Macros and security

Macros are an essential part of Kentico. You can read more about them in the Macro expressions chapter. This page focuses on the security mechanisms and best practices related to macros.

Signing macros

Whenever a user saves a complex macro expression, the system automatically adds a security signature. This signature contains an identifier of the macro’s author (the user name or an assigned macro identity) and a hash of the given expression.

You can recognize signed macro expressions by the # character, which the system automatically inserts before the closing %} parentheses when saving the text containing the macro:

  • {%CurrentSite.SiteID #%}

For illustration, a signed macro may look like this in the database:

  • {%CurrentSite.SiteID|(user)administrator|(hash)9056b7b76629a47a660c40cc2e5b0d92a13d0f9bce178847ca412c3a585552a1%} –  OR –
  • {%CurrentSite.SiteID|(identity)GlobalAdministrator|(hash)e3402fe14374ab15d119dddbb6c831ce3d2ef55bd8e70ce8eb80994f4e6ad18b%}

Hashing is omitted when submitting very simple macros (e.g., {%FullName%}). Macros are signed only when they contain an indexer or a dot.

The system checks the macro signature when accessing an object through a different object (for example the user settings of a user object) and evaluates whether the user (identified by the signature) has permissions to execute the macro. 

The best practice is to use the least privilege approach – submit macros signed by a user who has access only to the required objects and nothing else.

SQL injections

Macros can often become part of SQL queries, for example in WhereCondition and OrderBy fields of web part properties, which can lead to SQL injection vulnerability.

SQL injection protection in web part properties

Some web part properties are secured against SQL injection attacks, which may affect how macros are resolved in specific cases. By default, this is applied to macros entered into the WhereCondition, OrderBy and Columns web part properties.

If the macro returns a string value that contains single quote characters (‘), they will be escaped and replaced by two single quotes (’’). This may cause an SQL syntax error if you are using the macro to dynamically insert a part of a query, such as a WHERE clause.

It is possible to disable single quote escaping for a specific macro expression by adding the handlesqlinjection parameter and setting its value to false:

{% ... |(handlesqlinjection)false %}

To disable SQL escaping globally for all properties of a specific type of web part, edit its code behind file (e.g. ~/CMSWebParts/Viewers/Documents/cmsrepeater.ascx.cs for the Repeater web part) and add the following line of code into the SetupControl() method:

this.SQLProperties = "";

The SQLProperties property is inherited from the CMSAbstractWebPart base class by all web parts, but you can override its value to set which properties the system protects.

If you wish to enable SQL escaping for additional web part properties, enter their names into the SQLProperties value separated by semicolons, for example:

this.SQLProperties = "wherecondition;orderby;columns;sqlquery";

Disabling SQL protection may create security vulnerabilities if the macro resolves its value according to data that can be modified by the website’s users, such as in the case of query string macros.

SQL injection protection outside of web part properties

If you are using macros outside of web part properties or you have disabled SQL escaping, then you need to use the SQLEscape method to handle SQL macros.

WHERE UserName LIKE '%{% SQLEscape(QueryString.GetValue("test", ""))#%}%'

However, if you expect a different data type than string (for example an integer), you need to convert the macro to the correct data type. The SQLEscape method is useless in this case.

WHERE UserID = {% ToInt(QueryString.GetValue("test", ""), 0)#%}

Output encoding of macros

Macro encoding is an essential protection against XSS. You must encode output macros properly, unless you want to display some HTML code using the particular macro. There are several methods for encoding macros in Kentico:

  • {% UrlEncode(CurrentUser.FullName) %} – macro is encoded into the query URL.
  • {% HTMLEncode(CurrentUser.FullName) %} – macro is a part of standard page output text and text between HTML tags.
  • {% JSEscape(CurrentUser.FullName) %} – macro is a part of JS code.

Writing custom macro methods

When creating a custom macro method, you need to ensure security yourself. The macro engine cannot predict which data is accessed in the method, and thus cannot properly secure the method.

Unsafe macros

Query macros, cookie macros and data macros (information from the database, e.g. user display name) and their equivalent properties can be potentially dangerous. When you use these macros, you have to secure them against SQL injection and XSS.

It is NOT possible to gain access to user passwords using macros.