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Example for Docker Swarm, Let's Encrypt and Nginx setup with no Nginx down time (answer to https://twitter.com/developius/status/892470102632923136)

This is an answer to https://twitter.com/developius/status/892470102632923136 about his SSL with Docker Swarm, Let's Encrypt and Nginx blog post and a way to not kill Nginx for certificate generation/renewal.

Assumptions

(from what I read in the blog post)

  • Docker hosts have a /etc/letsencrypt directory so that certificates are on the host and not on the container.
  • Docker hosts have a /var/lib/letsencrypt shared copy of the and a (docker run certbot could also re-use containers' /var/lib/letsencrypt volumes.

My proposition

I use /var/lib/letsencrypt/webroot/ as a place for the certbot Webroot plugin (--webroot) to store ACME Challenges, which are then served by Nginx server for "/.well-known/acme-challenge/xxxxxxxxx" HTTP requests only.

Because, certbot's Webroot plugin only need an HTTP (not HTTPS) server to chat with about ACME Challenges, for new domains, I first start Nginx with only the HTTP (port 80) server: the HTTPS (port 443) server block is commented, then run the certbot certonly --webroot command. Once first certificate has been issued, I can enable the HTTPS (port 443) server and reload Nginx.

Future certificate renewal (certbot renew --webroot) part is untouched (same as blog post).

# Create a directory where certbot will place ACME Challenges
# Our Nginx server will also use this as a root for serving files
# when requested for "/.well-known/acme-challenge/xxxxxxxxx".
mkdir -p /var/lib/letsencrypt/webroot
user nginx;
worker_processes 1;
error_log /var/log/nginx/error.log warn;
pid /var/run/nginx.pid;
events {
worker_connections 1024;
}
http {
include /etc/nginx/mime.types;
default_type application/octet-stream;
log_format main '$remote_addr - $remote_user [$time_local] "$request" '
'$status $body_bytes_sent "$http_referer" '
'"$http_user_agent" "$http_x_forwarded_for"';
access_log /dev/stdout main;
sendfile on;
keepalive_timeout 65;
server {
listen 80;
server_name _;
# redirect from http to https
location / {
return 301 https://$host$request_uri;
}
# Rule for legitimate ACME Challenge requests (like /.well-known/acme-challenge/xxxxxxxxx)
location ^~ /.well-known/acme-challenge/ {
# No HTTP authentication
allow all;
# Set correct content type. According to this:
# https://community.letsencrypt.org/t/using-the-webroot-domain-verification-method/1445/29
# Current specification requires "text/plain" or no content header at all.
# It seems that "text/plain" is a safe option.
default_type "text/plain";
# Change document root: this path will be given to certbot as the
# `-w` param of the webroot plugin.
root /var/lib/letsencrypt/webroot;
}
# Hide /acme-challenge subdirectory and return 404 on all requests.
# It is somewhat more secure than letting Nginx return 403.
# Ending slash is important!
location = /.well-known/acme-challenge/ {
return 404;
}
access_log off;
}
#include /etc/nginx/nginx-https_server.conf;
}
server {
listen 443 ssl;
server_name example.com;
ssl_certificate /etc/letsencrypt/live/example.com/fullchain.pem;
ssl_certificate_key /etc/letsencrypt/live/example.com/privkey.pem;
ssl_protocols TLSv1 TLSv1.1 TLSv1.2;
ssl_ciphers HIGH:!aNULL:!MD5;
location / {
# do your thing
}
# No acme ACME Challenge stuff here: Let's Encrypt API uses HTTP for validation
}
version: '3.2'
services:
nginx:
image: nginx:stable-alpine
volumes:
- /etc/letsencrypt:/etc/letsencrypt
- /usr/share/nginx/html:/usr/share/nginx/html
- /var/lib/letsencrypt:/var/lib/letsencrypt
- ${PWD}/nginx.conf:/etc/nginx/nginx.conf
- ${PWD}/nginx-https_server.conf:/etc/nginx/nginx-https_server.conf
deploy:
mode: global
placement:
constraints:
- node.role == manager
ports:
- 80:80
- 443:443
# First time certificate generation
# (No need for 80 nor 443 ports)
docker run --rm \
--name letsencrypt \
-v "/etc/letsencrypt:/etc/letsencrypt" \
-v "/var/lib/letsencrypt:/var/lib/letsencrypt" \
certbot/certbot certonly -n \
-m "YOUR_EMAIL" \
--agree-tos \
-d example.com \
--webroot --webroot-path /var/lib/letsencrypt/webroot/
# Now enable/create the HTTPS nginx VHost
docker exec nginx sed -r 's,^(\s*)#(include /etc/nginx/nginx-https_server.conf;)$,\1\2,' /etc/nginx/nginx.conf
# Reload Nginx
docker kill -s HUP nginx
# Command to run periodically
# (Removed /usr/share/nginx/html, superseded by /var/lib/letsencrypt/webroot)
docker run --rm \
--name letsencrypt \
-v "/etc/letsencrypt:/etc/letsencrypt" \
-v "/var/lib/letsencrypt:/var/lib/letsencrypt" \
certbot/certbot:latest \
renew --quiet --no-self-upgrade
# Reload Nginx
docker kill -s HUP nginx
# Improvement: only reload Nginx if renewall occured (using `--renew-hook` with an `echo` and then grepping the output in Docker host).
@souhaiebtar

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commented Jul 31, 2018

how to add load balancing using upstream ?

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