This article dissects the recent Logjam paper from a pentesting viewpoint to reveal a number of different factors that affect the impact of the vulnerability. One of those factors includes the use of common primes and I’ve included a small change to OpenSSL that you can use to look out for this. Continue reading
Tag Archives: pentesting
When HTML Encoding Helped XSS
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
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
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
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
Testing for TCP/IP Timestamps
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
The Small Print for OpenSSL legacy_renegotiation
The other day my attention was drawn to a switch in OpenSSL called -legacy_rengotation
. I pulled up the built-in help for s_client
and, sure enough, there it was. So I trawled back through the release notes and it looked to have been there since version 0.9.8m. I couldn’t believe that I hadn’t spotted this before: it looked like the perfect way to test for insecure renegotiation without the faff of having to recompile OpenSSL or use an older version. But after a bit of testing this proved to be a red herring… Continue reading
SQL Injection in Search Fields
A quick posting about a fun SQL injection I cracked last week (of course, it’s only when you’ve cracked them that they’re fun!). A colleague had found the classic sign of a problem – add a single quote and you get an error – but was having no luck doing anything more. I was getting nowhere with my test so I thought I’d take a look for a change of scene. The input field was in a search box so, for example, search=keyword'
returned an error but search=keyword''
was fine. Anything more exciting than that, however, such as search=keyword' and '1'='1
, didn’t seem to work as expected: in this case, an error was returned instead of the same set of results that the normal search=keyword
produced. Continue reading
SSL/TLS Checklist for Pentesters
I gave a presentation at BSides MCR 2014 on the subject of SSL and TLS checks from a pentesting viewpoint. The idea was to focus on the pitfalls of testing, why the tools may let you down and how to check for issues manually (as much as possible), often using OpenSSL. Continue reading
Three Cheers for DirBuster
Not exactly wizard stuff today, more like back to basics perhaps – but sometimes they’re worth revisiting. I’ve had some good DirBuster finds three tests in a row so I thought I’d write them up as a case study. It’s a reminder that there’s some very low-hanging fruit out there that may not always get picked. I’ve also put together a walk-through for many of DirBuster’s features and I aim to show that, as with many tools, a few minutes of manual work can produce a faster set of more meaningful results. Continue reading