security/integrity/ima/ima_queue_keys.c

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