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Solving HTTP 01 Challenge Failed Issue in Certbot-NGINX

There has been a problem with certificates failing to renew, especially for those who use the python-certbot-nginx plugin to handle certificate installation and renewal on their web servers. One frequent situation that increases this issue is when we choose a different location for the acme-challenge directory than the installation root standard folder. This is often the case when we use NGINX as a proxy for another service.

Users often get an error message similar to this one during the renewal process: “Failed authorization procedure…Connection refused.” When using programs like curl or wget to test connectivity, the connection always returns a 404 error. So, to make sure that the http-01 challenge succeeds, fixing this issue usually entails removing the previous certificate config and setting it up again using the certbot-nginx plugin.

After trying different things and testing a lot, we found an issue in how plugins were chosen. It is expected the system to use “Authenticator nginx” and “Installer nginx,” but it was actually picking “Authenticator webroot” and “Installer nginx” by mistake. This caused authentication problems because of the unusual acme-challenge folder location.

Solutions

1. Open the /etc/cron.d/certbot file and add the –nginx option to the renew command. This option should be added automatically by the python-certbot-nginx plugin, but sometimes it doesn’t.

2. If we encounter an error and port 443 is not open in the firewall, this could be the cause of the problem.

3. If the domain is protected by Cloudflare and has a WAF rule for country restriction, it may block traffic from the origin server. Temporarily turning off country restrictions can help resolve this issue.

4. Always use the latest version of Certbot, as it provides more detailed error messages for fixing.

i. Install the latest version using Snap:

sudo snap install certbot --classic

ii. Use the /snap/bin/certbot binary instead of the default /usr/bin/certbot binary:

sudo /snap/bin/certbot --webroot --agree-tos --redirect --hsts --staple-ocsp -d example.com

iii. Optionally, create a symbolic link so that the terminal automatically uses the Snap version of Certbot:

sudo ln -sf /snap/bin/certbot /usr/bin/certbot

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Conclusion

This article offers the steps from our Experts to fix the http 01 challenge failed issue in Certbot-NGINX framework.