XML Denial of Service (XDoS) can be applied to any technology that
utilizes XML data. This is, of course, most distributed systems technology
including Java, .Net, databases, and so on. XDoS is most closely associated
with web services, SOAP, and Rest, because remote service requesters can
post malicious XML payloads to the service provider designed to exhaust the
service provider's memory, CPU, and/or disk space. The main weakness in XDoS
is that the service provider generally must inspect, parse, and validate the
XML messages to determine routing, workflow, security considerations, and so
on. It is exactly these inspection, parsing, and validation routines that
XDoS targets.
There are three primary attack vectors that XDoS can navigate
Target CPU through recursion: attacker creates a recursive payload and
sends to service provider
Target memory through jumbo payloads: service provider uses DOM to
parse XML. DOM creates in memory representation of XML document, but
when document is very large (for example, north of 1 Gb) service
provider host may exhaust memory trying to build memory objects.
XML Ping of death: attack service provider with numerous small files
that clog the system.
All of the above attacks exploit the loosely coupled nature of web
services, where the service provider has little to no control over the
service requester and any messages the service requester sends.
Description
