include/linux/cred.h

   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[];
  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         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 #ifdef CONFIG_MULTIUSER
  57 extern struct group_info *groups_alloc(int);
  58 extern void groups_free(struct group_info *);
  59
  60 extern int in_group_p(kgid_t);
  61 extern int in_egroup_p(kgid_t);
  62 extern int groups_search(const struct group_info *, kgid_t);
  63
  64 extern int set_current_groups(struct group_info *);
  65 extern void set_groups(struct cred *, struct group_info *);
  66 extern bool may_setgroups(void);
  67 extern void groups_sort(struct group_info *);
  68 #else
  69 static inline void groups_free(struct group_info *group_info)
  70 {
  71 }
  72
  73 static inline int in_group_p(kgid_t grp)
  74 {
  75         return 1;
  76 }
  77 static inline int in_egroup_p(kgid_t grp)
  78 {
  79         return 1;
  80 }
  81 static inline int groups_search(const struct group_info *group_info, kgid_t grp)
  82 {
  83         return 1;
  84 }
  85 #endif
  86
  87 /*
  88  * The security context of a task
  89  *
  90  * The parts of the context break down into two categories:
  91  *
  92  *  (1) The objective context of a task.  These parts are used when some other
  93  *      task is attempting to affect this one.
  94  *
  95  *  (2) The subjective context.  These details are used when the task is acting
  96  *      upon another object, be that a file, a task, a key or whatever.
  97  *
  98  * Note that some members of this structure belong to both categories - the
  99  * LSM security pointer for instance.
 100  *
 101  * A task has two security pointers.  task->real_cred points to the objective
 102  * context that defines that task's actual details.  The objective part of this
 103  * context is used whenever that task is acted upon.
 104  *
 105  * task->cred points to the subjective context that defines the details of how
 106  * that task is going to act upon another object.  This may be overridden
 107  * temporarily to point to another security context, but normally points to the
 108  * same context as task->real_cred.
 109  */
 110 struct cred {
 111         atomic_long_t   usage;
 112         kuid_t          uid;            /* real UID of the task */
 113         kgid_t          gid;            /* real GID of the task */
 114         kuid_t          suid;           /* saved UID of the task */
 115         kgid_t          sgid;           /* saved GID of the task */
 116         kuid_t          euid;           /* effective UID of the task */
 117         kgid_t          egid;           /* effective GID of the task */
 118         kuid_t          fsuid;          /* UID for VFS ops */
 119         kgid_t          fsgid;          /* GID for VFS ops */
 120         unsigned        securebits;     /* SUID-less security management */
 121         kernel_cap_t    cap_inheritable; /* caps our children can inherit */
 122         kernel_cap_t    cap_permitted;  /* caps we're permitted */
 123         kernel_cap_t    cap_effective;  /* caps we can actually use */
 124         kernel_cap_t    cap_bset;       /* capability bounding set */
 125         kernel_cap_t    cap_ambient;    /* Ambient capability set */
 126 #ifdef CONFIG_KEYS
 127         unsigned char   jit_keyring;    /* default keyring to attach requested
 128                                          * keys to */
 129         struct key      *session_keyring; /* keyring inherited over fork */
 130         struct key      *process_keyring; /* keyring private to this process */
 131         struct key      *thread_keyring; /* keyring private to this thread */
 132         struct key      *request_key_auth; /* assumed request_key authority */
 133 #endif
 134 #ifdef CONFIG_SECURITY
 135         void            *security;      /* LSM security */
 136 #endif
 137         struct user_struct *user;       /* real user ID subscription */
 138         struct user_namespace *user_ns; /* user_ns the caps and keyrings are relative to. */
 139         struct ucounts *ucounts;
 140         struct group_info *group_info;  /* supplementary groups for euid/fsgid */
 141         /* RCU deletion */
 142         union {
 143                 int non_rcu;                    /* Can we skip RCU deletion? */
 144                 struct rcu_head rcu;            /* RCU deletion hook */
 145         };
 146 } __randomize_layout;
 147
 148 extern void __put_cred(struct cred *);
 149 extern void exit_creds(struct task_struct *);
 150 extern int copy_creds(struct task_struct *, unsigned long);
 151 extern const struct cred *get_task_cred(struct task_struct *);
 152 extern struct cred *cred_alloc_blank(void);
 153 extern struct cred *prepare_creds(void);
 154 extern struct cred *prepare_exec_creds(void);
 155 extern int commit_creds(struct cred *);
 156 extern void abort_creds(struct cred *);
 157 extern const struct cred *override_creds(const struct cred *);
 158 extern void revert_creds(const struct cred *);
 159 extern struct cred *prepare_kernel_cred(struct task_struct *);
 160 extern int set_security_override(struct cred *, u32);
 161 extern int set_security_override_from_ctx(struct cred *, const char *);
 162 extern int set_create_files_as(struct cred *, struct inode *);
 163 extern int cred_fscmp(const struct cred *, const struct cred *);
 164 extern void __init cred_init(void);
 165 extern int set_cred_ucounts(struct cred *);
 166
 167 static inline bool cap_ambient_invariant_ok(const struct cred *cred)
 168 {
 169         return cap_issubset(cred->cap_ambient,
 170                             cap_intersect(cred->cap_permitted,
 171                                           cred->cap_inheritable));
 172 }
 173
 174 /**
 175  * get_new_cred - Get a reference on a new set of credentials
 176  * @cred: The new credentials to reference
 177  *
 178  * Get a reference on the specified set of new credentials.  The caller must
 179  * release the reference.
 180  */
 181 static inline struct cred *get_new_cred(struct cred *cred)
 182 {
 183         atomic_long_inc(&cred->usage);
 184         return cred;
 185 }
 186
 187 /**
 188  * get_cred - Get a reference on a set of credentials
 189  * @cred: The credentials to reference
 190  *
 191  * Get a reference on the specified set of credentials.  The caller must
 192  * release the reference.  If %NULL is passed, it is returned with no action.
 193  *
 194  * This is used to deal with a committed set of credentials.  Although the
 195  * pointer is const, this will temporarily discard the const and increment the
 196  * usage count.  The purpose of this is to attempt to catch at compile time the
 197  * accidental alteration of a set of credentials that should be considered
 198  * immutable.
 199  */
 200 static inline const struct cred *get_cred(const struct cred *cred)
 201 {
 202         struct cred *nonconst_cred = (struct cred *) cred;
 203         if (!cred)
 204                 return cred;
 205         nonconst_cred->non_rcu = 0;
 206         return get_new_cred(nonconst_cred);
 207 }
 208
 209 static inline const struct cred *get_cred_rcu(const struct cred *cred)
 210 {
 211         struct cred *nonconst_cred = (struct cred *) cred;
 212         if (!cred)
 213                 return NULL;
 214         if (!atomic_long_inc_not_zero(&nonconst_cred->usage))
 215                 return NULL;
 216         nonconst_cred->non_rcu = 0;
 217         return cred;
 218 }
 219
 220 /**
 221  * put_cred - Release a reference to a set of credentials
 222  * @cred: The credentials to release
 223  *
 224  * Release a reference to a set of credentials, deleting them when the last ref
 225  * is released.  If %NULL is passed, nothing is done.
 226  *
 227  * This takes a const pointer to a set of credentials because the credentials
 228  * on task_struct are attached by const pointers to prevent accidental
 229  * alteration of otherwise immutable credential sets.
 230  */
 231 static inline void put_cred(const struct cred *_cred)
 232 {
 233         struct cred *cred = (struct cred *) _cred;
 234
 235         if (cred) {
 236                 if (atomic_long_dec_and_test(&(cred)->usage))
 237                         __put_cred(cred);
 238         }
 239 }
 240
 241 /**
 242  * current_cred - Access the current task's subjective credentials
 243  *
 244  * Access the subjective credentials of the current task.  RCU-safe,
 245  * since nobody else can modify it.
 246  */
 247 #define current_cred() \
 248         rcu_dereference_protected(current->cred, 1)
 249
 250 /**
 251  * current_real_cred - Access the current task's objective credentials
 252  *
 253  * Access the objective credentials of the current task.  RCU-safe,
 254  * since nobody else can modify it.
 255  */
 256 #define current_real_cred() \
 257         rcu_dereference_protected(current->real_cred, 1)
 258
 259 /**
 260  * __task_cred - Access a task's objective credentials
 261  * @task: The task to query
 262  *
 263  * Access the objective credentials of a task.  The caller must hold the RCU
 264  * readlock.
 265  *
 266  * The result of this function should not be passed directly to get_cred();
 267  * rather get_task_cred() should be used instead.
 268  */
 269 #define __task_cred(task)       \
 270         rcu_dereference((task)->real_cred)
 271
 272 /**
 273  * get_current_cred - Get the current task's subjective credentials
 274  *
 275  * Get the subjective credentials of the current task, pinning them so that
 276  * they can't go away.  Accessing the current task's credentials directly is
 277  * not permitted.
 278  */
 279 #define get_current_cred()                              \
 280         (get_cred(current_cred()))
 281
 282 /**
 283  * get_current_user - Get the current task's user_struct
 284  *
 285  * Get the user record of the current task, pinning it so that it can't go
 286  * away.
 287  */
 288 #define get_current_user()                              \
 289 ({                                                      \
 290         struct user_struct *__u;                        \
 291         const struct cred *__cred;                      \
 292         __cred = current_cred();                        \
 293         __u = get_uid(__cred->user);                    \
 294         __u;                                            \
 295 })
 296
 297 /**
 298  * get_current_groups - Get the current task's supplementary group list
 299  *
 300  * Get the supplementary group list of the current task, pinning it so that it
 301  * can't go away.
 302  */
 303 #define get_current_groups()                            \
 304 ({                                                      \
 305         struct group_info *__groups;                    \
 306         const struct cred *__cred;                      \
 307         __cred = current_cred();                        \
 308         __groups = get_group_info(__cred->group_info);  \
 309         __groups;                                       \
 310 })
 311
 312 #define task_cred_xxx(task, xxx)                        \
 313 ({                                                      \
 314         __typeof__(((struct cred *)NULL)->xxx) ___val;  \
 315         rcu_read_lock();                                \
 316         ___val = __task_cred((task))->xxx;              \
 317         rcu_read_unlock();                              \
 318         ___val;                                         \
 319 })
 320
 321 #define task_uid(task)          (task_cred_xxx((task), uid))
 322 #define task_euid(task)         (task_cred_xxx((task), euid))
 323 #define task_ucounts(task)      (task_cred_xxx((task), ucounts))
 324
 325 #define current_cred_xxx(xxx)                   \
 326 ({                                              \
 327         current_cred()->xxx;                    \
 328 })
 329
 330 #define current_uid()           (current_cred_xxx(uid))
 331 #define current_gid()           (current_cred_xxx(gid))
 332 #define current_euid()          (current_cred_xxx(euid))
 333 #define current_egid()          (current_cred_xxx(egid))
 334 #define current_suid()          (current_cred_xxx(suid))
 335 #define current_sgid()          (current_cred_xxx(sgid))
 336 #define current_fsuid()         (current_cred_xxx(fsuid))
 337 #define current_fsgid()         (current_cred_xxx(fsgid))
 338 #define current_cap()           (current_cred_xxx(cap_effective))
 339 #define current_user()          (current_cred_xxx(user))
 340 #define current_ucounts()       (current_cred_xxx(ucounts))
 341
 342 extern struct user_namespace init_user_ns;
 343 #ifdef CONFIG_USER_NS
 344 #define current_user_ns()       (current_cred_xxx(user_ns))
 345 #else
 346 static inline struct user_namespace *current_user_ns(void)
 347 {
 348         return &init_user_ns;
 349 }
 350 #endif
 351
 352
 353 #define current_uid_gid(_uid, _gid)             \
 354 do {                                            \
 355         const struct cred *__cred;              \
 356         __cred = current_cred();                \
 357         *(_uid) = __cred->uid;                  \
 358         *(_gid) = __cred->gid;                  \
 359 } while(0)
 360
 361 #define current_euid_egid(_euid, _egid)         \
 362 do {                                            \
 363         const struct cred *__cred;              \
 364         __cred = current_cred();                \
 365         *(_euid) = __cred->euid;                \
 366         *(_egid) = __cred->egid;                \
 367 } while(0)
 368
 369 #define current_fsuid_fsgid(_fsuid, _fsgid)     \
 370 do {                                            \
 371         const struct cred *__cred;              \
 372         __cred = current_cred();                \
 373         *(_fsuid) = __cred->fsuid;              \
 374         *(_fsgid) = __cred->fsgid;              \
 375 } while(0)
 376
 377 #endif /* _LINUX_CRED_H */