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
  88 extern void release_tgcred(struct cred *cred);
  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_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 *) __deprecated;
 151 extern void revert_creds(const struct cred *) __deprecated;
 152 extern void __init cred_init(void);
 153
 154 /**
 155  * get_new_cred - Get a reference on a new set of credentials
 156  * @cred: The new credentials to reference
 157  *
 158  * Get a reference on the specified set of new credentials.  The caller must
 159  * release the reference.
 160  */
 161 static inline struct cred *get_new_cred(struct cred *cred)
 162 {
 163         atomic_inc(&cred->usage);
 164         return cred;
 165 }
 166
 167 /**
 168  * get_cred - Get a reference on a set of credentials
 169  * @cred: The credentials to reference
 170  *
 171  * Get a reference on the specified set of credentials.  The caller must
 172  * release the reference.
 173  */
 174 static inline const struct cred *get_cred(const struct cred *cred)
 175 {
 176         return get_new_cred((struct cred *) cred);
 177 }
 178
 179 /**
 180  * put_cred - Release a reference to a set of credentials
 181  * @cred: The credentials to release
 182  *
 183  * Release a reference to a set of credentials, deleting them when the last ref
 184  * is released.
 185  */
 186 static inline void put_cred(const struct cred *_cred)
 187 {
 188         struct cred *cred = (struct cred *) _cred;
 189
 190         BUG_ON(atomic_read(&(cred)->usage) <= 0);
 191         if (atomic_dec_and_test(&(cred)->usage))
 192                 __put_cred(cred);
 193 }
 194
 195 /**
 196  * current_cred - Access the current task's credentials
 197  *
 198  * Access the credentials of the current task.
 199  */
 200 #define current_cred() \
 201         (current->cred)
 202
 203 /**
 204  * __task_cred - Access another task's credentials
 205  * @task: The task to query
 206  *
 207  * Access the credentials of another task.  The caller must hold the
 208  * RCU readlock.
 209  *
 210  * The caller must make sure task doesn't go away, either by holding a ref on
 211  * task or by holding tasklist_lock to prevent it from being unlinked.
 212  */
 213 #define __task_cred(task) \
 214         ((const struct cred *)(rcu_dereference((task)->cred)))
 215
 216 /**
 217  * get_task_cred - Get another task's credentials
 218  * @task: The task to query
 219  *
 220  * Get the credentials of a task, pinning them so that they can't go away.
 221  * Accessing a task's credentials directly is not permitted.
 222  *
 223  * The caller must make sure task doesn't go away, either by holding a ref on
 224  * task or by holding tasklist_lock to prevent it from being unlinked.
 225  */
 226 #define get_task_cred(task)                             \
 227 ({                                                      \
 228         struct cred *__cred;                            \
 229         rcu_read_lock();                                \
 230         __cred = (struct cred *) __task_cred((task));   \
 231         get_cred(__cred);                               \
 232         rcu_read_unlock();                              \
 233         __cred;                                         \
 234 })
 235
 236 /**
 237  * get_current_cred - Get the current task's credentials
 238  *
 239  * Get the credentials of the current task, pinning them so that they can't go
 240  * away.  Accessing the current task's credentials directly is not permitted.
 241  */
 242 #define get_current_cred()                              \
 243         (get_cred(current_cred()))
 244
 245 /**
 246  * get_current_user - Get the current task's user_struct
 247  *
 248  * Get the user record of the current task, pinning it so that it can't go
 249  * away.
 250  */
 251 #define get_current_user()                              \
 252 ({                                                      \
 253         struct user_struct *__u;                        \
 254         struct cred *__cred;                            \
 255         __cred = (struct cred *) current_cred();        \
 256         __u = get_uid(__cred->user);                    \
 257         __u;                                            \
 258 })
 259
 260 /**
 261  * get_current_groups - Get the current task's supplementary group list
 262  *
 263  * Get the supplementary group list of the current task, pinning it so that it
 264  * can't go away.
 265  */
 266 #define get_current_groups()                            \
 267 ({                                                      \
 268         struct group_info *__groups;                    \
 269         struct cred *__cred;                            \
 270         __cred = (struct cred *) current_cred();        \
 271         __groups = get_group_info(__cred->group_info);  \
 272         __groups;                                       \
 273 })
 274
 275 #define task_cred_xxx(task, xxx)                        \
 276 ({                                                      \
 277         __typeof__(((struct cred *)NULL)->xxx) ___val;  \
 278         rcu_read_lock();                                \
 279         ___val = __task_cred((task))->xxx;              \
 280         rcu_read_unlock();                              \
 281         ___val;                                         \
 282 })
 283
 284 #define task_uid(task)          (task_cred_xxx((task), uid))
 285 #define task_euid(task)         (task_cred_xxx((task), euid))
 286
 287 #define current_cred_xxx(xxx)                   \
 288 ({                                              \
 289         current->cred->xxx;                     \
 290 })
 291
 292 #define current_uid()           (current_cred_xxx(uid))
 293 #define current_gid()           (current_cred_xxx(gid))
 294 #define current_euid()          (current_cred_xxx(euid))
 295 #define current_egid()          (current_cred_xxx(egid))
 296 #define current_suid()          (current_cred_xxx(suid))
 297 #define current_sgid()          (current_cred_xxx(sgid))
 298 #define current_fsuid()         (current_cred_xxx(fsuid))
 299 #define current_fsgid()         (current_cred_xxx(fsgid))
 300 #define current_cap()           (current_cred_xxx(cap_effective))
 301 #define current_user()          (current_cred_xxx(user))
 302 #define current_security()      (current_cred_xxx(security))
 303
 304 #define current_uid_gid(_uid, _gid)             \
 305 do {                                            \
 306         const struct cred *__cred;              \
 307         __cred = current_cred();                \
 308         *(_uid) = __cred->uid;                  \
 309         *(_gid) = __cred->gid;                  \
 310 } while(0)
 311
 312 #define current_euid_egid(_euid, _egid)         \
 313 do {                                            \
 314         const struct cred *__cred;              \
 315         __cred = current_cred();                \
 316         *(_euid) = __cred->euid;                \
 317         *(_egid) = __cred->egid;                \
 318 } while(0)
 319
 320 #define current_fsuid_fsgid(_fsuid, _fsgid)     \
 321 do {                                            \
 322         const struct cred *__cred;              \
 323         __cred = current_cred();                \
 324         *(_fsuid) = __cred->fsuid;              \
 325         *(_fsgid) = __cred->fsgid;              \
 326 } while(0)
 327
 328 #endif /* _LINUX_CRED_H */