Re: [chrony-users] Re: NTS Server Setup with Let's Encrypt

[Sviatoslav Feshchenko <sviatoslav.feshchenko@xxxxxxxxx>]

Thank you James and Rob.

I think Rob is right. No matter what I did with permission, it just didn't work. As a workaround, I simply copied the certificates to a different directory and chrony now loads the certificates without issues, and I am now able to synchronize to the server using NTS!

Copying the certificates may be an acceptable solution, because certbot offers pre and post validation hooks, which will execute a script before/after renewal. This script can copy the certificates after renewal and restart chrony, so it should be easy to automate this.

Many many thanks!

Sviatoslav

On Sunday, April 20th, 2025 at 11:53 AM, Rob Janssen <chrony-users@xxxxxxxxx> wrote:

Modern Linux systems often have something like SELinux which limits where certain programs can open files.
Just putting extra config files in "myfolder" isn't going to work, and the error messages can be misleading...

Rob

On 2025-04-20 14:58, Sviatoslav Feshchenko wrote:

Made a bit of progress with the issue. The server error log has the following entry after startup: "Could not set credentials : Error while reading file."

This means it can't read the certificate files.

Tried to change permissions using the following command:

setfacl -R -m u:_chrony:rwx myfolder

Wher myfolder is the directory where the certificates are located.

Still not working, giving same error message.

What would be the correct way of giving chrony permissions to read the certificate files created by certbot, without breaking the web server? I am running Debian 12.

Many thanks!

Sviatoslav

On Saturday, April 19th, 2025 at 9:02 PM, Sviatoslav Feshchenko <sviatoslav.feshchenko@xxxxxxxxx> wrote:

Hello,

I am trying to set up a NTS server suing Let's Encrypt certificate for a web server, but haven't been successful. Here are the steps I've taken:

1. Set up a web server on the same machine as chrony.
2. Set up Let's Encrypt certificates using the certbot tool and the web server is properly serving a test page via HTTPS.
3. In chrony.conf have the following directives relating to NTS:
1. ntsservercert - set to point to the certificate created by certbot for the web server
2. ntsserverkey - set to point to the key created by certbot for the web server
4. Chrony is working just fine in all other respects.
5. Firewall is configured to allow traffic on port 4460 and 123 and routes all such traffic to the chrony server.

I have not taken any other steps other than what's described above.

I am testing the NTS server by using a different machine in a different location on a different public IP that's running chrony and pointing to the server with nts directive. I will refer to this as the client machine.

The client machine does not appear to authenticate the server properly for some reason. Running authdata command in chronyc shows "NTS" in mode column and a small number in column Atmp. All other columns are zero.

On the server machine, running serverstats command in chronyc shows the same number as the client machine in column Atmp, in row "NTS-KE connections accepted. This suggests that the server is receiving an NTS request. Authenticated NTP packets is zero however, suggesting that authentication on the client side failed.

Also, not sure if it matters, but my certificate points to a sub-domain, which is the same sub-domain as I am using as the server name on the client side. However, when I run "sources" command on the client machine, the server domain name resolves to something like "dsl-1-2-3-4-tor.pr where 1-2-3-4 is the actual server IP address. Not sure why it resolves like that, but I am guessing my DNS provider is somehow using the tor network? Could this be the culprit?

Any suggestions on what may be wrong, or how to diagnose the problem?

All your suggestions are always very much appreciated, thank you!

Sviatoslav