cloudflare


Ubuntu SSHD listen to multiple ports

Recently, we’ve setup an Ubuntu server behind CloudFlare that needed to listen for SSH connections.
Unfortunately, CloudFlare does not allow connections to the default SSH port which is 22.
So, to achieve what it was needed we either had to change the port that the SSH service was listening to or add an additional port.
We decided to go with the option of listening to multiple ports for SSH connections, this way users that were also behind the CloudFlare CDN could still continue to use their SSH clients without being forced to define the connection port manually.

The port listening setting is available in /etc/ssh/sshd_config, using sudo we edited the file with a text editor and searched for the following lines:

# What ports, IPs and protocols we listen for
Port 22

Right after the line that contains Port 22, we added another line for the new port (to see the list of all available open ports on CloudFlare, check this post)

And the file became as follows:

# What ports, IPs and protocols we listen for
Port 22
Port 2053

Afterwards, we restarted the SSHD service to apply the changes by executing the following command by using sudo:

systemctl restart ssh;


CloudFlare does not allow port 22 (usual SSH port) on domain 2

When you try to connect via ssh on a domain for which you are using CloudFlare as a HTTP proxy, you will get the following error:

$ ssh [email protected]
 ssh_exchange_identification: Connection closed by remote host

You have a few options to resolve for this issue:

  1. Either connect directly to the IP of the machine.
  2. Or, setup a CNAME record with no HTTP proxy for the SSH (so that you do not need to remember the IP).
    This solution does not offer any additional benefits than connecting directly to the IP of the server.
    To do that, you need to visit the configure DNS page for your site: e.g. https://www.cloudflare.com/a/dns/example.com,
    then create the CNAME named ssh, use as target your domain (e.g. example.com) and disable HTTP proxy by clicking on the orange cloud and making it gray before pressing the Add Record button.

    Then, you will be able to connect via ssh [email protected].
  3. Last solution but not least is configuring your server to listen for SSH on one of the ports of CloudFlare that are open.
    When this post was written, the following ports were available/open for any site in CloudFlare:
    For requests made via HTTP:

    80
    8080
    8880
    2052
    2082
    2086
    2095

    For requests made via HTTPS:

    443
    2053
    2083
    2087
    2096
    8443

    At the time, we were using an Ubuntu GNU/Linux server, to instruct Ubuntu SSHD to listen to multiple ports we edited the file /etc/ssh/sshd_config and right after the lines:

    # What ports, IPs and protocols we listen for
    Port 22

    we added another line with the new port we wanted to use:

    # What ports, IPs and protocols we listen for
    Port 22
    Port 2053

    After restarting the service
    service ssh restart;
    we were able to connect to our page as follows:
    ssh -p 2053 [email protected];

 


Cannot verify domain with Yandex when domain is behind CloudFlare 2

Recently we were trying to verify the ownership of a domain through yandex. We tried the CNAME approach which would be more universal and so we added a new CNAME record in the DNS configuration in CloudFlare.

The record had the following configuration:

  • Type: CNAME
  • Name: yamail-dd63c3831dbd
  • Value: mail.yandex.com
  • TTL: Automatic
  • Status: DNS and HTTP proxy (CDN)

We tried several times the verify domain button in https://domain.yandex.com/domain/example.com/ but it kept on failing saying that the CNAME record was not found. Only after we disabled the DNS and HTTP proxy (CDN) did it work.

So in the end, the properly working record was as follows:

  • Type: CNAME
  • Name: yamail-dd63c3831dbd
  • Value: mail.yandex.com
  • TTL: Automatic
  • Status: DNS Only