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/selinux.h>
  19 #include <linux/atomic.h>
  20 #include <linux/uidgid.h>
  21 #include <linux/sched.h>
  22 #include <linux/sched/user.h>
  23
  24 struct cred;
  25 struct inode;
  26
  27 /*
  28  * COW Supplementary groups list
  29  */
  30 struct group_info {
  31         atomic_t        usage;
  32         int             ngroups;
  33         kgid_t          gid[0];
  34 } __randomize_layout;
  35
  36 /**
  37  * get_group_info - Get a reference to a group info structure
  38  * @group_info: The group info to reference
  39  *
  40  * This gets a reference to a set of supplementary groups.
  41  *
  42  * If the caller is accessing a task's credentials, they must hold the RCU read
  43  * lock when reading.
  44  */
  45 static inline struct group_info *get_group_info(struct group_info *gi)
  46 {
  47         atomic_inc(&gi->usage);
  48         return gi;
  49 }
  50
  51 /**
  52  * put_group_info - Release a reference to a group info structure
  53  * @group_info: The group info to release
  54  */
  55 #define put_group_info(group_info)                      \
  56 do {                                                    \
  57         if (atomic_dec_and_test(&(group_info)->usage))  \
  58                 groups_free(group_info);                \
  59 } while (0)
  60
  61 extern struct group_info init_groups;
  62 #ifdef CONFIG_MULTIUSER
  63 extern struct group_info *groups_alloc(int);
  64 extern void groups_free(struct group_info *);
  65
  66 extern int in_group_p(kgid_t);
  67 extern int in_egroup_p(kgid_t);
  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 #endif
  82 extern int set_current_groups(struct group_info *);
  83 extern void set_groups(struct cred *, struct group_info *);
  84 extern int groups_search(const struct group_info *, kgid_t);
  85 extern bool may_setgroups(void);
  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 __rcu *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;      /* subjective 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         struct rcu_head rcu;            /* RCU deletion hook */
 148 } __randomize_layout;
 149
 150 extern void __put_cred(struct cred *);
 151 extern void exit_creds(struct task_struct *);
 152 extern int copy_creds(struct task_struct *, unsigned long);
 153 extern const struct cred *get_task_cred(struct task_struct *);
 154 extern struct cred *cred_alloc_blank(void);
 155 extern struct cred *prepare_creds(void);
 156 extern struct cred *prepare_exec_creds(void);
 157 extern int commit_creds(struct cred *);
 158 extern void abort_creds(struct cred *);
 159 extern const struct cred *override_creds(const struct cred *);
 160 extern void revert_creds(const struct cred *);
 161 extern struct cred *prepare_kernel_cred(struct task_struct *);
 162 extern int change_create_files_as(struct cred *, struct inode *);
 163 extern int set_security_override(struct cred *, u32);
 164 extern int set_security_override_from_ctx(struct cred *, const char *);
 165 extern int set_create_files_as(struct cred *, struct inode *);
 166 extern void __init cred_init(void);
 167
 168 /*
 169  * check for validity of credentials
 170  */
 171 #ifdef CONFIG_DEBUG_CREDENTIALS
 172 extern void __invalid_creds(const struct cred *, const char *, unsigned);
 173 extern void __validate_process_creds(struct task_struct *,
 174                                      const char *, unsigned);
 175
 176 extern bool creds_are_invalid(const struct cred *cred);
 177
 178 static inline void __validate_creds(const struct cred *cred,
 179                                     const char *file, unsigned line)
 180 {
 181         if (unlikely(creds_are_invalid(cred)))
 182                 __invalid_creds(cred, file, line);
 183 }
 184
 185 #define validate_creds(cred)                            \
 186 do {                                                    \
 187         __validate_creds((cred), __FILE__, __LINE__);   \
 188 } while(0)
 189
 190 #define validate_process_creds()                                \
 191 do {                                                            \
 192         __validate_process_creds(current, __FILE__, __LINE__);  \
 193 } while(0)
 194
 195 extern void validate_creds_for_do_exit(struct task_struct *);
 196 #else
 197 static inline void validate_creds(const struct cred *cred)
 198 {
 199 }
 200 static inline void validate_creds_for_do_exit(struct task_struct *tsk)
 201 {
 202 }
 203 static inline void validate_process_creds(void)
 204 {
 205 }
 206 #endif
 207
 208 static inline bool cap_ambient_invariant_ok(const struct cred *cred)
 209 {
 210         return cap_issubset(cred->cap_ambient,
 211                             cap_intersect(cred->cap_permitted,
 212                                           cred->cap_inheritable));
 213 }
 214
 215 /**
 216  * get_new_cred - Get a reference on a new set of credentials
 217  * @cred: The new credentials to reference
 218  *
 219  * Get a reference on the specified set of new credentials.  The caller must
 220  * release the reference.
 221  */
 222 static inline struct cred *get_new_cred(struct cred *cred)
 223 {
 224         atomic_inc(&cred->usage);
 225         return cred;
 226 }
 227
 228 /**
 229  * get_cred - Get a reference on a set of credentials
 230  * @cred: The credentials to reference
 231  *
 232  * Get a reference on the specified set of credentials.  The caller must
 233  * release the reference.
 234  *
 235  * This is used to deal with a committed set of credentials.  Although the
 236  * pointer is const, this will temporarily discard the const and increment the
 237  * usage count.  The purpose of this is to attempt to catch at compile time the
 238  * accidental alteration of a set of credentials that should be considered
 239  * immutable.
 240  */
 241 static inline const struct cred *get_cred(const struct cred *cred)
 242 {
 243         struct cred *nonconst_cred = (struct cred *) cred;
 244         validate_creds(cred);
 245         return get_new_cred(nonconst_cred);
 246 }
 247
 248 /**
 249  * put_cred - Release a reference to a set of credentials
 250  * @cred: The credentials to release
 251  *
 252  * Release a reference to a set of credentials, deleting them when the last ref
 253  * is released.
 254  *
 255  * This takes a const pointer to a set of credentials because the credentials
 256  * on task_struct are attached by const pointers to prevent accidental
 257  * alteration of otherwise immutable credential sets.
 258  */
 259 static inline void put_cred(const struct cred *_cred)
 260 {
 261         struct cred *cred = (struct cred *) _cred;
 262
 263         validate_creds(cred);
 264         if (atomic_dec_and_test(&(cred)->usage))
 265                 __put_cred(cred);
 266 }
 267
 268 /**
 269  * current_cred - Access the current task's subjective credentials
 270  *
 271  * Access the subjective credentials of the current task.  RCU-safe,
 272  * since nobody else can modify it.
 273  */
 274 #define current_cred() \
 275         rcu_dereference_protected(current->cred, 1)
 276
 277 /**
 278  * current_real_cred - Access the current task's objective credentials
 279  *
 280  * Access the objective credentials of the current task.  RCU-safe,
 281  * since nobody else can modify it.
 282  */
 283 #define current_real_cred() \
 284         rcu_dereference_protected(current->real_cred, 1)
 285
 286 /**
 287  * __task_cred - Access a task's objective credentials
 288  * @task: The task to query
 289  *
 290  * Access the objective credentials of a task.  The caller must hold the RCU
 291  * readlock.
 292  *
 293  * The result of this function should not be passed directly to get_cred();
 294  * rather get_task_cred() should be used instead.
 295  */
 296 #define __task_cred(task)       \
 297         rcu_dereference((task)->real_cred)
 298
 299 /**
 300  * get_current_cred - Get the current task's subjective credentials
 301  *
 302  * Get the subjective credentials of the current task, pinning them so that
 303  * they can't go away.  Accessing the current task's credentials directly is
 304  * not permitted.
 305  */
 306 #define get_current_cred()                              \
 307         (get_cred(current_cred()))
 308
 309 /**
 310  * get_current_user - Get the current task's user_struct
 311  *
 312  * Get the user record of the current task, pinning it so that it can't go
 313  * away.
 314  */
 315 #define get_current_user()                              \
 316 ({                                                      \
 317         struct user_struct *__u;                        \
 318         const struct cred *__cred;                      \
 319         __cred = current_cred();                        \
 320         __u = get_uid(__cred->user);                    \
 321         __u;                                            \
 322 })
 323
 324 /**
 325  * get_current_groups - Get the current task's supplementary group list
 326  *
 327  * Get the supplementary group list of the current task, pinning it so that it
 328  * can't go away.
 329  */
 330 #define get_current_groups()                            \
 331 ({                                                      \
 332         struct group_info *__groups;                    \
 333         const struct cred *__cred;                      \
 334         __cred = current_cred();                        \
 335         __groups = get_group_info(__cred->group_info);  \
 336         __groups;                                       \
 337 })
 338
 339 #define task_cred_xxx(task, xxx)                        \
 340 ({                                                      \
 341         __typeof__(((struct cred *)NULL)->xxx) ___val;  \
 342         rcu_read_lock();                                \
 343         ___val = __task_cred((task))->xxx;              \
 344         rcu_read_unlock();                              \
 345         ___val;                                         \
 346 })
 347
 348 #define task_uid(task)          (task_cred_xxx((task), uid))
 349 #define task_euid(task)         (task_cred_xxx((task), euid))
 350
 351 #define current_cred_xxx(xxx)                   \
 352 ({                                              \
 353         current_cred()->xxx;                    \
 354 })
 355
 356 #define current_uid()           (current_cred_xxx(uid))
 357 #define current_gid()           (current_cred_xxx(gid))
 358 #define current_euid()          (current_cred_xxx(euid))
 359 #define current_egid()          (current_cred_xxx(egid))
 360 #define current_suid()          (current_cred_xxx(suid))
 361 #define current_sgid()          (current_cred_xxx(sgid))
 362 #define current_fsuid()         (current_cred_xxx(fsuid))
 363 #define current_fsgid()         (current_cred_xxx(fsgid))
 364 #define current_cap()           (current_cred_xxx(cap_effective))
 365 #define current_user()          (current_cred_xxx(user))
 366 #define current_security()      (current_cred_xxx(security))
 367
 368 extern struct user_namespace init_user_ns;
 369 #ifdef CONFIG_USER_NS
 370 #define current_user_ns()       (current_cred_xxx(user_ns))
 371 #else
 372 static inline struct user_namespace *current_user_ns(void)
 373 {
 374         return &init_user_ns;
 375 }
 376 #endif
 377
 378
 379 #define current_uid_gid(_uid, _gid)             \
 380 do {                                            \
 381         const struct cred *__cred;              \
 382         __cred = current_cred();                \
 383         *(_uid) = __cred->uid;                  \
 384         *(_gid) = __cred->gid;                  \
 385 } while(0)
 386
 387 #define current_euid_egid(_euid, _egid)         \
 388 do {                                            \
 389         const struct cred *__cred;              \
 390         __cred = current_cred();                \
 391         *(_euid) = __cred->euid;                \
 392         *(_egid) = __cred->egid;                \
 393 } while(0)
 394
 395 #define current_fsuid_fsgid(_fsuid, _fsgid)     \
 396 do {                                            \
 397         const struct cred *__cred;              \
 398         __cred = current_cred();                \
 399         *(_fsuid) = __cred->fsuid;              \
 400         *(_fsgid) = __cred->fsgid;              \
 401 } while(0)
 402
 403 #endif /* _LINUX_CRED_H */