Configure how Liberator handles direct client connections

This page describes how to configure Liberator’s interface for direct (RTTP over TCP/IP) connections from StreamLink clients.

To configure Liberator’s interface for StreamLink connections that are encapsulated in HTTP, HTTPS, and WebSocket protocols, see Configure how Liberator handles HTTP connections and Configure how Liberator handles HTTPS connections.

Direct connections are supported by all StreamLink libraries except for StreamLink JS. For more information on connection types, see StreamLink connection types.

Direct connections can also use SSL/TLS to provide greater security. The instructions below on setting up secure direct connections apply to Liberator 6.2 release and later, deployed using the Caplin Platform Deployment Framework release 6.2 and later.

Configuring Liberator’s direct port and interface

When you install Liberator to run under the Caplin Platform Deployment Framework, it’s automatically configured to use direct connections through a built-in Config blade called DirectConnection. The Liberator listens for direct connections on all available interfaces, on port 14001.

This type of connection isn’t secure. In a production installation, use direct connections over SSL instead - see Enabling secure connections (SSL) below.

Configuring the direct port

By default, Liberator’s direct RTTP port is 14001. To change the direct port, redefine the LIBERATOR${THIS_LEG}_DIRECTPORT configuration variable in the Deployment Framework’s global_config/environment.conf file:

Setting Liberator’s direct RTTP port to 14051
Do not set the value of the configuration item direct-port directly. Redefine the LIBERATOR${THIS_LEG}_DIRECTPORT configuration variable instead.

Configuring the direct interface

By default, Liberator’s direct and direct SSL server sockets are bound to all network interfaces on Liberator’s host. To bind Liberator’s direct server sockets to one or more network interfaces, redefine the LIBERATOR${THIS_LEG}_DIRECTINTERFACE configuration variable in the Deployment Framework’s global_config/environment.conf file:

Binding Liberator’s direct sockets to two network addresses

The configuration variable supports IPv6 addresses from version 7 of Liberator. To listen for connections on both the IPv4 and IPv6 address of a dual-stack network interface, assign both IP addresses to the macro.

Despite the name of the LIBERATOR${THIS_LEG}_DIRECTINTERFACE variable implying that it applies only to the non-SSL direct server socket, the variable applies to both the direct and direct SSL server sockets.

Do not set the value of the configuration item direct-interface directly. Redefine the LIBERATOR${THIS_LEG}_DIRECTINTERFACE configuration variable instead.

Enabling secure (SSL) direct connections

Liberator’s direct RTTP configuration is provided in two feature blades (config blades): DirectConnection and DirectSSLConnection.

The DirectConnection feature blade is activated by default.

To enable secure direct connections, follow the steps below:

  1. Run the commands below to deactivate the DirectConnection blade and activate the DirectSSLConnection blade:

    ./dfw deactivate DirectConnection
    ./dfw activate DirectSSLConnection
  2. Review the default direct SSL port and interface. See Configuring the direct SSL port and Configuring the direct SSL interface.

  3. Install an SSL/TLS key, password file, and certificate. See Installing keys and certificates.

  4. Review the SSL/TLS protocols and ciphers supported by Liberator’s HTTPS interface (you should also repeat this task periodically as part of a regular security review). See Configuring SSL/TLS protocols and ciphers.

  5. Generate a Diffie-Hellman (DH) parameters file to allow Liberator to use ephemeral Diffie-Hellman (DHE) ciphers. See Generating a Diffie-Hellman parameters file for DHE ciphers.

  6. If this is a production server, disable Liberator’s built-in administrator website:

    ./dfw deactivate LiberatorWebsite
    ./dfw activate MinimalLiberatorWebsite
  7. If this is a production server, enable SSL/TLS for Liberator’s HTTP interface. See Configure how Liberator handles HTTPS connections for more information.

Direct client SSL/TLS implementations

This section provides links to third party resources that document the protocols and ciphers supported by Java and .NET direct clients of Liberator.

Java clients and SSL/TLS

Support for client connections using TLS 1.2 is enabled by default in Oracle JDK 8. See JDK 8 will use TLS 1.2 as default.

.NET Framework clients and SSL/TLS

Direct connections using TLS 1.2 are supported from Caplin StreamLink.NET 7.1, which requires .NET Framework 4.6.

In addition to requiring StreamLink 7.1 and .NET Framework 4.6, support for .NET client connections using TLS 1.2 is also dependant on OS version. See Transport Layer Security (TLS) best practices with the .NET Framework: TLS 1.2.

Cipher suite availability is dependent on OS version. See Cipher Suites in TLS/SSL (Schannel SSP).

Liberator’s SSL/TLS implementation

Liberator uses OpenSSL to provide its implementation of SSL/TLS. The OpenSSL library is built-in to Liberator and is independent of the host system’s installation of OpenSSL.

To determine the version of OpenSSL bundled with a specific release of Liberator, see Liberator’s release notes or run the strings command on the Liberator binary and grep the output:

strings rttpd | grep -i '^openssl [0-9]'

Configuring the direct SSL port

By default, Liberator’s direct SSL port is 14002.To change the HTTPS port, redefine the LIBERATOR${THIS_LEG}_DIRECTSSLPORT configuration variable in the <Framework-root>/global_config/environment.conf file:

Setting Liberator’s direct SSL port to 14052
Do not set the value of the directssl-port configuration item directly. Redefine the LIBERATOR${THIS_LEG}_DIRECTSSLPORT configuration variable instead.

Configuring the direct SSL interface

By default, Liberator’s direct SSL server socket is bound to all network interfaces on Liberator’s host. To bind Liberator’s direct SSL server socket to specific network interfaces, redefine the LIBERATOR${THIS_LEG}_DIRECTSSLINTERFACE configuration variable in the <Framework-root>/global_config/environment.conf file:

Binding Liberator’s direct SSL socket to two network interfaces
Do not set the value of the directssl-interface configuration item directly. Redefine the LIBERATOR${THIS_LEG}_DIRECTSSLINTERFACE configuration variable instead.

Installing keys and certificates

This section describes how to install a key, key password file, and certificate.

Default key and certificate paths

By default, the Deployment Framework (DFW) expects keys and certificates to be stored in the global_config/ssl directory. For convenience in writing configuration, the Deployment Framework sets a configuration variable SSLCERT_PATH to this directory.

For a full list of Deployment Framework configuration variables, see Configuration macros and items.

Liberator’s direct SSL feature blade configures default key and certificate locations as follows:

Default key, passphrase, and certificate paths
File Configuration item Default value




Private key



Private-key passphrase



To override the default paths, assign new paths to directssl-certificate, directssl-privatekey, and directssl-passwordfile in the Deployment Framework file global_config/overrides/servers/Liberator/etc/rttpd.conf.

Deprecation of certificates with MD5- and SHA1-based digital signatures

Certificates signed with an MD5 hash with RSA encryption have long been deprecated and some platforms and libraries no longer support them. The digital security industry now recommends using the SHA-2 family of hashing algorithms in digital signatures.

Liberator’s demonstration self-signed SSL certificate was re-issued with a SHA256-based digital signature in versions 6.2.23, 7.0.5, and 7.1.1 of Liberator. Liberator 7.1 continues to support certificates signed with an MD5 hashing algorithm, but support may be dropped in future.

StreamLink.NET 7.1 is compiled with .NET 4.6, which does not support certificates signed with the MD5 hashing algorithm.

To determine the digital signature algorithm used in a certificate, use OpenSSL’s x509 command to read the certificate and then grep the output:

Determining the digital signature algorithm in certificate 'rttpd_https.pem'
$ openssl x509 -in rttpd_https.pem -text -noout | grep -m1 'Signature Algorithm'
    Signature Algorithm: sha256WithRSAEncryption
Digital signature algorithms used in certificates
Algorithm Status Notes



Not supported by Caplin’s StreamLink.NET 7.1.



See SHA1 Deprecation: What you need to know on the Qualys blog.



Installing certificates for development and testing

For the convenience of developers and software testers, Caplin ships a self-signed demonstration certificate with Liberator.

Do not use Caplin’s self-signed certificate in production.

In versions of the Deployment Framework prior to 7.0.2, the Deployment Framework automatically deploys Caplin’s self-signed certificate with Liberator if no keys and certificate exist for Liberator in the global_config/ssl directory.

From version 7.0.2 of the Deployment Framework, the Deployment Framework does not automatically deploy Caplin’s self-signed certificate with Liberator. To manually deploy the self-signed certificate, run the copy-ssl-demo-files Deployment Framework command:

./dfw copy-ssl-demo-files

When you first connect a web browser to a Liberator that presents Caplin’s self-signed certificate, your web browser will prompt you to trust the certificate.

Installing certificates for production use

Follow the instructions below to install a production certificate:

  1. Follow the instructions provided by your chosen certificate authority (CA) to generate a certificate signing request (CSR) for your Liberator host. When generating the CSR, we recommend that you specify a SHA-2 hashing algorithm or stronger. See Deprecation of certificates with MD5- and SHA1-based digital signatures above.

  2. When your CA delivers a signed certificate, rename the certificate, key, and passphrase files to Liberator’s default file names: rttpd_https.pem, rttpd_https.key, and rttpd_https.pwd.

    If you don’t want to use Liberator’s default file names, edit <Framework-root>/global_config/overrides/servers/Liberator/etc/rttpd.conf, and specify your own file names using the configuration items directssl-certificate, directssl-privatekey, and directssl-passwordfile.

  3. Copy the private key, certificate, and pass phrase file to the <Framework-root>/global_config/ssl/ directory.

If the private key is unencrypted, the password file must be empty.

From Liberator 7.1.9: If the private key is unencrypted and you don’t want to deploy an empty password file, then set the configuration variable HTTPS_PASSWORD_FILE_REQUIRED to NO in the Deployment Framework file global_config/environment.conf.

Configuring SSL/TLS protocols and ciphers

Regularly reviewing Liberator’s list of permitted SSL/TLS protocols and ciphers should be part of your security policy. Security best practices can change quickly.

Review the configuration of Liberator’s SSL/TLS protocols and ciphers for compliance with your security policy before deploying Liberator to production, and regularly review the configuration thereafter.

Liberator defaults

Liberator’s default TLS configuration is balanced in favour of supporting as wide a range of clients as possible, with older clients supported at the cost of enabling deprecated TLS protocols. The default TLS configuration is not updated regularly and is for your initial convenience only; it is not a security recommendation.

If your Liberator does not need to support older clients, then disable Liberator’s support for all protocols older than TLS 1.2 and their associated ciphers. For example configuration, see Example TLS protocol and cipher configuration.

All protocols supported by the version of OpenSSL included with Liberator are enabled unless explicitly disabled by directssl-ssl-options.

Default SSL/TLS protocols
Liberator SSL 2 * SSL 3  TLS 1.0  TLS 1.1  TLS 1.2 TLS 1.3














-   Protocol not available
Protocol disabled (see directssl-ssl-options)
Protocol enabled
* The IETF prohibited SSL 2 in March 2011: RFC 6176
† The IETF deprecated SSL 3 in June 2015: RFC 7568
‡ The IETF recommended TLS 1.0 and TLS 1.1 for deprecation in June 2018: Deprecating TLSv1.0 and TLSv1.1

Default cipher string
Liberator Cipher string

7.1.5 *






* From Liberator 7.1.5, only cipher suites that support forward secrecy (ECDHE and DHE) are enabled by default. DHE ciphers require a Diffie-Hellman parameters file, which is not distributed with Liberator (see Generating a Diffie-Hellman parameters file for DHE ciphers).

Guidance on choosing protocols and ciphers

Choosing which SSL/TLS protocols and ciphers to support is a balance between minimising security risk and supporting the broadest range of clients.

For introductory guidance on choosing protocols and ciphers, read the third-party resources below:

Configuring TLS protocol support

To configure the SSL/TLS protocols supported by Liberator, set the value of the directssl-ssl-options configuration item.

For guidance on choosing which protocols to support, read the third party resources listed in Guidance on choosing protocols and ciphers above.

For example directssl-ssl-options configuration, see Example TLS protocol and cipher configuration below.

Configuring TLS cipher support

To configure the list of SSL/TLS ciphers supported by Liberator, set directssl-cipher-list to an OpenSSL cipher list.

The order of ciphers in directssl-cipher-list does not influence Liberator’s choice of cipher for a TLS connection. In accordance with the TLS specification, given a choice of mutually-supported ciphers for a TLS connection, Liberator chooses the client’s most preferred cipher.

For guidance on choosing which ciphers to support, read the third party resources listed in Guidance on choosing protocols and ciphers above.

If your cipher list includes Ephemeral Diffie-Hellman (DHE) ciphers, you must configure the directssl-dhparams configuration item with the location of a valid Diffie-Hellman (DH) parameters file. If you fail to do so, Liberator silently drops DHE ciphers from its list of supported ciphers. See Generating a Diffie-Hellman parameters file for DHE ciphers.

To view how OpenSSL expands a cipher list to individual ciphers, run the OpenSSL ciphers command with a version of OpenSSL equal to the version included with your release of Liberator:

Expand the cipher list 'ECDHE+TLSv1.2:DHE+TLSv1.2:@STRENGTH'
openssl ciphers -v 'ECDHE+TLSv1.2:DHE+TLSv1.2:@STRENGTH' | column -t

For example directssl-cipher-list configuration, see Example TLS protocol and cipher configuration below.

Example TLS protocol and cipher configuration

The configuration in this section is provided for illustrative purposes only, is not updated regularly, and does not constitute security advice. Review all TLS configuration before deploying to production, and schedule regular reviews thereafter.

This example supports modern direct clients (defined as all clients with support for TLS 1.2 and above).


  • TLS protocols: TLS 1.2, TLS 1.3 (Liberator supports TLS 1.3 from Liberator 7.1.5)

  • TLS ciphers: Forward-secrecy ciphers only (ECDHE, DHE). Weak ciphers removed. Ciphers ordered by strength.

  • Diffie-Hellman parameters: 2048-bit

When the equivalent configuration for Liberator’s HTTPS interface was tested on Liberator 7.1.12 using the SSL Labs Server Test on 27 Apr 2020, the configuration below scored A+. View the SSL Labs report.

While the configuration below achieved an SSL Labs score of A+ on 27 Apr 2020, ciphers may weaken over time and the configuration may not achieve that score today. Retest and review this configuration before considering deploying it to production.
# Disable TLS versions SSLv2, SSLv3, TLSv1, and TLSv1.1
# (retain TLSv1.2 and TLSv1.3)
directssl-ssl-options  SSL_OP_NO_SSLv2|SSL_OP_NO_SSLv3|SSL_OP_NO_TLSv1|SSL_OP_NO_TLSv1_1

# OpenSSL ciphers to include

# OpenSSL ciphers to exclude

# Set OpenSSL cipher string, and order ciphers by strength

# Diffie-Hellman parameters file (for DHE ciphers)
directssl-dhparams     ${SSLCERT_PATH}/rttpd-dhparam-2048.pem

OpenSSL option SSL_OP_NO_TLSv1_1 is supported by directssl-ssl-options from Liberator 7.1.3.

Generating a Diffie-Hellman parameters file for DHE ciphers

Ephemeral Diffie-Hellman ciphers (DHE) ciphers are supported by Liberator from version 6.2.14 and 7.0.1, but are not enabled by default.

DHE ciphers require a Diffie-Hellman (DH) parameter file. If you do not configure the directssl-dhparams configuration item with the location of a valid DH parameters file, Liberator silently removes DHE ciphers from its list of supported ciphers.

No DH parameters file is provided with Liberator; you must generate your own.

To generate a Diffie-Hellman (DH) parameters file, follow the steps below:

  1. In the Deployment Framework’s global_config/ssl/ directory, run the command below:

    openssl dhparam -out rttpd-dhparam-2048.pem 2048

    This command can take a long time to complete.

  2. Assign the location of the DH parameters file to the directssl-dhparams configuration item in the Deployment Framework’s global_config/overrides/servers/Liberator/etc/rttpd.conf file:

    directssl-dhparams ${SSLCERT_PATH}/rttpd-dhparam-2048.pem

To test that a Liberator supports DHE ciphers, follow the steps below:

  1. In the file global_config/overrides/servers/Liberator/rttpd.conf, assign a cipher string containing DHE ciphers to the directssl-cipher-list configuration item. For example:

    directssl-cipher-list ECDHE+TLSv1.2:DHE+TLSv1.2:@STRENGTH
  2. Restart Liberator

  3. Run the command below to test connecting to Liberator using a DHE cipher. The example below tests connecting with the DHE-DSS-AES256-GCM-SHA384 cipher, one of the DHE ciphers included in OpenSSL’s TLS 1.2 cipher suite:

    openssl s_client -cipher cipher -connect host:port

Seeding the OpenSSL random number generator

Configuring OpenSSL

Liberator uses the OpenSSL software to implement the security policies for secure direct connections with clients. You can configure OpenSSL using the following DataSource configuration items, which are defined on the page DataSource Secure Sockets Layer (SSL) configuration:

When you change the configuration of OpenSSL, the new settings apply to all of Liberator’s secure (SSL) connections: Direct secure connections to clients, HTTPS connections and secure connections between Liberator and other DataSource applications.

Improving the security of direct connections

To resist attacks on your system, Liberator includes a configuration option called direct-max-line-length that limits the length of an RTTP message sent across a direct connection. If Liberator receives a message longer than that configured, it’ll reject it rather than reading it continuously until memory runs out.

The default setting for this item should be sufficient, but if you experience security problems, set it to a lower value. Add the new setting to the Deployment Framework file <Framework-root>/global_config/overrides/servers/Liberator/etc/rttpd.conf

See also: