From 89e7033830bd73a35f4bb2faf14ccf06f3785712 Mon Sep 17 00:00:00 2001
From: JF <jf@codingfield.com>
Date: Sun, 28 Jun 2020 11:59:14 +0200
Subject: [PATCH] Fix buffer overflow opportunities in AlertNotificationService
 & AlertNotificationClient.

---
 .../Ble/AlertNotificationClient.cpp           | 25 ++++++++++----
 .../Ble/AlertNotificationService.cpp          | 34 +++++++++++--------
 src/Components/Ble/NotificationManager.cpp    |  7 ++--
 src/Components/Ble/NotificationManager.h      |  4 +--
 4 files changed, 43 insertions(+), 27 deletions(-)

diff --git a/src/Components/Ble/AlertNotificationClient.cpp b/src/Components/Ble/AlertNotificationClient.cpp
index bf4d851c..b65e019d 100644
--- a/src/Components/Ble/AlertNotificationClient.cpp
+++ b/src/Components/Ble/AlertNotificationClient.cpp
@@ -105,14 +105,25 @@ int AlertNotificationClient::OnDescriptorDiscoveryEventCallback(uint16_t connect
 
 void AlertNotificationClient::OnNotification(ble_gap_event *event) {
   if(event->notify_rx.attr_handle == newAlertHandle) {
-    size_t notifSize = OS_MBUF_PKTLEN(event->notify_rx.om);
-    uint8_t data[notifSize + 1];
-    data[notifSize] = '\0';
-    os_mbuf_copydata(event->notify_rx.om, 0, notifSize, data);
-    char *s = (char *) &data[2];
-    NRF_LOG_INFO("DATA : %s", s);
+    // TODO implement this with more memory safety (and constexpr)
+    static const size_t maxBufferSize{21};
+    static const size_t maxMessageSize{18};
+    size_t bufferSize = min(OS_MBUF_PKTLEN(event->notify_rx.om), maxBufferSize);
 
-    notificationManager.Push(Pinetime::Controllers::NotificationManager::Categories::SimpleAlert, s, notifSize + 1);
+    uint8_t data[bufferSize];
+    os_mbuf_copydata(event->notify_rx.om, 0, bufferSize, data);
+
+    char *s = (char *) &data[3];
+    auto messageSize = min(maxMessageSize, (bufferSize-3));
+
+    for (int i = 0; i < messageSize-1; i++) {
+      if (s[i] == 0x00) {
+        s[i] = 0x0A;
+      }
+    }
+    s[messageSize-1] = '\0';
+
+    notificationManager.Push(Pinetime::Controllers::NotificationManager::Categories::SimpleAlert, s, messageSize);
     systemTask.PushMessage(Pinetime::System::SystemTask::Messages::OnNewNotification);
   }
 }
diff --git a/src/Components/Ble/AlertNotificationService.cpp b/src/Components/Ble/AlertNotificationService.cpp
index fd69bda3..0faa17c8 100644
--- a/src/Components/Ble/AlertNotificationService.cpp
+++ b/src/Components/Ble/AlertNotificationService.cpp
@@ -4,6 +4,7 @@
 #include <SystemTask/SystemTask.h>
 
 #include "AlertNotificationService.h"
+#include <cstring>
 
 using namespace Pinetime::Controllers;
 
@@ -55,23 +56,26 @@ int AlertNotificationService::OnAlert(uint16_t conn_handle, uint16_t attr_handle
                                                     struct ble_gatt_access_ctxt *ctxt) {
 
   if (ctxt->op == BLE_GATT_ACCESS_OP_WRITE_CHR) {
-        size_t notifSize = OS_MBUF_PKTLEN(ctxt->om);
-        uint8_t data[notifSize + 1];
-        data[notifSize] = '\0';
-        os_mbuf_copydata(ctxt->om, 0, notifSize, data);
-        char *s = (char *) &data[3];
-        NRF_LOG_INFO("DATA : %s", s);
+    // TODO implement this with more memory safety (and constexpr)
+    static const size_t maxBufferSize{21};
+    static const size_t maxMessageSize{18};
+    size_t bufferSize = min(OS_MBUF_PKTLEN(ctxt->om), maxBufferSize);
 
-        for(int i = 0; i <= notifSize; i++)
-        {
-            if(s[i] == 0x00)
-            {
-                s[i] = 0x0A;
-            }
-        }
+    uint8_t data[bufferSize];
+    os_mbuf_copydata(ctxt->om, 0, bufferSize, data);
 
-        m_notificationManager.Push(Pinetime::Controllers::NotificationManager::Categories::SimpleAlert, s, notifSize + 1);
-        m_systemTask.PushMessage(Pinetime::System::SystemTask::Messages::OnNewNotification);
+    char *s = (char *) &data[3];
+    auto messageSize = min(maxMessageSize, (bufferSize-3));
+
+    for (int i = 0; i < messageSize-1; i++) {
+      if (s[i] == 0x00) {
+        s[i] = 0x0A;
+      }
+    }
+    s[messageSize-1] = '\0';
+
+    m_notificationManager.Push(Pinetime::Controllers::NotificationManager::Categories::SimpleAlert, s, messageSize);
+    m_systemTask.PushMessage(Pinetime::System::SystemTask::Messages::OnNewNotification);
   }
   return 0;
 }
diff --git a/src/Components/Ble/NotificationManager.cpp b/src/Components/Ble/NotificationManager.cpp
index 2e02cb15..0aea0697 100644
--- a/src/Components/Ble/NotificationManager.cpp
+++ b/src/Components/Ble/NotificationManager.cpp
@@ -4,11 +4,12 @@
 using namespace Pinetime::Controllers;
 
 void NotificationManager::Push(Pinetime::Controllers::NotificationManager::Categories category,
-                                                      const char *message, uint8_t messageSize) {
+                                                      const char *message, uint8_t currentMessageSize) {
   // TODO handle edge cases on read/write index
+  auto checkedSize = std::min(currentMessageSize, uint8_t{18});
   auto& notif = notifications[writeIndex];
-  std::memcpy(notif.message.data(), message, messageSize);
-  notif.message[messageSize] = '\0';
+  std::memcpy(notif.message.data(), message, checkedSize);
+  notif.message[checkedSize] = '\0';
   notif.category = category;
 
   writeIndex = (writeIndex + 1 < TotalNbNotifications) ? writeIndex + 1 : 0;
diff --git a/src/Components/Ble/NotificationManager.h b/src/Components/Ble/NotificationManager.h
index 8edd6828..daa1571b 100644
--- a/src/Components/Ble/NotificationManager.h
+++ b/src/Components/Ble/NotificationManager.h
@@ -7,10 +7,10 @@ namespace Pinetime {
     class NotificationManager {
       public:
         enum class Categories {Unknown, SimpleAlert, Email, News, IncomingCall, MissedCall, Sms, VoiceMail, Schedule, HighProriotyAlert, InstantMessage };
-        static constexpr uint8_t MessageSize = 18;
+        static constexpr uint8_t MessageSize{18};
 
         struct Notification {
-          std::array<char, MessageSize> message;
+          std::array<char, MessageSize+1> message;
           Categories category = Categories::Unknown;
         };