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 static int logon_vet_description(const char *desc);
  22
  23 /*
  24  * user defined keys take an arbitrary string as the description and an
  25  * arbitrary blob of data as the payload
  26  */
  27 struct key_type key_type_user = {
  28         .name           = "user",
  29         .instantiate    = user_instantiate,
  30         .update         = user_update,
  31         .match          = user_match,
  32         .revoke         = user_revoke,
  33         .destroy        = user_destroy,
  34         .describe       = user_describe,
  35         .read           = user_read,
  36 };
  37
  38 EXPORT_SYMBOL_GPL(key_type_user);
  39
  40 /*
  41  * This key type is essentially the same as key_type_user, but it does
  42  * not define a .read op. This is suitable for storing username and
  43  * password pairs in the keyring that you do not want to be readable
  44  * from userspace.
  45  */
  46 struct key_type key_type_logon = {
  47         .name                   = "logon",
  48         .instantiate            = user_instantiate,
  49         .update                 = user_update,
  50         .match                  = user_match,
  51         .revoke                 = user_revoke,
  52         .destroy                = user_destroy,
  53         .describe               = user_describe,
  54         .vet_description        = logon_vet_description,
  55 };
  56 EXPORT_SYMBOL_GPL(key_type_logon);
  57
  58 /*
  59  * instantiate a user defined key
  60  */
  61 int user_instantiate(struct key *key, struct key_preparsed_payload *prep)
  62 {
  63         struct user_key_payload *upayload;
  64         size_t datalen = prep->datalen;
  65         int ret;
  66
  67         ret = -EINVAL;
  68         if (datalen <= 0 || datalen > 32767 || !prep->data)
  69                 goto error;
  70
  71         ret = key_payload_reserve(key, datalen);
  72         if (ret < 0)
  73                 goto error;
  74
  75         ret = -ENOMEM;
  76         upayload = kmalloc(sizeof(*upayload) + datalen, GFP_KERNEL);
  77         if (!upayload)
  78                 goto error;
  79
  80         /* attach the data */
  81         upayload->datalen = datalen;
  82         memcpy(upayload->data, prep->data, datalen);
  83         rcu_assign_keypointer(key, upayload);
  84         ret = 0;
  85
  86 error:
  87         return ret;
  88 }
  89
  90 EXPORT_SYMBOL_GPL(user_instantiate);
  91
  92 /*
  93  * update a user defined key
  94  * - the key's semaphore is write-locked
  95  */
  96 int user_update(struct key *key, struct key_preparsed_payload *prep)
  97 {
  98         struct user_key_payload *upayload, *zap;
  99         size_t datalen = prep->datalen;
 100         int ret;
 101
 102         ret = -EINVAL;
 103         if (datalen <= 0 || datalen > 32767 || !prep->data)
 104                 goto error;
 105
 106         /* construct a replacement payload */
 107         ret = -ENOMEM;
 108         upayload = kmalloc(sizeof(*upayload) + datalen, GFP_KERNEL);
 109         if (!upayload)
 110                 goto error;
 111
 112         upayload->datalen = datalen;
 113         memcpy(upayload->data, prep->data, datalen);
 114
 115         /* check the quota and attach the new data */
 116         zap = upayload;
 117
 118         ret = key_payload_reserve(key, datalen);
 119
 120         if (ret == 0) {
 121                 /* attach the new data, displacing the old */
 122                 zap = key->payload.data;
 123                 rcu_assign_keypointer(key, upayload);
 124                 key->expiry = 0;
 125         }
 126
 127         if (zap)
 128                 kfree_rcu(zap, rcu);
 129
 130 error:
 131         return ret;
 132 }
 133
 134 EXPORT_SYMBOL_GPL(user_update);
 135
 136 /*
 137  * match users on their name
 138  */
 139 int user_match(const struct key *key, const void *description)
 140 {
 141         return strcmp(key->description, description) == 0;
 142 }
 143
 144 EXPORT_SYMBOL_GPL(user_match);
 145
 146 /*
 147  * dispose of the links from a revoked keyring
 148  * - called with the key sem write-locked
 149  */
 150 void user_revoke(struct key *key)
 151 {
 152         struct user_key_payload *upayload = key->payload.data;
 153
 154         /* clear the quota */
 155         key_payload_reserve(key, 0);
 156
 157         if (upayload) {
 158                 rcu_assign_keypointer(key, NULL);
 159                 kfree_rcu(upayload, rcu);
 160         }
 161 }
 162
 163 EXPORT_SYMBOL(user_revoke);
 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
 175 EXPORT_SYMBOL_GPL(user_destroy);
 176
 177 /*
 178  * describe the user key
 179  */
 180 void user_describe(const struct key *key, struct seq_file *m)
 181 {
 182         seq_puts(m, key->description);
 183         if (key_is_instantiated(key))
 184                 seq_printf(m, ": %u", key->datalen);
 185 }
 186
 187 EXPORT_SYMBOL_GPL(user_describe);
 188
 189 /*
 190  * read the key data
 191  * - the key's semaphore is read-locked
 192  */
 193 long user_read(const struct key *key, char __user *buffer, size_t buflen)
 194 {
 195         struct user_key_payload *upayload;
 196         long ret;
 197
 198         upayload = rcu_dereference_key(key);
 199         ret = upayload->datalen;
 200
 201         /* we can return the data as is */
 202         if (buffer && buflen > 0) {
 203                 if (buflen > upayload->datalen)
 204                         buflen = upayload->datalen;
 205
 206                 if (copy_to_user(buffer, upayload->data, buflen) != 0)
 207                         ret = -EFAULT;
 208         }
 209
 210         return ret;
 211 }
 212
 213 EXPORT_SYMBOL_GPL(user_read);
 214
 215 /* Vet the description for a "logon" key */
 216 static int logon_vet_description(const char *desc)
 217 {
 218         char *p;
 219
 220         /* require a "qualified" description string */
 221         p = strchr(desc, ':');
 222         if (!p)
 223                 return -EINVAL;
 224
 225         /* also reject description with ':' as first char */
 226         if (p == desc)
 227                 return -EINVAL;
 228
 229         return 0;
 230 }