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