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/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(&init_user_ns, NULL,
 163                                                    entry->payload,
 164                                                    entry->payload_len,
 165                                                    entry->keyring_name,
 166                                                    KEY_CHECK, 0,
 167                                                    entry->keyring_name,
 168                                                    false);
 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 }