Use user-provided values as Utf8

src/Microsoft.IdentityModel.JsonWebTokens/Json/JsonWebToken.PayloadClaimSet.cs

@@ -3,6 +3,7 @@
 
 using System;
 using System.Collections.Generic;
+using System.Text;
 using System.Text.Json;
 using Microsoft.IdentityModel.Logging;
 using Microsoft.IdentityModel.Tokens;
@@ -73,8 +74,15 @@ internal JsonClaimSet CreatePayloadClaimSet(byte[] bytes, int length)
                     }
                     else if (reader.ValueTextEquals(JwtPayloadUtf8Bytes.Iss))
                     {
-                        _iss = JsonSerializerPrimitives.ReadString(ref reader, JwtRegisteredClaimNames.Iss, ClassName, true);
-                        claims[JwtRegisteredClaimNames.Iss] = _iss;
+                        IssuerUtf8 = Encoding.UTF8.GetBytes(JsonSerializerPrimitives.ReadString(ref reader, JwtRegisteredClaimNames.Iss, ClassName, true));
+
+                        //if (!reader.ValueTextEquals(tokenValidationParameters.ValidIssuerUtf8))
+                        //{
+                        //    throw new InvalidOperationException();
+                        //}
+
+                        // Validate
+                        // await Validators.ValidateIssuerAsync
                     }
                     else if (reader.ValueTextEquals(JwtPayloadUtf8Bytes.Jti))
                     {

src/Microsoft.IdentityModel.JsonWebTokens/JsonWebToken.cs

@@ -972,11 +972,13 @@ public override string Issuer
         {
             get
             {
-                _iss ??= Payload.GetStringValue(JwtRegisteredClaimNames.Iss);
+                _iss ??= IssuerUtf8.ToString();
                 return _iss;
             }
         }
 
+        internal ReadOnlySpan<byte> IssuerUtf8 { get; set; }
+
         /// <summary>
         /// Gets the 'value' of the 'jti' claim from the payload.
         /// </summary>

src/Microsoft.IdentityModel.Tokens/TokenValidationParameters.cs

@@ -5,6 +5,7 @@
 using System.Collections.Generic;
 using System.ComponentModel;
 using System.Security.Claims;
+using System.Text;
 using System.Threading.Tasks;
 using Microsoft.IdentityModel.Abstractions;
 using Microsoft.IdentityModel.Logging;
@@ -893,11 +894,23 @@
         /// </summary>
         public IEnumerable<string> ValidAudiences { get; set; }
 
+        private string _validIssuer;
+
         /// <summary>
         /// Gets or sets a <see cref="string"/> that represents a valid issuer that will be used to check against the token's issuer.
         /// The default is <c>null</c>.
         /// </summary>
-        public string ValidIssuer { get; set; }
+        public string ValidIssuer
+        {
+            get => _validIssuer;
+            set
+            {
+                _validIssuer = value;
+                ValidIssuerUtf8 = value != null ? Encoding.UTF8.GetBytes(value) : null;
+            }
+        }
+
+        internal ReadOnlySpan<byte> ValidIssuerUtf8 { get; set; }
 
         /// <summary>
         /// Gets or sets the <see cref="IEnumerable{String}"/> that contains valid issuers that will be used to check against the token's issuer.