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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}