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  * instantiate a user defined key
  40  */
  41 int user_instantiate(struct key *key, const void *data, size_t datalen)
  42 {
  43         struct user_key_payload *upayload;
  44         int ret;
  45
  46         ret = -EINVAL;
  47         if (datalen <= 0 || datalen > 32767 || !data)
  48                 goto error;
  49
  50         ret = key_payload_reserve(key, datalen);
  51         if (ret < 0)
  52                 goto error;
  53
  54         ret = -ENOMEM;
  55         upayload = kmalloc(sizeof(*upayload) + datalen, GFP_KERNEL);
  56         if (!upayload)
  57                 goto error;
  58
  59         /* attach the data */
  60         upayload->datalen = datalen;
  61         memcpy(upayload->data, data, datalen);
  62         rcu_assign_pointer(key->payload.data, upayload);
  63         ret = 0;
  64
  65 error:
  66         return ret;
  67 }
  68
  69 EXPORT_SYMBOL_GPL(user_instantiate);
  70
  71 /*
  72  * update a user defined key
  73  * - the key's semaphore is write-locked
  74  */
  75 int user_update(struct key *key, const void *data, size_t datalen)
  76 {
  77         struct user_key_payload *upayload, *zap;
  78         int ret;
  79
  80         ret = -EINVAL;
  81         if (datalen <= 0 || datalen > 32767 || !data)
  82                 goto error;
  83
  84         /* construct a replacement payload */
  85         ret = -ENOMEM;
  86         upayload = kmalloc(sizeof(*upayload) + datalen, GFP_KERNEL);
  87         if (!upayload)
  88                 goto error;
  89
  90         upayload->datalen = datalen;
  91         memcpy(upayload->data, data, datalen);
  92
  93         /* check the quota and attach the new data */
  94         zap = upayload;
  95
  96         ret = key_payload_reserve(key, datalen);
  97
  98         if (ret == 0) {
  99                 /* attach the new data, displacing the old */
 100                 zap = key->payload.data;
 101                 rcu_assign_pointer(key->payload.data, upayload);
 102                 key->expiry = 0;
 103         }
 104
 105         if (zap)
 106                 kfree_rcu(zap, rcu);
 107
 108 error:
 109         return ret;
 110 }
 111
 112 EXPORT_SYMBOL_GPL(user_update);
 113
 114 /*
 115  * match users on their name
 116  */
 117 int user_match(const struct key *key, const void *description)
 118 {
 119         return strcmp(key->description, description) == 0;
 120 }
 121
 122 EXPORT_SYMBOL_GPL(user_match);
 123
 124 /*
 125  * dispose of the links from a revoked keyring
 126  * - called with the key sem write-locked
 127  */
 128 void user_revoke(struct key *key)
 129 {
 130         struct user_key_payload *upayload = key->payload.data;
 131
 132         /* clear the quota */
 133         key_payload_reserve(key, 0);
 134
 135         if (upayload) {
 136                 rcu_assign_pointer(key->payload.data, NULL);
 137                 kfree_rcu(upayload, rcu);
 138         }
 139 }
 140
 141 EXPORT_SYMBOL(user_revoke);
 142
 143 /*
 144  * dispose of the data dangling from the corpse of a user key
 145  */
 146 void user_destroy(struct key *key)
 147 {
 148         struct user_key_payload *upayload = key->payload.data;
 149
 150         kfree(upayload);
 151 }
 152
 153 EXPORT_SYMBOL_GPL(user_destroy);
 154
 155 /*
 156  * describe the user key
 157  */
 158 void user_describe(const struct key *key, struct seq_file *m)
 159 {
 160         seq_puts(m, key->description);
 161         if (key_is_instantiated(key))
 162                 seq_printf(m, ": %u", key->datalen);
 163 }
 164
 165 EXPORT_SYMBOL_GPL(user_describe);
 166
 167 /*
 168  * read the key data
 169  * - the key's semaphore is read-locked
 170  */
 171 long user_read(const struct key *key, char __user *buffer, size_t buflen)
 172 {
 173         struct user_key_payload *upayload;
 174         long ret;
 175
 176         upayload = rcu_dereference_key(key);
 177         ret = upayload->datalen;
 178
 179         /* we can return the data as is */
 180         if (buffer && buflen > 0) {
 181                 if (buflen > upayload->datalen)
 182                         buflen = upayload->datalen;
 183
 184                 if (copy_to_user(buffer, upayload->data, buflen) != 0)
 185                         ret = -EFAULT;
 186         }
 187
 188         return ret;
 189 }
 190
 191 EXPORT_SYMBOL_GPL(user_read);