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       1                 :            : /* SPDX-License-Identifier: GPL-2.0-or-later */
       2                 :            : /* Credentials management - see Documentation/security/credentials.rst
       3                 :            :  *
       4                 :            :  * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved.
       5                 :            :  * Written by David Howells (dhowells@redhat.com)
       6                 :            :  */
       7                 :            : 
       8                 :            : #ifndef _LINUX_CRED_H
       9                 :            : #define _LINUX_CRED_H
      10                 :            : 
      11                 :            : #include <linux/capability.h>
      12                 :            : #include <linux/init.h>
      13                 :            : #include <linux/key.h>
      14                 :            : #include <linux/atomic.h>
      15                 :            : #include <linux/uidgid.h>
      16                 :            : #include <linux/sched.h>
      17                 :            : #include <linux/sched/user.h>
      18                 :            : 
      19                 :            : struct cred;
      20                 :            : struct inode;
      21                 :            : 
      22                 :            : /*
      23                 :            :  * COW Supplementary groups list
      24                 :            :  */
      25                 :            : struct group_info {
      26                 :            :         atomic_t        usage;
      27                 :            :         int             ngroups;
      28                 :            :         kgid_t          gid[0];
      29                 :            : } __randomize_layout;
      30                 :            : 
      31                 :            : /**
      32                 :            :  * get_group_info - Get a reference to a group info structure
      33                 :            :  * @group_info: The group info to reference
      34                 :            :  *
      35                 :            :  * This gets a reference to a set of supplementary groups.
      36                 :            :  *
      37                 :            :  * If the caller is accessing a task's credentials, they must hold the RCU read
      38                 :            :  * lock when reading.
      39                 :            :  */
      40                 :            : static inline struct group_info *get_group_info(struct group_info *gi)
      41                 :            : {
      42                 :          3 :         atomic_inc(&gi->usage);
      43                 :            :         return gi;
      44                 :            : }
      45                 :            : 
      46                 :            : /**
      47                 :            :  * put_group_info - Release a reference to a group info structure
      48                 :            :  * @group_info: The group info to release
      49                 :            :  */
      50                 :            : #define put_group_info(group_info)                      \
      51                 :            : do {                                                    \
      52                 :            :         if (atomic_dec_and_test(&(group_info)->usage))   \
      53                 :            :                 groups_free(group_info);                \
      54                 :            : } while (0)
      55                 :            : 
      56                 :            : extern struct group_info init_groups;
      57                 :            : #ifdef CONFIG_MULTIUSER
      58                 :            : extern struct group_info *groups_alloc(int);
      59                 :            : extern void groups_free(struct group_info *);
      60                 :            : 
      61                 :            : extern int in_group_p(kgid_t);
      62                 :            : extern int in_egroup_p(kgid_t);
      63                 :            : extern int groups_search(const struct group_info *, kgid_t);
      64                 :            : 
      65                 :            : extern int set_current_groups(struct group_info *);
      66                 :            : extern void set_groups(struct cred *, struct group_info *);
      67                 :            : extern bool may_setgroups(void);
      68                 :            : extern void groups_sort(struct group_info *);
      69                 :            : #else
      70                 :            : static inline void groups_free(struct group_info *group_info)
      71                 :            : {
      72                 :            : }
      73                 :            : 
      74                 :            : static inline int in_group_p(kgid_t grp)
      75                 :            : {
      76                 :            :         return 1;
      77                 :            : }
      78                 :            : static inline int in_egroup_p(kgid_t grp)
      79                 :            : {
      80                 :            :         return 1;
      81                 :            : }
      82                 :            : static inline int groups_search(const struct group_info *group_info, kgid_t grp)
      83                 :            : {
      84                 :            :         return 1;
      85                 :            : }
      86                 :            : #endif
      87                 :            : 
      88                 :            : /*
      89                 :            :  * The security context of a task
      90                 :            :  *
      91                 :            :  * The parts of the context break down into two categories:
      92                 :            :  *
      93                 :            :  *  (1) The objective context of a task.  These parts are used when some other
      94                 :            :  *      task is attempting to affect this one.
      95                 :            :  *
      96                 :            :  *  (2) The subjective context.  These details are used when the task is acting
      97                 :            :  *      upon another object, be that a file, a task, a key or whatever.
      98                 :            :  *
      99                 :            :  * Note that some members of this structure belong to both categories - the
     100                 :            :  * LSM security pointer for instance.
     101                 :            :  *
     102                 :            :  * A task has two security pointers.  task->real_cred points to the objective
     103                 :            :  * context that defines that task's actual details.  The objective part of this
     104                 :            :  * context is used whenever that task is acted upon.
     105                 :            :  *
     106                 :            :  * task->cred points to the subjective context that defines the details of how
     107                 :            :  * that task is going to act upon another object.  This may be overridden
     108                 :            :  * temporarily to point to another security context, but normally points to the
     109                 :            :  * same context as task->real_cred.
     110                 :            :  */
     111                 :            : struct cred {
     112                 :            :         atomic_t        usage;
     113                 :            : #ifdef CONFIG_DEBUG_CREDENTIALS
     114                 :            :         atomic_t        subscribers;    /* number of processes subscribed */
     115                 :            :         void            *put_addr;
     116                 :            :         unsigned        magic;
     117                 :            : #define CRED_MAGIC      0x43736564
     118                 :            : #define CRED_MAGIC_DEAD 0x44656144
     119                 :            : #endif
     120                 :            :         kuid_t          uid;            /* real UID of the task */
     121                 :            :         kgid_t          gid;            /* real GID of the task */
     122                 :            :         kuid_t          suid;           /* saved UID of the task */
     123                 :            :         kgid_t          sgid;           /* saved GID of the task */
     124                 :            :         kuid_t          euid;           /* effective UID of the task */
     125                 :            :         kgid_t          egid;           /* effective GID of the task */
     126                 :            :         kuid_t          fsuid;          /* UID for VFS ops */
     127                 :            :         kgid_t          fsgid;          /* GID for VFS ops */
     128                 :            :         unsigned        securebits;     /* SUID-less security management */
     129                 :            :         kernel_cap_t    cap_inheritable; /* caps our children can inherit */
     130                 :            :         kernel_cap_t    cap_permitted;  /* caps we're permitted */
     131                 :            :         kernel_cap_t    cap_effective;  /* caps we can actually use */
     132                 :            :         kernel_cap_t    cap_bset;       /* capability bounding set */
     133                 :            :         kernel_cap_t    cap_ambient;    /* Ambient capability set */
     134                 :            : #ifdef CONFIG_KEYS
     135                 :            :         unsigned char   jit_keyring;    /* default keyring to attach requested
     136                 :            :                                          * keys to */
     137                 :            :         struct key      *session_keyring; /* keyring inherited over fork */
     138                 :            :         struct key      *process_keyring; /* keyring private to this process */
     139                 :            :         struct key      *thread_keyring; /* keyring private to this thread */
     140                 :            :         struct key      *request_key_auth; /* assumed request_key authority */
     141                 :            : #endif
     142                 :            : #ifdef CONFIG_SECURITY
     143                 :            :         void            *security;      /* subjective LSM security */
     144                 :            : #endif
     145                 :            :         struct user_struct *user;       /* real user ID subscription */
     146                 :            :         struct user_namespace *user_ns; /* user_ns the caps and keyrings are relative to. */
     147                 :            :         struct group_info *group_info;  /* supplementary groups for euid/fsgid */
     148                 :            :         /* RCU deletion */
     149                 :            :         union {
     150                 :            :                 int non_rcu;                    /* Can we skip RCU deletion? */
     151                 :            :                 struct rcu_head rcu;            /* RCU deletion hook */
     152                 :            :         };
     153                 :            : } __randomize_layout;
     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 int cred_fscmp(const struct cred *, const struct cred *);
     172                 :            : extern void __init cred_init(void);
     173                 :            : 
     174                 :            : /*
     175                 :            :  * check for validity of credentials
     176                 :            :  */
     177                 :            : #ifdef CONFIG_DEBUG_CREDENTIALS
     178                 :            : extern void __invalid_creds(const struct cred *, const char *, unsigned);
     179                 :            : extern void __validate_process_creds(struct task_struct *,
     180                 :            :                                      const char *, unsigned);
     181                 :            : 
     182                 :            : extern bool creds_are_invalid(const struct cred *cred);
     183                 :            : 
     184                 :            : static inline void __validate_creds(const struct cred *cred,
     185                 :            :                                     const char *file, unsigned line)
     186                 :            : {
     187                 :            :         if (unlikely(creds_are_invalid(cred)))
     188                 :            :                 __invalid_creds(cred, file, line);
     189                 :            : }
     190                 :            : 
     191                 :            : #define validate_creds(cred)                            \
     192                 :            : do {                                                    \
     193                 :            :         __validate_creds((cred), __FILE__, __LINE__);   \
     194                 :            : } while(0)
     195                 :            : 
     196                 :            : #define validate_process_creds()                                \
     197                 :            : do {                                                            \
     198                 :            :         __validate_process_creds(current, __FILE__, __LINE__);  \
     199                 :            : } while(0)
     200                 :            : 
     201                 :            : extern void validate_creds_for_do_exit(struct task_struct *);
     202                 :            : #else
     203                 :            : static inline void validate_creds(const struct cred *cred)
     204                 :            : {
     205                 :            : }
     206                 :            : static inline void validate_creds_for_do_exit(struct task_struct *tsk)
     207                 :            : {
     208                 :            : }
     209                 :            : static inline void validate_process_creds(void)
     210                 :            : {
     211                 :            : }
     212                 :            : #endif
     213                 :            : 
     214                 :          3 : static inline bool cap_ambient_invariant_ok(const struct cred *cred)
     215                 :            : {
     216                 :          3 :         return cap_issubset(cred->cap_ambient,
     217                 :            :                             cap_intersect(cred->cap_permitted,
     218                 :            :                                           cred->cap_inheritable));
     219                 :            : }
     220                 :            : 
     221                 :            : /**
     222                 :            :  * get_new_cred - Get a reference on a new set of credentials
     223                 :            :  * @cred: The new credentials to reference
     224                 :            :  *
     225                 :            :  * Get a reference on the specified set of new credentials.  The caller must
     226                 :            :  * release the reference.
     227                 :            :  */
     228                 :            : static inline struct cred *get_new_cred(struct cred *cred)
     229                 :            : {
     230                 :          3 :         atomic_inc(&cred->usage);
     231                 :            :         return cred;
     232                 :            : }
     233                 :            : 
     234                 :            : /**
     235                 :            :  * get_cred - Get a reference on a set of credentials
     236                 :            :  * @cred: The credentials to reference
     237                 :            :  *
     238                 :            :  * Get a reference on the specified set of credentials.  The caller must
     239                 :            :  * release the reference.  If %NULL is passed, it is returned with no action.
     240                 :            :  *
     241                 :            :  * This is used to deal with a committed set of credentials.  Although the
     242                 :            :  * pointer is const, this will temporarily discard the const and increment the
     243                 :            :  * usage count.  The purpose of this is to attempt to catch at compile time the
     244                 :            :  * accidental alteration of a set of credentials that should be considered
     245                 :            :  * immutable.
     246                 :            :  */
     247                 :          3 : static inline const struct cred *get_cred(const struct cred *cred)
     248                 :            : {
     249                 :            :         struct cred *nonconst_cred = (struct cred *) cred;
     250                 :          3 :         if (!cred)
     251                 :            :                 return cred;
     252                 :            :         validate_creds(cred);
     253                 :          3 :         nonconst_cred->non_rcu = 0;
     254                 :          3 :         return get_new_cred(nonconst_cred);
     255                 :            : }
     256                 :            : 
     257                 :          3 : static inline const struct cred *get_cred_rcu(const struct cred *cred)
     258                 :            : {
     259                 :            :         struct cred *nonconst_cred = (struct cred *) cred;
     260                 :          3 :         if (!cred)
     261                 :            :                 return NULL;
     262                 :          3 :         if (!atomic_inc_not_zero(&nonconst_cred->usage))
     263                 :            :                 return NULL;
     264                 :            :         validate_creds(cred);
     265                 :          3 :         nonconst_cred->non_rcu = 0;
     266                 :          3 :         return cred;
     267                 :            : }
     268                 :            : 
     269                 :            : /**
     270                 :            :  * put_cred - Release a reference to a set of credentials
     271                 :            :  * @cred: The credentials to release
     272                 :            :  *
     273                 :            :  * Release a reference to a set of credentials, deleting them when the last ref
     274                 :            :  * is released.  If %NULL is passed, nothing is done.
     275                 :            :  *
     276                 :            :  * This takes a const pointer to a set of credentials because the credentials
     277                 :            :  * on task_struct are attached by const pointers to prevent accidental
     278                 :            :  * alteration of otherwise immutable credential sets.
     279                 :            :  */
     280                 :          3 : static inline void put_cred(const struct cred *_cred)
     281                 :            : {
     282                 :            :         struct cred *cred = (struct cred *) _cred;
     283                 :            : 
     284                 :          3 :         if (cred) {
     285                 :            :                 validate_creds(cred);
     286                 :          3 :                 if (atomic_dec_and_test(&(cred)->usage))
     287                 :          3 :                         __put_cred(cred);
     288                 :            :         }
     289                 :          3 : }
     290                 :            : 
     291                 :            : /**
     292                 :            :  * current_cred - Access the current task's subjective credentials
     293                 :            :  *
     294                 :            :  * Access the subjective credentials of the current task.  RCU-safe,
     295                 :            :  * since nobody else can modify it.
     296                 :            :  */
     297                 :            : #define current_cred() \
     298                 :            :         rcu_dereference_protected(current->cred, 1)
     299                 :            : 
     300                 :            : /**
     301                 :            :  * current_real_cred - Access the current task's objective credentials
     302                 :            :  *
     303                 :            :  * Access the objective credentials of the current task.  RCU-safe,
     304                 :            :  * since nobody else can modify it.
     305                 :            :  */
     306                 :            : #define current_real_cred() \
     307                 :            :         rcu_dereference_protected(current->real_cred, 1)
     308                 :            : 
     309                 :            : /**
     310                 :            :  * __task_cred - Access a task's objective credentials
     311                 :            :  * @task: The task to query
     312                 :            :  *
     313                 :            :  * Access the objective credentials of a task.  The caller must hold the RCU
     314                 :            :  * readlock.
     315                 :            :  *
     316                 :            :  * The result of this function should not be passed directly to get_cred();
     317                 :            :  * rather get_task_cred() should be used instead.
     318                 :            :  */
     319                 :            : #define __task_cred(task)       \
     320                 :            :         rcu_dereference((task)->real_cred)
     321                 :            : 
     322                 :            : /**
     323                 :            :  * get_current_cred - Get the current task's subjective credentials
     324                 :            :  *
     325                 :            :  * Get the subjective credentials of the current task, pinning them so that
     326                 :            :  * they can't go away.  Accessing the current task's credentials directly is
     327                 :            :  * not permitted.
     328                 :            :  */
     329                 :            : #define get_current_cred()                              \
     330                 :            :         (get_cred(current_cred()))
     331                 :            : 
     332                 :            : /**
     333                 :            :  * get_current_user - Get the current task's user_struct
     334                 :            :  *
     335                 :            :  * Get the user record of the current task, pinning it so that it can't go
     336                 :            :  * away.
     337                 :            :  */
     338                 :            : #define get_current_user()                              \
     339                 :            : ({                                                      \
     340                 :            :         struct user_struct *__u;                        \
     341                 :            :         const struct cred *__cred;                      \
     342                 :            :         __cred = current_cred();                        \
     343                 :            :         __u = get_uid(__cred->user);                 \
     344                 :            :         __u;                                            \
     345                 :            : })
     346                 :            : 
     347                 :            : /**
     348                 :            :  * get_current_groups - Get the current task's supplementary group list
     349                 :            :  *
     350                 :            :  * Get the supplementary group list of the current task, pinning it so that it
     351                 :            :  * can't go away.
     352                 :            :  */
     353                 :            : #define get_current_groups()                            \
     354                 :            : ({                                                      \
     355                 :            :         struct group_info *__groups;                    \
     356                 :            :         const struct cred *__cred;                      \
     357                 :            :         __cred = current_cred();                        \
     358                 :            :         __groups = get_group_info(__cred->group_info);       \
     359                 :            :         __groups;                                       \
     360                 :            : })
     361                 :            : 
     362                 :            : #define task_cred_xxx(task, xxx)                        \
     363                 :            : ({                                                      \
     364                 :            :         __typeof__(((struct cred *)NULL)->xxx) ___val;       \
     365                 :            :         rcu_read_lock();                                \
     366                 :            :         ___val = __task_cred((task))->xxx;           \
     367                 :            :         rcu_read_unlock();                              \
     368                 :            :         ___val;                                         \
     369                 :            : })
     370                 :            : 
     371                 :            : #define task_uid(task)          (task_cred_xxx((task), uid))
     372                 :            : #define task_euid(task)         (task_cred_xxx((task), euid))
     373                 :            : 
     374                 :            : #define current_cred_xxx(xxx)                   \
     375                 :            : ({                                              \
     376                 :            :         current_cred()->xxx;                 \
     377                 :            : })
     378                 :            : 
     379                 :            : #define current_uid()           (current_cred_xxx(uid))
     380                 :            : #define current_gid()           (current_cred_xxx(gid))
     381                 :            : #define current_euid()          (current_cred_xxx(euid))
     382                 :            : #define current_egid()          (current_cred_xxx(egid))
     383                 :            : #define current_suid()          (current_cred_xxx(suid))
     384                 :            : #define current_sgid()          (current_cred_xxx(sgid))
     385                 :            : #define current_fsuid()         (current_cred_xxx(fsuid))
     386                 :            : #define current_fsgid()         (current_cred_xxx(fsgid))
     387                 :            : #define current_cap()           (current_cred_xxx(cap_effective))
     388                 :            : #define current_user()          (current_cred_xxx(user))
     389                 :            : 
     390                 :            : extern struct user_namespace init_user_ns;
     391                 :            : #ifdef CONFIG_USER_NS
     392                 :            : #define current_user_ns()       (current_cred_xxx(user_ns))
     393                 :            : #else
     394                 :            : static inline struct user_namespace *current_user_ns(void)
     395                 :            : {
     396                 :            :         return &init_user_ns;
     397                 :            : }
     398                 :            : #endif
     399                 :            : 
     400                 :            : 
     401                 :            : #define current_uid_gid(_uid, _gid)             \
     402                 :            : do {                                            \
     403                 :            :         const struct cred *__cred;              \
     404                 :            :         __cred = current_cred();                \
     405                 :            :         *(_uid) = __cred->uid;                       \
     406                 :            :         *(_gid) = __cred->gid;                       \
     407                 :            : } while(0)
     408                 :            : 
     409                 :            : #define current_euid_egid(_euid, _egid)         \
     410                 :            : do {                                            \
     411                 :            :         const struct cred *__cred;              \
     412                 :            :         __cred = current_cred();                \
     413                 :            :         *(_euid) = __cred->euid;             \
     414                 :            :         *(_egid) = __cred->egid;             \
     415                 :            : } while(0)
     416                 :            : 
     417                 :            : #define current_fsuid_fsgid(_fsuid, _fsgid)     \
     418                 :            : do {                                            \
     419                 :            :         const struct cred *__cred;              \
     420                 :            :         __cred = current_cred();                \
     421                 :            :         *(_fsuid) = __cred->fsuid;           \
     422                 :            :         *(_fsgid) = __cred->fsgid;           \
     423                 :            : } while(0)
     424                 :            : 
     425                 :            : #endif /* _LINUX_CRED_H */