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 /*
  22  * user defined keys take an arbitrary string as the description and an
  23  * arbitrary blob of data as the payload
  24  */
  25 struct key_type key_type_user = {
  26         .name           = "user",
  27         .instantiate    = user_instantiate,
  28         .update         = user_update,
  29         .match          = user_match,
  30         .revoke         = user_revoke,
  31         .destroy        = user_destroy,
  32         .describe       = user_describe,
  33         .read           = user_read,
  34 };
  35
  36 EXPORT_SYMBOL_GPL(key_type_user);
  37
  38 /*****************************************************************************/
  39 /*
  40  * instantiate a user defined key
  41  */
  42 int user_instantiate(struct key *key, const void *data, size_t datalen)
  43 {
  44         struct user_key_payload *upayload;
  45         int ret;
  46
  47         ret = -EINVAL;
  48         if (datalen <= 0 || datalen > 32767 || !data)
  49                 goto error;
  50
  51         ret = key_payload_reserve(key, datalen);
  52         if (ret < 0)
  53                 goto error;
  54
  55         ret = -ENOMEM;
  56         upayload = kmalloc(sizeof(*upayload) + datalen, GFP_KERNEL);
  57         if (!upayload)
  58                 goto error;
  59
  60         /* attach the data */
  61         upayload->datalen = datalen;
  62         memcpy(upayload->data, data, datalen);
  63         rcu_assign_pointer(key->payload.data, upayload);
  64         ret = 0;
  65
  66 error:
  67         return ret;
  68
  69 } /* end user_instantiate() */
  70
  71 EXPORT_SYMBOL_GPL(user_instantiate);
  72
  73 /*****************************************************************************/
  74 /*
  75  * dispose of the old data from an updated user defined key
  76  */
  77 static void user_update_rcu_disposal(struct rcu_head *rcu)
  78 {
  79         struct user_key_payload *upayload;
  80
  81         upayload = container_of(rcu, struct user_key_payload, rcu);
  82
  83         kfree(upayload);
  84
  85 } /* end user_update_rcu_disposal() */
  86
  87 /*****************************************************************************/
  88 /*
  89  * update a user defined key
  90  * - the key's semaphore is write-locked
  91  */
  92 int user_update(struct key *key, const void *data, size_t datalen)
  93 {
  94         struct user_key_payload *upayload, *zap;
  95         int ret;
  96
  97         ret = -EINVAL;
  98         if (datalen <= 0 || datalen > 32767 || !data)
  99                 goto error;
 100
 101         /* construct a replacement payload */
 102         ret = -ENOMEM;
 103         upayload = kmalloc(sizeof(*upayload) + datalen, GFP_KERNEL);
 104         if (!upayload)
 105                 goto error;
 106
 107         upayload->datalen = datalen;
 108         memcpy(upayload->data, data, datalen);
 109
 110         /* check the quota and attach the new data */
 111         zap = upayload;
 112
 113         ret = key_payload_reserve(key, datalen);
 114
 115         if (ret == 0) {
 116                 /* attach the new data, displacing the old */
 117                 zap = key->payload.data;
 118                 rcu_assign_pointer(key->payload.data, upayload);
 119                 key->expiry = 0;
 120         }
 121
 122         call_rcu(&zap->rcu, user_update_rcu_disposal);
 123
 124 error:
 125         return ret;
 126
 127 } /* end user_update() */
 128
 129 EXPORT_SYMBOL_GPL(user_update);
 130
 131 /*****************************************************************************/
 132 /*
 133  * match users on their name
 134  */
 135 int user_match(const struct key *key, const void *description)
 136 {
 137         return strcmp(key->description, description) == 0;
 138
 139 } /* end user_match() */
 140
 141 EXPORT_SYMBOL_GPL(user_match);
 142
 143 /*****************************************************************************/
 144 /*
 145  * dispose of the links from a revoked keyring
 146  * - called with the key sem write-locked
 147  */
 148 void 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_pointer(key->payload.data, NULL);
 157                 call_rcu(&upayload->rcu, user_update_rcu_disposal);
 158         }
 159
 160 } /* end user_revoke() */
 161
 162 EXPORT_SYMBOL(user_revoke);
 163
 164 /*****************************************************************************/
 165 /*
 166  * dispose of the data dangling from the corpse of a user key
 167  */
 168 void user_destroy(struct key *key)
 169 {
 170         struct user_key_payload *upayload = key->payload.data;
 171
 172         kfree(upayload);
 173
 174 } /* end user_destroy() */
 175
 176 EXPORT_SYMBOL_GPL(user_destroy);
 177
 178 /*****************************************************************************/
 179 /*
 180  * describe the user key
 181  */
 182 void user_describe(const struct key *key, struct seq_file *m)
 183 {
 184         seq_puts(m, key->description);
 185
 186         seq_printf(m, ": %u", key->datalen);
 187
 188 } /* end user_describe() */
 189
 190 EXPORT_SYMBOL_GPL(user_describe);
 191
 192 /*****************************************************************************/
 193 /*
 194  * read the key data
 195  * - the key's semaphore is read-locked
 196  */
 197 long user_read(const struct key *key, char __user *buffer, size_t buflen)
 198 {
 199         struct user_key_payload *upayload;
 200         long ret;
 201
 202         upayload = rcu_dereference_protected(
 203                 key->payload.data, rwsem_is_locked(&((struct key *)key)->sem));
 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);