Nginx – Let’s Encrypt Nginx-plugin installation and usage

lets-encryptnginxssl

Let's Encrypt just released their open beta, which is great.

I'm using Nginx as a webserver and I know that Let's Encrypt so far only supports Nginx via plugin.

Now the problem is this:
I'm not quite sure how I should install and use that plugin.

I've been trying to run it with this command, referred from their documentation :

./letsencrypt-auto certonly --standalone -d example.com -d www.example.com

And changed –standalone to nginx ofc

No matter how I've tried, the result answer is always the same:

$ The requested nginx plugin does not appear to be installed

Any ideas how to make nginx and Let's Encrypt work together?

Cheers!

Best Answer

Time passes and it seems that now

letsencrypt-auto certonly --standalone

now works as expected

The README.rst supplied as part of the git repo you reference in your question has this to say

nginx/0.8.48+ (highly experimental, not included in letsencrypt-auto)

Erm ... that's it.

_{Iain's reading manuals as a service (RMAAS) at your erm ... service}

Manual plugin

You can either perform a manual verification - with the manual plugin.

certbot -d bristol3.pki.enigmabridge.com --manual --preferred-challenges dns certonly

Certbot will then provide you instructions to manually update a TXT record for the domain in order to proceed with the validation.

Please deploy a DNS TXT record under the name
_acme-challenge.bristol3.pki.enigmabridge.com with the following value:

667drNmQL3vX6bu8YZlgy0wKNBlCny8yrjF1lSaUndc

Once this is deployed,
Press ENTER to continue

Once you have updated the DNS record, press Enter, certbot will continue and if the LetsEncrypt CA verifies the challenge, the certificate is issued as normally.

You may also use a command with more options to minimize interactivity and answering certbot questions. Note that the manual plugin does not yet support non-interactive mode.

certbot --text --agree-tos --email you@example.com -d bristol3.pki.enigmabridge.com --manual --preferred-challenges dns --expand --renew-by-default  --manual-public-ip-logging-ok certonly

Renewal does not work with the manual plugin as it runs in non-interactive mode. More info in the official certbot documentation.

Update: manual hooks

In the new certbot version you can use hooks, e.g., --manual-auth-hook, --manual-cleanup-hook. The hooks are external scripts executed by certbot to perform the task.

Information is passed in environment variables - e.g., domain to validate, challenge token. Vars: CERTBOT_DOMAIN, CERTBOT_VALIDATION, CERTBOT_TOKEN.

certbot certonly --manual --preferred-challenges=dns --manual-auth-hook /path/to/dns/authenticator.sh --manual-cleanup-hook /path/to/dns/cleanup.sh -d secure.example.com

You can write your own handler or use already existing ones. There are many available, e.g., for Cloudflare DNS.

More info on official certbot hooks documentation.

Automation, Renewal, Scripting

~~If you would like to automate DNS challenge validation it is not currently possible with vanilla certbot.~~ Update: some automation is possible with the certbot hooks.

We thus created a simple plugin that supports scripting with DNS automation. It's available as certbot-external-auth.

pip install certbot-external-auth

It supports the DNS, HTTP, TLS-SNI validation methods. You can either use it in handler mode or in JSON output mode.

Handler mode

In handler mode, the certbot + plugin calls external hooks (a program, shell script, Python, ...) to perform the validation and installation. In practice you write a simple handler/shell script which gets the input arguments - domain, token and makes the change in DNS. When the handler finishes, certbot proceeds with validation as usual.

This gives you extra flexibility, renewal is also possible.

Handler mode is also compatible with Dehydrated DNS hooks (former letsencrypt.sh). There are already many DNS hooks for common providers (e.g., CloudFlare, GoDaddy, AWS). In the repository there is a README with extensive examples and example handlers.

Example with Dehydrated DNS hook:

certbot \
    --text --agree-tos --email you@example.com \
    --expand --renew-by-default \
    --configurator certbot-external-auth:out \
    --certbot-external-auth:out-public-ip-logging-ok \
    -d "bristol3.pki.enigmabridge.com" \
    --preferred-challenges dns \
    --certbot-external-auth:out-handler ./dehydrated-example.sh \
    --certbot-external-auth:out-dehydrated-dns \
    run

JSON mode

Another plugin mode is JSON mode. It produces one JSON object per line. This enables a more complicated integration - e.g., when Ansible or some deployment manager is calling certbot. Communication is performed via STDOUT and STDIN. Cerbot produces JSON objects with data to perform the validation, for example:

certbot \
    --text --agree-tos --email you@example.com \
    --expand --renew-by-default \
    --configurator certbot-external-auth:out \
    --certbot-external-auth:out-public-ip-logging-ok \
    -d "bristol3.pki.enigmabridge.com" \
    --preferred-challenges dns \
    certonly 2>/dev/null

{"cmd": "perform_challenge", "type": "dns-01", "domain": "bs3.pki.enigmabridge.com", "token": "3gJ87yANDpmuuKVL2ktfQ0_qURQ3mN0IfqgbTU_AGS4", "validation": "ejEDZXYEeYHUxqBAiX4csh8GKkeVX7utK6BBOBshZ1Y", "txt_domain": "_acme-challenge.bs3.pki.enigmabridge.com", "key_auth": "3gJ87yANDpmuuKVL2ktfQ0_qURQ3mN0IfqgbTU_AGS4.tRQM98JsABZRm5-NiotcgD212RAUPPbyeDP30Ob_7-0"}

Once DNS is updated, the caller sends the new-line character to STDIN of certbot to signal it can continue with validation.

This enables automation and certificate management from the central management server. For installation you can deploy certificates over SSH.

For more info please refer to the readme and examples on certbot-external-auth GitHub.

EDIT: There is also a new blog post describing the DNS validation problem and the plugin usage.

EDIT: We currently work on Ansible 2-step validation, will be soon off.

Let’s Encrypt – How to Use Let’s Encrypt as a Free SSL Certificate Provider

I have written a pair of how-tos for running Let's Encrypt SSL certs on CentOS: initial setup & cronning it.

And my per-domain (I use the file naming convention of z-<[sub-]domain-tld>.conf) Apache config files look like this:

<VirtualHost *:80>
ServerName domain.tld
Redirect permanent / https://domain.tld/
</VirtualHost>

<VirtualHost *:443>
    SSLCertificateFile /etc/letsencrypt/live/domain.tld/cert.pem
    SSLCertificateKeyFile /etc/letsencrypt/live/domain.tld/privkey.pem
    SSLCertificateChainFile /etc/letsencrypt/live/domain.tld/fullchain.pem
    DocumentRoot /var/www/domain
    ServerName domain.tld
    ErrorLog logs/domain-error_log
    CustomLog logs/domain-access_log \
          "%t %h %{SSL_PROTOCOL}x %{SSL_CIPHER}x \"%r\" %b"
    ServerAdmin user@domain.tld

    SSLEngine on

<Files ~ "\.(cgi|shtml|phtml|php3?)$">
    SSLOptions +StdEnvVars
</Files>
<Directory "/var/www/cgi-bin">
    SSLOptions +StdEnvVars
</Directory>

SetEnvIf User-Agent ".*MSIE.*" \
         nokeepalive ssl-unclean-shutdown \
         downgrade-1.0 force-response-1.0

    <Directory "/var/www/domain">
         Options All +Indexes +FollowSymLinks
         AllowOverride All
         Order allow,deny
         Allow from all
    </Directory>

</VirtualHost>

And my ssl.conf looks like this:

#SSL options for all sites
Listen 443
SSLPassPhraseDialog  builtin
SSLSessionCache         shmcb:/var/cache/mod_ssl/scache(512000)
SSLSessionCacheTimeout  300
Mutex sysvsem default
SSLRandomSeed startup file:/dev/urandom  1024
SSLRandomSeed connect builtin
SSLCryptoDevice builtin
SSLCompression          off
SSLHonorCipherOrder     on
SSLProtocol all -SSLv2 -SSLv3 -TLSv1 -TLSv1.1
SSLCipherSuite ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-SHA384:ECDHE-RSA-AES256-SHA384:ECDHE-ECDSA-AES128-SHA256:ECDHE-RSA-AES128-SHA256

Using Let's Encrypt to get SSL certs (and get your site up to an "A" rating from SSL Labs) is pretty straight-forward - once you get past some of the arcana of the Apache configs and LE command-line arguments.