security/keys/persistent.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /* General persistent per-UID keyrings register
   3  *
   4  * Copyright (C) 2013 Red Hat, Inc. All Rights Reserved.
   5  * Written by David Howells (dhowells@redhat.com)
   6  */
   7
   8 #include <linux/user_namespace.h>
   9 #include <linux/cred.h>
  10
  11 #include "internal.h"
  12
  13 unsigned persistent_keyring_expiry = 3 * 24 * 3600; /* Expire after 3 days of non-use */
  14
  15 /*
  16  * Create the persistent keyring register for the current user namespace.
  17  *
  18  * Called with the namespace's sem locked for writing.
  19  */
  20 static int key_create_persistent_register(struct user_namespace *ns)
  21 {
  22         struct key *reg = keyring_alloc(".persistent_register",
  23                                         KUIDT_INIT(0), KGIDT_INIT(0),
  24                                         current_cred(),
  25                                         ((KEY_POS_ALL & ~KEY_POS_SETATTR) |
  26                                          KEY_USR_VIEW | KEY_USR_READ),
  27                                         KEY_ALLOC_NOT_IN_QUOTA, NULL, NULL);
  28         if (IS_ERR(reg))
  29                 return PTR_ERR(reg);
  30
  31         ns->persistent_keyring_register = reg;
  32         return 0;
  33 }
  34
  35 /*
  36  * Create the persistent keyring for the specified user.
  37  *
  38  * Called with the namespace's sem locked for writing.
  39  */
  40 static key_ref_t key_create_persistent(struct user_namespace *ns, kuid_t uid,
  41                                        struct keyring_index_key *index_key)
  42 {
  43         struct key *persistent;
  44         key_ref_t reg_ref, persistent_ref;
  45
  46         if (!ns->persistent_keyring_register) {
  47                 long err = key_create_persistent_register(ns);
  48                 if (err < 0)
  49                         return ERR_PTR(err);
  50         } else {
  51                 reg_ref = make_key_ref(ns->persistent_keyring_register, true);
  52                 persistent_ref = find_key_to_update(reg_ref, index_key);
  53                 if (persistent_ref)
  54                         return persistent_ref;
  55         }
  56
  57         persistent = keyring_alloc(index_key->description,
  58                                    uid, INVALID_GID, current_cred(),
  59                                    ((KEY_POS_ALL & ~KEY_POS_SETATTR) |
  60                                     KEY_USR_VIEW | KEY_USR_READ),
  61                                    KEY_ALLOC_NOT_IN_QUOTA, NULL,
  62                                    ns->persistent_keyring_register);
  63         if (IS_ERR(persistent))
  64                 return ERR_CAST(persistent);
  65
  66         return make_key_ref(persistent, true);
  67 }
  68
  69 /*
  70  * Get the persistent keyring for a specific UID and link it to the nominated
  71  * keyring.
  72  */
  73 static long key_get_persistent(struct user_namespace *ns, kuid_t uid,
  74                                key_ref_t dest_ref)
  75 {
  76         struct keyring_index_key index_key;
  77         struct key *persistent;
  78         key_ref_t reg_ref, persistent_ref;
  79         char buf[32];
  80         long ret;
  81
  82         /* Look in the register if it exists */
  83         memset(&index_key, 0, sizeof(index_key));
  84         index_key.type = &key_type_keyring;
  85         index_key.description = buf;
  86         index_key.desc_len = sprintf(buf, "_persistent.%u", from_kuid(ns, uid));
  87         key_set_index_key(&index_key);
  88
  89         if (ns->persistent_keyring_register) {
  90                 reg_ref = make_key_ref(ns->persistent_keyring_register, true);
  91                 down_read(&ns->keyring_sem);
  92                 persistent_ref = find_key_to_update(reg_ref, &index_key);
  93                 up_read(&ns->keyring_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->keyring_sem);
 103         persistent_ref = key_create_persistent(ns, uid, &index_key);
 104         up_write(&ns->keyring_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 }