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BunnyJunJun's avatar
BunnyJunJun
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Sep 27, 2022

iRule Checking for No Value

Hi All, Just want to check with the fellow community members if you all have any idea on how to use iRules to check for no value? Basically, I am crafting an iRule that search for all headers and s...
security
  • Kevin_Stewart's avatar
    Kevin_Stewart
    Oct 27, 2022

    local0. goes to the LTM log:

    tail -f /var/log/ltm
BunnyJunJun's avatar
BunnyJunJun
Icon for Altostratus rankAltostratus

Hi Kevin,

Thanks! I did roughly the same, however, in your context, x has no value. It is not even a string. Hence, quite hard for me to further "manipulate" x.

I was thinking to concatenate it like those we do for typical coding. (i.e. var temp = "" + x, and temp will be a string with x valueless). Is this possible in terms of iRules?

Kevin_Stewart's avatar
Kevin_Stewart
Icon for Employee rankEmployee
Sep 27, 2022

x is the header name. Are you saying the header doesn't exist?

  • BunnyJunJun's avatar
    BunnyJunJun
    Icon for Altostratus rankAltostratus
    Sep 28, 2022

    Hi Kevin,

    Header exist. An example of the request captured would be as such.

    Header A: valueA
    Header B: valueB
    sec-ch-mobile: 
    Header C: valueC

    Given the idea of above, sec-ch-mobile has no value and it is not an empty string. As such, how do i check for x is an empty value given your sample iRules above?

    • Kevin_Stewart's avatar
      Kevin_Stewart
      Icon for Employee rankEmployee
      Sep 28, 2022

      Not sure I completely understand. the sec-ch-mobile header has no value and is not an empty string? I don't think it can be both of these. Try logging what the value actually is:

      when HTTP_REQUEST {
    foreach x [string tolower [HTTP::header names]] {
        if { $x starts_with "sec-ch" } {
            log local0. "header($x) == |[HTTP::header $x]|"
        }
    }
}

      I put the pipes in there to show if there's actually just white space. Still technically a non-empty string, not equal to "".

      • BunnyJunJun's avatar
        BunnyJunJun
        Icon for Altostratus rankAltostratus
        Oct 27, 2022

        Hi Kevin, any idea how do i access the logs? I am accessing via putty and when i am in the tmsh, i tried to quit tmsh and the whole command prompt just closes.. 😞