Timezones + static blog generation

Dec 18, 2016 / 0 comments

So, it turns out when you move to static blog generation and do the generation on your laptop, which is usually in the timezone you’re currently physically located, it can cause URLs to change. Especially if you’re prone to blogging late at night, which can result in even just a shift to DST changing things. I’ve forced jekyll to UTC by adding timezone: 'UTC' to the config, and ensuring all the posts now have timezones for when they were written (a lot of the imported ones didn’t), so hopefully things should be stable from here on.

No longer a student. Again.

Dec 12, 2016 / 0 comments

99 Problems

(image courtesy of XKCD)

Last week I graduated with a Masters in Legal Science (now taught as an MLaw) from Queen’s University Belfast. I’m pleased to have achieved a Distinction, as well an award for Outstanding Achievement in the Dissertation (which was on the infringement of privacy by private organisations due to state mandated surveillance and retention laws - pretty topical given the unfortunate introduction of the Investigatory Powers Act 2016). However, as previously stated, I had made the decision that I was happier building things, and wanted to return to the world of technology. I talked to a bunch of interesting options, got to various stages in the hiring process with each of them, and happily accepted a role with Titan IC Systems which started at the beginning of September.

Titan have produced a hardware accelerated regular expression processor (hence the XKCD reference); the RXP in its FPGA variant (what I get to play with) can handle pattern matching against 40Gb/s of traffic. Which is kinda interesting, as it lends itself to a whole range of applications from network scanning to data mining to, well, anything where you want to sift through a large amount of data checking against a large number of rules. However it’s brand new technology for me to get up to speed with (plus getting back into a regular working pattern rather than academentia), and the combination of that and spending most of the summer post DebConf wrapping up the dissertation has meant I haven’t had as much time to devote other things as I’d have liked. However I’ve a few side projects at various stages of completion and will try to manage more regular updates.

Confirming all use of an SSH agent

Jul 3, 2016 / 0 comments

For a long time I’ve wanted an ssh-agent setup that would ask me before every use, so I could slightly more comfortably forward authentication over SSH without worrying that my session might get hijacked somewhere at the remote end (I often find myself wanting to pull authenticated git repos on remote hosts). I’m at DebConf this week, which is an ideal time to dig further into these things, so I did so today. As is often the case it turns out this is already possible, if you know how.

I began with a setup that was using GNOME Keyring to manage my SSH keys. This isn’t quite what I want (eventually I want to get to the point that I can sometimes forward a GPG agent to remote hosts for signing purposes as well), so I set about setting up gpg-agent. I used Chris’ excellent guide to GnuPG/SSH Agent setup as a starting point and ended up doing the following:

$ echo use-agent >> ~/.gnupg/options
$ echo enable-ssh-support >> ~/.gnupg/gpg-agent.conf
$ sudo sed -i.bak "s/^use-ssh-agent/# use-ssh-agent/" /etc/X11/Xsession.options
$ sudo rm /etc/xdg/autostart/gnome-keyring-ssh.desktop

The first 2 commands setup my local agent, and told it to do SSH agent foo. The next stopped X from firing up ssh-agent, and the final one prevents GNOME Keyring from being configured to be the SSH agent, without having to remove libpam-gnome-keyring as Chris did. After the above I logged out of and into X again, and could see ~/.gnupg/S.gpg-agent.ssh getting created and env | grep SSH showing SSH_AUTH_SOCK pointing to it (if GNOME Keyring is still handling things it ends up pointing to something like /run/user/1000/keyring/ssh).

[Update: Luca Capello emailed to point out this was a bad approach; there’s thankfully no need to do the last 2 commands that require root. #767341 removed the need to edit Xsession.options and you can prevent GNOME Keyring starting on a per user basis with:

(cat /etc/xdg/autostart/gnome-keyring-ssh.desktop ;
 echo 'X-GNOME-Autostart-enabled=false') > \
 ~/.config/autostart/gnome-keyring-ssh.desktop

]

After this it turned out all I need to do was ssh-add -c <ssh keyfile>. The -c says “confirm use” and results in the confirm flag being appended to the end of ~/.gnupg/sshcontrol (so if you’ve already done the ssh-add you can go and add the confirm if that’s the behaviour you’d like).

Simple when you know how, but I’ve had conversations with several people in the past who wanted the same thing and hadn’t figured out how, so hopefully this is helpful to others.

Hire me!

Jun 27, 2016 / 0 comments

It’s rare to be in a position to be able to publicly announce you’re looking for a new job, but as the opportunity is currently available to me I feel I should take advantage of it. That’s especially true given the fact I’ll be at DebConf 16 next week and hope to be able to talk to various people who might be hiring (and will, of course, be attending the job fair).

I’m coming to the end of my Masters in Legal Science and although it’s been fascinating I’ve made the decision that I want to return to the world of tech. I like building things too much it seems. There are various people I’ve already reached out to, and more that are on my list to contact, but I figure making it more widely known that I’m in the market can’t hurt with finding the right fit.

  • Availability: August 2016 onwards. I can wait for the right opportunity, but I’ve got a dissertation to write up so can’t start any sooner.
  • Location: Preferably Belfast, Northern Ireland. I know that’s a tricky one, but I’ve done my share of moving around for the moment (note I’ve no problem with having to do travel as part of my job). While I prefer an office environment I’m perfectly able to work from home, as long as it’s as part of a team that is tooled up for disperse workers - in my experience being the only remote person rarely works well. There’s a chance I could be persuaded to move to Dublin for the right role.
  • Type of role: I sit somewhere on the software developer/technical lead/architect spectrum. I expect to get my hands dirty (it’s the only way to learn a system properly), but equally if I’m not able to be involved in making high level technical decisions then I’ll find myself frustrated.
  • Technology preferences: Flexible. My background is backend systems programming (primarily C in the storage and networking spaces), but like most developers these days I’ve had exposure to a bunch of different things and enjoy the opportunity to learn new things.

I’m on LinkedIn and OpenHUB, which should give a bit more info on my previous experience and skill set. I know I’m light on details here, so feel free to email me to talk about what I might be able to specifically bring to your organisation.

Fixing missing text in Firefox

Jun 23, 2016 / 0 comments

Every now and again I get this problem where Firefox won’t render text correctly (on a Debian/stretch system). Most websites are fine, but the odd site just shows up with blanks where the text should be. Initially I thought it was NoScript, but turning that off didn’t help. Daniel Silverstone gave me a pointer today that the pages in question were using webfonts, and that provided enough information to dig deeper. The sites in question were using Cantarell, via:

src: local('Cantarell Regular'), local('Cantarell-Regular'), url(cantarell.woff2) format('woff2'), url(cantarell.woff) format('woff');

The Firefox web dev inspector didn’t show it trying to fetch the font remotely, so I removed the local() elements from the CSS. That fixed the page, letting me pinpoint the problem as a local font issue. I have fonts-cantarell installed so at first I tried to remove it, but that breaks gnome-core. So instead I did an fc-list | grep -i cant to ask fontconfig what it thought was happening. That gave:

/usr/share/fonts/opentype/cantarell/Cantarell-Regular.otf.dpkg-tmp: Cantarell:style=Regular
/usr/share/fonts/opentype/cantarell/Cantarell-Bold.otf.dpkg-tmp: Cantarell:style=Bold
/usr/share/fonts/opentype/cantarell/Cantarell-Bold.otf: Cantarell:style=Bold
/usr/share/fonts/opentype/cantarell/Cantarell-Oblique.otf: Cantarell:style=Oblique
/usr/share/fonts/opentype/cantarell/Cantarell-Regular.otf: Cantarell:style=Regular
/usr/share/fonts/opentype/cantarell/Cantarell-Bold-Oblique.otf: Cantarell:style=Bold-Oblique
/usr/share/fonts/opentype/cantarell/Cantarell-Oblique.otf.dpkg-tmp: Cantarell:style=Oblique
/usr/share/fonts/opentype/cantarell/Cantarell-BoldOblique.otf: Cantarell:style=BoldOblique

Hmmm. Those .dpkg-tmp files looked odd, and sure enough they didn’t actually exist. So I did a sudo fc-cache -f -v to force a rebuild of the font cache and restarted Firefox (it didn’t seem to work before doing so) and everything works fine now.

It seems that fc-cache must have been run at some point when dpkg had not yet completed installing an update to the fonts-cantarell package. That seems like a bug - fontconfig should probably ignore .dpkg* files, but equally I wouldn’t expect it to be run before dpkg had finished its unpacking stage fully.

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