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  * dispose of the old data from an updated user defined key
  73  */
  74 static void user_update_rcu_disposal(struct rcu_head *rcu)
  75 {
  76         struct user_key_payload *upayload;
  77
  78         upayload = container_of(rcu, struct user_key_payload, rcu);
  79
  80         kfree(upayload);
  81 }
  82
  83 /*
  84  * update a user defined key
  85  * - the key's semaphore is write-locked
  86  */
  87 int user_update(struct key *key, const void *data, size_t datalen)
  88 {
  89         struct user_key_payload *upayload, *zap;
  90         int ret;
  91
  92         ret = -EINVAL;
  93         if (datalen <= 0 || datalen > 32767 || !data)
  94                 goto error;
  95
  96         /* construct a replacement payload */
  97         ret = -ENOMEM;
  98         upayload = kmalloc(sizeof(*upayload) + datalen, GFP_KERNEL);
  99         if (!upayload)
 100                 goto error;
 101
 102         upayload->datalen = datalen;
 103         memcpy(upayload->data, data, datalen);
 104
 105         /* check the quota and attach the new data */
 106         zap = upayload;
 107
 108         ret = key_payload_reserve(key, datalen);
 109
 110         if (ret == 0) {
 111                 /* attach the new data, displacing the old */
 112                 zap = key->payload.data;
 113                 rcu_assign_pointer(key->payload.data, upayload);
 114                 key->expiry = 0;
 115         }
 116
 117         call_rcu(&zap->rcu, user_update_rcu_disposal);
 118
 119 error:
 120         return ret;
 121 }
 122
 123 EXPORT_SYMBOL_GPL(user_update);
 124
 125 /*
 126  * match users on their name
 127  */
 128 int user_match(const struct key *key, const void *description)
 129 {
 130         return strcmp(key->description, description) == 0;
 131 }
 132
 133 EXPORT_SYMBOL_GPL(user_match);
 134
 135 /*
 136  * dispose of the links from a revoked keyring
 137  * - called with the key sem write-locked
 138  */
 139 void user_revoke(struct key *key)
 140 {
 141         struct user_key_payload *upayload = key->payload.data;
 142
 143         /* clear the quota */
 144         key_payload_reserve(key, 0);
 145
 146         if (upayload) {
 147                 rcu_assign_pointer(key->payload.data, NULL);
 148                 call_rcu(&upayload->rcu, user_update_rcu_disposal);
 149         }
 150 }
 151
 152 EXPORT_SYMBOL(user_revoke);
 153
 154 /*
 155  * dispose of the data dangling from the corpse of a user key
 156  */
 157 void user_destroy(struct key *key)
 158 {
 159         struct user_key_payload *upayload = key->payload.data;
 160
 161         kfree(upayload);
 162 }
 163
 164 EXPORT_SYMBOL_GPL(user_destroy);
 165
 166 /*
 167  * describe the user key
 168  */
 169 void user_describe(const struct key *key, struct seq_file *m)
 170 {
 171         seq_puts(m, key->description);
 172
 173         seq_printf(m, ": %u", key->datalen);
 174 }
 175
 176 EXPORT_SYMBOL_GPL(user_describe);
 177
 178 /*
 179  * read the key data
 180  * - the key's semaphore is read-locked
 181  */
 182 long user_read(const struct key *key, char __user *buffer, size_t buflen)
 183 {
 184         struct user_key_payload *upayload;
 185         long ret;
 186
 187         upayload = rcu_dereference_key(key);
 188         ret = upayload->datalen;
 189
 190         /* we can return the data as is */
 191         if (buffer && buflen > 0) {
 192                 if (buflen > upayload->datalen)
 193                         buflen = upayload->datalen;
 194
 195                 if (copy_to_user(buffer, upayload->data, buflen) != 0)
 196                         ret = -EFAULT;
 197         }
 198
 199         return ret;
 200 }
 201
 202 EXPORT_SYMBOL_GPL(user_read);