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   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
  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 };
 141
 142 extern void __put_cred(struct cred *);
 143 extern int copy_creds(struct task_struct *, unsigned long);
 144 extern struct cred *prepare_creds(void);
 145 extern struct cred *prepare_exec_creds(void);
 146 extern struct cred *prepare_usermodehelper_creds(void);
 147 extern int commit_creds(struct cred *);
 148 extern void abort_creds(struct cred *);
 149 extern const struct cred *override_creds(const struct cred *);
 150 extern void revert_creds(const struct cred *);
 151 extern void __init cred_init(void);
 152
 153 /**
 154  * get_new_cred - Get a reference on a new set of credentials
 155  * @cred: The new credentials to reference
 156  *
 157  * Get a reference on the specified set of new credentials.  The caller must
 158  * release the reference.
 159  */
 160 static inline struct cred *get_new_cred(struct cred *cred)
 161 {
 162         atomic_inc(&cred->usage);
 163         return cred;
 164 }
 165
 166 /**
 167  * get_cred - Get a reference on a set of credentials
 168  * @cred: The credentials to reference
 169  *
 170  * Get a reference on the specified set of credentials.  The caller must
 171  * release the reference.
 172  *
 173  * This is used to deal with a committed set of credentials.  Although the
 174  * pointer is const, this will temporarily discard the const and increment the
 175  * usage count.  The purpose of this is to attempt to catch at compile time the
 176  * accidental alteration of a set of credentials that should be considered
 177  * immutable.
 178  */
 179 static inline const struct cred *get_cred(const struct cred *cred)
 180 {
 181         return get_new_cred((struct cred *) cred);
 182 }
 183
 184 /**
 185  * put_cred - Release a reference to a set of credentials
 186  * @cred: The credentials to release
 187  *
 188  * Release a reference to a set of credentials, deleting them when the last ref
 189  * is released.
 190  *
 191  * This takes a const pointer to a set of credentials because the credentials
 192  * on task_struct are attached by const pointers to prevent accidental
 193  * alteration of otherwise immutable credential sets.
 194  */
 195 static inline void put_cred(const struct cred *_cred)
 196 {
 197         struct cred *cred = (struct cred *) _cred;
 198
 199         BUG_ON(atomic_read(&(cred)->usage) <= 0);
 200         if (atomic_dec_and_test(&(cred)->usage))
 201                 __put_cred(cred);
 202 }
 203
 204 /**
 205  * current_cred - Access the current task's subjective credentials
 206  *
 207  * Access the subjective credentials of the current task.
 208  */
 209 #define current_cred() \
 210         (current->cred)
 211
 212 /**
 213  * __task_cred - Access a task's objective credentials
 214  * @task: The task to query
 215  *
 216  * Access the objective credentials of a task.  The caller must hold the RCU
 217  * readlock.
 218  *
 219  * The caller must make sure task doesn't go away, either by holding a ref on
 220  * task or by holding tasklist_lock to prevent it from being unlinked.
 221  */
 222 #define __task_cred(task) \
 223         ((const struct cred *)(rcu_dereference((task)->real_cred)))
 224
 225 /**
 226  * get_task_cred - Get another task's objective credentials
 227  * @task: The task to query
 228  *
 229  * Get the objective credentials of a task, pinning them so that they can't go
 230  * away.  Accessing a task's credentials directly is not permitted.
 231  *
 232  * The caller must make sure task doesn't go away, either by holding a ref on
 233  * task or by holding tasklist_lock to prevent it from being unlinked.
 234  */
 235 #define get_task_cred(task)                             \
 236 ({                                                      \
 237         struct cred *__cred;                            \
 238         rcu_read_lock();                                \
 239         __cred = (struct cred *) __task_cred((task));   \
 240         get_cred(__cred);                               \
 241         rcu_read_unlock();                              \
 242         __cred;                                         \
 243 })
 244
 245 /**
 246  * get_current_cred - Get the current task's subjective credentials
 247  *
 248  * Get the subjective credentials of the current task, pinning them so that
 249  * they can't go away.  Accessing the current task's credentials directly is
 250  * not permitted.
 251  */
 252 #define get_current_cred()                              \
 253         (get_cred(current_cred()))
 254
 255 /**
 256  * get_current_user - Get the current task's user_struct
 257  *
 258  * Get the user record of the current task, pinning it so that it can't go
 259  * away.
 260  */
 261 #define get_current_user()                              \
 262 ({                                                      \
 263         struct user_struct *__u;                        \
 264         struct cred *__cred;                            \
 265         __cred = (struct cred *) current_cred();        \
 266         __u = get_uid(__cred->user);                    \
 267         __u;                                            \
 268 })
 269
 270 /**
 271  * get_current_groups - Get the current task's supplementary group list
 272  *
 273  * Get the supplementary group list of the current task, pinning it so that it
 274  * can't go away.
 275  */
 276 #define get_current_groups()                            \
 277 ({                                                      \
 278         struct group_info *__groups;                    \
 279         struct cred *__cred;                            \
 280         __cred = (struct cred *) current_cred();        \
 281         __groups = get_group_info(__cred->group_info);  \
 282         __groups;                                       \
 283 })
 284
 285 #define task_cred_xxx(task, xxx)                        \
 286 ({                                                      \
 287         __typeof__(((struct cred *)NULL)->xxx) ___val;  \
 288         rcu_read_lock();                                \
 289         ___val = __task_cred((task))->xxx;              \
 290         rcu_read_unlock();                              \
 291         ___val;                                         \
 292 })
 293
 294 #define task_uid(task)          (task_cred_xxx((task), uid))
 295 #define task_euid(task)         (task_cred_xxx((task), euid))
 296
 297 #define current_cred_xxx(xxx)                   \
 298 ({                                              \
 299         current->cred->xxx;                     \
 300 })
 301
 302 #define current_uid()           (current_cred_xxx(uid))
 303 #define current_gid()           (current_cred_xxx(gid))
 304 #define current_euid()          (current_cred_xxx(euid))
 305 #define current_egid()          (current_cred_xxx(egid))
 306 #define current_suid()          (current_cred_xxx(suid))
 307 #define current_sgid()          (current_cred_xxx(sgid))
 308 #define current_fsuid()         (current_cred_xxx(fsuid))
 309 #define current_fsgid()         (current_cred_xxx(fsgid))
 310 #define current_cap()           (current_cred_xxx(cap_effective))
 311 #define current_user()          (current_cred_xxx(user))
 312 #define current_security()      (current_cred_xxx(security))
 313
 314 #define current_uid_gid(_uid, _gid)             \
 315 do {                                            \
 316         const struct cred *__cred;              \
 317         __cred = current_cred();                \
 318         *(_uid) = __cred->uid;                  \
 319         *(_gid) = __cred->gid;                  \
 320 } while(0)
 321
 322 #define current_euid_egid(_euid, _egid)         \
 323 do {                                            \
 324         const struct cred *__cred;              \
 325         __cred = current_cred();                \
 326         *(_euid) = __cred->euid;                \
 327         *(_egid) = __cred->egid;                \
 328 } while(0)
 329
 330 #define current_fsuid_fsgid(_fsuid, _fsgid)     \
 331 do {                                            \
 332         const struct cred *__cred;              \
 333         __cred = current_cred();                \
 334         *(_fsuid) = __cred->fsuid;              \
 335         *(_fsgid) = __cred->fsgid;              \
 336 } while(0)
 337
 338 #endif /* _LINUX_CRED_H */