Refactoring/optimization2 (#114)

Covid19Radar/Covid19Radar.Android/Covid19Radar.Android.csproj

@@ -1,4 +1,4 @@
-<?xml version="1.0" encoding="utf-8"?>
+<?xml version="1.0" encoding="utf-8"?>
 <Project ToolsVersion="4.0" DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
   <PropertyGroup>
     <Configuration Condition=" '$(Configuration)' == '' ">Debug</Configuration>

Covid19Radar/Covid19Radar.Android/Services/DeviceCheckService.cs

@@ -2,45 +2,63 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
-using System;
 using System.Collections.Generic;
 using System.Linq;
+using System.Security.Cryptography;
 using System.Text;
 using System.Threading.Tasks;
-using Android.App;
-using Android.Content;
-using Android.OS;
-using Android.Runtime;
-using Android.Views;
-using Android.Widget;
-using Covid19Radar.Services;
+using Android.Gms.SafetyNet;
 using Covid19Radar.Droid.Services;
-using Xamarin.Forms;
 using Covid19Radar.Model;
-using Covid19Radar.Common;
-using Android.Gms.SafetyNet;
+using Covid19Radar.Services;
+using Xamarin.Forms;
 
 [assembly: Dependency(typeof(DeviceCheckService))]
 namespace Covid19Radar.Droid.Services
 {
     public class DeviceCheckService : IDeviceVerifier
     {
-
         public Task<string> VerifyAsync(DiagnosisSubmissionParameter submission)
         {
-            var nonce = submission.GetAndroidNonce();
+            var nonce = GetNonce(submission);
             return GetSafetyNetAttestationAsync(nonce);
         }
 
         /// <summary>
         /// Verification device information required for positive submissions
         /// </summary>
         /// <returns>Device Verification Payload</returns>
-        async Task<string> GetSafetyNetAttestationAsync(byte[] nonce)
+        private static async Task<string> GetSafetyNetAttestationAsync(byte[] nonce)
         {
             using var client = SafetyNetClass.GetClient(Android.App.Application.Context);
             using var response = await client.AttestAsync(nonce, AppSettings.Instance.AndroidSafetyNetApiKey);
             return response.JwsResult;
         }
+
+        private static byte[] GetNonce(DiagnosisSubmissionParameter submission)
+        {
+            var cleartext = GetNonceClearText(submission);
+            var nonce = GetSha256(cleartext);
+            return nonce;
+
+            static string GetNonceClearText(DiagnosisSubmissionParameter submission) =>
+                string.Join("|", submission.AppPackageName, GetKeyString(submission.Keys), GetRegionString(submission.Regions), submission.VerificationPayload);
+
+            static string GetKeyString(IEnumerable<DiagnosisSubmissionParameter.Key> keys) =>
+                string.Join(",", keys.OrderBy(k => k.KeyData).Select(k => GetKeyStringCore(k)));
+
+            static string GetKeyStringCore(DiagnosisSubmissionParameter.Key k) =>
+                string.Join(".", k.KeyData, k.RollingStartNumber, k.RollingPeriod);
+
+            static string GetRegionString(IEnumerable<string> regions) =>
+                string.Join(",", regions.Select(r => r.ToUpperInvariant()).OrderBy(r => r));
+
+            static byte[] GetSha256(string text)
+            {
+                using var sha = SHA256.Create();
+                var textBytes = Encoding.UTF8.GetBytes(text);
+                return sha.ComputeHash(textBytes);
+            }
+        }
     }
-}
+}

Covid19Radar/Covid19Radar/App.xaml.cs

@@ -1,22 +1,22 @@
-/* This Source Code Form is subject to the terms of the Mozilla Public
+/* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
+using System;
+using System.Threading.Tasks;
+using CommonServiceLocator;
+using Covid19Radar.Common;
+using Covid19Radar.Services;
+using Covid19Radar.Services.Logs;
+using Covid19Radar.ViewModels;
+using Covid19Radar.Views;
+using DryIoc;
 using Prism;
 using Prism.DryIoc;
 using Prism.Ioc;
-using Covid19Radar.ViewModels;
-using Covid19Radar.Views;
+using Prism.Navigation;
 using Xamarin.Forms;
 using Xamarin.Forms.Xaml;
-using DryIoc;
-using System.Threading.Tasks;
-using Prism.Navigation;
-using Covid19Radar.Services;
-using Covid19Radar.Services.Logs;
-using System;
-using CommonServiceLocator;
-using Covid19Radar.Common;
 
 /*
  * Our mission...is

Covid19Radar/Covid19Radar/AppSettings.cs

@@ -62,8 +62,5 @@ public AppSettings()
         public string LogStorageEndpoint { get; }
         public string LogStorageContainerName { get; }
         public string LogStorageAccountName { get; }
-
-        internal Dictionary<string, ulong> GetDefaultBatch() =>
-            Instance.SupportedRegions.ToDictionary(r => r, r => (ulong)0);
     }
 }

Covid19Radar/Covid19Radar/Common/AppConstants.cs

@@ -6,23 +6,16 @@ namespace Covid19Radar.Common
 {
     public static class AppConstants
     {
-        public static readonly int NumberOfGroup = 86400;
         /// <summary>
         /// Number of days covered from the date of diagnosis or onset
         /// </summary>
         public const int DaysToSendTek = -3;
-        /// <summary>
-        /// Cache Timeout
-        /// </summary>
-        public const int CacheTimeout = 60;
-        /// <summary>
-        /// Active Rolling Period
-        /// </summary>
-        public const uint ActiveRollingPeriod = 144;
+
         /// <summary>
         /// Max Error Count
         /// </summary>
         public const int MaxErrorCount = 3;
+
         /// <summary>
         /// Max diagnosis UID Count
         /// </summary>

Covid19Radar/Covid19Radar/Common/AppUtils.cs

@@ -16,14 +16,6 @@ namespace Covid19Radar.Common
 {
     static class AppUtils
     {
-        public static async void CheckPermission()
-        {
-            var status = await Permissions.CheckStatusAsync<Permissions.LocationAlways>();
-            if (status != PermissionStatus.Granted)
-            {
-                status = await Permissions.RequestAsync<Permissions.LocationAlways>();
-            }
-        }
         public static async void PopUpShare()
         {
             if (Device.RuntimePlatform == Device.iOS)
@@ -85,4 +77,4 @@ public static async void CheckVersion(ILoggerService loggerService)
             }
         }
     }
-}
+}

Covid19Radar/Covid19Radar/Common/DateTimeUtility.cs

@@ -1,10 +1,16 @@
-using System;
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+using System;
+
 namespace Covid19Radar.Common
 {
     public interface IDateTimeUtility
     {
         DateTime UtcNow { get; }
     }
+
     public class DateTimeUtility : IDateTimeUtility
     {
         public static IDateTimeUtility Instance = new DateTimeUtility();

Covid19Radar/Covid19Radar/Common/Utils.cs

@@ -3,18 +3,13 @@
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
 using System;
-using Newtonsoft.Json;
 
 namespace Covid19Radar.Common
 {
     public static class Utils
     {
         #region Other Public Methods
 
-        public static string SerializeToJson(object obj) => JsonConvert.SerializeObject(obj);
-
-        public static T DeserializeFromJson<T>(string jsonObj) => JsonConvert.DeserializeObject<T>(jsonObj);
-
         public static DateTime JstNow()
         {
             return TimeZoneInfo.ConvertTime(DateTime.Now, JstTimeZoneInfo());

Covid19Radar/Covid19Radar/Controls/CustomDatePicker.cs

@@ -6,10 +6,5 @@
 
 namespace Covid19Radar.Controls
 {
-    public class CustomDatePicker : DatePicker
-    {
-        public CustomDatePicker()
-        {
-        }
-    }
+    public class CustomDatePicker : DatePicker { }
 }