Enable RemoteConnections with SSL versus Disable RemoteConnections and Use an SSH Tunnel: Which Approach Best Mitigates Unintentional Public Exposure?

Direct answer: disable the remote listener and tunnel over SSH

Disabling Firebird's remote listener and requiring an SSH tunnel is the stronger mitigation against unintentional public exposure. It removes TCP port 3050 from the routable attack surface entirely. Enabling remote connections with wire encryption protects the confidentiality and integrity of traffic, but it does not make the service unreachable; an exposed listener can still be probed, rate-limited, or attacked at the authentication layer.

Confirmed behavior vs. terminology to verify

Firebird 4 uses TCP port 3050 by default, and exposure is controlled by listener binding, firewalling, authentication, and server mode. Transport protection is separate from reachability. The question's phrase "Enable RemoteConnections with SSL" most likely refers to Firebird wire encryption (WireCrypt/CryptPlugin) rather than OpenSSL TLS. Firebird generally does not expose TLS cipher-suite or minimum-version knobs, so do not assume SSL semantics. Confirm the exact listener, wire-crypt, and any per-database encryption parameter names in your target Firebird 4 build's firebird.conf and release notes before applying changes.

Steps for this case

1. Edit firebird.conf to disable the remote listener or bind it only to loopback/a private interface, then restart the Firebird service.
2. Verify the binding scope with ss -tlnp | grep 3050 (or netstat -tlnp | grep 3050). The port should not appear on public interfaces.
3. Configure legitimate clients to connect through an SSH tunnel, for example ssh -L 3050:localhost:3050 user@dbhost, and point the client at localhost:3050.
4. Harden SSH access: use key-based authentication, avoid agent forwarding on shared jump hosts, and rotate keys regularly.
5. Test failover, backup, replication, and monitoring paths before enforcing the policy, because they may rely on direct TCP/3050.

When to keep remote connections enabled

If any legitimate client requires direct TCP/3050 from outside the host or private admin network, do not disable the listener. Instead, bind to loopback or a private interface, firewall port 3050, require strong authentication and wire encryption, restrict users and roles, and monitor failed logins.

Missing diagnostic that changes the recommendation

The single detail needed is whether any legitimate client requires direct TCP/3050 access from outside the host or private admin network. If yes, private binding plus firewall and encryption is the correct path; if no, disabling the listener and tunneling is preferable.

Verification

• After restart, confirm with ss -tlnp that 3050 is absent or bound only to intended addresses.
• From an external host, a direct connection to 3050 should fail when disabled.
• Verify the tunnel works for authorized users and that database logs show no unexpected fallback to unencrypted transport.