Assistance with an iRule

Interesting challenge. Try this?

when RULE_INIT {
  set static::key "fc2ed2bf490ad801c04ccd46b9d85b0c"
  set static::iv "7e2fe021d573c0eedd93c4b2704b1b3e"
}

when HTTP_REQUEST_SEND {
  set time [clock seconds]
  set encryptedtime [CRYPTO::encrypt -alg aes-128-cbc -keyhex $static::key -ivhex $static:iv $time]
  HTTP::header remove SECRETTIME
  HTTP::header insert SECRETTIME [b64encode $encryptedtime]
}

You can test it like by applying this rule to a test VIP:

when RULE_INIT {
  set static::key "fc2ed2bf490ad801c04ccd46b9d85b0c"
  set static::iv "7e2fe021d573c0eedd93c4b2704b1b3e"
}

when HTTP_REQUEST {
  set time [clock seconds]
  set encryptedtime [CRYPTO::encrypt -alg aes-128-cbc -keyhex $static::key -ivhex $static::iv $time]
  HTTP::respond 200 SECRETTIME [b64encode $encryptedtime]
}

And then test decrypting with curl and openssl:

curl -sI <ip> | grep SECRETTIME | awk '{print $2}' | openssl enc -a -d -aes-128-cbc -K fc2ed2bf490ad801c04ccd46b9d85b0c -iv 7e2fe021d573c0eedd93c4b2704b1b3e

Edit, made key + iv static to avoid being shamed by the iRules community.
Edit2: Added an example and changed to 32 bit hex key to follow the spec. F5 accepts 16 but openssl does not accept it.

Thanks for helping out Patrik! We REALLY appreciate your help, support and participation!  🙂