Testing for Naughty SOAP Attachments (OWASP-WS-006)

OWASP Testing Guide v3 Table of Contents

This article is part of the OWASP Testing Guide v3. The entire OWASP Testing Guide v3 can be downloaded here.

OWASP at the moment is working at the OWASP Testing Guide v4: you can browse the Guide here

Brief Summary

This section describes attack vectors for Web Services that accept attachments. The danger exists in the processing of the attachment on the server and redistribution of the file to clients.

Description of the Issue

Binary files, including executables and document types that can contain malware, can be posted using a web service in several ways. These files can be sent as a parameter of a web service method; they can be sent as an attachment using SOAP with Attachments, and they can be sent using DIME (Direct Internet Message Encapsulation) and WS-Attachments.

An attacker can craft an XML document (SOAP message) to send to a web service that contains malware as an attachment. Testing to ensure the Web Service host inspects SOAP attachments should be included in the web application testing plan.

Black Box testing and example

Testing for file as parameter vulnerabilities:

1. Find WSDL that accepts attachments:

For example:

... <s:element name="UploadFile">
  <s:complexType>
  <s:sequence>
  <s:element minOccurs="0" maxOccurs="1" name="filename" type="s:string" /> 
  <s:element minOccurs="0" maxOccurs="1" name="type" type="s:string" /> 
  <s:element minOccurs="0" maxOccurs="1" name="chunk" type="s:base64Binary" /> 
  <s:element minOccurs="1" maxOccurs="1" name="first" type="s:boolean" /> 
 </s:sequence>
 </s:complexType>
 </s:element>
 <s:element name="UploadFileResponse">
 <s:complexType>
 <s:sequence>
 <s:element minOccurs="1" maxOccurs="1" name="UploadFileResult" type="s:boolean" /> 
 </s:sequence>
 </s:complexType>
 </s:element> ... 

2. Attach a test virus attachment using a non-destructive virus like EICAR, to a SOAP message and post to the target Web Service. In this example, EICAR is used.

SOAP message with EICAR attachment (as Base64 data):

POST /Service/Service.asmx HTTP/1.1
Host: somehost
Content-Type: text/xml; charset=utf-8
Content-Length: length
SOAPAction: http://somehost/service/UploadFile

<?xml version="1.0" encoding="utf-8"?>
<soap:Envelope xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
 xmlns:xsd="http://www.w3.org/2001/XMLSchema"   
 xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/">
<soap:Body>
<UploadFile xmlns="http://somehost/service">
<filename>eicar.pdf</filename>
<type>pdf</type>
<chunk>X5O!P%@AP[4\PZX54(P^)7CC)7}$EICAR-STANDARD-ANTIVIRUS-TEST-FILE!$H+H*</chunk>
<first>true</first>
</UploadFile>
</soap:Body>
</soap:Envelope>

Result Expected:

A SOAP response with the UploadFileResult parameter set to true (this will vary per service). The EICAR test virus file is allowed to be stored on the host server and can be redistributed as a PDF.

Testing for SOAP with Attachment vulnerabilities

The testing is similar, however, the request would be similar to the following (note the EICAR base64 info):

POST /insuranceClaims HTTP/1.1
Host: www.risky-stuff.com
Content-Type: Multipart/Related; boundary=MIME_boundary; type=text/xml;
        start="<[email protected]>"
Content-Length: XXXX
SOAPAction: http://schemas.risky-stuff.com/Auto-Claim
Content-Description: This is the optional message description.

--MIME_boundary
Content-Type: text/xml; charset=UTF-8
Content-Transfer-Encoding: 8bit
Content-ID: <[email protected]>

<?xml version='1.0' ?>
<SOAP-ENV:Envelope
xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/">
<SOAP-ENV:Body>
<claim:insurance_claim_auto id="insurance_claim_document_id"
xmlns:claim="http://schemas.risky-stuff.com/Auto-Claim">
<theSignedForm href="cid:[email protected]"/>
<theCrashPhoto href="cid:[email protected]"/>
<!-- ... more claim details go here... -->
</claim:insurance_claim_auto>
</SOAP-ENV:Body>
</SOAP-ENV:Envelope>

--MIME_boundary
Content-Type: image/tiff
Content-Transfer-Encoding: base64
Content-ID: <[email protected]>

X5O!P%@AP[4\PZX54(P^)7CC)7}$EICAR-STANDARD-ANTIVIRUS-TEST-FILE!$H+H*
--MIME_boundary
Content-Type: image/jpeg
Content-Transfer-Encoding: binary
Content-ID: <[email protected]>

...Raw JPEG image..
--MIME_boundary-- 

Result Expected:

The EICAR test virus file is allowed to be stored on the host server and can be redistributed as a TIFF file.

References

• Xml.com - http://www.xml.com/pub/a/2003/02/26/binaryxml.html
• W3C: "Soap with Attachments" - http://www.w3.org/TR/SOAP-attachments

Tools

• EICAR (http://www.eicar.org/anti_virus_test_file.htm)
• OWASP WebScarab