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 <linux/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 *zap = NULL;
 100         int ret;
 101
 102         /* check the quota and attach the new data */
 103         ret = key_payload_reserve(key, prep->datalen);
 104         if (ret < 0)
 105                 return ret;
 106
 107         /* attach the new data, displacing the old */
 108         key->expiry = prep->expiry;
 109         if (!test_bit(KEY_FLAG_NEGATIVE, &key->flags))
 110                 zap = rcu_dereference_key(key);
 111         rcu_assign_keypointer(key, prep->payload.data[0]);
 112         prep->payload.data[0] = NULL;
 113
 114         if (zap)
 115                 kfree_rcu(zap, rcu);
 116         return ret;
 117 }
 118 EXPORT_SYMBOL_GPL(user_update);
 119
 120 /*
 121  * dispose of the links from a revoked keyring
 122  * - called with the key sem write-locked
 123  */
 124 void user_revoke(struct key *key)
 125 {
 126         struct user_key_payload *upayload = key->payload.data[0];
 127
 128         /* clear the quota */
 129         key_payload_reserve(key, 0);
 130
 131         if (upayload) {
 132                 rcu_assign_keypointer(key, NULL);
 133                 kfree_rcu(upayload, rcu);
 134         }
 135 }
 136
 137 EXPORT_SYMBOL(user_revoke);
 138
 139 /*
 140  * dispose of the data dangling from the corpse of a user key
 141  */
 142 void user_destroy(struct key *key)
 143 {
 144         struct user_key_payload *upayload = key->payload.data[0];
 145
 146         kfree(upayload);
 147 }
 148
 149 EXPORT_SYMBOL_GPL(user_destroy);
 150
 151 /*
 152  * describe the user key
 153  */
 154 void user_describe(const struct key *key, struct seq_file *m)
 155 {
 156         seq_puts(m, key->description);
 157         if (key_is_instantiated(key))
 158                 seq_printf(m, ": %u", key->datalen);
 159 }
 160
 161 EXPORT_SYMBOL_GPL(user_describe);
 162
 163 /*
 164  * read the key data
 165  * - the key's semaphore is read-locked
 166  */
 167 long user_read(const struct key *key, char __user *buffer, size_t buflen)
 168 {
 169         const struct user_key_payload *upayload;
 170         long ret;
 171
 172         upayload = user_key_payload(key);
 173         ret = upayload->datalen;
 174
 175         /* we can return the data as is */
 176         if (buffer && buflen > 0) {
 177                 if (buflen > upayload->datalen)
 178                         buflen = upayload->datalen;
 179
 180                 if (copy_to_user(buffer, upayload->data, buflen) != 0)
 181                         ret = -EFAULT;
 182         }
 183
 184         return ret;
 185 }
 186
 187 EXPORT_SYMBOL_GPL(user_read);
 188
 189 /* Vet the description for a "logon" key */
 190 static int logon_vet_description(const char *desc)
 191 {
 192         char *p;
 193
 194         /* require a "qualified" description string */
 195         p = strchr(desc, ':');
 196         if (!p)
 197                 return -EINVAL;
 198
 199         /* also reject description with ':' as first char */
 200         if (p == desc)
 201                 return -EINVAL;
 202
 203         return 0;
 204 }