Suppress SM05220 in src/DurableTask.AzureStorage/MessageManager.cs

Resolving
https://msazure.visualstudio.com/Antares/_workitems/edit/37181656

Co-authored-by: Copilot <copilot@github.com>

Author: AnatoliB

src/DurableTask.AzureStorage/MessageManager.cs

@@ -14,6 +14,7 @@
 namespace DurableTask.AzureStorage
 {
     using System;
+    using System.Diagnostics.CodeAnalysis;
     using System.IO;
     using System.IO.Compression;
     using System.Linq;
@@ -51,6 +52,14 @@ class MessageManager
 
         bool containerInitialized;
 
+        [SuppressMessage(
+            "Security",
+            "CA2326:Do not use TypeNameHandling values other than None",
+            Justification = "Required to round-trip polymorphic HistoryEvent payloads through customer-owned Azure Storage. See inline CodeQL suppression comment below.")]
+        [SuppressMessage(
+            "Security",
+            "CA2327:Do not use insecure deserializer settings",
+            Justification = "Required to round-trip polymorphic HistoryEvent payloads through customer-owned Azure Storage. See inline CodeQL suppression comment below.")]
         public MessageManager(
             AzureStorageOrchestrationServiceSettings settings,
             AzureStorageClient azureStorageClient,
@@ -59,6 +68,14 @@ public MessageManager(
             this.settings = settings;
             this.azureStorageClient = azureStorageClient;
             this.blobContainer = this.azureStorageClient.GetBlobContainerReference(blobContainerName);
+            // CodeQL [SM05220] TypeNameHandling.Objects with TypeNameSerializationBinder is required to round-trip
+            // polymorphic HistoryEvent payloads (and dictionary types like ExecutionStartedEvent.Tags) through
+            // customer-owned Azure Storage queues/blobs. The DTFx worker and the Storage account sit on the same
+            // side of the trust boundary: both are authenticated with the customer's tenant credentials, so any
+            // attacker capable of writing a malicious $type into the queue/blob has already breached the data-plane
+            // auth boundary that protects the Storage account. The public ICustomTypeBinder extensibility point
+            // (CustomMessageTypeBinder) lets security-sensitive customers plug in their own allowlist; tightening
+            // the default binder to a hard-coded allowlist would be a breaking change for the DTFx public API.
             this.taskMessageSerializerSettings = new JsonSerializerSettings
             {
                 TypeNameHandling = TypeNameHandling.Objects,