Install the ExtraHop session key forwarder on a Linux server
The ExtraHop session key forwarder runs as a process on a monitored Linux server running SSL services. The forwarder establishes an SSL-secured connection to an ExtraHop Discover appliance to send all SSL session keys through. The session keys enable the Discover appliance to decrypt SSL/TLS sessions encrypted with Perfect Forward Secrecy (PFS) ciphers.
Before you begin
- Read our blog post: What is Perfect Forward Secrecy?
- Review the list of supported cipher suites that can be decrypted by the Discover appliance when session key forwarding is configured.
- Make sure that the Discover appliance is running firmware version 7.1 or later.
- Make sure that the Discover appliance is licensed for SSL Decryption.
- Install the session key forwarder on one or more Linux servers, either a Debian-based Linux distribution or an RPM-based Linux distribution with a Java-based encryption framework.
- Session key processing on the Discover appliance requires that you upload the server certificate and private key file for any monitored SSL-encrypted service to the Discover appliance. Go to the page in the Admin UI to upload a .pem file that includes both a private key and certificate. You can also upload a password-protected PKCS#12 (.PFX) file.
- Make sure that the server certificates have an RSA public key. DSA and ECDSA public keys are not currently supported.
- The session key forwarder on the Linux server must be able to access a trusted CA certificate from the Linux trust store to validate the certificate (or chain of certificates) that the Discover appliance presents.
- The traffic for each monitored SSL server must be part of the data feed to the Discover appliance.
Enable the SSL session key receiver service
You must enable the session key receiver service on the Discover appliance before the appliance can receive and decrypt sessions keys from the session key forwarder. By default, this service is disabled.
Install the software
Integrate the forwarder with the Java-based SSL application
As an example, many Tomcat environments support customization of Java options in the /etc/default/tomcat7 file. In the following example, adding the -javaagent option to the JAVA_OPTS line causes the Java runtime to share SSL session secrets with the key forwarder process, which then relays the secrets to the Discover appliance so that the secrets can be decrypted.
JAVA_OPTS="... -javaagent:/opt/extrahop/lib/exagent.jar
Validate and troubleshoot your installation
If your Linux server has network access to the Discover appliance and the server SSL configuration trusts the certificate presented by the Discover appliance that you specified when you installed the session key forwarder, then the configuration is complete.
In cases where you might have problems with the configuration, the session key forwarder binary includes a test mode you can access from the command-line to test your configuration.
(Optional) Configure a server name override
If there is a mismatch between the Discover appliance hostname that the forwarder knows (SERVER) and the common name (CN) that is presented in the SSL certificate of the Discover appliance, then the forwarder must be configured with the correct CN.
Create a dashboard to see sessions decrypted with a shared secret
When the Discover appliance receives session keys and applies them to decrypted sessions, the Shared Secret metric counter (in
) is incremented. Create a dashboard chart with this metric to see if the Discover appliance is successfully receiving session keys from the monitored servers.
View connected session key forwarders
You can view recently connected session key forwarders after you install the session key forwarder on your server and enable the SSL session key receiver service on the Discover appliance. Note that this page only displays session key forwarders that have connected over the last few minutes, not all session key forwarders that are currently connected.
- Log into the Admin UI on the Discover appliance.
- In the System Configuration section, click Capture.
- Click SSL Shared Secrets.
Uninstall the software
If you no longer want the ExtraHop session key forwarder software installed, complete the following steps.
- Log into the Linux server.
-
Open a terminal application and choose one of the following options to remove
the software.
- For RPM-based servers, run the following
command:
sudo rpm --erase extrahop-key-forwarder
- For Debian and Ubuntu servers, run the following
command:
sudo apt-get --purge remove extrahop-key-forwarder
Type Y at the prompt to confirm the software removal and then press ENTER.
- For RPM-based servers, run the following
command:
- Click Yes to confirm.
- After the software is removed, click Yes to restart the system
Common error messages
Errors created by the session key forwarder are logged to the Linux system log file.
Message | Cause | Solution |
---|---|---|
connect: dial tcp <IP address>:4873: connectex: A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond | The monitored server cannot route any traffic to the Discover appliance. | Ensure firewall rules allow connections to be initiated by the monitored server to TCP port 4873 on the Discover appliance. |
connect: dial tcp <IP address>:4873: connectex: No connection could be made because the target machine actively refused it | The monitored server can route traffic to the Discover appliance, but the receiving process is not listening. | Ensure that the Discover appliance is licensed for both the SSL Decryption and SSL Shared Secrets features. |
connect: x509: certificate signed by unknown authority | The monitored server is not able to chain up the Discover appliance certificate to a trusted Certificate Authority (CA). | Ensure that the Linux certificate store for the computer account has trusted root certificate authorities that establish a chain of trust for the Discover appliance. |
connect: x509: cannot validate certificate for <IP address> because it doesn't contain any IP SANs | An IP address was supplied as the SERVER parameter when installing the forwarder, but the SSL certificate presented by the Discover appliance does not include an IP address as a Subject Alternate Name (SAN). | Select from the following three solutions.
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