Client Auth with Interlock and Nginx

I had the requirement of setting Interlock + Nginx where backend expects client authentication. If you have directly landed up here, to get the context about service discovery and interlock and Nginx, read my previous post.

Note: This topic applies to Interlock 1.3 and Docker 1.11. If you are using docker > 1.12, I recommended to use inbuilt docker load balancer, which ships with swarmkit.

Problem Definition:

Setup client authentication certificates with Interlock + Nginx

Why it a problem: 

Interlock controls the Nginx configuration file. You can’t directly modify the Nginx configuration file, as Interlock would be overwrite when a container starts or dies.

Interlock allows certain data labels which allows you to configure the Nginx configuration file. Read Interlock data label section of previous post for more info.

There are data label to set SSL certificate, set SSL only, set SSL backend, etc. But, there aren’t any labels to set SSL proxy certificate. I had eve raise an issue, to found it not supported.

No data label to configure client authentication certificates is the problem

Possible Solution

If you need to set client authentication certificates with Nginx, serverfault threads hints how to do

backend {
 server some-ip:443;

server {
 listen 80;

   location / {
      proxy_ssl_certificate certs/client.crt;
      proxy_ssl_certificate_key certs/client.key;

      proxy_pass https://backend;

Now, I need to find a way with Interlock, where I could get control of template it uses for configuring the interlock

Hint’s from the interlock docs, where it shows configuration variable TemplatePath  in the toml configuration. It allows us to give the template, which it would use with variable substitution to create final Nginx config.

Again, I can get the example of this template file in interlock docs.

I found this template file a perfect opportunity to modify the template to include client auth certificates in template and use.

 location / {
 # Added by Shabbir 9th Dec 2016, For Client Authentication
 proxy_ssl_certificate /certs/client.crt;
 proxy_ssl_certificate_key /certs/client.key;
 proxy_ssl_password_file /certs/pass.txt;
 # Change End
 {{ if $host.SSLBackend }}proxy_pass https://{{ $host.Upstream.Name }};{{ else }}proxy_pass http://{{ $host.Upstream.Name }};{{ end }}

This certificate needs to be present on the machine where Nginx container would be launch, and they are added to container via volume mounts.

Here, the extract of docker-compose file, which configures nginx container

   image: nginx:latest
   entrypoint: nginx
     - common     
     - 8443:8443
     - 8009
     - interlock
   command: -g "daemon off;" -c /etc/nginx/nginx.conf
   restart: unless-stopped
   labels: nginx
       - "constraint:com.function==interlock"
       - ~/myapp/certs:/certs
       - ~/myapp/logs:/var/log/nginx

This is how I solve the issue of client authentication, but this technique could be use to configure interlock for all the unsupported Nginx scenarios like tcp pass through, etc





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