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         .update         = user_update,
  30         .match          = user_match,
  31         .revoke         = user_revoke,
  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  * dispose of the old data from an updated user defined key
  77  */
  78 static void user_update_rcu_disposal(struct rcu_head *rcu)
  79 {
  80         struct user_key_payload *upayload;
  81
  82         upayload = container_of(rcu, struct user_key_payload, rcu);
  83
  84         kfree(upayload);
  85
  86 } /* end user_update_rcu_disposal() */
  87
  88 /*****************************************************************************/
  89 /*
  90  * update a user defined key
  91  * - the key's semaphore is write-locked
  92  */
  93 int user_update(struct key *key, const void *data, size_t datalen)
  94 {
  95         struct user_key_payload *upayload, *zap;
  96         int ret;
  97
  98         ret = -EINVAL;
  99         if (datalen <= 0 || datalen > 32767 || !data)
 100                 goto error;
 101
 102         /* construct a replacement payload */
 103         ret = -ENOMEM;
 104         upayload = kmalloc(sizeof(*upayload) + datalen, GFP_KERNEL);
 105         if (!upayload)
 106                 goto error;
 107
 108         upayload->datalen = datalen;
 109         memcpy(upayload->data, data, datalen);
 110
 111         /* check the quota and attach the new data */
 112         zap = upayload;
 113
 114         ret = key_payload_reserve(key, datalen);
 115
 116         if (ret == 0) {
 117                 /* attach the new data, displacing the old */
 118                 zap = key->payload.data;
 119                 rcu_assign_pointer(key->payload.data, upayload);
 120                 key->expiry = 0;
 121         }
 122
 123         call_rcu(&zap->rcu, user_update_rcu_disposal);
 124
 125 error:
 126         return ret;
 127
 128 } /* end user_update() */
 129
 130 EXPORT_SYMBOL_GPL(user_update);
 131
 132 /*****************************************************************************/
 133 /*
 134  * match users on their name
 135  */
 136 int user_match(const struct key *key, const void *description)
 137 {
 138         return strcmp(key->description, description) == 0;
 139
 140 } /* end user_match() */
 141
 142 EXPORT_SYMBOL_GPL(user_match);
 143
 144 /*****************************************************************************/
 145 /*
 146  * dispose of the links from a revoked keyring
 147  * - called with the key sem write-locked
 148  */
 149 void user_revoke(struct key *key)
 150 {
 151         struct user_key_payload *upayload = key->payload.data;
 152
 153         /* clear the quota */
 154         key_payload_reserve(key, 0);
 155
 156         if (upayload) {
 157                 rcu_assign_pointer(key->payload.data, NULL);
 158                 call_rcu(&upayload->rcu, user_update_rcu_disposal);
 159         }
 160
 161 } /* end user_revoke() */
 162
 163 EXPORT_SYMBOL(user_revoke);
 164
 165 /*****************************************************************************/
 166 /*
 167  * dispose of the data dangling from the corpse of a user key
 168  */
 169 void user_destroy(struct key *key)
 170 {
 171         struct user_key_payload *upayload = key->payload.data;
 172
 173         kfree(upayload);
 174
 175 } /* end user_destroy() */
 176
 177 EXPORT_SYMBOL_GPL(user_destroy);
 178
 179 /*****************************************************************************/
 180 /*
 181  * describe the user key
 182  */
 183 void user_describe(const struct key *key, struct seq_file *m)
 184 {
 185         seq_puts(m, key->description);
 186
 187         seq_printf(m, ": %u", key->datalen);
 188
 189 } /* end user_describe() */
 190
 191 EXPORT_SYMBOL_GPL(user_describe);
 192
 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->payload.data);
 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 } /* end user_read() */
 218
 219 EXPORT_SYMBOL_GPL(user_read);