CRV2 FrameworkSpecIssuesASPNet

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ASP.NET Security

Protection against SQL injections

The best solution a developer using ASP.NET can implement to avoid this OWASP #1 in the top ten list of security vulnerabilities is to use Parameterized queries . Equivalent to these solution us the use if Stored procedures which are a form of parameterized queries, for example:

// Build the query statement using parameterized query.
string sql = "SELECT UserId FROM User WHERE " +
               "UserName = @UserName AND Password = @Password";
 
using (SqlCommand cmd = new SqlCommand(sql))
 
{
   // Create the parameter objects as specific as possible.
   cmd.Parameters.Add("@UserName", System.Data.SqlDbType.NVarChar, 50);
   cmd.Parameters.Add("@Password", System.Data.SqlDbType.NVarChar, 25);
 
   // Add the parameter values.  Validation should have already happened.
   cmd.Parameters["@UserName"].Value = UserName;
   cmd.Parameters["@Password"].Value = Password;
   cmd.Connection = connnection;
 
   try
   {
       cmd.Connection.Open();
       var userId = cmd.ExecuteScalar();
   }
   catch (SqlException sx)
   {
       // Handle exceptions before moving on.
   }
}

Source:(Jardine, 2013)

Use an ORM(Object Relational Mapper)

ORM’s are a real blessing regarding protection against SQL injection. By default, the use of ORM will automatically send all SQL request as parameterized queries, however, it’s important to keep in mind that this from of security can be easily bypassed if the developer uses unparameterized HQL or Entity SQL queries dynamically with string concatenations

Request Validation feature against XSS attacks

ASP.NET comes with a built-in request validation feature. This feature was added in the ASP.NET version 1.1, in addition this feature is enabled by default. Once a malformed request containing any HTML tags in send, ASP.NET will simply display an error as shown in the following figure Unfortunately, this inherent feature can also create issues when legitimate requests are sent by users who need to submit data containing certain kind of characters such as brackets. Another disadvantage is that this does not avoid any attacks originated from other application or if stored in the database, neither will offer any protection when input is injected in HTML attributes.

MVC’s CSFR anti-forgery system

This is one handy feature found in .NET which contra rest the #8 owasp top 10 security issue.

Use Anti-forgery Helpers

There are 2 methods which a developer can use to avoid CSFR attacks, these are Html.AntiForgeryToken() and the filter [ValidateAntiForgeryToken]. To use these features, call the AntiForgeryToken method from within your form, and add the ValidateAntiForgeryTokenAttribute to the action method you want to protect. A combination between the Html.AntiForgeryToken() and Ajax.ActionLink is a recommended way to go in order to make sure that no attacker can send a false deletion request

$.ajaxPrefilter(
      function (options, localOptions, jqXHR) {
          if (options.type !== "GET") {
              var token = GetAntiForgeryToken();
              if (token !== null) {
                  if (options.data.indexOf("X-Requested-With") === -1) {
                      options.data = "X-Requested-With=XMLHttpRequest" + (options.data === "") ? "" : "&" + options.data;
                  }
                  options.data = options.data + "&" + token.name + '=' + token.value;
              }
          }
      }
      );

Limitations

  • Users must accept cookies otherwise the [ValidateAntiForgeryToken] will deny their form’s posts
  • Works only with POST request
  • Can be bypassed if the application has XSS vulnerabilities since it will be possible to read _RequestVerificationToken value

References

Jardine, 2013.How to Fix SQL Injection Using Microsoft .Net Parameterized Queries, URL: http://software-security.sans.org/developer-how-to/fix-sql-injection-microsoft-.net-with-parameterized-queries