[security] Fix SecKeyChain.QueryAsData (#2485)

- Fixes bug #58720: SecKeychain.QueryAsData returns invalid data type
(https://bugzilla.xamarin.com/show_bug.cgi?id=58720)

As per Apple's doc: https://developer.apple.com/documentation/security/keychain_services/keychain_items/item_return_result_keys?language=objc
when multiple return types are requested (when wantPersistentReference is set to true),
the underlying native return type is an NSDictionary not an NSData.

As per https://bugzilla.xamarin.com/show_bug.cgi?id=58720#c3
when trying to access the byte property of the NSData object, we'd get an "unrecognized selector sent to instance".
This is confirmed by the added test.

src/Security/Items.cs

@@ -110,9 +110,10 @@ namespace XamCore.Security {
 
 			using (var copy = NSMutableDictionary.FromDictionary (query.queryDict)){
 				SetLimit (copy, 1);
-				copy.LowlevelSetObject (CFBoolean.True.Handle, SecItem.ReturnData);
 				if (wantPersistentReference)
 					copy.LowlevelSetObject (CFBoolean.True.Handle, SecItem.ReturnPersistentRef);
+				else
+					copy.LowlevelSetObject (CFBoolean.True.Handle, SecItem.ReturnData);
 				
 				IntPtr ptr;
 				status = SecItem.SecItemCopyMatching (copy.Handle, out ptr);
@@ -129,9 +130,10 @@ namespace XamCore.Security {
 
 			using (var copy = NSMutableDictionary.FromDictionary (query.queryDict)){
 				var n = SetLimit (copy, max);
-				copy.LowlevelSetObject (CFBoolean.True.Handle, SecItem.ReturnData);
 				if (wantPersistentReference)
 					copy.LowlevelSetObject (CFBoolean.True.Handle, SecItem.ReturnPersistentRef);
+				else
+					copy.LowlevelSetObject (CFBoolean.True.Handle, SecItem.ReturnData);
 
 				IntPtr ptr;
 				status = SecItem.SecItemCopyMatching (copy.Handle, out ptr);

tests/monotouch-test/Security/KeyChainTest.cs

@@ -112,6 +112,36 @@ namespace MonoTouchFixtures.Security {
 			
 			return returnGuid;
 		}
+
+		[Test]
+		public void QueryAsData ()
+		{
+			SecStatusCode code;
+			SecRecord queryRec = new SecRecord (SecKind.GenericPassword) {
+				Service = "KEYCHAIN_SERVICE",
+				Label = "KEYCHAIN_SERVICE",
+				Account = "KEYCHAIN_ACCOUNT"
+			};
+			var data = SecKeyChain.QueryAsData (queryRec, true, out code);
+			if (code == SecStatusCode.Success && queryRec != null) {
+				Assert.NotNull (data.Bytes);
+			}
+		}
+
+		[Test]
+		public void QueryAsDataArray ()
+		{
+			SecStatusCode code;
+			SecRecord queryRec = new SecRecord (SecKind.GenericPassword) {
+				Service = "KEYCHAIN_SERVICE",
+				Label = "KEYCHAIN_SERVICE",
+				Account = "KEYCHAIN_ACCOUNT"
+			};
+			var data = SecKeyChain.QueryAsData (queryRec, true, 1, out code);
+			if (code == SecStatusCode.Success && queryRec != null) {
+				Assert.NotNull (data [0].Bytes);
+			}
+		}
 		
 		static SecStatusCode SetID (Guid setID)
 		{