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 #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 }