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 struct lsmblob;
  22
  23 /*
  24  * COW Supplementary groups list
  25  */
  26 struct group_info {
  27         atomic_t        usage;
  28         int             ngroups;
  29         kgid_t          gid[0];
  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         atomic_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 (atomic_dec_and_test(&(group_info)->usage))  \
  54                 groups_free(group_info);                \
  55 } while (0)
  56
  57 extern struct group_info init_groups;
  58 #ifdef CONFIG_MULTIUSER
  59 extern struct group_info *groups_alloc(int);
  60 extern void groups_free(struct group_info *);
  61
  62 extern int in_group_p(kgid_t);
  63 extern int in_egroup_p(kgid_t);
  64 extern int groups_search(const struct group_info *, kgid_t);
  65
  66 extern int set_current_groups(struct group_info *);
  67 extern void set_groups(struct cred *, struct group_info *);
  68 extern bool may_setgroups(void);
  69 extern void groups_sort(struct group_info *);
  70 #else
  71 static inline void groups_free(struct group_info *group_info)
  72 {
  73 }
  74
  75 static inline int in_group_p(kgid_t grp)
  76 {
  77         return 1;
  78 }
  79 static inline int in_egroup_p(kgid_t grp)
  80 {
  81         return 1;
  82 }
  83 static inline int groups_search(const struct group_info *group_info, kgid_t grp)
  84 {
  85         return 1;
  86 }
  87 #endif
  88
  89 /*
  90  * The security context of a task
  91  *
  92  * The parts of the context break down into two categories:
  93  *
  94  *  (1) The objective context of a task.  These parts are used when some other
  95  *      task is attempting to affect this one.
  96  *
  97  *  (2) The subjective context.  These details are used when the task is acting
  98  *      upon another object, be that a file, a task, a key or whatever.
  99  *
 100  * Note that some members of this structure belong to both categories - the
 101  * LSM security pointer for instance.
 102  *
 103  * A task has two security pointers.  task->real_cred points to the objective
 104  * context that defines that task's actual details.  The objective part of this
 105  * context is used whenever that task is acted upon.
 106  *
 107  * task->cred points to the subjective context that defines the details of how
 108  * that task is going to act upon another object.  This may be overridden
 109  * temporarily to point to another security context, but normally points to the
 110  * same context as task->real_cred.
 111  */
 112 struct cred {
 113         atomic_t        usage;
 114 #ifdef CONFIG_DEBUG_CREDENTIALS
 115         atomic_t        subscribers;    /* number of processes subscribed */
 116         void            *put_addr;
 117         unsigned        magic;
 118 #define CRED_MAGIC      0x43736564
 119 #define CRED_MAGIC_DEAD 0x44656144
 120 #endif
 121         kuid_t          uid;            /* real UID of the task */
 122         kgid_t          gid;            /* real GID of the task */
 123         kuid_t          suid;           /* saved UID of the task */
 124         kgid_t          sgid;           /* saved GID of the task */
 125         kuid_t          euid;           /* effective UID of the task */
 126         kgid_t          egid;           /* effective GID of the task */
 127         kuid_t          fsuid;          /* UID for VFS ops */
 128         kgid_t          fsgid;          /* GID for VFS ops */
 129         unsigned        securebits;     /* SUID-less security management */
 130         kernel_cap_t    cap_inheritable; /* caps our children can inherit */
 131         kernel_cap_t    cap_permitted;  /* caps we're permitted */
 132         kernel_cap_t    cap_effective;  /* caps we can actually use */
 133         kernel_cap_t    cap_bset;       /* capability bounding set */
 134         kernel_cap_t    cap_ambient;    /* Ambient capability set */
 135 #ifdef CONFIG_KEYS
 136         unsigned char   jit_keyring;    /* default keyring to attach requested
 137                                          * keys to */
 138         struct key      *session_keyring; /* keyring inherited over fork */
 139         struct key      *process_keyring; /* keyring private to this process */
 140         struct key      *thread_keyring; /* keyring private to this thread */
 141         struct key      *request_key_auth; /* assumed request_key authority */
 142 #endif
 143 #ifdef CONFIG_SECURITY
 144         void            *security;      /* subjective LSM security */
 145 #endif
 146         struct user_struct *user;       /* real user ID subscription */
 147         struct user_namespace *user_ns; /* user_ns the caps and keyrings are relative to. */
 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 change_create_files_as(struct cred *, struct inode *);
 169 extern int set_security_override(struct cred *, struct lsmblob *);
 170 extern int set_security_override_from_ctx(struct cred *, const char *);
 171 extern int set_create_files_as(struct cred *, struct inode *);
 172 extern int cred_fscmp(const struct cred *, const struct cred *);
 173 extern void __init cred_init(void);
 174
 175 /*
 176  * check for validity of credentials
 177  */
 178 #ifdef CONFIG_DEBUG_CREDENTIALS
 179 extern void __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 - Get a reference on a new set of credentials
 224  * @cred: The new credentials to reference
 225  *
 226  * Get a reference on the specified set of new credentials.  The caller must
 227  * release the reference.
 228  */
 229 static inline struct cred *get_new_cred(struct cred *cred)
 230 {
 231         atomic_inc(&cred->usage);
 232         return cred;
 233 }
 234
 235 /**
 236  * get_cred - Get a reference on a set of credentials
 237  * @cred: The credentials to reference
 238  *
 239  * Get a reference on the specified set of credentials.  The caller must
 240  * release the reference.  If %NULL is passed, it is returned with no action.
 241  *
 242  * This is used to deal with a committed set of credentials.  Although the
 243  * pointer is const, this will temporarily discard the const and increment the
 244  * usage count.  The purpose of this is to attempt to catch at compile time the
 245  * accidental alteration of a set of credentials that should be considered
 246  * immutable.
 247  */
 248 static inline const struct cred *get_cred(const struct cred *cred)
 249 {
 250         struct cred *nonconst_cred = (struct cred *) cred;
 251         if (!cred)
 252                 return cred;
 253         validate_creds(cred);
 254         nonconst_cred->non_rcu = 0;
 255         return get_new_cred(nonconst_cred);
 256 }
 257
 258 static inline const struct cred *get_cred_rcu(const struct cred *cred)
 259 {
 260         struct cred *nonconst_cred = (struct cred *) cred;
 261         if (!cred)
 262                 return NULL;
 263         if (!atomic_inc_not_zero(&nonconst_cred->usage))
 264                 return NULL;
 265         validate_creds(cred);
 266         nonconst_cred->non_rcu = 0;
 267         return cred;
 268 }
 269
 270 /**
 271  * put_cred - Release a reference to a set of credentials
 272  * @cred: The credentials to release
 273  *
 274  * Release a reference to a set of credentials, deleting them when the last ref
 275  * is released.  If %NULL is passed, nothing is done.
 276  *
 277  * This takes a const pointer to a set of credentials because the credentials
 278  * on task_struct are attached by const pointers to prevent accidental
 279  * alteration of otherwise immutable credential sets.
 280  */
 281 static inline void put_cred(const struct cred *_cred)
 282 {
 283         struct cred *cred = (struct cred *) _cred;
 284
 285         if (cred) {
 286                 validate_creds(cred);
 287                 if (atomic_dec_and_test(&(cred)->usage))
 288                         __put_cred(cred);
 289         }
 290 }
 291
 292 /**
 293  * current_cred - Access the current task's subjective credentials
 294  *
 295  * Access the subjective credentials of the current task.  RCU-safe,
 296  * since nobody else can modify it.
 297  */
 298 #define current_cred() \
 299         rcu_dereference_protected(current->cred, 1)
 300
 301 /**
 302  * current_real_cred - Access the current task's objective credentials
 303  *
 304  * Access the objective credentials of the current task.  RCU-safe,
 305  * since nobody else can modify it.
 306  */
 307 #define current_real_cred() \
 308         rcu_dereference_protected(current->real_cred, 1)
 309
 310 /**
 311  * __task_cred - Access a task's objective credentials
 312  * @task: The task to query
 313  *
 314  * Access the objective credentials of a task.  The caller must hold the RCU
 315  * readlock.
 316  *
 317  * The result of this function should not be passed directly to get_cred();
 318  * rather get_task_cred() should be used instead.
 319  */
 320 #define __task_cred(task)       \
 321         rcu_dereference((task)->real_cred)
 322
 323 /**
 324  * get_current_cred - Get the current task's subjective credentials
 325  *
 326  * Get the subjective credentials of the current task, pinning them so that
 327  * they can't go away.  Accessing the current task's credentials directly is
 328  * not permitted.
 329  */
 330 #define get_current_cred()                              \
 331         (get_cred(current_cred()))
 332
 333 /**
 334  * get_current_user - Get the current task's user_struct
 335  *
 336  * Get the user record of the current task, pinning it so that it can't go
 337  * away.
 338  */
 339 #define get_current_user()                              \
 340 ({                                                      \
 341         struct user_struct *__u;                        \
 342         const struct cred *__cred;                      \
 343         __cred = current_cred();                        \
 344         __u = get_uid(__cred->user);                    \
 345         __u;                                            \
 346 })
 347
 348 /**
 349  * get_current_groups - Get the current task's supplementary group list
 350  *
 351  * Get the supplementary group list of the current task, pinning it so that it
 352  * can't go away.
 353  */
 354 #define get_current_groups()                            \
 355 ({                                                      \
 356         struct group_info *__groups;                    \
 357         const struct cred *__cred;                      \
 358         __cred = current_cred();                        \
 359         __groups = get_group_info(__cred->group_info);  \
 360         __groups;                                       \
 361 })
 362
 363 #define task_cred_xxx(task, xxx)                        \
 364 ({                                                      \
 365         __typeof__(((struct cred *)NULL)->xxx) ___val;  \
 366         rcu_read_lock();                                \
 367         ___val = __task_cred((task))->xxx;              \
 368         rcu_read_unlock();                              \
 369         ___val;                                         \
 370 })
 371
 372 #define task_uid(task)          (task_cred_xxx((task), uid))
 373 #define task_euid(task)         (task_cred_xxx((task), euid))
 374
 375 #define current_cred_xxx(xxx)                   \
 376 ({                                              \
 377         current_cred()->xxx;                    \
 378 })
 379
 380 #define current_uid()           (current_cred_xxx(uid))
 381 #define current_gid()           (current_cred_xxx(gid))
 382 #define current_euid()          (current_cred_xxx(euid))
 383 #define current_egid()          (current_cred_xxx(egid))
 384 #define current_suid()          (current_cred_xxx(suid))
 385 #define current_sgid()          (current_cred_xxx(sgid))
 386 #define current_fsuid()         (current_cred_xxx(fsuid))
 387 #define current_fsgid()         (current_cred_xxx(fsgid))
 388 #define current_cap()           (current_cred_xxx(cap_effective))
 389 #define current_user()          (current_cred_xxx(user))
 390
 391 extern struct user_namespace init_user_ns;
 392 #ifdef CONFIG_USER_NS
 393 #define current_user_ns()       (current_cred_xxx(user_ns))
 394 #else
 395 static inline struct user_namespace *current_user_ns(void)
 396 {
 397         return &init_user_ns;
 398 }
 399 #endif
 400
 401
 402 #define current_uid_gid(_uid, _gid)             \
 403 do {                                            \
 404         const struct cred *__cred;              \
 405         __cred = current_cred();                \
 406         *(_uid) = __cred->uid;                  \
 407         *(_gid) = __cred->gid;                  \
 408 } while(0)
 409
 410 #define current_euid_egid(_euid, _egid)         \
 411 do {                                            \
 412         const struct cred *__cred;              \
 413         __cred = current_cred();                \
 414         *(_euid) = __cred->euid;                \
 415         *(_egid) = __cred->egid;                \
 416 } while(0)
 417
 418 #define current_fsuid_fsgid(_fsuid, _fsgid)     \
 419 do {                                            \
 420         const struct cred *__cred;              \
 421         __cred = current_cred();                \
 422         *(_fsuid) = __cred->fsuid;              \
 423         *(_fsgid) = __cred->fsgid;              \
 424 } while(0)
 425
 426 #endif /* _LINUX_CRED_H */