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 <asm/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        .instantiate    = user_instantiate,
  30        .update         = user_update,
  31        .match          = user_match,
  32        .revoke         = user_revoke,
  33        .destroy        = user_destroy,
  34        .describe       = user_describe,
  35        .read           = user_read,
  36};
  37
  38EXPORT_SYMBOL_GPL(key_type_user);
  39
  40/*
  41 * This key type is essentially the same as key_type_user, but it does
  42 * not define a .read op. This is suitable for storing username and
  43 * password pairs in the keyring that you do not want to be readable
  44 * from userspace.
  45 */
  46struct key_type key_type_logon = {
  47        .name                   = "logon",
  48        .instantiate            = user_instantiate,
  49        .update                 = user_update,
  50        .match                  = user_match,
  51        .revoke                 = user_revoke,
  52        .destroy                = user_destroy,
  53        .describe               = user_describe,
  54        .vet_description        = logon_vet_description,
  55};
  56EXPORT_SYMBOL_GPL(key_type_logon);
  57
  58/*
  59 * instantiate a user defined key
  60 */
  61int user_instantiate(struct key *key, struct key_preparsed_payload *prep)
  62{
  63        struct user_key_payload *upayload;
  64        size_t datalen = prep->datalen;
  65        int ret;
  66
  67        ret = -EINVAL;
  68        if (datalen <= 0 || datalen > 32767 || !prep->data)
  69                goto error;
  70
  71        ret = key_payload_reserve(key, datalen);
  72        if (ret < 0)
  73                goto error;
  74
  75        ret = -ENOMEM;
  76        upayload = kmalloc(sizeof(*upayload) + datalen, GFP_KERNEL);
  77        if (!upayload)
  78                goto error;
  79
  80        /* attach the data */
  81        upayload->datalen = datalen;
  82        memcpy(upayload->data, prep->data, datalen);
  83        rcu_assign_keypointer(key, upayload);
  84        ret = 0;
  85
  86error:
  87        return ret;
  88}
  89
  90EXPORT_SYMBOL_GPL(user_instantiate);
  91
  92/*
  93 * update a user defined key
  94 * - the key's semaphore is write-locked
  95 */
  96int user_update(struct key *key, struct key_preparsed_payload *prep)
  97{
  98        struct user_key_payload *upayload, *zap;
  99        size_t datalen = prep->datalen;
 100        int ret;
 101
 102        ret = -EINVAL;
 103        if (datalen <= 0 || datalen > 32767 || !prep->data)
 104                goto error;
 105
 106        /* construct a replacement payload */
 107        ret = -ENOMEM;
 108        upayload = kmalloc(sizeof(*upayload) + datalen, GFP_KERNEL);
 109        if (!upayload)
 110                goto error;
 111
 112        upayload->datalen = datalen;
 113        memcpy(upayload->data, prep->data, datalen);
 114
 115        /* check the quota and attach the new data */
 116        zap = upayload;
 117
 118        ret = key_payload_reserve(key, datalen);
 119
 120        if (ret == 0) {
 121                /* attach the new data, displacing the old */
 122                zap = key->payload.data;
 123                rcu_assign_keypointer(key, upayload);
 124                key->expiry = 0;
 125        }
 126
 127        if (zap)
 128                kfree_rcu(zap, rcu);
 129
 130error:
 131        return ret;
 132}
 133
 134EXPORT_SYMBOL_GPL(user_update);
 135
 136/*
 137 * match users on their name
 138 */
 139int user_match(const struct key *key, const void *description)
 140{
 141        return strcmp(key->description, description) == 0;
 142}
 143
 144EXPORT_SYMBOL_GPL(user_match);
 145
 146/*
 147 * dispose of the links from a revoked keyring
 148 * - called with the key sem write-locked
 149 */
 150void user_revoke(struct key *key)
 151{
 152        struct user_key_payload *upayload = key->payload.data;
 153
 154        /* clear the quota */
 155        key_payload_reserve(key, 0);
 156
 157        if (upayload) {
 158                rcu_assign_keypointer(key, NULL);
 159                kfree_rcu(upayload, rcu);
 160        }
 161}
 162
 163EXPORT_SYMBOL(user_revoke);
 164
 165/*
 166 * dispose of the data dangling from the corpse of a user key
 167 */
 168void user_destroy(struct key *key)
 169{
 170        struct user_key_payload *upayload = key->payload.data;
 171
 172        kfree(upayload);
 173}
 174
 175EXPORT_SYMBOL_GPL(user_destroy);
 176
 177/*
 178 * describe the user key
 179 */
 180void user_describe(const struct key *key, struct seq_file *m)
 181{
 182        seq_puts(m, key->description);
 183        if (key_is_instantiated(key))
 184                seq_printf(m, ": %u", key->datalen);
 185}
 186
 187EXPORT_SYMBOL_GPL(user_describe);
 188
 189/*
 190 * read the key data
 191 * - the key's semaphore is read-locked
 192 */
 193long user_read(const struct key *key, char __user *buffer, size_t buflen)
 194{
 195        struct user_key_payload *upayload;
 196        long ret;
 197
 198        upayload = rcu_dereference_key(key);
 199        ret = upayload->datalen;
 200
 201        /* we can return the data as is */
 202        if (buffer && buflen > 0) {
 203                if (buflen > upayload->datalen)
 204                        buflen = upayload->datalen;
 205
 206                if (copy_to_user(buffer, upayload->data, buflen) != 0)
 207                        ret = -EFAULT;
 208        }
 209
 210        return ret;
 211}
 212
 213EXPORT_SYMBOL_GPL(user_read);
 214
 215/* Vet the description for a "logon" key */
 216static int logon_vet_description(const char *desc)
 217{
 218        char *p;
 219
 220        /* require a "qualified" description string */
 221        p = strchr(desc, ':');
 222        if (!p)
 223                return -EINVAL;
 224
 225        /* also reject description with ':' as first char */
 226        if (p == desc)
 227                return -EINVAL;
 228
 229        return 0;
 230}
 231
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