cred.h

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/* Credentials management - see Documentation/security/credentials.txt
 *
 * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells ([email protected])
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public Licence
 * as published by the Free Software Foundation; either version
 * 2 of the Licence, or (at your option) any later version.
 */

#ifndef _LINUX_CRED_H
#define _LINUX_CRED_H

#include <linux/capability.h>
#include <linux/init.h>
#include <linux/key.h>
#include <linux/selinux.h>
#include <linux/atomic.h>
#include <linux/uidgid.h>

struct user_struct;
struct cred;
struct inode;

/*
 * COW Supplementary groups list
 */
#define NGROUPS_SMALL       32
#define NGROUPS_PER_BLOCK   ((unsigned int)(PAGE_SIZE / sizeof(kgid_t)))

struct group_info {
    atomic_t    usage;
    int     ngroups;
    int     nblocks;
    kgid_t      small_block[NGROUPS_SMALL];
    kgid_t      *blocks[0];
};

static inline struct group_info *get_group_info(struct group_info *gi)
{
    atomic_inc(&gi->usage);
    return gi;
}

#define put_group_info(group_info)          \
do {                            \
    if (atomic_dec_and_test(&(group_info)->usage))  \
        groups_free(group_info);        \
} while (0)

extern struct group_info *groups_alloc(int);
extern struct group_info init_groups;
extern void groups_free(struct group_info *);
extern int set_current_groups(struct group_info *);
extern int set_groups(struct cred *, struct group_info *);
extern int groups_search(const struct group_info *, kgid_t);

/* access the groups "array" with this macro */
#define GROUP_AT(gi, i) \
    ((gi)->blocks[(i) / NGROUPS_PER_BLOCK][(i) % NGROUPS_PER_BLOCK])

extern int in_group_p(kgid_t);
extern int in_egroup_p(kgid_t);

/*
 * The common credentials for a thread group
 * - shared by CLONE_THREAD
 */
#ifdef CONFIG_KEYS
struct thread_group_cred {
    atomic_t    usage;
    pid_t       tgid;           /* thread group process ID */
    spinlock_t  lock;
    struct key __rcu *session_keyring;  /* keyring inherited over fork */
    struct key  *process_keyring;   /* keyring private to this process */
    struct rcu_head rcu;            /* RCU deletion hook */
};
#endif

/*
 * The security context of a task
 *
 * The parts of the context break down into two categories:
 *
 *  (1) The objective context of a task.  These parts are used when some other
 *  task is attempting to affect this one.
 *
 *  (2) The subjective context.  These details are used when the task is acting
 *  upon another object, be that a file, a task, a key or whatever.
 *
 * Note that some members of this structure belong to both categories - the
 * LSM security pointer for instance.
 *
 * A task has two security pointers.  task->real_cred points to the objective
 * context that defines that task's actual details.  The objective part of this
 * context is used whenever that task is acted upon.
 *
 * task->cred points to the subjective context that defines the details of how
 * that task is going to act upon another object.  This may be overridden
 * temporarily to point to another security context, but normally points to the
 * same context as task->real_cred.
 */
struct cred {
    atomic_t    usage;
#ifdef CONFIG_DEBUG_CREDENTIALS
    atomic_t    subscribers;    /* number of processes subscribed */
    void        *put_addr;
    unsigned    magic;
#define CRED_MAGIC  0x43736564
#define CRED_MAGIC_DEAD 0x44656144
#endif
    kuid_t      uid;        /* real UID of the task */
    kgid_t      gid;        /* real GID of the task */
    kuid_t      suid;       /* saved UID of the task */
    kgid_t      sgid;       /* saved GID of the task */
    kuid_t      euid;       /* effective UID of the task */
    kgid_t      egid;       /* effective GID of the task */
    kuid_t      fsuid;      /* UID for VFS ops */
    kgid_t      fsgid;      /* GID for VFS ops */
    unsigned    securebits; /* SUID-less security management */
    kernel_cap_t    cap_inheritable; /* caps our children can inherit */
    kernel_cap_t    cap_permitted;  /* caps we're permitted */
    kernel_cap_t    cap_effective;  /* caps we can actually use */
    kernel_cap_t    cap_bset;   /* capability bounding set */
#ifdef CONFIG_KEYS
    unsigned char   jit_keyring;    /* default keyring to attach requested
                     * keys to */
    struct key  *thread_keyring; /* keyring private to this thread */
    struct key  *request_key_auth; /* assumed request_key authority */
    struct thread_group_cred *tgcred; /* thread-group shared credentials */
#endif
#ifdef CONFIG_SECURITY
    void        *security;  /* subjective LSM security */
#endif
    struct user_struct *user;   /* real user ID subscription */
    struct user_namespace *user_ns; /* user_ns the caps and keyrings are relative to. */
    struct group_info *group_info;  /* supplementary groups for euid/fsgid */
    struct rcu_head rcu;        /* RCU deletion hook */
};

extern void __put_cred(struct cred *);
extern void exit_creds(struct task_struct *);
extern int copy_creds(struct task_struct *, unsigned long);
extern const struct cred *get_task_cred(struct task_struct *);
extern struct cred *cred_alloc_blank(void);
extern struct cred *prepare_creds(void);
extern struct cred *prepare_exec_creds(void);
extern int commit_creds(struct cred *);
extern void abort_creds(struct cred *);
extern const struct cred *override_creds(const struct cred *);
extern void revert_creds(const struct cred *);
extern struct cred *prepare_kernel_cred(struct task_struct *);
extern int change_create_files_as(struct cred *, struct inode *);
extern int set_security_override(struct cred *, u32);
extern int set_security_override_from_ctx(struct cred *, const char *);
extern int set_create_files_as(struct cred *, struct inode *);
extern void __init cred_init(void);

/*
 * check for validity of credentials
 */
#ifdef CONFIG_DEBUG_CREDENTIALS
extern void __invalid_creds(const struct cred *, const char *, unsigned);
extern void __validate_process_creds(struct task_struct *,
                     const char *, unsigned);

extern bool creds_are_invalid(const struct cred *cred);

static inline void __validate_creds(const struct cred *cred,
                    const char *file, unsigned line)
{
    if (unlikely(creds_are_invalid(cred)))
        __invalid_creds(cred, file, line);
}

#define validate_creds(cred)                \
do {                            \
    __validate_creds((cred), __FILE__, __LINE__);   \
} while(0)

#define validate_process_creds()                \
do {                                \
    __validate_process_creds(current, __FILE__, __LINE__);  \
} while(0)

extern void validate_creds_for_do_exit(struct task_struct *);
#else
static inline void validate_creds(const struct cred *cred)
{
}
static inline void validate_creds_for_do_exit(struct task_struct *tsk)
{
}
static inline void validate_process_creds(void)
{
}
#endif

static inline struct cred *get_new_cred(struct cred *cred)
{
    atomic_inc(&cred->usage);
    return cred;
}

static inline const struct cred *get_cred(const struct cred *cred)
{
    struct cred *nonconst_cred = (struct cred *) cred;
    validate_creds(cred);
    return get_new_cred(nonconst_cred);
}

static inline void put_cred(const struct cred *_cred)
{
    struct cred *cred = (struct cred *) _cred;

    validate_creds(cred);
    if (atomic_dec_and_test(&(cred)->usage))
        __put_cred(cred);
}

#define current_cred() \
    rcu_dereference_protected(current->cred, 1)

#define __task_cred(task)   \
    rcu_dereference((task)->real_cred)

#define get_current_cred()              \
    (get_cred(current_cred()))

#define get_current_user()              \
({                          \
    struct user_struct *__u;            \
    const struct cred *__cred;          \
    __cred = current_cred();            \
    __u = get_uid(__cred->user);            \
    __u;                        \
})

#define get_current_groups()                \
({                          \
    struct group_info *__groups;            \
    const struct cred *__cred;          \
    __cred = current_cred();            \
    __groups = get_group_info(__cred->group_info);  \
    __groups;                   \
})

#define task_cred_xxx(task, xxx)            \
({                          \
    __typeof__(((struct cred *)NULL)->xxx) ___val;  \
    rcu_read_lock();                \
    ___val = __task_cred((task))->xxx;      \
    rcu_read_unlock();              \
    ___val;                     \
})

#define task_uid(task)      (task_cred_xxx((task), uid))
#define task_euid(task)     (task_cred_xxx((task), euid))

#define current_cred_xxx(xxx)           \
({                      \
    current_cred()->xxx;            \
})

#define current_uid()       (current_cred_xxx(uid))
#define current_gid()       (current_cred_xxx(gid))
#define current_euid()      (current_cred_xxx(euid))
#define current_egid()      (current_cred_xxx(egid))
#define current_suid()      (current_cred_xxx(suid))
#define current_sgid()      (current_cred_xxx(sgid))
#define current_fsuid()     (current_cred_xxx(fsuid))
#define current_fsgid()     (current_cred_xxx(fsgid))
#define current_cap()       (current_cred_xxx(cap_effective))
#define current_user()      (current_cred_xxx(user))
#define current_security()  (current_cred_xxx(security))

extern struct user_namespace init_user_ns;
#ifdef CONFIG_USER_NS
#define current_user_ns()   (current_cred_xxx(user_ns))
#define task_user_ns(task)  (task_cred_xxx((task), user_ns))
#else
#define current_user_ns()   (&init_user_ns)
#define task_user_ns(task)  (&init_user_ns)
#endif


#define current_uid_gid(_uid, _gid)     \
do {                        \
    const struct cred *__cred;      \
    __cred = current_cred();        \
    *(_uid) = __cred->uid;          \
    *(_gid) = __cred->gid;          \
} while(0)

#define current_euid_egid(_euid, _egid)     \
do {                        \
    const struct cred *__cred;      \
    __cred = current_cred();        \
    *(_euid) = __cred->euid;        \
    *(_egid) = __cred->egid;        \
} while(0)

#define current_fsuid_fsgid(_fsuid, _fsgid) \
do {                        \
    const struct cred *__cred;      \
    __cred = current_cred();        \
    *(_fsuid) = __cred->fsuid;      \
    *(_fsgid) = __cred->fsgid;      \
} while(0)

#endif /* _LINUX_CRED_H */