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         kfree_rcu(zap, rcu);
 106
 107 error:
 108         return ret;
 109 }
 110
 111 EXPORT_SYMBOL_GPL(user_update);
 112
 113 /*
 114  * match users on their name
 115  */
 116 int user_match(const struct key *key, const void *description)
 117 {
 118         return strcmp(key->description, description) == 0;
 119 }
 120
 121 EXPORT_SYMBOL_GPL(user_match);
 122
 123 /*
 124  * dispose of the links from a revoked keyring
 125  * - called with the key sem write-locked
 126  */
 127 void user_revoke(struct key *key)
 128 {
 129         struct user_key_payload *upayload = key->payload.data;
 130
 131         /* clear the quota */
 132         key_payload_reserve(key, 0);
 133
 134         if (upayload) {
 135                 rcu_assign_pointer(key->payload.data, NULL);
 136                 kfree_rcu(upayload, rcu);
 137         }
 138 }
 139
 140 EXPORT_SYMBOL(user_revoke);
 141
 142 /*
 143  * dispose of the data dangling from the corpse of a user key
 144  */
 145 void user_destroy(struct key *key)
 146 {
 147         struct user_key_payload *upayload = key->payload.data;
 148
 149         kfree(upayload);
 150 }
 151
 152 EXPORT_SYMBOL_GPL(user_destroy);
 153
 154 /*
 155  * describe the user key
 156  */
 157 void user_describe(const struct key *key, struct seq_file *m)
 158 {
 159         seq_puts(m, key->description);
 160         if (key_is_instantiated(key))
 161                 seq_printf(m, ": %u", key->datalen);
 162 }
 163
 164 EXPORT_SYMBOL_GPL(user_describe);
 165
 166 /*
 167  * read the key data
 168  * - the key's semaphore is read-locked
 169  */
 170 long user_read(const struct key *key, char __user *buffer, size_t buflen)
 171 {
 172         struct user_key_payload *upayload;
 173         long ret;
 174
 175         upayload = rcu_dereference_key(key);
 176         ret = upayload->datalen;
 177
 178         /* we can return the data as is */
 179         if (buffer && buflen > 0) {
 180                 if (buflen > upayload->datalen)
 181                         buflen = upayload->datalen;
 182
 183                 if (copy_to_user(buffer, upayload->data, buflen) != 0)
 184                         ret = -EFAULT;
 185         }
 186
 187         return ret;
 188 }
 189
 190 EXPORT_SYMBOL_GPL(user_read);