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 <linux/selinux.h>
  19 #include <asm/atomic.h>
  20
  21 struct user_struct;
  22 struct cred;
  23 struct inode;
  24
  25 /*
  26  * COW Supplementary groups list
  27  */
  28 #define NGROUPS_SMALL           32
  29 #define NGROUPS_PER_BLOCK       ((unsigned int)(PAGE_SIZE / sizeof(gid_t)))
  30
  31 struct group_info {
  32         atomic_t        usage;
  33         int             ngroups;
  34         int             nblocks;
  35         gid_t           small_block[NGROUPS_SMALL];
  36         gid_t           *blocks[0];
  37 };
  38
  39 /**
  40  * get_group_info - Get a reference to a group info structure
  41  * @group_info: The group info to reference
  42  *
  43  * This gets a reference to a set of supplementary groups.
  44  *
  45  * If the caller is accessing a task's credentials, they must hold the RCU read
  46  * lock when reading.
  47  */
  48 static inline struct group_info *get_group_info(struct group_info *gi)
  49 {
  50         atomic_inc(&gi->usage);
  51         return gi;
  52 }
  53
  54 /**
  55  * put_group_info - Release a reference to a group info structure
  56  * @group_info: The group info to release
  57  */
  58 #define put_group_info(group_info)                      \
  59 do {                                                    \
  60         if (atomic_dec_and_test(&(group_info)->usage))  \
  61                 groups_free(group_info);                \
  62 } while (0)
  63
  64 extern struct group_info *groups_alloc(int);
  65 extern struct group_info init_groups;
  66 extern void groups_free(struct group_info *);
  67 extern int set_current_groups(struct group_info *);
  68 extern int set_groups(struct cred *, struct group_info *);
  69 extern int groups_search(const struct group_info *, gid_t);
  70
  71 /* access the groups "array" with this macro */
  72 #define GROUP_AT(gi, i) \
  73         ((gi)->blocks[(i) / NGROUPS_PER_BLOCK][(i) % NGROUPS_PER_BLOCK])
  74
  75 extern int in_group_p(gid_t);
  76 extern int in_egroup_p(gid_t);
  77
  78 /*
  79  * The common credentials for a thread group
  80  * - shared by CLONE_THREAD
  81  */
  82 #ifdef CONFIG_KEYS
  83 struct thread_group_cred {
  84         atomic_t        usage;
  85         pid_t           tgid;                   /* thread group process ID */
  86         spinlock_t      lock;
  87         struct key      *session_keyring;       /* keyring inherited over fork */
  88         struct key      *process_keyring;       /* keyring private to this process */
  89         struct rcu_head rcu;                    /* RCU deletion hook */
  90 };
  91 #endif
  92
  93 /*
  94  * The security context of a task
  95  *
  96  * The parts of the context break down into two categories:
  97  *
  98  *  (1) The objective context of a task.  These parts are used when some other
  99  *      task is attempting to affect this one.
 100  *
 101  *  (2) The subjective context.  These details are used when the task is acting
 102  *      upon another object, be that a file, a task, a key or whatever.
 103  *
 104  * Note that some members of this structure belong to both categories - the
 105  * LSM security pointer for instance.
 106  *
 107  * A task has two security pointers.  task->real_cred points to the objective
 108  * context that defines that task's actual details.  The objective part of this
 109  * context is used whenever that task is acted upon.
 110  *
 111  * task->cred points to the subjective context that defines the details of how
 112  * that task is going to act upon another object.  This may be overridden
 113  * temporarily to point to another security context, but normally points to the
 114  * same context as task->real_cred.
 115  */
 116 struct cred {
 117         atomic_t        usage;
 118 #ifdef CONFIG_DEBUG_CREDENTIALS
 119         atomic_t        subscribers;    /* number of processes subscribed */
 120         void            *put_addr;
 121         unsigned        magic;
 122 #define CRED_MAGIC      0x43736564
 123 #define CRED_MAGIC_DEAD 0x44656144
 124 #endif
 125         uid_t           uid;            /* real UID of the task */
 126         gid_t           gid;            /* real GID of the task */
 127         uid_t           suid;           /* saved UID of the task */
 128         gid_t           sgid;           /* saved GID of the task */
 129         uid_t           euid;           /* effective UID of the task */
 130         gid_t           egid;           /* effective GID of the task */
 131         uid_t           fsuid;          /* UID for VFS ops */
 132         gid_t           fsgid;          /* GID for VFS ops */
 133         unsigned        securebits;     /* SUID-less security management */
 134         kernel_cap_t    cap_inheritable; /* caps our children can inherit */
 135         kernel_cap_t    cap_permitted;  /* caps we're permitted */
 136         kernel_cap_t    cap_effective;  /* caps we can actually use */
 137         kernel_cap_t    cap_bset;       /* capability bounding set */
 138 #ifdef CONFIG_KEYS
 139         unsigned char   jit_keyring;    /* default keyring to attach requested
 140                                          * keys to */
 141         struct key      *thread_keyring; /* keyring private to this thread */
 142         struct key      *request_key_auth; /* assumed request_key authority */
 143         struct thread_group_cred *tgcred; /* thread-group shared credentials */
 144 #endif
 145 #ifdef CONFIG_SECURITY
 146         void            *security;      /* subjective LSM security */
 147 #endif
 148         struct user_struct *user;       /* real user ID subscription */
 149         struct group_info *group_info;  /* supplementary groups for euid/fsgid */
 150         struct rcu_head rcu;            /* RCU deletion hook */
 151 };
 152
 153 extern void __put_cred(struct cred *);
 154 extern void exit_creds(struct task_struct *);
 155 extern int copy_creds(struct task_struct *, unsigned long);
 156 extern struct cred *cred_alloc_blank(void);
 157 extern struct cred *prepare_creds(void);
 158 extern struct cred *prepare_exec_creds(void);
 159 extern struct cred *prepare_usermodehelper_creds(void);
 160 extern int commit_creds(struct cred *);
 161 extern void abort_creds(struct cred *);
 162 extern const struct cred *override_creds(const struct cred *);
 163 extern void revert_creds(const struct cred *);
 164 extern struct cred *prepare_kernel_cred(struct task_struct *);
 165 extern int change_create_files_as(struct cred *, struct inode *);
 166 extern int set_security_override(struct cred *, u32);
 167 extern int set_security_override_from_ctx(struct cred *, const char *);
 168 extern int set_create_files_as(struct cred *, struct inode *);
 169 extern void __init cred_init(void);
 170
 171 /*
 172  * check for validity of credentials
 173  */
 174 #ifdef CONFIG_DEBUG_CREDENTIALS
 175 extern void __invalid_creds(const struct cred *, const char *, unsigned);
 176 extern void __validate_process_creds(struct task_struct *,
 177                                      const char *, unsigned);
 178
 179 static inline bool creds_are_invalid(const struct cred *cred)
 180 {
 181         if (cred->magic != CRED_MAGIC)
 182                 return true;
 183         if (atomic_read(&cred->usage) < atomic_read(&cred->subscribers))
 184                 return true;
 185 #ifdef CONFIG_SECURITY_SELINUX
 186         if (selinux_is_enabled()) {
 187                 if ((unsigned long) cred->security < PAGE_SIZE)
 188                         return true;
 189                 if ((*(u32 *)cred->security & 0xffffff00) ==
 190                     (POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8))
 191                         return true;
 192         }
 193 #endif
 194         return false;
 195 }
 196
 197 static inline void __validate_creds(const struct cred *cred,
 198                                     const char *file, unsigned line)
 199 {
 200         if (unlikely(creds_are_invalid(cred)))
 201                 __invalid_creds(cred, file, line);
 202 }
 203
 204 #define validate_creds(cred)                            \
 205 do {                                                    \
 206         __validate_creds((cred), __FILE__, __LINE__);   \
 207 } while(0)
 208
 209 #define validate_process_creds()                                \
 210 do {                                                            \
 211         __validate_process_creds(current, __FILE__, __LINE__);  \
 212 } while(0)
 213
 214 extern void validate_creds_for_do_exit(struct task_struct *);
 215 #else
 216 static inline void validate_creds(const struct cred *cred)
 217 {
 218 }
 219 static inline void validate_creds_for_do_exit(struct task_struct *tsk)
 220 {
 221 }
 222 static inline void validate_process_creds(void)
 223 {
 224 }
 225 #endif
 226
 227 /**
 228  * get_new_cred - Get a reference on a new set of credentials
 229  * @cred: The new credentials to reference
 230  *
 231  * Get a reference on the specified set of new credentials.  The caller must
 232  * release the reference.
 233  */
 234 static inline struct cred *get_new_cred(struct cred *cred)
 235 {
 236         atomic_inc(&cred->usage);
 237         return cred;
 238 }
 239
 240 /**
 241  * get_cred - Get a reference on a set of credentials
 242  * @cred: The credentials to reference
 243  *
 244  * Get a reference on the specified set of credentials.  The caller must
 245  * release the reference.
 246  *
 247  * This is used to deal with a committed set of credentials.  Although the
 248  * pointer is const, this will temporarily discard the const and increment the
 249  * usage count.  The purpose of this is to attempt to catch at compile time the
 250  * accidental alteration of a set of credentials that should be considered
 251  * immutable.
 252  */
 253 static inline const struct cred *get_cred(const struct cred *cred)
 254 {
 255         struct cred *nonconst_cred = (struct cred *) cred;
 256         validate_creds(cred);
 257         return get_new_cred(nonconst_cred);
 258 }
 259
 260 /**
 261  * put_cred - Release a reference to a set of credentials
 262  * @cred: The credentials to release
 263  *
 264  * Release a reference to a set of credentials, deleting them when the last ref
 265  * is released.
 266  *
 267  * This takes a const pointer to a set of credentials because the credentials
 268  * on task_struct are attached by const pointers to prevent accidental
 269  * alteration of otherwise immutable credential sets.
 270  */
 271 static inline void put_cred(const struct cred *_cred)
 272 {
 273         struct cred *cred = (struct cred *) _cred;
 274
 275         validate_creds(cred);
 276         if (atomic_dec_and_test(&(cred)->usage))
 277                 __put_cred(cred);
 278 }
 279
 280 /**
 281  * current_cred - Access the current task's subjective credentials
 282  *
 283  * Access the subjective credentials of the current task.
 284  */
 285 #define current_cred() \
 286         (current->cred)
 287
 288 /**
 289  * __task_cred - Access a task's objective credentials
 290  * @task: The task to query
 291  *
 292  * Access the objective credentials of a task.  The caller must hold the RCU
 293  * readlock.
 294  *
 295  * The caller must make sure task doesn't go away, either by holding a ref on
 296  * task or by holding tasklist_lock to prevent it from being unlinked.
 297  */
 298 #define __task_cred(task) \
 299         ((const struct cred *)(rcu_dereference((task)->real_cred)))
 300
 301 /**
 302  * get_task_cred - Get another task's objective credentials
 303  * @task: The task to query
 304  *
 305  * Get the objective credentials of a task, pinning them so that they can't go
 306  * away.  Accessing a task's credentials directly is not permitted.
 307  *
 308  * The caller must make sure task doesn't go away, either by holding a ref on
 309  * task or by holding tasklist_lock to prevent it from being unlinked.
 310  */
 311 #define get_task_cred(task)                             \
 312 ({                                                      \
 313         struct cred *__cred;                            \
 314         rcu_read_lock();                                \
 315         __cred = (struct cred *) __task_cred((task));   \
 316         get_cred(__cred);                               \
 317         rcu_read_unlock();                              \
 318         __cred;                                         \
 319 })
 320
 321 /**
 322  * get_current_cred - Get the current task's subjective credentials
 323  *
 324  * Get the subjective credentials of the current task, pinning them so that
 325  * they can't go away.  Accessing the current task's credentials directly is
 326  * not permitted.
 327  */
 328 #define get_current_cred()                              \
 329         (get_cred(current_cred()))
 330
 331 /**
 332  * get_current_user - Get the current task's user_struct
 333  *
 334  * Get the user record of the current task, pinning it so that it can't go
 335  * away.
 336  */
 337 #define get_current_user()                              \
 338 ({                                                      \
 339         struct user_struct *__u;                        \
 340         struct cred *__cred;                            \
 341         __cred = (struct cred *) current_cred();        \
 342         __u = get_uid(__cred->user);                    \
 343         __u;                                            \
 344 })
 345
 346 /**
 347  * get_current_groups - Get the current task's supplementary group list
 348  *
 349  * Get the supplementary group list of the current task, pinning it so that it
 350  * can't go away.
 351  */
 352 #define get_current_groups()                            \
 353 ({                                                      \
 354         struct group_info *__groups;                    \
 355         struct cred *__cred;                            \
 356         __cred = (struct cred *) current_cred();        \
 357         __groups = get_group_info(__cred->group_info);  \
 358         __groups;                                       \
 359 })
 360
 361 #define task_cred_xxx(task, xxx)                        \
 362 ({                                                      \
 363         __typeof__(((struct cred *)NULL)->xxx) ___val;  \
 364         rcu_read_lock();                                \
 365         ___val = __task_cred((task))->xxx;              \
 366         rcu_read_unlock();                              \
 367         ___val;                                         \
 368 })
 369
 370 #define task_uid(task)          (task_cred_xxx((task), uid))
 371 #define task_euid(task)         (task_cred_xxx((task), euid))
 372
 373 #define current_cred_xxx(xxx)                   \
 374 ({                                              \
 375         current->cred->xxx;                     \
 376 })
 377
 378 #define current_uid()           (current_cred_xxx(uid))
 379 #define current_gid()           (current_cred_xxx(gid))
 380 #define current_euid()          (current_cred_xxx(euid))
 381 #define current_egid()          (current_cred_xxx(egid))
 382 #define current_suid()          (current_cred_xxx(suid))
 383 #define current_sgid()          (current_cred_xxx(sgid))
 384 #define current_fsuid()         (current_cred_xxx(fsuid))
 385 #define current_fsgid()         (current_cred_xxx(fsgid))
 386 #define current_cap()           (current_cred_xxx(cap_effective))
 387 #define current_user()          (current_cred_xxx(user))
 388 #define current_user_ns()       (current_cred_xxx(user)->user_ns)
 389 #define current_security()      (current_cred_xxx(security))
 390
 391 #define current_uid_gid(_uid, _gid)             \
 392 do {                                            \
 393         const struct cred *__cred;              \
 394         __cred = current_cred();                \
 395         *(_uid) = __cred->uid;                  \
 396         *(_gid) = __cred->gid;                  \
 397 } while(0)
 398
 399 #define current_euid_egid(_euid, _egid)         \
 400 do {                                            \
 401         const struct cred *__cred;              \
 402         __cred = current_cred();                \
 403         *(_euid) = __cred->euid;                \
 404         *(_egid) = __cred->egid;                \
 405 } while(0)
 406
 407 #define current_fsuid_fsgid(_fsuid, _fsgid)     \
 408 do {                                            \
 409         const struct cred *__cred;              \
 410         __cred = current_cred();                \
 411         *(_fsuid) = __cred->fsuid;              \
 412         *(_fsgid) = __cred->fsgid;              \
 413 } while(0)
 414
 415 #endif /* _LINUX_CRED_H */