XML format check

The XML Format check examines the XML format of incoming requests and blocks those requests that are not well formed or that do not meet the criteria in the XML specification for properly-formed XML documents. Some of those criteria are:

  • An XML document must contain only properly-encoded Unicode characters that match the Unicode specification.
  • No special XML syntax characters—such as < , > and &—can be included in the document except when used in XML markup.
  • All begin, end, and empty-element tags must be correctly nested, with none missing or overlapping.
  • XML element tags are case-sensitive. All beginning and end tags must match exactly.
  • A single root element must contain all the other elements in the XML document.

A document that does not meet the criteria for well-formed XML does not meet the definition of an XML document. Strictly speaking, it is not XML. However, not all XML applications and web services enforce the XML well-formed standard, and not all handle poorly-formed or invalid XML correctly. Inappropriate handling of a poorly-formed XML document can cause security breaches. The purpose of the XML Format check is to prevent a malicious user from using a poorly-formed XML request to breach security on your XML application or web service.

If you use the wizard or the GUI, in the Modify XML Format Check dialog box, on the General tab you can enable or disable the Block, Log, and Statistics actions.

If you use the command-line interface, you can enter the following command to configure the XML Format Check:

  • set appfw profile <name> -xmlFormatAction [**block**] [**log**] [**stats**] [**none**]

You cannot configure exceptions to the XML Format check. You can only enable or disable it.

XML format check

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