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/sched.h>
  15 #include <linux/slab.h>
  16 #include <linux/seq_file.h>
  17 #include <linux/err.h>
  18 #include <asm/uaccess.h>
  19 #include "internal.h"
  20
  21 static int user_instantiate(struct key *key, const void *data, size_t datalen);
  22 static int user_duplicate(struct key *key, const struct key *source);
  23 static int user_update(struct key *key, const void *data, size_t datalen);
  24 static int user_match(const struct key *key, const void *criterion);
  25 static void user_destroy(struct key *key);
  26 static void user_describe(const struct key *user, struct seq_file *m);
  27 static long user_read(const struct key *key,
  28                       char __user *buffer, size_t buflen);
  29
  30 /*
  31  * user defined keys take an arbitrary string as the description and an
  32  * arbitrary blob of data as the payload
  33  */
  34 struct key_type key_type_user = {
  35         .name           = "user",
  36         .instantiate    = user_instantiate,
  37         .duplicate      = user_duplicate,
  38         .update         = user_update,
  39         .match          = user_match,
  40         .destroy        = user_destroy,
  41         .describe       = user_describe,
  42         .read           = user_read,
  43 };
  44
  45 struct user_key_payload {
  46         struct rcu_head rcu;            /* RCU destructor */
  47         unsigned short  datalen;        /* length of this data */
  48         char            data[0];        /* actual data */
  49 };
  50
  51 EXPORT_SYMBOL_GPL(key_type_user);
  52
  53 /*****************************************************************************/
  54 /*
  55  * instantiate a user defined key
  56  */
  57 static int user_instantiate(struct key *key, const void *data, size_t datalen)
  58 {
  59         struct user_key_payload *upayload;
  60         int ret;
  61
  62         ret = -EINVAL;
  63         if (datalen <= 0 || datalen > 32767 || !data)
  64                 goto error;
  65
  66         ret = key_payload_reserve(key, datalen);
  67         if (ret < 0)
  68                 goto error;
  69
  70         ret = -ENOMEM;
  71         upayload = kmalloc(sizeof(*upayload) + datalen, GFP_KERNEL);
  72         if (!upayload)
  73                 goto error;
  74
  75         /* attach the data */
  76         upayload->datalen = datalen;
  77         memcpy(upayload->data, data, datalen);
  78         rcu_assign_pointer(key->payload.data, upayload);
  79         ret = 0;
  80
  81  error:
  82         return ret;
  83
  84 } /* end user_instantiate() */
  85
  86 /*****************************************************************************/
  87 /*
  88  * duplicate a user defined key
  89  * - both keys' semaphores are locked against further modification
  90  * - the new key cannot yet be accessed
  91  */
  92 static int user_duplicate(struct key *key, const struct key *source)
  93 {
  94         struct user_key_payload *upayload, *spayload;
  95         int ret;
  96
  97         /* just copy the payload */
  98         ret = -ENOMEM;
  99         upayload = kmalloc(sizeof(*upayload) + source->datalen, GFP_KERNEL);
 100         if (upayload) {
 101                 spayload = rcu_dereference(source->payload.data);
 102                 BUG_ON(source->datalen != spayload->datalen);
 103
 104                 upayload->datalen = key->datalen = spayload->datalen;
 105                 memcpy(upayload->data, spayload->data, key->datalen);
 106
 107                 key->payload.data = upayload;
 108                 ret = 0;
 109         }
 110
 111         return ret;
 112
 113 } /* end user_duplicate() */
 114
 115 /*****************************************************************************/
 116 /*
 117  * dispose of the old data from an updated user defined key
 118  */
 119 static void user_update_rcu_disposal(struct rcu_head *rcu)
 120 {
 121         struct user_key_payload *upayload;
 122
 123         upayload = container_of(rcu, struct user_key_payload, rcu);
 124
 125         kfree(upayload);
 126
 127 } /* end user_update_rcu_disposal() */
 128
 129 /*****************************************************************************/
 130 /*
 131  * update a user defined key
 132  * - the key's semaphore is write-locked
 133  */
 134 static int user_update(struct key *key, const void *data, size_t datalen)
 135 {
 136         struct user_key_payload *upayload, *zap;
 137         int ret;
 138
 139         ret = -EINVAL;
 140         if (datalen <= 0 || datalen > 32767 || !data)
 141                 goto error;
 142
 143         /* construct a replacement payload */
 144         ret = -ENOMEM;
 145         upayload = kmalloc(sizeof(*upayload) + datalen, GFP_KERNEL);
 146         if (!upayload)
 147                 goto error;
 148
 149         upayload->datalen = datalen;
 150         memcpy(upayload->data, data, datalen);
 151
 152         /* check the quota and attach the new data */
 153         zap = upayload;
 154
 155         ret = key_payload_reserve(key, datalen);
 156
 157         if (ret == 0) {
 158                 /* attach the new data, displacing the old */
 159                 zap = key->payload.data;
 160                 rcu_assign_pointer(key->payload.data, upayload);
 161                 key->expiry = 0;
 162         }
 163
 164         call_rcu(&zap->rcu, user_update_rcu_disposal);
 165
 166  error:
 167         return ret;
 168
 169 } /* end user_update() */
 170
 171 /*****************************************************************************/
 172 /*
 173  * match users on their name
 174  */
 175 static int user_match(const struct key *key, const void *description)
 176 {
 177         return strcmp(key->description, description) == 0;
 178
 179 } /* end user_match() */
 180
 181 /*****************************************************************************/
 182 /*
 183  * dispose of the data dangling from the corpse of a user
 184  */
 185 static void user_destroy(struct key *key)
 186 {
 187         struct user_key_payload *upayload = key->payload.data;
 188
 189         kfree(upayload);
 190
 191 } /* end user_destroy() */
 192
 193 /*****************************************************************************/
 194 /*
 195  * describe the user key
 196  */
 197 static void user_describe(const struct key *key, struct seq_file *m)
 198 {
 199         seq_puts(m, key->description);
 200
 201         seq_printf(m, ": %u", key->datalen);
 202
 203 } /* end user_describe() */
 204
 205 /*****************************************************************************/
 206 /*
 207  * read the key data
 208  * - the key's semaphore is read-locked
 209  */
 210 static long user_read(const struct key *key,
 211                       char __user *buffer, size_t buflen)
 212 {
 213         struct user_key_payload *upayload;
 214         long ret;
 215
 216         upayload = rcu_dereference(key->payload.data);
 217         ret = upayload->datalen;
 218
 219         /* we can return the data as is */
 220         if (buffer && buflen > 0) {
 221                 if (buflen > upayload->datalen)
 222                         buflen = upayload->datalen;
 223
 224                 if (copy_to_user(buffer, upayload->data, buflen) != 0)
 225                         ret = -EFAULT;
 226         }
 227
 228         return ret;
 229
 230 } /* end user_read() */