include/linux/cred.h

   1 /* Credentials management - see Documentation/security/credentials.rst
   2  *
   3  * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved.
   4  * Written by David Howells (dhowells@redhat.com)
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public Licence
   8  * as published by the Free Software Foundation; either version
   9  * 2 of the Licence, or (at your option) any later version.
  10  */
  11
  12 #ifndef _LINUX_CRED_H
  13 #define _LINUX_CRED_H
  14
  15 #include <linux/capability.h>
  16 #include <linux/init.h>
  17 #include <linux/key.h>
  18 #include <linux/atomic.h>
  19 #include <linux/uidgid.h>
  20 #include <linux/sched.h>
  21 #include <linux/sched/user.h>
  22
  23 struct cred;
  24 struct inode;
  25
  26 /*
  27  * COW Supplementary groups list
  28  */
  29 struct group_info {
  30         atomic_t        usage;
  31         int             ngroups;
  32         kgid_t          gid[0];
  33 } __randomize_layout;
  34
  35 /**
  36  * get_group_info - Get a reference to a group info structure
  37  * @group_info: The group info to reference
  38  *
  39  * This gets a reference to a set of supplementary groups.
  40  *
  41  * If the caller is accessing a task's credentials, they must hold the RCU read
  42  * lock when reading.
  43  */
  44 static inline struct group_info *get_group_info(struct group_info *gi)
  45 {
  46         atomic_inc(&gi->usage);
  47         return gi;
  48 }
  49
  50 /**
  51  * put_group_info - Release a reference to a group info structure
  52  * @group_info: The group info to release
  53  */
  54 #define put_group_info(group_info)                      \
  55 do {                                                    \
  56         if (atomic_dec_and_test(&(group_info)->usage))  \
  57                 groups_free(group_info);                \
  58 } while (0)
  59
  60 extern struct group_info init_groups;
  61 #ifdef CONFIG_MULTIUSER
  62 extern struct group_info *groups_alloc(int);
  63 extern void groups_free(struct group_info *);
  64
  65 extern int in_group_p(kgid_t);
  66 extern int in_egroup_p(kgid_t);
  67 extern int groups_search(const struct group_info *, kgid_t);
  68
  69 extern int set_current_groups(struct group_info *);
  70 extern void set_groups(struct cred *, struct group_info *);
  71 extern bool may_setgroups(void);
  72 extern void groups_sort(struct group_info *);
  73 #else
  74 static inline void groups_free(struct group_info *group_info)
  75 {
  76 }
  77
  78 static inline int in_group_p(kgid_t grp)
  79 {
  80         return 1;
  81 }
  82 static inline int in_egroup_p(kgid_t grp)
  83 {
  84         return 1;
  85 }
  86 static inline int groups_search(const struct group_info *group_info, kgid_t grp)
  87 {
  88         return 1;
  89 }
  90 #endif
  91
  92 /*
  93  * The security context of a task
  94  *
  95  * The parts of the context break down into two categories:
  96  *
  97  *  (1) The objective context of a task.  These parts are used when some other
  98  *      task is attempting to affect this one.
  99  *
 100  *  (2) The subjective context.  These details are used when the task is acting
 101  *      upon another object, be that a file, a task, a key or whatever.
 102  *
 103  * Note that some members of this structure belong to both categories - the
 104  * LSM security pointer for instance.
 105  *
 106  * A task has two security pointers.  task->real_cred points to the objective
 107  * context that defines that task's actual details.  The objective part of this
 108  * context is used whenever that task is acted upon.
 109  *
 110  * task->cred points to the subjective context that defines the details of how
 111  * that task is going to act upon another object.  This may be overridden
 112  * temporarily to point to another security context, but normally points to the
 113  * same context as task->real_cred.
 114  */
 115 struct cred {
 116         atomic_t        usage;
 117 #ifdef CONFIG_DEBUG_CREDENTIALS
 118         atomic_t        subscribers;    /* number of processes subscribed */
 119         void            *put_addr;
 120         unsigned        magic;
 121 #define CRED_MAGIC      0x43736564
 122 #define CRED_MAGIC_DEAD 0x44656144
 123 #endif
 124         kuid_t          uid;            /* real UID of the task */
 125         kgid_t          gid;            /* real GID of the task */
 126         kuid_t          suid;           /* saved UID of the task */
 127         kgid_t          sgid;           /* saved GID of the task */
 128         kuid_t          euid;           /* effective UID of the task */
 129         kgid_t          egid;           /* effective GID of the task */
 130         kuid_t          fsuid;          /* UID for VFS ops */
 131         kgid_t          fsgid;          /* GID for VFS ops */
 132         unsigned        securebits;     /* SUID-less security management */
 133         kernel_cap_t    cap_inheritable; /* caps our children can inherit */
 134         kernel_cap_t    cap_permitted;  /* caps we're permitted */
 135         kernel_cap_t    cap_effective;  /* caps we can actually use */
 136         kernel_cap_t    cap_bset;       /* capability bounding set */
 137         kernel_cap_t    cap_ambient;    /* Ambient capability set */
 138 #ifdef CONFIG_KEYS
 139         unsigned char   jit_keyring;    /* default keyring to attach requested
 140                                          * keys to */
 141         struct key      *session_keyring; /* keyring inherited over fork */
 142         struct key      *process_keyring; /* keyring private to this process */
 143         struct key      *thread_keyring; /* keyring private to this thread */
 144         struct key      *request_key_auth; /* assumed request_key authority */
 145 #endif
 146 #ifdef CONFIG_SECURITY
 147         void            *security;      /* subjective LSM security */
 148 #endif
 149         struct user_struct *user;       /* real user ID subscription */
 150         struct user_namespace *user_ns; /* user_ns the caps and keyrings are relative to. */
 151         struct group_info *group_info;  /* supplementary groups for euid/fsgid */
 152         struct rcu_head rcu;            /* RCU deletion hook */
 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         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         return cred;
 265 }
 266
 267 /**
 268  * put_cred - Release a reference to a set of credentials
 269  * @cred: The credentials to release
 270  *
 271  * Release a reference to a set of credentials, deleting them when the last ref
 272  * is released.  If %NULL is passed, nothing is done.
 273  *
 274  * This takes a const pointer to a set of credentials because the credentials
 275  * on task_struct are attached by const pointers to prevent accidental
 276  * alteration of otherwise immutable credential sets.
 277  */
 278 static inline void put_cred(const struct cred *_cred)
 279 {
 280         struct cred *cred = (struct cred *) _cred;
 281
 282         if (cred) {
 283                 validate_creds(cred);
 284                 if (atomic_dec_and_test(&(cred)->usage))
 285                         __put_cred(cred);
 286         }
 287 }
 288
 289 /**
 290  * current_cred - Access the current task's subjective credentials
 291  *
 292  * Access the subjective credentials of the current task.  RCU-safe,
 293  * since nobody else can modify it.
 294  */
 295 #define current_cred() \
 296         rcu_dereference_protected(current->cred, 1)
 297
 298 /**
 299  * current_real_cred - Access the current task's objective credentials
 300  *
 301  * Access the objective credentials of the current task.  RCU-safe,
 302  * since nobody else can modify it.
 303  */
 304 #define current_real_cred() \
 305         rcu_dereference_protected(current->real_cred, 1)
 306
 307 /**
 308  * __task_cred - Access a task's objective credentials
 309  * @task: The task to query
 310  *
 311  * Access the objective credentials of a task.  The caller must hold the RCU
 312  * readlock.
 313  *
 314  * The result of this function should not be passed directly to get_cred();
 315  * rather get_task_cred() should be used instead.
 316  */
 317 #define __task_cred(task)       \
 318         rcu_dereference((task)->real_cred)
 319
 320 /**
 321  * get_current_cred - Get the current task's subjective credentials
 322  *
 323  * Get the subjective credentials of the current task, pinning them so that
 324  * they can't go away.  Accessing the current task's credentials directly is
 325  * not permitted.
 326  */
 327 #define get_current_cred()                              \
 328         (get_cred(current_cred()))
 329
 330 /**
 331  * get_current_user - Get the current task's user_struct
 332  *
 333  * Get the user record of the current task, pinning it so that it can't go
 334  * away.
 335  */
 336 #define get_current_user()                              \
 337 ({                                                      \
 338         struct user_struct *__u;                        \
 339         const struct cred *__cred;                      \
 340         __cred = current_cred();                        \
 341         __u = get_uid(__cred->user);                    \
 342         __u;                                            \
 343 })
 344
 345 /**
 346  * get_current_groups - Get the current task's supplementary group list
 347  *
 348  * Get the supplementary group list of the current task, pinning it so that it
 349  * can't go away.
 350  */
 351 #define get_current_groups()                            \
 352 ({                                                      \
 353         struct group_info *__groups;                    \
 354         const struct cred *__cred;                      \
 355         __cred = current_cred();                        \
 356         __groups = get_group_info(__cred->group_info);  \
 357         __groups;                                       \
 358 })
 359
 360 #define task_cred_xxx(task, xxx)                        \
 361 ({                                                      \
 362         __typeof__(((struct cred *)NULL)->xxx) ___val;  \
 363         rcu_read_lock();                                \
 364         ___val = __task_cred((task))->xxx;              \
 365         rcu_read_unlock();                              \
 366         ___val;                                         \
 367 })
 368
 369 #define task_uid(task)          (task_cred_xxx((task), uid))
 370 #define task_euid(task)         (task_cred_xxx((task), euid))
 371
 372 #define current_cred_xxx(xxx)                   \
 373 ({                                              \
 374         current_cred()->xxx;                    \
 375 })
 376
 377 #define current_uid()           (current_cred_xxx(uid))
 378 #define current_gid()           (current_cred_xxx(gid))
 379 #define current_euid()          (current_cred_xxx(euid))
 380 #define current_egid()          (current_cred_xxx(egid))
 381 #define current_suid()          (current_cred_xxx(suid))
 382 #define current_sgid()          (current_cred_xxx(sgid))
 383 #define current_fsuid()         (current_cred_xxx(fsuid))
 384 #define current_fsgid()         (current_cred_xxx(fsgid))
 385 #define current_cap()           (current_cred_xxx(cap_effective))
 386 #define current_user()          (current_cred_xxx(user))
 387 #define current_security()      (current_cred_xxx(security))
 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 */