/* keyctl.c: userspace keyctl operations
 *
 * Copyright (C) 2004-5 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 License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 */

#include <linux/module.h>
#include <linux/init.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/syscalls.h>
#include <linux/keyctl.h>
#include <linux/fs.h>
#include <linux/capability.h>
#include <linux/string.h>
#include <linux/err.h>
#include <linux/vmalloc.h>
#include <linux/security.h>
#include <asm/uaccess.h>
#include "internal.h"

static int key_get_type_from_user(char *type,
                                  const char __user *_type,
                                  unsigned len)
{
        int ret;

        ret = strncpy_from_user(type, _type, len);

        if (ret < 0)
                return -EFAULT;

        if (ret == 0 || ret >= len)
                return -EINVAL;

        if (type[0] == '.')
                return -EPERM;

        type[len - 1] = '\0';

        return 0;
}

/*****************************************************************************/
/*
 * extract the description of a new key from userspace and either add it as a
 * new key to the specified keyring or update a matching key in that keyring
 * - the keyring must be writable
 * - returns the new key's serial number
 * - implements add_key()
 */
SYSCALL_DEFINE5(add_key, const char __user *, _type,
                const char __user *, _description,
                const void __user *, _payload,
                size_t, plen,
                key_serial_t, ringid)
{
        key_ref_t keyring_ref, key_ref;
        char type[32], *description;
        void *payload;
        long ret;
        bool vm;

        ret = -EINVAL;
        if (plen > 1024 * 1024 - 1)
                goto error;

        /* draw all the data into kernel space */
        ret = key_get_type_from_user(type, _type, sizeof(type));
        if (ret < 0)
                goto error;

        description = strndup_user(_description, PAGE_SIZE);
        if (IS_ERR(description)) {
                ret = PTR_ERR(description);
                goto error;
        }

        /* pull the payload in if one was supplied */
        payload = NULL;

        vm = false;
        if (_payload) {
                ret = -ENOMEM;
                payload = kmalloc(plen, GFP_KERNEL);
                if (!payload) {
                        if (plen <= PAGE_SIZE)
                                goto error2;
                        vm = true;
                        payload = vmalloc(plen);
                        if (!payload)
                                goto error2;
                }

                ret = -EFAULT;
                if (copy_from_user(payload, _payload, plen) != 0)
                        goto error3;
        }

        /* find the target keyring (which must be writable) */
        keyring_ref = lookup_user_key(ringid, 1, 0, KEY_WRITE);
        if (IS_ERR(keyring_ref)) {
                ret = PTR_ERR(keyring_ref);
                goto error3;
        }

        /* create or update the requested key and add it to the target
         * keyring */
        key_ref = key_create_or_update(keyring_ref, type, description,
                                       payload, plen, KEY_PERM_UNDEF,
                                       KEY_ALLOC_IN_QUOTA);
        if (!IS_ERR(key_ref)) {
                ret = key_ref_to_ptr(key_ref)->serial;
                key_ref_put(key_ref);
        }
        else {
                ret = PTR_ERR(key_ref);
        }

        key_ref_put(keyring_ref);
 error3:
        if (!vm)
                kfree(payload);
        else
                vfree(payload);
 error2:
        kfree(description);
 error:
        return ret;

} /* end sys_add_key() */

/*****************************************************************************/
/*
 * search the process keyrings for a matching key
 * - nested keyrings may also be searched if they have Search permission
 * - if a key is found, it will be attached to the destination keyring if
 *   there's one specified
 * - /sbin/request-key will be invoked if _callout_info is non-NULL
 *   - the _callout_info string will be passed to /sbin/request-key
 *   - if the _callout_info string is empty, it will be rendered as "-"
 * - implements request_key()
 */
SYSCALL_DEFINE4(request_key, const char __user *, _type,
                const char __user *, _description,
                const char __user *, _callout_info,
                key_serial_t, destringid)
{
        struct key_type *ktype;
        struct key *key;
        key_ref_t dest_ref;
        size_t callout_len;
        char type[32], *description, *callout_info;
        long ret;

        /* pull the type into kernel space */
        ret = key_get_type_from_user(type, _type, sizeof(type));
        if (ret < 0)
                goto error;

        /* pull the description into kernel space */
        description = strndup_user(_description, PAGE_SIZE);
        if (IS_ERR(description)) {
                ret = PTR_ERR(description);
                goto error;
        }

        /* pull the callout info into kernel space */
        callout_info = NULL;
        callout_len = 0;
        if (_callout_info) {
                callout_info = strndup_user(_callout_info, PAGE_SIZE);
                if (IS_ERR(callout_info)) {
                        ret = PTR_ERR(callout_info);
                        goto error2;
                }
                callout_len = strlen(callout_info);
        }

        /* get the destination keyring if specified */
        dest_ref = NULL;
        if (destringid) {
                dest_ref = lookup_user_key(destringid, 1, 0, KEY_WRITE);
                if (IS_ERR(dest_ref)) {
                        ret = PTR_ERR(dest_ref);
                        goto error3;
                }
        }

        /* find the key type */
        ktype = key_type_lookup(type);
        if (IS_ERR(ktype)) {
                ret = PTR_ERR(ktype);
                goto error4;
        }

        /* do the search */
        key = request_key_and_link(ktype, description, callout_info,
                                   callout_len, NULL, key_ref_to_ptr(dest_ref),
                                   KEY_ALLOC_IN_QUOTA);
        if (IS_ERR(key)) {
                ret = PTR_ERR(key);
                goto error5;
        }

        ret = key->serial;

        key_put(key);
 error5:
        key_type_put(ktype);
 error4:
        key_ref_put(dest_ref);
 error3:
        kfree(callout_info);
 error2:
        kfree(description);
 error:
        return ret;

} /* end sys_request_key() */

/*****************************************************************************/
/*
 * get the ID of the specified process keyring
 * - the keyring must have search permission to be found
 * - implements keyctl(KEYCTL_GET_KEYRING_ID)
 */
long keyctl_get_keyring_ID(key_serial_t id, int create)
{
        key_ref_t key_ref;
        long ret;

        key_ref = lookup_user_key(id, create, 0, KEY_SEARCH);
        if (IS_ERR(key_ref)) {
                ret = PTR_ERR(key_ref);
                goto error;
        }

        ret = key_ref_to_ptr(key_ref)->serial;
        key_ref_put(key_ref);
 error:
        return ret;

} /* end keyctl_get_keyring_ID() */

/*****************************************************************************/
/*
 * join the session keyring
 * - implements keyctl(KEYCTL_JOIN_SESSION_KEYRING)
 */
long keyctl_join_session_keyring(const char __user *_name)
{
        char *name;
        long ret;

        /* fetch the name from userspace */
        name = NULL;
        if (_name) {
                name = strndup_user(_name, PAGE_SIZE);
                if (IS_ERR(name)) {
                        ret = PTR_ERR(name);
                        goto error;
                }
        }

        /* join the session */
        ret = join_session_keyring(name);
        kfree(name);

 error:
        return ret;

} /* end keyctl_join_session_keyring() */

/*****************************************************************************/
/*
 * update a key's data payload
 * - the key must be writable
 * - implements keyctl(KEYCTL_UPDATE)
 */
long keyctl_update_key(key_serial_t id,
                       const void __user *_payload,
                       size_t plen)
{
        key_ref_t key_ref;
        void *payload;
        long ret;

        ret = -EINVAL;
        if (plen > PAGE_SIZE)
                goto error;

        /* pull the payload in if one was supplied */
        payload = NULL;
        if (_payload) {
                ret = -ENOMEM;
                payload = kmalloc(plen, GFP_KERNEL);
                if (!payload)
                        goto error;

                ret = -EFAULT;
                if (copy_from_user(payload, _payload, plen) != 0)
                        goto error2;
        }

        /* find the target key (which must be writable) */
        key_ref = lookup_user_key(id, 0, 0, KEY_WRITE);
        if (IS_ERR(key_ref)) {
                ret = PTR_ERR(key_ref);
                goto error2;
        }

        /* update the key */
        ret = key_update(key_ref, payload, plen);

        key_ref_put(key_ref);
 error2:
        kfree(payload);
 error:
        return ret;

} /* end keyctl_update_key() */

/*****************************************************************************/
/*
 * revoke a key
 * - the key must be writable
 * - implements keyctl(KEYCTL_REVOKE)
 */
long keyctl_revoke_key(key_serial_t id)
{
        key_ref_t key_ref;
        long ret;

        key_ref = lookup_user_key(id, 0, 0, KEY_WRITE);
        if (IS_ERR(key_ref)) {
                ret = PTR_ERR(key_ref);
                goto error;
        }

        key_revoke(key_ref_to_ptr(key_ref));
        ret = 0;

        key_ref_put(key_ref);
 error:
        return ret;

} /* end keyctl_revoke_key() */

/*****************************************************************************/
/*
 * clear the specified process keyring
 * - the keyring must be writable
 * - implements keyctl(KEYCTL_CLEAR)
 */
long keyctl_keyring_clear(key_serial_t ringid)
{
        key_ref_t keyring_ref;
        long ret;

        keyring_ref = lookup_user_key(ringid, 1, 0, KEY_WRITE);
        if (IS_ERR(keyring_ref)) {
                ret = PTR_ERR(keyring_ref);
                goto error;
        }

        ret = keyring_clear(key_ref_to_ptr(keyring_ref));

        key_ref_put(keyring_ref);
 error:
        return ret;

} /* end keyctl_keyring_clear() */

/*****************************************************************************/
/*
 * link a key into a keyring
 * - the keyring must be writable
 * - the key must be linkable
 * - implements keyctl(KEYCTL_LINK)
 */
long keyctl_keyring_link(key_serial_t id, key_serial_t ringid)
{
        key_ref_t keyring_ref, key_ref;
        long ret;

        keyring_ref = lookup_user_key(ringid, 1, 0, KEY_WRITE);
        if (IS_ERR(keyring_ref)) {
                ret = PTR_ERR(keyring_ref);
                goto error;
        }

        key_ref = lookup_user_key(id, 1, 0, KEY_LINK);
        if (IS_ERR(key_ref)) {
                ret = PTR_ERR(key_ref);
                goto error2;
        }

        ret = key_link(key_ref_to_ptr(keyring_ref), key_ref_to_ptr(key_ref));

        key_ref_put(key_ref);
 error2:
        key_ref_put(keyring_ref);
 error:
        return ret;

} /* end keyctl_keyring_link() */

/*****************************************************************************/
/*
 * unlink the first attachment of a key from a keyring
 * - the keyring must be writable
 * - we don't need any permissions on the key
 * - implements keyctl(KEYCTL_UNLINK)
 */
long keyctl_keyring_unlink(key_serial_t id, key_serial_t ringid)
{
        key_ref_t keyring_ref, key_ref;
        long ret;

        keyring_ref = lookup_user_key(ringid, 0, 0, KEY_WRITE);
        if (IS_ERR(keyring_ref)) {
                ret = PTR_ERR(keyring_ref);
                goto error;
        }

        key_ref = lookup_user_key(id, 0, 0, 0);
        if (IS_ERR(key_ref)) {
                ret = PTR_ERR(key_ref);
                goto error2;
        }

        ret = key_unlink(key_ref_to_ptr(keyring_ref), key_ref_to_ptr(key_ref));

        key_ref_put(key_ref);
 error2:
        key_ref_put(keyring_ref);
 error:
        return ret;

} /* end keyctl_keyring_unlink() */

/*****************************************************************************/
/*
 * describe a user key
 * - the key must have view permission
 * - if there's a buffer, we place up to buflen bytes of data into it
 * - unless there's an error, we return the amount of description available,
 *   irrespective of how much we may have copied
 * - the description is formatted thus:
 *      type;uid;gid;perm;description<NUL>
 * - implements keyctl(KEYCTL_DESCRIBE)
 */
long keyctl_describe_key(key_serial_t keyid,
                         char __user *buffer,
                         size_t buflen)
{
        struct key *key, *instkey;
        key_ref_t key_ref;
        char *tmpbuf;
        long ret;

        key_ref = lookup_user_key(keyid, 0, 1, KEY_VIEW);
        if (IS_ERR(key_ref)) {
                /* viewing a key under construction is permitted if we have the
                 * authorisation token handy */
                if (PTR_ERR(key_ref) == -EACCES) {
                        instkey = key_get_instantiation_authkey(keyid);
                        if (!IS_ERR(instkey)) {
                                key_put(instkey);
                                key_ref = lookup_user_key(keyid,
                                                          0, 1, 0);
                                if (!IS_ERR(key_ref))
                                        goto okay;
                        }
                }

                ret = PTR_ERR(key_ref);
                goto error;
        }

okay:
        /* calculate how much description we're going to return */
        ret = -ENOMEM;
        tmpbuf = kmalloc(PAGE_SIZE, GFP_KERNEL);
        if (!tmpbuf)
                goto error2;

        key = key_ref_to_ptr(key_ref);

        ret = snprintf(tmpbuf, PAGE_SIZE - 1,
                       "%s;%d;%d;%08x;%s",
                       key_ref_to_ptr(key_ref)->type->name,
                       key_ref_to_ptr(key_ref)->uid,
                       key_ref_to_ptr(key_ref)->gid,
                       key_ref_to_ptr(key_ref)->perm,
                       key_ref_to_ptr(key_ref)->description ?
                       key_ref_to_ptr(key_ref)->description : ""
                       );

        /* include a NUL char at the end of the data */
        if (ret > PAGE_SIZE - 1)
                ret = PAGE_SIZE - 1;
        tmpbuf[ret] = 0;
        ret++;

        /* consider returning the data */
        if (buffer && buflen > 0) {
                if (buflen > ret)
                        buflen = ret;

                if (copy_to_user(buffer, tmpbuf, buflen) != 0)
                        ret = -EFAULT;
        }

        kfree(tmpbuf);
 error2:
        key_ref_put(key_ref);
 error:
        return ret;

} /* end keyctl_describe_key() */

/*****************************************************************************/
/*
 * search the specified keyring for a matching key
 * - the start keyring must be searchable
 * - nested keyrings may also be searched if they are searchable
 * - only keys with search permission may be found
 * - if a key is found, it will be attached to the destination keyring if
 *   there's one specified
 * - implements keyctl(KEYCTL_SEARCH)
 */
long keyctl_keyring_search(key_serial_t ringid,
                           const char __user *_type,
                           const char __user *_description,
                           key_serial_t destringid)
{
        struct key_type *ktype;
        key_ref_t keyring_ref, key_ref, dest_ref;
        char type[32], *description;
        long ret;

        /* pull the type and description into kernel space */
        ret = key_get_type_from_user(type, _type, sizeof(type));
        if (ret < 0)
                goto error;

        description = strndup_user(_description, PAGE_SIZE);
        if (IS_ERR(description)) {
                ret = PTR_ERR(description);
                goto error;
        }

        /* get the keyring at which to begin the search */
        keyring_ref = lookup_user_key(ringid, 0, 0, KEY_SEARCH);
        if (IS_ERR(keyring_ref)) {
                ret = PTR_ERR(keyring_ref);
                goto error2;
        }

        /* get the destination keyring if specified */
        dest_ref = NULL;
        if (destringid) {
                dest_ref = lookup_user_key(destringid, 1, 0, KEY_WRITE);
                if (IS_ERR(dest_ref)) {
                        ret = PTR_ERR(dest_ref);
                        goto error3;
                }
        }

        /* find the key type */
        ktype = key_type_lookup(type);
        if (IS_ERR(ktype)) {
                ret = PTR_ERR(ktype);
                goto error4;
        }

        /* do the search */
        key_ref = keyring_search(keyring_ref, ktype, description);
        if (IS_ERR(key_ref)) {
                ret = PTR_ERR(key_ref);

                /* treat lack or presence of a negative key the same */
                if (ret == -EAGAIN)
                        ret = -ENOKEY;
                goto error5;
        }

        /* link the resulting key to the destination keyring if we can */
        if (dest_ref) {
                ret = key_permission(key_ref, KEY_LINK);
                if (ret < 0)
                        goto error6;

                ret = key_link(key_ref_to_ptr(dest_ref), key_ref_to_ptr(key_ref));
                if (ret < 0)
                        goto error6;
        }

        ret = key_ref_to_ptr(key_ref)->serial;

 error6:
        key_ref_put(key_ref);
 error5:
        key_type_put(ktype);
 error4:
        key_ref_put(dest_ref);
 error3:
        key_ref_put(keyring_ref);
 error2:
        kfree(description);
 error:
        return ret;

} /* end keyctl_keyring_search() */

/*****************************************************************************/
/*
 * read a user key's payload
 * - the keyring must be readable or the key must be searchable from the
 *   process's keyrings
 * - if there's a buffer, we place up to buflen bytes of data into it
 * - unless there's an error, we return the amount of data in the key,
 *   irrespective of how much we may have copied
 * - implements keyctl(KEYCTL_READ)
 */
long keyctl_read_key(key_serial_t keyid, char __user *buffer, size_t buflen)
{
        struct key *key;
        key_ref_t key_ref;
        long ret;

        /* find the key first */
        key_ref = lookup_user_key(keyid, 0, 0, 0);
        if (IS_ERR(key_ref)) {
                ret = -ENOKEY;
                goto error;
        }

        key = key_ref_to_ptr(key_ref);

        /* see if we can read it directly */
        ret = key_permission(key_ref, KEY_READ);
        if (ret == 0)
                goto can_read_key;
        if (ret != -EACCES)
                goto error;

        /* we can't; see if it's searchable from this process's keyrings
         * - we automatically take account of the fact that it may be
         *   dangling off an instantiation key
         */
        if (!is_key_possessed(key_ref)) {
                ret = -EACCES;
                goto error2;
        }

        /* the key is probably readable - now try to read it */
 can_read_key:
        ret = key_validate(key);
        if (ret == 0) {
                ret = -EOPNOTSUPP;
                if (key->type->read) {
                        /* read the data with the semaphore held (since we
                         * might sleep) */
                        down_read(&key->sem);
                        ret = key->type->read(key, buffer, buflen);
                        up_read(&key->sem);
                }
        }

 error2:
        key_put(key);
 error:
        return ret;

} /* end keyctl_read_key() */

/*****************************************************************************/
/*
 * change the ownership of a key
 * - the keyring owned by the changer
 * - if the uid or gid is -1, then that parameter is not changed
 * - implements keyctl(KEYCTL_CHOWN)
 */
long keyctl_chown_key(key_serial_t id, uid_t uid, gid_t gid)
{
        struct key_user *newowner, *zapowner = NULL;
        struct key *key;
        key_ref_t key_ref;
        long ret;

        ret = 0;
        if (uid == (uid_t) -1 && gid == (gid_t) -1)
                goto error;

        key_ref = lookup_user_key(id, 1, 1, KEY_SETATTR);
        if (IS_ERR(key_ref)) {
                ret = PTR_ERR(key_ref);
                goto error;
        }

        key = key_ref_to_ptr(key_ref);

        /* make the changes with the locks held to prevent chown/chown races */
        ret = -EACCES;
        down_write(&key->sem);

        if (!capable(CAP_SYS_ADMIN)) {
                /* only the sysadmin can chown a key to some other UID */
                if (uid != (uid_t) -1 && key->uid != uid)
                        goto error_put;

                /* only the sysadmin can set the key's GID to a group other
                 * than one of those that the current process subscribes to */
                if (gid != (gid_t) -1 && gid != key->gid && !in_group_p(gid))
                        goto error_put;
        }

        /* change the UID */
        if (uid != (uid_t) -1 && uid != key->uid) {
                ret = -ENOMEM;
                newowner = key_user_lookup(uid, current_user_ns());
                if (!newowner)
                        goto error_put;

                /* transfer the quota burden to the new user */
                if (test_bit(KEY_FLAG_IN_QUOTA, &key->flags)) {
                        unsigned maxkeys = (uid == 0) ?
                                key_quota_root_maxkeys : key_quota_maxkeys;
                        unsigned maxbytes = (uid == 0) ?
                                key_quota_root_maxbytes : key_quota_maxbytes;

                        spin_lock(&newowner->lock);
                        if (newowner->qnkeys + 1 >= maxkeys ||
                            newowner->qnbytes + key->quotalen >= maxbytes ||
                            newowner->qnbytes + key->quotalen <
                            newowner->qnbytes)
                                goto quota_overrun;

                        newowner->qnkeys++;
                        newowner->qnbytes += key->quotalen;
                        spin_unlock(&newowner->lock);

                        spin_lock(&key->user->lock);
                        key->user->qnkeys--;
                        key->user->qnbytes -= key->quotalen;
                        spin_unlock(&key->user->lock);
                }

                atomic_dec(&key->user->nkeys);
                atomic_inc(&newowner->nkeys);

                if (test_bit(KEY_FLAG_INSTANTIATED, &key->flags)) {
                        atomic_dec(&key->user->nikeys);
                        atomic_inc(&newowner->nikeys);
                }

                zapowner = key->user;
                key->user = newowner;
                key->uid = uid;
        }

        /* change the GID */
        if (gid != (gid_t) -1)
                key->gid = gid;

        ret = 0;

error_put:
        up_write(&key->sem);
        key_put(key);
        if (zapowner)
                key_user_put(zapowner);
error:
        return ret;

quota_overrun:
        spin_unlock(&newowner->lock);
        zapowner = newowner;
        ret = -EDQUOT;
        goto error_put;

} /* end keyctl_chown_key() */

/*****************************************************************************/
/*
 * change the permission mask on a key
 * - the keyring owned by the changer
 * - implements keyctl(KEYCTL_SETPERM)
 */
long keyctl_setperm_key(key_serial_t id, key_perm_t perm)
{
        struct key *key;
        key_ref_t key_ref;
        long ret;

        ret = -EINVAL;
        if (perm & ~(KEY_POS_ALL | KEY_USR_ALL | KEY_GRP_ALL | KEY_OTH_ALL))
                goto error;

        key_ref = lookup_user_key(id, 1, 1, KEY_SETATTR);
        if (IS_ERR(key_ref)) {
                ret = PTR_ERR(key_ref);
                goto error;
        }

        key = key_ref_to_ptr(key_ref);

        /* make the changes with the locks held to prevent chown/chmod races */
        ret = -EACCES;
        down_write(&key->sem);

        /* if we're not the sysadmin, we can only change a key that we own */
        if (capable(CAP_SYS_ADMIN) || key->uid == current_fsuid()) {
                key->perm = perm;
                ret = 0;
        }

        up_write(&key->sem);
        key_put(key);
error:
        return ret;

} /* end keyctl_setperm_key() */

/*
 * get the destination keyring for instantiation
 */
static long get_instantiation_keyring(key_serial_t ringid,
                                      struct request_key_auth *rka,
                                      struct key **_dest_keyring)
{
        key_ref_t dkref;

        *_dest_keyring = NULL;

        /* just return a NULL pointer if we weren't asked to make a link */
        if (ringid == 0)
                return 0;

        /* if a specific keyring is nominated by ID, then use that */
        if (ringid > 0) {
                dkref = lookup_user_key(ringid, 1, 0, KEY_WRITE);
                if (IS_ERR(dkref))
                        return PTR_ERR(dkref);
                *_dest_keyring = key_ref_to_ptr(dkref);
                return 0;
        }

        if (ringid == KEY_SPEC_REQKEY_AUTH_KEY)
                return -EINVAL;

        /* otherwise specify the destination keyring recorded in the
         * authorisation key (any KEY_SPEC_*_KEYRING) */
        if (ringid >= KEY_SPEC_REQUESTOR_KEYRING) {
                *_dest_keyring = rka->dest_keyring;
                return 0;
        }

        return -ENOKEY;
}

/*
 * change the request_key authorisation key on the current process
 */
static int keyctl_change_reqkey_auth(struct key *key)
{
        struct cred *new;

        new = prepare_creds();
        if (!new)
                return -ENOMEM;

        key_put(new->request_key_auth);
        new->request_key_auth = key_get(key);

        return commit_creds(new);
}

/*****************************************************************************/
/*
 * instantiate the key with the specified payload, and, if one is given, link
 * the key into the keyring
 */
long keyctl_instantiate_key(key_serial_t id,
                            const void __user *_payload,
                            size_t plen,
                            key_serial_t ringid)
{
        const struct cred *cred = current_cred();
        struct request_key_auth *rka;
        struct key *instkey, *dest_keyring;
        void *payload;
        long ret;
        bool vm = false;

        kenter("%d,,%zu,%d", id, plen, ringid);

        ret = -EINVAL;
        if (plen > 1024 * 1024 - 1)
                goto error;

        /* the appropriate instantiation authorisation key must have been
         * assumed before calling this */
        ret = -EPERM;
        instkey = cred->request_key_auth;
        if (!instkey)
                goto error;

        rka = instkey->payload.data;
        if (rka->target_key->serial != id)
                goto error;

        /* pull the payload in if one was supplied */
        payload = NULL;

        if (_payload) {
                ret = -ENOMEM;
                payload = kmalloc(plen, GFP_KERNEL);
                if (!payload) {
                        if (plen <= PAGE_SIZE)
                                goto error;
                        vm = true;
                        payload = vmalloc(plen);
                        if (!payload)
                                goto error;
                }

                ret = -EFAULT;
                if (copy_from_user(payload, _payload, plen) != 0)
                        goto error2;
        }

        /* find the destination keyring amongst those belonging to the
         * requesting task */
        ret = get_instantiation_keyring(ringid, rka, &dest_keyring);
        if (ret < 0)
                goto error2;

        /* instantiate the key and link it into a keyring */
        ret = key_instantiate_and_link(rka->target_key, payload, plen,
                                       dest_keyring, instkey);

        key_put(dest_keyring);

        /* discard the assumed authority if it's just been disabled by
         * instantiation of the key */
        if (ret == 0)
                keyctl_change_reqkey_auth(NULL);

error2:
        if (!vm)
                kfree(payload);
        else
                vfree(payload);
error:
        return ret;

} /* end keyctl_instantiate_key() */

/*****************************************************************************/
/*
 * negatively instantiate the key with the given timeout (in seconds), and, if
 * one is given, link the key into the keyring
 */
long keyctl_negate_key(key_serial_t id, unsigned timeout, key_serial_t ringid)
{
        const struct cred *cred = current_cred();
        struct request_key_auth *rka;
        struct key *instkey, *dest_keyring;
        long ret;

        kenter("%d,%u,%d", id, timeout, ringid);

        /* the appropriate instantiation authorisation key must have been
         * assumed before calling this */
        ret = -EPERM;
        instkey = cred->request_key_auth;
        if (!instkey)
                goto error;

        rka = instkey->payload.data;
        if (rka->target_key->serial != id)
                goto error;

        /* find the destination keyring if present (which must also be
         * writable) */
        ret = get_instantiation_keyring(ringid, rka, &dest_keyring);
        if (ret < 0)
                goto error;

        /* instantiate the key and link it into a keyring */
        ret = key_negate_and_link(rka->target_key, timeout,

                                  dest_keyring, instkey);

        key_put(dest_keyring);

        /* discard the assumed authority if it's just been disabled by
         * instantiation of the key */
        if (ret == 0)
                keyctl_change_reqkey_auth(NULL);

error:
        return ret;

} /* end keyctl_negate_key() */

/*****************************************************************************/
/*
 * set the default keyring in which request_key() will cache keys
 * - return the old setting
 */
long keyctl_set_reqkey_keyring(int reqkey_defl)
{
        struct cred *new;
        int ret, old_setting;

        old_setting = current_cred_xxx(jit_keyring);

        if (reqkey_defl == KEY_REQKEY_DEFL_NO_CHANGE)
                return old_setting;

        new = prepare_creds();
        if (!new)
                return -ENOMEM;

        switch (reqkey_defl) {
        case KEY_REQKEY_DEFL_THREAD_KEYRING:
                ret = install_thread_keyring_to_cred(new);
                if (ret < 0)
                        goto error;
                goto set;

        case KEY_REQKEY_DEFL_PROCESS_KEYRING:
                ret = install_process_keyring_to_cred(new);
                if (ret < 0) {
                        if (ret != -EEXIST)
                                goto error;
                        ret = 0;
                }
                goto set;

        case KEY_REQKEY_DEFL_DEFAULT:
        case KEY_REQKEY_DEFL_SESSION_KEYRING:
        case KEY_REQKEY_DEFL_USER_KEYRING:
        case KEY_REQKEY_DEFL_USER_SESSION_KEYRING:
        case KEY_REQKEY_DEFL_REQUESTOR_KEYRING:
                goto set;

        case KEY_REQKEY_DEFL_NO_CHANGE:
        case KEY_REQKEY_DEFL_GROUP_KEYRING:
        default:
                ret = -EINVAL;
                goto error;
        }

set:
        new->jit_keyring = reqkey_defl;
        commit_creds(new);
        return old_setting;
error:
        abort_creds(new);
        return -EINVAL;

} /* end keyctl_set_reqkey_keyring() */

/*****************************************************************************/
/*
 * set or clear the timeout for a key
 */
long keyctl_set_timeout(key_serial_t id, unsigned timeout)
{
        struct timespec now;
        struct key *key;
        key_ref_t key_ref;
        time_t expiry;
        long ret;

        key_ref = lookup_user_key(id, 1, 1, KEY_SETATTR);
        if (IS_ERR(key_ref)) {
                ret = PTR_ERR(key_ref);
                goto error;
        }

        key = key_ref_to_ptr(key_ref);

        /* make the changes with the locks held to prevent races */
        down_write(&key->sem);

        expiry = 0;
        if (timeout > 0) {
                now = current_kernel_time();
                expiry = now.tv_sec + timeout;
        }

        key->expiry = expiry;

        up_write(&key->sem);
        key_put(key);

        ret = 0;
error:
        return ret;

} /* end keyctl_set_timeout() */

/*****************************************************************************/
/*
 * assume the authority to instantiate the specified key
 */
long keyctl_assume_authority(key_serial_t id)
{
        struct key *authkey;
        long ret;

        /* special key IDs aren't permitted */
        ret = -EINVAL;
        if (id < 0)
                goto error;

        /* we divest ourselves of authority if given an ID of 0 */
        if (id == 0) {
                ret = keyctl_change_reqkey_auth(NULL);
                goto error;
        }

        /* attempt to assume the authority temporarily granted to us whilst we
         * instantiate the specified key
         * - the authorisation key must be in the current task's keyrings
         *   somewhere
         */
        authkey = key_get_instantiation_authkey(id);
        if (IS_ERR(authkey)) {
                ret = PTR_ERR(authkey);
                goto error;
        }

        ret = keyctl_change_reqkey_auth(authkey);
        if (ret < 0)
                goto error;
        key_put(authkey);

        ret = authkey->serial;
error:
        return ret;

} /* end keyctl_assume_authority() */

/*
 * get the security label of a key
 * - the key must grant us view permission
 * - if there's a buffer, we place up to buflen bytes of data into it
 * - unless there's an error, we return the amount of information available,
 *   irrespective of how much we may have copied (including the terminal NUL)
 * - implements keyctl(KEYCTL_GET_SECURITY)
 */
long keyctl_get_security(key_serial_t keyid,
                         char __user *buffer,
                         size_t buflen)
{
        struct key *key, *instkey;
        key_ref_t key_ref;
        char *context;
        long ret;

        key_ref = lookup_user_key(keyid, 0, 1, KEY_VIEW);
        if (IS_ERR(key_ref)) {
                if (PTR_ERR(key_ref) != -EACCES)
                        return PTR_ERR(key_ref);

                /* viewing a key under construction is also permitted if we
                 * have the authorisation token handy */
                instkey = key_get_instantiation_authkey(keyid);
                if (IS_ERR(instkey))
                        return PTR_ERR(key_ref);
                key_put(instkey);

                key_ref = lookup_user_key(keyid, 0, 1, 0);
                if (IS_ERR(key_ref))
                        return PTR_ERR(key_ref);
        }

        key = key_ref_to_ptr(key_ref);
        ret = security_key_getsecurity(key, &context);
        if (ret == 0) {
                /* if no information was returned, give userspace an empty
                 * string */
                ret = 1;
                if (buffer && buflen > 0 &&
                    copy_to_user(buffer, "", 1) != 0)
                        ret = -EFAULT;
        } else if (ret > 0) {
                /* return as much data as there's room for */
                if (buffer && buflen > 0) {
                        if (buflen > ret)
                                buflen = ret;

                        if (copy_to_user(buffer, context, buflen) != 0)
                                ret = -EFAULT;
                }

                kfree(context);
        }

        key_ref_put(key_ref);
        return ret;
}

/*****************************************************************************/
/*
 * the key control system call
 */
SYSCALL_DEFINE5(keyctl, int, option, unsigned long, arg2, unsigned long, arg3,
                unsigned long, arg4, unsigned long, arg5)
{
        switch (option) {
        case KEYCTL_GET_KEYRING_ID:
                return keyctl_get_keyring_ID((key_serial_t) arg2,
                                             (int) arg3);

        case KEYCTL_JOIN_SESSION_KEYRING:
                return keyctl_join_session_keyring((const char __user *) arg2);

        case KEYCTL_UPDATE:
                return keyctl_update_key((key_serial_t) arg2,
                                         (const void __user *) arg3,
                                         (size_t) arg4);

        case KEYCTL_REVOKE:
                return keyctl_revoke_key((key_serial_t) arg2);

        case KEYCTL_DESCRIBE:
                return keyctl_describe_key((key_serial_t) arg2,
                                           (char __user *) arg3,
                                           (unsigned) arg4);

        case KEYCTL_CLEAR:
                return keyctl_keyring_clear((key_serial_t) arg2);

        case KEYCTL_LINK:
                return keyctl_keyring_link((key_serial_t) arg2,
                                           (key_serial_t) arg3);

        case KEYCTL_UNLINK:
                return keyctl_keyring_unlink((key_serial_t) arg2,
                                             (key_serial_t) arg3);

        case KEYCTL_SEARCH:
                return keyctl_keyring_search((key_serial_t) arg2,
                                             (const char __user *) arg3,
                                             (const char __user *) arg4,
                                             (key_serial_t) arg5);

        case KEYCTL_READ:
                return keyctl_read_key((key_serial_t) arg2,
                                       (char __user *) arg3,
                                       (size_t) arg4);

        case KEYCTL_CHOWN:
                return keyctl_chown_key((key_serial_t) arg2,
                                        (uid_t) arg3,
                                        (gid_t) arg4);

        case KEYCTL_SETPERM:
                return keyctl_setperm_key((key_serial_t) arg2,
                                          (key_perm_t) arg3);

        case KEYCTL_INSTANTIATE:
                return keyctl_instantiate_key((key_serial_t) arg2,
                                              (const void __user *) arg3,
                                              (size_t) arg4,
                                              (key_serial_t) arg5);

        case KEYCTL_NEGATE:
                return keyctl_negate_key((key_serial_t) arg2,
                                         (unsigned) arg3,
                                         (key_serial_t) arg4);

        case KEYCTL_SET_REQKEY_KEYRING:
                return keyctl_set_reqkey_keyring(arg2);

        case KEYCTL_SET_TIMEOUT:
                return keyctl_set_timeout((key_serial_t) arg2,
                                          (unsigned) arg3);

        case KEYCTL_ASSUME_AUTHORITY:
                return keyctl_assume_authority((key_serial_t) arg2);

        case KEYCTL_GET_SECURITY:
                return keyctl_get_security((key_serial_t) arg2,
                                           (char __user *) arg3,
                                           (size_t) arg4);

        default:
                return -EOPNOTSUPP;
        }

} /* end sys_keyctl() */