Merge pull request #2 from Takym/refactoring/optimization-dsp

`DiagnosisSubmissionParameterExtensions` を `DeviceCheckService` に結合
cocoa-mhlw · May 5, 2021 · a8a02f5 · a8a02f5
2 parents e65bd26 + 5d0d031
commit a8a02f5
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Showing 3 changed files with 32 additions and 56 deletions.
diff --git a/Covid19Radar/Covid19Radar.Android/Covid19Radar.Android.csproj b/Covid19Radar/Covid19Radar.Android/Covid19Radar.Android.csproj
@@ -186,7 +186,6 @@
     </PackageReference>
   </ItemGroup>
   <ItemGroup>
-    <Compile Include="DiagnosisSubmissionParameterExtensions.cs" />
     <Compile Include="MainActivity.cs" />
     <Compile Include="MainApplication.cs" />
     <Compile Include="Resources\Resource.Designer.cs" />

diff --git a/Covid19Radar/Covid19Radar.Android/DiagnosisSubmissionParameterExtensions.cs b/Covid19Radar/Covid19Radar.Android/DiagnosisSubmissionParameterExtensions.cs
diff --git a/Covid19Radar/Covid19Radar.Android/Services/DeviceCheckService.cs b/Covid19Radar/Covid19Radar.Android/Services/DeviceCheckService.cs
@@ -2,33 +2,25 @@
  * 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(Model.DiagnosisSubmissionParameter submission)
+        public Task<string> VerifyAsync(DiagnosisSubmissionParameter submission)
         {
-            var nonce = submission.GetNonce();
+            var nonce = GetNonce(submission);
             return GetSafetyNetAttestationAsync(nonce);
         }
 
@@ -42,5 +34,31 @@ async Task<string> GetSafetyNetAttestationAsync(byte[] nonce)
             using var response = await client.AttestAsync(nonce, AppSettings.Instance.AndroidSafetyNetApiKey);
             return response.JwsResult;
         }
+
+        public 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);
+            }
+        }
     }
 }