From e4cd129b9fd12b5f2dce58244f532c9fccd44fbd Mon Sep 17 00:00:00 2001
From: Jason Nelson <jason@carbonmade.com>
Date: Tue, 6 Sep 2022 14:37:49 -0700
Subject: [PATCH] Eliminate Linq usage in Packed

---
 Src/Fido2/AttestationFormat/Packed.cs | 21 ++++++++++++++-------
 Src/Fido2/Fido2.csproj                |  1 +
 2 files changed, 15 insertions(+), 7 deletions(-)

diff --git a/Src/Fido2/AttestationFormat/Packed.cs b/Src/Fido2/AttestationFormat/Packed.cs
index 4e655fc8..28683684 100644
--- a/Src/Fido2/AttestationFormat/Packed.cs
+++ b/Src/Fido2/AttestationFormat/Packed.cs
@@ -1,5 +1,5 @@
 using System;
-using System.Linq;
+using System.Collections.Generic;
 using System.Security.Cryptography.X509Certificates;
 
 using Fido2NetLib.Cbor;
@@ -9,18 +9,25 @@ namespace Fido2NetLib
 {
     internal sealed class Packed : AttestationVerifier
     {
-        private static readonly string[] s_newLine = new string[] { Environment.NewLine };
-
         public static bool IsValidPackedAttnCertSubject(string attnCertSubj)
         {
             // parse the DN string using standard rules
             var dictSubjectObj = new X500DistinguishedName(attnCertSubj);
 
             // form the string for splitting using new lines to avoid issues with commas
-            var dictSubjectString = dictSubjectObj.Decode(X500DistinguishedNameFlags.UseNewLines); 
-            var dictSubject = dictSubjectString.Split(s_newLine, StringSplitOptions.None)
-                                          .Select(part => part.Split('='))
-                                          .ToDictionary(split => split[0], split => split[1]);
+            string dictSubjectString = dictSubjectObj.Decode(X500DistinguishedNameFlags.UseNewLines);
+
+            var dictSubject = new Dictionary<string, string>();
+
+            foreach (var line in dictSubjectString.AsSpan().EnumerateLines())
+            {
+                int equalIndex = line.IndexOf('=');
+
+                var lhs = line.Slice(0, equalIndex).ToString();
+                var rhs = line.Slice(equalIndex + 1).ToString();
+
+                dictSubject[lhs] = rhs;
+            }
 
             return dictSubject["C"].Length != 0 
                 && dictSubject["O"].Length != 0 
diff --git a/Src/Fido2/Fido2.csproj b/Src/Fido2/Fido2.csproj
index 469cb955..5b191c33 100644
--- a/Src/Fido2/Fido2.csproj
+++ b/Src/Fido2/Fido2.csproj
@@ -4,6 +4,7 @@
     <Nullable>enable</Nullable>
     <RootNamespace>Fido2NetLib</RootNamespace>
     <IsTrimmable>true</IsTrimmable>
+    <NoWarn>IDE0057</NoWarn>
   </PropertyGroup>
    
   <ItemGroup>