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Securing an Ubuntu VM with a free LetsEncrypt SSL certificate in 1 Minute

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I visited https://letsencrypt.org/ where it said Let’s Encrypt is a free, automated, and open SSL Certificate Authority. That sounds great, time to check them out. This may not take 1 minute on your server but it did on mine (a self-managed Ubuntu 16.04/NGINX server). If you are not sure why you need an SSL cert read Life Is About to Get a Whole Lot Harder for Websites Without Https from Troy hunt.

FYI you can set up an Ubuntu Vutur VM here (my guide here) for as low as $2.5 a month or a Digital Ocean VM server here (my guide here) for $5 a month, billing is charged to the hour and is cheap as chips.

Buy a domain name from Namecheap here.

Domain names for just 88 cents!

But for the best performing server read my guide on the awesome UpCloud VM hosts (get $25 free credit by signing up here). Also read my recent post on setting up Lets Encrypt on sub domains.

I clicked Get Started and read the Getting started guide. I was redirected to https://certbot.eff.org/ where it said: “Automatically enable HTTPS on your website with EFF’s Certbot, deploying Let’s Encrypt certificates.“. I was asked what web server and OS I use..

I confirmed my Linux version

Ensure your NGINX is setup (read my Vultr guide here) and you have a”server_name” specified in the “/etc/nginx/sites-available/default” file.

e.g

I also like to set “root” to “/www” in the NGINX configuration.

e.g

Tip: Ensure the www folder is set up first and has ownership.

Also, make and verify the contents of a /www /index.html file.

I then selected my environment on the site (NGINX and Ubuntu 16.04) and was redirected to the setup instructions.

FYI: I will remove mention of my real domain and substitute with thesubdomain.thedomain.com for security in the output below.

I was asked to run these commands

Detailed instructions here.

Obtaining an SSL Certificate

I then ran the following command to automatically obtain and install (configure NGINX) an SSL certificate.

Output

That was the easiest SSL cert generation in history.

SSL Certificate Renewal (dry run)

SSL Certificate Renewal (Live)

The Lets Encrypt SSL certificate is only a 90-day certificate.

Again: The Lets Encrypt SSL certificate is only a 90-day certificate.

I’ll run “certbot renew” again 2 months time to manually renew the certificate (and configure my higher security configuration (see below)).

Certbot NGINX Config renew (what did it do)

It’s nice to see forces HTTPS added to the configuration

Cert stuff added

    listen 443 ssl; # managed by Certbot
ssl_certificate /etc/letsencrypt/live/thesubdomain.thedomain.com/fullchain.pem; # managed by Certbot
ssl_certificate_key /etc/letsencrypt/live/thesubdomain.thedomain.com/privkey.pem; # managed by Certbot
    include /etc/letsencrypt/options-ssl-nginx.conf; # managed by Certbot

Contents of /etc/letsencrypt/options-ssl-nginx.conf

This contains too many legacy cyphers for my liking.

I changed /etc/letsencrypt/options-ssl-nginx.conf to tighten ciphers and add TLS 1.3 (as my NGINX Supports it).

Enabling OCSP Stapling and Strict Transport Security in NGINX

I add the following to /etc/nginx/sites/available/default

Restart NGINX.

SSL Labs SSL Score

I am happy with this.

Read my guide on Beyond SSL with Content Security Policy, Public Key Pinning etc

Automatic SSL Certificate Renewal

There are ways to auto renew the SSL certs floating around YouTube but I’ll stick to manual issue and renewals of SSL certificates.

SSL Checker Reports

‘I checked the certificate with other SSL checking sites.

NameCheap SSL Checker – https://decoder.link/sslchecker/ (Passed). I did notice that the certificate will expire in 89 days (I was not aware of that). I guess a free 90-day certificate for a noncritical server is OK (as long as I renew it in time).

CertLogik – https://certlogik.com/ssl-checker/ (OK)

Comodo – https://sslanalyzer.comodoca.com (OK)

Lets Encrypt SSL Certificate Pros

  • Free.
  • Secure.
  • Easy to install.
  • Easy to renew.
  • Good for local, test or development environments.
  • It auto-detected my domain name (even a subdomain)

Lets Encrypt SSL Certificate Cons

  • The auto install process does not setup OCSP Stapling (I configured NGINX but the certificate does not support it may be to limit the Certificate Authority resources handing the certificate revocation checks).
  • The auto install process does not setup HSTS. (I enabled it in NGINX manually).
  • The auto install process does not setup HPKP. More on enabling Public Key Pinning in NGINX here.
  • Too many cyphers installed by default.
  • No TLS 1.3 installed by default by the install process in my NGINX config in the default certbot secure auto install (even though my NGINX supports it). More on enabling TLS 1.3 in NGINX here.

Read my guide on Beyond SSL with Content Security Policy, Public Key Pinning etc

I’d recommend you follow these Twitter security users

http://twitter.com/GibsonResearch

https://twitter.com/troyhunt

https://twitter.com/0xDUDE

Troubleshooting

I had one server were certbot failed to verify the SSL and said I needed a public routable IP (it was) and that the firewall needed to be disabled (it was). I checked the contents of “/etc/nginx/sites-available/default” and it appeared no additional SSL values were added (not even listening on port 443?????).

Certbot Error

I am viewing: /var/log/letsencrypt/letsencrypt.log

Forcing Certificate Renewal 

Run the following command to force a certificate to renew outside the crontab renewal window.

Conclusion

Free is free but I’d still use paid certs from Namecheap for important stuff/sites, not having OCSP stapling on the CA and 90-day certs is a deal breaker for me. The Lets Encrypt certificate is only a 90-day certificate (I’d prefer a 3-year certificate).

A big thank you to Electronic Frontier Foundation for making this possible and providing a free service (please donate to them)..

Lets Encrypt does recommend you renew certs every 60 days or use auto-renew tools but rate limits are in force and Lets Encrypt admit their service is young (will they stick around)? Even Symantec SSL certs are at risk.

Happy SSL’ing.

Check out the extensive Hardening a Linux Server guide at thecloud.org.uk: https://thecloud.org.uk/wiki/index.php?title=Hardening_a_Linux_Server

fyi, I followed this guide setting up Let’s Encrypt on Ubuntu 18.04.

Read my guide on the awesome UpCloud VM hosts (get $25 free credit by signing up here).

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v1.8 Force Renew Command

v1.7 Ubuntu 18.94 info

V1.62 added hardening Linux server link

Adding a commercial SSL certificate to a Digital Ocean VM

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fyi: Consider reading this first (newer blog post):  How to buy a new domain and SSL cert from NameCheap, a Server from Digital Ocean and configure it.

If you have read my quickest way to setup a scalable development ide and web server guide chances are you setup a www.c9.io development IDE connected and Digital Ocean Ubuntu VM in the cloud for about $5 a month.  It did not take me long to install an NGINX web server, PHP, MySQL and phpMyAdmin sites. The next logical step is to secure my site with an SSL certificate.

I have purchased commercial SSL certificate in the past for a CPanel sub domain and they cost about $150 a year.  I always thought the certificate was set in stone and if it was a weak certificate it would perform poorly in the essential https://www.ssllabs.com/ssltest/index.html certificate tester.

I ran a quick test over my previously purchased managed host provided certificate (lets just say it performs poorly).

Managed WebServices SSL
Managed WebServices SSL Report

Generating a $0 self signed SSL Certificate (Digital Ocean VM)

Digital Ocean have fantastic guides and I searched Google for “digital ocean how to create an ssl certificate” and read this guide. Within a few minutes I had generated a self signed certificate and added it to my NGINX config and had SSL enabled on my site.  The only problem the certificate said it was not trusted by a third party (this may be ok for a closed development box but it would not be good on a production environment).

Self Signed Certificates are not trusted
Self Signed Certificates are not trusted

Generating a $9 commercial SSL Certificate (Digital Ocean VM)

I googled and found this Digital Ocean guide How To Install an SSL Certificate from a Commercial Certificate Authority.

Without listing each step I performed I was able to generate a “key” and “csr” file (from the digital ocean guide, I ignored the Namecheap’s guide). These files are needed to seed the commercial SSL certificate.

I decided to buy a domain certificate from RapidSSL via Namecheap (as they responded to a Livechat support request where GoDaddy ignored the live chat). A Namecheap certificate for my subdomain was going to cost me $9 US a year (that is mega cheap compared to the $150 a CPanel host was going to charge me).  Maybe the $9 certificate will be crap?

I followed the digital ocean guide and to my surprise I had a valid certificate emailed to me within 15 minutes once I followed the process to purchase, verify activate the certificate. To Namecheap’s credit the live chat person (“Anastasia B”) stuck with me as answered frequent questions I had (I thought $9 was too good to be true).

Once I had the commercial keys I was able to generate the private/public keys that feed into the commercial certificate with this command (replace “thesubdomain” with your subdomain and the “the domain” with your domain, if you are not applying the certificate to a subdomain then exclude the sub domain.).

>cd /etc/nginx/ssl/

> openssl req -newkey rsa:2048 -nodes -keyout thesubdomain_thedomain_com.key -out thesubdomain_thedomain_com.csr

The contents of the locally generated certificates were then pasted into the Namecheap SSL pages based on the digital ocean guide. At the end of the Namecheap purchase and verification process I was emailed 4 files that make up the certificate. The Digital Ocean and Namecheap guides were a bit short on combining the certificated but this was the working command to merge the bits intone valid certificate.

> cd /etc/nginx/ssl/

>cat thesubdomain_thedomain_com.crt COMODORSADomainValidationSecureServerCA.crt COMODORSAAddTrustCA.crt AddTrustExternalCARoot.crt >> cert_chain.crt

Then all I had to do was configure NGINX to use the certificate.

> listen 443 ssl;
> server_name thesubdomain.thedomain.com;
> ssl_certificate /etc/nginx/ssl/cert_chain.crt;
> ssl_certificate_key /etc/nginx/ssl/thesubdomain.thedomain.key;

SSL Enabled

A quick restart of the NGINX server and the certificate was good to go, I now had trusted SSL certificate enabled on my site.

I ran a SSL labs test over the site and got a lame C ranking.  WTF, I though SSL was supposed to make sites secure. Maybe there is more I can do to make this secure.

SSL Test After Install
SSL Test After Install

Research and Lockdown Mode

I googled as much as I could find on NGINX and SSL security.

Essential reading:

To me the biggest failing point in the OpenSSL test was a weak PRIME in the Diffe-Hellman crypto,  I thought I could just disable these crypto algorithms but this was not the case.  The secret is to generate a new 2048 bit key on my digital ocean server for ssl to use in connections with browsers instead of the known 1024 bit key.  This was as simple as running this command (and waiting 10 mins):

>cd /etc/nginx/ssl/

> openssl dhparam -out dhparams.pem 2048
>Generating DH parameters, 2048 bit long safe prime, generator 2
>This is going to take a long time

Then when the key is generated you can add it to your NGINX config

>  ssl_dhparam /etc/nginx/path/dhparams.pem;

So after much trial and error this is the bulk of my NGINX configuration

listen 443 ssl;

# Change to your server
server_name thesubdomain.thedomain.com;
# Location of the private key and merged certificates
ssl_certificate /etc/nginx/ssl/cert_chain.crt;
ssl_certificate_key /etc/nginx/ssl/thesubdomain.thedomain.com.key;

# Here are the cyphers we are ignoring
# ssl_ciphers 'ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-AES256-GCM-SHA384:DHE-RSA-AES128-GCM-SHA256:DHE-DSS-AES128-GCM-SHA256:kEDH+AESGCM:ECDHE-RSA-AES128-SHA256:ECDHE-ECDSA-AES128-SHA256:ECDHE-RSA-AES128-SHA:ECDHE-ECDSA-AES128-SHA:ECDHE-RSA-AES256-SHA384:ECDHE-ECDSA-AES256-SHA384:ECDHE-RSA-AES256-SHA:ECDHE-ECDSA-AES256-SHA:DHE-RSA-AES128-SHA256:DHE-RSA-AES128-SHA:DHE-DSS-AES128-SHA256:DHE-RSA-AES256-SHA256:DHE-DSS-AES256-SHA:DHE-RSA-AES256-SHA:AES128-GCM-SHA256:AES256-GCM-SHA384:AES128-SHA256:AES256-SHA256:AES128-SHA:AES256-SHA:AES:CAMELLIA:DES-CBC3-SHA:!aNULL:!eNULL:!EXPORT:!DES:!RC4:!MD5:!PSK:!aECDH:!EDH-DSS-DES-CBC3-SHA:!EDH-RSA-DES-CBC3-SHA:!KRB5-DES-CBC3-SHA';

# Only use a small set of ciphers (may not work on older devices or browsers (but screw them)
ssl_ciphers "EECDH+AESGCM:EDH+AESGCM:AES256+EECDH:AES256+EDH";

# Force only allowing the ciphers above
ssl_prefer_server_ciphers on;

#use the 2048bit DH key
ssl_dhparam /etc/nginx/ssl/dhparams.pem;

# Don't allow old encryption methods like SSL3
ssl_protocols TLSv1 TLSv1.1 TLSv1.2;

# Set SSL caching and storage/timeout values: 
# More info: http://nginx.com/blog/improve-seo-https-nginx/
ssl_session_cache shared:SSL:40m;
ssl_session_timeout 4h;
# Prevent Clickjacking
add_header X-Frame-Options DENY;

# Prevent MIME Sniffing
add_header X-Content-Type-Options nosniff;

# Disable session tickets
ssl_session_tickets off; # Requires nginx >= 1.5.9

# OCSP (Online Certificate Status Protocol) is a protocol for checking if a SSL certificate has been revoked
ssl_stapling on; # Requires nginx >= 1.3.7
ssl_stapling_verify on; # Requires nginx => 1.3.7

# Use Google DNS
resolver 8.8.8.8 8.8.4.4 valid=300s;
resolver_timeout 5s;

# force https over http
add_header Strict-Transport-Security "max-age=63072000; includeSubdomains; preload";

# No need to manually redirect all traffic to https as the header above does this
#rewrite ^/(.*) https://thesubdomain.thedomain.com/$1 permanent;

Conclusion

This is my result on SSLLabs SSL test now. Not bay for $9 and a few hours researching.

Final SSL Labs Score
Final SSL Labs Score

A big Thank You goes to “Anastasia B” on the Namecheap Livechat, they stuck with me while I jumped ahead and ignored the guides.

If you need an SSL certificate choose https://www.namecheap.com/ and don’t forget http://www.digitalocean.com for full access VM’s.

Also listen to this podcast of you an to understand how HTTPS and the internt works.

Also check out how to update your Open SSL and security: https://fearby.com/article/update-openssl-on-a-digital-ocean-vm/

Security

Having ssl may not be enough, do check your website often in https://www.shodan.io and see if it has open software or is known to hackers.
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