Forum Discussion

Cirrus

Sep 17, 2021

[Irule][ASM] Header name with no header value

Hi all I have setup a ASM profile and all my application will through BIG-IP WAF. But I have a issue " HTTP Protocol Compliance Failed: Header name with no header value " for a resquest with heade...

Cirrostratus

Sep 17, 2021

Hi Hoang Hung,

You can check this article: Disabling a violation for a URL using an iRule (f5.com)

According to article, first get the violation name in a separate irule and then use that violation name in second irule with your host header condition. Do not forget to change the "Specific_ASM_Violation" value with the name of matched violation, when the request with header name "abc" has no value.

when ASM_REQUEST_DONE {
  if {[ASM::violation names] contains "Specific_ASM_Violation" and [HTTP::header "abc"] equals "" } {
    ASM::unblock
    log local0. "ASM unblocking"
  }
}

Hoang_Hung
Cirrus
Sep 18, 2021
Thank Oguzy
I was been read article, I saw F5 use irule get violation name.
But I had event log on F5. Is it Http protocol compliance failed , right ?
Thanks
Hoang Hung
- oguzy
  Cirrostratus
  Sep 18, 2021
  Hi Hoang,
  
  Could you please try to determine the exact violation name using the following steps:
  
  Log in to the Configuration utility.
  Go to Local Traffic > iRules > iRule list.
  Select Create.
  For Definition, enter the following iRule code:
  when ASM_REQUEST_DONE {
  log local0. "ASM violation name: [ASM::violation names]"
  }
  Select Update.
  Associate the iRule with the appropriate virtual server.
  Send a request that triggers the violation that you want to forward to the OWS.
  Log in to the BIG-IP command line and search for the name of the violation.
  For example:
  grep -i violation /var/log/ltm
  The following log entry shows an example of a violation name as it should be used in the iRule:
  tmm[25875]: Rule /Common/asm_violation <ASM_REQUEST_DONE>: ASM violation name: VIOLATION_ILLEGAL_METHOD
  After you determine the violation name that you want to use in the iRule, you can remove the previous iRule from the virtual server configuration.
Irre_Levant
Cirrus
Oct 24, 2023
Ahoi,
what is exactly unblocked here? What if i have multiple violations in one request? Are they all unblocked if one of them contains what is defined in the irule?
Is there another way to remove the empty cookie or header before it reaches the asm processing?