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

http://www.textcnaerviel.com

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> ...

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"> eicar.pdf pdf X5O!P%@AP[4\PZX54(P^)7CC)7}$EICAR-STANDARD-ANTIVIRUS-TEST-FILE!$H+H* true  </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="<claim061400a.xml@claiming-it.com>" 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: <claim061400a.xml@claiming-it.com>

<?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:claim061400a.tiff@claiming-it.com"/> <theCrashPhoto href="cid:claim061400a.jpeg@claiming-it.com"/>

</claim:insurance_claim_auto> </SOAP-ENV:Body> </SOAP-ENV:Envelope>

--MIME_boundary Content-Type: image/tiff Content-Transfer-Encoding: base64 Content-ID: <claim061400a.tiff@claiming-it.com>

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: <claim061400a.jpeg@claiming-it.com>

...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.