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/refcount.h>
  16 #include <linux/uidgid.h>
  17 #include <linux/sched.h>
  18 #include <linux/sched/user.h>
  19
  20 struct cred;
  21 struct inode;
  22
  23 /*
  24  * COW Supplementary groups list
  25  */
  26 struct group_info {
  27         refcount_t      usage;
  28         int             ngroups;
  29         kgid_t          gid[];
  30 } __randomize_layout;
  31
  32 /**
  33  * get_group_info - Get a reference to a group info structure
  34  * @group_info: The group info to reference
  35  *
  36  * This gets a reference to a set of supplementary groups.
  37  *
  38  * If the caller is accessing a task's credentials, they must hold the RCU read
  39  * lock when reading.
  40  */
  41 static inline struct group_info *get_group_info(struct group_info *gi)
  42 {
  43         refcount_inc(&gi->usage);
  44         return gi;
  45 }
  46
  47 /**
  48  * put_group_info - Release a reference to a group info structure
  49  * @group_info: The group info to release
  50  */
  51 #define put_group_info(group_info)                      \
  52 do {                                                    \
  53         if (refcount_dec_and_test(&(group_info)->usage))        \
  54                 groups_free(group_info);                \
  55 } while (0)
  56
  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_long_t   usage;
 113         kuid_t          uid;            /* real UID of the task */
 114         kgid_t          gid;            /* real GID of the task */
 115         kuid_t          suid;           /* saved UID of the task */
 116         kgid_t          sgid;           /* saved GID of the task */
 117         kuid_t          euid;           /* effective UID of the task */
 118         kgid_t          egid;           /* effective GID of the task */
 119         kuid_t          fsuid;          /* UID for VFS ops */
 120         kgid_t          fsgid;          /* GID for VFS ops */
 121         unsigned        securebits;     /* SUID-less security management */
 122         kernel_cap_t    cap_inheritable; /* caps our children can inherit */
 123         kernel_cap_t    cap_permitted;  /* caps we're permitted */
 124         kernel_cap_t    cap_effective;  /* caps we can actually use */
 125         kernel_cap_t    cap_bset;       /* capability bounding set */
 126         kernel_cap_t    cap_ambient;    /* Ambient capability set */
 127 #ifdef CONFIG_KEYS
 128         unsigned char   jit_keyring;    /* default keyring to attach requested
 129                                          * keys to */
 130         struct key      *session_keyring; /* keyring inherited over fork */
 131         struct key      *process_keyring; /* keyring private to this process */
 132         struct key      *thread_keyring; /* keyring private to this thread */
 133         struct key      *request_key_auth; /* assumed request_key authority */
 134 #endif
 135 #ifdef CONFIG_SECURITY
 136         void            *security;      /* LSM security */
 137 #endif
 138         struct user_struct *user;       /* real user ID subscription */
 139         struct user_namespace *user_ns; /* user_ns the caps and keyrings are relative to. */
 140         struct ucounts *ucounts;
 141         struct group_info *group_info;  /* supplementary groups for euid/fsgid */
 142         /* RCU deletion */
 143         union {
 144                 int non_rcu;                    /* Can we skip RCU deletion? */
 145                 struct rcu_head rcu;            /* RCU deletion hook */
 146         };
 147 } __randomize_layout;
 148
 149 extern void __put_cred(struct cred *);
 150 extern void exit_creds(struct task_struct *);
 151 extern int copy_creds(struct task_struct *, unsigned long);
 152 extern const struct cred *get_task_cred(struct task_struct *);
 153 extern struct cred *cred_alloc_blank(void);
 154 extern struct cred *prepare_creds(void);
 155 extern struct cred *prepare_exec_creds(void);
 156 extern int commit_creds(struct cred *);
 157 extern void abort_creds(struct cred *);
 158 extern const struct cred *override_creds(const struct cred *);
 159 extern void revert_creds(const struct cred *);
 160 extern struct cred *prepare_kernel_cred(struct task_struct *);
 161 extern int set_security_override(struct cred *, u32);
 162 extern int set_security_override_from_ctx(struct cred *, const char *);
 163 extern int set_create_files_as(struct cred *, struct inode *);
 164 extern int cred_fscmp(const struct cred *, const struct cred *);
 165 extern void __init cred_init(void);
 166 extern int set_cred_ucounts(struct cred *);
 167
 168 static inline bool cap_ambient_invariant_ok(const struct cred *cred)
 169 {
 170         return cap_issubset(cred->cap_ambient,
 171                             cap_intersect(cred->cap_permitted,
 172                                           cred->cap_inheritable));
 173 }
 174
 175 /*
 176  * Override creds without bumping reference count. Caller must ensure
 177  * reference remains valid or has taken reference. Almost always not the
 178  * interface you want. Use override_creds()/revert_creds() instead.
 179  */
 180 static inline const struct cred *override_creds_light(const struct cred *override_cred)
 181 {
 182         const struct cred *old = current->cred;
 183
 184         rcu_assign_pointer(current->cred, override_cred);
 185         return old;
 186 }
 187
 188 static inline void revert_creds_light(const struct cred *revert_cred)
 189 {
 190         rcu_assign_pointer(current->cred, revert_cred);
 191 }
 192
 193 /**
 194  * get_new_cred_many - Get references on a new set of credentials
 195  * @cred: The new credentials to reference
 196  * @nr: Number of references to acquire
 197  *
 198  * Get references on the specified set of new credentials.  The caller must
 199  * release all acquired references.
 200  */
 201 static inline struct cred *get_new_cred_many(struct cred *cred, int nr)
 202 {
 203         atomic_long_add(nr, &cred->usage);
 204         return cred;
 205 }
 206
 207 /**
 208  * get_new_cred - Get a reference on a new set of credentials
 209  * @cred: The new credentials to reference
 210  *
 211  * Get a reference on the specified set of new credentials.  The caller must
 212  * release the reference.
 213  */
 214 static inline struct cred *get_new_cred(struct cred *cred)
 215 {
 216         return get_new_cred_many(cred, 1);
 217 }
 218
 219 /**
 220  * get_cred_many - Get references on a set of credentials
 221  * @cred: The credentials to reference
 222  * @nr: Number of references to acquire
 223  *
 224  * Get references on the specified set of credentials.  The caller must release
 225  * all acquired reference.  If %NULL is passed, it is returned with no action.
 226  *
 227  * This is used to deal with a committed set of credentials.  Although the
 228  * pointer is const, this will temporarily discard the const and increment the
 229  * usage count.  The purpose of this is to attempt to catch at compile time the
 230  * accidental alteration of a set of credentials that should be considered
 231  * immutable.
 232  */
 233 static inline const struct cred *get_cred_many(const struct cred *cred, int nr)
 234 {
 235         struct cred *nonconst_cred = (struct cred *) cred;
 236         if (!cred)
 237                 return cred;
 238         nonconst_cred->non_rcu = 0;
 239         return get_new_cred_many(nonconst_cred, nr);
 240 }
 241
 242 /*
 243  * get_cred - Get a reference on a set of credentials
 244  * @cred: The credentials to reference
 245  *
 246  * Get a reference on the specified set of credentials.  The caller must
 247  * release the reference.  If %NULL is passed, it is returned with no action.
 248  *
 249  * This is used to deal with a committed set of credentials.
 250  */
 251 static inline const struct cred *get_cred(const struct cred *cred)
 252 {
 253         return get_cred_many(cred, 1);
 254 }
 255
 256 static inline const struct cred *get_cred_rcu(const struct cred *cred)
 257 {
 258         struct cred *nonconst_cred = (struct cred *) cred;
 259         if (!cred)
 260                 return NULL;
 261         if (!atomic_long_inc_not_zero(&nonconst_cred->usage))
 262                 return NULL;
 263         nonconst_cred->non_rcu = 0;
 264         return cred;
 265 }
 266
 267 /**
 268  * put_cred - Release a reference to a set of credentials
 269  * @cred: The credentials to release
 270  * @nr: Number of references to release
 271  *
 272  * Release a reference to a set of credentials, deleting them when the last ref
 273  * is released.  If %NULL is passed, nothing is done.
 274  *
 275  * This takes a const pointer to a set of credentials because the credentials
 276  * on task_struct are attached by const pointers to prevent accidental
 277  * alteration of otherwise immutable credential sets.
 278  */
 279 static inline void put_cred_many(const struct cred *_cred, int nr)
 280 {
 281         struct cred *cred = (struct cred *) _cred;
 282
 283         if (cred) {
 284                 if (atomic_long_sub_and_test(nr, &cred->usage))
 285                         __put_cred(cred);
 286         }
 287 }
 288
 289 /*
 290  * put_cred - Release a reference to a set of credentials
 291  * @cred: The credentials to release
 292  *
 293  * Release a reference to a set of credentials, deleting them when the last ref
 294  * is released.  If %NULL is passed, nothing is done.
 295  */
 296 static inline void put_cred(const struct cred *cred)
 297 {
 298         put_cred_many(cred, 1);
 299 }
 300
 301 /**
 302  * current_cred - Access the current task's subjective credentials
 303  *
 304  * Access the subjective credentials of the current task.  RCU-safe,
 305  * since nobody else can modify it.
 306  */
 307 #define current_cred() \
 308         rcu_dereference_protected(current->cred, 1)
 309
 310 /**
 311  * current_real_cred - Access the current task's objective credentials
 312  *
 313  * Access the objective credentials of the current task.  RCU-safe,
 314  * since nobody else can modify it.
 315  */
 316 #define current_real_cred() \
 317         rcu_dereference_protected(current->real_cred, 1)
 318
 319 /**
 320  * __task_cred - Access a task's objective credentials
 321  * @task: The task to query
 322  *
 323  * Access the objective credentials of a task.  The caller must hold the RCU
 324  * readlock.
 325  *
 326  * The result of this function should not be passed directly to get_cred();
 327  * rather get_task_cred() should be used instead.
 328  */
 329 #define __task_cred(task)       \
 330         rcu_dereference((task)->real_cred)
 331
 332 /**
 333  * get_current_cred - Get the current task's subjective credentials
 334  *
 335  * Get the subjective credentials of the current task, pinning them so that
 336  * they can't go away.  Accessing the current task's credentials directly is
 337  * not permitted.
 338  */
 339 #define get_current_cred()                              \
 340         (get_cred(current_cred()))
 341
 342 /**
 343  * get_current_user - Get the current task's user_struct
 344  *
 345  * Get the user record of the current task, pinning it so that it can't go
 346  * away.
 347  */
 348 #define get_current_user()                              \
 349 ({                                                      \
 350         struct user_struct *__u;                        \
 351         const struct cred *__cred;                      \
 352         __cred = current_cred();                        \
 353         __u = get_uid(__cred->user);                    \
 354         __u;                                            \
 355 })
 356
 357 /**
 358  * get_current_groups - Get the current task's supplementary group list
 359  *
 360  * Get the supplementary group list of the current task, pinning it so that it
 361  * can't go away.
 362  */
 363 #define get_current_groups()                            \
 364 ({                                                      \
 365         struct group_info *__groups;                    \
 366         const struct cred *__cred;                      \
 367         __cred = current_cred();                        \
 368         __groups = get_group_info(__cred->group_info);  \
 369         __groups;                                       \
 370 })
 371
 372 #define task_cred_xxx(task, xxx)                        \
 373 ({                                                      \
 374         __typeof__(((struct cred *)NULL)->xxx) ___val;  \
 375         rcu_read_lock();                                \
 376         ___val = __task_cred((task))->xxx;              \
 377         rcu_read_unlock();                              \
 378         ___val;                                         \
 379 })
 380
 381 #define task_uid(task)          (task_cred_xxx((task), uid))
 382 #define task_euid(task)         (task_cred_xxx((task), euid))
 383 #define task_ucounts(task)      (task_cred_xxx((task), ucounts))
 384
 385 #define current_cred_xxx(xxx)                   \
 386 ({                                              \
 387         current_cred()->xxx;                    \
 388 })
 389
 390 #define current_uid()           (current_cred_xxx(uid))
 391 #define current_gid()           (current_cred_xxx(gid))
 392 #define current_euid()          (current_cred_xxx(euid))
 393 #define current_egid()          (current_cred_xxx(egid))
 394 #define current_suid()          (current_cred_xxx(suid))
 395 #define current_sgid()          (current_cred_xxx(sgid))
 396 #define current_fsuid()         (current_cred_xxx(fsuid))
 397 #define current_fsgid()         (current_cred_xxx(fsgid))
 398 #define current_cap()           (current_cred_xxx(cap_effective))
 399 #define current_user()          (current_cred_xxx(user))
 400 #define current_ucounts()       (current_cred_xxx(ucounts))
 401
 402 extern struct user_namespace init_user_ns;
 403 #ifdef CONFIG_USER_NS
 404 #define current_user_ns()       (current_cred_xxx(user_ns))
 405 #else
 406 static inline struct user_namespace *current_user_ns(void)
 407 {
 408         return &init_user_ns;
 409 }
 410 #endif
 411
 412
 413 #define current_uid_gid(_uid, _gid)             \
 414 do {                                            \
 415         const struct cred *__cred;              \
 416         __cred = current_cred();                \
 417         *(_uid) = __cred->uid;                  \
 418         *(_gid) = __cred->gid;                  \
 419 } while(0)
 420
 421 #define current_euid_egid(_euid, _egid)         \
 422 do {                                            \
 423         const struct cred *__cred;              \
 424         __cred = current_cred();                \
 425         *(_euid) = __cred->euid;                \
 426         *(_egid) = __cred->egid;                \
 427 } while(0)
 428
 429 #define current_fsuid_fsgid(_fsuid, _fsgid)     \
 430 do {                                            \
 431         const struct cred *__cred;              \
 432         __cred = current_cred();                \
 433         *(_fsuid) = __cred->fsuid;              \
 434         *(_fsgid) = __cred->fsgid;              \
 435 } while(0)
 436
 437 #endif /* _LINUX_CRED_H */