user_defined.c

Go to the documentation of this file.

/* user_defined.c: user defined key type
 *
 * Copyright (C) 2004 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/slab.h>
#include <linux/seq_file.h>
#include <linux/err.h>
#include <keys/user-type.h>
#include <asm/uaccess.h>
#include "internal.h"

static int logon_vet_description(const char *desc);

/*
 * user defined keys take an arbitrary string as the description and an
 * arbitrary blob of data as the payload
 */
struct key_type key_type_user = {
    .name       = "user",
    .instantiate    = user_instantiate,
    .update     = user_update,
    .match      = user_match,
    .revoke     = user_revoke,
    .destroy    = user_destroy,
    .describe   = user_describe,
    .read       = user_read,
};

EXPORT_SYMBOL_GPL(key_type_user);

/*
 * This key type is essentially the same as key_type_user, but it does
 * not define a .read op. This is suitable for storing username and
 * password pairs in the keyring that you do not want to be readable
 * from userspace.
 */
struct key_type key_type_logon = {
    .name           = "logon",
    .instantiate        = user_instantiate,
    .update         = user_update,
    .match          = user_match,
    .revoke         = user_revoke,
    .destroy        = user_destroy,
    .describe       = user_describe,
    .vet_description    = logon_vet_description,
};
EXPORT_SYMBOL_GPL(key_type_logon);

/*
 * instantiate a user defined key
 */
int user_instantiate(struct key *key, struct key_preparsed_payload *prep)
{
    struct user_key_payload *upayload;
    size_t datalen = prep->datalen;
    int ret;

    ret = -EINVAL;
    if (datalen <= 0 || datalen > 32767 || !prep->data)
        goto error;

    ret = key_payload_reserve(key, datalen);
    if (ret < 0)
        goto error;

    ret = -ENOMEM;
    upayload = kmalloc(sizeof(*upayload) + datalen, GFP_KERNEL);
    if (!upayload)
        goto error;

    /* attach the data */
    upayload->datalen = datalen;
    memcpy(upayload->data, prep->data, datalen);
    rcu_assign_keypointer(key, upayload);
    ret = 0;

error:
    return ret;
}

EXPORT_SYMBOL_GPL(user_instantiate);

/*
 * update a user defined key
 * - the key's semaphore is write-locked
 */
int user_update(struct key *key, struct key_preparsed_payload *prep)
{
    struct user_key_payload *upayload, *zap;
    size_t datalen = prep->datalen;
    int ret;

    ret = -EINVAL;
    if (datalen <= 0 || datalen > 32767 || !prep->data)
        goto error;

    /* construct a replacement payload */
    ret = -ENOMEM;
    upayload = kmalloc(sizeof(*upayload) + datalen, GFP_KERNEL);
    if (!upayload)
        goto error;

    upayload->datalen = datalen;
    memcpy(upayload->data, prep->data, datalen);

    /* check the quota and attach the new data */
    zap = upayload;

    ret = key_payload_reserve(key, datalen);

    if (ret == 0) {
        /* attach the new data, displacing the old */
        zap = key->payload.data;
        rcu_assign_keypointer(key, upayload);
        key->expiry = 0;
    }

    if (zap)
        kfree_rcu(zap, rcu);

error:
    return ret;
}

EXPORT_SYMBOL_GPL(user_update);

/*
 * match users on their name
 */
int user_match(const struct key *key, const void *description)
{
    return strcmp(key->description, description) == 0;
}

EXPORT_SYMBOL_GPL(user_match);

/*
 * dispose of the links from a revoked keyring
 * - called with the key sem write-locked
 */
void user_revoke(struct key *key)
{
    struct user_key_payload *upayload = key->payload.data;

    /* clear the quota */
    key_payload_reserve(key, 0);

    if (upayload) {
        rcu_assign_keypointer(key, NULL);
        kfree_rcu(upayload, rcu);
    }
}

EXPORT_SYMBOL(user_revoke);

/*
 * dispose of the data dangling from the corpse of a user key
 */
void user_destroy(struct key *key)
{
    struct user_key_payload *upayload = key->payload.data;

    kfree(upayload);
}

EXPORT_SYMBOL_GPL(user_destroy);

/*
 * describe the user key
 */
void user_describe(const struct key *key, struct seq_file *m)
{
    seq_puts(m, key->description);
    if (key_is_instantiated(key))
        seq_printf(m, ": %u", key->datalen);
}

EXPORT_SYMBOL_GPL(user_describe);

/*
 * read the key data
 * - the key's semaphore is read-locked
 */
long user_read(const struct key *key, char __user *buffer, size_t buflen)
{
    struct user_key_payload *upayload;
    long ret;

    upayload = rcu_dereference_key(key);
    ret = upayload->datalen;

    /* we can return the data as is */
    if (buffer && buflen > 0) {
        if (buflen > upayload->datalen)
            buflen = upayload->datalen;

        if (copy_to_user(buffer, upayload->data, buflen) != 0)
            ret = -EFAULT;
    }

    return ret;
}

EXPORT_SYMBOL_GPL(user_read);

/* Vet the description for a "logon" key */
static int logon_vet_description(const char *desc)
{
    char *p;

    /* require a "qualified" description string */
    p = strchr(desc, ':');
    if (!p)
        return -EINVAL;

    /* also reject description with ':' as first char */
    if (p == desc)
        return -EINVAL;

    return 0;
}