WebApp Sec mailing list archives
Re: GET and POST Methods Accepted
From: Serg Belokamen <serg.belokamen () gmail com>
Date: Thu, 13 Oct 2005 13:39:03 +1000
Hi, I am not sure about Perl (cgi) but I know in PHP there are a number of global arrays such as $_POST, $_GET and $_REQUEST. POST and GET arrays keep corresponding data and developer decided on the order and importance of processing the values. For example if system doesnt use GET at all, then $_POST array is the only one that is being used and thus no GET values are utilised (user can attempt as much as they like). $_REQUEST array is a little different and in my opinon dangerous, since that addresses exactly what you mentioned. All input values from POST and GET methods get stored there and used interchangeably. This is when it could be possible to perform XSS attack assuming the processing order on the server level (described later) is incorrect. It is also largly depends on the environment setup. In case of PHP, system admins. can define a setting that states the order input gets processed (GET, then POST, then...) so all ilegal values would be overiden. This is usually left as default by the way. Finaly, there are systems that allow this behaviour since they want to enable users to issue automated requests from remote scripts and doing it in a single GET request makes perfect scence. So bottom line, it completely depends on the aplication and its purpose. My AU$0.2, hope it helped. Serg P.S. If site is explicitly saying "use POST" and get gets processed regardless it is most likely that something like $_REQUEST is being used and not specific HTTP method value arrays. On 13/10/05, Welsh, Ed <Ed.Welsh () fishnetsecurity com> wrote:
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 I have begun stating this as an issue during assessments and wonder what you folks think of it. Web sites are allowing a switch in method for requests and still processing the input. I have been able to analyze a site login form which is specified to use POST method and craft a URL (GET of course) that the web server will still accept and process. If the site will accept the GET method for form data and is vulnerable to XSS, the attack surface greatly increases over a site that is vulnerable to XSS but only accepts the POST method. POST is still attackable, but it becomes more complicated than simply emailing a link. There used to be a substantial difference in how variables received via GET vs POST were stored. That difference had to be accounted for in the server code and would not lend itself to arbitrary method switching. This may disclose some of my ignorance, but it seems something has changed and application systems are treating input values the same regardless of the method. I have seen this recently on J2EE sites and CGI (PERL, PYTHON, Binary). Do any of you test for this issue - what are your results? Any other discussion is valued. Ed Welsh -----BEGIN PGP SIGNATURE----- Version: PGP Desktop 9.0.2 (Build 2424) iQEVAwUBQ01sNlcLJH9lmXCIAQgowAgAz4eUyEgXKIk7aveM09znkQVy4rUm640w 7M9XwRC2XnHo49MIc2CLsBa6d2yFbBsfhjw0L+hNRhWVnWRZsBv1Z+k61slZK0QU qeQS4f3+6iVgqesLsRtFG6d7DI50tDuVFpIkrwosLL4OkVLFHrA56x3BkrByverx pYa6SMihDMrVRl5dvIGecijObexHLM03gEembyTB2XJC5h+5Z3UNaGqt6kf4X0Dz Y3pfBdQ5OH8XdVReW+AZJAimd40g/+qiiYhMbeKJzC0p3/7Yw1VOG9//OPKFi/wY q79op1KikDcZ7l29YdI323gfI2G5WS3rJsdP00wM9X2IFEsdYR7n3A== =zb7v -----END PGP SIGNATURE-----
Current thread:
- GET and POST Methods Accepted Welsh, Ed (Oct 12)
- Re: GET and POST Methods Accepted Joe Teff (Oct 12)
- Re: GET and POST Methods Accepted christopher baus (Oct 12)
- Re: GET and POST Methods Accepted Stephen de Vries (Oct 13)
- Re: GET and POST Methods Accepted christopher baus (Oct 13)
- Re: GET and POST Methods Accepted Stephen de Vries (Oct 13)
- Re: GET and POST Methods Accepted Damien Watson (Oct 13)
- Re: GET and POST Methods Accepted Serg Belokamen (Oct 13)
- Re: GET and POST Methods Accepted Eoin Keary (Oct 13)
- Re: GET and POST Methods Accepted Amit Klein (AKsecurity) (Oct 13)
- Re: GET and POST Methods Accepted John GALLET (Oct 13)
- Re: GET and POST Methods Accepted Eoin Keary (Oct 13)
- Re: GET and POST Methods Accepted John GALLET (Oct 13)
- Re: GET and POST Methods Accepted Eoin Keary (Oct 13)
- Re: GET and POST Methods Accepted Paul Laudanski (Oct 18)
- <Possible follow-ups>
- RE: GET and POST Methods Accepted Derick Anderson (Oct 13)
- RE: GET and POST Methods Accepted christopher baus (Oct 13)
- RE: GET and POST Methods Accepted Joe Teff (Oct 13)
- RE: GET and POST Methods Accepted christopher baus (Oct 13)
- RE: GET and POST Methods Accepted Derick Anderson (Oct 14)