[release/5.0] ignore empty domain for digest auth (#50598)

* ignore empty domain for digets auth

* style cleanup

Co-authored-by: wfurt <[email protected]>

Author: github-actions[bot]

src/libraries/Common/tests/System/Net/Http/HttpClientHandlerTest.Authentication.cs

@@ -33,7 +33,6 @@ public abstract class HttpClientHandler_Authentication_Test : HttpClientHandlerT
         private async Task CreateAndValidateRequest(HttpClientHandler handler, Uri url, HttpStatusCode expectedStatusCode, ICredentials credentials)
         {
             handler.Credentials = credentials;
-
             using (HttpClient client = CreateHttpClient(handler))
             using (HttpResponseMessage response = await client.GetAsync(url))
             {
@@ -94,6 +93,13 @@ public static IEnumerable<object[]> Authentication_SocketsHttpHandler_TestData()
                 yield return new object[] { $"Digest realm=\"testrealm\", algorithm=sha-256, nonce=\"testnonce\"", true };
                 yield return new object[] { $"Digest realm=\"testrealm\", algorithm=sha-256-SESS, nonce=\"testnonce\", qop=\"auth\"", true };
             }
+
+            // Add tests cases for empty values that are not mandatory
+            if (!IsWinHttpHandler)
+            {
+                yield return new object[] { "Digest realm=\"testrealm\",nonce=\"6afd170437eb5144258b308f7c491d96\",opaque=\"\",stale=FALSE,algorithm=MD5,qop=\"auth\"", true };
+                yield return new object[] { "Digest realm=\"testrealm\", domain=\"\", nonce=\"NA42+vpOFQd1GwCyVRZuhhy+jDn4BMRl\", algorithm=MD5, qop=\"auth\", stale=false", true };
+            }
         }
 
         [Theory]

src/libraries/System.Net.Http/src/System/Net/Http/SocketsHttpHandler/AuthenticationHelper.Digest.cs

@@ -18,6 +18,7 @@ internal partial class AuthenticationHelper
         private const string Qop = "qop";
         private const string Auth = "auth";
         private const string AuthInt = "auth-int";
+        private const string Domain = "domain";
         private const string Nonce = "nonce";
         private const string NC = "nc";
         private const string Realm = "realm";
@@ -402,9 +403,13 @@ private unsafe void Parse(string challenge)
 
                     // Get the value.
                     string? value = GetNextValue(challenge, parsedIndex, MustValueBeQuoted(key), out parsedIndex);
+                    if (value == null)
+                        break;
+
                     // Ensure value is valid.
-                    if (string.IsNullOrEmpty(value)
-                        && (value == null || !key.Equals(Opaque, StringComparison.OrdinalIgnoreCase)))
+                    // Opaque and Domain can have empty string
+                    if (value == string.Empty &&
+                       (!key.Equals(Opaque, StringComparison.OrdinalIgnoreCase) && !key.Equals(Domain, StringComparison.OrdinalIgnoreCase)))
                         break;
 
                     // Add the key-value pair to Parameters.