Forum Discussion

Nimbostratus

Dec 04, 2020

Cipher negotiated between F5 and Node

Hi There,

We are currently in the process of upgrading F5 from v12 to v13. We came across an issue due to depreciated ciphers. Some of our VIPs were using the DEFAULT cipher suite and since some legacy ciphers were depreciated in the new version, caused an outage for us.

In order to mitigate this issue in future upgrades is there any way to check all the ciphers negotiated between the F5 and Nodes before hand, hence we can verify this against the supported ciphers in the latest version.

Appreciate any other solutions that can mitigate the issue for our scenario.

Thanks in Advance

Cheers

jaikumar_f5
Dec 06, 2020
Here's what you could had done,

1. Run the tmm --clientciphers <suite> command in both the versions and see the difference. Don't forget to frame the command with your existing cipher suite.

2. As you suspect the issue is on the server side, you can run the same command like,
tmm ---serverciphers <suite> and identify the differences. If it's DEFAULT, use DEFAULT.

3. Other option is to use the openssl/curl command to be run against your nodes to see which cipher was selected. I prefer openssl.

4. The easiest way would be to map an irule to log the ciphers. If you want client side, use clientssl_handshake event, since you need on serverside, use serverssl_handshake event and log below entries.

SSL Version - [SSL::cipher version]
Cipher Name - [SSL::cipher name]
Bits Strength - [SSL::cipher bits]

If you need help in framing Irule, let us know.

Samir
MVP
Dec 04, 2020
1. Generate the qkview and upload the ihealth.f5.com
2. Open support care for most stable version in v13.x
3. Do the proper plan before upgrade.

Thanks
- prashanth
  Nimbostratus
  Dec 05, 2020
  i think you are not getting my question here, my question is more simple though, is there any commands available to check the cipher negotiated between F5 and backend node in F5?
  - Samir
    MVP
    Dec 05, 2020
    Capture the packet via ssldump and see the negotiated cipher details.
prashanth
Nimbostratus
Dec 05, 2020
This is also a known solution, even without SSLdump just with simple curl command we can find the cipher. But my question is whether I can see the cipher negotiated with ALL THE NODES with F5 via any command.
jaikumar_f5
MVP
Dec 06, 2020
Here's what you could had done,

1. Run the tmm --clientciphers <suite> command in both the versions and see the difference. Don't forget to frame the command with your existing cipher suite.

2. As you suspect the issue is on the server side, you can run the same command like,
tmm ---serverciphers <suite> and identify the differences. If it's DEFAULT, use DEFAULT.

3. Other option is to use the openssl/curl command to be run against your nodes to see which cipher was selected. I prefer openssl.

4. The easiest way would be to map an irule to log the ciphers. If you want client side, use clientssl_handshake event, since you need on serverside, use serverssl_handshake event and log below entries.

SSL Version - [SSL::cipher version]
Cipher Name - [SSL::cipher name]
Bits Strength - [SSL::cipher bits]

If you need help in framing Irule, let us know.
prashanth
Nimbostratus
Dec 08, 2020
Thank You Jaikumar for the reply.