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