Adobe 38043740 Developing Applications - Page 421

DEVELOPING COLDFUSION 9 APPLICATIONS 416 Accessing and Using Data Enhancing security with cfqueryparam Some DBMSs let you send multiple SQL statements in a single query. However, hackers sometimes try to modify URL or form variables in a dynamic query by appending malicious SQL statements to existing parameters. Be aware of potential security risks when you pass parameters in a query string. These risks can exist in many development environments, including ColdFusion, ASP, and CGI. Using the cfqueryparam tag can reduce this risk. About query string parameters When you let a query string pass a parameter, ensure that only the expected information is passed. The following ColdFusion query contains a WHERE clause, which selects only database entries that match the last name specified in the LastName field of a form: SELECT FirstName, LastName, Salary FROM Employee WHERE LastName='#Form.LastName#' Someone could call this page with the following malicious URL: http://myserver/page.cfm?Emp_ID=7%20DELETE%20FROM%20Employee The result is that ColdFusion tries to execute the following query: SELECT * FROM Employee WHERE Emp_ID = 7 DELETE FROM Employee In addition to an expected integer for the Emp_ID column, this query also passes malicious string code in the form of a SQL statement. If this query successfully executes, it deletes all rows from the Employee table-something you definitely do not want to enable by this method. To prevent such actions, evaluate the contents of query string parameters. Using cfqueryparam You can use the cfqueryparam tag to evaluate query string parameters and pass a ColdFusion variable within a SQL statement. This tag evaluates variable values before they reach the database. You specify the data type of the corresponding database column in the cfsqltype attribute of the cfqueryparam tag. In the following example, because the Emp_ID column in the cfdocexamples data source is an integer, you specify a cfsqltype of cf_sql_integer: SELECT * FROM Employee WHERE Emp_ID = The cfqueryparam tag checks that the value of Emp_ID is an integer data type. If anything else in the query string is not an integer, such as a SQL statement to delete a table, the cfquery tag does not execute. Instead, the cfqueryparam tag returns the following error message: Invalid data '7 DELETE FROM Employee' for CFSQLTYPE 'CF_SQL_INTEGER'. Using cfqueryparam with strings When passing a variable that contains a string to a query, specify a cfsqltype value of cf_sql_char, and specify the maxLength attribute, as in the following example: Last updated 1/20/2012