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  */
20 static bool ima_process_keys;
21 
22 /*
23  * To synchronize access to the list of keys that need to be measured
24  */
25 static DEFINE_MUTEX(ima_keys_lock);
26 static 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  */
33 static long ima_key_queue_timeout = 300000; /* 5 Minutes */
34 static void ima_keys_handler(struct work_struct *work);
35 static DECLARE_DELAYED_WORK(ima_keys_delayed_work, ima_keys_handler);
36 static 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  */
42 static 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  */
52 void ima_init_key_queue(void)
53 {
54 	schedule_delayed_work(&ima_keys_delayed_work,
55 			      msecs_to_jiffies(ima_key_queue_timeout));
56 }
57 
58 static 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 
67 static 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 
91 out:
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 
104 bool 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  */
133 void 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 
174 inline bool ima_should_queue_key(void)
175 {
176 	return !ima_process_keys;
177 }
178