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