Entries posted in June 2016

I should probably document the purple server I hacked together in Perl and mentioned in my last post. In short it allows you to centralise notifications. Send "alerts" to it, and when they are triggered they will be routed from that central location. There is only a primitive notifier included, which sends data to the console, but there are sample stubs for sending by email/pushover, and escalation.

In brief you create alerts by sending a JSON object via HTTP-POST. These objects contain a bunch of fields, but the two most important are:

• id
  • A human-name for the alert. e.g. "disk-space", "heartbeat", or "unread-mail".
• raise
  • When to raise the alert. e.g. "now", "+5m", "1466006086".

When an update is received any existing alert has its values updated, which makes heartbeat alerts trivial. Send a message with:

{ "id": "heartbeat",

 "raise": "+5m",
 .. }

The existing alert will be updated each time such a new event is submitted, which means that the time at which that alert will raise will be pushed back by five minutes. If you send this every 60 seconds then you'll get informed of an outage five minutes after your server explodes (because the "+5m" will have been turned into an absolute time, and that time will eventually become in the past - triggering a notification).

Alerts are keyed on the source IP which sent the submission and the id field, meaning you can send the same update from multiple hosts without causing any problems.

Notifications can be viewed in a reasonably pretty Web UI, so you can clear raised-alerts, see the pending ones, and suppress further notifications on something that has been raised. (By default notifications are issued every sixty seconds, until the alert is cleared. There is support for only raising an alert once, which is useful for services you might deliver events via, such as pushover which will repeat themselves.)

Anyway this is a fun project, which is a significantly simplified and less scalable version of a project which is open-sourced already and used at Bytemark.

Tags: purple | 4 comments

The past few days I've been working on my mail client which has resulted in a lot of improvements to drawing, display and correctness.

Since then I've been working on adding GPG-support. My naive attempt was to extract the signature, and the appropriate body-part from the message. Write them both to disk then I could validate via:

gpg --verify msg.sig msg

However that failed, and it took me a long to work out why. I downloaded the source to mutt, which can correctly verify an attached-signature, then hacked lib.c to neuter the mutt_unlink function. That left me with a bunch of files inside $TEMPFILE one of which provided the epiphany.

A message which is to be validated is indeed written out to disk, just as I would have done, as is the signature. Ignoring the signature the message is interesting:

Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: quoted-printable

On Mon, 27 Jun 2016 08:08:14 +0200

...

--=20
Bob Smith

The reason I'd failed to validate my message-body was because I'd already decoded the text of the MIME-part, and I'd also lost the prefixed two lines "Content-type:.." and Content-Transfer:.... I'm currently trying to work out if it is possible to get access to the RAW MIME-part-text in GMIME.

Anyway that learning aside I've made a sleazy hack which just shells out to mimegpg, and this allows me to validate GPG signatures! That's not the solution I'd prefer, but that said it does work, and it works with inline-signed messages as well as messages with application/pgp-signature MIME-parts.

Changing the subject now. I wonder how many people read to the end anyway?

I've been in Finland for almost a year now. Recently I was looking over websites and I saw that the domain steve.fi was going to expire in a few weeks. So I started obsessively watching it. Today I claimed it.

So I'll be slowly moving things from beneath steve.org.uk to use the new home steve.fi.

I also setup a mini-portfolio/reference site at http://steve.kemp.fi/ - which was a domain I registered while I was unsure if I could get steve.fi.

Finally now is a good time to share more interesting news:

• I've been reinstated as a Debian developer.
• We're having a baby.
  • Interesting times.

Tags: finland, gpg, lumail, mutt, updates | 7 comments