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Testing for WS HTTP GET parameters/REST attacks (OWASP-WS-005)
HTTP GET parameters.
Brief Summary
Many XML applications are invoked by passing them parameters using HTTP GET queries. These are sometimes known as “REST-style" Web Services. These Web Services can be attacked by passing malicious content on the HTTP GET string (e.g. Extra long parameters (2048 chars), SQL statements/injection or OS Injection parameters). REST = Representational State Transfer).
Description of the Issue
Given that Web services REST are in effect HTTP-In -> WS-OUT at attack patterns are very similar to regular HTTP attack vectors, discussed throughout the guide.
Example: The HTTP request with query string /viewDetail=detail-10293, the HTTP GET parameter is detail- 10293.
Black Box Testing
Say we had a Web Service which accepts the following HTTP GET query string: https://www.ws.com/accountinfo?accountnumber=12039475&userId=asi9485jfuhe92
The resultant response would be similar to:
<?xml version="1.0" encoding="ISO-8859-1"?> <Account="12039475"> <balance>€100</balance> <body>Bank of Bannana account info</body> </Account>
Testing the data validation on this REST web service is similar to generic application testing:
Try vectors such as: https://www.ws.com/accountinfo?accountnumber=12039475' exec master..xp_cmdshell 'net user Vxr pass /Add &userId=asi9485jfuhe92
Grey Box Testing
Upon the reception of a HTTP request the code should do the following:
Check:
- max length and minimum length
- Validate payload:
- If possible implement the following data validation stratigies; "exact match", "known good" and "known bad" in that order.
- Validate parameter names and existance.
References
The OWASP Fuzz vectors list: [1]
