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         kzfree(prep->payload.data[0]);
  90 }
  91 EXPORT_SYMBOL_GPL(user_free_preparse);
  92
  93 static void user_free_payload_rcu(struct rcu_head *head)
  94 {
  95         struct user_key_payload *payload;
  96
  97         payload = container_of(head, struct user_key_payload, rcu);
  98         kzfree(payload);
  99 }
 100
 101 /*
 102  * update a user defined key
 103  * - the key's semaphore is write-locked
 104  */
 105 int user_update(struct key *key, struct key_preparsed_payload *prep)
 106 {
 107         struct user_key_payload *zap = NULL;
 108         int ret;
 109
 110         /* check the quota and attach the new data */
 111         ret = key_payload_reserve(key, prep->datalen);
 112         if (ret < 0)
 113                 return ret;
 114
 115         /* attach the new data, displacing the old */
 116         key->expiry = prep->expiry;
 117         if (key_is_positive(key))
 118                 zap = dereference_key_locked(key);
 119         rcu_assign_keypointer(key, prep->payload.data[0]);
 120         prep->payload.data[0] = NULL;
 121
 122         if (zap)
 123                 call_rcu(&zap->rcu, user_free_payload_rcu);
 124         return ret;
 125 }
 126 EXPORT_SYMBOL_GPL(user_update);
 127
 128 /*
 129  * dispose of the links from a revoked keyring
 130  * - called with the key sem write-locked
 131  */
 132 void user_revoke(struct key *key)
 133 {
 134         struct user_key_payload *upayload = user_key_payload_locked(key);
 135
 136         /* clear the quota */
 137         key_payload_reserve(key, 0);
 138
 139         if (upayload) {
 140                 rcu_assign_keypointer(key, NULL);
 141                 call_rcu(&upayload->rcu, user_free_payload_rcu);
 142         }
 143 }
 144
 145 EXPORT_SYMBOL(user_revoke);
 146
 147 /*
 148  * dispose of the data dangling from the corpse of a user key
 149  */
 150 void user_destroy(struct key *key)
 151 {
 152         struct user_key_payload *upayload = key->payload.data[0];
 153
 154         kzfree(upayload);
 155 }
 156
 157 EXPORT_SYMBOL_GPL(user_destroy);
 158
 159 /*
 160  * describe the user key
 161  */
 162 void user_describe(const struct key *key, struct seq_file *m)
 163 {
 164         seq_puts(m, key->description);
 165         if (key_is_positive(key))
 166                 seq_printf(m, ": %u", key->datalen);
 167 }
 168
 169 EXPORT_SYMBOL_GPL(user_describe);
 170
 171 /*
 172  * read the key data
 173  * - the key's semaphore is read-locked
 174  */
 175 long user_read(const struct key *key, char __user *buffer, size_t buflen)
 176 {
 177         const struct user_key_payload *upayload;
 178         long ret;
 179
 180         upayload = user_key_payload_locked(key);
 181         ret = upayload->datalen;
 182
 183         /* we can return the data as is */
 184         if (buffer && buflen > 0) {
 185                 if (buflen > upayload->datalen)
 186                         buflen = upayload->datalen;
 187
 188                 if (copy_to_user(buffer, upayload->data, buflen) != 0)
 189                         ret = -EFAULT;
 190         }
 191
 192         return ret;
 193 }
 194
 195 EXPORT_SYMBOL_GPL(user_read);
 196
 197 /* Vet the description for a "logon" key */
 198 static int logon_vet_description(const char *desc)
 199 {
 200         char *p;
 201
 202         /* require a "qualified" description string */
 203         p = strchr(desc, ':');
 204         if (!p)
 205                 return -EINVAL;
 206
 207         /* also reject description with ':' as first char */
 208         if (p == desc)
 209                 return -EINVAL;
 210
 211         return 0;
 212 }