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[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         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         struct rcu_head rcu;            /* RCU deletion hook */
 149 } __randomize_layout;
 150
 151 extern void __put_cred(struct cred *);
 152 extern void exit_creds(struct task_struct *);
 153 extern int copy_creds(struct task_struct *, unsigned long);
 154 extern const struct cred *get_task_cred(struct task_struct *);
 155 extern struct cred *cred_alloc_blank(void);
 156 extern struct cred *prepare_creds(void);
 157 extern struct cred *prepare_exec_creds(void);
 158 extern int commit_creds(struct cred *);
 159 extern void abort_creds(struct cred *);
 160 extern const struct cred *override_creds(const struct cred *);
 161 extern void revert_creds(const struct cred *);
 162 extern struct cred *prepare_kernel_cred(struct task_struct *);
 163 extern int change_create_files_as(struct cred *, struct inode *);
 164 extern int set_security_override(struct cred *, u32);
 165 extern int set_security_override_from_ctx(struct cred *, const char *);
 166 extern int set_create_files_as(struct cred *, struct inode *);
 167 extern int cred_fscmp(const struct cred *, const struct cred *);
 168 extern void __init cred_init(void);
 169
 170 /*
 171  * check for validity of credentials
 172  */
 173 #ifdef CONFIG_DEBUG_CREDENTIALS
 174 extern void __invalid_creds(const struct cred *, const char *, unsigned);
 175 extern void __validate_process_creds(struct task_struct *,
 176                                      const char *, unsigned);
 177
 178 extern bool creds_are_invalid(const struct cred *cred);
 179
 180 static inline void __validate_creds(const struct cred *cred,
 181                                     const char *file, unsigned line)
 182 {
 183         if (unlikely(creds_are_invalid(cred)))
 184                 __invalid_creds(cred, file, line);
 185 }
 186
 187 #define validate_creds(cred)                            \
 188 do {                                                    \
 189         __validate_creds((cred), __FILE__, __LINE__);   \
 190 } while(0)
 191
 192 #define validate_process_creds()                                \
 193 do {                                                            \
 194         __validate_process_creds(current, __FILE__, __LINE__);  \
 195 } while(0)
 196
 197 extern void validate_creds_for_do_exit(struct task_struct *);
 198 #else
 199 static inline void validate_creds(const struct cred *cred)
 200 {
 201 }
 202 static inline void validate_creds_for_do_exit(struct task_struct *tsk)
 203 {
 204 }
 205 static inline void validate_process_creds(void)
 206 {
 207 }
 208 #endif
 209
 210 static inline bool cap_ambient_invariant_ok(const struct cred *cred)
 211 {
 212         return cap_issubset(cred->cap_ambient,
 213                             cap_intersect(cred->cap_permitted,
 214                                           cred->cap_inheritable));
 215 }
 216
 217 /**
 218  * get_new_cred - Get a reference on a new set of credentials
 219  * @cred: The new credentials to reference
 220  *
 221  * Get a reference on the specified set of new credentials.  The caller must
 222  * release the reference.
 223  */
 224 static inline struct cred *get_new_cred(struct cred *cred)
 225 {
 226         atomic_inc(&cred->usage);
 227         return cred;
 228 }
 229
 230 /**
 231  * get_cred - Get a reference on a set of credentials
 232  * @cred: The credentials to reference
 233  *
 234  * Get a reference on the specified set of credentials.  The caller must
 235  * release the reference.  If %NULL is passed, it is returned with no action.
 236  *
 237  * This is used to deal with a committed set of credentials.  Although the
 238  * pointer is const, this will temporarily discard the const and increment the
 239  * usage count.  The purpose of this is to attempt to catch at compile time the
 240  * accidental alteration of a set of credentials that should be considered
 241  * immutable.
 242  */
 243 static inline const struct cred *get_cred(const struct cred *cred)
 244 {
 245         struct cred *nonconst_cred = (struct cred *) cred;
 246         if (!cred)
 247                 return cred;
 248         validate_creds(cred);
 249         return get_new_cred(nonconst_cred);
 250 }
 251
 252 static inline const struct cred *get_cred_rcu(const struct cred *cred)
 253 {
 254         struct cred *nonconst_cred = (struct cred *) cred;
 255         if (!cred)
 256                 return NULL;
 257         if (!atomic_inc_not_zero(&nonconst_cred->usage))
 258                 return NULL;
 259         validate_creds(cred);
 260         return cred;
 261 }
 262
 263 /**
 264  * put_cred - Release a reference to a set of credentials
 265  * @cred: The credentials to release
 266  *
 267  * Release a reference to a set of credentials, deleting them when the last ref
 268  * is released.  If %NULL is passed, nothing is done.
 269  *
 270  * This takes a const pointer to a set of credentials because the credentials
 271  * on task_struct are attached by const pointers to prevent accidental
 272  * alteration of otherwise immutable credential sets.
 273  */
 274 static inline void put_cred(const struct cred *_cred)
 275 {
 276         struct cred *cred = (struct cred *) _cred;
 277
 278         if (cred) {
 279                 validate_creds(cred);
 280                 if (atomic_dec_and_test(&(cred)->usage))
 281                         __put_cred(cred);
 282         }
 283 }
 284
 285 /**
 286  * current_cred - Access the current task's subjective credentials
 287  *
 288  * Access the subjective credentials of the current task.  RCU-safe,
 289  * since nobody else can modify it.
 290  */
 291 #define current_cred() \
 292         rcu_dereference_protected(current->cred, 1)
 293
 294 /**
 295  * current_real_cred - Access the current task's objective credentials
 296  *
 297  * Access the objective credentials of the current task.  RCU-safe,
 298  * since nobody else can modify it.
 299  */
 300 #define current_real_cred() \
 301         rcu_dereference_protected(current->real_cred, 1)
 302
 303 /**
 304  * __task_cred - Access a task's objective credentials
 305  * @task: The task to query
 306  *
 307  * Access the objective credentials of a task.  The caller must hold the RCU
 308  * readlock.
 309  *
 310  * The result of this function should not be passed directly to get_cred();
 311  * rather get_task_cred() should be used instead.
 312  */
 313 #define __task_cred(task)       \
 314         rcu_dereference((task)->real_cred)
 315
 316 /**
 317  * get_current_cred - Get the current task's subjective credentials
 318  *
 319  * Get the subjective credentials of the current task, pinning them so that
 320  * they can't go away.  Accessing the current task's credentials directly is
 321  * not permitted.
 322  */
 323 #define get_current_cred()                              \
 324         (get_cred(current_cred()))
 325
 326 /**
 327  * get_current_user - Get the current task's user_struct
 328  *
 329  * Get the user record of the current task, pinning it so that it can't go
 330  * away.
 331  */
 332 #define get_current_user()                              \
 333 ({                                                      \
 334         struct user_struct *__u;                        \
 335         const struct cred *__cred;                      \
 336         __cred = current_cred();                        \
 337         __u = get_uid(__cred->user);                    \
 338         __u;                                            \
 339 })
 340
 341 /**
 342  * get_current_groups - Get the current task's supplementary group list
 343  *
 344  * Get the supplementary group list of the current task, pinning it so that it
 345  * can't go away.
 346  */
 347 #define get_current_groups()                            \
 348 ({                                                      \
 349         struct group_info *__groups;                    \
 350         const struct cred *__cred;                      \
 351         __cred = current_cred();                        \
 352         __groups = get_group_info(__cred->group_info);  \
 353         __groups;                                       \
 354 })
 355
 356 #define task_cred_xxx(task, xxx)                        \
 357 ({                                                      \
 358         __typeof__(((struct cred *)NULL)->xxx) ___val;  \
 359         rcu_read_lock();                                \
 360         ___val = __task_cred((task))->xxx;              \
 361         rcu_read_unlock();                              \
 362         ___val;                                         \
 363 })
 364
 365 #define task_uid(task)          (task_cred_xxx((task), uid))
 366 #define task_euid(task)         (task_cred_xxx((task), euid))
 367
 368 #define current_cred_xxx(xxx)                   \
 369 ({                                              \
 370         current_cred()->xxx;                    \
 371 })
 372
 373 #define current_uid()           (current_cred_xxx(uid))
 374 #define current_gid()           (current_cred_xxx(gid))
 375 #define current_euid()          (current_cred_xxx(euid))
 376 #define current_egid()          (current_cred_xxx(egid))
 377 #define current_suid()          (current_cred_xxx(suid))
 378 #define current_sgid()          (current_cred_xxx(sgid))
 379 #define current_fsuid()         (current_cred_xxx(fsuid))
 380 #define current_fsgid()         (current_cred_xxx(fsgid))
 381 #define current_cap()           (current_cred_xxx(cap_effective))
 382 #define current_user()          (current_cred_xxx(user))
 383 #define current_security()      (current_cred_xxx(security))
 384
 385 extern struct user_namespace init_user_ns;
 386 #ifdef CONFIG_USER_NS
 387 #define current_user_ns()       (current_cred_xxx(user_ns))
 388 #else
 389 static inline struct user_namespace *current_user_ns(void)
 390 {
 391         return &init_user_ns;
 392 }
 393 #endif
 394
 395
 396 #define current_uid_gid(_uid, _gid)             \
 397 do {                                            \
 398         const struct cred *__cred;              \
 399         __cred = current_cred();                \
 400         *(_uid) = __cred->uid;                  \
 401         *(_gid) = __cred->gid;                  \
 402 } while(0)
 403
 404 #define current_euid_egid(_euid, _egid)         \
 405 do {                                            \
 406         const struct cred *__cred;              \
 407         __cred = current_cred();                \
 408         *(_euid) = __cred->euid;                \
 409         *(_egid) = __cred->egid;                \
 410 } while(0)
 411
 412 #define current_fsuid_fsgid(_fsuid, _fsgid)     \
 413 do {                                            \
 414         const struct cred *__cred;              \
 415         __cred = current_cred();                \
 416         *(_fsuid) = __cred->fsuid;              \
 417         *(_fsgid) = __cred->fsgid;              \
 418 } while(0)
 419
 420 #endif /* _LINUX_CRED_H */