F5 BigIP SSL TLS Traffic Decryption Methods and Notes

There are three methods to decrypt SSL encrypted packets on the BigIP:

  • From Jim Shaver’s blog, using your browser
  • Using the SSL Decryption Irule
  • Using the SSLDUMP on the BigIP platform

Jim Shaver’s blog, using your browser

Adding the SSLKEYLOGFILE to environmental setingd


This method simply involves adding a SSLKEYLOG variable to your windows settings and both chrome and firefox will start dumping all the SSL session keys there.

Then you import the file to wireshark under edit > preferences > SSL pre-master session keys.

Note: This only work on Chrome and FF and not on the IE browser.

Using the SSL Decryption Irule

You use the below irule on the virtual server and you get the RSA and Master-Key. This decrypts the client of the traffic only.

if {[IP::addr [IP::client_addr] equals <client_IP_addr>] } {
log local0. "[TCP::client_port] :: RSA Session-ID:[SSL::sessionid] Master-Key:[SSL::sessionsecret]"

Once you have the keys you put them in a .pms file like:

sed -e 's/^.*\(RSA Session-ID\)/\1/;tx;d;:x' /var/log/ltm > /var/tmp/sessionsecrets.pms

Then you import them to the same place as with the first method.


  • If you have route domains on your BigIP then don’t forget to add the route domain to the client IP in the irule, if you miss it the traffic will never match the irule and you won’t see any keys being written to the ltm log.

Using the SSLDUMP on the BigIP CLI

This method requires the use of the private key used to encrypt the session and the pcap file to generate the Pre-Master Secret keys.

Once you capture traffic using TCPDUMP on the BigIP and you want to decrypt the client side of the traffic, you just use:

ssldump -r /path/to/capture_file -k /path/to/private_key -M /path/to/pre-master-key_log_file

For example:

ssldump -r /var/tmp/www-ssl-client1.cap -k /config/filestore/files_d/Common_d/certificate_key_d/\:Common\:test.org.key_1 -M /var/tmp/client1.pms

Now you can get the pcap file and the pms using WinSCP and load them into Wireshark 1.6 and later to view the decrypted traffic.

Wireshark Notes

If you are searching for a string match in Wireshark like a name/password use edit > Find packet > set the option to packet details and string.


  1. UPDATED: 25 JAN 2019.