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 #ifdef CONFIG_DEBUG_CREDENTIALS
 118         atomic_t        subscribers;    /* number of processes subscribed */
 119         void            *put_addr;
 120         unsigned        magic;
 121 #define CRED_MAGIC      0x43736564
 122 #define CRED_MAGIC_DEAD 0x44656144
 123 #endif
 124         uid_t           uid;            /* real UID of the task */
 125         gid_t           gid;            /* real GID of the task */
 126         uid_t           suid;           /* saved UID of the task */
 127         gid_t           sgid;           /* saved GID of the task */
 128         uid_t           euid;           /* effective UID of the task */
 129         gid_t           egid;           /* effective GID of the task */
 130         uid_t           fsuid;          /* UID for VFS ops */
 131         gid_t           fsgid;          /* GID for VFS ops */
 132         unsigned        securebits;     /* SUID-less security management */
 133         kernel_cap_t    cap_inheritable; /* caps our children can inherit */
 134         kernel_cap_t    cap_permitted;  /* caps we're permitted */
 135         kernel_cap_t    cap_effective;  /* caps we can actually use */
 136         kernel_cap_t    cap_bset;       /* capability bounding set */
 137 #ifdef CONFIG_KEYS
 138         unsigned char   jit_keyring;    /* default keyring to attach requested
 139                                          * keys to */
 140         struct key      *thread_keyring; /* keyring private to this thread */
 141         struct key      *request_key_auth; /* assumed request_key authority */
 142         struct thread_group_cred *tgcred; /* thread-group shared credentials */
 143 #endif
 144 #ifdef CONFIG_SECURITY
 145         void            *security;      /* subjective LSM security */
 146 #endif
 147         struct user_struct *user;       /* real user ID subscription */
 148         struct group_info *group_info;  /* supplementary groups for euid/fsgid */
 149         struct rcu_head rcu;            /* RCU deletion hook */
 150 };
 151
 152 extern void __put_cred(struct cred *);
 153 extern void exit_creds(struct task_struct *);
 154 extern int copy_creds(struct task_struct *, unsigned long);
 155 extern struct cred *prepare_creds(void);
 156 extern struct cred *prepare_exec_creds(void);
 157 extern struct cred *prepare_usermodehelper_creds(void);
 158 extern int commit_creds(struct cred *);
 159 extern void abort_creds(struct cred *);
 160 extern const struct cred *override_creds(const struct cred *);
 161 extern void revert_creds(const struct cred *);
 162 extern struct cred *prepare_kernel_cred(struct task_struct *);
 163 extern int change_create_files_as(struct cred *, struct inode *);
 164 extern int set_security_override(struct cred *, u32);
 165 extern int set_security_override_from_ctx(struct cred *, const char *);
 166 extern int set_create_files_as(struct cred *, struct inode *);
 167 extern void __init cred_init(void);
 168
 169 /*
 170  * check for validity of credentials
 171  */
 172 #ifdef CONFIG_DEBUG_CREDENTIALS
 173 extern void __invalid_creds(const struct cred *, const char *, unsigned);
 174 extern void __validate_process_creds(struct task_struct *,
 175                                      const char *, unsigned);
 176
 177 static inline bool creds_are_invalid(const struct cred *cred)
 178 {
 179         if (cred->magic != CRED_MAGIC)
 180                 return true;
 181         if (atomic_read(&cred->usage) < atomic_read(&cred->subscribers))
 182                 return true;
 183 #ifdef CONFIG_SECURITY_SELINUX
 184         if ((unsigned long) cred->security < PAGE_SIZE)
 185                 return true;
 186         if ((*(u32*)cred->security & 0xffffff00) ==
 187             (POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8))
 188                 return true;
 189 #endif
 190         return false;
 191 }
 192
 193 static inline void __validate_creds(const struct cred *cred,
 194                                     const char *file, unsigned line)
 195 {
 196         if (unlikely(creds_are_invalid(cred)))
 197                 __invalid_creds(cred, file, line);
 198 }
 199
 200 #define validate_creds(cred)                            \
 201 do {                                                    \
 202         __validate_creds((cred), __FILE__, __LINE__);   \
 203 } while(0)
 204
 205 #define validate_process_creds()                                \
 206 do {                                                            \
 207         __validate_process_creds(current, __FILE__, __LINE__);  \
 208 } while(0)
 209
 210 extern void validate_creds_for_do_exit(struct task_struct *);
 211 #else
 212 static inline void validate_creds(const struct cred *cred)
 213 {
 214 }
 215 static inline void validate_creds_for_do_exit(struct task_struct *tsk)
 216 {
 217 }
 218 static inline void validate_process_creds(void)
 219 {
 220 }
 221 #endif
 222
 223 /**
 224  * get_new_cred - Get a reference on a new set of credentials
 225  * @cred: The new credentials to reference
 226  *
 227  * Get a reference on the specified set of new credentials.  The caller must
 228  * release the reference.
 229  */
 230 static inline struct cred *get_new_cred(struct cred *cred)
 231 {
 232         atomic_inc(&cred->usage);
 233         return cred;
 234 }
 235
 236 /**
 237  * get_cred - Get a reference on a set of credentials
 238  * @cred: The credentials to reference
 239  *
 240  * Get a reference on the specified set of credentials.  The caller must
 241  * release the reference.
 242  *
 243  * This is used to deal with a committed set of credentials.  Although the
 244  * pointer is const, this will temporarily discard the const and increment the
 245  * usage count.  The purpose of this is to attempt to catch at compile time the
 246  * accidental alteration of a set of credentials that should be considered
 247  * immutable.
 248  */
 249 static inline const struct cred *get_cred(const struct cred *cred)
 250 {
 251         struct cred *nonconst_cred = (struct cred *) cred;
 252         validate_creds(cred);
 253         return get_new_cred(nonconst_cred);
 254 }
 255
 256 /**
 257  * put_cred - Release a reference to a set of credentials
 258  * @cred: The credentials to release
 259  *
 260  * Release a reference to a set of credentials, deleting them when the last ref
 261  * is released.
 262  *
 263  * This takes a const pointer to a set of credentials because the credentials
 264  * on task_struct are attached by const pointers to prevent accidental
 265  * alteration of otherwise immutable credential sets.
 266  */
 267 static inline void put_cred(const struct cred *_cred)
 268 {
 269         struct cred *cred = (struct cred *) _cred;
 270
 271         validate_creds(cred);
 272         if (atomic_dec_and_test(&(cred)->usage))
 273                 __put_cred(cred);
 274 }
 275
 276 /**
 277  * current_cred - Access the current task's subjective credentials
 278  *
 279  * Access the subjective credentials of the current task.
 280  */
 281 #define current_cred() \
 282         (current->cred)
 283
 284 /**
 285  * __task_cred - Access a task's objective credentials
 286  * @task: The task to query
 287  *
 288  * Access the objective credentials of a task.  The caller must hold the RCU
 289  * readlock.
 290  *
 291  * The caller must make sure task doesn't go away, either by holding a ref on
 292  * task or by holding tasklist_lock to prevent it from being unlinked.
 293  */
 294 #define __task_cred(task) \
 295         ((const struct cred *)(rcu_dereference((task)->real_cred)))
 296
 297 /**
 298  * get_task_cred - Get another task's objective credentials
 299  * @task: The task to query
 300  *
 301  * Get the objective credentials of a task, pinning them so that they can't go
 302  * away.  Accessing a task's credentials directly is not permitted.
 303  *
 304  * The caller must make sure task doesn't go away, either by holding a ref on
 305  * task or by holding tasklist_lock to prevent it from being unlinked.
 306  */
 307 #define get_task_cred(task)                             \
 308 ({                                                      \
 309         struct cred *__cred;                            \
 310         rcu_read_lock();                                \
 311         __cred = (struct cred *) __task_cred((task));   \
 312         get_cred(__cred);                               \
 313         rcu_read_unlock();                              \
 314         __cred;                                         \
 315 })
 316
 317 /**
 318  * get_current_cred - Get the current task's subjective credentials
 319  *
 320  * Get the subjective credentials of the current task, pinning them so that
 321  * they can't go away.  Accessing the current task's credentials directly is
 322  * not permitted.
 323  */
 324 #define get_current_cred()                              \
 325         (get_cred(current_cred()))
 326
 327 /**
 328  * get_current_user - Get the current task's user_struct
 329  *
 330  * Get the user record of the current task, pinning it so that it can't go
 331  * away.
 332  */
 333 #define get_current_user()                              \
 334 ({                                                      \
 335         struct user_struct *__u;                        \
 336         struct cred *__cred;                            \
 337         __cred = (struct cred *) current_cred();        \
 338         __u = get_uid(__cred->user);                    \
 339         __u;                                            \
 340 })
 341
 342 /**
 343  * get_current_groups - Get the current task's supplementary group list
 344  *
 345  * Get the supplementary group list of the current task, pinning it so that it
 346  * can't go away.
 347  */
 348 #define get_current_groups()                            \
 349 ({                                                      \
 350         struct group_info *__groups;                    \
 351         struct cred *__cred;                            \
 352         __cred = (struct cred *) current_cred();        \
 353         __groups = get_group_info(__cred->group_info);  \
 354         __groups;                                       \
 355 })
 356
 357 #define task_cred_xxx(task, xxx)                        \
 358 ({                                                      \
 359         __typeof__(((struct cred *)NULL)->xxx) ___val;  \
 360         rcu_read_lock();                                \
 361         ___val = __task_cred((task))->xxx;              \
 362         rcu_read_unlock();                              \
 363         ___val;                                         \
 364 })
 365
 366 #define task_uid(task)          (task_cred_xxx((task), uid))
 367 #define task_euid(task)         (task_cred_xxx((task), euid))
 368
 369 #define current_cred_xxx(xxx)                   \
 370 ({                                              \
 371         current->cred->xxx;                     \
 372 })
 373
 374 #define current_uid()           (current_cred_xxx(uid))
 375 #define current_gid()           (current_cred_xxx(gid))
 376 #define current_euid()          (current_cred_xxx(euid))
 377 #define current_egid()          (current_cred_xxx(egid))
 378 #define current_suid()          (current_cred_xxx(suid))
 379 #define current_sgid()          (current_cred_xxx(sgid))
 380 #define current_fsuid()         (current_cred_xxx(fsuid))
 381 #define current_fsgid()         (current_cred_xxx(fsgid))
 382 #define current_cap()           (current_cred_xxx(cap_effective))
 383 #define current_user()          (current_cred_xxx(user))
 384 #define current_user_ns()       (current_cred_xxx(user)->user_ns)
 385 #define current_security()      (current_cred_xxx(security))
 386
 387 #define current_uid_gid(_uid, _gid)             \
 388 do {                                            \
 389         const struct cred *__cred;              \
 390         __cred = current_cred();                \
 391         *(_uid) = __cred->uid;                  \
 392         *(_gid) = __cred->gid;                  \
 393 } while(0)
 394
 395 #define current_euid_egid(_euid, _egid)         \
 396 do {                                            \
 397         const struct cred *__cred;              \
 398         __cred = current_cred();                \
 399         *(_euid) = __cred->euid;                \
 400         *(_egid) = __cred->egid;                \
 401 } while(0)
 402
 403 #define current_fsuid_fsgid(_fsuid, _fsgid)     \
 404 do {                                            \
 405         const struct cred *__cred;              \
 406         __cred = current_cred();                \
 407         *(_fsuid) = __cred->fsuid;              \
 408         *(_fsgid) = __cred->fsgid;              \
 409 } while(0)
 410
 411 #endif /* _LINUX_CRED_H */