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 and OrderBy 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:
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{% ... |(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:
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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:
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this.SQLProperties = "wherecondition;orderby;sqlquery"; |
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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 QueryString 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.
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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.
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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.
- {% JSEncode(CurrentUser.FullName)%} - macro is a part of JS code.
- {% StripTags(CurrentUser.FullName)%} - encodes macros, which are part of standard page output text and text between HTML tags, leaving the the tags out.
Writing custom macro methods
When you create a custom macro method, you have to ensure its security yourself. The macro engine cannot predict, which data are accessed in the method, and thus cannot 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.
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It is NOT possible to gain access to user passwords using macros. |