Stefano Rivera (tumbleweed)'s Website, Blog, collected bits of code, cruft and other stuff.

Spam Spam Spam Spam, Spam Spam Spam Spam, Lovely Spam, Wonderful Spam

This morning I got an unsolicited SMS spam “Home owners ? do u need money? R100,000 @ R752 pm! Reply YES and we?ll phone you”. I know that everybody gets things like this and they just shrug them off, but I have a rabid hatred of spammers.

With e-mail spam, there’s normally nothing you can do. The spammers are on the other side of the world, and they’ve used a botnet. But when I get something from South Africans, I act. We have the ECT act protecting us against spam. It’s not the most effective anti-spam legislation, but it’s better than nothing. I’ll send the IOZ Spam Message to the spammers, their ISP, the domain registrants etc etc. Usually I get a response. Usually they remove me from their lists. (If they don’t, their VP of marketing is going to have me harassing him over the phone in short order.) But of course they rarely mend their ways. Sometimes we end up in long e-mail arguments backwards and forwards, them saying “but I’m justified in spamming, because of foo”, me saying “no bloody way, because of bar” etc. It’s ineffectual and depressing, but at least I’m doing something to deter spammers and keep South Africa relatively clean.

But enough about e-mail. It’s time for some tips on dealing with SMS-spam. The SMS Spamming industry (euphemisms: direct marketing, wireless application service provider) is attempting to regulate itself rather than be regulated by government. They’ve formed WASPA and signed the sms code of practice. WASPA lets you file complaints against its members and fines them (although the fines are rather paltry).

I heard about them via Jeremy Thurgood’s recent spam-scapades. His spammers were charging R1 to opt-out. While the WASPA code of conduct allows a <=R1 fee, I agree with him that this is intolerable extortion.

In my case, my spammers had broken a few WASPA code of conduct rules:

  • 5.1.1.: They didn’t identify themselves in the SMS
  • 5.1.2.: There is no opt-out facility that I know of.
  • 5.1.4.: There is no advertised opt-out procedure.
  • 5.2.1.: I’m very careful about not allowing people to spam me, so I’m pretty sure they failed all the options. I’d like them to prove otherwise.

I looked up the originating number on the SMS Code website. It belongs to Celerity Systems. They are currently under a suspended sentence at WASPA, so my WASPA complaint should force them to fork out a fine. Lets hope for the best.

I’m against capital punishment, but I wouldn’t mind seeing a few spammers being hanged, drawn and quartered :-)

Bandwidth accounting with ulogd

My post about repositories wasn't just a little attempt to stave off work, it was part of a larger scheme.

I share the ADSL line in my digs with 3 other people. We do split-routing to save money, but we still have to divide the phone bill at the end of the month. Rather than buy a fixed cap, and have a fight over who's fault it was when we get capped, we are running a pay-per-use system (with local use free, subsidised by me). It means you don't have to restrain yourself for the common cap, but it also means I need to calculate who owes what.

For the first month, I used my old standby, bandwidthd. It uses pcap to count traffic, and gives you totals and graphs. For simplicity of logging, I gave each person a /28 for their machines and configured static DHCP leases. Then bandwidthd totalled up the internet use for each /28.

This was sub-optimal. bandwidthd either sees the local network, in which case it can't see which packets went out over which link. Or it can watch the international link, but then not know which user is responsible.

I could have installed some netflow utilities at this point, but I wanted to roll my own with the correct Linux approach (ulog) rather than any pcapping. ulogd is the easy ulog solution.

Ulogd can pick up packets that you "-j ULOG" from iptables. It receives them over a netlink interface. You can tell iptables how many bytes of each packet to send, and how many to queue up before sending them. E.g.

# iptables -I INPUT 1 -j ULOG --ulog-nlgroup 1 --ulog-qthreshold 50 --ulog-cprange 48 --ulog-prefix input

will log the first 48 bytes of any incoming packet to netlink-group 1. It will tag the packet as being "input", and send them in batches of 50. 48 bytes is usually enough to catch any data you could want from the headers. If you were only need size, 4 bytes will do, and for source and destination as well, 20.

Now, we tell ulogd to listen for this stuff and log it. Ulogd has a pluggable architecture. IPv4 decoding is a plugin, and there are various logging plugins for "-j LOG" emulation, Text files, pcap-files, MySQL, PostgreSQL, and SQLite. For my purposes, I used MySQL as the router in question already had MySQL on it (for Cacti). Otherwise, I would have opted for SQLite. Be warned that the etch version of ulogd doesn't automatically reconnect to the MySQL server should the connection break for any reason. I backported the lenny version to etch to get around that. (You also need to provide the reconnect and connect_timeout options.)

Besides the reconnection issue, the SQL implementations are quite nice. They have a set schema, and you just need to create a table with the columns in it that you are interested in. No other configuration (beyond connection details) is necessary.

My MySQL table:

My ulogd.conf:

# netlink multicast group (the same as the iptables --ulog-nlgroup param)
# logfile for status messages
# loglevel: debug(1), info(3), notice(5), error(7) or fatal(8)
# socket receive buffer size (should be at least the size of the
# in-kernel buffer (ipt_ULOG.o 'nlbufsiz' parameter)
# libipulog/ulogd receive buffer size, should be > rmem
# - interpreter plugin for basic IPv4 header fields
#             you will always need this


The relevant parts of my firewall rules:

# Count proxy usage (transparent and explicit)
iptables -A count-from-inside -p ! tcp -j RETURN
iptables -A count-from-inside -p tcp -m multiport --destination-ports ! 3128,8080 -j RETURN
iptables -A count-from-inside -s -j ULOG --ulog-nlgroup 1 --ulog-qthreshold 50 --ulog-cprange 4 --ulog-prefix sr-p
iptables -A count-from-inside -s -j ULOG --ulog-nlgroup 1 --ulog-qthreshold 50 --ulog-cprange 4 --ulog-prefix fb-p
iptables -A count-from-inside -s -j ULOG --ulog-nlgroup 1 --ulog-qthreshold 50 --ulog-cprange 4 --ulog-prefix gu-p

iptables -A count-to-inside -p ! tcp -j RETURN
iptables -A count-to-inside -p tcp -m multiport --source-ports ! 3128,8080 -j RETURN
iptables -A count-to-inside -d -j ULOG --ulog-nlgroup 1 --ulog-qthreshold 50 --ulog-cprange 4 --ulog-prefix sr-p
iptables -A count-to-inside -d -j ULOG --ulog-nlgroup 1 --ulog-qthreshold 50 --ulog-cprange 4 --ulog-prefix fb-p
iptables -A count-to-inside -d -j ULOG --ulog-nlgroup 1 --ulog-qthreshold 50 --ulog-cprange 4 --ulog-prefix gu-p

# Count forwarded traffic (excluding local internet connection - ppp2)
iptables -A count-forward-in -i ppp2 -j RETURN
iptables -A count-forward-in -d -j ULOG --ulog-nlgroup 1 --ulog-qthreshold 50 --ulog-cprange 4 --ulog-prefix sr-f
iptables -A count-forward-in -d -j ULOG --ulog-nlgroup 1 --ulog-qthreshold 50 --ulog-cprange 4 --ulog-prefix fb-f
iptables -A count-forward-in -d -j ULOG --ulog-nlgroup 1 --ulog-qthreshold 50 --ulog-cprange 4 --ulog-prefix gu-f

iptables -A count-forward-out -o ppp2 -j RETURN
iptables -A count-forward-out -s -j ULOG --ulog-nlgroup 1 --ulog-qthreshold 50 --ulog-cprange 4 --ulog-prefix sr-f
iptables -A count-forward-out -s -j ULOG --ulog-nlgroup 1 --ulog-qthreshold 50 --ulog-cprange 4 --ulog-prefix fb-f
iptables -A count-forward-out -s -j ULOG --ulog-nlgroup 1 --ulog-qthreshold 50 --ulog-cprange 4 --ulog-prefix gu-f

# Glue
iptables -A INPUT -i eth0 -j count-from-inside
iptables -A OUTPUT  -o eth0 -j count-to-inside
iptables -A FORWARD -i ppp+ -j count-forward-in
iptables -A FORWARD -o ppp+ -j count-forward-out

So, traffic for my /28 (sr) will be counted as sr-f or sr-p so I can tally up proxy & forwarded traffic separately. (Yes, I can count traffic with squid too, but doing it all in one place is simpler.) fb is random housemate Foo Bar, and gu guest (unreserved IP addresses).

You can query the usage this month with for example:

Your table will fill up fast. We are averaging around 200 000 rows per day. So obviously some aggregation is in order:

And every night, run something like:

Finally, I have a simple little PHP script that provides reporting and calculates dues. Done.

My first (real) debian repo

Up to now, whenever I've needed a backport or debian recompile, I've done it locally. But finally last night, instead of studying for this morning's exam, I decided to do it properly.

The tool for producing a debian archive tree is reprepro. There are a few howtos out there for it, but none of them quite covered everything I needed. So this is mine. But we'll get to that later, first we need to have some packages to put up.

For building packages, I decided to do it properly and use pbuilder. Just install it:

# aptitude install pbuilder cdebootstrap devscripts

Make the following changes to /etc/pbuilderrc:

DEBEMAIL="Your Name <>"

The first, to point to your local mirror, and the second to credit you in the packages.

Then, as root:

# pbuilder create --distribution etch --debootstrapopts --variant=buildd

Now, we can build a package, lets build the hello package:

$ mkdir /tmp/packaging; cd /tmp/packaging
$ gpg --recv-key 3EF23CD6
$ dget -x
dpkg-source: extracting hello in hello-2.2
dpkg-source: unpacking hello_2.2.orig.tar.gz
dpkg-source: applying ./hello_2.2-2.diff.gz
$ cd hello-2.2/
$ debchange -n

dget and debchange are neat little utilities from devscripts. You can configure them to know your name, e-mail address, etc. If you work with debian packages a lot, you'll get to know them well. Future versions of debchange support --bpo for backports, but we use -n which means new package. You should edit the version number in the top line to be a backport version, i.e.:

hello (2.2-2~bpo-sr.1) etch-backports; urgency=low

  * Rebuild for etch-backports.

 -- Your Name <>  Wed,  2 Apr 2008 22:24:30 +0100

Now, let's build it. We are only doing a backport, but if you were making any changes, you'd do them before the next stage, and list them in the changelog you just edited:

$ cd ..
$ dpkg-source -sa -b hello-2.2-2~bpo/
$ sudo pbuilder build hello_2.2-2~bpo-sr.1.dsc

Assuming no errors, the built package will be sitting in /var/cache/pbuilder/result/.

Now, for the repository:

$ mkdir ~/public_html/backports
$ cd ~/public_html/backports
$ mkdir conf
$ cat > conf/distributions << EOF
Origin: Your Name
Label: Your Name's Backports
Suite: stable-backports
Codename: etch-backports
Version: 4.0
Architectures: i386 all source
Components: main
Description: Your Name's repository of etch backports.
NotAutomatic: yes

This file defines your repository. The codename will be the distribution you list in your sources.list. The version should match it. The architectures are the architectures you are going to carry - "all" refers to non-architecture-specific packages, and source to source packages. I added amd64 to mine. SignWith is the ID of the GPG key you are going to use with this repo. I created a new DSA key for the job. NotAutomatic is a good setting for a backports repo, it means that packages won't be installed from here unless explicitly requested (via package=version or -d etch-backports).

Let's start by importing our source package:

$ cd /tmp/packaging
$ debsign -kABCDABCD hello_2.2-2~bpo-sr.1.dsc
$ cd ~/public_html/backports
$ reprepro -P optional -S devel --ask-passphrase -Vb . includedsc etch-backports /tmp/packaging/hello_2.2-2~bpo-sr.1.dsc

(There is currently a known bug in reprepro's command-line handling. -S and -P are swapped.)

Now, let's import our binary package:

$ reprepro --ask-passphrase -Vb . includedeb etch-backports /var/cache/pbuilder/result/hello_2.2-2~bpo-sr.1_i386.deb

Reprepro can be automated with it's processincoming command, but that's beyond the scope of this howto.

Test your new repository, add it to your /etc/apt/sources.list

deb etch-backports main
# aptitude update
# aptitude install hello=2.2-2~bpo-sr.1

Enjoy. My backports repository can be found here.

I'm a Google Reader convert

My blog hasn’t had much to say recently, but now that I’m feeling pressured by University assignments, I think it’s time to get back into one-post-per-day mode :-)

I remember once trying Google Reader, just after it launched, and very quickly deciding that I couldn’t stand it, and I’d stick to Liferea.

Recently, however, Liferea has been giving me trouble. It’s been incredibly unstable, and I’d often forgot to run a transparent proxy on my laptop when in restrictive environments, so it’d miss lots of posts and generally be un-happy. The instability I fixed by exporting an OPML list, wiping the configuration, and re-loading, but that was a ball-ache to do. While I was bitching about this, Vhata pushed me to try Google Reader again.

I was pleasantly surprised. It works well, and I didn’t find it oppressive. That doesn’t mean it’s perfect, I’d like to see the following things improved:

  • Duplicate post detection (i.e. planetified & origional posts, liferea does this)
  • Performance
  • Favicons (or something similar, to make it more clear where a post comes from)
  • On that note, maybe configurable colour borders for important feeds?
  • Automatic refreshing (i.e. “r”)
  • More viewable area
  • A key press for opening a post in a backgrounded new tab “v” changes your focus to the new tab, which is against the principles of tabbed browsing.

Some cool things it does that lifera doesn’t:

  • Clicking on a folder shows you the all the posts from the feeds in that folder
  • river of posts” view, which lets me get through my reading a lot faster
  • preloading images for posts that I haven’t got to yet (this contributes a fair whack to the reading speed, given the slow interwebs in ZA)
  • Shared items
  • Access from multiple machines (OX, X-forwarding worked, but this is neater)
  • Doesn’t crash (sorry lifrea…)

I’m converted. Google Reader really is good.

/me gets on with reading feeds…

*Camp Videos

I’ve (finally) finished encoding the ~6 hours of *camp video. They can be found on As usual, 3 qualities.

I’ve probably screwed up at least one of them, so if anyone spots a problem, please let me know soon, before I delete the source material.

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