Link to breaking change announcement in IDX10506

When an IDX10506 exception is thrown from JsonWebTokenHandler, there's a
good chance this is due to a breaking change to ASP.NET Core 8.

This adds a link to the breaking change announcement at
https://learn.microsoft.com/en-us/dotnet/core/compatibility/aspnet-core/8.0/securitytoken-events

src/Microsoft.IdentityModel.JsonWebTokens/JsonWebTokenHandler.cs

@@ -17,7 +17,7 @@
 namespace Microsoft.IdentityModel.JsonWebTokens
 {
     /// <summary>
-    /// A <see cref="SecurityTokenHandler"/> designed for creating and validating Json Web Tokens. 
+    /// A <see cref="SecurityTokenHandler"/> designed for creating and validating Json Web Tokens.
     /// See: https://datatracker.ietf.org/doc/html/rfc7519 and http://www.rfc-editor.org/info/rfc7515.
     /// </summary>
     public partial class JsonWebTokenHandler : TokenHandler
@@ -38,7 +38,7 @@ public partial class JsonWebTokenHandler : TokenHandler
         public static bool DefaultMapInboundClaims = false;
 
         /// <summary>
-        /// Gets the Base64Url encoded string representation of the following JWT header: 
+        /// Gets the Base64Url encoded string representation of the following JWT header:
         /// { <see cref="JwtHeaderParameterNames.Alg"/>, <see cref="SecurityAlgorithms.None"/> }.
         /// </summary>
         /// <return>The Base64Url encoded string representation of the unsigned JWT header.</return>
@@ -85,7 +85,7 @@ public static string ShortClaimTypeProperty
         }
 
         /// <summary>
-        /// Gets or sets the <see cref="MapInboundClaims"/> property which is used when determining whether or not to map claim types that are extracted when validating a <see cref="JsonWebToken"/>. 
+        /// Gets or sets the <see cref="MapInboundClaims"/> property which is used when determining whether or not to map claim types that are extracted when validating a <see cref="JsonWebToken"/>.
         /// <para>If this is set to true, the <see cref="Claim.Type"/> is set to the JSON claim 'name' after translating using this mapping. Otherwise, no mapping occurs.</para>
         /// <para>The default value is false.</para>
         /// </summary>
@@ -104,7 +104,7 @@ public bool MapInboundClaims
         }
 
         /// <summary>
-        /// Gets or sets the <see cref="InboundClaimTypeMap"/> which is used when setting the <see cref="Claim.Type"/> for claims in the <see cref="ClaimsPrincipal"/> extracted when validating a <see cref="JsonWebToken"/>. 
+        /// Gets or sets the <see cref="InboundClaimTypeMap"/> which is used when setting the <see cref="Claim.Type"/> for claims in the <see cref="ClaimsPrincipal"/> extracted when validating a <see cref="JsonWebToken"/>.
         /// <para>The <see cref="Claim.Type"/> is set to the JSON claim 'name' after translating using this mapping.</para>
         /// <para>The default value is ClaimTypeMapping.InboundClaimTypeMap.</para>
         /// </summary>
@@ -331,7 +331,7 @@ private ClaimsIdentity CreateClaimsIdentityPrivate(JsonWebToken jwtToken, TokenV
         }
 
         /// <summary>
-        /// Decrypts a JWE and returns the clear text 
+        /// Decrypts a JWE and returns the clear text
         /// </summary>
         /// <param name="jwtToken">the JWE that contains the cypher text.</param>
         /// <param name="validationParameters">contains crypto material.</param>
@@ -811,7 +811,7 @@ private static JsonWebToken ValidateSignatureUsingDelegates(JsonWebToken jsonWeb
                     throw LogHelper.LogExceptionMessage(new SecurityTokenInvalidSignatureException(LogHelper.FormatInvariant(TokenLogMessages.IDX10505, jsonWebToken)));
 
                 if (!(validatedToken is JsonWebToken validatedJsonWebToken))
-                    throw LogHelper.LogExceptionMessage(new SecurityTokenInvalidSignatureException(LogHelper.FormatInvariant(TokenLogMessages.IDX10506, LogHelper.MarkAsNonPII(typeof(JsonWebToken)), LogHelper.MarkAsNonPII(validatedToken.GetType()), jsonWebToken)));
+                    throw LogHelper.LogExceptionMessage(new SecurityTokenInvalidSignatureException(LogHelper.FormatInvariant(LogMessages.IDX10506, LogHelper.MarkAsNonPII(typeof(JsonWebToken)), LogHelper.MarkAsNonPII(validatedToken.GetType()), jsonWebToken)));
 
                 return validatedJsonWebToken;
             }
@@ -822,7 +822,7 @@ private static JsonWebToken ValidateSignatureUsingDelegates(JsonWebToken jsonWeb
                     throw LogHelper.LogExceptionMessage(new SecurityTokenInvalidSignatureException(LogHelper.FormatInvariant(TokenLogMessages.IDX10505, jsonWebToken)));
 
                 if (!(validatedToken is JsonWebToken validatedJsonWebToken))
-                    throw LogHelper.LogExceptionMessage(new SecurityTokenInvalidSignatureException(LogHelper.FormatInvariant(TokenLogMessages.IDX10506, LogHelper.MarkAsNonPII(typeof(JsonWebToken)), LogHelper.MarkAsNonPII(validatedToken.GetType()), jsonWebToken)));
+                    throw LogHelper.LogExceptionMessage(new SecurityTokenInvalidSignatureException(LogHelper.FormatInvariant(LogMessages.IDX10506, LogHelper.MarkAsNonPII(typeof(JsonWebToken)), LogHelper.MarkAsNonPII(validatedToken.GetType()), jsonWebToken)));
 
                 return validatedJsonWebToken;
             }

src/Microsoft.IdentityModel.JsonWebTokens/LogMessages.cs

@@ -13,6 +13,9 @@ internal static class LogMessages
     {
         #pragma warning disable 1591
 
+        // This reuses the ID of TokenLogMessages.IDX10506 to provide a message more specific to JsonWebTokens while allowing people searching the ID to search solutions provided for the old message like those at https://stackoverflow.com/questions/77515249/custom-token-validator-not-working-in-net-8
+        internal const string IDX10506 = "IDX10506: Signature validation failed. The user defined 'Delegate' specified on TokenValidationParameters did not return a '{0}', but returned a '{1}' when validating token: '{2}'. If you are using ASP.NET Core 8 or later, see https://learn.microsoft.com/en-us/dotnet/core/compatibility/aspnet-core/8.0/securitytoken-events for more details.";
+
         // signature creation / validation
         internal const string IDX14000 = "IDX14000: Signature validation of this JWT is not supported for: Algorithm: '{0}', SecurityKey: '{1}'.";