/* SPDX-License-Identifier: GPL-2.0-or-later */
/* Credentials management - see Documentation/security/credentials.rst
 *
 * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 */

#ifndef _LINUX_CRED_H
#define _LINUX_CRED_H

#include <linux/capability.h>
#include <linux/init.h>
#include <linux/key.h>
#include <linux/atomic.h>
#include <linux/refcount.h>
#include <linux/uidgid.h>
#include <linux/sched.h>
#include <linux/sched/user.h>

struct cred;
struct inode;

extern struct task_struct init_task;

/*
 * COW Supplementary groups list
 */
struct group_info {
        refcount_t      usage;
        int             ngroups;
        kgid_t          gid[];
} __randomize_layout;

/**
 * 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)
{
        refcount_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 (refcount_dec_and_test(&(group_info)->usage))        \
                groups_free(group_info);                \
} while (0)

#ifdef CONFIG_MULTIUSER
extern struct group_info *groups_alloc(int);
extern void groups_free(struct group_info *);

extern int in_group_p(kgid_t);
extern int in_egroup_p(kgid_t);
extern int groups_search(const struct group_info *, kgid_t);

extern int set_current_groups(struct group_info *);
extern void set_groups(struct cred *, struct group_info *);
extern bool may_setgroups(void);
extern void groups_sort(struct group_info *);
#else
static inline void groups_free(struct group_info *group_info)
{
}

static inline int in_group_p(kgid_t grp)
{
        return 1;
}
static inline int in_egroup_p(kgid_t grp)
{
        return 1;
}
static inline int groups_search(const struct group_info *group_info, kgid_t grp)
{
        return 1;
}
#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_long_t   usage;
        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 */
        kernel_cap_t    cap_ambient;    /* Ambient capability set */
#ifdef CONFIG_KEYS
        unsigned char   jit_keyring;    /* default keyring to attach requested
                                         * keys to */
        struct key      *session_keyring; /* keyring inherited over fork */
        struct key      *process_keyring; /* keyring private to this process */
        struct key      *thread_keyring; /* keyring private to this thread */
        struct key      *request_key_auth; /* assumed request_key authority */
#endif
#ifdef CONFIG_SECURITY
        void            *security;      /* 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 ucounts *ucounts;
        struct group_info *group_info;  /* supplementary groups for euid/fsgid */
        /* RCU deletion */
        union {
                int non_rcu;                    /* Can we skip RCU deletion? */
                struct rcu_head rcu;            /* RCU deletion hook */
        };
} __randomize_layout;

extern void __put_cred(struct cred *);
extern void exit_creds(struct task_struct *);
extern int copy_creds(struct task_struct *, u64);
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 struct cred *prepare_kernel_cred(struct task_struct *);
static inline const struct cred *kernel_cred(void)
{
        /* shut up sparse */
        return rcu_dereference_raw(init_task.cred);
}
extern int set_security_override(struct cred *, u32);
extern int set_create_files_as(struct cred *, struct inode *);
extern int cred_fscmp(const struct cred *, const struct cred *);
extern void __init cred_init(void);
extern int set_cred_ucounts(struct cred *);

static inline bool cap_ambient_invariant_ok(const struct cred *cred)
{
        return cap_issubset(cred->cap_ambient,
                            cap_intersect(cred->cap_permitted,
                                          cred->cap_inheritable));
}

static inline const struct cred *override_creds(const struct cred *override_cred)
{
        return rcu_replace_pointer(current->cred, override_cred, 1);
}

static inline const struct cred *revert_creds(const struct cred *revert_cred)
{
        return rcu_replace_pointer(current->cred, revert_cred, 1);
}

DEFINE_CLASS(override_creds,
             const struct cred *,
             revert_creds(_T),
             override_creds(override_cred), const struct cred *override_cred)

#define scoped_with_creds(cred) \
        scoped_class(override_creds, __UNIQUE_ID(label), cred)

#define scoped_with_kernel_creds() scoped_with_creds(kernel_cred())

/**
 * get_cred_many - Get references on a set of credentials
 * @cred: The credentials to reference
 * @nr: Number of references to acquire
 *
 * Get references on the specified set of credentials.  The caller must release
 * all acquired reference.  If %NULL is passed, it is returned with no action.
 *
 * 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_many(const struct cred *cred, int nr)
{
        struct cred *nonconst_cred = (struct cred *) cred;
        if (!cred)
                return cred;
        nonconst_cred->non_rcu = 0;
        atomic_long_add(nr, &nonconst_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.  If %NULL is passed, it is returned with no action.
 *
 * This is used to deal with a committed set of credentials.
 */
static inline const struct cred *get_cred(const struct cred *cred)
{
        return get_cred_many(cred, 1);
}

static inline const struct cred *get_cred_rcu(const struct cred *cred)
{
        struct cred *nonconst_cred = (struct cred *) cred;
        if (!cred)
                return NULL;
        if (!atomic_long_inc_not_zero(&nonconst_cred->usage))
                return NULL;
        nonconst_cred->non_rcu = 0;
        return cred;
}

/**
 * put_cred - Release a reference to a set of credentials
 * @cred: The credentials to release
 * @nr: Number of references to release
 *
 * Release a reference to a set of credentials, deleting them when the last ref
 * is released.  If %NULL is passed, nothing is done.
 *
 * 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_many(const struct cred *_cred, int nr)
{
        struct cred *cred = (struct cred *) _cred;

        if (cred) {
                if (atomic_long_sub_and_test(nr, &cred->usage))
                        __put_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.  If %NULL is passed, nothing is done.
 */
static inline void put_cred(const struct cred *cred)
{
        put_cred_many(cred, 1);
}

DEFINE_CLASS(prepare_creds,
              struct cred *,
              if (_T) put_cred(_T),
              prepare_creds(), void)

DEFINE_FREE(put_cred, struct cred *, if (!IS_ERR_OR_NULL(_T)) put_cred(_T))

/**
 * current_cred - Access the current task's subjective credentials
 *
 * Access the subjective credentials of the current task.  RCU-safe,
 * since nobody else can modify it.
 */
#define current_cred() \
        rcu_dereference_protected(current->cred, 1)

/**
 * current_real_cred - Access the current task's objective credentials
 *
 * Access the objective credentials of the current task.  RCU-safe,
 * since nobody else can modify it.
 */
#define current_real_cred() \
        rcu_dereference_protected(current->real_cred, 1)

/**
 * __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 result of this function should not be passed directly to get_cred();
 * rather get_task_cred() should be used instead.
 */
#define __task_cred(task)       \
        rcu_dereference((task)->real_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;                        \
        const struct cred *__cred;                      \
        __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;                    \
        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 task_ucounts(task)      (task_cred_xxx((task), ucounts))

#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_ucounts()       (current_cred_xxx(ucounts))

extern struct user_namespace init_user_ns;
#ifdef CONFIG_USER_NS
#define current_user_ns()       (current_cred_xxx(user_ns))
#else
static inline struct user_namespace *current_user_ns(void)
{
        return &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 */