/* Credentials management - see Documentation/credentials.txt
 *
 * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 *
 * 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 <asm/atomic.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(gid_t)))

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

/**
 * get_group_info - Get a reference to a group info structure
 * @group_info: The group info to reference
 *
 * This gets a reference to a set of supplementary groups.
 *
 * If the caller is accessing a task's credentials, they must hold the RCU read
 * lock when reading.
 */
static inline struct group_info *get_group_info(struct group_info *gi)
{
        atomic_inc(&gi->usage);
        return gi;
}

/**
 * put_group_info - Release a reference to a group info structure
 * @group_info: The group info to release
 */
#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 *, gid_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(gid_t);
extern int in_egroup_p(gid_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      *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;
        uid_t           uid;            /* real UID of the task */
        gid_t           gid;            /* real GID of the task */
        uid_t           suid;           /* saved UID of the task */
        gid_t           sgid;           /* saved GID of the task */
        uid_t           euid;           /* effective UID of the task */
        gid_t           egid;           /* effective GID of the task */
        uid_t           fsuid;          /* UID for VFS ops */
        gid_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 group_info *group_info;  /* supplementary groups for euid/fsgid */
        struct rcu_head rcu;            /* RCU deletion hook */
};

extern void __put_cred(struct cred *);
extern int copy_creds(struct task_struct *, unsigned long);
extern struct cred *prepare_creds(void);
extern struct cred *prepare_exec_creds(void);
extern struct cred *prepare_usermodehelper_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);

/**
 * get_new_cred - Get a reference on a new set of credentials
 * @cred: The new credentials to reference
 *
 * Get a reference on the specified set of new credentials.  The caller must
 * release the reference.
 */
static inline struct cred *get_new_cred(struct cred *cred)
{
        atomic_inc(&cred->usage);
        return cred;
}

/**
 * get_cred - Get a reference on a set of credentials
 * @cred: The credentials to reference
 *
 * Get a reference on the specified set of credentials.  The caller must
 * release the reference.
 *
 * This is used to deal with a committed set of credentials.  Although the
 * pointer is const, this will temporarily discard the const and increment the
 * usage count.  The purpose of this is to attempt to catch at compile time the
 * accidental alteration of a set of credentials that should be considered
 * immutable.
 */
static inline const struct cred *get_cred(const struct cred *cred)
{
        return get_new_cred((struct cred *) cred);
}

/**
 * put_cred - Release a reference to a set of credentials
 * @cred: The credentials to release
 *
 * Release a reference to a set of credentials, deleting them when the last ref
 * is released.
 *
 * This takes a const pointer to a set of credentials because the credentials
 * on task_struct are attached by const pointers to prevent accidental
 * alteration of otherwise immutable credential sets.
 */
static inline void put_cred(const struct cred *_cred)
{
        struct cred *cred = (struct cred *) _cred;

        BUG_ON(atomic_read(&(cred)->usage) <= 0);
        if (atomic_dec_and_test(&(cred)->usage))
                __put_cred(cred);
}

/**
 * current_cred - Access the current task's subjective credentials
 *
 * Access the subjective credentials of the current task.
 */
#define current_cred() \
        (current->cred)

/**
 * __task_cred - Access a task's objective credentials
 * @task: The task to query
 *
 * Access the objective credentials of a task.  The caller must hold the RCU
 * readlock.
 *
 * The caller must make sure task doesn't go away, either by holding a ref on
 * task or by holding tasklist_lock to prevent it from being unlinked.
 */
#define __task_cred(task) \
        ((const struct cred *)(rcu_dereference((task)->real_cred)))

/**
 * get_task_cred - Get another task's objective credentials
 * @task: The task to query
 *
 * Get the objective credentials of a task, pinning them so that they can't go
 * away.  Accessing a task's credentials directly is not permitted.
 *
 * The caller must make sure task doesn't go away, either by holding a ref on
 * task or by holding tasklist_lock to prevent it from being unlinked.
 */
#define get_task_cred(task)                             \
({                                                      \
        struct cred *__cred;                            \
        rcu_read_lock();                                \
        __cred = (struct cred *) __task_cred((task));   \
        get_cred(__cred);                               \
        rcu_read_unlock();                              \
        __cred;                                         \
})

/**
 * get_current_cred - Get the current task's subjective credentials
 *
 * Get the subjective credentials of the current task, pinning them so that
 * they can't go away.  Accessing the current task's credentials directly is
 * not permitted.
 */
#define get_current_cred()                              \
        (get_cred(current_cred()))

/**
 * get_current_user - Get the current task's user_struct
 *
 * Get the user record of the current task, pinning it so that it can't go
 * away.
 */
#define get_current_user()                              \
({                                                      \
        struct user_struct *__u;                        \
        struct cred *__cred;                            \
        __cred = (struct cred *) current_cred();        \
        __u = get_uid(__cred->user);                    \
        __u;                                            \
})

/**
 * get_current_groups - Get the current task's supplementary group list
 *
 * Get the supplementary group list of the current task, pinning it so that it
 * can't go away.
 */
#define get_current_groups()                            \
({                                                      \
        struct group_info *__groups;                    \
        struct cred *__cred;                            \
        __cred = (struct 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_user_ns()       (current_cred_xxx(user)->user_ns)
#define current_security()      (current_cred_xxx(security))

#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 */