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 } 168