ima_queue_keys.c

  1// SPDX-License-Identifier: GPL-2.0+
  2/*
  3 * Copyright (C) 2019 Microsoft Corporation
  4 *
  5 * Author: Lakshmi Ramasubramanian (nramas@linux.microsoft.com)
  6 *
  7 * File: ima_queue_keys.c
  8 *       Enables deferred processing of keys
  9 */
 10
 11#include <linux/user_namespace.h>
 12#include <linux/workqueue.h>
 13#include <keys/asymmetric-type.h>
 14#include "ima.h"
 15
 16/*
 17 * Flag to indicate whether a key can be processed
 18 * right away or should be queued for processing later.
 19 */
 20static bool ima_process_keys;
 21
 22/*
 23 * To synchronize access to the list of keys that need to be measured
 24 */
 25static DEFINE_MUTEX(ima_keys_lock);
 26static LIST_HEAD(ima_keys);
 27
 28/*
 29 * If custom IMA policy is not loaded then keys queued up
 30 * for measurement should be freed. This worker is used
 31 * for handling this scenario.
 32 */
 33static long ima_key_queue_timeout = 300000; /* 5 Minutes */
 34static void ima_keys_handler(struct work_struct *work);
 35static DECLARE_DELAYED_WORK(ima_keys_delayed_work, ima_keys_handler);
 36static bool timer_expired;
 37
 38/*
 39 * This worker function frees keys that may still be
 40 * queued up in case custom IMA policy was not loaded.
 41 */
 42static void ima_keys_handler(struct work_struct *work)
 43{
 44	timer_expired = true;
 45	ima_process_queued_keys();
 46}
 47
 48/*
 49 * This function sets up a worker to free queued keys in case
 50 * custom IMA policy was never loaded.
 51 */
 52void ima_init_key_queue(void)
 53{
 54	schedule_delayed_work(&ima_keys_delayed_work,
 55			      msecs_to_jiffies(ima_key_queue_timeout));
 56}
 57
 58static void ima_free_key_entry(struct ima_key_entry *entry)
 59{
 60	if (entry) {
 61		kfree(entry->payload);
 62		kfree(entry->keyring_name);
 63		kfree(entry);
 64	}
 65}
 66
 67static struct ima_key_entry *ima_alloc_key_entry(struct key *keyring,
 68						 const void *payload,
 69						 size_t payload_len)
 70{
 71	int rc = 0;
 72	const char *audit_cause = "ENOMEM";
 73	struct ima_key_entry *entry;
 74
 75	entry = kzalloc(sizeof(*entry), GFP_KERNEL);
 76	if (entry) {
 77		entry->payload = kmemdup(payload, payload_len, GFP_KERNEL);
 78		entry->keyring_name = kstrdup(keyring->description,
 79					      GFP_KERNEL);
 80		entry->payload_len = payload_len;
 81	}
 82
 83	if ((entry == NULL) || (entry->payload == NULL) ||
 84	    (entry->keyring_name == NULL)) {
 85		rc = -ENOMEM;
 86		goto out;
 87	}
 88
 89	INIT_LIST_HEAD(&entry->list);
 90
 91out:
 92	if (rc) {
 93		integrity_audit_message(AUDIT_INTEGRITY_PCR, NULL,
 94					keyring->description,
 95					func_measure_str(KEY_CHECK),
 96					audit_cause, rc, 0, rc);
 97		ima_free_key_entry(entry);
 98		entry = NULL;
 99	}
100
101	return entry;
102}
103
104bool ima_queue_key(struct key *keyring, const void *payload,
105		   size_t payload_len)
106{
107	bool queued = false;
108	struct ima_key_entry *entry;
109
110	entry = ima_alloc_key_entry(keyring, payload, payload_len);
111	if (!entry)
112		return false;
113
114	mutex_lock(&ima_keys_lock);
115	if (!ima_process_keys) {
116		list_add_tail(&entry->list, &ima_keys);
117		queued = true;
118	}
119	mutex_unlock(&ima_keys_lock);
120
121	if (!queued)
122		ima_free_key_entry(entry);
123
124	return queued;
125}
126
127/*
128 * ima_process_queued_keys() - process keys queued for measurement
129 *
130 * This function sets ima_process_keys to true and processes queued keys.
131 * From here on keys will be processed right away (not queued).
132 */
133void ima_process_queued_keys(void)
134{
135	struct ima_key_entry *entry, *tmp;
136	bool process = false;
137
138	if (ima_process_keys)
139		return;
140
141	/*
142	 * Since ima_process_keys is set to true, any new key will be
143	 * processed immediately and not be queued to ima_keys list.
144	 * First one setting the ima_process_keys flag to true will
145	 * process the queued keys.
146	 */
147	mutex_lock(&ima_keys_lock);
148	if (!ima_process_keys) {
149		ima_process_keys = true;
150		process = true;
151	}
152	mutex_unlock(&ima_keys_lock);
153
154	if (!process)
155		return;
156
157	if (!timer_expired)
158		cancel_delayed_work_sync(&ima_keys_delayed_work);
159
160	list_for_each_entry_safe(entry, tmp, &ima_keys, list) {
161		if (!timer_expired)
162			process_buffer_measurement(&nop_mnt_idmap, NULL,
163						   entry->payload,
164						   entry->payload_len,
165						   entry->keyring_name,
166						   KEY_CHECK, 0,
167						   entry->keyring_name,
168						   false, NULL, 0);
169		list_del(&entry->list);
170		ima_free_key_entry(entry);
171	}
172}
173
174inline bool ima_should_queue_key(void)
175{
176	return !ima_process_keys;
177}