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}
178