security/keys/user_defined.c

   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
  21 static 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  */
  27 struct key_type key_type_user = {
  28         .name                   = "user",
  29         .def_lookup_type        = KEYRING_SEARCH_LOOKUP_DIRECT,
  30         .preparse               = user_preparse,
  31         .free_preparse          = user_free_preparse,
  32         .instantiate            = generic_key_instantiate,
  33         .update                 = user_update,
  34         .match                  = user_match,
  35         .revoke                 = user_revoke,
  36         .destroy                = user_destroy,
  37         .describe               = user_describe,
  38         .read                   = user_read,
  39 };
  40
  41 EXPORT_SYMBOL_GPL(key_type_user);
  42
  43 /*
  44  * This key type is essentially the same as key_type_user, but it does
  45  * not define a .read op. This is suitable for storing username and
  46  * password pairs in the keyring that you do not want to be readable
  47  * from userspace.
  48  */
  49 struct key_type key_type_logon = {
  50         .name                   = "logon",
  51         .def_lookup_type        = KEYRING_SEARCH_LOOKUP_DIRECT,
  52         .preparse               = user_preparse,
  53         .free_preparse          = user_free_preparse,
  54         .instantiate            = generic_key_instantiate,
  55         .update                 = user_update,
  56         .match                  = user_match,
  57         .revoke                 = user_revoke,
  58         .destroy                = user_destroy,
  59         .describe               = user_describe,
  60         .vet_description        = logon_vet_description,
  61 };
  62 EXPORT_SYMBOL_GPL(key_type_logon);
  63
  64 /*
  65  * Preparse a user defined key payload
  66  */
  67 int user_preparse(struct key_preparsed_payload *prep)
  68 {
  69         struct user_key_payload *upayload;
  70         size_t datalen = prep->datalen;
  71
  72         if (datalen <= 0 || datalen > 32767 || !prep->data)
  73                 return -EINVAL;
  74
  75         upayload = kmalloc(sizeof(*upayload) + datalen, GFP_KERNEL);
  76         if (!upayload)
  77                 return -ENOMEM;
  78
  79         /* attach the data */
  80         prep->quotalen = datalen;
  81         prep->payload[0] = upayload;
  82         upayload->datalen = datalen;
  83         memcpy(upayload->data, prep->data, datalen);
  84         return 0;
  85 }
  86 EXPORT_SYMBOL_GPL(user_preparse);
  87
  88 /*
  89  * Free a preparse of a user defined key payload
  90  */
  91 void user_free_preparse(struct key_preparsed_payload *prep)
  92 {
  93         kfree(prep->payload[0]);
  94 }
  95 EXPORT_SYMBOL_GPL(user_free_preparse);
  96
  97 /*
  98  * update a user defined key
  99  * - the key's semaphore is write-locked
 100  */
 101 int user_update(struct key *key, struct key_preparsed_payload *prep)
 102 {
 103         struct user_key_payload *upayload, *zap;
 104         size_t datalen = prep->datalen;
 105         int ret;
 106
 107         ret = -EINVAL;
 108         if (datalen <= 0 || datalen > 32767 || !prep->data)
 109                 goto error;
 110
 111         /* construct a replacement payload */
 112         ret = -ENOMEM;
 113         upayload = kmalloc(sizeof(*upayload) + datalen, GFP_KERNEL);
 114         if (!upayload)
 115                 goto error;
 116
 117         upayload->datalen = datalen;
 118         memcpy(upayload->data, prep->data, datalen);
 119
 120         /* check the quota and attach the new data */
 121         zap = upayload;
 122
 123         ret = key_payload_reserve(key, datalen);
 124
 125         if (ret == 0) {
 126                 /* attach the new data, displacing the old */
 127                 zap = key->payload.data;
 128                 rcu_assign_keypointer(key, upayload);
 129                 key->expiry = 0;
 130         }
 131
 132         if (zap)
 133                 kfree_rcu(zap, rcu);
 134
 135 error:
 136         return ret;
 137 }
 138
 139 EXPORT_SYMBOL_GPL(user_update);
 140
 141 /*
 142  * match users on their name
 143  */
 144 int user_match(const struct key *key, const void *description)
 145 {
 146         return strcmp(key->description, description) == 0;
 147 }
 148
 149 EXPORT_SYMBOL_GPL(user_match);
 150
 151 /*
 152  * dispose of the links from a revoked keyring
 153  * - called with the key sem write-locked
 154  */
 155 void user_revoke(struct key *key)
 156 {
 157         struct user_key_payload *upayload = key->payload.data;
 158
 159         /* clear the quota */
 160         key_payload_reserve(key, 0);
 161
 162         if (upayload) {
 163                 rcu_assign_keypointer(key, NULL);
 164                 kfree_rcu(upayload, rcu);
 165         }
 166 }
 167
 168 EXPORT_SYMBOL(user_revoke);
 169
 170 /*
 171  * dispose of the data dangling from the corpse of a user key
 172  */
 173 void user_destroy(struct key *key)
 174 {
 175         struct user_key_payload *upayload = key->payload.data;
 176
 177         kfree(upayload);
 178 }
 179
 180 EXPORT_SYMBOL_GPL(user_destroy);
 181
 182 /*
 183  * describe the user key
 184  */
 185 void user_describe(const struct key *key, struct seq_file *m)
 186 {
 187         seq_puts(m, key->description);
 188         if (key_is_instantiated(key))
 189                 seq_printf(m, ": %u", key->datalen);
 190 }
 191
 192 EXPORT_SYMBOL_GPL(user_describe);
 193
 194 /*
 195  * read the key data
 196  * - the key's semaphore is read-locked
 197  */
 198 long user_read(const struct key *key, char __user *buffer, size_t buflen)
 199 {
 200         struct user_key_payload *upayload;
 201         long ret;
 202
 203         upayload = rcu_dereference_key(key);
 204         ret = upayload->datalen;
 205
 206         /* we can return the data as is */
 207         if (buffer && buflen > 0) {
 208                 if (buflen > upayload->datalen)
 209                         buflen = upayload->datalen;
 210
 211                 if (copy_to_user(buffer, upayload->data, buflen) != 0)
 212                         ret = -EFAULT;
 213         }
 214
 215         return ret;
 216 }
 217
 218 EXPORT_SYMBOL_GPL(user_read);
 219
 220 /* Vet the description for a "logon" key */
 221 static int logon_vet_description(const char *desc)
 222 {
 223         char *p;
 224
 225         /* require a "qualified" description string */
 226         p = strchr(desc, ':');
 227         if (!p)
 228                 return -EINVAL;
 229
 230         /* also reject description with ':' as first char */
 231         if (p == desc)
 232                 return -EINVAL;
 233
 234         return 0;
 235 }