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 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;      /* 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 static inline bool cap_ambient_invariant_ok(const struct cred *cred)
 215 {
 216         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         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 static inline const struct cred *get_cred(const struct cred *cred)
 248 {
 249         struct cred *nonconst_cred = (struct cred *) cred;
 250         if (!cred)
 251                 return cred;
 252         validate_creds(cred);
 253         nonconst_cred->non_rcu = 0;
 254         return get_new_cred(nonconst_cred);
 255 }
 256
 257 static inline const struct cred *get_cred_rcu(const struct cred *cred)
 258 {
 259         struct cred *nonconst_cred = (struct cred *) cred;
 260         if (!cred)
 261                 return NULL;
 262         if (!atomic_inc_not_zero(&nonconst_cred->usage))
 263                 return NULL;
 264         validate_creds(cred);
 265         nonconst_cred->non_rcu = 0;
 266         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 static inline void put_cred(const struct cred *_cred)
 281 {
 282         struct cred *cred = (struct cred *) _cred;
 283
 284         if (cred) {
 285                 validate_creds(cred);
 286                 if (atomic_dec_and_test(&(cred)->usage))
 287                         __put_cred(cred);
 288         }
 289 }
 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 */