Category: Hacking


Blast from the Past: How Attackers Compromised Zimbra With a Patched Vulnerability

Last year, I worked on a vulnerability in Zimbra (CVE-2022-41352 - my AttackerKB analysis for Rapid7) that turned out to be a new(-ish) exploit path for a really old bug in cpio - CVE-2015-1194. But that was patched in 2019, so what happened?

(I posted this as a tweet-thread awhile back, but I decided to flesh it out and make it into a full blog post!)

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BSidesSF CTF 2021 Author writeup: glitter-printer, a buffer underflow where you modify the actual code

Hi Everybody!

This is going to be a challenge-author writeup for the Glitter Printer challenge from BSides San Francisco 2021.

First, a bit of history: the original idea I had behind Glitter Printer was to make a video game challenge involving cartridge-swap, where I’d write a handful of simple video games in 100% x86 code with no imports or anything (like an old fashioned cartridge game), and the player could swap between them without memory being re-initialized. Folks used to do this sorta thing on NES, and maybe I’ll use it in a future challenge, but I decided to make this a bit simpler.

While experimenting with writing libraries without libc, I realized just how much work it was going to be to write a bunch of games, and decided to simplify. My next ide was to write a “driver” type thing, where a blob of code is loaded into +RWX memory and the player could go wild on it. The the name Glitter Printer came across my radar, I don’t even remember why, and that gave me the idea to do an LPR server.

That’s quite the background!

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BSidesSF CTF 2021 Author writeup: secure-asset-manager, a reversing challenge similar to Battle.net bot dev

Hi Everybody!

This is going to be a challenge-author writeup for the Secure Asset Manager challenge from BSides San Francisco 2021.

It’s designed to be a sort of “server management software”. I sort of chose that theme to play off the Solarwinds thing, the theme wasn’t super linked to the challenge.

The challenge was to analyze and reverse engineer a piece of client-side software that “checks in” with a server. For the check-in, the client is required to “validate” itself. The server sends a random “challenge” - which is actually a block of randomized x86 code - and that code used to checksum active memory to prevent tampering. If anybody reading this worked on bots for the original Starcraft (and other Battle.net games), this might seem familiar! It’s based on Battle.net’s CheckRevision code.

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BSidesSF CTF 2021 Author writeup / shellcode primer: Runme, Runme2, and Runme3

Hi Everybody!

This is going to be a writeup for the Runme suite of challenges from BSides San Francisco 2021.

The three challenges I’ll cover are runme, runme2, and runme3, which are increasingly difficult write-shellcode challenges. As always, the binary and info the player gets is in the respective distfiles/ folder, and source is in challenge/.

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BSidesSF CTF author writeup: genius

Hey all,

This is going to be an author’s writeup of the BSidesSF 2019 CTF challenge: genius!

genius is probably my favourite challenge from the year, and I’m thrilled that it was solved by 6 teams! It was inspired by a few other challenges I wrote in the past, including Nibbler. You can grab the sourcecode, solution, and everything needed to run it yourself on our Github release!

It is actually implemented as a pair of programs: loader and genius. I only provide the binaries to the players, so it’s up to the player to reverse engineer them. Fortunately, for this writeup, we’ll have source to reference as needed!

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Technical Rundown of WebExec

This is a technical rundown of a vulnerability that we’ve dubbed “WebExec”. The summary is: a flaw in WebEx’s WebexUpdateService allows anyone with a login to the Windows system where WebEx is installed to run SYSTEM-level code remotely. That’s right: this client-side application that doesn’t listen on any ports is actually vulnerable to remote code execution! A local or domain account will work, making this a powerful way to pivot through networks until it’s patched.

High level details and FAQ at https://webexec.org! Below is a technical writeup of how we found the bug and how it works.

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Solving b-64-b-tuff: writing base64 and alphanumeric shellcode

Hey everybody,

A couple months ago, we ran BSides San Francisco CTF. It was fun, and I posted blogs about it at the time, but I wanted to do a late writeup for the level b-64-b-tuff.

The challenge was to write base64-compatible shellcode. There’s an easy solution - using an alphanumeric encoder - but what’s the fun in that? (also, I didn’t think of it :) ). I’m going to cover base64, but these exact same principles apply to alphanumeric - there’s absolutely on reason you couldn’t change the SET variable in my examples and generate alphanumeric shellcode.

In this post, we’re going to write a base64 decoder stub by hand, which encodes some super simple shellcode. I’ll also post a link to a tool I wrote to automate this.

I can’t promise that this is the best, or the easiest, or even a sane way to do this. I came up with this process all by myself, but I have to imagine that the generally available encoders do basically the same thing. :)

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Going the other way with padding oracles: Encrypting arbitrary data!

A long time ago, I wrote a couple blogs that went into a lot of detail on how to use padding oracle vulnerabilities to decrypt an encrypted string of data. It’s pretty important to understand to use a padding oracle vulnerability for decryption before reading this, so I’d suggest going there for a refresher.

When I wrote that blog and the Poracle tool originally, I didn’t actually know how to encrypt arbitrary data using a padding oracle. I was vaguely aware that it was possible, but I hadn’t really thought about it. But recently, I decided to figure out how it works. I thought and thought, and finally came up with this technique that seems to work. I also implemented it in Poracle in commit a5cfad76ad.

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dnscat2 0.05: with tunnels!

Greetings, and I hope you’re all having a great holiday!

My Christmas present to you, the community, is dnscat2 version 0.05!

Some of you will remember that I recently gave a talk at the SANS Hackfest Summit. At the talk, I mentioned some ideas for future plans. That’s when Ed jumped on the stage and took a survey: which feature did the audience want most?

The winner? Tunneling TCP via a dnscat. So now you have it! Tunneling: Phase 1. :)

Info and downloads.

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dnscat2: now with crypto!

Hey everybody,

Live from the SANS Pentest Summit, I’m excited to announce the latest beta release of dnscat2: 0.04! Besides some minor cleanups and UI improvements, there is one serious improvement: all dnscat2 sessions are now encrypted by default!

Read on for some user information, then some implementation details for those who are interested! For all the REALLY gory information, check out the protocol doc!

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How I nearly almost saved the Internet, starring afl-fuzz and dnsmasq

If you know me, you know that I love DNS. I’m not exactly sure how that happened, but I suspect that Ed Skoudis is at least partly to blame.

Anyway, a project came up to evaluate dnsmasq, and being a DNS server - and a key piece of Internet infrastructure - I thought it would be fun! And it was! By fuzzing in a somewhat creative way, I found a really cool vulnerability that’s almost certainly exploitable (though I haven’t proven that for reasons that’ll become apparent later).

Although I started writing an exploit, I didn’t finish it. I think it’s almost certainly exploitable, so if you have some free time and you want to learn about exploit development, it’s worthwhile having a look! Here’s a link to the actual distribution of a vulnerable version, and I’ll discuss the work I’ve done so far at the end of this post.

You can also download my branch, which is similar to the vulnerable version (branched from it), the only difference is that it contains a bunch of fuzzing instrumentation and debug output around parsing names.

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GitS 2015: Giggles (off-by-one virtual machine)

Welcome to part 3 of my Ghost in the Shellcode writeup! Sorry for the delay, I actually just moved to Seattle. On a sidenote, if there are any Seattle hackers out there reading this, hit me up and let’s get a drink!

Now, down to business: this writeup is about one of the Pwnage 300 levels; specifically, Giggles, which implements a very simple and very vulnerable virtual machine. You can download the binary here, the source code here (with my comments - I put XXX near most of the vulnerabilities and bad practices I noticed), and my exploit here.

One really cool aspect of this level was that they gave source code, a binary with symbols, and even a client (that’s the last time I’ll mention their client, since I dislike Python :) )! That means we could focus on exploitation and not reversing!

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GitS 2015: aart.php (race condition)

Welcome to my second writeup for Ghost in the Shellcode 2015! This writeup is for the one and only Web level, “aart” (download it). I wanted to do a writeup for this one specifically because, even though the level isn’t super exciting, the solution was actually a pretty obscure vulnerability type that you don’t generally see in CTFs: a race condition!

But we’ll get to that after, first I want to talk about a wrong path that I spent a lot of time on. :)

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Defcon Quals writeup for byhd (reversing a Huffman Tree)

This is my writeup for byhd, a 2-point challenge from the Defcon Qualifier CTF. You can get the files, including my annotated assembly file, here. This is my second (and final) writeup for the Defcon Qualifiers, you can find the writeup for shitsco here.

This was a reverse engineering challenge where code would be constructed based on your input, then executed. You had to figure out the exact right input to generate a payload that would give you access to the server (so, in a way, there was some exploitation involved).

Up till now, cnot from PlaidCTF has probably been my favourite hardcore reversing level, but I think this level has taken over. It was super fun!

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Defcon Quals writeup for Shitsco (use-after-free vuln)

Hey folks,

Apparently this blog has become a CTF writeup blog! Hopefully you don’t mind, I still try to keep all my posts educational.

Anyway, this is the first of two writeups for the Defcon CTF Qualifiers (2014). I only completed two levels, both of which were binary reversing/exploitation! This particular level was called “shitsco”, and was essentially a use-after-free vulnerability. You can download the level, as well as my annotated IDA file, here.

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PlaidCTF writeup for Pwn-275 – Kappa (type confusion vuln)

Hey folks,

This is my last writeup for PlaidCTF! You can get a list of all my writeups here. Kappa is a 275-point pwnable level called Kappa, and the goal is to capture a bunch of Pokemon and make them battle each other!

Ultimately, this issue came down to a type-confusion bug that let us read memory and call arbitrary locations. Let’s see why!

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PlaidCTF writeup for Web-100 – PolygonShifter (blind sql injection)

Hey folks,

I know in my last blog I promised to do a couple exploit ones instead of doing boring Web stuff. But, this level was really easy and I still wanted to do a writeup, so you’re just going to have to wait a little while longer for my ‘kappa’ writeup!

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PlaidCTF writeup for Pwn-200 (a simple overflow bug)

I know what you’re thinking of: what’s with all the Web levels!?

Well, I was saving the exploitation levels for last! This post will be about Pwnable-200 (ezhp), and the next one will be Pwnable-275 (kappa). You can get the binary for ezhp here, and I highly recommend poking at this if you’re interested in exploitation—it’s actually one of the easiest exploitation levels you’ll find!

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PlaidCTF writeup for Web-300 – whatscat (SQL Injection via DNS)

Hey folks,

This is my writeup for Whatscat, just about the easiest 300-point Web level I’ve ever solved! I wouldn’t normally do a writeup about a level like this, but much like the mtpox level I actually wrote the exact tool for exploiting this, and even wrote a blog post about it almost exactly 4 years ago - April of 2010. Unlike mtpox, this tool isn’t the least bit popular, but it sure made my life easy!

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PlaidCTF writeup for Web-200 – kpop (bad deserialization)

Hello again!

This is my second writeup from PlaidCTF this past weekend! It’s for the Web level called kpop, and is about how to shoot yourself in the foot by misusing serialization (download the files). There are at least three levels I either solved or worked on that involved serialization attacks (mtpox, reeekeeeeee, and this one), which is awesome because this is a seriously undersung attack. Good on the PPP!

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PlaidCTF writeup for Web-150 – mtpox (hash extension attack)

Hey folks,

This is going to be my first of a couple writeups about this past weekend’s CTF: PlaidCTF!

My first writeup is for a 150-point Web level called mtpox. I chose this one to do first not only because it’s the first level I completed, but also because the primary vulnerability was a hash extension issue, and I wrote one of most popular tools for exploiting those. So it’s like the level made for me!

(Actually, there’s another level that I wrote a less popular tool for. I’ll talk about that one in my next post. :) )

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Ghost in the Shellcode: fuzzy (Pwnage 301)

Hey folks,

It’s a little bit late coming, but this is my writeup for the Fuzzy level from the Ghost in the Shellcode 2014 CTF! I kept putting off writing this, to the point where it became hard to just sit down and do it. But I really wanted to finish before PlaidCTF 2014, which is this weekend so here we are! You can see my other two writeups here (TI-1337) and here (gitsmsg).

Like my other writeups, this is a “pwnage” level, and required the user to own a remote server. Unfortunately, because of my slowness, they’re no longer running the server, but you can get a copy of the binary at my github page and run it yourself. It’s a 64-bit Linux ELF executable. It didn’t have ASLR, and DEP would have been

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Ghost in the Shellcode: gitsmsg (Pwnage 299)

“It’s Saturday night; I have no date, a 2L bottle of Shasta, and my all-rush mix tape. Let’s rock!”

…that’s what I said before I started gitsmsg. I then entered “Rush” into Pandora, and listened to a mix of Rush, Kansas, Queen, Billy Idol, and other 80’s rock for the entire level. True story.

Anyway, let’s get on with it! Not too long ago I posted my writeup for the 100-level “Pwnage” challenge from Ghost in the Shellcode. Now, it’s time to get a little more advanced and talk about the 299-level challenge: gitsmsg. Solved by only 11 teams, this was considerably more challenging.

As before, you can obtain the binary, my annotated IDA database, and exploit code on my Github page

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Ghost in the Shellcode: TI-1337 (Pwnable 100)

Hey everybody,

This past weekend was Shmoocon, and you know what that means—Ghost in the Shellcode!

Most years I go to Shmoocon, but this year I couldn’t attend, so I did the next best thing: competed in Ghost in the Shellcode! This year, our rag-tag band of misfits—that is, the team who purposely decided not to ever decide on a team name, mainly to avoid getting competitive—managed to get 20th place out of at least 300 scoring teams!

I personally solved three levels: TI-1337, gitsmsg, and fuzzy. This is the first of three writeups, for the easiest of the three: TI-1337—solved by 44 teams.

You can download the binary, as well as the exploit, the IDA Pro files, and everything else worth keeping that I generated, from my Github repository.

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ropasaurusrex: a primer on return-oriented programming

One of the worst feelings when playing a capture-the-flag challenge is the hindsight problem. You spend a few hours on a level—nothing like the amount of time I spent on cnot, not by a fraction—and realize that it was actually pretty easy. But also a brainfuck. That’s what ROP’s all about, after all!

Anyway, even though I spent a lot of time working on the wrong solution (specifically, I didn’t think to bypass ASLR for quite awhile), the process we took of completing the level first without, then with ASLR, is actually a good way to show it, so I’ll take the same route on this post.

Before I say anything else, I have to thank HikingPete for being my wingman on this one. Thanks to him, we solved this puzzle much more quickly and, for a short time, were in 3rd place worldwide!

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Epic “cnot” Writeup (highest value level from PlaidCTF)

When I was at Shmoocon, I saw a talk about how to write an effective capture-the-flag contest. One of their suggestions was to have a tar-pit challenge that would waste all the time of the best player, by giving him a complicated challenge he won’t be able to resist. In my opinion, in PlaidCTF, I suspected that “cnot” was that challenge. And I was the sucker, even though I knew it all the way…

(It turns out, after reviewing writeups of other challenges, that most of the challenges were like this; even so, I’m proud to have been sucked in!)

If you want a writeup where you can learn something, I plan to post a writeup for “Ropasaurus” in the next day or two. If you want a writeup about me being tortured as I fought through inconceivable horrors to finish a level and capture the bloody flag, read on! This level wasn’t a lot of learning, just brute-force persistence.

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A padding oracle example

Early last week, I posted a blog about padding oracle attacks. I explained them in detail, as simply as I could (without making diagrams, I suck at diagrams). I asked on Reddit about how I could make it easier to understand, and JoseJimeniz suggested working through an example. I thought that was a neat idea, and working through a padding oracle attack by hand seems like a fun exercise!

(Having done it already and writing this introduction afterwards, I can assure you that it isn’t as fun as I thought it’d be :) )

I’m going to assume that you’ve read my previous blog all the way through, and jump right into things!

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Padding oracle attacks: in depth

This post is about padding oracle vulnerabilities and the tool for attacking them - “Poracle” I’m officially releasing right now. You can grab the Poracle tool on Github!

At my previous job — Tenable Network Security — one of the first tasks I ever had was to write a vulnerability check for MS10-070 — a padding oracle vulnerability in ASP.net. It’s an interesting use of a padding oracle vulnerability, since it leads to code execution, but this blog is going to be a more general overview of padding oracles. When I needed to test this vuln, I couldn’t find a good writeup on how they work. The descriptions I did find were very technical and academic, which I’m no good at. In fact, when it comes to reading academic papers, I’m clueless and easily frightened. But, I struggled through them, and now I’m gonna give you a writeup that even I’d be able to understand!

By the way, the Wikipedia page for this attack isn’t very good. If somebody wants to summarize my blog and make it into a Wikipedia page, there’s now a source you can reference. :)

On a related note, I’m gonna be speaking at Shmoocon in February: “Crypto: You’re doing it wrong”. Among other things, I plan to talk about padding oracles and hash extension attacks — I’m really getting into this crypto thing!

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Everything you need to know about hash length extension attacks

You can grab the hash_extender tool on Github!

(Administrative note: I'm no longer at Tenable! I left on good terms, and now I'm a consultant at Leviathan Security Group. Feel free to contact me if you need more information!)

Awhile back, my friend @mogigoma and I were doing a capture-the-flag contest at https://stripe-ctf.com. One of the levels of the contest required us to perform a hash length extension attack. I had never even heard of the attack at the time, and after some reading I realized that not only is it a super cool (and conceptually easy!) attack to perform, there is also a total lack of good tools for performing said attack! After hours of adding the wrong number of null bytes or incorrectly adding length values, I vowed to write a tool to make this easy for myself and anybody else who's trying to do it. So, after a couple weeks of work, here it is!

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Using “Git Clone” to get Pwn3D

Hey everybody!

While I was doing a pentest last month, I discovered an attack I didn’t previously know, and I thought I’d share it. This may be a Christopher Columbus moment - discovering something that millions of people already knew about - but I found it pretty cool so now you get to hear about it!

One of the first things I do when I’m looking at a Web app - and it’s okay to make a lot of noise - is run the http-enum.nse Nmap script. This script uses the http-fingerprints.lua file to find any common folders on a system (basically brute-force browsing). I’m used to seeing admin folders, tmp folders, and all kinds of other interesting stuff, but one folder in particular caught my eye this time - /.git.

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Remote control manager FAIL

Hey guys,

Today, I thought it’d be fun to take a good look at a serious flaw in some computer-management software. Basically, the software is designed for remotely controlling systems on networks (for installing updates or whatever). As far as I know, this vulnerability is currently unpatched; there are allegedly mitigations, but you have to pay to see them! (A note to vendors - making us pay for your patches or mitigation notes only makes your customers less secure. Please stop doing that!)

This research was done in the course of my work at Tenable Network Security on the Reverse Engineering team. It’s an awesome team to work on, and we’re always hiring (for this team and others)! If you’re interested and you have mad reverse engineering skillz, or any kind of infosec skillz, get in touch with me privately! (rbowes-at-tenable-dot-com if you’re interested in applying)

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A deeper look at ms11-058

Hey everybody,

Two weeks ago today, Microsoft released a bunch of bulletins for Patch Tuesday. One of them - ms11-058 - was rated critical and potentially exploitable. However, according to Microsoft, this is a simple integer overflow, leading to a huge memcpy leading to a DoS and nothing more. I disagree.

Although I didn’t find a way to exploit this vulnerability, there’s more to this vulnerability than meets the eye - it’s fairly complicated, and there are a number of places that I suspect an experienced exploit developer might find a way to take control.

In this post, I’m going to go over step by step how I reverse engineered this patch, figured out how this could be attacked, and why I don’t believe the vulnerability is as simple as the reports seem to indicate.

Oh, and before I forget, the Nessus Security Scanner from Tenable Network Security (my employer) has both remote and local checks for this vulnerability, so if you want to check your network go run Nessus now!

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(Mostly) good password resets

Hey everybody!

This is part 3 to my 2-part series on password reset attacks (Part 1 / Part 2). Overall, I got awesome feedback on the first two parts, but I got the same question over and over: what’s the RIGHT way to do this?

So, here’s the thing. I like to break stuff, but I generally leave the fixing to somebody else. It’s just safer that way, since I’m not really a developer or anything like that. Instead, I’m going to continue the trend of looking at others’ implementations by looking at three major opensource projects - Wordpress, SMF, and MediaWiki. Then, since all of these rely on PHP’s random number implementation to some extent, I’ll take a brief look at PHP.

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Hacking crappy password resets (part 2)

Hey,

In my last post, I showed how we could guess the output of a password-reset function with a million states. While doing research for that, I stumbled across some software that had a mere 16,000 states. I will show how to fully compromise this software package remotely using the password reset.

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Hacking crappy password resets (part 1)

Greetings, all!

This is part one of a two-part blog on password resets. For anybody who saw my talk (or watched the video) from Winnipeg Code Camp, some of this will be old news (but hopefully still interesting!)

For this first part, I’m going to take a closer look at some very common (and very flawed) code that I’ve seen in on a major “snippit” site and contained in at least 5-6 different applications (out of 20 or so that I reviewed). The second blog will focus on a single application that does something much worse.

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Ethics of password cracking/dissemination

It’s rare these days for me to write blogs that I have to put a lot of thought into. Most of my writing is technical, which comes pretty naturally, but I haven’t written an argument since I minored in philosophy. So, if my old Ethics or Philosophy profs are reading this, I’m sorry!

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Watch out for exim!

Hey everybody,

Most of you have probably heard of the exim vulnerability this week. It has potential to be a nasty one, and my brain is stuffed with its inner workings right now so I want to post before I explode!

First off, if you’re concerned that you might have vulnerable hosts, I wrote a plugin for Nessus to help you find them (I’m not sure if it’s in the ProfessionalFeed yet - if it isn’t, it will be soon). There’s no Nmap script yet, but my sources tell me that it’s in progress (keep an eye on my Twitter account for updates on that).

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Faking demos for fun and profit

This week Last week Earlier this month Last month

Last year (if this intro doesn’t work, I give up trying to post this :) ), I presented at B-Sides Ottawa, which was put on by Andrew Hay and others (and sorry I waited so long before posting this… I kept revising it and not publishing). I got to give a well received talk, meet a lot of great folks, see Ottawa for the first time, and learn that I am a good solid Security D-lister. w00t!

Before I talk about the fun part, where I completely faked out my demo, if you want the slides you can grab them here: http://svn.skullsecurity.org:81/ron/security/2010-11-bsides-ottawa/. You can find more info about the conference and people’s slides at the official site. And finally, here’s a picture of me trying to look casual.

B-sides conferences, for those of you who don’t know, are awesome little conferences that often (but not always) piggyback on other conferences. They are free (or cheap), run by volunteers, and have raw and technical talks. B-sides Ottawa was no exception, and I’m thrilled I had the chance to not only see it, but take part in it. I really hope to run our own B-sides Winnipeg next year!

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A call to arms! Web app fingerprints needed!

Hey all,

This is partly an overview of a new Nmap feature that I’m excited about, but is mostly a call to arms. I don’t have access to enterprise apps anymore, and I’m hoping you can all help me out by submitting fingerprints! Read on for more.

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Finding Mapped Drives with Meterpreter

This post written by Matt Gardenghi

This is going to be a series of short “how to” articles so that I have a resource when I forget how I did something. Your benefit from this post is incidental to my desire to have a resource I can reach when I’ve had a brain cloud.

When cracking into a computer via Metasploit, I often (OK, usually) install meterpreter.  It just makes life simpler.  Well, the other day, I was chatting with @jcran about my inability to get access to network drives on a Novell network.  The problem is that Novell maps drives in a sorta funny method compared to Active Directory. At least that was my thought.  The problem generally is that Novell handles things extremely differently then AD, that I assumed that things would be different.  #facepalm

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Return of the Facebook Snatchers

First and foremost: if you want to cut to the chase, just download the torrent. If you want the full story, please read on….

Background

Way back when I worked at Symantec, my friend Nick wrote a blog that caused a little bit of trouble for us: Attack of the Facebook Snatchers. I was blog editor at the time, and I went through the usual sign off process and, eventually, published it. Facebook was none too happy, but we fought for it and, in the end, we got to leave the blog up in its original form.

Why do I bring this up? Well last week @FSLabsAdvisor wrote an interesting Tweet: it turns out, by heading to https://www.facebook.com/directory, you can get a list of every searchable user on all of Facebook!

My first idea was simple: spider the lists, generate first-initial-last-name (and similar) lists, then hand them over to @Ithilgore to use in Nmap’s awesome new bruteforce tool he’s working on, Ncrack.

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Information Security For College Students

I’ve thought about this off and on over the last few years.  Today I noticed that Kees Leune (http://www.leune.org/blog/kees/2010/07/teaching-agai.html) is going to be teaching a class this school year.  He was asking for comments and so here’s mine….

I’d like to see a threefold class system.  The first class would entail an overview of the 10 Domains.  The second would be Offensive Security and the third would be Defensive Security.

There is a reason for that ordering.  Without a good understanding of the fundamentals of security (10 domains) the second two classes will have less value.  Understanding the idea of physical security as well as separation of duties and such really support defensive and offensive security.  Defenders are better when they understand the threats.  Therefore, I place Offensive Security before Defensive Security.  But that’s preference.  You could teach them together and make it a two-part class (firewall defense/offense; Linux offense/defense and so forth).

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Five Relays and a Patch

Hey all,

We hired a new pair of co-op students recently. They’re both in their last academic terms, and are looking for a good challenge and to learn a lot. So, for a challenge, I set up a scenario that forced them to use a series of netcat relays to compromise a target host and bring a meterpreter session back. Here is what the network looked like: To describe in text:

  • They have already compromised a Web server with a non-root account
  • The Web server has no egress filtering, but full ingress filtering, and they aren’t allowed to install anything (fortunately, it already had Netcat)
  • The target server has both egress and ingress filtering, and is not accessible at all from the Internet, but the Web server can connect to it on 139/445 (which are vulnerable to ms08-067). The target can also connect back to the Web server on any port.

The challenge was to exploit the target server with ms08-067 and bring a meterpreter session back to the attacker server.

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Defeating expensive lockdowns with cheap shellscripts

Recently, I was given the opportunity to work with an embedded Linux OS that was locked down to prevent unauthorized access. I was able to obtain a shell fairly quickly, but then I ran into a number of security mechanisms. Fortunately, I found creative ways to overcome each of them.

Here’s the list of the biggest problems I encountered, in the order that I overcame them:

  • The user account couldn't 'ls' most folders due to lack of privileges
  • Process management tools (like ps) didn't work (thanks to the missing 'ls')
  • The user account could only write to designated areas, in spite of file permissions
  • Architecture was PowerPC, which I have no experience with
  • netstat, ifconfig, arp, and other tools were disabled
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Metasploit Express Beta – First Look

This post was written by Matt Gardenghi

This is just initial impressions of a beta product.

I’ve been playing with this for about a week now in an internal network.  I have a dedicated box running Ubuntu 10.04 and Metasploit Express.  I’ve noticed that Express loves CPU time but is much less caring about RAM.  It’s also not multi-threaded.  I’d recommend a dual core box as Express will peg one core.  If you want to do anything else while Express is running, you need two cores. Still, Express does not require an expensive RAM build out. I’ve run top plenty of times and seen that the RAM usage remains low even when I’ve had 170+ shells running.  :-p  Hopefully, we’ll get multi-threading down the road.  When multiple tasks are running simultaneously, this lack of multi-threading becomes an issue.  Everything slows to a crawl.

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Confidential Information in the Cloud

This is another special blog written by Matt Gardenghi!

My boss passed around a document about database security in the cloud.  It raised issues about proper monitoring of the DB, but offered no solutions.

This got me thinking.  I hate it when that happens.  Its like an automatic “boss button” that I can’t switch off.  /gah

For the sake of argument, let’s assume we are discussing VMs hosted on some provider’s (Amazon) VMWare ESX cluster.  This could really apply to any VM on any company’s specific VM host, but VMWare is big, popular, and a good basis to work from.  Let’s say, some marketing exec bought a package that would hold data on a machine in the cloud.  (You may shoot him later; right now, you have to deal with the issues of integration into your secure environment.)

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Stuffing Javascript into DNS names

Greetings!

Today seemed like a fun day to write about a really cool vector for cross-site scripting I found. In my testing, this attack is pretty specific and, in some ways, useless, but I strongly suspect that, with resources I don’t have access to, this can trigger stored cross-site scripting in some pretty nasty places. But I’ll get to that!

Interestingly enough, between the time that I wrote this blog/tool and published it, nCircle researchers have said almost the same thing (paper (pdf)). The major difference is, I released a tool to do it and demonstrate actual examples.

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Exotic XSS: The HTML Image Tag

There are the usual XSS tests.  And then there are the fun ones.  This is a story about a more exotic approach to testing XSS….

I was testing a company that had passed all XSS tests from their pentester.  I found that they allowed users to write HTML tags.  Of course they didn’t permit <script> tags or <iframe> tags.  (Well, they did allow those, but that was an oops - no server side filtering.)  This company had whitelisted a variety of “safe” tags for use by clients.

That’s boring, right?  Heh, thanks to Ron, I had a way to abuse their whitelist.  (I’ve since found this in Web Application Hackers Handbook, but I seem to have overlooked it at the time I read it.)  Three HTML 4 tags in particular allow javascript to be run from one of the elements and these are: <img>, <object>, and <style>.

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Are you a “Real” hacker or just a skiddie?

This is yet another guest post from our good friend Matt Gardenghi! If you enjoy this one, don’t forget to check his last one: Trusting the Browser (a ckeditor short story).

Often, I hear arguments that go like this: real hackers write code and exploits; everyone else is a script-kiddie.

That is a dumb argument from all sorts of levels.  For starters, those who make this observation are usually those who can write code.  Therefore, everyone who can’t meet their personal standards/abilities as a coder are “skiddies” who demean the profession.

I find it intriguing that everyone defines the basis for a good pentester by their own capabilities.  Clearly you think that you are good and it’s normal to think that everyone will want to be good just like you.  Consequently, they should all do as you do, right?  Wrong.  We need diversity of backgrounds, skills, and opinions.  It’s healthy not to inbreed (intellectually or otherwise).

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Weaponizing dnscat with shellcode and Metasploit

Hey all,

I’ve been letting other projects slip these last couple weeks because I was excited about converting dnscat into shellcode (or “weaponizing dnscat”, as I enjoy saying). Even though I got into the security field with reverse engineering and writing hacks for games, I have never written more than a couple lines of x86 at a time, nor have I ever written shellcode, so this was an awesome learning experience. Most people start by writing shellcode that spawns a local shell; I decided to start with shellcode that implements a dnscat client in under 1024 bytes (for both Linux and Windows). Like I always say, go big or go home!

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Trusting the Browser (a ckeditor short story)

My name is Matt Gardenghi. Ron seems to think it important that this post be clearly attributed to someone else (this fact might worry me). I’m an occasional contributor here (see: Bypassing AV). I handle security at Bob Jones University and also perform pentests on the side. (So if you need someone to do work, here’s my shameless plug.) I have acquired the oddly despised CISSP and the more respectable GCFA, GPEN, and GWAPT.

I know a company that purchased some Web 2.0 services.  We’ll leave it at that, to protect the guilty.  :-p

So, one day a bored user decided that the editor used on the site was annoying.  He used GreaseMonkey to replace the editor with his preferred editor.  This was “Clue #1” that a problem existed with the Web 2.0 service.

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How big is the ideal dick…tionary?

Hey all,

As some of you know, I’ve been working on collecting leaked passwords/other dictionaries. I spent some time this week updating my wiki’s password page. Check it out and let me know what I’m missing, and I’ll go ahead and mirror it.

I’ve had a couple new developments in my password list, though. Besides having an entirely new layout, I’ve added some really cool data!

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DNS Backdoors with dnscat

Hey all,

I’m really excited to announce the first release of a tool I’ve put a lot of hard work into: dnscat.

It’s being released, along with a bunch of other tools that I’ll be blogging about, as part of nbtool 0.04.

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Watch out for evil SMB servers: MS10-006

Thanks to a Google Alert on my name, I recently found Laurent Gaffié’s blog post about MS10-006 (Microsoft Technet link).

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Why settle for (stealing) one password?

This is just a quick thought I had at work today – actually, I had it in November, but just got around to posting it now. Common story, but eh?

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smb-psexec.nse: owning Windows, fast (Part 3)

Posts in this series (I’ll add links as they’re written):

  1. What does smb-psexec do?
  2. Sample configurations ("sample.lua")
  3. <a href=/blog/?p=404'>Default configuration ("default.lua")</a>
  4. Advanced configuration ("pwdump.lua" and "backdoor.lua")
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smb-psexec.nse: owning Windows, fast (Part 2)

Posts in this series (I’ll add links as they’re written):

  1. What does smb-psexec do?
  2. Sample configurations ("sample.lua")
  3. Default configuration ("default.lua")
  4. Advanced configuration ("pwdump.lua" and "backdoor.lua")
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smb-psexec.nse: owning Windows, fast (Part 1)

Posts in this series (I’ll add links as they’re written):

  1. What does smb-psexec do?
  2. Sample configurations ("sample.lua")
  3. Default configuration ("default.lua")
  4. Advanced configuration ("pwdump.lua" and "backdoor.lua")
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Pwning hotel guests

Greetings everybody!

I spent a good part of the past month traveling, which meant staying in several hotels, both planned and unplanned. There’s nothing like having a canceled flight and spending a boring night in San Francisco! But hey, why be bored when you have a packet sniffer installed? :)

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Toorcon coming up!

Hey all,

I’ll be presenting at Toorcon San Diego in a couple week (finalized lineup, my talk!).

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Nmap 5.00 released — lots of new features!

View my post on Slashdot

I’m just going to quote my Slashdot post inline.. check out the links for all the nitty gritty details. The bottom line is that 5.00 is awesome, and includes everything I’ve written as yet – download it! :)

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WebDAV Detection, Vulnerability Checking and Exploitation

Ahoy! My name is Andrew and I’ve been playing with the recent IIS WebDAV authentication bypass vulnerability (CVE-2009-1676) and helping Ron with writing the nmap detection script (http-iis-webdav-vuln.nse) and testing it in the lab. Ron is in a meeting today so I thought I’d jump in where he left off and post a bit about how to detect if WebDAV is enabled and how to actually exploit a folder once you’ve determined it is vulnerable.

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WebDAV Scanning with Nmap

Greetings!

This morning I heard (from the security-basics mailing list, of all places) that there’s a zero-day vulnerability going around for WebDAV on Windows 2003. I always like a good vulnerability early in the week, so I decided to write an Nmap script to find it!

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Bypassing AV over the Internet with Metasploit

I performed all of this to learn more about data exfiltration, remote control, etc… over a tightly controlled corp environment. It was depressing actually…. It’s far too easy to gain control of a corp network even one that is conscientious. This work is built on the info at metasploit.com.

Oh, let me just say thanks for Metasploit.  Words fail to describe how nice this project is.  Thanks guys.

So, I want to share what I’ve learned and offer some thoughts for pondering.

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Using PsTools in a pentest

I’m going to start off this blog by wishing a happy birthday to a very important person – me. :)

Now, onto the content!

PsTools is a suite of tools developed by Sysinternals (now Microsoft). They’re a great complement to any pen test, and many of my Nmap scripts are loosely based on them. As good as they are, they aren’t without their quirks!

Here are a few topics worth discussing:

  • Ports and traffic
  • Specifying an account
  • Running it purely in a console

Most (possibly all) of the PsTools use standard Windows functions. That makes life easy – we can expect PsTools to act the same way other remote functions work. If we know how!

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Bruteforcing Windows over SMB: Tips and Tricks

Today, I’m going to share some knowledge and techniques on bruteforcing Windows passwords. Hopefully, some of you have thought about this and can give me even more advice. If you know anything, post it!

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How Pwdump6 works, and how Nmap can do it

Today I want to discuss how the pwdump6 and fgdump tools work, in detail, and how I was able to integrate pwdump6 into my Nmap scripts. Is this integration useful? Maybe or maybe not, but it was definitely an interesting problem.

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More password dictionaries

Last month, I posted about some password dictionaries I’ve collected. Well, thanks to a hacker who compromised PHPBB’s site, I added another. There’s a big caveat to this one, though – these passwords are apparently based on ones that were cracked by the hacker, so they’re only an accurate representation of weak passwords.

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Password dictionaries

Greetings from 2009!

I have a real post planned for the near future, but for now you’re stuck with something short (and probably more useful, ultimately). I just wanted to draw attention to a few password databases I put on my wiki. You can find them here.

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ms08-068 — Preventing SMBRelay Attacks

Microsoft released ms08-068 this week, which fixes a vulnerability that’s been present and documented since 2001. I’m going to write a quick overview of it here, although you’ll probably get a better one by reading The Metasploit Blog.

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What time IS it?

How synced up are the clocks on your servers? Ignoring your system times may give an important clue to attackers. Read on to find out more!

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