include/linux/cred.h

   1 /* Credentials management - see Documentation/security/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 <linux/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 __rcu *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 user_namespace *user_ns; /* cached user->user_ns */
 150         struct group_info *group_info;  /* supplementary groups for euid/fsgid */
 151         struct rcu_head rcu;            /* RCU deletion hook */
 152 };
 153
 154 extern void __put_cred(struct cred *);
 155 extern void exit_creds(struct task_struct *);
 156 extern int copy_creds(struct task_struct *, unsigned long);
 157 extern const struct cred *get_task_cred(struct task_struct *);
 158 extern struct cred *cred_alloc_blank(void);
 159 extern struct cred *prepare_creds(void);
 160 extern struct cred *prepare_exec_creds(void);
 161 extern int commit_creds(struct cred *);
 162 extern void abort_creds(struct cred *);
 163 extern const struct cred *override_creds(const struct cred *);
 164 extern void revert_creds(const struct cred *);
 165 extern struct cred *prepare_kernel_cred(struct task_struct *);
 166 extern int change_create_files_as(struct cred *, struct inode *);
 167 extern int set_security_override(struct cred *, u32);
 168 extern int set_security_override_from_ctx(struct cred *, const char *);
 169 extern int set_create_files_as(struct cred *, struct inode *);
 170 extern void __init cred_init(void);
 171
 172 /*
 173  * check for validity of credentials
 174  */
 175 #ifdef CONFIG_DEBUG_CREDENTIALS
 176 extern void __invalid_creds(const struct cred *, const char *, unsigned);
 177 extern void __validate_process_creds(struct task_struct *,
 178                                      const char *, unsigned);
 179
 180 extern bool creds_are_invalid(const struct cred *cred);
 181
 182 static inline void __validate_creds(const struct cred *cred,
 183                                     const char *file, unsigned line)
 184 {
 185         if (unlikely(creds_are_invalid(cred)))
 186                 __invalid_creds(cred, file, line);
 187 }
 188
 189 #define validate_creds(cred)                            \
 190 do {                                                    \
 191         __validate_creds((cred), __FILE__, __LINE__);   \
 192 } while(0)
 193
 194 #define validate_process_creds()                                \
 195 do {                                                            \
 196         __validate_process_creds(current, __FILE__, __LINE__);  \
 197 } while(0)
 198
 199 extern void validate_creds_for_do_exit(struct task_struct *);
 200 #else
 201 static inline void validate_creds(const struct cred *cred)
 202 {
 203 }
 204 static inline void validate_creds_for_do_exit(struct task_struct *tsk)
 205 {
 206 }
 207 static inline void validate_process_creds(void)
 208 {
 209 }
 210 #endif
 211
 212 /**
 213  * get_new_cred - Get a reference on a new set of credentials
 214  * @cred: The new credentials to reference
 215  *
 216  * Get a reference on the specified set of new credentials.  The caller must
 217  * release the reference.
 218  */
 219 static inline struct cred *get_new_cred(struct cred *cred)
 220 {
 221         atomic_inc(&cred->usage);
 222         return cred;
 223 }
 224
 225 /**
 226  * get_cred - Get a reference on a set of credentials
 227  * @cred: The credentials to reference
 228  *
 229  * Get a reference on the specified set of credentials.  The caller must
 230  * release the reference.
 231  *
 232  * This is used to deal with a committed set of credentials.  Although the
 233  * pointer is const, this will temporarily discard the const and increment the
 234  * usage count.  The purpose of this is to attempt to catch at compile time the
 235  * accidental alteration of a set of credentials that should be considered
 236  * immutable.
 237  */
 238 static inline const struct cred *get_cred(const struct cred *cred)
 239 {
 240         struct cred *nonconst_cred = (struct cred *) cred;
 241         validate_creds(cred);
 242         return get_new_cred(nonconst_cred);
 243 }
 244
 245 /**
 246  * put_cred - Release a reference to a set of credentials
 247  * @cred: The credentials to release
 248  *
 249  * Release a reference to a set of credentials, deleting them when the last ref
 250  * is released.
 251  *
 252  * This takes a const pointer to a set of credentials because the credentials
 253  * on task_struct are attached by const pointers to prevent accidental
 254  * alteration of otherwise immutable credential sets.
 255  */
 256 static inline void put_cred(const struct cred *_cred)
 257 {
 258         struct cred *cred = (struct cred *) _cred;
 259
 260         validate_creds(cred);
 261         if (atomic_dec_and_test(&(cred)->usage))
 262                 __put_cred(cred);
 263 }
 264
 265 /**
 266  * current_cred - Access the current task's subjective credentials
 267  *
 268  * Access the subjective credentials of the current task.  RCU-safe,
 269  * since nobody else can modify it.
 270  */
 271 #define current_cred() \
 272         rcu_dereference_protected(current->cred, 1)
 273
 274 /**
 275  * __task_cred - Access a task's objective credentials
 276  * @task: The task to query
 277  *
 278  * Access the objective credentials of a task.  The caller must hold the RCU
 279  * readlock or the task must be dead and unable to change its own credentials.
 280  *
 281  * The result of this function should not be passed directly to get_cred();
 282  * rather get_task_cred() should be used instead.
 283  */
 284 #define __task_cred(task)                                               \
 285         ({                                                              \
 286                 const struct task_struct *__t = (task);                 \
 287                 rcu_dereference_check(__t->real_cred,                   \
 288                                       task_is_dead(__t));               \
 289         })
 290
 291 /**
 292  * get_current_cred - Get the current task's subjective credentials
 293  *
 294  * Get the subjective credentials of the current task, pinning them so that
 295  * they can't go away.  Accessing the current task's credentials directly is
 296  * not permitted.
 297  */
 298 #define get_current_cred()                              \
 299         (get_cred(current_cred()))
 300
 301 /**
 302  * get_current_user - Get the current task's user_struct
 303  *
 304  * Get the user record of the current task, pinning it so that it can't go
 305  * away.
 306  */
 307 #define get_current_user()                              \
 308 ({                                                      \
 309         struct user_struct *__u;                        \
 310         const struct cred *__cred;                      \
 311         __cred = current_cred();                        \
 312         __u = get_uid(__cred->user);                    \
 313         __u;                                            \
 314 })
 315
 316 /**
 317  * get_current_groups - Get the current task's supplementary group list
 318  *
 319  * Get the supplementary group list of the current task, pinning it so that it
 320  * can't go away.
 321  */
 322 #define get_current_groups()                            \
 323 ({                                                      \
 324         struct group_info *__groups;                    \
 325         const struct cred *__cred;                      \
 326         __cred = current_cred();                        \
 327         __groups = get_group_info(__cred->group_info);  \
 328         __groups;                                       \
 329 })
 330
 331 #define task_cred_xxx(task, xxx)                        \
 332 ({                                                      \
 333         __typeof__(((struct cred *)NULL)->xxx) ___val;  \
 334         rcu_read_lock();                                \
 335         ___val = __task_cred((task))->xxx;              \
 336         rcu_read_unlock();                              \
 337         ___val;                                         \
 338 })
 339
 340 #define task_uid(task)          (task_cred_xxx((task), uid))
 341 #define task_euid(task)         (task_cred_xxx((task), euid))
 342
 343 #define current_cred_xxx(xxx)                   \
 344 ({                                              \
 345         current_cred()->xxx;                    \
 346 })
 347
 348 #define current_uid()           (current_cred_xxx(uid))
 349 #define current_gid()           (current_cred_xxx(gid))
 350 #define current_euid()          (current_cred_xxx(euid))
 351 #define current_egid()          (current_cred_xxx(egid))
 352 #define current_suid()          (current_cred_xxx(suid))
 353 #define current_sgid()          (current_cred_xxx(sgid))
 354 #define current_fsuid()         (current_cred_xxx(fsuid))
 355 #define current_fsgid()         (current_cred_xxx(fsgid))
 356 #define current_cap()           (current_cred_xxx(cap_effective))
 357 #define current_user()          (current_cred_xxx(user))
 358 #define current_security()      (current_cred_xxx(security))
 359
 360 #ifdef CONFIG_USER_NS
 361 #define current_user_ns() (current_cred_xxx(user_ns))
 362 #else
 363 extern struct user_namespace init_user_ns;
 364 #define current_user_ns() (&init_user_ns)
 365 #endif
 366
 367
 368 #define current_uid_gid(_uid, _gid)             \
 369 do {                                            \
 370         const struct cred *__cred;              \
 371         __cred = current_cred();                \
 372         *(_uid) = __cred->uid;                  \
 373         *(_gid) = __cred->gid;                  \
 374 } while(0)
 375
 376 #define current_euid_egid(_euid, _egid)         \
 377 do {                                            \
 378         const struct cred *__cred;              \
 379         __cred = current_cred();                \
 380         *(_euid) = __cred->euid;                \
 381         *(_egid) = __cred->egid;                \
 382 } while(0)
 383
 384 #define current_fsuid_fsgid(_fsuid, _fsgid)     \
 385 do {                                            \
 386         const struct cred *__cred;              \
 387         __cred = current_cred();                \
 388         *(_fsuid) = __cred->fsuid;              \
 389         *(_fsgid) = __cred->fsgid;              \
 390 } while(0)
 391
 392 #endif /* _LINUX_CRED_H */