Gets or sets a value that specifies whether a cookie is accessible by client-side script.
(in System.Web.dll)
'Usage
Dim instance As HttpCookie
Dim value As Boolean
value = instance.HttpOnly
instance.HttpOnly = value
'Declaration
Public Property HttpOnly As Boolean
Property Value
Type:
System..::.Boolean
true if the cookie has the HttpOnly attribute and cannot be accessed through a client-side script; otherwise, false. The default is false.
Microsoft Internet Explorer version 6 Service Pack 1 and later supports a cookie property, HttpOnly, that can help mitigate cross-site scripting threats that result in stolen cookies. Stolen cookies can contain sensitive information identifying the user to the site, such as the ASP.NET session ID or forms authentication ticket, and can be replayed by the attacker in order to masquerade as the user or obtain sensitive information. When an HttpOnly cookie is received by a compliant browser, it is inaccessible to client-side script.
.gif) Caution: |
|---|
Setting the HttpOnly property to true does not prevent an attacker with access to the network channel from accessing the cookie directly. Consider using Secure Sockets Layer (SSL) to help protect against this. Workstation security is also important, as a malicious user could use an open browser window or a computer containing persistent cookies to obtain access to a Web site with a legitimate user's identity. |
For more information on possible attacks and how this property can help mitigate them, see Mitigating Cross-site Scripting With HTTP-only Cookies.
The following code example demonstrates how to write an HttpOnly cookie and shows how it is not accessible by the client through ECMAScript.
<%@ Page Language="VB" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server">
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs)
' Create a new HttpCookie.
Dim myHttpCookie As New HttpCookie("LastVisit", DateTime.Now.ToString())
' By default, the HttpOnly property is set to false
' unless specified otherwise in configuration.
myHttpCookie.Name = "MyHttpCookie"
Response.AppendCookie(myHttpCookie)
' Show the name of the cookie.
Response.Write(myHttpCookie.Name)
' Create an HttpOnly cookie.
Dim myHttpOnlyCookie As New HttpCookie("LastVisit", DateTime.Now.ToString())
' Setting the HttpOnly value to true, makes
' this cookie accessible only to ASP.NET.
myHttpOnlyCookie.HttpOnly = True
myHttpOnlyCookie.Name = "MyHttpOnlyCookie"
Response.AppendCookie(myHttpOnlyCookie)
' Show the name of the HttpOnly cookie.
Response.Write(myHttpOnlyCookie.Name)
End Sub
</script>
<html >
<head runat="server">
<title>ASP.NET Example</title>
</head>
<body>
<script type="text/javascript">
function getCookie(NameOfCookie)
{
if (document.cookie.length > 0)
{
begin = document.cookie.indexOf(NameOfCookie+"=");
if (begin != -1)
{
begin += NameOfCookie.length+1;
end = document.cookie.indexOf(";", begin);
if (end == -1) end = document.cookie.length;
return unescape(document.cookie.substring(begin, end));
}
}
return null;
}
</script>
<script type="text/javascript">
// This code returns the cookie name.
alert("Getting HTTP Cookie");
alert(getCookie("MyHttpCookie"));
// Because the cookie is set to HttpOnly,
// this returns null.
alert("Getting HTTP Only Cookie");
alert(getCookie("MyHttpOnlyCookie"));
</script>
</body>
</html>
Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98
The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.
.NET Framework
Supported in: 3.5, 3.0, 2.0
Reference
