In a previous post I discussed creating an HTTP API in q. Back then I mentioned that I may explore adding HTTPS support at a later point; I’ve recently had a chance to give this a try, and thanks to Let’s Encrypt it’s very easy to do!

This will work regardless of whether you are using the webapi library from my previous post (now available from conda: conda install -c jmcmurray webapi - see this post about q package management for more details on that) or another custom definition (or even the default q HTTP interface).

Step one is to generate your certificates; this is pretty simple using certbot from Let’s Encrypt. This is a fairly straightforward process, documented here [instructions for various OSes available]. For example on Ubuntu, once certbot is installed we simply do something like:

sudo certbot certonly --standalone -d

(obviously is a domain I control). Certs will be generated in e.g. /etc/letsencrypt/live/

jonny@grizzly ~ $ sudo ls -lFh /etc/letsencrypt/live/
total 4.0K
lrwxrwxrwx 1 root root  43 Oct 25 15:08 cert.pem -> ../../archive/
lrwxrwxrwx 1 root root  44 Oct 25 15:08 chain.pem -> ../../archive/
lrwxrwxrwx 1 root root  48 Oct 25 15:08 fullchain.pem -> ../../archive/
lrwxrwxrwx 1 root root  41 Dec  8 14:10 -> /etc/letsencrypt/live/
lrwxrwxrwx 1 root root  46 Oct 25 15:08 privkey.pem -> ../../archive/
-rw-r--r-- 1 root root 682 Oct 25 15:08 README

As the certs are created as root, we have a couple of options. We could run our q server as root, allowing us to read the certs. Alternatively, we can copy (as root) to another readable location e.g.

jonny@grizzly ~ $ mkdir certs
jonny@grizzly ~ $ sudo su
root@grizzly:/home/jonny# cp /etc/letsencrypt/live/* certs/
cp: -r not specified; omitting directory '/etc/letsencrypt/live/'
root@grizzly:/home/jonny# exit
jonny@grizzly ~ $ ll certs/
total 20K
-rw-r--r-- 1 root root 2.2K Dec  8 15:06 cert.pem
-rw-r--r-- 1 root root 1.7K Dec  8 15:06 chain.pem
-rw-r--r-- 1 root root 3.8K Dec  8 15:06 fullchain.pem
-rw-r--r-- 1 root root 1.7K Dec  8 15:06 privkey.pem
-rw-r--r-- 1 root root  682 Dec  8 15:06 README

Now we can set the necessary environment variables & load up our q session:

jonny@grizzly ~ $ export SSL_CERT_FILE=~/certs/fullchain.pem
jonny@grizzly ~ $ export SSL_KEY_FILE=~/certs/privkey.pem
jonny@grizzly ~ $ q -E 1 -p 8100
KDB+ 3.6 2018.05.17 Copyright (C) 1993-2018 Kx Systems
l32/ 2()core 1944MB jonny grizzly NONEXPIRE

q)\l git/qwebapi/example.q

(Here I load my webapi module previously mentioned & the same example script I used in my previous post on HTTP APIs)

Now, we can query the API over HTTPS:


All in all, the process is pretty simple & straightforward, and takes about 5 minutes. As a couple of closing notes:

  • Using -E 1 as I showed here still allows HTTP access; with -E 2 only HTTPS is allowed (however, HTTP requests will not be redirected to HTTPS - I’ll be looking into this in future)
  • As per the kx docs -u 1 should be used to prevent remote access to your server key file, & q should not be run from a directory where the keys can be accessed

UPDATE: After publishing this post, I realised that kdb+ seemingly does not publish the full certificate chain it is provided, only the server certificate.

This means that, when using Let’s Encrypt, the intermediate LE certificate is not provided to clients. Some clients (e.g. web browsers) will download the intermediate(s) as necessary & the user will likely not notice anything is “wrong”. Other clients (e.g. another q session) will not, and will therefore fail to verify the server certificate.

HTTPS Chain Report from SSL Labs

In order to send an HTTPS query from another q session, you will need to either disable SSL server verification (set env var SSL_VERIFY_SERVER=NO before starting q) or add your server cert to the CA bundle you are using.