Solutions to multiple issues with SSL certificates

  • ATTENTION! As of November 1, 2020, you are not able to reply to threads 6 months after the thread is opened if there are more than 500 posts in the thread.
    Threads will not be locked, so posts may still be edited by their authors.
    Just start a new thread on the topic to post if you get an error message when trying to reply to a thread.


New Around Here
Model: RT-AC86U
Firmware Version: 386.1_beta2

Hi all, I was recently playing with SSL certificates on my router and discover a few things which imho can be helpful to solve problems with SSL certificates. Probably everything below was already mentioned somewhere on the forum, but when I was looking for solutions to my problems I had to read multiple threads and look for individual helpful comments, so I thought putting all of that into one place can be a good idea. Originally I posted these notes on the Asuswrt-Merlin's GitHub.

Generating a new self-signed cert
In WAN - DDNS menu, If you select HTTPS/SSL Certificate as None and Generate a new certificate as Yes then after applying - nothing changes, you still get the old certificate. The reason is /jffs/cert.tgz archive file, which stores 2 files within etc folder: cert.pem and key.pem. If the file exists, then new cert is not generated.

Solution? Ssh into your router and run rm /jffs/cert.tgz before generating a new cert. Now, when applying the above, a new /jffs/cert.tgz file would be created and cert files in /tmp/etc - successfuly replaced.

@RMerlin: my opinion - removing the old file should be just done under-the-hood.

Importing your own cert
In WAN - DDNS menu, If you select Import Your Own Certificate then after uploading files and applying - it works (even if you get No certificate found status). What is interesting here - the uploaded files are stored in /jffs/.cert/ directory, but /jffs/cert.tgz is not modified - it still stores the old cert files. I expected it can be a problem after reboot, but... it isn't, the cert moved to /tmp/etc/ is still the new one. Tbh that's quite surprising to me, I need to investigate it more, but well - the most important part is "it works".

@RMerlin: however it works, maybe it's a good idea to overwrite existing /jffs/cert.tgz anyway to have a repeatable flow?

Generating a certificate from Let's Encrypt (for a custom DDNS)
In WAN - DDNS menu, If you select Free Certificate from Let's Encrypt then after applying - nothing changes. It doesn't matter if you have /jffs/cert.tgz or any files in /jffs/.cert/ - it just doesn't work. If you look at logs, you can see such a line: Dec 24 02:53:29 rc_service: httpd 7936:notify_rc restart_ddns_le;restart_ftpd, but restart_ddns_le seems not to do anything interesting.

But... when you ssh into your router and run service restart_letsencrypt... magic happens and the process of ordering the cert starts - you can track it in System Log -> General Log. The domain used is ofc the one specified in the field Host Name. After all, you can cd /jffs/.le and you will see a new folder named as your domain (e.g.

However, we are only halfway there - the cert is not working yet. But let's do some experiment - we would get the freshly generated key and cert and pack it into /jffs/cert.tgz:
  1. If we look at /jffs/.le/, there are 2 especially interesting files for us: and fullchain.pem.
  2. Let's create a new /jffs/cert.tgz archive file:
    cd /jffs/.le/ && mkdir etc
    cp etc/key.pem && cp fullchain.pem etc/cert.pem
    cd tar -czf /jffs/cert.tgz etc/key.pem etc/cert.pem
  3. Let's reboot: reboot
  4. Voila, it works!
What next? The above doesn't answer if the cert is automatically renewed after 3 months, and even if yes - if it's moved to /tmp/etc/ automatically. But if we you know the mechanism, you can automate it on your own or... @RMerlin - again, maybe it can be automated under-the-hood, when applying Let's Encrypt cert in GUI?

PS I have tested the above for a custom domain, don't know if there are any differences if you want to generate a cert for a default * domain.
Last edited:

Similar threads

Latest threads

Sign Up For SNBForums Daily Digest

Get an update of what's new every day delivered to your mailbox. Sign up here!