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Letsencrypt Certificate Renewal for Google App Engine

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I’ve been using letsencrypt for vphone for a while, and every time I need to renew the certificates, I face new problems and surprises. Originally I had setup letsencrypt for my website by following this. Tonight, the problem was that I was getting the following error when going through my notes on how to renew the certificates, just after running letsencrypt/letsencrypt-auto renew in certbot:

Attempting to renew cert from /etc/letsencrypt/renewal/ produced an unexpected error: The manual plugin is not working; there may be problems with your existing configuration.
The error was: PluginError('An authentication script must be provided with --manual-auth-hook when using the manual plugin non-interactively.',). Skipping.
The Problem

Looking for the cause, I saw that a new parameter has been added to the manual plugin of certbot which was stopping me from renewing the certificates.

The Solution

To solve the issue, I added a small bash script to my project to help in automating the letsencrypt website validation under letsencrypt directory of my GAE project:

DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
echo "$CERTBOT_VALIDATION" > "$DIR/.well-known/acme-challenge/$CERTBOT_TOKEN"
gcloud app deploy -q "$DIR/../app.yaml"

The above script will put the challenge provided by letsencrypt into the correct location in my project and deploys the project to GAE.

Then, I changed the previous configuration of letsencrypt to use the above script, by adding the last line to the contents of /etc/letsencrypt/renewal/

# renew_before_expiry = 30 days
version = 0.12.0
cert = /etc/letsencrypt/live/
privkey = /etc/letsencrypt/live/
chain = /etc/letsencrypt/live/
fullchain = /etc/letsencrypt/live/
archive_dir = /etc/letsencrypt/archive/

# Options used in the renewal process
authenticator = manual
installer = None
account = <hidden>
manual_public_ip_logging_ok = True
manual_auth_hook = /home/user/my-appengine-project/letsencrypt/

Running letsencrypt/letsencrypt-auto renew again, I did not see any errors this time, and the certificates were generated successfully. The next step was uploading the new certificates to the GAE, as described in the post I mentioned in the beginning.