Author Archives: Jerome

The Why Behind Web Application Penetration Test Prerequisites

Leave a reply

Before a web application penetration test is scheduled to start, the company performing the test will contact the client with a list of considerations and configurations that are required before the test can begin. Sadly, the importance of these can be lost in amongst the frenzy of ensuring the system is ready on time, or perhaps because the items listed don’t seem necessary. My whitepaper aims to address the latter, providing an explanation of the why behind the prerequisites, together with some general pre-test points for consideration. It is aimed at anyone who is charged with preparing for a web application penetration test, from project managers to developers, and as such it is written for both technical and non-technical readers. The paper ends with a one-page quick reference guide to help with future tests, which is available as a standalone document here.

Testing for Anti-Virus on File Upload

3 Replies

One of the issues on a standard web app checklist is to test whether or not an application that supports file upload is scanning those files for malware. This article reviews the methodology and highlights the danger of corrupting an EICAR test file so that it no longer acts as a valid test. It is based on an internal presentation I gave, the slides for which are here. Continue reading →

Testing for POODLE_TLS Manually

9 Replies

Testing for the original POODLE vulnerability was easy because it was an inherent problem with SSLv3, so if you find SSLv3 enabled then you’ve found POODLE (although other factors such as cipher suite preference have a role to play – see my previous post). Like Heartbleed, though, testing for POODLE over TLS is conceptually easy but it falls within a class of flaws that requires bespoke tools as an unpatched version of openssl, for example, won’t do what you want it to do. This article discusses how the Python tlslite library can be used to test for POODLE_TLS – and so much more. Continue reading →

When HTML Encoding Helped XSS

1 Reply

Recently I was pentesting a web app that had an unauthenticated XSS vulnerability but there was some heavy filtering in place. Nonetheless I was able to achieve session fixation using a combination of a technique I previously explained and some fun filter workarounds – including using the application’s own defensive HTML encoding to create a working XSS payload! Continue reading →

SS-Hell: the Devil is in the Details

Leave a reply

Penetration test reports commonly contain mention of vulnerabilities in SSL/TLS (hereafter referred to as just SSL). In many cases, this is due to system administrators not understanding the details of these services’ configuration and assuming that simply using SSL provides security. The issues identified during penetration tests are usually low in severity, as an average attacker would find them difficult to exploit, but they should be taken seriously to ensure that data in transit is properly secured. If something’s worth doing, it’s worth doing well. This whitepaper, co-written with Will Alexander, discusses how organisations can avoid SSL issues commonly found during penetration tests, ensure that data in transit is properly secured and ultimately instil in users a sense of confidence that their information is adequately protected.

Thoughts on Testing for POODLE

Leave a reply

I recently did an internal presentation on POODLE – what the flaw is and how to test for it – and a version of the slides can be found here. Obviously much has been written about the vulnerability, its mitigations and what the future holds. What follows expands on the testing aspect of the presentation, with a few pointers on manual checks if you feel you need to verify or clarify – and possibly even add to – what the tools are telling you. Continue reading →

Testing for Cipher Suite Preference

Leave a reply

It’s often important to know which SSL/TLS cipher suite is preferred by a server to alter the risk rating of a particular issue. For POODLE, if the server prefers RC4 ciphers over SSLv3 connections then it’s very unlikely that a connection will be vulnerable to POODLE. Similarly, if a server prefers block ciphers then reporting RC4 support should be appropriately adjusted. Occasionally tools conflict over which cipher suite is preferred so I thought I’d write up how to resolve this manaully in the spirit of the SSL/TLS manual cheatsheet. Continue reading →

POODLE and the TLS_FALLBACK_SCSV Remedy

6 Replies

The POODLE attack announced very recently depends largely on a protocol downgrade attack (which I covered in my SSL/TLS presentation at BSides). I don’t think this aspect of TLS security was widely appreciated – but it is now! It’s a fair bet that any technical article about POODLE includes the phrase “TLS_FALLBACK_SCSV” as a remedy. This article discusses the mechanism proposed to protect us from attackers forcing TLS downgrades. NEW (16/10/14): while I was writing this I thought of a small but potential compatibility problem, which in fact could do us all a favour. I checked with the authors of the RFC and Adam Langley was kind enough to reply back so I’ve added added a new section below. Continue reading →

Testing for TCP/IP Timestamps

2 Replies

It always used to be a stock joke in my old workplace that if you were having a tough time finding issues in a pentest then you could always rely on “TCP/IP timestamps”. Recently I did a re-test (based on another company’s report) that included this issue and found that it’s easy for this to be a false positive. I thought I’d write up this finding – as much for the journey I took through Nessus, Nmap, hping and Wireshark as for the result itself. Continue reading →