cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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persistent.c (4441B)

      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
     13unsigned 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 */
     20static 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 */
     40static 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 */
     73static 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
    110found:
    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 */
    129long 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
    164out_put_dest:
    165	key_ref_put(dest_ref);
    166	return ret;
    167}