Respect user-provided authority queries and add to options.ExtraQueryParams

src/Microsoft.Identity.Web/AuthorityHelpers.cs

@@ -2,6 +2,8 @@
 // Licensed under the MIT License.
 
 using System;
+using System.Collections.Generic;
+using System.Web;
 using Microsoft.AspNetCore.Http;
 
 namespace Microsoft.Identity.Web
@@ -51,5 +53,29 @@ internal static string EnsureAuthorityIsV2(string authority)
             preserveAuthority = true;
             return authority;
         }
+
+        internal static string GetAuthorityWithoutQueryIfNeeded(MicrosoftIdentityOptions options)
+        {
+            if (!string.IsNullOrEmpty(options.Authority))
+            {
+                int queryIndex = options.Authority.IndexOf('?', StringComparison.Ordinal);
+                if (queryIndex > -1)
+                {
+                    options.ExtraQueryParameters ??= new Dictionary<string, string>();
+                    var queryParams = HttpUtility.ParseQueryString(options.Authority[queryIndex..].TrimStart('?'));
+                    for (int i = 0; i < queryParams.Count; i++)
+                    {
+                        var key = queryParams.GetKey(i);
+                        var value = queryParams.Get(i);
+                        if (key != null && value != null)
+                            options.ExtraQueryParameters[key] = value;
+                    }
+
+                    return options.Authority[..queryIndex];
+                }
+            }
+
+            return options.Authority ?? string.Empty;
+        }
     }
 }

src/Microsoft.Identity.Web/WebApiExtensions/MicrosoftIdentityWebApiAuthenticationBuilderExtensions.cs

@@ -176,6 +176,7 @@ private static void AddMicrosoftIdentityWebApiImplementation(
                     // Process OIDC compliant tenants
                     if (mergedOptions.Authority != null)
                     {
+                        mergedOptions.Authority = AuthorityHelpers.GetAuthorityWithoutQueryIfNeeded(mergedOptions);
                         mergedOptions.Authority = AuthorityHelpers.BuildCiamAuthorityIfNeeded(mergedOptions.Authority, out bool preserveAuthority);
                         mergedOptions.PreserveAuthority = preserveAuthority;
                         options.Authority = mergedOptions.Authority;

src/Microsoft.Identity.Web/WebAppExtensions/MicrosoftIdentityWebAppAuthenticationBuilderExtensions.cs

@@ -312,6 +312,7 @@ s.ServiceKey is null &&
 
                     if (mergedOptions.Authority != null)
                     {
+                        mergedOptions.Authority = AuthorityHelpers.GetAuthorityWithoutQueryIfNeeded(mergedOptions);
                         mergedOptions.Authority = AuthorityHelpers.BuildCiamAuthorityIfNeeded(mergedOptions.Authority, out bool preserveAuthority);
                         mergedOptions.PreserveAuthority = preserveAuthority;
                         if (mergedOptions.ExtraQueryParameters != null)