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 ([email protected])
   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_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;      /* 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 ucounts *ucounts;
 148         struct group_info *group_info;  /* supplementary groups for euid/fsgid */
 149         /* RCU deletion */
 150         union {
 151                 int non_rcu;                    /* Can we skip RCU deletion? */
 152                 struct rcu_head rcu;            /* RCU deletion hook */
 153         };
 154 } __randomize_layout;
 155
 156 extern void __put_cred(struct cred *);
 157 extern void exit_creds(struct task_struct *);
 158 extern int copy_creds(struct task_struct *, unsigned long);
 159 extern const struct cred *get_task_cred(struct task_struct *);
 160 extern struct cred *cred_alloc_blank(void);
 161 extern struct cred *prepare_creds(void);
 162 extern struct cred *prepare_exec_creds(void);
 163 extern int commit_creds(struct cred *);
 164 extern void abort_creds(struct cred *);
 165 extern const struct cred *override_creds(const struct cred *);
 166 extern void revert_creds(const struct cred *);
 167 extern struct cred *prepare_kernel_cred(struct task_struct *);
 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 extern int set_cred_ucounts(struct cred *);
 174
 175 /*
 176  * check for validity of credentials
 177  */
 178 #ifdef CONFIG_DEBUG_CREDENTIALS
 179 extern void __noreturn __invalid_creds(const struct cred *, const char *, unsigned);
 180 extern void __validate_process_creds(struct task_struct *,
 181                                      const char *, unsigned);
 182
 183 extern bool creds_are_invalid(const struct cred *cred);
 184
 185 static inline void __validate_creds(const struct cred *cred,
 186                                     const char *file, unsigned line)
 187 {
 188         if (unlikely(creds_are_invalid(cred)))
 189                 __invalid_creds(cred, file, line);
 190 }
 191
 192 #define validate_creds(cred)                            \
 193 do {                                                    \
 194         __validate_creds((cred), __FILE__, __LINE__);   \
 195 } while(0)
 196
 197 #define validate_process_creds()                                \
 198 do {                                                            \
 199         __validate_process_creds(current, __FILE__, __LINE__);  \
 200 } while(0)
 201
 202 extern void validate_creds_for_do_exit(struct task_struct *);
 203 #else
 204 static inline void validate_creds(const struct cred *cred)
 205 {
 206 }
 207 static inline void validate_creds_for_do_exit(struct task_struct *tsk)
 208 {
 209 }
 210 static inline void validate_process_creds(void)
 211 {
 212 }
 213 #endif
 214
 215 static inline bool cap_ambient_invariant_ok(const struct cred *cred)
 216 {
 217         return cap_issubset(cred->cap_ambient,
 218                             cap_intersect(cred->cap_permitted,
 219                                           cred->cap_inheritable));
 220 }
 221
 222 /**
 223  * get_new_cred_many - Get references on a new set of credentials
 224  * @cred: The new credentials to reference
 225  * @nr: Number of references to acquire
 226  *
 227  * Get references on the specified set of new credentials.  The caller must
 228  * release all acquired references.
 229  */
 230 static inline struct cred *get_new_cred_many(struct cred *cred, int nr)
 231 {
 232         atomic_add(nr, &cred->usage);
 233         return cred;
 234 }
 235
 236 /**
 237  * get_new_cred - Get a reference on a new set of credentials
 238  * @cred: The new credentials to reference
 239  *
 240  * Get a reference on the specified set of new credentials.  The caller must
 241  * release the reference.
 242  */
 243 static inline struct cred *get_new_cred(struct cred *cred)
 244 {
 245         return get_new_cred_many(cred, 1);
 246 }
 247
 248 /**
 249  * get_cred_many - Get references on a set of credentials
 250  * @cred: The credentials to reference
 251  * @nr: Number of references to acquire
 252  *
 253  * Get references on the specified set of credentials.  The caller must release
 254  * all acquired reference.  If %NULL is passed, it is returned with no action.
 255  *
 256  * This is used to deal with a committed set of credentials.  Although the
 257  * pointer is const, this will temporarily discard the const and increment the
 258  * usage count.  The purpose of this is to attempt to catch at compile time the
 259  * accidental alteration of a set of credentials that should be considered
 260  * immutable.
 261  */
 262 static inline const struct cred *get_cred_many(const struct cred *cred, int nr)
 263 {
 264         struct cred *nonconst_cred = (struct cred *) cred;
 265         if (!cred)
 266                 return cred;
 267         validate_creds(cred);
 268         nonconst_cred->non_rcu = 0;
 269         return get_new_cred_many(nonconst_cred, nr);
 270 }
 271
 272 /*
 273  * get_cred - Get a reference on a set of credentials
 274  * @cred: The credentials to reference
 275  *
 276  * Get a reference on the specified set of credentials.  The caller must
 277  * release the reference.  If %NULL is passed, it is returned with no action.
 278  *
 279  * This is used to deal with a committed set of credentials.
 280  */
 281 static inline const struct cred *get_cred(const struct cred *cred)
 282 {
 283         return get_cred_many(cred, 1);
 284 }
 285
 286 static inline const struct cred *get_cred_rcu(const struct cred *cred)
 287 {
 288         struct cred *nonconst_cred = (struct cred *) cred;
 289         if (!cred)
 290                 return NULL;
 291         if (!atomic_inc_not_zero(&nonconst_cred->usage))
 292                 return NULL;
 293         validate_creds(cred);
 294         nonconst_cred->non_rcu = 0;
 295         return cred;
 296 }
 297
 298 /**
 299  * put_cred - Release a reference to a set of credentials
 300  * @cred: The credentials to release
 301  * @nr: Number of references to release
 302  *
 303  * Release a reference to a set of credentials, deleting them when the last ref
 304  * is released.  If %NULL is passed, nothing is done.
 305  *
 306  * This takes a const pointer to a set of credentials because the credentials
 307  * on task_struct are attached by const pointers to prevent accidental
 308  * alteration of otherwise immutable credential sets.
 309  */
 310 static inline void put_cred_many(const struct cred *_cred, int nr)
 311 {
 312         struct cred *cred = (struct cred *) _cred;
 313
 314         if (cred) {
 315                 validate_creds(cred);
 316                 if (atomic_sub_and_test(nr, &cred->usage))
 317                         __put_cred(cred);
 318         }
 319 }
 320
 321 /*
 322  * put_cred - Release a reference to a set of credentials
 323  * @cred: The credentials to release
 324  *
 325  * Release a reference to a set of credentials, deleting them when the last ref
 326  * is released.  If %NULL is passed, nothing is done.
 327  */
 328 static inline void put_cred(const struct cred *cred)
 329 {
 330         put_cred_many(cred, 1);
 331 }
 332
 333 /**
 334  * current_cred - Access the current task's subjective credentials
 335  *
 336  * Access the subjective credentials of the current task.  RCU-safe,
 337  * since nobody else can modify it.
 338  */
 339 #define current_cred() \
 340         rcu_dereference_protected(current->cred, 1)
 341
 342 /**
 343  * current_real_cred - Access the current task's objective credentials
 344  *
 345  * Access the objective credentials of the current task.  RCU-safe,
 346  * since nobody else can modify it.
 347  */
 348 #define current_real_cred() \
 349         rcu_dereference_protected(current->real_cred, 1)
 350
 351 /**
 352  * __task_cred - Access a task's objective credentials
 353  * @task: The task to query
 354  *
 355  * Access the objective credentials of a task.  The caller must hold the RCU
 356  * readlock.
 357  *
 358  * The result of this function should not be passed directly to get_cred();
 359  * rather get_task_cred() should be used instead.
 360  */
 361 #define __task_cred(task)       \
 362         rcu_dereference((task)->real_cred)
 363
 364 /**
 365  * get_current_cred - Get the current task's subjective credentials
 366  *
 367  * Get the subjective credentials of the current task, pinning them so that
 368  * they can't go away.  Accessing the current task's credentials directly is
 369  * not permitted.
 370  */
 371 #define get_current_cred()                              \
 372         (get_cred(current_cred()))
 373
 374 /**
 375  * get_current_user - Get the current task's user_struct
 376  *
 377  * Get the user record of the current task, pinning it so that it can't go
 378  * away.
 379  */
 380 #define get_current_user()                              \
 381 ({                                                      \
 382         struct user_struct *__u;                        \
 383         const struct cred *__cred;                      \
 384         __cred = current_cred();                        \
 385         __u = get_uid(__cred->user);                    \
 386         __u;                                            \
 387 })
 388
 389 /**
 390  * get_current_groups - Get the current task's supplementary group list
 391  *
 392  * Get the supplementary group list of the current task, pinning it so that it
 393  * can't go away.
 394  */
 395 #define get_current_groups()                            \
 396 ({                                                      \
 397         struct group_info *__groups;                    \
 398         const struct cred *__cred;                      \
 399         __cred = current_cred();                        \
 400         __groups = get_group_info(__cred->group_info);  \
 401         __groups;                                       \
 402 })
 403
 404 #define task_cred_xxx(task, xxx)                        \
 405 ({                                                      \
 406         __typeof__(((struct cred *)NULL)->xxx) ___val;  \
 407         rcu_read_lock();                                \
 408         ___val = __task_cred((task))->xxx;              \
 409         rcu_read_unlock();                              \
 410         ___val;                                         \
 411 })
 412
 413 #define task_uid(task)          (task_cred_xxx((task), uid))
 414 #define task_euid(task)         (task_cred_xxx((task), euid))
 415 #define task_ucounts(task)      (task_cred_xxx((task), ucounts))
 416
 417 #define current_cred_xxx(xxx)                   \
 418 ({                                              \
 419         current_cred()->xxx;                    \
 420 })
 421
 422 #define current_uid()           (current_cred_xxx(uid))
 423 #define current_gid()           (current_cred_xxx(gid))
 424 #define current_euid()          (current_cred_xxx(euid))
 425 #define current_egid()          (current_cred_xxx(egid))
 426 #define current_suid()          (current_cred_xxx(suid))
 427 #define current_sgid()          (current_cred_xxx(sgid))
 428 #define current_fsuid()         (current_cred_xxx(fsuid))
 429 #define current_fsgid()         (current_cred_xxx(fsgid))
 430 #define current_cap()           (current_cred_xxx(cap_effective))
 431 #define current_user()          (current_cred_xxx(user))
 432 #define current_ucounts()       (current_cred_xxx(ucounts))
 433
 434 extern struct user_namespace init_user_ns;
 435 #ifdef CONFIG_USER_NS
 436 #define current_user_ns()       (current_cred_xxx(user_ns))
 437 #else
 438 static inline struct user_namespace *current_user_ns(void)
 439 {
 440         return &init_user_ns;
 441 }
 442 #endif
 443
 444
 445 #define current_uid_gid(_uid, _gid)             \
 446 do {                                            \
 447         const struct cred *__cred;              \
 448         __cred = current_cred();                \
 449         *(_uid) = __cred->uid;                  \
 450         *(_gid) = __cred->gid;                  \
 451 } while(0)
 452
 453 #define current_euid_egid(_euid, _egid)         \
 454 do {                                            \
 455         const struct cred *__cred;              \
 456         __cred = current_cred();                \
 457         *(_euid) = __cred->euid;                \
 458         *(_egid) = __cred->egid;                \
 459 } while(0)
 460
 461 #define current_fsuid_fsgid(_fsuid, _fsgid)     \
 462 do {                                            \
 463         const struct cred *__cred;              \
 464         __cred = current_cred();                \
 465         *(_fsuid) = __cred->fsuid;              \
 466         *(_fsgid) = __cred->fsgid;              \
 467 } while(0)
 468
 469 #endif /* _LINUX_CRED_H */