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, const void *data, size_t datalen)
  62{
  63        struct user_key_payload *upayload;
  64        int ret;
  65
  66        ret = -EINVAL;
  67        if (datalen <= 0 || datalen > 32767 || !data)
  68                goto error;
  69
  70        ret = key_payload_reserve(key, datalen);
  71        if (ret < 0)
  72                goto error;
  73
  74        ret = -ENOMEM;
  75        upayload = kmalloc(sizeof(*upayload) + datalen, GFP_KERNEL);
  76        if (!upayload)
  77                goto error;
  78
  79        /* attach the data */
  80        upayload->datalen = datalen;
  81        memcpy(upayload->data, data, datalen);
  82        rcu_assign_keypointer(key, upayload);
  83        ret = 0;
  84
  85error:
  86        return ret;
  87}
  88
  89EXPORT_SYMBOL_GPL(user_instantiate);
  90
  91/*
  92 * update a user defined key
  93 * - the key's semaphore is write-locked
  94 */
  95int user_update(struct key *key, const void *data, size_t datalen)
  96{
  97        struct user_key_payload *upayload, *zap;
  98        int ret;
  99
 100        ret = -EINVAL;
 101        if (datalen <= 0 || datalen > 32767 || !data)
 102                goto error;
 103
 104        /* construct a replacement payload */
 105        ret = -ENOMEM;
 106        upayload = kmalloc(sizeof(*upayload) + datalen, GFP_KERNEL);
 107        if (!upayload)
 108                goto error;
 109
 110        upayload->datalen = datalen;
 111        memcpy(upayload->data, data, datalen);
 112
 113        /* check the quota and attach the new data */
 114        zap = upayload;
 115
 116        ret = key_payload_reserve(key, datalen);
 117
 118        if (ret == 0) {
 119                /* attach the new data, displacing the old */
 120                zap = key->payload.data;
 121                rcu_assign_keypointer(key, upayload);
 122                key->expiry = 0;
 123        }
 124
 125        if (zap)
 126                kfree_rcu(zap, rcu);
 127
 128error:
 129        return ret;
 130}
 131
 132EXPORT_SYMBOL_GPL(user_update);
 133
 134/*
 135 * match users on their name
 136 */
 137int user_match(const struct key *key, const void *description)
 138{
 139        return strcmp(key->description, description) == 0;
 140}
 141
 142EXPORT_SYMBOL_GPL(user_match);
 143
 144/*
 145 * dispose of the links from a revoked keyring
 146 * - called with the key sem write-locked
 147 */
 148void user_revoke(struct key *key)
 149{
 150        struct user_key_payload *upayload = key->payload.data;
 151
 152        /* clear the quota */
 153        key_payload_reserve(key, 0);
 154
 155        if (upayload) {
 156                rcu_assign_keypointer(key, NULL);
 157                kfree_rcu(upayload, rcu);
 158        }
 159}
 160
 161EXPORT_SYMBOL(user_revoke);
 162
 163/*
 164 * dispose of the data dangling from the corpse of a user key
 165 */
 166void user_destroy(struct key *key)
 167{
 168        struct user_key_payload *upayload = key->payload.data;
 169
 170        kfree(upayload);
 171}
 172
 173EXPORT_SYMBOL_GPL(user_destroy);
 174
 175/*
 176 * describe the user key
 177 */
 178void user_describe(const struct key *key, struct seq_file *m)
 179{
 180        seq_puts(m, key->description);
 181        if (key_is_instantiated(key))
 182                seq_printf(m, ": %u", key->datalen);
 183}
 184
 185EXPORT_SYMBOL_GPL(user_describe);
 186
 187/*
 188 * read the key data
 189 * - the key's semaphore is read-locked
 190 */
 191long user_read(const struct key *key, char __user *buffer, size_t buflen)
 192{
 193        struct user_key_payload *upayload;
 194        long ret;
 195
 196        upayload = rcu_dereference_key(key);
 197        ret = upayload->datalen;
 198
 199        /* we can return the data as is */
 200        if (buffer && buflen > 0) {
 201                if (buflen > upayload->datalen)
 202                        buflen = upayload->datalen;
 203
 204                if (copy_to_user(buffer, upayload->data, buflen) != 0)
 205                        ret = -EFAULT;
 206        }
 207
 208        return ret;
 209}
 210
 211EXPORT_SYMBOL_GPL(user_read);
 212
 213/* Vet the description for a "logon" key */
 214static int logon_vet_description(const char *desc)
 215{
 216        char *p;
 217
 218        /* require a "qualified" description string */
 219        p = strchr(desc, ':');
 220        if (!p)
 221                return -EINVAL;
 222
 223        /* also reject description with ':' as first char */
 224        if (p == desc)
 225                return -EINVAL;
 226
 227        return 0;
 228}
 229
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