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478 Posts By ben

  • Datasets!

    Here are a bunch of datasets accumulated over the years for different projects, have fun with them! If you have something to augment this list with, let me know.

    U.S. zip codes

    basic english words

    condensed english words

    english dictionnary

    miscellaneous easy to type

    star trek references

    first names

    significant numbers

    common passwords

    places

    king james bible words

    book of mormon words

    koran words

    U.S. counties

  • Trip to a new life

    Not a whole lot of cell coverage in Wyoming & Nebraska :)

  • Adding an Endace card to Symantec’s DLP

    I decided to publish this hack as I could not find an iota of information about getting an Endace card working With Symantec’s DLP (previously Vontu) on RedHat.

    After you’ve installed the module for your Endace card, you recycle your sensor and are confronted with the following error message:

    Endace DAG driver is not available
    Packet Capture was unable to activate Endace device support. Please see PacketCapture.log for more information.

    A look at /var/log/Vontu/debug/PacketCapture.log yields:

    ERROR PacketDriverFactory - Driver Dag is unavailable: libdag.so.3: cannot open shared object file: No such file or directory [PacketDriverFactory.cpp(423)]

    do an

    updatedb
    locate libdag.so

    You will notice you just compiled a version more recent than libdag.so.3. As it turns out, Symantec DLP v11.0 does NOT know how to use the generic libdag.so nor the latest libdag.so.4.0.2 you just compiled. I’ve tried many tricks mostly with symlinks and I just couldn’t get it to use libdag.so.4.

    Hold on to your pants as I explain the unholy hack that made it work:

    edit /opt/Vontu/Protect/lib/native/libPacketDriverDag.so.11.0.0 , this is a binary file so using a hex editor is a good idea although vi works fine. Also, do respect placement very carefully, you will be changing 1 character and 1 character only.

    search for libdag.so.3 and replace its 3 by a 4.

    Recycle your server again and it should be happy about life :)

  • Spamassassin stats

    54.46% of all emails received on akrin so far got flagged as spam by the excellent Spamassassin. This is actually not too bad compared to high profile mail service providers.

    1 email that takes the cake is with a spam score of 42.2 (anything above 4 is not relayed):

    Return-Path: <comicalbp@sosmoteurs.com>
    Received: from 201-93-229-84.dsl.telesp.net.br (201-93-229-84.dsl.telesp.net.br [201.93.229.84])
    From: "Chase bank" <mailserver.id3373332193ib@chase.com>
    To: <XXXXXX@akrin.com>
    Subject: urgent security notification for client!
    X-Spam-Level: ******************************************
    X-Spam-Status: Yes, score=42.2 required=5.0

    Content analysis details:

    pts rule name              description
    ---- ---------------------- --------------------------------------------------
    2.0 RCVD_IN_BL_SPAMCOP_NET RBL: Received via a relay in bl.spamcop.net [Blocked - see <http://www.spamcop.net/bl.shtml?201.93.229.84>]
    3.0 RCVD_IN_XBL            RBL: Received via a relay in Spamhaus XBL [201.93.229.84 listed in zen.spamhaus.org]
    0.9 RCVD_IN_PBL            RBL: Received via a relay in Spamhaus PBL
    0.6 RCVD_IN_SORBS_WEB      RBL: SORBS: sender is a abuseable web server [201.93.229.84 listed in dnsbl.sorbs.net]
    1.8 URIBL_PH_SURBL         Contains an URL listed in the PH SURBL blocklist [URIs: nilvert.com]
    1.9 URIBL_AB_SURBL         Contains an URL listed in the AB SURBL blocklist [URIs: nilvert.com]
    1.5 URIBL_WS_SURBL         Contains an URL listed in the WS SURBL blocklist [URIs: nilvert.com]
    1.5 URIBL_JP_SURBL         Contains an URL listed in the JP SURBL blocklist [URIs: nilvert.com]
    2.0 URIBL_BLACK            Contains an URL listed in the URIBL blacklist [URIs: nilvert.com]
    3.5 BAYES_99               BODY: Bayesian spam probability is 99 to 100% [score: 1.0000]
    4.3 HELO_DYNAMIC_HCC       Relay HELO'd using suspicious hostname (HCC)
    4.4 HELO_DYNAMIC_IPADDR2   Relay HELO'd using suspicious hostname (IP addr 2)
    0.0 FH_HELO_EQ_D_D_D_D     Helo is d-d-d-d
    1.4 FROM_LOCAL_HEX         From: localpart has long hexadecimal sequence
    1.9 TVD_RCVD_IP            TVD_RCVD_IP
    2.8 TVD_PH_SUBJ_URGENT     TVD_PH_SUBJ_URGENT
    0.7 SPF_NEUTRAL            SPF: sender does not match SPF record (neutral)
    2.3 SPOOF_COM2COM          URI: URI contains ".com" in middle and end
    1.6 HTML_IMAGE_ONLY_24     BODY: HTML: images with 2000-2400 bytes of words
    0.0 HTML_MESSAGE           BODY: HTML included in message
    1.4 MIME_QP_LONG_LINE      RAW: Quoted-printable line longer than 76 chars
    0.1 RDNS_DYNAMIC           Delivered to trusted network by host with dynamic-looking rDNS
    2.8 DOS_OE_TO_MX           Delivered direct to MX with OE headers
  • Mounting a partition from a disk image

    So you’ve dded a disk and you would like to mount its partitions from the resulting image file. Easy enough, first:

    fdisk -l -u /path/to/disk.img

    Which will yield a variation of the following output:

    You must set cylinders.
    You can do this from the extra functions menu.
    
    Disk disk.img: 0 MB, 0 bytes
    255 heads, 63 sectors/track, 0 cylinders, total 0 sectors
    Units = sectors of 1 * 512 = 512 bytes
    Sector size (logical/physical): 512 bytes / 512 bytes
    I/O size (minimum/optimal): 512 bytes / 512 bytes
    Disk identifier: 0x00000080
    
       Device Boot      Start         End      Blocks   Id  System
    disk.img1              63    15631244     7815591   82  Linux swap / Solaris
    disk.img2   *    15631245   113290379    48829567+  83  Linux
    Partition 2 has different physical/logical endings:
         phys=(1023, 254, 63) logical=(7051, 254, 63)
    disk.img3       113290380   210949514    48829567+  83  Linux
    Partition 3 has different physical/logical beginnings (non-Linux?):
         phys=(1023, 254, 63) logical=(7052, 0, 1)
    Partition 3 has different physical/logical endings:
         phys=(1023, 254, 63) logical=(13130, 254, 63)

    Partitions available on the disk image are listed as disk.img1, disk.img2 & disk.img3. Great, pick which one you want to mount and look at where it starts.
    disk.img2 starts at 15631245, multiply that by 512. 15631245 * 512 = 8003197440.
    Finally, mount the disk image at the offset you calculated as such:

    mount -o loop,offset=8003197440 -t auto /path/to/disk.img /mnt/disk_img_partition2

    And done!

  • 2-factor authentication & writing PAM modules for Ubuntu

    Download

    2ndfactor.c

    The problem

    Passwords are often seen as a weak link in the security of today’s I.T. infrastructures. And justifiably so:

    • re-usability, which we’re all guilty of, guarantees that credentials compromised on a system can be leveraged on many others. And given the world we live in, password re-use is inevitable, we just have too many accounts in too many places.
    • plain text protocols are still used to transmit credentials, and the result is that they are exposed to network sniffing. This is worsened by the increase in wireless usage which broadcasts information. Telnet, FTP, HTTP come to mind but they aren’t the only ones.
    • lack of encryption on storage is a flaw that too often makes it way into architecture design. How many databases have we heard about getting hacked & dumped? How many have we not heard about?
    • password simplicity & patterns are also factors weakening us against bruteforce attacks.

    So far, the main counter measure we’ve see out there is complexity enforcement. Sometimes IP restriction, or triggering warnings on geographic inconsistencies (Gmail, Facebook). But these barely help alleviate problem.

    A solution

    One hot solution that is making its way into critical systems (banks, sensitive servers) is Multi-factor authentication, and by “multi” we’ll stick to 2-factor authentication (2FA) because, well 3 factor authentication might be getting a little cumbersome :). The goal is to have more than one mean of establishing identity. And as much as possible, the means have to be distinct in order to reduce the chances of having both mechanisms compromised.

    Let’s see how to implement 2FA on an Ubuntu server for SSH. Ubuntu uses PAM (Pluggable Authentication Modules) for SSH authentication among other things. PAM’s name speaks for itself, it’s comprised of many modules that can be added or removed as necessary. And it is pretty easy to write your own module and add it to SSH authentication. After PAM is done with the regular password authentication it already does for SSH, we’ll get it to send an email/SMS with a randomly generated code valid only for this authentication. The user will need access to email/cell phone on top of valid credentials to get in.

    Implementation

    Let’s do an ls on /lib/security, this is where the pam modules reside in Ubuntu.

    Let’s go ahead and create our custom module. First, be very careful, we’re messing with authentication and you risk locking yourself out. A good idea is to keep a couple of sessions open just in case. Go ahead and download the source for our new module.

    Take a look at the code, you’ll see that PAM expect things to be laid out in a certain way. That’s fine, all we care about is where to write our custom code. In our case it starts at line 35. As you can see, the module takes 2 parameters, a URL and the size of the code to generate. The URL will be called and passed a code & username. It is this web service that will be in charge of dispatching the code to the user. This step could be done in the module itself but here we have in mind a centrally managed service in charge of dispatching codes to multiple users.

    Deploying the code is done as follows:

    gcc -fPIC -lcurl -c 2ndfactor.c
    ld -lcurl -x --shared -o /lib/security/2ndfactor.so 2ndfactor.o

    If you got errors, you probably need to first:

    apt-get update
    apt-get install build-essential libpam0g-dev libcurl4-openssl-dev

    Do an ls on /lib/security again and you should see our new module, yay!

    Now let’s edit /etc/pam.d/sshd, this is the file that describes which PAM modules take care of ssh authentication, account & session handling. But we only care about authentication here. The top of the file looks like:

    # PAM configuration for the Secure Shell service
    
    # Read environment variables from /etc/environment and
    # /etc/security/pam_env.conf.
    auth       required     pam_env.so # [1]
    # In Debian 4.0 (etch), locale-related environment variables were moved to
    # /etc/default/locale, so read that as well.
    auth       required     pam_env.so envfile=/etc/default/locale
    
    # Standard Un*x authentication.
    @include common-auth

    The common-auth is probably what takes care of the regular password prompt so we’ll add our module call after this line as such:

    auth       required     2ndfactor.so base_url=http://my.server.com/send_code.php code_size=5

    The line is pretty self descriptive: this is an authentication module that is required (not optional), here’s its name and the parameters to give it.

    send_code.php can be as simple as:

    <?php mail( "{$_GET['username']}@mail_server.com", "{$_GET['code']}" ) ; ?>

    Or a complex as you can make it for a managed, multi-user, multi-server environment.

    Lastly, edit /etc/ssd/sshd_config and change ChallengeResponseAuthentication to yes. Do a quick

    /etc/init.d/ssh restart

    for the change to take effect.

    That’s it! try and ssh in, the code will be dispatched and you will be prompted for it after the usual password. This was tested on Ubuntu 10.04 32b / Ubuntu 10.04.2 64b / Ubuntu 11.04 64b / Ubuntu 12.04 64b.

    A few disadvantages of this 2FA implementation worth mentioning
    • more steps required to get in
    • doesn’t support non TTY based applications
    • relying on external services (web service, message delivery), thus adding points of failure. Implementing a fail-safe is to be considered.
    • SSH handles key authentication on its own, meaning a successful key auth does not go through PAM and thus does not get a chance to do the 2nd factor. You might want to disable key authentication in sshd’s config.
  • Chicken cam

    As part of my CCTV installation at home, a cam is placed in the chicken coop. This has very little direct purpose although it is fun to watch chicken behaviors with no humans around. And I guess it is nice to check if we have eggs or if everything is all right.

    Really, this is an experiment towards what our future farm will be like. We’d like for people to be able to watch how their food is grown. Maybe even interact remotely with the animals.

    It’s a little slow due to my 3Mbps connection and the proxying but have fun with it:

    The chicken cam has been disabled as we get ready to move to a new state.

    A year a and half after our big jump, it has been re-enabled :)

  • And Minecraft for all

    With video games becoming ever more realistic, one game stands out and defies the pursuit of polygons: Minecraft. With the charm of old video games, big fat pixels and a very square geometry. It stands to remind us of a time when video games left room for imagination.

    This is a pig

    It has the charm of an old Ultima and sandbox spirit of Legos. Indeed, there is no purpose in the game other than just build random stuff. And to get the material needed to create, it will take some serious world exploration. The world generator is very well tuned and will leave you in awe of the majestic landscapes & mystical caves it comes up with.

    Can you feel the wind on your cheeks?

    As with Legos, the possibilities are endless ranging from basic fort construction to advanced engineering.


    A slight downside is in the choice of technology: Java. Which as always sucks the everliving crap out of all the resources your machine has, both on the client and the server. Which is ironic given the simplistic nature of the game, it should have a very low footprint on the system.

    I’m running a server on Akrin, feel free to ask for a whitelist if you feel like building cool things with cool people.

  • Markov chains based random text generation

    We’ve already seen how to use Markov chains to generate random words that are based on the essence of a previously analyzed corpus. Well the exact same algorithm can be applied to text. The base entities become words instead of letters. I make punctuation be part of the entities, this way, sentence flow becomes part of the extracted statistical essence.

    Feel free to send me ideas of cool corpora to analyze.

    You can play with it here:

  • Tripwiring your linux box

    Privilege escalation, trojan’ed SSH daemons, key loggers… While the focus is still mostly on MS platforms, Unix boxes aren’t free of exploits. As they are made popular by Macs and ever more approachable distributions like Ubuntu, they become more of a focus. The large share of the server market they represent is a considerable source of information that is mouth-watering to hackers.

    A good tool in the fight against ever evolving malware is Tripwire (the open source version cause we’re cheap). It takes the signature of key files on your systems (configuration, binaries) and checks them regularly for changes. Its major strength is the fact that no matter what exploit was used to compromise a certain binary, if this binary is infected, tripwire will go off. Modern antivirus softwares look for specific signatures of known infections, and there are so many of them that they only look for the ones that are thought to be in the wild at any given time. They also are in reactive mode against 0days and usually take a few days to adjust. Their behavioral analysis methods are based on heuristics and generate too many false positives to be worthwhile.

    Tripwire doesn’t care what the infection is, it just goes off if something changed. This is simple and efficient. Now it should only be one piece of a comprehensive security policy.

    In this article we’ll look at getting it installed and going on Ubuntu in a matter of minutes. You’ll want to be root for all this.

    ——————————————

    First, get the package:

    aptitude install tripwire

    It’ll ask you for the passphrases used to secure itself.

    You’ll end up with these config files in /etc/tripwire:

    ——————————————

    Edit /etc/tripwire/twpol.txt to define which areas to keep an eye on, a pretty ok default is provided but needs some tweaking for Ubuntu and personal preference. I’d publish mine but hey, that’d be pretty stupid. Just keep in mind that you can use an exclamation mark “!” to negate a line, let’s say you want it to look at /etc but not /etc/shadow (user will want to change passwords in most cases) you’ll have a rule that looks like that:

    {
    /etc        -> $(SEC_BIN) ;
    ! /etc/passwd ;
    }

    ——————————————

    When you’re done, run:

    twadmin --create-polfile -S /etc/tripwire/site.key /etc/tripwire/twpol.txt

    This will create the secured policy file based on the text file you just edited.

    ——————————————

    The config file (/etc/tripwire/twcfg.txt) can be edited too but the defaults are nice too. When done run:

    twadmin --create-cfgfile -S /etc/tripwire/site.key /etc/tripwire/twcfg.txt

    Again, this creates it secured equivalent.

    ——————————————

    Make sure that the created file are only readable/writable by root

    chmod 600 /etc/tripwire/tw.cfg /etc/tripwire/tw.pol

    Good practice dictates that you also should be removing plain text configuration files but you’ll want to keep them around for a little while, as you tweak your original config.

    ——————————————

    Finally, you can initialize the database with:

    tripwire --init

    What this does is take a snapshot of everything you’ve specified in the policy file. If any of it changes, you’ll be notified.

    ——————————————

    The following will run the check for changes manually.

    tripwire --check

    When you installed the package with aptitude, /etc/cron.daily/tripwire was automatically created to have this run everyday, root will received a mail report every day.

    ——————————————

    If you want to make a change to the base config:

    edit /etc/tripwire/twpol.txt
    twadmin --create-polfile -S /etc/tripwire/site.key /etc/tripwire/twpol.txt
    tripwire --init

    If you want to update the base config, for example to acknowledge changes that happened on the box:

    tripwire --update --twrfile /var/lib/tripwire/report/<hostname>-<date>-<hour>.twr