security/keys/persistent.c

   1 /* General persistent per-UID keyrings register
   2  *
   3  * Copyright (C) 2013 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 Licence
   8  * as published by the Free Software Foundation; either version
   9  * 2 of the Licence, or (at your option) any later version.
  10  */
  11
  12 #include <linux/user_namespace.h>
  13 #include <linux/cred.h>
  14
  15 #include "internal.h"
  16
  17 unsigned persistent_keyring_expiry = 3 * 24 * 3600; /* Expire after 3 days of non-use */
  18
  19 /*
  20  * Create the persistent keyring register for the current user namespace.
  21  *
  22  * Called with the namespace's sem locked for writing.
  23  */
  24 static int key_create_persistent_register(struct user_namespace *ns)
  25 {
  26         struct key *reg = keyring_alloc(".persistent_register",
  27                                         KUIDT_INIT(0), KGIDT_INIT(0),
  28                                         current_cred(),
  29                                         ((KEY_POS_ALL & ~KEY_POS_SETATTR) |
  30                                          KEY_USR_VIEW | KEY_USR_READ),
  31                                         KEY_ALLOC_NOT_IN_QUOTA, NULL, NULL);
  32         if (IS_ERR(reg))
  33                 return PTR_ERR(reg);
  34
  35         ns->persistent_keyring_register = reg;
  36         return 0;
  37 }
  38
  39 /*
  40  * Create the persistent keyring for the specified user.
  41  *
  42  * Called with the namespace's sem locked for writing.
  43  */
  44 static key_ref_t key_create_persistent(struct user_namespace *ns, kuid_t uid,
  45                                        struct keyring_index_key *index_key)
  46 {
  47         struct key *persistent;
  48         key_ref_t reg_ref, persistent_ref;
  49
  50         if (!ns->persistent_keyring_register) {
  51                 long err = key_create_persistent_register(ns);
  52                 if (err < 0)
  53                         return ERR_PTR(err);
  54         } else {
  55                 reg_ref = make_key_ref(ns->persistent_keyring_register, true);
  56                 persistent_ref = find_key_to_update(reg_ref, index_key);
  57                 if (persistent_ref)
  58                         return persistent_ref;
  59         }
  60
  61         persistent = keyring_alloc(index_key->description,
  62                                    uid, INVALID_GID, current_cred(),
  63                                    ((KEY_POS_ALL & ~KEY_POS_SETATTR) |
  64                                     KEY_USR_VIEW | KEY_USR_READ),
  65                                    KEY_ALLOC_NOT_IN_QUOTA, NULL,
  66                                    ns->persistent_keyring_register);
  67         if (IS_ERR(persistent))
  68                 return ERR_CAST(persistent);
  69
  70         return make_key_ref(persistent, true);
  71 }
  72
  73 /*
  74  * Get the persistent keyring for a specific UID and link it to the nominated
  75  * keyring.
  76  */
  77 static long key_get_persistent(struct user_namespace *ns, kuid_t uid,
  78                                key_ref_t dest_ref)
  79 {
  80         struct keyring_index_key index_key;
  81         struct key *persistent;
  82         key_ref_t reg_ref, persistent_ref;
  83         char buf[32];
  84         long ret;
  85
  86         /* Look in the register if it exists */
  87         index_key.type = &key_type_keyring;
  88         index_key.description = buf;
  89         index_key.desc_len = sprintf(buf, "_persistent.%u", from_kuid(ns, uid));
  90
  91         if (ns->persistent_keyring_register) {
  92                 reg_ref = make_key_ref(ns->persistent_keyring_register, true);
  93                 down_read(&ns->persistent_keyring_register_sem);
  94                 persistent_ref = find_key_to_update(reg_ref, &index_key);
  95                 up_read(&ns->persistent_keyring_register_sem);
  96
  97                 if (persistent_ref)
  98                         goto found;
  99         }
 100
 101         /* It wasn't in the register, so we'll need to create it.  We might
 102          * also need to create the register.
 103          */
 104         down_write(&ns->persistent_keyring_register_sem);
 105         persistent_ref = key_create_persistent(ns, uid, &index_key);
 106         up_write(&ns->persistent_keyring_register_sem);
 107         if (!IS_ERR(persistent_ref))
 108                 goto found;
 109
 110         return PTR_ERR(persistent_ref);
 111
 112 found:
 113         ret = key_task_permission(persistent_ref, current_cred(), KEY_NEED_LINK);
 114         if (ret == 0) {
 115                 persistent = key_ref_to_ptr(persistent_ref);
 116                 ret = key_link(key_ref_to_ptr(dest_ref), persistent);
 117                 if (ret == 0) {
 118                         key_set_timeout(persistent, persistent_keyring_expiry);
 119                         ret = persistent->serial;
 120                 }
 121         }
 122
 123         key_ref_put(persistent_ref);
 124         return ret;
 125 }
 126
 127 /*
 128  * Get the persistent keyring for a specific UID and link it to the nominated
 129  * keyring.
 130  */
 131 long keyctl_get_persistent(uid_t _uid, key_serial_t destid)
 132 {
 133         struct user_namespace *ns = current_user_ns();
 134         key_ref_t dest_ref;
 135         kuid_t uid;
 136         long ret;
 137
 138         /* -1 indicates the current user */
 139         if (_uid == (uid_t)-1) {
 140                 uid = current_uid();
 141         } else {
 142                 uid = make_kuid(ns, _uid);
 143                 if (!uid_valid(uid))
 144                         return -EINVAL;
 145
 146                 /* You can only see your own persistent cache if you're not
 147                  * sufficiently privileged.
 148                  */
 149                 if (!uid_eq(uid, current_uid()) &&
 150                     !uid_eq(uid, current_euid()) &&
 151                     !ns_capable(ns, CAP_SETUID))
 152                         return -EPERM;
 153         }
 154
 155         /* There must be a destination keyring */
 156         dest_ref = lookup_user_key(destid, KEY_LOOKUP_CREATE, KEY_NEED_WRITE);
 157         if (IS_ERR(dest_ref))
 158                 return PTR_ERR(dest_ref);
 159         if (key_ref_to_ptr(dest_ref)->type != &key_type_keyring) {
 160                 ret = -ENOTDIR;
 161                 goto out_put_dest;
 162         }
 163
 164         ret = key_get_persistent(ns, uid, dest_ref);
 165
 166 out_put_dest:
 167         key_ref_put(dest_ref);
 168         return ret;
 169 }