both categories - the
 104  * LSM security pointer for instance.
 105  *
 106  * A task has two security pointers.  task->real_cred points to the objective
 107  * context that defines that task's actual details.  The objective part of this
 108  * context is used whenever that task is acted upon.
 109  *
 110  * task->cred points to the subjective context that defines the details of how
 111  * that task is going to act upon another object.  This may be overridden
 112  * temporarily to point to another security context, but normally points to the
 113  * same context as task->real_cred.
 114  */
 115 struct cred {
 116         atomic_t        usage;
 117         uid_t           uid;            /* real UID of the task */
 118         gid_t           gid;            /* real GID of the task */
 119         uid_t           suid;           /* saved UID of the task */
 120         gid_t           sgid;           /* saved GID of the task */
 121         uid_t           euid;           /* effective UID of the task */
 122         gid_t           egid;           /* effective GID of the task */
 123         uid_t           fsuid;          /* UID for VFS ops */
 124         gid_t           fsgid;          /* GID for VFS ops */
 125         unsigned        securebits;     /* SUID-less security management */
 126         kernel_cap_t    cap_inheritable; /* caps our children can inherit */
 127         kernel_cap_t    cap_permitted;  /* caps we're permitted */
 128         kernel_cap_t    cap_effective;  /* caps we can actually use */
 129         kernel_cap_t    cap_bset;       /* capability bounding set */
 130 #ifdef CONFIG_KEYS
 131         unsigned char   jit_keyring;    /* default keyring to attach requested
 132                                          * keys to */
 133         struct key      *thread_keyring; /* keyring private to this thread */
 134         struct key      *request_key_auth; /* assumed request_key authority */
 135         struct thread_group_cred *tgcred; /* thread-group shared credentials */
 136 #endif
 137 #ifdef CONFIG_SECURITY
 138         void            *security;      /* subjective LSM security */
 139 #endif
 140         struct user_struct *user;       /* real user ID subscription */
 141         struct group_info *group_info;  /* supplementary groups for euid/fsgid */
 142         struct rcu_head rcu;            /* RCU deletion hook */
 143 };
 144
 145 extern void __put_cred(struct cred *);
 146 extern int copy_creds(struct task_struct *, unsigned long);
 147 extern struct cred *prepare_creds(void);
 148 extern struct cred *prepare_exec_creds(void);
 149 extern struct cred *prepare_usermodehelper_creds(void);
 150 extern int commit_creds(struct cred *);
 151 extern void abort_creds(struct cred *);
 152 extern const struct cred *override_creds(const struct cred *);
 153 extern void revert_creds(const struct cred *);
 154 extern struct cred *prepare_kernel_cred(struct task_struct *);
 155 extern int change_create_files_as(struct cred *, struct inode *);
 156 extern int set_security_override(struct cred *, u32);
 157 extern int set_security_override_from_ctx(struct cred *, const char *);
 158 extern int set_create_files_as(struct cred *, struct inode *);
 159 extern void __init cred_init(void);
 160
 161 /**
 162  * get_new_cred - Get a reference on a new set of credentials
 163  * @cred: The new credentials to reference
 164  *
 165  * Get a reference on the specified set of new credentials.  The caller must
 166  * release the reference.
 167  */
 168 static inline struct cred *get_new_cred(struct cred *cred)
 169 {
 170         atomic_inc(&cred->usage);
 171         return cred;
 172 }
 173
 174 /**
 175  * get_cred - Get a reference on a set of credentials
 176  * @cred: The credentials to reference
 177  *
 178  * Get a reference on the specified set of credentials.  The caller must
 179  * release the reference.
 180  *
 181  * This is used to deal with a committed set of credentials.  Although the
 182  * pointer is const, this will temporarily discard the const and increment the
 183  * usage count.  The purpose of this is to attempt to catch at compile time the
 184  * accidental alteration of a set of credentials that should be considered
 185  * immutable.
 186  */
 187 static inline const struct cred *get_cred(const struct cred *cred)
 188 {
 189         return get_new_cred((struct cred *) cred);
 190 }
 191
 192 /**
 193  * put_cred - Release a reference to a set of credentials
 194  * @cred: The credentials to release
 195  *
 196  * Release a reference to a set of credentials, deleting them when the last ref
 197  * is released.
 198  *
 199  * This takes a const pointer to a set of credentials because the credentials
 200  * on task_struct are attached by const pointers to prevent accidental
 201  * alteration of otherwise immutable credential sets.
 202  */
 203 static inline void put_cred(const struct cred *_cred)
 204 {
 205         struct cred *cred = (struct cred *) _cred;
 206
 207         BUG_ON(atomic_read(&(cred)->usage) <= 0);
 208         if (atomic_dec_and_test(&(cred)->usage))
 209                 __put_cred(cred);
 210 }
 211
 212 /**
 213  * current_cred - Access the current task's subjective credentials
 214  *
 215  * Access the subjective credentials of the current task.
 216  */
 217 #define current_cred() \
 218         (current->cred)
 219
 220 /**
 221  * __task_cred - Access a task's objective credentials
 222  * @task: The task to query
 223  *
 224  * Access the objective credentials of a task.  The caller must hold the RCU
 225  * readlock.
 226  *
 227  * The caller must make sure task doesn't go away, either by holding a ref on
 228  * task or by holding tasklist_lock to prevent it from being unlinked.
 229  */
 230 #define __task_cred(task) \
 231         ((const struct cred *)(rcu_dereference((task)->real_cred)))
 232
 233 /**
 234  * get_task_cred - Get another task's objective credentials
 235  * @task: The task to query
 236  *
 237  * Get the objective credentials of a task, pinning them so that they can't go
 238  * away.  Accessing a task's credentials directly is not permitted.
 239  *
 240  * The caller must make sure task doesn't go away, either by holding a ref on
 241  * task or by holding tasklist_lock to prevent it from being unlinked.
 242  */
 243 #define get_task_cred(task)                             \
 244 ({                                                      \
 245         struct cred *__cred;                            \
 246         rcu_read_lock();                                \
 247         __cred = (struct cred *) __task_cred((task));   \
 248         get_cred(__cred);                               \
 249         rcu_read_unlock();                              \
 250         __cred;                                         \
 251 })
 252
 253 /**
 254  * get_current_cred - Get the current task's subjective credentials
 255  *
 256  * Get the subjective credentials of the current task, pinning them so that
 257  * they can't go away.  Accessing the current task's credentials directly is
 258  * not permitted.
 259  */
 260 #define get_current_cred()                              \
 261         (get_cred(current_cred()))
 262
 263 /**
 264  * get_current_user - Get the current task's user_struct
 265  *
 266  * Get the user record of the current task, pinning it so that it can't go
 267  * away.
 268  */
 269 #define get_current_user()                              \
 270 ({                                                      \
 271         struct user_struct *__u;                        \
 272         struct cred *__cred;                            \
 273         __cred = (struct cred *) current_cred();        \
 274         __u = get_uid(__cred->user);                    \
 275         __u;                                            \
 276 })
 277
 278 /**
 279  * get_current_groups - Get the current task's supplementary group list
 280  *
 281  * Get the supplementary group list of the current task, pinning it so that it
 282  * can't go away.
 283  */
 284 #define get_current_groups()                            \
 285 ({                                                      \
 286         struct group_info *__groups;                    \
 287         struct cred *__cred;                            \
 288         __cred = (struct cred *) current_cred();        \
 289         __groups = get_group_info(__cred->group_info);  \
 290         __groups;                                       \
 291 })
 292
 293 #define task_cred_xxx(task, xxx)                        \
 294 ({                                                      \
 295         __typeof__(((struct cred *)NULL)->xxx) ___val;  \
 296         rcu_read_lock();                                \
 297         ___val = __task_cred((task))->xxx;              \
 298         rcu_read_unlock();                              \
 299         ___val;                                         \
 300 })
 301
 302 #define task_uid(task)          (task_cred_xxx((task), uid))
 303 #define task_euid(task)         (task_cred_xxx((task), euid))
 304
 305 #define current_cred_xxx(xxx)                   \
 306 ({                                              \
 307         current->cred->xxx;                     \
 308 })
 309
 310 #define current_uid()           (current_cred_xxx(uid))
 311 #define current_gid()           (current_cred_xxx(gid))
 312 #define current_euid()          (current_cred_xxx(euid))
 313 #define current_egid()          (current_cred_xxx(egid))
 314 #define current_suid()          (current_cred_xxx(suid))
 315 #define current_sgid()          (current_cred_xxx(sgid))
 316 #define current_fsuid()         (current_cred_xxx(fsuid))
 317 #define current_fsgid()         (current_cred_xxx(fsgid))
 318 #define current_cap()           (current_cred_xxx(cap_effective))
 319 #define current_user()          (current_cred_xxx(user))
 320 #define current_user_ns()       (current_cred_xxx(user)->user_ns)
 321 #define current_security()      (current_cred_xxx(security))
 322
 323 #define current_uid_gid(_uid, _gid)             \
 324 do {                                            \
 325         const struct cred *__cred;              \
 326         __cred = current_cred();                \
 327         *(_uid) = __cred->uid;                  \
 328         *(_gid) = __cred->gid;                  \
 329 } while(0)
 330
 331 #define current_euid_egid(_euid, _egid)         \
 332 do {                                            \
 333         const struct cred *__cred;              \
 334         __cred = current_cred();                \
 335         *(_euid) = __cred->euid;                \
 336         *(_egid) = __cred->egid;                \
 337 } while(0)
 338
 339 #define current_fsuid_fsgid(_fsuid, _fsgid)     \
 340 do {                                            \
 341         const struct cred *__cred;              \
 342         __cred = current_cred();                \
 343         *(_fsuid) = __cred->fsuid;              \
 344         *(_fsgid) = __cred->fsgid;              \
 345 } while(0)
 346
 347 #endif /* _LINUX_CRED_H */