Static in the Ether

I had an interesting question posed ot me today by Dominic who asked me to verify whether his all new Digital certificate was correctly being used for signing mail. Thunderbird sadly complained that the signature was invalid, which was unexpected, and that the issuer was unknown ( expected since it comes form a private hierarchy.)  The question then lead to where did the problem lie?

My gut feel was that it was the disclaimer being inserted by an intermediary gateway ( one has to love corpmail).  Setting about proving this was the hard part.  The first issue at hand wa to actually extract the certificates so I could play with the verification.  Cert Viewer Plus for Thunderbird made this part a dream. Creating a modified version of the signed message was a little bit more problematic.

Trusting the command line, I started hunting around for details on openssl support for SMIME, which it has.  OPenSSL needs a full CA path for being able to verify SMIME signed messages. One can optain this from various places ( such as exporting form your browser) but in a case like this where a private hierarchy was being used, its enough to just make used of a somewhat smaller subset contianing only the certificates used in this chain.  These can be extracted using Cert Viewer Plus. Alternately some command line magic can be used to extract the PKCS7 formatted embedded certificates out in standard PEM format., using the following command:

openssl smime -pk7out -in mail.txt | \
        openssl pkcs7 -print_certs > extract.crt

Now that we have a certificate chain we can attempt the verify. The extract.crt below can be either from the openssl method above or the Cert Viewer plus PEM dump.

openssl smime -CAfile extract.crt -verify -in mail.txt

Now e actually have a more usable error message. Although I really don’t know why I have such a deep distrust in GUI apps for actually telling me what is wrong.

Verification failure
88175:error:21071065:PKCS7 routines:PKCS7_signatureVerify:digest failure:/usr/src/secure/lib/libcrypto/../../../crypto/openssl/crypto/pkcs7/pk7_doit.c:808:
88175:error:21075069:PKCS7 routines:PKCS7_verify:signature failure:/usr/src/secure/lib/libcrypto/../../../crypto/openssl/crypto/pkcs7/pk7_smime.c:265:

As suspected the digest filed, which lead to a overall signature failure.  The next step was to see if removing the disclaimer worked.  Repeating on a slightly edited version of the the mail gave the following:

openssl smime -CAfile extract.crt -verify -in mail2.txt
...
mail contents deleted
...
Verification successful

So the original question posed was if the signature system was working correctly which it now was. The differences between the two mail files was checked using diff

diff -u mail.txt  mail2.txt
--- mail.txt         Mon Aug 25 18:06:33 2008
+++ mail2.txt      Mon Aug 25 18:08:10 2008
@@ -61,10 +61,6 @@
    South Africa

-Important Notice: This email is subject to important restrictions, qualifications
 and disclaimers ("the Disclaimer") ..that all was one very long line that made
 up the corporate disclaimer.....
-
-
-
 ------=_NextPart_000_0048_01C906C7.DB6FB700
 Content-Type: application/x-pkcs7-signature;
        name="smime.p7s"

From the above the only difference shown is that a mailgateway had added in a extra four lines of disclaimer and whitespace padding.  The question now evolves as to how to provide the now pretty much ubiquitious organisational disclaimer in outgoing mail in such a way that it doesnt trash any cryptographic operations in which the mail is involved.  Ive gone back over mails from a  couple of other people in corporate South Africa that I know , and the problem seems to be widespread.

The solution may be that the disclaimer as such is encapsulated as a separeate mime component, which is what interestingly one university here does ( although it insists on prepending its mime encapsulated HTML disclaimer, which makes for relaly ugly mail reading!)

With the comment spam continuing to pour in I caved in a and implemented captchas for comments.  While a solution using mathematical computation such as that offered by the match captcha plugin for wordpress, since the are only host defendant (rather than having to rely on some other 3rd-party service), this particular plugin was only certified to 2.3.1, and I could not get a working download.  I capitulated to the web 2.0 way and installed WP-recaptcha, which provides a nice wrapper around the recaptcha.net service.

Installation was simple, with registration required in order to obtain two APi keys for use with the service. What interesting about this solution is that rather than just mutating words, a two phrase system is sued. One of the phrases is a known word, and th eother is a word that is taken form a ocr scan of the NYT or Internet Archive, ans has not been correctly identified by the ocr software. Thus there is a bit of community mindedness involved as well, as these words are interpreted. More on the gory details can be found here.

What does interest me tho is that this will not offer any protection from ‘pingback’ spam whihc is being submitted via the xmlrpc interface, but should still at another layer to the security onion.

I probably should have posted this a while back but, its still worth noting that Raffael Marty’s Applied Security Visualization has been released, and includes a copy of the DAVIX CD as distributed at Defcon 16 (davix-1.0.1-defcon16.iso.gz - also obtainable from the homepage, includes a couple of packet traces as used in the Defcon workshop) , which includes a copy of InetVis as one of their four chosen visual analysis tools on the live CD.

For the impatient some instructions are available for getting started. Now to work out what else to order form amazon so that the 40USD specail shipment fee hurts a little less ( thanks to our totally criminal and incompetent post office in South Africa)

Failing that its time to wait till the local places get round to stocking it.

With the 16^th incarnation of Defcon having come and gone last week, a number of people have put together a nice list of the various tools released. The ZDnet’s Rob Fuller has done all the hard work of tracking down the various tools and their websites in his article -  entitled “ DEFCON 16: List of tools and stuff released
“seems to be the most definitive.  Another (updated) list is on Rob’s personal site in which he includes some other items like Packet-O-Matic, PE-Scambler andVMware Pen-Testing Framework, alng with a link to the ISO.

Of all the tools release its DAVIX, that makes me happiest, other than it being a relaly slick Compilation of VizSec tools, it also features InetVis, which is a part of the postgraduate research by one of my students (Jean-Pierre van Riel), which I previously posted about.

iKat is the other tool that tickles my fancy.

There are some interesting setf odf Defcon Photos floating around such as these by sits, who has also made available a zip of the of the Defcon 16 CD contents.An 732MB ISO  version is also available that at least has checksums.

I see some fun times ahead!

Why trying out FreeNAS yesterday I ran into the problem thats tripped me up in the past, Windows ships with basic CD writing functionality, but nothing for burning images.  Previously I’ve used CDRtools or Nero, but didnt have these handy.  I came across InfraRecord, which suites all my needs.  It provided simple authoring capabilities for both CD and DVD images, and is released under the GPLv2.

The screenshots provided show the functionality quite nicely. To round it off, its a tiny 3MB download, installing to just over 8MB.  The actual burning is handled by the well established CDRtools libraries, but the frontend makes it a much more pleasurable experience, than having to fiddle with command line arguments.

Some two and a half hours into the FF3.0 download campaign, and the toll is beginning to show.spreadfirefox.com seems to be refusing connections. While individual mirror sites seem up, it looks like the counts are going via some redirector script. getfirefox.com is however working fine.

The impact its having on mirrors seems to be quite intense. The following two images sow traffic stats from mirror.ac.za the mirror service run by TENET here in South Africa.

Update:

A Firefox 3.0 download counter is now available. 943806 currently averaging some 7000/minute. Some commentary on the outages, although they seem to have cleared.

Today is the official launch of the Firefox 3.0 Browser. the 24 Hour period form June 17th to June 18th will be a a record attempt in order to get into the Guinness book of Records, for the most software downloads in a day. The day apparently starts on Tuesday, June 17th after 10am PDT.

This Aside, I think the upgrade is well worth it , and I’ve been more than happy since Beta2 when I move my primary system over to running 3.0. The biggest improvements being rendering when switching between tabs ( and I usually have LOTS of tabs) and memory usage.

Tomorrow regular programming resumes ;)

DAVIX is the upcoming live CD for data analysis and visualization, which will be released at Blackhat/DEFCON in Las Vegas this summer, with another talk at VizSec 2008. From the VizSec.org announcement:

Jan Monsch and Raffael Marty and have prepared the second beta version of DAVIX. And are now seeking for beta testers that have the time to test DAVIX and answer the questionnaire that comes along with the beta version. All completely filled out questionnaires received by me until Monday 23 June 2008 18:00 UTC will enter a raffle for one autographed copy of Raffy’s upcoming book “Applied Security Visualization”.

If you want to participate in the beta test please contact: jan.monsch ät iplosion.com

What makes me quite happy is that they have included InetVis as one of their four chosen visual analysis tools on the live CD.

I’ve been paying with this since this morning and so far so good.

Having now migrated to Wordpress from my own very customised version of phpBloxsom, which ran the previous incarnation of this blog, Ive been left with the issue of dealing with all the sites pulling my RSS feeds. With the change of software has come a change of url for the location of the feeds.

Apache’s mod_rewrite seems to be the obvious candidate for making this as transparent as possible. In essence what needed to happen was incoming requests for:

"GET /blog/?flav=rss&category=Security HTTP/1.0" and
"GET /blog/?flav=rss HTTP/1.0" respectively need to be converted into:


http://lair.moria.org/blog/archives/category/security/feed

and

http://lair.moria.org/blog/feed respectively

This was achieved matching on the QUERY_STRING variable within apache. The real trick came trying to get the new URLS to appear clean. This proved to be more difficult than I expected. My initial rewrite rules resulted int he following:

"GET /blog/?flav=rss HTTP/1.0" 301 249 "
"GET /blog/feed/?flav=rss HTTP/1.0" 200 54274 ""

The agent was directed to the right url but it still looks ugly. Note the use of a HTTP/301 status code indicating permanently moved rather than a 302 which mod_redirect usually provides. The solution to the appending of the query string turned out to be to force my own null string onto the redirect. The Apache Wiki was where I finally found the right answer. so the way to remove a QUERY_STRING is to append a blank string “?” to the redirect .

The final setup in my .htaccess for Wordpress looks as follows:

RewriteCond %{QUERY_STRING} ^flav=rss$ [NC]
RewriteRule ^$ http://lair.moria.org/blog/feed? [R=301,L]
RewriteCond %{QUERY_STRING} ^flav=rss&(category)=Security$ [NC]
RewriteRule ^$ http://lair.moria.org/blog/archives/category/security/feed? [R=301,L]
RewriteCond %{QUERY_STRING} ^flav=atom$ [NC]
RewriteRule ^$ http://lair.moria.org/blog/feed/atom? [R=301,L]