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                 zap = key->payload.data[0];
 124                 rcu_assign_keypointer(key, upayload);
 125                 key->expiry = 0;
 126         }
 127
 128         if (zap)
 129                 kfree_rcu(zap, rcu);
 130
 131 error:
 132         return ret;
 133 }
 134
 135 EXPORT_SYMBOL_GPL(user_update);
 136
 137 /*
 138  * dispose of the links from a revoked keyring
 139  * - called with the key sem write-locked
 140  */
 141 void user_revoke(struct key *key)
 142 {
 143         struct user_key_payload *upayload = key->payload.data[0];
 144
 145         /* clear the quota */
 146         key_payload_reserve(key, 0);
 147
 148         if (upayload) {
 149                 rcu_assign_keypointer(key, NULL);
 150                 kfree_rcu(upayload, rcu);
 151         }
 152 }
 153
 154 EXPORT_SYMBOL(user_revoke);
 155
 156 /*
 157  * dispose of the data dangling from the corpse of a user key
 158  */
 159 void user_destroy(struct key *key)
 160 {
 161         struct user_key_payload *upayload = key->payload.data[0];
 162
 163         kfree(upayload);
 164 }
 165
 166 EXPORT_SYMBOL_GPL(user_destroy);
 167
 168 /*
 169  * describe the user key
 170  */
 171 void user_describe(const struct key *key, struct seq_file *m)
 172 {
 173         seq_puts(m, key->description);
 174         if (key_is_instantiated(key))
 175                 seq_printf(m, ": %u", key->datalen);
 176 }
 177
 178 EXPORT_SYMBOL_GPL(user_describe);
 179
 180 /*
 181  * read the key data
 182  * - the key's semaphore is read-locked
 183  */
 184 long user_read(const struct key *key, char __user *buffer, size_t buflen)
 185 {
 186         const struct user_key_payload *upayload;
 187         long ret;
 188
 189         upayload = user_key_payload(key);
 190         ret = upayload->datalen;
 191
 192         /* we can return the data as is */
 193         if (buffer && buflen > 0) {
 194                 if (buflen > upayload->datalen)
 195                         buflen = upayload->datalen;
 196
 197                 if (copy_to_user(buffer, upayload->data, buflen) != 0)
 198                         ret = -EFAULT;
 199         }
 200
 201         return ret;
 202 }
 203
 204 EXPORT_SYMBOL_GPL(user_read);
 205
 206 /* Vet the description for a "logon" key */
 207 static int logon_vet_description(const char *desc)
 208 {
 209         char *p;
 210
 211         /* require a "qualified" description string */
 212         p = strchr(desc, ':');
 213         if (!p)
 214                 return -EINVAL;
 215
 216         /* also reject description with ':' as first char */
 217         if (p == desc)
 218                 return -EINVAL;
 219
 220         return 0;
 221 }