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         .preparse               = user_preparse,
  30         .free_preparse          = user_free_preparse,
  31         .instantiate            = generic_key_instantiate,
  32         .update                 = user_update,
  33         .revoke                 = user_revoke,
  34         .destroy                = user_destroy,
  35         .describe               = user_describe,
  36         .read                   = user_read,
  37 };
  38
  39 EXPORT_SYMBOL_GPL(key_type_user);
  40
  41 /*
  42  * This key type is essentially the same as key_type_user, but it does
  43  * not define a .read op. This is suitable for storing username and
  44  * password pairs in the keyring that you do not want to be readable
  45  * from userspace.
  46  */
  47 struct key_type key_type_logon = {
  48         .name                   = "logon",
  49         .preparse               = user_preparse,
  50         .free_preparse          = user_free_preparse,
  51         .instantiate            = generic_key_instantiate,
  52         .update                 = user_update,
  53         .revoke                 = user_revoke,
  54         .destroy                = user_destroy,
  55         .describe               = user_describe,
  56         .vet_description        = logon_vet_description,
  57 };
  58 EXPORT_SYMBOL_GPL(key_type_logon);
  59
  60 /*
  61  * Preparse a user defined key payload
  62  */
  63 int user_preparse(struct key_preparsed_payload *prep)
  64 {
  65         struct user_key_payload *upayload;
  66         size_t datalen = prep->datalen;
  67
  68         if (datalen <= 0 || datalen > 32767 || !prep->data)
  69                 return -EINVAL;
  70
  71         upayload = kmalloc(sizeof(*upayload) + datalen, GFP_KERNEL);
  72         if (!upayload)
  73                 return -ENOMEM;
  74
  75         /* attach the data */
  76         prep->quotalen = datalen;
  77         prep->payload.data[0] = upayload;
  78         upayload->datalen = datalen;
  79         memcpy(upayload->data, prep->data, datalen);
  80         return 0;
  81 }
  82 EXPORT_SYMBOL_GPL(user_preparse);
  83
  84 /*
  85  * Free a preparse of a user defined key payload
  86  */
  87 void user_free_preparse(struct key_preparsed_payload *prep)
  88 {
  89         kfree(prep->payload.data[0]);
  90 }
  91 EXPORT_SYMBOL_GPL(user_free_preparse);
  92
  93 /*
  94  * update a user defined key
  95  * - the key's semaphore is write-locked
  96  */
  97 int user_update(struct key *key, struct key_preparsed_payload *prep)
  98 {
  99         struct user_key_payload *upayload, *zap;
 100         size_t datalen = prep->datalen;
 101         int ret;
 102
 103         ret = -EINVAL;
 104         if (datalen <= 0 || datalen > 32767 || !prep->data)
 105                 goto error;
 106
 107         /* construct a replacement payload */
 108         ret = -ENOMEM;
 109         upayload = kmalloc(sizeof(*upayload) + datalen, GFP_KERNEL);
 110         if (!upayload)
 111                 goto error;
 112
 113         upayload->datalen = datalen;
 114         memcpy(upayload->data, prep->data, datalen);
 115
 116         /* check the quota and attach the new data */
 117         zap = upayload;
 118
 119         ret = key_payload_reserve(key, datalen);
 120
 121         if (ret == 0) {
 122                 /* attach the new data, displacing the old */
 123                 if (!test_bit(KEY_FLAG_NEGATIVE, &key->flags))
 124                         zap = key->payload.data[0];
 125                 else
 126                         zap = NULL;
 127                 rcu_assign_keypointer(key, upayload);
 128                 key->expiry = 0;
 129         }
 130
 131         if (zap)
 132                 kfree_rcu(zap, rcu);
 133
 134 error:
 135         return ret;
 136 }
 137
 138 EXPORT_SYMBOL_GPL(user_update);
 139
 140 /*
 141  * dispose of the links from a revoked keyring
 142  * - called with the key sem write-locked
 143  */
 144 void user_revoke(struct key *key)
 145 {
 146         struct user_key_payload *upayload = key->payload.data[0];
 147
 148         /* clear the quota */
 149         key_payload_reserve(key, 0);
 150
 151         if (upayload) {
 152                 rcu_assign_keypointer(key, NULL);
 153                 kfree_rcu(upayload, rcu);
 154         }
 155 }
 156
 157 EXPORT_SYMBOL(user_revoke);
 158
 159 /*
 160  * dispose of the data dangling from the corpse of a user key
 161  */
 162 void user_destroy(struct key *key)
 163 {
 164         struct user_key_payload *upayload = key->payload.data[0];
 165
 166         kfree(upayload);
 167 }
 168
 169 EXPORT_SYMBOL_GPL(user_destroy);
 170
 171 /*
 172  * describe the user key
 173  */
 174 void user_describe(const struct key *key, struct seq_file *m)
 175 {
 176         seq_puts(m, key->description);
 177         if (key_is_instantiated(key))
 178                 seq_printf(m, ": %u", key->datalen);
 179 }
 180
 181 EXPORT_SYMBOL_GPL(user_describe);
 182
 183 /*
 184  * read the key data
 185  * - the key's semaphore is read-locked
 186  */
 187 long user_read(const struct key *key, char __user *buffer, size_t buflen)
 188 {
 189         const struct user_key_payload *upayload;
 190         long ret;
 191
 192         upayload = user_key_payload(key);
 193         ret = upayload->datalen;
 194
 195         /* we can return the data as is */
 196         if (buffer && buflen > 0) {
 197                 if (buflen > upayload->datalen)
 198                         buflen = upayload->datalen;
 199
 200                 if (copy_to_user(buffer, upayload->data, buflen) != 0)
 201                         ret = -EFAULT;
 202         }
 203
 204         return ret;
 205 }
 206
 207 EXPORT_SYMBOL_GPL(user_read);
 208
 209 /* Vet the description for a "logon" key */
 210 static int logon_vet_description(const char *desc)
 211 {
 212         char *p;
 213
 214         /* require a "qualified" description string */
 215         p = strchr(desc, ':');
 216         if (!p)
 217                 return -EINVAL;
 218
 219         /* also reject description with ':' as first char */
 220         if (p == desc)
 221                 return -EINVAL;
 222
 223         return 0;
 224 }