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chic_cat_324145's avatar
Icon for Altocumulus rankAltocumulus
Sep 18, 2018

SSL Proxy

Hello, I have multiple puppet masters behind f5 and would like to offload ssl on F5 and encrypt it again and pass to backend server. I created: a) client ssl profile (uploaded cert + private key from puppet masters) b) server ssl profile


a and b - enabled SSL PROXY


Created Pools, VIP, selected certs.


When I try to access pool through https getting this output:


  • Rebuilt URL to:
  • Trying
  • Connected to ( port 8140 (0)
  • ALPN, offering h2
  • ALPN, offering http/1.1
  • Cipher selection: ALL:!EXPORT:!EXPORT40:!EXPORT56:!aNULL:!LOW:!RC4:@STRENGTH
  • successfully set certificate verify locations:
  • CAfile: /etc/ssl/cert.pem CApath: none
  • TLSv1.2 (OUT), TLS handshake, Client hello (1):
  • LibreSSL SSL_connect: SSL_ERROR_SYSCALL in connection to
  • stopped the pause stream!
  • Closing connection 0 curl: (35) LibreSSL SSL_connect: SSL_ERROR_SYSCALL in connection to

L4 works just fine - so not an issue on the backend servers.


Any thoughts?




9 Replies

  • Can you possibly capture the SSL handshake on the BIG-IP using ssldump? Please refer to the following article:


    K10209: Overview of packet tracing with the ssldump utility


    What version of LibreSSL are you using on the back-end servers? The reason I'm asking is that some people have resolved this by simply upgrading LibreSSL.


    benoittgt commented on 22 Jan


    I update with brew, libressl, openssl and curl and reboot my machine. It's now working.



  • As Philip states, it really would be helpful to see the ssldump transaction. That it seems to fail directly after the ClientHello usually suggests that the client and server's cipher lists are incompatible. If the server is the one severing the connection, then it could also be that the client is sending, or maybe not sending, an extension (like Server Name).


  • Waiting for ssh access... Meanwhile, maybe somebody sees any issues with this config?










  • Sorry guys, I got stuck with ssldump utility:


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


    Where to I get private key? I'm in tmos utility.


    Also, how would I capture traffic for a specific VIP after it's offloaded?


    This doesn't work: tcpdump -vvv -s 0 -nni external host and port 8140




  • Okay, two things.

    • Why do you have SSL Forward Proxy enabled? You definitely shouldn’t need this. SSLFWD is used when the F5 is a forward proxy (for outbound traffic) and you need to re-issue (forge) remote server certs. I think you’re just dealing with a reverse proxy here, so you just need the server cert and key in the client SSL profile, and probably just the generic serverssl profile.

    • You don’t need to specify a key in the ssldump. That’d be if you were trying to decrypt the traffic, and would also only work with non-PFS (RSA key exchange) ciphers. You just need a very simple ssldump command like this:

      ssldump -AdNn -i [vlan name] port 443 [and any additional display filters]
  • So just to be clear from Philip's last post, you also MUST set the Trusted Certificate Authorities option. This is what the BIG-IP uses to validate the client certificate, and will fail without it. Minimally this is a single self-signed root CA, but in reality should be a text file containing the entire PKI CA chain in PEM format.

    ----- BEGIN CERTIFICATE -----
    ----- END CERTIFICATE -----
    ----- BEGIN CERTIFICATE -----
    ----- END CERTIFICATE -----    

    So is it that [X509::subject [SSL::cert 0]] doesn't work because client cert auth is failing? If you insert a log statement, does the log return the correct value?

    log local0. "cert = [X509::subject [SSL::cert 0]]"

    It looks like you're getting all the way through a first TLS handshake, then failing on a second, and you're definitely passing a certificate, so an improvement. An ssldump will still be helpful.

    And last, what are you trying to do once you've set the variable? And how does puppet expect to receive the client cert? Can it consume an HTTP header? Or does puppet strictly require the client cert in a TLS handshake?

  • One more question, Let's say a client doesn't have a cert signed with CA, in this model F5 would throw an error (unauth).


    In fact CA is behind F5, is there a way to allow cert requests to flow through F5 without auth through the same VIP and port?




    • Kevin_Stewart's avatar
      Icon for Employee rankEmployee

      You can set the certification auth option to 'request' vs. 'require'. It'll prompt for a cert, but still let clients through if they don't present a cert.