linux/security/keys/user_defined.c
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   1/* user_defined.c: user defined key type
   2 *
   3 * Copyright (C) 2004 Red Hat, Inc. All Rights Reserved.
   4 * Written by David Howells (dhowells@redhat.com)
   5 *
   6 * This program is free software; you can redistribute it and/or
   7 * modify it under the terms of the GNU General Public License
   8 * as published by the Free Software Foundation; either version
   9 * 2 of the License, or (at your option) any later version.
  10 */
  11
  12#include <linux/module.h>
  13#include <linux/init.h>
  14#include <linux/slab.h>
  15#include <linux/seq_file.h>
  16#include <linux/err.h>
  17#include <keys/user-type.h>
  18#include <linux/uaccess.h>
  19#include "internal.h"
  20
  21static int logon_vet_description(const char *desc);
  22
  23/*
  24 * user defined keys take an arbitrary string as the description and an
  25 * arbitrary blob of data as the payload
  26 */
  27struct key_type key_type_user = {
  28        .name                   = "user",
  29        .preparse               = user_preparse,
  30        .free_preparse          = user_free_preparse,
  31        .instantiate            = generic_key_instantiate,
  32        .update                 = user_update,
  33        .revoke                 = user_revoke,
  34        .destroy                = user_destroy,
  35        .describe               = user_describe,
  36        .read                   = user_read,
  37};
  38
  39EXPORT_SYMBOL_GPL(key_type_user);
  40
  41/*
  42 * This key type is essentially the same as key_type_user, but it does
  43 * not define a .read op. This is suitable for storing username and
  44 * password pairs in the keyring that you do not want to be readable
  45 * from userspace.
  46 */
  47struct key_type key_type_logon = {
  48        .name                   = "logon",
  49        .preparse               = user_preparse,
  50        .free_preparse          = user_free_preparse,
  51        .instantiate            = generic_key_instantiate,
  52        .update                 = user_update,
  53        .revoke                 = user_revoke,
  54        .destroy                = user_destroy,
  55        .describe               = user_describe,
  56        .vet_description        = logon_vet_description,
  57};
  58EXPORT_SYMBOL_GPL(key_type_logon);
  59
  60/*
  61 * Preparse a user defined key payload
  62 */
  63int user_preparse(struct key_preparsed_payload *prep)
  64{
  65        struct user_key_payload *upayload;
  66        size_t datalen = prep->datalen;
  67
  68        if (datalen <= 0 || datalen > 32767 || !prep->data)
  69                return -EINVAL;
  70
  71        upayload = kmalloc(sizeof(*upayload) + datalen, GFP_KERNEL);
  72        if (!upayload)
  73                return -ENOMEM;
  74
  75        /* attach the data */
  76        prep->quotalen = datalen;
  77        prep->payload.data[0] = upayload;
  78        upayload->datalen = datalen;
  79        memcpy(upayload->data, prep->data, datalen);
  80        return 0;
  81}
  82EXPORT_SYMBOL_GPL(user_preparse);
  83
  84/*
  85 * Free a preparse of a user defined key payload
  86 */
  87void user_free_preparse(struct key_preparsed_payload *prep)
  88{
  89        kzfree(prep->payload.data[0]);
  90}
  91EXPORT_SYMBOL_GPL(user_free_preparse);
  92
  93static void user_free_payload_rcu(struct rcu_head *head)
  94{
  95        struct user_key_payload *payload;
  96
  97        payload = container_of(head, struct user_key_payload, rcu);
  98        kzfree(payload);
  99}
 100
 101/*
 102 * update a user defined key
 103 * - the key's semaphore is write-locked
 104 */
 105int user_update(struct key *key, struct key_preparsed_payload *prep)
 106{
 107        struct user_key_payload *zap = NULL;
 108        int ret;
 109
 110        /* check the quota and attach the new data */
 111        ret = key_payload_reserve(key, prep->datalen);
 112        if (ret < 0)
 113                return ret;
 114
 115        /* attach the new data, displacing the old */
 116        key->expiry = prep->expiry;
 117        if (key_is_positive(key))
 118                zap = dereference_key_locked(key);
 119        rcu_assign_keypointer(key, prep->payload.data[0]);
 120        prep->payload.data[0] = NULL;
 121
 122        if (zap)
 123                call_rcu(&zap->rcu, user_free_payload_rcu);
 124        return ret;
 125}
 126EXPORT_SYMBOL_GPL(user_update);
 127
 128/*
 129 * dispose of the links from a revoked keyring
 130 * - called with the key sem write-locked
 131 */
 132void user_revoke(struct key *key)
 133{
 134        struct user_key_payload *upayload = user_key_payload_locked(key);
 135
 136        /* clear the quota */
 137        key_payload_reserve(key, 0);
 138
 139        if (upayload) {
 140                rcu_assign_keypointer(key, NULL);
 141                call_rcu(&upayload->rcu, user_free_payload_rcu);
 142        }
 143}
 144
 145EXPORT_SYMBOL(user_revoke);
 146
 147/*
 148 * dispose of the data dangling from the corpse of a user key
 149 */
 150void user_destroy(struct key *key)
 151{
 152        struct user_key_payload *upayload = key->payload.data[0];
 153
 154        kzfree(upayload);
 155}
 156
 157EXPORT_SYMBOL_GPL(user_destroy);
 158
 159/*
 160 * describe the user key
 161 */
 162void user_describe(const struct key *key, struct seq_file *m)
 163{
 164        seq_puts(m, key->description);
 165        if (key_is_positive(key))
 166                seq_printf(m, ": %u", key->datalen);
 167}
 168
 169EXPORT_SYMBOL_GPL(user_describe);
 170
 171/*
 172 * read the key data
 173 * - the key's semaphore is read-locked
 174 */
 175long user_read(const struct key *key, char __user *buffer, size_t buflen)
 176{
 177        const struct user_key_payload *upayload;
 178        long ret;
 179
 180        upayload = user_key_payload_locked(key);
 181        ret = upayload->datalen;
 182
 183        /* we can return the data as is */
 184        if (buffer && buflen > 0) {
 185                if (buflen > upayload->datalen)
 186                        buflen = upayload->datalen;
 187
 188                if (copy_to_user(buffer, upayload->data, buflen) != 0)
 189                        ret = -EFAULT;
 190        }
 191
 192        return ret;
 193}
 194
 195EXPORT_SYMBOL_GPL(user_read);
 196
 197/* Vet the description for a "logon" key */
 198static int logon_vet_description(const char *desc)
 199{
 200        char *p;
 201
 202        /* require a "qualified" description string */
 203        p = strchr(desc, ':');
 204        if (!p)
 205                return -EINVAL;
 206
 207        /* also reject description with ':' as first char */
 208        if (p == desc)
 209                return -EINVAL;
 210
 211        return 0;
 212}
 213