Applications that depend on user input to create a SQL statement — concatenating the user input to the SQL query — can become vulnerable to SQL Injection attacks, much like those common to web applications.

SQL Injection is a technique that exploits a security vulnerability occurring in the database layer of an application. The vulnerability is present when user input is either incorrectly filtered for string literal escape characters embedded in SQL statements or user input is not strongly typed and thereby unexpectedly executed.

Fortunately, there is a simple solution to the problem: use parameterised SQL Statements. Parameterised statements not only make your applications more secure and run more efficiently, but they also enable you to use objects, rather than literal values, in your queries. SQL injection can’t happen because the parameter values are treated explicitly as substituted values, rather than becoming part of the literal statement text.

Parameters in a SQL statement can be either named or unnamed. Below are examples of both types of statement in ActionScript and JavaScript.

Named Parameters

A named parameter has a specific name that is used to match the parameter value to its placeholder location in the SQL statement text. A parameter name consists of the colon (:) or an at (@) character followed by the variable’s name:

ActionScript 3

var conn:SQLConnection = new SQLConnection();
var stmt:SQLStatement = new SQLStatement();
stmt.sqlConnection = conn;
stmt.text = "INSERT INTO user VALUES(@title, @firstname, @lastname)";
stmt.parameters["@title"] = "Mr";
stmt.parameters["@firstname"] = "Simon";
stmt.parameters["@lastname"] = "Whatley";
stmt.execute()

JavaScript

var conn = new air.SQLConnection();
var stmt = new air.SQLStatement();
stmt.sqlConnection = conn;
stmt.text = "INSERT INTO user VALUES(@title, @firstname, @lastname)";
stmt.parameters["@title"] = "Mr";
stmt.parameters["@firstname"] = "Simon";
stmt.parameters["@lastname"] = "Whatley";
stmt.execute()

Unnamed Parameters

As an alternative to using explicit named parameters, you can also use implicit unnamed parameters. To use an unnamed parameter you simply designate a parameter in the SQL statement using a question mark (?) character. Each parameter is assigned a numeric index, according to the order in which the parameters appear in the SQL statement, starting with index 0 (zero) for the first parameter.

ActionScript 3

var conn:SQLConnection = new SQLConnection();
var stmt:SQLStatement = new SQLStatement();
stmt.sqlConnection = conn;
stmt.text = "INSERT INTO address VALUES(?, ?, ?, ?)";
stmt.parameters[0] = "123 Main Street";
stmt.parameters[1] = "Sometown";
stmt.parameters[2] = "12345";
stmt.parameters[3] = "USA";
stmt.execute()

JavaScript

var conn = new air.SQLConnection();
var stmt = new air.SQLStatement();
stmt.sqlConnection = conn;
stmt.text = "INSERT INTO address VALUES(?, ?, ?, ?)";
stmt.parameters[0] = "123 Main Street";
stmt.parameters[1] = "Sometown";
stmt.parameters[2] = "12345";
stmt.parameters[3] = "USA";
stmt.execute()

Note: Use clearParameters() to empty the statement parameters array; e.g. stmt.clearParameters().

Advantages

1. Performance – A SQL statement that uses parameters can execute more efficiently compared to one that dynamically creates the SQL text each time it executes. The performance improvement is because the statement is prepared once and then executed multiple times using different parameter values, without needing to recompile the SQL statement. A comparison can be draw with database stored procedures.
2. Data Typing – Parameters are used to allow for typed-substitution of values that are unknown at the time the SQL statement is constructed. The use of parameters is the only way to guarantee the type (storage class) for a value passed to the database. Using paramters therefore, implies better performance and security. When parameters are not used, the runtime attempts to convert all values from their text representation to a type based on the associated column’s type.
3. Security – The AIR application is not vulnerable to SQL injections so common to web applications.

Why should you be worried about security?

The Web is changing many of the assumptions that people have historically made about computer security and publishing. As the Internet makes it possible for web servers to publish information to millions of users, it also makes it possible for computer hackers, crackers, criminals, vandals, and other “bad guys” to break into the very computers on which the web servers are running. Once subverted, web servers can be used by attackers as a launching point for conducting further attacks against users and organisations.

It is considerably more expensive and more time-consuming to recover from a security incident than to take preventative measures ahead of time.

This blog post started on the premise of protecting your website from a SQL Injection Attack. However, it is also appropriate to discuss, at a relatively high level, how to secure your server architecture and applications.

Server-Level Security

• Separate web- and database-servers on to different physical machines.
• Secure the web- and database-servers with traditional techniques. Only authorised accounts should have the capabilities to run tasks on the machine. That means not giving admin-rights to the user account.
• Keep servers up-to-date with the latest patches and software releases.
• Minimise the number of services running on the server. This means limiting the services to only those required for the web- or database-servers to function.
• Secure information in transit between servers. This may mean physically securing the network to prevent evesdropping via encryption or obfuscating the data amongst innocuous ‘noise’.
• Secure the database server behind a firewall.

Application-Level Security

• Separate ColdFusion, the webserver and database server user accounts. They should never be under the same system account.
• Create a database user specifically for your ColdFusion datasource and restrict it to only the activities required for the application. The user should not have database-owner rights, access to databases not relating to the application or access to the system tables.
• Revoke privileges in the ColdFusion datasource definition to prevent the SQL commands CREATE, DROP, GRANT, REVOKE and ALTER.
• General settings in the ColdFusion Administrator:
  • Check the Disable access to internal ColdFusion Java components option.
  • Check the Enable Global Script Protection option.
  • Add a Missing Template Handler.
  • Add a Site-wide Error Handler.
  • Reduce the Maximum size of post data from 100MB.
  • Enable Timeout Requests, and set to 60 seconds or less.
  • Disable Robust Exception Handling on production servers.

Code-Level Security

• Application.cfc – Set the scriptProtect Application variable to true to enable application-wide cross-site script protection.
• CFQueryParam – This tag, importantly, verifies the data type of a query parameter and, for RDBMSs that support bind variables, enables ColdFusion to use bind variables in the SQL statement. Bind variable usage enhances performance when executing a cfquery statement multiple times.

  <cfquery name="qry" datasource="#APPLICATION.dsn#">
  SELECT column1, column2, column3
  FROM tableName
  WHERE column4 = <cfqueryparam value="#variable1#" cfsqltype="cf_sql_bit" />
  AND column5 LIKE <cfqueryparam value="%#variable2#%" cfsqltype="cf_sql_varchar" maxlength="200" />
  AND column6 IN (<cfqueryparam value="#variable3#" cfsqltype="cf_sql_integer" list="true" />)
  </cfquery>

  There are limitations to the use of the cfqueryparam tag. In ColdFusion 7 for example, you cannot use them in queries using the cachedWithin attribute. Similarly, they cannot be used in ORDER BY clauses, although the use of conditional logic should resolve the need for order by variables.

• Functions – As a rule of thumb, validate all the data being passed into a query prior to it being used. ColdFusion MX 7 saw the introduction of the isValid() function. This function tests whether a value meets a validation or data type rule and can be used to replace a large number of type-specific functions such as isArray(), isBinary(), isBoolean(), isDate(), isNumeric() and isSimpleValue() etc.
• Stored Procedures – I often favour the use of stored procedures over standard queries. Not only do they add an additional level of performance, they provide an additional level of security; ColdFusion does not do any raw processing of queries in the web code, it simply passes variables down the wire to the database server.

Additional Resources

• Web Security, Privacy and Commerce
• O’Reilly’s The Web Application Hacker’s Handbook
• Adobe’s whitepaper – ColdFusion 8 Developer Security Guidlines (PDF, 281k)
• Adobe’s whitepaper – ColdFusion 7 Developer Security Guidlines (PDF, 217k)
• Adobe DevNet – Learning Stored Procedure Basics in ColdFusion 8
• 0×000000 # The Hacker Webzine’s article on Attacking ColdFusion
• Three part series from Mark Kruger (ColdFusion Muse) – Part 1, Part 2, Part 3
• Brad Wood’s article on CFQueryParam is not just for security.