Using Letsencrypt with Wowza Media Server

As part of a work project, I needed to set up Wowza Media Server to do video streaming. As the webapp (which I wrote using the excellent ionic 3 framework) is running under https, it won’t accept video traffic coming from non-encrypted sources. Wowza has some pricey solutions for automatically installing SSL certificates for you, you can also purchase ones however these days I don’t see why everyone doesn’t just use the free and easily automated letsencrypt system. Unfortunately however, letsencrypt doesn’t let you run servers on different ports particularly easily, although it does have some hooks to stop/start services that may already be listening on port 443 (ssl). I happen to be using a redhat/centos distro, although I’m pretty sure the exact same instructions will work on ubuntu and other distros.

Firstly, you need to download the wowza-letsencrypt-converter java program which will convert letsencrypt certificates to the Java format that Wowza can use. Install that prebuild jar under /usr/bin.

Now, create a directory under the Wowza conf directory called ssl and create a file called jksmap.txt (so for example full path is /usr/local/WowzaStreamingEngine/conf/ssl/jksmap.txt) which lists all the domains the Wowza server will be listening on like:

‘secret’ is not actually a placeholder; it’s the password that the wowza-letsencrypt-converter program sets up automatically so keep it as it is.

Configure SSL on the Wowza server by editing the VHost.xml configuration file (find out more about this process in the wowza documentation). Find the 443/SSL section which is commented out by default and change the following sections:

Note the <KeyStorePath>foo</KeyStorePath> line – the value foo is ignored when using jksmap.txt, however if this is empty the server refuses to start or crashes.

Next, install letsencrypt using the instructions on the certbot website.

Once you’ve done all this, run the following command to temporarily stop the server, fetch the certificate, convert it and start the server again:

Then, in order to ensure that the certificate continues to be valid you need to set up a cron entry to run this command daily which will automatically renew the cert when it gets close to its default 3 month expiry time. Simply create /etc/cron.d/wowza-cert-renewal with the following content:

Easily setup a secure FTP server with vsftpd and letsencrypt

I recently had to set up a FTP server for some designers to upload their work (unfortunately they couldn’t use SFTP otherwise it would have been much simpler!). I’ve not had to set up vsftpd for a while, and when I last did it I didn’t much worry about needing to use encryption. So here are some notes on how to set up vsftpd with letsencrypt on ubuntu 14.04 / 16.04 so that only a specific user or two are permitted access.

First, install vsftpd:

Next, you need to make sure you have installed letsencrypt. If not, you can do so using the instructions here – fortunately letsencrypt installation has got a lot easier since my last blog post about letsencrypt almost 2 years ago.

I’m assuming you are running this on the same server as the website, and you’re wanting to set it up as ftp on the same domain or similar subdomain as the website (eg ftp access direct to, or via something like If not, you can do a manual install of the certificate but then you will need to redo this every 3 months.

Assuming you’re running the site on apache get the certificate like:

You should now have the necessary certificates in the /etc/letsencrypt/live/ folder, and your site should be accessible nicely via https.

Now, create a user for FTP using the useradd command. If you want to just create a user that only has access to the server via FTP but not a regular account you can modify the PAM configuration file /etc/pam.d/vsftpd and comment out the following line:

This lets you keep nologin as the shell so the user cannot login normally but can log in via vsftpd’s PAM layer.

Now open up

Because we’re running behind a firewall we want to specify which port range to open up for the connections (as well as port 21 for FTP of course):

If you want to make it even more secure by only allowing users listed in /etc/vsftpd.userlist to be able to log in, add some usernames in that file and then add the following to the /etc/vsftpd.conf configuration file:

You can test using the excellent lftp command:

If the cert is giving errors or is self-signed, you can do the following to connect ignoring them:

Fixing Ubuntu 16.04 massive internal microphone distortion

A while ago I upgrade from Ubuntu 14.10 to 16.04. Afterwards, my laptop’s internal microphone started to become massively distorted to the point that people on the other end of skype or hangouts calls couldn’t understand me at all.

Looking in the ALSA settings I noticed that the “Internal Mic Boost” was constantly being set to 100% and when I dropped this down to 0% everything went well. It seems on my laptop at least to be coupled with the “Mic Boost” which boosts both but without quite so much distortion, ie the “Internal Mic Boost” is a boost on top of the “Mic Boost” which is obviously a problem.

I couldn’t find much detail about how to configure this properly, so after some hacking around I was able to come up with the following solution. Go through every file in /usr/share/pulseaudio/alsa-mixer/paths, look for the section “[Element Internal Mic Boost]” if it is there. You should see a setting under that section like “volume = merge“. Turn that into “volume = off“. To prevent it being changed later when ALSA is updated, you can run:

I’d love to hear if there is a simpler way to work around this issue, but it works for me at least!

Awesome Angular 4 form validator routine

One of the things I like the most about Angular is the ability to make even complex forms relatively simple. In Angular 1 I had a library of form helpers that I wrote, the basic idea was initially show a blank form, when user fills in (dirties) an entry it should do validation. When the user click on the submit button it should do validation of all items on the form, submit the form if no errors and show any errors if there were any. This sounds simple enough but in reality it was a few hundred lines of code to do it correctly.

Angular 2+ (Angular 4 on Ionic 3 in this case) make life a lot easier, especially once you’ve got to terms with the FormBuilder framework. To force whole-form validation (including any subforms) simply create a module called form-tools.ts looking like:

Then you can easily use it from another class as follows:

Fan/Light remote control teardown and documentation

I recently bought a few ceiling fan controllers from AliExpress, I’m guessing there are a lot more out there with a similar electrical design so I thought perhaps my notes on tearing these down would be useful for someone as I didn’t find this elsewhere on the internet. As I was taking them apart to replace the wireless section with an ESP8266 for WiFi remote control I thought I’d document the design of these devices a bit.

Firstly, the main circuits run at 12v – the relays are triggered by that voltage, and the remote control uses a small 12v battery too. However the radio is only rated for 5v, so I think there must be a 5v circuit there as well probably obtained via resistors from the 12v circuit. The basic block layout is that the radio receiver connects to an unmarked chip (in some models this connects to an AT24C02N which presumably holds the last state of the relays). The unmarked chip has 5 output tracks running from it to an ULN2003A which boosts the signal to 12v to trigger the relays. 4 tracks go to the 4 relays (one for the light, and 3 for fan control which has live, 3uF and 2.5uF (2uF in some models) capacitors to regulate the speed). The 5th track goes to a buzzer which is triggered when it gets powered on or receives a command from the remote controller. Unfortunately I can’t remember the order that fan relays were triggered as I wrote it down lost it, but it was something along the lines of:

high live
medium 3uF + 2.5uF
low 3uF

The radio receiver in the ceiling fan based on a SYN470R chip and the transmitter uses an EV1527 to encode the data to send to the fan. It sends 24-bits – a 20 bit id and a 4 bit code. Here are the hex codes for the commands as discovered by my patches to allow this device to work on a C.H.I.P board:




Command Hex code
low 8
medium 2
high 6
stop c
toggle light on/off 5
timer 1h 4
timer 2h
timer 4h
timer 8h

Uploading videos to YouTube with perl

As part of a perl project recently I needed to generate a load of videos (using the excellent MLT framework) and upload them to YouTube. As the bulk of the project was already in perl, I needed to write a YouTube upload module for it. Here’s a rough overview of how to authenticate and upload a video (chunked rather than loading it all into memory at once) with perl. Note as well it was quite a struggle to get long-term auth tokens from the Google services – one slight mistake with a parameter and they only give temporary grants which last for an hour or two rather than indefinitely.

As per this bug report you need to hack LWP::Authen::OAuth2::AccessToken::Bearer to enable the chunked uploads to work, otherwise it throws an error.

The auth_id and auth_secret parameters are given by the google code console when you sign up for YouTube API access, and the redirect_uri should be where the web app would redirect to after displaying the Google oauth permission grant screen. The first time you run the script, you’ll need to save the auth_code / auth_token parts and use them in future when calling. Even though it should grant a new auth token each time the script is run you still need to present the original one from the look of things.

Element scrolling within Angular (1) pages

Back to Angular 1 for today’s post as I’ve been doing some work on an older project today. As we all know, in the old days of the web, you could scroll to items within the page by using an <a> element with a hash reference, like:

With the advent of single-page sites and multiple ajax pages under them however, the hash section of a query parameter is increasingly unable to be used. On Angular 1 with angular-route this becomes impossible.

So what if for example you want to have some references at the top of a page within an Angular application which will scroll the user down to certain sections below, just like the hash references used to do? There are a number of suggestions on the internet for this but they are not very reusable, so I decided to create a simple directive that does this:

This is slightly complicated by the fact that I am using an element with class="main-page" with overflow: auto set to contain the scrollable section of the app. If you don’t have a layout like this just replace the $('.main-page') part with $('body').

Then you can easily create elements like:

Full-stack Linux development (AngularJS, Bootstrap, Modern Perl) and Life in Turkey