Client-Side HTTPS Support

Client-Side HTTPS Support

Akka HTTP supports TLS encryption on the client-side as well as on the server-side.

The central vehicle for configuring encryption is the HttpsContext, which can be created using the static method HttpsContext.create which is defined like this:

public static HttpsContext create(SSLContext sslContext,
                                  Option<Collection<String>> enabledCipherSuites,
                                  Option<Collection<String>> enabledProtocols,
                                  Option<ClientAuth> clientAuth,
                                  Option<SSLParameters> sslParameters)

In addition to the outgoingConnection, newHostConnectionPool and cachedHostConnectionPool methods the akka.http.javadsl.Http extension also defines outgoingConnectionTls, newHostConnectionPoolTls and cachedHostConnectionPoolTls. These methods work identically to their counterparts without the -Tls suffix, with the exception that all connections will always be encrypted.

The singleRequest and superPool methods determine the encryption state via the scheme of the incoming request, i.e. requests to an "https" URI will be encrypted, while requests to an "http" URI won't.

The encryption configuration for all HTTPS connections, i.e. the HttpsContext is determined according to the following logic:

  1. If the optional httpsContext method parameter is defined it contains the configuration to be used (and thus takes precedence over any potentially set default client-side HttpsContext).
  2. If the optional httpsContext method parameter is undefined (which is the default) the default client-side HttpsContext is used, which can be set via the setDefaultClientHttpsContext on the Http extension.
  3. If no default client-side HttpsContext has been set via the setDefaultClientHttpsContext on the Http extension the default system configuration is used.

Usually the process is, if the default system TLS configuration is not good enough for your application's needs, that you configure a custom HttpsContext instance and set it via Http.get(system).setDefaultClientHttpsContext. Afterwards you simply use outgoingConnectionTls, newHostConnectionPoolTls, cachedHostConnectionPoolTls, superPool or singleRequest without a specific httpsContext argument, which causes encrypted connections to rely on the configured default client-side HttpsContext.

If no custom HttpsContext is defined the default context uses Java's default TLS settings. Customizing the HttpsContext can make the Https client less secure. Understand what you are doing!

Hostname verification

Hostname verification proves that the Akka HTTP client is actually communicating with the server it intended to communicate with. Without this check a man-in-the-middle attack is possible. In the attack scenario, an alternative certificate would be presented which was issued for another host name. Checking the host name in the certificate against the host name the connection was opened against is therefore vital.

The default HttpsContext enables hostname verification. Akka HTTP relies on the Typesafe SSL-Config library to implement this and security options for SSL/TLS. Hostname verification is provided by the JDK and used by Akka HTTP since Java 7, and on Java 6 the verification is implemented by ssl-config manually.


We highly recommend updating your Java runtime to the latest available release, preferably JDK 8, as it includes this and many more security features related to TLS.