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_t        usage;
 112 #ifdef CONFIG_DEBUG_CREDENTIALS
 113         atomic_t        subscribers;    /* number of processes subscribed */
 114         void            *put_addr;
 115         unsigned        magic;
 116 #define CRED_MAGIC      0x43736564
 117 #define CRED_MAGIC_DEAD 0x44656144
 118 #endif
 119         kuid_t          uid;            /* real UID of the task */
 120         kgid_t          gid;            /* real GID of the task */
 121         kuid_t          suid;           /* saved UID of the task */
 122         kgid_t          sgid;           /* saved GID of the task */
 123         kuid_t          euid;           /* effective UID of the task */
 124         kgid_t          egid;           /* effective GID of the task */
 125         kuid_t          fsuid;          /* UID for VFS ops */
 126         kgid_t          fsgid;          /* GID for VFS ops */
 127         unsigned        securebits;     /* SUID-less security management */
 128         kernel_cap_t    cap_inheritable; /* caps our children can inherit */
 129         kernel_cap_t    cap_permitted;  /* caps we're permitted */
 130         kernel_cap_t    cap_effective;  /* caps we can actually use */
 131         kernel_cap_t    cap_bset;       /* capability bounding set */
 132         kernel_cap_t    cap_ambient;    /* Ambient capability set */
 133 #ifdef CONFIG_KEYS
 134         unsigned char   jit_keyring;    /* default keyring to attach requested
 135                                          * keys to */
 136         struct key      *session_keyring; /* keyring inherited over fork */
 137         struct key      *process_keyring; /* keyring private to this process */
 138         struct key      *thread_keyring; /* keyring private to this thread */
 139         struct key      *request_key_auth; /* assumed request_key authority */
 140 #endif
 141 #ifdef CONFIG_SECURITY
 142         void            *security;      /* LSM security */
 143 #endif
 144         struct user_struct *user;       /* real user ID subscription */
 145         struct user_namespace *user_ns; /* user_ns the caps and keyrings are relative to. */
 146         struct group_info *group_info;  /* supplementary groups for euid/fsgid */
 147         /* RCU deletion */
 148         union {
 149                 int non_rcu;                    /* Can we skip RCU deletion? */
 150                 struct rcu_head rcu;            /* RCU deletion hook */
 151         };
 152 } __randomize_layout;
 153
 154 extern void __put_cred(struct cred *);
 155 extern void exit_creds(struct task_struct *);
 156 extern int copy_creds(struct task_struct *, unsigned long);
 157 extern const struct cred *get_task_cred(struct task_struct *);
 158 extern struct cred *cred_alloc_blank(void);
 159 extern struct cred *prepare_creds(void);
 160 extern struct cred *prepare_exec_creds(void);
 161 extern int commit_creds(struct cred *);
 162 extern void abort_creds(struct cred *);
 163 extern const struct cred *override_creds(const struct cred *);
 164 extern void revert_creds(const struct cred *);
 165 extern struct cred *prepare_kernel_cred(struct task_struct *);
 166 extern int change_create_files_as(struct cred *, struct inode *);
 167 extern int set_security_override(struct cred *, u32);
 168 extern int set_security_override_from_ctx(struct cred *, const char *);
 169 extern int set_create_files_as(struct cred *, struct inode *);
 170 extern int cred_fscmp(const struct cred *, const struct cred *);
 171 extern void __init cred_init(void);
 172
 173 /*
 174  * check for validity of credentials
 175  */
 176 #ifdef CONFIG_DEBUG_CREDENTIALS
 177 extern void __invalid_creds(const struct cred *, const char *, unsigned);
 178 extern void __validate_process_creds(struct task_struct *,
 179                                      const char *, unsigned);
 180
 181 extern bool creds_are_invalid(const struct cred *cred);
 182
 183 static inline void __validate_creds(const struct cred *cred,
 184                                     const char *file, unsigned line)
 185 {
 186         if (unlikely(creds_are_invalid(cred)))
 187                 __invalid_creds(cred, file, line);
 188 }
 189
 190 #define validate_creds(cred)                            \
 191 do {                                                    \
 192         __validate_creds((cred), __FILE__, __LINE__);   \
 193 } while(0)
 194
 195 #define validate_process_creds()                                \
 196 do {                                                            \
 197         __validate_process_creds(current, __FILE__, __LINE__);  \
 198 } while(0)
 199
 200 extern void validate_creds_for_do_exit(struct task_struct *);
 201 #else
 202 static inline void validate_creds(const struct cred *cred)
 203 {
 204 }
 205 static inline void validate_creds_for_do_exit(struct task_struct *tsk)
 206 {
 207 }
 208 static inline void validate_process_creds(void)
 209 {
 210 }
 211 #endif
 212
 213 static inline bool cap_ambient_invariant_ok(const struct cred *cred)
 214 {
 215         return cap_issubset(cred->cap_ambient,
 216                             cap_intersect(cred->cap_permitted,
 217                                           cred->cap_inheritable));
 218 }
 219
 220 /**
 221  * get_new_cred - Get a reference on a new set of credentials
 222  * @cred: The new credentials to reference
 223  *
 224  * Get a reference on the specified set of new credentials.  The caller must
 225  * release the reference.
 226  */
 227 static inline struct cred *get_new_cred(struct cred *cred)
 228 {
 229         atomic_inc(&cred->usage);
 230         return cred;
 231 }
 232
 233 /**
 234  * get_cred - Get a reference on a set of credentials
 235  * @cred: The credentials to reference
 236  *
 237  * Get a reference on the specified set of credentials.  The caller must
 238  * release the reference.  If %NULL is passed, it is returned with no action.
 239  *
 240  * This is used to deal with a committed set of credentials.  Although the
 241  * pointer is const, this will temporarily discard the const and increment the
 242  * usage count.  The purpose of this is to attempt to catch at compile time the
 243  * accidental alteration of a set of credentials that should be considered
 244  * immutable.
 245  */
 246 static inline const struct cred *get_cred(const struct cred *cred)
 247 {
 248         struct cred *nonconst_cred = (struct cred *) cred;
 249         if (!cred)
 250                 return cred;
 251         validate_creds(cred);
 252         nonconst_cred->non_rcu = 0;
 253         return get_new_cred(nonconst_cred);
 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_inc_not_zero(&nonconst_cred->usage))
 262                 return NULL;
 263         validate_creds(cred);
 264         nonconst_cred->non_rcu = 0;
 265         return cred;
 266 }
 267
 268 /**
 269  * put_cred - Release a reference to a set of credentials
 270  * @cred: The credentials 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(const struct cred *_cred)
 280 {
 281         struct cred *cred = (struct cred *) _cred;
 282
 283         if (cred) {
 284                 validate_creds(cred);
 285                 if (atomic_dec_and_test(&(cred)->usage))
 286                         __put_cred(cred);
 287         }
 288 }
 289
 290 /**
 291  * current_cred - Access the current task's subjective credentials
 292  *
 293  * Access the subjective credentials of the current task.  RCU-safe,
 294  * since nobody else can modify it.
 295  */
 296 #define current_cred() \
 297         rcu_dereference_protected(current->cred, 1)
 298
 299 /**
 300  * current_real_cred - Access the current task's objective credentials
 301  *
 302  * Access the objective credentials of the current task.  RCU-safe,
 303  * since nobody else can modify it.
 304  */
 305 #define current_real_cred() \
 306         rcu_dereference_protected(current->real_cred, 1)
 307
 308 /**
 309  * __task_cred - Access a task's objective credentials
 310  * @task: The task to query
 311  *
 312  * Access the objective credentials of a task.  The caller must hold the RCU
 313  * readlock.
 314  *
 315  * The result of this function should not be passed directly to get_cred();
 316  * rather get_task_cred() should be used instead.
 317  */
 318 #define __task_cred(task)       \
 319         rcu_dereference((task)->real_cred)
 320
 321 /**
 322  * get_current_cred - Get the current task's subjective credentials
 323  *
 324  * Get the subjective credentials of the current task, pinning them so that
 325  * they can't go away.  Accessing the current task's credentials directly is
 326  * not permitted.
 327  */
 328 #define get_current_cred()                              \
 329         (get_cred(current_cred()))
 330
 331 /**
 332  * get_current_user - Get the current task's user_struct
 333  *
 334  * Get the user record of the current task, pinning it so that it can't go
 335  * away.
 336  */
 337 #define get_current_user()                              \
 338 ({                                                      \
 339         struct user_struct *__u;                        \
 340         const struct cred *__cred;                      \
 341         __cred = current_cred();                        \
 342         __u = get_uid(__cred->user);                    \
 343         __u;                                            \
 344 })
 345
 346 /**
 347  * get_current_groups - Get the current task's supplementary group list
 348  *
 349  * Get the supplementary group list of the current task, pinning it so that it
 350  * can't go away.
 351  */
 352 #define get_current_groups()                            \
 353 ({                                                      \
 354         struct group_info *__groups;                    \
 355         const struct cred *__cred;                      \
 356         __cred = current_cred();                        \
 357         __groups = get_group_info(__cred->group_info);  \
 358         __groups;                                       \
 359 })
 360
 361 #define task_cred_xxx(task, xxx)                        \
 362 ({                                                      \
 363         __typeof__(((struct cred *)NULL)->xxx) ___val;  \
 364         rcu_read_lock();                                \
 365         ___val = __task_cred((task))->xxx;              \
 366         rcu_read_unlock();                              \
 367         ___val;                                         \
 368 })
 369
 370 #define task_uid(task)          (task_cred_xxx((task), uid))
 371 #define task_euid(task)         (task_cred_xxx((task), euid))
 372
 373 #define current_cred_xxx(xxx)                   \
 374 ({                                              \
 375         current_cred()->xxx;                    \
 376 })
 377
 378 #define current_uid()           (current_cred_xxx(uid))
 379 #define current_gid()           (current_cred_xxx(gid))
 380 #define current_euid()          (current_cred_xxx(euid))
 381 #define current_egid()          (current_cred_xxx(egid))
 382 #define current_suid()          (current_cred_xxx(suid))
 383 #define current_sgid()          (current_cred_xxx(sgid))
 384 #define current_fsuid()         (current_cred_xxx(fsuid))
 385 #define current_fsgid()         (current_cred_xxx(fsgid))
 386 #define current_cap()           (current_cred_xxx(cap_effective))
 387 #define current_user()          (current_cred_xxx(user))
 388
 389 extern struct user_namespace init_user_ns;
 390 #ifdef CONFIG_USER_NS
 391 #define current_user_ns()       (current_cred_xxx(user_ns))
 392 #else
 393 static inline struct user_namespace *current_user_ns(void)
 394 {
 395         return &init_user_ns;
 396 }
 397 #endif
 398
 399
 400 #define current_uid_gid(_uid, _gid)             \
 401 do {                                            \
 402         const struct cred *__cred;              \
 403         __cred = current_cred();                \
 404         *(_uid) = __cred->uid;                  \
 405         *(_gid) = __cred->gid;                  \
 406 } while(0)
 407
 408 #define current_euid_egid(_euid, _egid)         \
 409 do {                                            \
 410         const struct cred *__cred;              \
 411         __cred = current_cred();                \
 412         *(_euid) = __cred->euid;                \
 413         *(_egid) = __cred->egid;                \
 414 } while(0)
 415
 416 #define current_fsuid_fsgid(_fsuid, _fsgid)     \
 417 do {                                            \
 418         const struct cred *__cred;              \
 419         __cred = current_cred();                \
 420         *(_fsuid) = __cred->fsuid;              \
 421         *(_fsgid) = __cred->fsgid;              \
 422 } while(0)
 423
 424 #endif /* _LINUX_CRED_H */