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, const void *data, size_t datalen)
  62 {
  63         struct user_key_payload *upayload;
  64         int ret;
  65
  66         ret = -EINVAL;
  67         if (datalen <= 0 || datalen > 32767 || !data)
  68                 goto error;
  69
  70         ret = key_payload_reserve(key, datalen);
  71         if (ret < 0)
  72                 goto error;
  73
  74         ret = -ENOMEM;
  75         upayload = kmalloc(sizeof(*upayload) + datalen, GFP_KERNEL);
  76         if (!upayload)
  77                 goto error;
  78
  79         /* attach the data */
  80         upayload->datalen = datalen;
  81         memcpy(upayload->data, data, datalen);
  82         rcu_assign_keypointer(key, upayload);
  83         ret = 0;
  84
  85 error:
  86         return ret;
  87 }
  88
  89 EXPORT_SYMBOL_GPL(user_instantiate);
  90
  91 /*
  92  * update a user defined key
  93  * - the key's semaphore is write-locked
  94  */
  95 int user_update(struct key *key, const void *data, size_t datalen)
  96 {
  97         struct user_key_payload *upayload, *zap;
  98         int ret;
  99
 100         ret = -EINVAL;
 101         if (datalen <= 0 || datalen > 32767 || !data)
 102                 goto error;
 103
 104         /* construct a replacement payload */
 105         ret = -ENOMEM;
 106         upayload = kmalloc(sizeof(*upayload) + datalen, GFP_KERNEL);
 107         if (!upayload)
 108                 goto error;
 109
 110         upayload->datalen = datalen;
 111         memcpy(upayload->data, data, datalen);
 112
 113         /* check the quota and attach the new data */
 114         zap = upayload;
 115
 116         ret = key_payload_reserve(key, datalen);
 117
 118         if (ret == 0) {
 119                 /* attach the new data, displacing the old */
 120                 zap = key->payload.data;
 121                 rcu_assign_keypointer(key, upayload);
 122                 key->expiry = 0;
 123         }
 124
 125         if (zap)
 126                 kfree_rcu(zap, rcu);
 127
 128 error:
 129         return ret;
 130 }
 131
 132 EXPORT_SYMBOL_GPL(user_update);
 133
 134 /*
 135  * match users on their name
 136  */
 137 int user_match(const struct key *key, const void *description)
 138 {
 139         return strcmp(key->description, description) == 0;
 140 }
 141
 142 EXPORT_SYMBOL_GPL(user_match);
 143
 144 /*
 145  * dispose of the links from a revoked keyring
 146  * - called with the key sem write-locked
 147  */
 148 void user_revoke(struct key *key)
 149 {
 150         struct user_key_payload *upayload = key->payload.data;
 151
 152         /* clear the quota */
 153         key_payload_reserve(key, 0);
 154
 155         if (upayload) {
 156                 rcu_assign_keypointer(key, NULL);
 157                 kfree_rcu(upayload, rcu);
 158         }
 159 }
 160
 161 EXPORT_SYMBOL(user_revoke);
 162
 163 /*
 164  * dispose of the data dangling from the corpse of a user key
 165  */
 166 void user_destroy(struct key *key)
 167 {
 168         struct user_key_payload *upayload = key->payload.data;
 169
 170         kfree(upayload);
 171 }
 172
 173 EXPORT_SYMBOL_GPL(user_destroy);
 174
 175 /*
 176  * describe the user key
 177  */
 178 void user_describe(const struct key *key, struct seq_file *m)
 179 {
 180         seq_puts(m, key->description);
 181         if (key_is_instantiated(key))
 182                 seq_printf(m, ": %u", key->datalen);
 183 }
 184
 185 EXPORT_SYMBOL_GPL(user_describe);
 186
 187 /*
 188  * read the key data
 189  * - the key's semaphore is read-locked
 190  */
 191 long user_read(const struct key *key, char __user *buffer, size_t buflen)
 192 {
 193         struct user_key_payload *upayload;
 194         long ret;
 195
 196         upayload = rcu_dereference_key(key);
 197         ret = upayload->datalen;
 198
 199         /* we can return the data as is */
 200         if (buffer && buflen > 0) {
 201                 if (buflen > upayload->datalen)
 202                         buflen = upayload->datalen;
 203
 204                 if (copy_to_user(buffer, upayload->data, buflen) != 0)
 205                         ret = -EFAULT;
 206         }
 207
 208         return ret;
 209 }
 210
 211 EXPORT_SYMBOL_GPL(user_read);
 212
 213 /* Vet the description for a "logon" key */
 214 static int logon_vet_description(const char *desc)
 215 {
 216         char *p;
 217
 218         /* require a "qualified" description string */
 219         p = strchr(desc, ':');
 220         if (!p)
 221                 return -EINVAL;
 222
 223         /* also reject description with ':' as first char */
 224         if (p == desc)
 225                 return -EINVAL;
 226
 227         return 0;
 228 }