Monthly Archives: October 2009

Development

First month on my own

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Yeah, it’s already been a month since I took off and started working for Haxx full time. Starting a company (even though the company already existed in the legal sense) certainly involves a lot of paperwork and talking to banks, insurance companies and getting arrangements with partners etc. A lot of that of course being just an initial phase, but some of it will be a more integrated part of my day now when I don’t have a well-oiled team of admins hired that deal with such matters.

I’m happy to say that I have had a whole slew of good talks with existing and potentially new customers, and I’m already cooperating with a few companies in very constructive ways – so that I can help others succeed with their undertakings. Several things that happened during this month involved open source (although I’m not able to talk about them in public), and I feel really good when my work and my beliefs can go hand in hand!

This said, I’m always ready for more and new missions. If you’re in need, you know where I am!

Mail

Spammers now subscribe

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During several years I’ve been setting mailing lists I admin to only accept posts from subscribers iA can with spamn order to avoid having to deal with very large amounts of spam posts.

While that is slightly awkward to users of the list, the huge benefit for me as admin has been the deciding factor.

Recently however, I’ve noticed how this way to prevent spam on the mailing lists have started to fail more and more frequently.

Now, I see a rapid growth in spam from users who actually subscribe first and then post their spam to the list. Of course, sometimes spammers happen to just fake the from address from a member of a list – like when a spammer fakes my address and sends spam to a list I am subscribed to, but it’s quite obvious that we also see the actual original spammer join lists and send spam as well.

It makes me sad, since I figure the next step I then need to take on the mailing lists I admin is to either spam check the incoming mails with a tool like spamassassin (and risk false positives or to not trap all spams) and/or start setting new members as moderated so that I have to acknowledge their first post to the list in order to make sure they’re not spammers.

Or is there any other good idea of what I can do that I haven’t thought of?

Linux, Open Source, Security

null-prefix domino

dominosAt the end of July 2009, Scott Cantor contacted us in the curl project and pointed out a security flaw in libcurl (in code that was using OpenSSL to verify server certificates). Having read his explanation I recalled that I had witnessed the discussion on the NSS list about this problem just a few days earlier (which resulted in their August 1st security advisory). The problem is basically that the cert can at times contain a name with an embedded zero in the middle, while most source code assumes plain C-style strings that ends with a zero. This turns out to be exploitable, and is explained in great detail in this document (PDF).

I started to work on a patch, and in the mean time I talked to Simon Josefsson of the GnuTLS team to see if GnuTLS was fine or not, only to get him confirm that GnuTLS did indeed have the same problem.

So I contacted vendor-sec, and then on the morning of August 5 I thought I’d just make a quick check how the other HTTPS client implementations do their cert checks.

Wget: vulnerable

neon: vulnerable

serf: vulnerable

So, Internet Explorer and Firefox were vulnerable. NSS and GnuTLS were. (OpenSSL wasn’t, but then it doesn’t provide this verifying feature by itself) (lib)curl, wget, neon, serf were all vulnerable. If that isn’t a large amount of the existing HTTPS clients then what is? I also think that this shows that it would be good for all of us if OpenSSL had this functionality, as even if it had been vulnerable we could’ve fixed a busload of different applications by repairing a single library. Now we instead need to hunt down all apps that use OpenSSL and that verify certificate names.

Quite clearly we (as implementers) have all had the same silly assumptions, and quite likely we’ve affected each other into doing these sloppy codes. SSL and certificates are over and over again getting hit by this kind of painful flaws and setbacks. Darn, getting things right really is very very hard…

(Disclaimer: I immediately notified the neon and serf projects but to my knowledge they have not yet released any fixed versions.)