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  */
19 static bool ima_process_keys;
20 
21 /*
22  * To synchronize access to the list of keys that need to be measured
23  */
24 static DEFINE_MUTEX(ima_keys_lock);
25 static 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  */
32 static long ima_key_queue_timeout = 300000; /* 5 Minutes */
33 static void ima_keys_handler(struct work_struct *work);
34 static DECLARE_DELAYED_WORK(ima_keys_delayed_work, ima_keys_handler);
35 static 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  */
41 static 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  */
51 void ima_init_key_queue(void)
52 {
53 	schedule_delayed_work(&ima_keys_delayed_work,
54 			      msecs_to_jiffies(ima_key_queue_timeout));
55 }
56 
57 static 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 
66 static 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 
90 out:
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 
103 bool 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  */
132 void 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 
171 inline bool ima_should_queue_key(void)
172 {
173 	return !ima_process_keys;
174 }
175