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
 17unsigned 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 */
 24static 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 */
 44static 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 */
 77static 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
112found:
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 */
131long 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
166out_put_dest:
167	key_ref_put(dest_ref);
168	return ret;
169}