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         .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 EXPORT_SYMBOL_GPL(user_instantiate);
  71
  72 /*****************************************************************************/
  73 /*
  74  * dispose of the old data from an updated user defined key
  75  */
  76 static void user_update_rcu_disposal(struct rcu_head *rcu)
  77 {
  78         struct user_key_payload *upayload;
  79
  80         upayload = container_of(rcu, struct user_key_payload, rcu);
  81
  82         kfree(upayload);
  83
  84 } /* end user_update_rcu_disposal() */
  85
  86 /*****************************************************************************/
  87 /*
  88  * update a user defined key
  89  * - the key's semaphore is write-locked
  90  */
  91 int user_update(struct key *key, const void *data, size_t datalen)
  92 {
  93         struct user_key_payload *upayload, *zap;
  94         int ret;
  95
  96         ret = -EINVAL;
  97         if (datalen <= 0 || datalen > 32767 || !data)
  98                 goto error;
  99
 100         /* construct a replacement payload */
 101         ret = -ENOMEM;
 102         upayload = kmalloc(sizeof(*upayload) + datalen, GFP_KERNEL);
 103         if (!upayload)
 104                 goto error;
 105
 106         upayload->datalen = datalen;
 107         memcpy(upayload->data, data, datalen);
 108
 109         /* check the quota and attach the new data */
 110         zap = upayload;
 111
 112         ret = key_payload_reserve(key, datalen);
 113
 114         if (ret == 0) {
 115                 /* attach the new data, displacing the old */
 116                 zap = key->payload.data;
 117                 rcu_assign_pointer(key->payload.data, upayload);
 118                 key->expiry = 0;
 119         }
 120
 121         call_rcu(&zap->rcu, user_update_rcu_disposal);
 122
 123 error:
 124         return ret;
 125
 126 } /* end user_update() */
 127
 128 EXPORT_SYMBOL_GPL(user_update);
 129
 130 /*****************************************************************************/
 131 /*
 132  * match users on their name
 133  */
 134 int user_match(const struct key *key, const void *description)
 135 {
 136         return strcmp(key->description, description) == 0;
 137
 138 } /* end user_match() */
 139
 140 EXPORT_SYMBOL_GPL(user_match);
 141
 142 /*****************************************************************************/
 143 /*
 144  * dispose of the data dangling from the corpse of a user
 145  */
 146 void user_destroy(struct key *key)
 147 {
 148         struct user_key_payload *upayload = key->payload.data;
 149
 150         kfree(upayload);
 151
 152 } /* end user_destroy() */
 153
 154 EXPORT_SYMBOL_GPL(user_destroy);
 155
 156 /*****************************************************************************/
 157 /*
 158  * describe the user key
 159  */
 160 void user_describe(const struct key *key, struct seq_file *m)
 161 {
 162         seq_puts(m, key->description);
 163
 164         seq_printf(m, ": %u", key->datalen);
 165
 166 } /* end user_describe() */
 167
 168 EXPORT_SYMBOL_GPL(user_describe);
 169
 170 /*****************************************************************************/
 171 /*
 172  * read the key data
 173  * - the key's semaphore is read-locked
 174  */
 175 long user_read(const struct key *key, char __user *buffer, size_t buflen)
 176 {
 177         struct user_key_payload *upayload;
 178         long ret;
 179
 180         upayload = rcu_dereference(key->payload.data);
 181         ret = upayload->datalen;
 182
 183         /* we can return the data as is */
 184         if (buffer && buflen > 0) {
 185                 if (buflen > upayload->datalen)
 186                         buflen = upayload->datalen;
 187
 188                 if (copy_to_user(buffer, upayload->data, buflen) != 0)
 189                         ret = -EFAULT;
 190         }
 191
 192         return ret;
 193
 194 } /* end user_read() */
 195
 196 EXPORT_SYMBOL_GPL(user_read);