XML Structural Attacks

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XML Structural Attacks:

Attacking the strucytre of the SOAP message in an attempt to circumvent the schema or XML parser.

Attackers can create XML documents which are structured in such a way as to create a DoS attacks on the receiving server by tying up memory and CPU resources.

XML messages which contain large amounts of parameters can cause problems with parsers. Parsers are CPU intensive, a problem that has not been addressed as of yet (via XML acceleration).

This category of attack also includes XML documents which are not "well-formed": With overlapping XML attributes. The end tag </element> is placed in the middle of another element in the SOAP document. This attack can also occur with open tags that have no matching end tags.

Perticularly but not exclusivley With DOM based parsing oversized attachments can cause an issue. DOM parsers load the complete document.message into memory prior to parsing. This is memory intensive and may cause DOS )or performance degradeation with a large message being processed by DOM.

Paradox: You have to parse before you validate. Prior to validation, a document must be parsed against a schema, but in parsing the document a violation may occur via a structural attack.