Configuring OpenSSL 3.x to Use Only the Default Provider for TLS Termination

Desired outcome

Run a TLS‑terminating service (e.g., nginx, Apache, or a custom server) that uses only OpenSSL 3.x’s default provider for all cryptographic primitives. The legacy provider must not be loaded, so the set of available algorithms is deterministic and can be audited for compliance.

Prerequisites

• OpenSSL 3.0 or later built with provider support (check with openssl version -a).
• Administrative access to the server’s OpenSSL configuration file (typically /etc/ssl/openssl.cnf or an application‑specific config).
• PEM‑encoded server certificate and private key ready for use.
• A test client capable of TLS 1.2+ handshakes (e.g., openssl s_client).
• Ability to restart the TLS‑terminating service and inspect its logs.

Procedure

1. Backup the existing configuration

   sudo cp /etc/ssl/openssl.cnf /etc/ssl/openssl.cnf.bak

2. Edit the provider section Locate the [provider_sect] block (or create it if missing) and ensure only the default provider is listed. Example snippet:

   [provider_sect]
   default = default_sect
   
   [default_sect]
   activate = 1
   

   If a legacy entry exists, comment it out or remove it.
3. Set protocol and cipher restrictions In the same file (or in the application’s SSL config) add:

   MinProtocol = TLSv1.2
   CipherString = DEFAULT@SECLEVEL=2
   

   This disables TLS 1.0/1.1 and limits ciphers to those considered secure by the default provider.
4. Verify the syntax

   openssl cnf-test -f /etc/ssl/openssl.cnf

   Correct any errors before proceeding.
5. Restart the TLS service Example for nginx:

   sudo systemctl restart nginx

   For other services, use the appropriate restart command.

Expected checks

• Version and build info

  openssl version -a

  Confirm the output shows OpenSSL 3.x and built on: date.
• Loaded providers

  openssl list -providers

  Expect only default (and possibly base) to appear; legacy should be absent.
• TLS handshake test Replace HOST and PORT with your service’s address:

  openssl s_client -connect HOST:PORT -servername example.com -tls1_3

  Look for lines like:

  Protocol  : TLSv1.3
  Cipher    : TLS_AES_256_GCM_SHA384
      

  The negotiated cipher must be one offered by the default provider.
• Log inspection Check the service journal or logs for provider initialization messages, e.g.,

  journalctl -u nginx | grep -i "provider default"

  Ensure there are no warnings about loading the legacy provider or attempting to use deprecated algorithms.

Recovery options (rollback)

Because the procedure changes the OpenSSL configuration and restarts the service, you can revert as follows:

1. Restore the backup configuration

   sudo cp /etc/ssl/openssl.cnf.bak /etc/ssl/openssl.cnf
   sudo systemctl restart nginx

2. Temporarily re‑enable the legacy provider Edit /etc/ssl/openssl.cnf to add a legacy entry in [provider_sect] and set its activate = 1. Restart the service and verify connectivity with older clients.
3. Relax protocol or cipher constraints If only a subset of modern clients fails, adjust MinProtocol to TLSv1.0 or modify CipherString to include DEFAULT@SECLEVEL=1, then restart.
4. Rollback the OpenSSL binary If the service binary itself was upgraded and you suspect a regression, reinstall the previous OpenSSL package (using your distribution’s package manager) and restart the service.

Limitations and practical verification

• Provider names and config directives differ slightly between OpenSSL 3.0, 3.1, and 3.2. Consult the man page for config(5) matching your installed version before applying the snippet.
• Disabling the legacy provider removes support for MD5‑based signatures, RC4, DES, and other deprecated algorithms. Existing clients or certificates that rely on these will fail the handshake.
• Using only the default provider does **not** imply FIPS validation. FIPS mode requires a separate, validated fips provider and explicit activation via OPENSSL_CONF or application code.
• After any change, repeat the checks in the Expected checks section. Success is confirmed when:
  • openssl list -providers shows only default (and base).
  • A TLS 1.2/1.3 handshake completes with a cipher from the default suite.
  • Service logs contain provider initialization lines for default and no legacy‑related warnings.