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 security context of a task
  81 *
  82 * The parts of the context break down into two categories:
  83 *
  84 *  (1) The objective context of a task.  These parts are used when some other
  85 *      task is attempting to affect this one.
  86 *
  87 *  (2) The subjective context.  These details are used when the task is acting
  88 *      upon another object, be that a file, a task, a key or whatever.
  89 *
  90 * Note that some members of this structure belong to both categories - the
  91 * LSM security pointer for instance.
  92 *
  93 * A task has two security pointers.  task->real_cred points to the objective
  94 * context that defines that task's actual details.  The objective part of this
  95 * context is used whenever that task is acted upon.
  96 *
  97 * task->cred points to the subjective context that defines the details of how
  98 * that task is going to act upon another object.  This may be overridden
  99 * temporarily to point to another security context, but normally points to the
 100 * same context as task->real_cred.
 101 */
 102struct cred {
 103        atomic_t        usage;
 104#ifdef CONFIG_DEBUG_CREDENTIALS
 105        atomic_t        subscribers;    /* number of processes subscribed */
 106        void            *put_addr;
 107        unsigned        magic;
 108#define CRED_MAGIC      0x43736564
 109#define CRED_MAGIC_DEAD 0x44656144
 110#endif
 111        kuid_t          uid;            /* real UID of the task */
 112        kgid_t          gid;            /* real GID of the task */
 113        kuid_t          suid;           /* saved UID of the task */
 114        kgid_t          sgid;           /* saved GID of the task */
 115        kuid_t          euid;           /* effective UID of the task */
 116        kgid_t          egid;           /* effective GID of the task */
 117        kuid_t          fsuid;          /* UID for VFS ops */
 118        kgid_t          fsgid;          /* GID for VFS ops */
 119        unsigned        securebits;     /* SUID-less security management */
 120        kernel_cap_t    cap_inheritable; /* caps our children can inherit */
 121        kernel_cap_t    cap_permitted;  /* caps we're permitted */
 122        kernel_cap_t    cap_effective;  /* caps we can actually use */
 123        kernel_cap_t    cap_bset;       /* capability bounding set */
 124#ifdef CONFIG_KEYS
 125        unsigned char   jit_keyring;    /* default keyring to attach requested
 126                                         * keys to */
 127        struct key __rcu *session_keyring; /* keyring inherited over fork */
 128        struct key      *process_keyring; /* keyring private to this process */
 129        struct key      *thread_keyring; /* keyring private to this thread */
 130        struct key      *request_key_auth; /* assumed request_key authority */
 131#endif
 132#ifdef CONFIG_SECURITY
 133        void            *security;      /* subjective LSM security */
 134#endif
 135        struct user_struct *user;       /* real user ID subscription */
 136        struct user_namespace *user_ns; /* user_ns the caps and keyrings are relative to. */
 137        struct group_info *group_info;  /* supplementary groups for euid/fsgid */
 138        struct rcu_head rcu;            /* RCU deletion hook */
 139};
 140
 141extern void __put_cred(struct cred *);
 142extern void exit_creds(struct task_struct *);
 143extern int copy_creds(struct task_struct *, unsigned long);
 144extern const struct cred *get_task_cred(struct task_struct *);
 145extern struct cred *cred_alloc_blank(void);
 146extern struct cred *prepare_creds(void);
 147extern struct cred *prepare_exec_creds(void);
 148extern int commit_creds(struct cred *);
 149extern void abort_creds(struct cred *);
 150extern const struct cred *override_creds(const struct cred *);
 151extern void revert_creds(const struct cred *);
 152extern struct cred *prepare_kernel_cred(struct task_struct *);
 153extern int change_create_files_as(struct cred *, struct inode *);
 154extern int set_security_override(struct cred *, u32);
 155extern int set_security_override_from_ctx(struct cred *, const char *);
 156extern int set_create_files_as(struct cred *, struct inode *);
 157extern void __init cred_init(void);
 158
 159/*
 160 * check for validity of credentials
 161 */
 162#ifdef CONFIG_DEBUG_CREDENTIALS
 163extern void __invalid_creds(const struct cred *, const char *, unsigned);
 164extern void __validate_process_creds(struct task_struct *,
 165                                     const char *, unsigned);
 166
 167extern bool creds_are_invalid(const struct cred *cred);
 168
 169static inline void __validate_creds(const struct cred *cred,
 170                                    const char *file, unsigned line)
 171{
 172        if (unlikely(creds_are_invalid(cred)))
 173                __invalid_creds(cred, file, line);
 174}
 175
 176#define validate_creds(cred)                            \
 177do {                                                    \
 178        __validate_creds((cred), __FILE__, __LINE__);   \
 179} while(0)
 180
 181#define validate_process_creds()                                \
 182do {                                                            \
 183        __validate_process_creds(current, __FILE__, __LINE__);  \
 184} while(0)
 185
 186extern void validate_creds_for_do_exit(struct task_struct *);
 187#else
 188static inline void validate_creds(const struct cred *cred)
 189{
 190}
 191static inline void validate_creds_for_do_exit(struct task_struct *tsk)
 192{
 193}
 194static inline void validate_process_creds(void)
 195{
 196}
 197#endif
 198
 199/**
 200 * get_new_cred - Get a reference on a new set of credentials
 201 * @cred: The new credentials to reference
 202 *
 203 * Get a reference on the specified set of new credentials.  The caller must
 204 * release the reference.
 205 */
 206static inline struct cred *get_new_cred(struct cred *cred)
 207{
 208        atomic_inc(&cred->usage);
 209        return cred;
 210}
 211
 212/**
 213 * get_cred - Get a reference on a set of credentials
 214 * @cred: The credentials to reference
 215 *
 216 * Get a reference on the specified set of credentials.  The caller must
 217 * release the reference.
 218 *
 219 * This is used to deal with a committed set of credentials.  Although the
 220 * pointer is const, this will temporarily discard the const and increment the
 221 * usage count.  The purpose of this is to attempt to catch at compile time the
 222 * accidental alteration of a set of credentials that should be considered
 223 * immutable.
 224 */
 225static inline const struct cred *get_cred(const struct cred *cred)
 226{
 227        struct cred *nonconst_cred = (struct cred *) cred;
 228        validate_creds(cred);
 229        return get_new_cred(nonconst_cred);
 230}
 231
 232/**
 233 * put_cred - Release a reference to a set of credentials
 234 * @cred: The credentials to release
 235 *
 236 * Release a reference to a set of credentials, deleting them when the last ref
 237 * is released.
 238 *
 239 * This takes a const pointer to a set of credentials because the credentials
 240 * on task_struct are attached by const pointers to prevent accidental
 241 * alteration of otherwise immutable credential sets.
 242 */
 243static inline void put_cred(const struct cred *_cred)
 244{
 245        struct cred *cred = (struct cred *) _cred;
 246
 247        validate_creds(cred);
 248        if (atomic_dec_and_test(&(cred)->usage))
 249                __put_cred(cred);
 250}
 251
 252/**
 253 * current_cred - Access the current task's subjective credentials
 254 *
 255 * Access the subjective credentials of the current task.  RCU-safe,
 256 * since nobody else can modify it.
 257 */
 258#define current_cred() \
 259        rcu_dereference_protected(current->cred, 1)
 260
 261/**
 262 * __task_cred - Access a task's objective credentials
 263 * @task: The task to query
 264 *
 265 * Access the objective credentials of a task.  The caller must hold the RCU
 266 * readlock.
 267 *
 268 * The result of this function should not be passed directly to get_cred();
 269 * rather get_task_cred() should be used instead.
 270 */
 271#define __task_cred(task)       \
 272        rcu_dereference((task)->real_cred)
 273
 274/**
 275 * get_current_cred - Get the current task's subjective credentials
 276 *
 277 * Get the subjective credentials of the current task, pinning them so that
 278 * they can't go away.  Accessing the current task's credentials directly is
 279 * not permitted.
 280 */
 281#define get_current_cred()                              \
 282        (get_cred(current_cred()))
 283
 284/**
 285 * get_current_user - Get the current task's user_struct
 286 *
 287 * Get the user record of the current task, pinning it so that it can't go
 288 * away.
 289 */
 290#define get_current_user()                              \
 291({                                                      \
 292        struct user_struct *__u;                        \
 293        const struct cred *__cred;                      \
 294        __cred = current_cred();                        \
 295        __u = get_uid(__cred->user);                    \
 296        __u;                                            \
 297})
 298
 299/**
 300 * get_current_groups - Get the current task's supplementary group list
 301 *
 302 * Get the supplementary group list of the current task, pinning it so that it
 303 * can't go away.
 304 */
 305#define get_current_groups()                            \
 306({                                                      \
 307        struct group_info *__groups;                    \
 308        const struct cred *__cred;                      \
 309        __cred = current_cred();                        \
 310        __groups = get_group_info(__cred->group_info);  \
 311        __groups;                                       \
 312})
 313
 314#define task_cred_xxx(task, xxx)                        \
 315({                                                      \
 316        __typeof__(((struct cred *)NULL)->xxx) ___val;  \
 317        rcu_read_lock();                                \
 318        ___val = __task_cred((task))->xxx;              \
 319        rcu_read_unlock();                              \
 320        ___val;                                         \
 321})
 322
 323#define task_uid(task)          (task_cred_xxx((task), uid))
 324#define task_euid(task)         (task_cred_xxx((task), euid))
 325
 326#define current_cred_xxx(xxx)                   \
 327({                                              \
 328        current_cred()->xxx;                    \
 329})
 330
 331#define current_uid()           (current_cred_xxx(uid))
 332#define current_gid()           (current_cred_xxx(gid))
 333#define current_euid()          (current_cred_xxx(euid))
 334#define current_egid()          (current_cred_xxx(egid))
 335#define current_suid()          (current_cred_xxx(suid))
 336#define current_sgid()          (current_cred_xxx(sgid))
 337#define current_fsuid()         (current_cred_xxx(fsuid))
 338#define current_fsgid()         (current_cred_xxx(fsgid))
 339#define current_cap()           (current_cred_xxx(cap_effective))
 340#define current_user()          (current_cred_xxx(user))
 341#define current_security()      (current_cred_xxx(security))
 342
 343extern struct user_namespace init_user_ns;
 344#ifdef CONFIG_USER_NS
 345#define current_user_ns()       (current_cred_xxx(user_ns))
 346#else
 347#define current_user_ns()       (&init_user_ns)
 348#endif
 349
 350
 351#define current_uid_gid(_uid, _gid)             \
 352do {                                            \
 353        const struct cred *__cred;              \
 354        __cred = current_cred();                \
 355        *(_uid) = __cred->uid;                  \
 356        *(_gid) = __cred->gid;                  \
 357} while(0)
 358
 359#define current_euid_egid(_euid, _egid)         \
 360do {                                            \
 361        const struct cred *__cred;              \
 362        __cred = current_cred();                \
 363        *(_euid) = __cred->euid;                \
 364        *(_egid) = __cred->egid;                \
 365} while(0)
 366
 367#define current_fsuid_fsgid(_fsuid, _fsgid)     \
 368do {                                            \
 369        const struct cred *__cred;              \
 370        __cred = current_cred();                \
 371        *(_fsuid) = __cred->fsuid;              \
 372        *(_fsgid) = __cred->fsgid;              \
 373} while(0)
 374
 375#endif /* _LINUX_CRED_H */
 376
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