security/keys/user_defined.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /* user_defined.c: user defined key type
   3  *
   4  * Copyright (C) 2004 Red Hat, Inc. All Rights Reserved.
   5  * Written by David Howells (dhowells@redhat.com)
   6  */
   7
   8 #include <linux/export.h>
   9 #include <linux/init.h>
  10 #include <linux/slab.h>
  11 #include <linux/seq_file.h>
  12 #include <linux/err.h>
  13 #include <keys/user-type.h>
  14 #include <linux/uaccess.h>
  15 #include "internal.h"
  16
  17 static int logon_vet_description(const char *desc);
  18
  19 /*
  20  * user defined keys take an arbitrary string as the description and an
  21  * arbitrary blob of data as the payload
  22  */
  23 struct key_type key_type_user = {
  24         .name                   = "user",
  25         .preparse               = user_preparse,
  26         .free_preparse          = user_free_preparse,
  27         .instantiate            = generic_key_instantiate,
  28         .update                 = user_update,
  29         .revoke                 = user_revoke,
  30         .destroy                = user_destroy,
  31         .describe               = user_describe,
  32         .read                   = user_read,
  33 };
  34
  35 EXPORT_SYMBOL_GPL(key_type_user);
  36
  37 /*
  38  * This key type is essentially the same as key_type_user, but it does
  39  * not define a .read op. This is suitable for storing username and
  40  * password pairs in the keyring that you do not want to be readable
  41  * from userspace.
  42  */
  43 struct key_type key_type_logon = {
  44         .name                   = "logon",
  45         .preparse               = user_preparse,
  46         .free_preparse          = user_free_preparse,
  47         .instantiate            = generic_key_instantiate,
  48         .update                 = user_update,
  49         .revoke                 = user_revoke,
  50         .destroy                = user_destroy,
  51         .describe               = user_describe,
  52         .vet_description        = logon_vet_description,
  53 };
  54 EXPORT_SYMBOL_GPL(key_type_logon);
  55
  56 /*
  57  * Preparse a user defined key payload
  58  */
  59 int user_preparse(struct key_preparsed_payload *prep)
  60 {
  61         struct user_key_payload *upayload;
  62         size_t datalen = prep->datalen;
  63
  64         if (datalen <= 0 || datalen > 32767 || !prep->data)
  65                 return -EINVAL;
  66
  67         upayload = kmalloc(sizeof(*upayload) + datalen, GFP_KERNEL);
  68         if (!upayload)
  69                 return -ENOMEM;
  70
  71         /* attach the data */
  72         prep->quotalen = datalen;
  73         prep->payload.data[0] = upayload;
  74         upayload->datalen = datalen;
  75         memcpy(upayload->data, prep->data, datalen);
  76         return 0;
  77 }
  78 EXPORT_SYMBOL_GPL(user_preparse);
  79
  80 /*
  81  * Free a preparse of a user defined key payload
  82  */
  83 void user_free_preparse(struct key_preparsed_payload *prep)
  84 {
  85         kzfree(prep->payload.data[0]);
  86 }
  87 EXPORT_SYMBOL_GPL(user_free_preparse);
  88
  89 static void user_free_payload_rcu(struct rcu_head *head)
  90 {
  91         struct user_key_payload *payload;
  92
  93         payload = container_of(head, struct user_key_payload, rcu);
  94         kzfree(payload);
  95 }
  96
  97 /*
  98  * update a user defined key
  99  * - the key's semaphore is write-locked
 100  */
 101 int user_update(struct key *key, struct key_preparsed_payload *prep)
 102 {
 103         struct user_key_payload *zap = NULL;
 104         int ret;
 105
 106         /* check the quota and attach the new data */
 107         ret = key_payload_reserve(key, prep->datalen);
 108         if (ret < 0)
 109                 return ret;
 110
 111         /* attach the new data, displacing the old */
 112         key->expiry = prep->expiry;
 113         if (key_is_positive(key))
 114                 zap = dereference_key_locked(key);
 115         rcu_assign_keypointer(key, prep->payload.data[0]);
 116         prep->payload.data[0] = NULL;
 117
 118         if (zap)
 119                 call_rcu(&zap->rcu, user_free_payload_rcu);
 120         return ret;
 121 }
 122 EXPORT_SYMBOL_GPL(user_update);
 123
 124 /*
 125  * dispose of the links from a revoked keyring
 126  * - called with the key sem write-locked
 127  */
 128 void user_revoke(struct key *key)
 129 {
 130         struct user_key_payload *upayload = user_key_payload_locked(key);
 131
 132         /* clear the quota */
 133         key_payload_reserve(key, 0);
 134
 135         if (upayload) {
 136                 rcu_assign_keypointer(key, NULL);
 137                 call_rcu(&upayload->rcu, user_free_payload_rcu);
 138         }
 139 }
 140
 141 EXPORT_SYMBOL(user_revoke);
 142
 143 /*
 144  * dispose of the data dangling from the corpse of a user key
 145  */
 146 void user_destroy(struct key *key)
 147 {
 148         struct user_key_payload *upayload = key->payload.data[0];
 149
 150         kzfree(upayload);
 151 }
 152
 153 EXPORT_SYMBOL_GPL(user_destroy);
 154
 155 /*
 156  * describe the user key
 157  */
 158 void user_describe(const struct key *key, struct seq_file *m)
 159 {
 160         seq_puts(m, key->description);
 161         if (key_is_positive(key))
 162                 seq_printf(m, ": %u", key->datalen);
 163 }
 164
 165 EXPORT_SYMBOL_GPL(user_describe);
 166
 167 /*
 168  * read the key data
 169  * - the key's semaphore is read-locked
 170  */
 171 long user_read(const struct key *key, char __user *buffer, size_t buflen)
 172 {
 173         const struct user_key_payload *upayload;
 174         long ret;
 175
 176         upayload = user_key_payload_locked(key);
 177         ret = upayload->datalen;
 178
 179         /* we can return the data as is */
 180         if (buffer && buflen > 0) {
 181                 if (buflen > upayload->datalen)
 182                         buflen = upayload->datalen;
 183
 184                 if (copy_to_user(buffer, upayload->data, buflen) != 0)
 185                         ret = -EFAULT;
 186         }
 187
 188         return ret;
 189 }
 190
 191 EXPORT_SYMBOL_GPL(user_read);
 192
 193 /* Vet the description for a "logon" key */
 194 static int logon_vet_description(const char *desc)
 195 {
 196         char *p;
 197
 198         /* require a "qualified" description string */
 199         p = strchr(desc, ':');
 200         if (!p)
 201                 return -EINVAL;
 202
 203         /* also reject description with ':' as first char */
 204         if (p == desc)
 205                 return -EINVAL;
 206
 207         return 0;
 208 }