keyctl.c

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/* Userspace key control operations
 *
 * Copyright (C) 2004-5 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 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/key.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 ret;
    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.
 *
 * If the description is NULL or an empty string, the key type is asked to
 * generate one from the payload.
 *
 * The keyring must be writable so that we can attach the key to it.
 *
 * If successful, the new key's serial number is returned, otherwise an error
 * code is returned.
 */
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 = NULL;
    if (_description) {
        description = strndup_user(_description, PAGE_SIZE);
        if (IS_ERR(description)) {
            ret = PTR_ERR(description);
            goto error;
        }
        if (!*description) {
            kfree(description);
            description = NULL;
        }
    }

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

    vm = false;
    if (_payload) {
        ret = -ENOMEM;
        payload = kmalloc(plen, GFP_KERNEL | __GFP_NOWARN);
        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, KEY_LOOKUP_CREATE, 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;
}

/*
 * Search the process keyrings and keyring trees linked from those for a
 * matching key.  Keyrings must have appropriate Search permission to be
 * searched.
 *
 * If a key is found, it will be attached to the destination keyring if there's
 * one specified and the serial number of the key will be returned.
 *
 * If no key is found, /sbin/request-key will be invoked if _callout_info is
 * non-NULL in an attempt to create a key.  The _callout_info string will be
 * passed to /sbin/request-key to aid with completing the request.  If the
 * _callout_info string is "" then it will be changed to "-".
 */
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, KEY_LOOKUP_CREATE,
                       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;
    }

    /* wait for the key to finish being constructed */
    ret = wait_for_key_construction(key, 1);
    if (ret < 0)
        goto error6;

    ret = key->serial;

error6:
    key_put(key);
error5:
    key_type_put(ktype);
error4:
    key_ref_put(dest_ref);
error3:
    kfree(callout_info);
error2:
    kfree(description);
error:
    return ret;
}

/*
 * Get the ID of the specified process keyring.
 *
 * The requested keyring must have search permission to be found.
 *
 * If successful, the ID of the requested keyring will be returned.
 */
long keyctl_get_keyring_ID(key_serial_t id, int create)
{
    key_ref_t key_ref;
    unsigned long lflags;
    long ret;

    lflags = create ? KEY_LOOKUP_CREATE : 0;
    key_ref = lookup_user_key(id, lflags, 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;
}

/*
 * Join a (named) session keyring.
 *
 * Create and join an anonymous session keyring or join a named session
 * keyring, creating it if necessary.  A named session keyring must have Search
 * permission for it to be joined.  Session keyrings without this permit will
 * be skipped over.
 *
 * If successful, the ID of the joined session keyring will be returned.
 */
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;
}

/*
 * Update a key's data payload from the given data.
 *
 * The key must grant the caller Write permission and the key type must support
 * updating for this to work.  A negative key can be positively instantiated
 * with this call.
 *
 * If successful, 0 will be returned.  If the key type does not support
 * updating, then -EOPNOTSUPP will be returned.
 */
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, 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;
}

/*
 * Revoke a key.
 *
 * The key must be grant the caller Write or Setattr permission for this to
 * work.  The key type should give up its quota claim when revoked.  The key
 * and any links to the key will be automatically garbage collected after a
 * certain amount of time (/proc/sys/kernel/keys/gc_delay).
 *
 * If successful, 0 is returned.
 */
long keyctl_revoke_key(key_serial_t id)
{
    key_ref_t key_ref;
    long ret;

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

/*
 * Invalidate a key.
 *
 * The key must be grant the caller Invalidate permission for this to work.
 * The key and any links to the key will be automatically garbage collected
 * immediately.
 *
 * If successful, 0 is returned.
 */
long keyctl_invalidate_key(key_serial_t id)
{
    key_ref_t key_ref;
    long ret;

    kenter("%d", id);

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

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

    key_ref_put(key_ref);
error:
    kleave(" = %ld", ret);
    return ret;
}

/*
 * Clear the specified keyring, creating an empty process keyring if one of the
 * special keyring IDs is used.
 *
 * The keyring must grant the caller Write permission for this to work.  If
 * successful, 0 will be returned.
 */
long keyctl_keyring_clear(key_serial_t ringid)
{
    key_ref_t keyring_ref;
    long ret;

    keyring_ref = lookup_user_key(ringid, KEY_LOOKUP_CREATE, KEY_WRITE);
    if (IS_ERR(keyring_ref)) {
        ret = PTR_ERR(keyring_ref);

        /* Root is permitted to invalidate certain special keyrings */
        if (capable(CAP_SYS_ADMIN)) {
            keyring_ref = lookup_user_key(ringid, 0, 0);
            if (IS_ERR(keyring_ref))
                goto error;
            if (test_bit(KEY_FLAG_ROOT_CAN_CLEAR,
                     &key_ref_to_ptr(keyring_ref)->flags))
                goto clear;
            goto error_put;
        }

        goto error;
    }

clear:
    ret = keyring_clear(key_ref_to_ptr(keyring_ref));
error_put:
    key_ref_put(keyring_ref);
error:
    return ret;
}

/*
 * Create a link from a keyring to a key if there's no matching key in the
 * keyring, otherwise replace the link to the matching key with a link to the
 * new key.
 *
 * The key must grant the caller Link permission and the the keyring must grant
 * the caller Write permission.  Furthermore, if an additional link is created,
 * the keyring's quota will be extended.
 *
 * If successful, 0 will be returned.
 */
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, KEY_LOOKUP_CREATE, KEY_WRITE);
    if (IS_ERR(keyring_ref)) {
        ret = PTR_ERR(keyring_ref);
        goto error;
    }

    key_ref = lookup_user_key(id, KEY_LOOKUP_CREATE, 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;
}

/*
 * Unlink a key from a keyring.
 *
 * The keyring must grant the caller Write permission for this to work; the key
 * itself need not grant the caller anything.  If the last link to a key is
 * removed then that key will be scheduled for destruction.
 *
 * If successful, 0 will be returned.
 */
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, KEY_WRITE);
    if (IS_ERR(keyring_ref)) {
        ret = PTR_ERR(keyring_ref);
        goto error;
    }

    key_ref = lookup_user_key(id, KEY_LOOKUP_FOR_UNLINK, 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;
}

/*
 * Return a description of a key to userspace.
 *
 * The key must grant the caller View permission for this to work.
 *
 * If there's a buffer, we place up to buflen bytes of data into it formatted
 * in the following way:
 *
 *  type;uid;gid;perm;description<NUL>
 *
 * If successful, we return the amount of description available, irrespective
 * of how much we may have copied into the buffer.
 */
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, KEY_LOOKUP_PARTIAL, 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,
                              KEY_LOOKUP_PARTIAL,
                              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->type->name,
               from_kuid_munged(current_user_ns(), key->uid),
               from_kgid_munged(current_user_ns(), key->gid),
               key->perm,
               key->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;
}

/*
 * Search the specified keyring and any keyrings it links to for a matching
 * key.  Only keyrings that grant the caller Search permission will be searched
 * (this includes the starting keyring).  Only keys with Search permission can
 * be found.
 *
 * If successful, the found key will be linked to the destination keyring if
 * supplied and the key has Link permission, and the found key ID will be
 * returned.
 */
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, 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, KEY_LOOKUP_CREATE,
                       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;
}

/*
 * Read a key's payload.
 *
 * The key must either grant the caller Read permission, or it must grant the
 * caller Search permission when searched for from the process keyrings.
 *
 * If successful, we place up to buflen bytes of data into the buffer, if one
 * is provided, and return the amount of data that is available in the key,
 * irrespective of how much we copied into the buffer.
 */
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);
    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;
}

/*
 * Change the ownership of a key
 *
 * The key must grant the caller Setattr permission for this to work, though
 * the key need not be fully instantiated yet.  For the UID to be changed, or
 * for the GID to be changed to a group the caller is not a member of, the
 * caller must have sysadmin capability.  If either uid or gid is -1 then that
 * attribute is not changed.
 *
 * If the UID is to be changed, the new user must have sufficient quota to
 * accept the key.  The quota deduction will be removed from the old user to
 * the new user should the attribute be changed.
 *
 * If successful, 0 will be returned.
 */
long keyctl_chown_key(key_serial_t id, uid_t user, gid_t group)
{
    struct key_user *newowner, *zapowner = NULL;
    struct key *key;
    key_ref_t key_ref;
    long ret;
    kuid_t uid;
    kgid_t gid;

    uid = make_kuid(current_user_ns(), user);
    gid = make_kgid(current_user_ns(), group);
    ret = -EINVAL;
    if ((user != (uid_t) -1) && !uid_valid(uid))
        goto error;
    if ((group != (gid_t) -1) && !gid_valid(gid))
        goto error;

    ret = 0;
    if (user == (uid_t) -1 && group == (gid_t) -1)
        goto error;

    key_ref = lookup_user_key(id, KEY_LOOKUP_CREATE | KEY_LOOKUP_PARTIAL,
                  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 (user != (uid_t) -1 && !uid_eq(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 (group != (gid_t) -1 && !gid_eq(gid, key->gid) && !in_group_p(gid))
            goto error_put;
    }

    /* change the UID */
    if (user != (uid_t) -1 && !uid_eq(uid, key->uid)) {
        ret = -ENOMEM;
        newowner = key_user_lookup(uid);
        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_eq(uid, GLOBAL_ROOT_UID) ?
                key_quota_root_maxkeys : key_quota_maxkeys;
            unsigned maxbytes = uid_eq(uid, GLOBAL_ROOT_UID) ?
                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 (group != (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;
}

/*
 * Change the permission mask on a key.
 *
 * The key must grant the caller Setattr permission for this to work, though
 * the key need not be fully instantiated yet.  If the caller does not have
 * sysadmin capability, it may only change the permission on keys that it owns.
 */
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, KEY_LOOKUP_CREATE | KEY_LOOKUP_PARTIAL,
                  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) || uid_eq(key->uid, current_fsuid())) {
        key->perm = perm;
        ret = 0;
    }

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

/*
 * Get the destination keyring for instantiation and check that the caller has
 * Write permission on it.
 */
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, KEY_LOOKUP_CREATE, 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 = key_get(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);
}

/*
 * Copy the iovec data from userspace
 */
static long copy_from_user_iovec(void *buffer, const struct iovec *iov,
                 unsigned ioc)
{
    for (; ioc > 0; ioc--) {
        if (copy_from_user(buffer, iov->iov_base, iov->iov_len) != 0)
            return -EFAULT;
        buffer += iov->iov_len;
        iov++;
    }
    return 0;
}

/*
 * Instantiate a key with the specified payload and link the key into the
 * destination keyring if one is given.
 *
 * The caller must have the appropriate instantiation permit set for this to
 * work (see keyctl_assume_authority).  No other permissions are required.
 *
 * If successful, 0 will be returned.
 */
long keyctl_instantiate_key_common(key_serial_t id,
                   const struct iovec *payload_iov,
                   unsigned ioc,
                   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_iov) {
        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 = copy_from_user_iovec(payload, payload_iov, ioc);
        if (ret < 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;
}

/*
 * Instantiate a key with the specified payload and link the key into the
 * destination keyring if one is given.
 *
 * The caller must have the appropriate instantiation permit set for this to
 * work (see keyctl_assume_authority).  No other permissions are required.
 *
 * If successful, 0 will be returned.
 */
long keyctl_instantiate_key(key_serial_t id,
                const void __user *_payload,
                size_t plen,
                key_serial_t ringid)
{
    if (_payload && plen) {
        struct iovec iov[1] = {
            [0].iov_base = (void __user *)_payload,
            [0].iov_len  = plen
        };

        return keyctl_instantiate_key_common(id, iov, 1, plen, ringid);
    }

    return keyctl_instantiate_key_common(id, NULL, 0, 0, ringid);
}

/*
 * Instantiate a key with the specified multipart payload and link the key into
 * the destination keyring if one is given.
 *
 * The caller must have the appropriate instantiation permit set for this to
 * work (see keyctl_assume_authority).  No other permissions are required.
 *
 * If successful, 0 will be returned.
 */
long keyctl_instantiate_key_iov(key_serial_t id,
                const struct iovec __user *_payload_iov,
                unsigned ioc,
                key_serial_t ringid)
{
    struct iovec iovstack[UIO_FASTIOV], *iov = iovstack;
    long ret;

    if (!_payload_iov || !ioc)
        goto no_payload;

    ret = rw_copy_check_uvector(WRITE, _payload_iov, ioc,
                    ARRAY_SIZE(iovstack), iovstack, &iov);
    if (ret < 0)
        return ret;
    if (ret == 0)
        goto no_payload_free;

    ret = keyctl_instantiate_key_common(id, iov, ioc, ret, ringid);

    if (iov != iovstack)
        kfree(iov);
    return ret;

no_payload_free:
    if (iov != iovstack)
        kfree(iov);
no_payload:
    return keyctl_instantiate_key_common(id, NULL, 0, 0, ringid);
}

/*
 * Negatively instantiate the key with the given timeout (in seconds) and link
 * the key into the destination keyring if one is given.
 *
 * The caller must have the appropriate instantiation permit set for this to
 * work (see keyctl_assume_authority).  No other permissions are required.
 *
 * The key and any links to the key will be automatically garbage collected
 * after the timeout expires.
 *
 * Negative keys are used to rate limit repeated request_key() calls by causing
 * them to return -ENOKEY until the negative key expires.
 *
 * If successful, 0 will be returned.
 */
long keyctl_negate_key(key_serial_t id, unsigned timeout, key_serial_t ringid)
{
    return keyctl_reject_key(id, timeout, ENOKEY, ringid);
}

/*
 * Negatively instantiate the key with the given timeout (in seconds) and error
 * code and link the key into the destination keyring if one is given.
 *
 * The caller must have the appropriate instantiation permit set for this to
 * work (see keyctl_assume_authority).  No other permissions are required.
 *
 * The key and any links to the key will be automatically garbage collected
 * after the timeout expires.
 *
 * Negative keys are used to rate limit repeated request_key() calls by causing
 * them to return the specified error code until the negative key expires.
 *
 * If successful, 0 will be returned.
 */
long keyctl_reject_key(key_serial_t id, unsigned timeout, unsigned error,
               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,%u,%d", id, timeout, error, ringid);

    /* must be a valid error code and mustn't be a kernel special */
    if (error <= 0 ||
        error >= MAX_ERRNO ||
        error == ERESTARTSYS ||
        error == ERESTARTNOINTR ||
        error == ERESTARTNOHAND ||
        error == ERESTART_RESTARTBLOCK)
        return -EINVAL;

    /* 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_reject_and_link(rka->target_key, timeout, error,
                  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;
}

/*
 * Read or set the default keyring in which request_key() will cache keys and
 * return the old setting.
 *
 * If a process keyring is specified then this will be created if it doesn't
 * yet exist.  The old setting will be returned if successful.
 */
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 ret;
}

/*
 * Set or clear the timeout on a key.
 *
 * Either the key must grant the caller Setattr permission or else the caller
 * must hold an instantiation authorisation token for the key.
 *
 * The timeout is either 0 to clear the timeout, or a number of seconds from
 * the current time.  The key and any links to the key will be automatically
 * garbage collected after the timeout expires.
 *
 * If successful, 0 is returned.
 */
long keyctl_set_timeout(key_serial_t id, unsigned timeout)
{
    struct key *key, *instkey;
    key_ref_t key_ref;
    long ret;

    key_ref = lookup_user_key(id, KEY_LOOKUP_CREATE | KEY_LOOKUP_PARTIAL,
                  KEY_SETATTR);
    if (IS_ERR(key_ref)) {
        /* setting the timeout on a key under construction is permitted
         * if we have the authorisation token handy */
        if (PTR_ERR(key_ref) == -EACCES) {
            instkey = key_get_instantiation_authkey(id);
            if (!IS_ERR(instkey)) {
                key_put(instkey);
                key_ref = lookup_user_key(id,
                              KEY_LOOKUP_PARTIAL,
                              0);
                if (!IS_ERR(key_ref))
                    goto okay;
            }
        }

        ret = PTR_ERR(key_ref);
        goto error;
    }

okay:
    key = key_ref_to_ptr(key_ref);
    key_set_timeout(key, timeout);
    key_put(key);

    ret = 0;
error:
    return ret;
}

/*
 * Assume (or clear) the authority to instantiate the specified key.
 *
 * This sets the authoritative token currently in force for key instantiation.
 * This must be done for a key to be instantiated.  It has the effect of making
 * available all the keys from the caller of the request_key() that created a
 * key to request_key() calls made by the caller of this function.
 *
 * The caller must have the instantiation key in their process keyrings with a
 * Search permission grant available to the caller.
 *
 * If the ID given is 0, then the setting will be cleared and 0 returned.
 *
 * If the ID given has a matching an authorisation key, then that key will be
 * set and its ID will be returned.  The authorisation key can be read to get
 * the callout information passed to request_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;
}

/*
 * Get a key's the LSM security label.
 *
 * The key must grant the caller View permission for this to work.
 *
 * If there's a buffer, then up to buflen bytes of data will be placed into it.
 *
 * If successful, the amount of information available will be returned,
 * irrespective of how much was copied (including the terminal NUL).
 */
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, KEY_LOOKUP_PARTIAL, 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(instkey);
        key_put(instkey);

        key_ref = lookup_user_key(keyid, KEY_LOOKUP_PARTIAL, 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;
}

/*
 * Attempt to install the calling process's session keyring on the process's
 * parent process.
 *
 * The keyring must exist and must grant the caller LINK permission, and the
 * parent process must be single-threaded and must have the same effective
 * ownership as this process and mustn't be SUID/SGID.
 *
 * The keyring will be emplaced on the parent when it next resumes userspace.
 *
 * If successful, 0 will be returned.
 */
long keyctl_session_to_parent(void)
{
    struct task_struct *me, *parent;
    const struct cred *mycred, *pcred;
    struct callback_head *newwork, *oldwork;
    key_ref_t keyring_r;
    struct cred *cred;
    int ret;

    keyring_r = lookup_user_key(KEY_SPEC_SESSION_KEYRING, 0, KEY_LINK);
    if (IS_ERR(keyring_r))
        return PTR_ERR(keyring_r);

    ret = -ENOMEM;

    /* our parent is going to need a new cred struct, a new tgcred struct
     * and new security data, so we allocate them here to prevent ENOMEM in
     * our parent */
    cred = cred_alloc_blank();
    if (!cred)
        goto error_keyring;
    newwork = &cred->rcu;

    cred->tgcred->session_keyring = key_ref_to_ptr(keyring_r);
    init_task_work(newwork, key_change_session_keyring);

    me = current;
    rcu_read_lock();
    write_lock_irq(&tasklist_lock);

    ret = -EPERM;
    oldwork = NULL;
    parent = me->real_parent;

    /* the parent mustn't be init and mustn't be a kernel thread */
    if (parent->pid <= 1 || !parent->mm)
        goto unlock;

    /* the parent must be single threaded */
    if (!thread_group_empty(parent))
        goto unlock;

    /* the parent and the child must have different session keyrings or
     * there's no point */
    mycred = current_cred();
    pcred = __task_cred(parent);
    if (mycred == pcred ||
        mycred->tgcred->session_keyring == pcred->tgcred->session_keyring) {
        ret = 0;
        goto unlock;
    }

    /* the parent must have the same effective ownership and mustn't be
     * SUID/SGID */
    if (!uid_eq(pcred->uid,  mycred->euid) ||
        !uid_eq(pcred->euid, mycred->euid) ||
        !uid_eq(pcred->suid, mycred->euid) ||
        !gid_eq(pcred->gid,  mycred->egid) ||
        !gid_eq(pcred->egid, mycred->egid) ||
        !gid_eq(pcred->sgid, mycred->egid))
        goto unlock;

    /* the keyrings must have the same UID */
    if ((pcred->tgcred->session_keyring &&
         !uid_eq(pcred->tgcred->session_keyring->uid, mycred->euid)) ||
        !uid_eq(mycred->tgcred->session_keyring->uid, mycred->euid))
        goto unlock;

    /* cancel an already pending keyring replacement */
    oldwork = task_work_cancel(parent, key_change_session_keyring);

    /* the replacement session keyring is applied just prior to userspace
     * restarting */
    ret = task_work_add(parent, newwork, true);
    if (!ret)
        newwork = NULL;
unlock:
    write_unlock_irq(&tasklist_lock);
    rcu_read_unlock();
    if (oldwork)
        put_cred(container_of(oldwork, struct cred, rcu));
    if (newwork)
        put_cred(cred);
    return ret;

error_keyring:
    key_ref_put(keyring_r);
    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);

    case KEYCTL_SESSION_TO_PARENT:
        return keyctl_session_to_parent();

    case KEYCTL_REJECT:
        return keyctl_reject_key((key_serial_t) arg2,
                     (unsigned) arg3,
                     (unsigned) arg4,
                     (key_serial_t) arg5);

    case KEYCTL_INSTANTIATE_IOV:
        return keyctl_instantiate_key_iov(
            (key_serial_t) arg2,
            (const struct iovec __user *) arg3,
            (unsigned) arg4,
            (key_serial_t) arg5);

    case KEYCTL_INVALIDATE:
        return keyctl_invalidate_key((key_serial_t) arg2);

    default:
        return -EOPNOTSUPP;
    }
}