linux/include/linux/cred.h
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   1/* Credentials management - see Documentation/security/credentials.txt
   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
  22struct user_struct;
  23struct cred;
  24struct inode;
  25
  26/*
  27 * COW Supplementary groups list
  28 */
  29#define NGROUPS_SMALL           32
  30#define NGROUPS_PER_BLOCK       ((unsigned int)(PAGE_SIZE / sizeof(kgid_t)))
  31
  32struct group_info {
  33        atomic_t        usage;
  34        int             ngroups;
  35        int             nblocks;
  36        kgid_t          small_block[NGROUPS_SMALL];
  37        kgid_t          *blocks[0];
  38};
  39
  40/**
  41 * get_group_info - Get a reference to a group info structure
  42 * @group_info: The group info to reference
  43 *
  44 * This gets a reference to a set of supplementary groups.
  45 *
  46 * If the caller is accessing a task's credentials, they must hold the RCU read
  47 * lock when reading.
  48 */
  49static inline struct group_info *get_group_info(struct group_info *gi)
  50{
  51        atomic_inc(&gi->usage);
  52        return gi;
  53}
  54
  55/**
  56 * put_group_info - Release a reference to a group info structure
  57 * @group_info: The group info to release
  58 */
  59#define put_group_info(group_info)                      \
  60do {                                                    \
  61        if (atomic_dec_and_test(&(group_info)->usage))  \
  62                groups_free(group_info);                \
  63} while (0)
  64
  65extern struct group_info *groups_alloc(int);
  66extern struct group_info init_groups;
  67extern void groups_free(struct group_info *);
  68extern int set_current_groups(struct group_info *);
  69extern int set_groups(struct cred *, struct group_info *);
  70extern int groups_search(const struct group_info *, kgid_t);
  71
  72/* access the groups "array" with this macro */
  73#define GROUP_AT(gi, i) \
  74        ((gi)->blocks[(i) / NGROUPS_PER_BLOCK][(i) % NGROUPS_PER_BLOCK])
  75
  76extern int in_group_p(kgid_t);
  77extern int in_egroup_p(kgid_t);
  78
  79/*
  80 * The common credentials for a thread group
  81 * - shared by CLONE_THREAD
  82 */
  83#ifdef CONFIG_KEYS
  84struct thread_group_cred {
  85        atomic_t        usage;
  86        pid_t           tgid;                   /* thread group process ID */
  87        spinlock_t      lock;
  88        struct key __rcu *session_keyring;      /* keyring inherited over fork */
  89        struct key      *process_keyring;       /* keyring private to this process */
  90        struct rcu_head rcu;                    /* RCU deletion hook */
  91};
  92#endif
  93
  94/*
  95 * The security context of a task
  96 *
  97 * The parts of the context break down into two categories:
  98 *
  99 *  (1) The objective context of a task.  These parts are used when some other
 100 *      task is attempting to affect this one.
 101 *
 102 *  (2) The subjective context.  These details are used when the task is acting
 103 *      upon another object, be that a file, a task, a key or whatever.
 104 *
 105 * Note that some members of this structure belong to both categories - the
 106 * LSM security pointer for instance.
 107 *
 108 * A task has two security pointers.  task->real_cred points to the objective
 109 * context that defines that task's actual details.  The objective part of this
 110 * context is used whenever that task is acted upon.
 111 *
 112 * task->cred points to the subjective context that defines the details of how
 113 * that task is going to act upon another object.  This may be overridden
 114 * temporarily to point to another security context, but normally points to the
 115 * same context as task->real_cred.
 116 */
 117struct cred {
 118        atomic_t        usage;
 119#ifdef CONFIG_DEBUG_CREDENTIALS
 120        atomic_t        subscribers;    /* number of processes subscribed */
 121        void            *put_addr;
 122        unsigned        magic;
 123#define CRED_MAGIC      0x43736564
 124#define CRED_MAGIC_DEAD 0x44656144
 125#endif
 126        kuid_t          uid;            /* real UID of the task */
 127        kgid_t          gid;            /* real GID of the task */
 128        kuid_t          suid;           /* saved UID of the task */
 129        kgid_t          sgid;           /* saved GID of the task */
 130        kuid_t          euid;           /* effective UID of the task */
 131        kgid_t          egid;           /* effective GID of the task */
 132        kuid_t          fsuid;          /* UID for VFS ops */
 133        kgid_t          fsgid;          /* GID for VFS ops */
 134        unsigned        securebits;     /* SUID-less security management */
 135        kernel_cap_t    cap_inheritable; /* caps our children can inherit */
 136        kernel_cap_t    cap_permitted;  /* caps we're permitted */
 137        kernel_cap_t    cap_effective;  /* caps we can actually use */
 138        kernel_cap_t    cap_bset;       /* capability bounding set */
 139#ifdef CONFIG_KEYS
 140        unsigned char   jit_keyring;    /* default keyring to attach requested
 141                                         * keys to */
 142        struct key      *thread_keyring; /* keyring private to this thread */
 143        struct key      *request_key_auth; /* assumed request_key authority */
 144        struct thread_group_cred *tgcred; /* thread-group shared credentials */
 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};
 154
 155extern void __put_cred(struct cred *);
 156extern void exit_creds(struct task_struct *);
 157extern int copy_creds(struct task_struct *, unsigned long);
 158extern const struct cred *get_task_cred(struct task_struct *);
 159extern struct cred *cred_alloc_blank(void);
 160extern struct cred *prepare_creds(void);
 161extern struct cred *prepare_exec_creds(void);
 162extern int commit_creds(struct cred *);
 163extern void abort_creds(struct cred *);
 164extern const struct cred *override_creds(const struct cred *);
 165extern void revert_creds(const struct cred *);
 166extern struct cred *prepare_kernel_cred(struct task_struct *);
 167extern int change_create_files_as(struct cred *, struct inode *);
 168extern int set_security_override(struct cred *, u32);
 169extern int set_security_override_from_ctx(struct cred *, const char *);
 170extern int set_create_files_as(struct cred *, struct inode *);
 171extern void __init cred_init(void);
 172
 173/*
 174 * check for validity of credentials
 175 */
 176#ifdef CONFIG_DEBUG_CREDENTIALS
 177extern void __invalid_creds(const struct cred *, const char *, unsigned);
 178extern void __validate_process_creds(struct task_struct *,
 179                                     const char *, unsigned);
 180
 181extern bool creds_are_invalid(const struct cred *cred);
 182
 183static 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)                            \
 191do {                                                    \
 192        __validate_creds((cred), __FILE__, __LINE__);   \
 193} while(0)
 194
 195#define validate_process_creds()                                \
 196do {                                                            \
 197        __validate_process_creds(current, __FILE__, __LINE__);  \
 198} while(0)
 199
 200extern void validate_creds_for_do_exit(struct task_struct *);
 201#else
 202static inline void validate_creds(const struct cred *cred)
 203{
 204}
 205static inline void validate_creds_for_do_exit(struct task_struct *tsk)
 206{
 207}
 208static inline void validate_process_creds(void)
 209{
 210}
 211#endif
 212
 213/**
 214 * get_new_cred - Get a reference on a new set of credentials
 215 * @cred: The new credentials to reference
 216 *
 217 * Get a reference on the specified set of new credentials.  The caller must
 218 * release the reference.
 219 */
 220static inline struct cred *get_new_cred(struct cred *cred)
 221{
 222        atomic_inc(&cred->usage);
 223        return cred;
 224}
 225
 226/**
 227 * get_cred - Get a reference on a set of credentials
 228 * @cred: The credentials to reference
 229 *
 230 * Get a reference on the specified set of credentials.  The caller must
 231 * release the reference.
 232 *
 233 * This is used to deal with a committed set of credentials.  Although the
 234 * pointer is const, this will temporarily discard the const and increment the
 235 * usage count.  The purpose of this is to attempt to catch at compile time the
 236 * accidental alteration of a set of credentials that should be considered
 237 * immutable.
 238 */
 239static inline const struct cred *get_cred(const struct cred *cred)
 240{
 241        struct cred *nonconst_cred = (struct cred *) cred;
 242        validate_creds(cred);
 243        return get_new_cred(nonconst_cred);
 244}
 245
 246/**
 247 * put_cred - Release a reference to a set of credentials
 248 * @cred: The credentials to release
 249 *
 250 * Release a reference to a set of credentials, deleting them when the last ref
 251 * is released.
 252 *
 253 * This takes a const pointer to a set of credentials because the credentials
 254 * on task_struct are attached by const pointers to prevent accidental
 255 * alteration of otherwise immutable credential sets.
 256 */
 257static inline void put_cred(const struct cred *_cred)
 258{
 259        struct cred *cred = (struct cred *) _cred;
 260
 261        validate_creds(cred);
 262        if (atomic_dec_and_test(&(cred)->usage))
 263                __put_cred(cred);
 264}
 265
 266/**
 267 * current_cred - Access the current task's subjective credentials
 268 *
 269 * Access the subjective credentials of the current task.  RCU-safe,
 270 * since nobody else can modify it.
 271 */
 272#define current_cred() \
 273        rcu_dereference_protected(current->cred, 1)
 274
 275/**
 276 * __task_cred - Access a task's objective credentials
 277 * @task: The task to query
 278 *
 279 * Access the objective credentials of a task.  The caller must hold the RCU
 280 * readlock.
 281 *
 282 * The result of this function should not be passed directly to get_cred();
 283 * rather get_task_cred() should be used instead.
 284 */
 285#define __task_cred(task)       \
 286        rcu_dereference((task)->real_cred)
 287
 288/**
 289 * get_current_cred - Get the current task's subjective credentials
 290 *
 291 * Get the subjective credentials of the current task, pinning them so that
 292 * they can't go away.  Accessing the current task's credentials directly is
 293 * not permitted.
 294 */
 295#define get_current_cred()                              \
 296        (get_cred(current_cred()))
 297
 298/**
 299 * get_current_user - Get the current task's user_struct
 300 *
 301 * Get the user record of the current task, pinning it so that it can't go
 302 * away.
 303 */
 304#define get_current_user()                              \
 305({                                                      \
 306        struct user_struct *__u;                        \
 307        const struct cred *__cred;                      \
 308        __cred = current_cred();                        \
 309        __u = get_uid(__cred->user);                    \
 310        __u;                                            \
 311})
 312
 313/**
 314 * get_current_groups - Get the current task's supplementary group list
 315 *
 316 * Get the supplementary group list of the current task, pinning it so that it
 317 * can't go away.
 318 */
 319#define get_current_groups()                            \
 320({                                                      \
 321        struct group_info *__groups;                    \
 322        const struct cred *__cred;                      \
 323        __cred = current_cred();                        \
 324        __groups = get_group_info(__cred->group_info);  \
 325        __groups;                                       \
 326})
 327
 328#define task_cred_xxx(task, xxx)                        \
 329({                                                      \
 330        __typeof__(((struct cred *)NULL)->xxx) ___val;  \
 331        rcu_read_lock();                                \
 332        ___val = __task_cred((task))->xxx;              \
 333        rcu_read_unlock();                              \
 334        ___val;                                         \
 335})
 336
 337#define task_uid(task)          (task_cred_xxx((task), uid))
 338#define task_euid(task)         (task_cred_xxx((task), euid))
 339
 340#define current_cred_xxx(xxx)                   \
 341({                                              \
 342        current_cred()->xxx;                    \
 343})
 344
 345#define current_uid()           (current_cred_xxx(uid))
 346#define current_gid()           (current_cred_xxx(gid))
 347#define current_euid()          (current_cred_xxx(euid))
 348#define current_egid()          (current_cred_xxx(egid))
 349#define current_suid()          (current_cred_xxx(suid))
 350#define current_sgid()          (current_cred_xxx(sgid))
 351#define current_fsuid()         (current_cred_xxx(fsuid))
 352#define current_fsgid()         (current_cred_xxx(fsgid))
 353#define current_cap()           (current_cred_xxx(cap_effective))
 354#define current_user()          (current_cred_xxx(user))
 355#define current_security()      (current_cred_xxx(security))
 356
 357extern struct user_namespace init_user_ns;
 358#ifdef CONFIG_USER_NS
 359#define current_user_ns()       (current_cred_xxx(user_ns))
 360#define task_user_ns(task)      (task_cred_xxx((task), user_ns))
 361#else
 362#define current_user_ns()       (&init_user_ns)
 363#define task_user_ns(task)      (&init_user_ns)
 364#endif
 365
 366
 367#define current_uid_gid(_uid, _gid)             \
 368do {                                            \
 369        const struct cred *__cred;              \
 370        __cred = current_cred();                \
 371        *(_uid) = __cred->uid;                  \
 372        *(_gid) = __cred->gid;                  \
 373} while(0)
 374
 375#define current_euid_egid(_euid, _egid)         \
 376do {                                            \
 377        const struct cred *__cred;              \
 378        __cred = current_cred();                \
 379        *(_euid) = __cred->euid;                \
 380        *(_egid) = __cred->egid;                \
 381} while(0)
 382
 383#define current_fsuid_fsgid(_fsuid, _fsgid)     \
 384do {                                            \
 385        const struct cred *__cred;              \
 386        __cred = current_cred();                \
 387        *(_fsuid) = __cred->fsuid;              \
 388        *(_fsgid) = __cred->fsgid;              \
 389} while(0)
 390
 391#endif /* _LINUX_CRED_H */
 392
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