Category Archives: Open Source

Open Source, Free Software, and similar

libssh2, Open Source, Security

Slacka-fun!

A bunch of the local OpenBSD fans here in Stockholm run this one-day event every year, called Slackathon. I missed it last year, but in 2007 I was there (and I did a little talk about open source management) and this year I was eager to participate again.

This year, the event was scheduled to take place immediately after a bunch of core OpenBSD developers had had their “hackathon f2k9” in Stockholm, so they could now boast with a series of very well known and very knowledgeable OpenBSD kernel hackers. As I am really not more than a distant observer of the OpenBSD project this of course put the lights on a lot of dusty corners I had no previous idea about. I’m not really a stranger to kernels and kernel hacking in general, and I must confess I had a great time and the team who spoke of various very detailed kernel topics are charismatic and put on a great show.

So I learned about the terrors of the VFS layer and hacking it (and how they’re working on making all the involved caches dynamically sized). I learned how to do active-active syncing  of pf-based firewalls (basically using two independent firewalls in front of something), or at least how the guys made it work fairly well. Or how the pf firewall was optimized to double its forwarding performance. And I got to hear a few wise words from Theo de Raadt and learn not only about their 6 month release schedules but also their plans and ideas around solving problems with livelocking and more. Not to mention the talk about managing physical memory, or the work to get OpenBSD ported to sparc64s with hardware-based virtualization support.

Taken all the hardcore kernel talks into account, I think my own talk on libssh2 (just before dinner) felt like a very light snack to chew and possibly a tiny bit out of the general topic… Anyway, I gave a quick overview of the project, how it started, why it was started, what it is and a bit how it works etc.

The slides from my slackathon talk. I expect to re-use a fair bunch of that, with some improvements and additions, in my libssh2 talk at FSCONS later this year.

Looking forward to Slackathon 2010!

Pictures from Slackathon 2009 by Vladimir Bogodist.

Me in front of the projector screen doing libssh2 talk

Open Source, Technology

Snaxx 21

HaxxYes!

It is now time to once again leave your dark and dusty corners of your office or closet, bring yourself up to speed on what currency we’re using in this country and then unite with fellow hackers and technologists in Stockholm City during a fine September evening. The entire Haxx team is delighted to inform that Snaxx-21 is about to happen…

Monday, September 28th 2009

Time: around 18:30

Where: see the snaxx site!

As usual we’re informal, and as our friends you’re of course allowed and encouraged to bring other friends who are similar in spirit and who you think would appreciate an event such as this.

When you’ve decided to show up, please email me and say so.

There might even be free t-shirts involved this time!

Oh, and if you are a Stockholmer and didn’t get this invite by mail already, let me know and I’ll add you to the list of people who get this notice by the old trusty RFC822 way.

cURL and libcurl, Security

curl fooled by null-prefix

We’ve just now released a security advisory on curl and libcurl regarding how a forger can trick libcurl to verify a forged site as having a fine certificate if you just had a CA create one for you with a carefully crafted embedded zero…

I think this flaw brings the light so greatly on the problems we deal with to maintain code to be safe and secure. When writing code, and as in this case using C, we might believe we’re mostly vulnerable to buffer overflows, pointer messups, memory leaks or similar. Then we see this fascinatingly imaginative “attack” creep up…

The theory in short and somewhat simplified:

A server certificate is always presented by a server when a client connects to it using SSL. The certificate contains the servers name. The client verifies that A) the cert is signed by the correct authority and B) that the cert has the correct name inside.

The A) thing works because servers buy their cert from a CA authority that has its public signature in all browsers, and thus we can be “cryptographically safe” when we see a match.

This last flaw was in the naming part (B). Apparently someone managed to trick a CA to hand out a cert to them using an embedded zero byte. Like if haxx.se would buy the cert, we’d get it with an embedded zero like:

“example.com\0.haxx.se”

Now, this works fine in certificates since they store the string and its length separately. In the language C we’re used to have strings that are terminated with a trailing zero… so, if we would take over the “example.com” HTTPS server we could put our legitimately purchased certificate on that server and clients would use strcmp() or the equivalent to check the name in the certificate against the host name they try to connect to.

The embedded zero makes strcmp(host, certname) return MATCH and the client was successfully fooled.

curl is no longer vulnerable to this trick since 7.19.6, and we have released a boatload of patches for older versions in case upgrading is not an option.

cURL and libcurl

curl 7.19.6 is here!

Yet again we strike back with an update to the popular download tool curl and the transfer library libcurl.

Noticeable changes this time include:

  • A security related fix, for the flaw named CVE-2009-2417.
  • CURLOPT_FTPPORT (and curl’s -P/–ftpport) support port ranges
  • Added CURLOPT_SSH_KNOWNHOSTS, CURLOPT_SSH_KEYFUNCTION, CURLOPT_SSH_KEYDATA so that both the library and the curl tool now understand and work with OpenSSH style known_hosts file (if built with libssh2 1.2 or later)
  • CURLOPT_QUOTE, CURLOPT_POSTQUOTE and  CURLOPT_PREQUOTE can be told to ignore error responses when used with FTP. Handy if you want to run custom commands that may fail, but still enjoy persistent connections properly.

Let me just mention that the known_host support will make the SCP and SFTP transfers done with curl one step more secure. My work on this feature (both in libssh2 and in libcurl) was sponsored by a well-known company that shall remain unidentified at their request.

cURL

cURL and libcurl, Open Source

libcurl in package management

A few days ago I noticed that the “urlgrabber” project now has switched to using pycurl (the python libcurl binding) in their bleeding edge development. It means that projects using that, such well-known apps like yum and anaconda then use libcurl. Already since ages the Suse installer named YaST is using libcurl and a few months ago I learned that the opensolaris package management (pkg) is also switching to become pycurl based.

According to the lead man on the urlgrabber project, Seth Vidal, there are several reasons to switch from Python’s native urllib for (mostly) HTTP transport and he was friendly enough to mention a few to me. Clearly the two primary reasons are FIPS certification and urllib’s lacking HTTP proxy support. The FIPS certification is something the Fedora project has been pushing for a lot during recent time and thus they’ve worked hard on making libcurl support NSS for SSL/TLS, and the lack of HTTP proxy support is supposedly hard to push into urllib itself due to its stagnant development etc.

In Debian-esque worlds, libcurl and curl are already used by the package system in forms of apt-transport-https and apt-file.

It seems that when you run an open source operating system tomorrow, chances are that libcurl is in the back-end of the package system.

Network, Open Source

A view of a popular post

1 Comment

So I post frequently on this blog, but I’m not a particularly interesting person myself, I’m not really a master at writing and phrasing articles to make them thrilling and irresistible and I basically only deal with really geeky and technical subjects. It means there’s an average of perhaps 200 views per day.

The other day I wrote my multipath tcp post, and someone submitted it to reddit. It turned out to become my most read posting on my blog ever. By far. I think the “views per day” graph looks pretty cool:

visitor graph from daniel.haxx.se/blog

libssh2, Web

I host www.libssh2.org

Sara Golemon, the founder and former maintainer of libssh2, pointed over the main site www.libssh2.org to my server the other day and now my previously unofficial libssh2 web site suddenly turned out to be the only and official one.

The plan is now to get the web contents push into a separate git repo to allow all libssh2’ers to modify it.

I’m also open and interested in feedback and ideas on how to improve the web site in whatever kind of way you think. Consider the current site mostly a placeholder for the info we have. How can we make it better?

libssh2

Development, Open Source, Technology, Web

My HTC Magic Review

This is my first “smartphone” I’ve owned myself so of course I have nothing else this fancy to actually compare against. I’ve played around with others’ a few times but that doesn’t really count. I’ve owned perhaps 8 mobile phones since I got my first one 1996, and they have all been Nokias and Sony Ericssons.

I was never really interested in iPhone due to many reasons. It is not open. It has a (very) restricted app distribution mechanism. It forbids apps from running simultaneously etc. And it has a pretty strong connection with itunes with no proper mass-storage syncing supported. But I admit that it has a slick UI and many cool apps.

My plan is to get some Android hacking going eventually and this is basically the first Android phone that has reached Swedish soil. I mean without requiring me to bend over backwards to get it, as I’m sure I could’ve bought previous Android phones from obroad if I really wanted to.

Random good things:

  • it’s fast, most things run faster than on my previous Sony Ericsson thing and yet this is way more advanced with much bigger screen estate and fancier UI
  • it has a nice gui that you mostly can guess how to work with
  • I love being able to use a qwerty-style keyboard when messaging instead of relying on T9 etc
  • wifi is fun, but with a decent data plan it basically only brings me slightly improved speed and I often can’t even tell the difference!
  • the integration with the Google services are nice, gmail and maps most noticeably
  • there really are a bunch of existing cool apps (I know iphone has lots more, but there are still thousands)
  • it has a much better approach to messaging, similar to what I’ve seen in the iphone, than I’ve ever experienced in a Nokia or Sony Ericsson. It focuses on conversations and keeps the “thread”.HTC Magic
  • I really really like the feeling of it being a networked thing that also can make phone calls. I can browse, use maps, use gmail just as easily as I can message or call people. With my previous phones all the internet-related services always felt tacked on like a very late afterthought.
  • The notification system is nice, and the three-screen wide “home” with its widget-system is really neat.

Bad stuff:

  • I’ve had some apps crash on me on occasion. But it’s rarely a problem as they’re restarted automatically for me.
  • Toggling wifi on/off a lot can sometimes lead to me not getting any data network at all, and I’ve had to reboot the phone to get back to phone-based (Edge/3G) data.

On-screen keyboard

Of course any and all geek friend I have ask me about how I deal with the on-screen keyboard. I must admit I’m still quite fond of it. Mostly because a physical keyboard makes the phone clonky and it adds physical contraints and wear-points that I don’t like. So the keyboard is a bit small, especially when the phone is in portrait mode, but the suggested completions are fine and I believe I’m already typing pretty quickly on the thing. When I ssh’ed from the phone to one of my servers I did find the obvious lack of cursor keys (to for example navigate an ordinary ncurses-based app or the command line history of a bash prompt) but other than that I really can’t complain.

Background Applications

One obvious advantage compared to iphones is of course the ability to run applications exactly the way I’d like. I can actually run the irc client and then have it in the background while I go browse the web or answer a call or whatever and then at my choice go back to the still connected irc client. In fact when playing with this it feels like a really ridiculous restriction of the iphone.

Comparing to my SE w550i

My previous phone is 94 grams compared to the Magic’s 116. The magic has a much bigger screen. The magic is roughly 11mm wider and 14mm taller. That makes it use 30% more volume (85 cm2) but still fits fine in the front pocket of any set of pants I use. The magic claims a lot longer battery life, but given that it has so much functionality I can’t help to play with all the time I doubt it’ll notice. It’ll more likely run down fast simply because I’ll use it more.

I’m also pleased that there’s no problem to just plug in the Magic to my Linux desktop and copy/sync the photos and the videos etc.

Google Integration

I realize some people will feel that the very tight integration with Google and Google’s services is a downside as it adds just another item that Google “owns” in your life. Still, it makes the experience very slick and as a user I get a lot of stuff “for free” as it just connects to lots of things that I already used and had accounts on. So gmail, sharing photos on picasaweb etc “just works”.