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