Forum Discussion

Chronos_258816's avatar
Chronos_258816
Icon for Nimbostratus rankNimbostratus
Jul 28, 2016

Host Header Validation

Greetings,   I have been tasked with crafting an iRule to validate the host header of incoming packets to a given virtual server. I have tried a few different irules to attempt this an yet I am t...
iRules
Security
  • VernonWells's avatar
    VernonWells
    Jul 28, 2016

    A data-group is a convenience rather than a necessity.

    I tried the following on 11.5.4:

     

     

    when HTTP_REQUEST {
    if { [HTTP::host] ne "xyz.com" } {
        reject
    }
}

     

     

    I tried all of the following combinations:

    1. HTTP/1.1 Host header xyz.com;
    2. HTTP/1.1 Host header foo.com;
    3. HTTP/1.0 no Host header;
    4. HTTP/1.1 Host header xyz.com followed by HTTP/1.0 no Host header;
    5. HTTP/1.1 Host header xyz.com followed by HTTP/1.1 Host header foo.com

    Case 1: allowed;

    Case 2: rejected (i.e., TCP RST);

    Case 3: rejected;

    Case 4: allowed then rejected;

    Case 5: allowed then rejected.

    Incidentally, if a pool is assigned to the VS, then the else clause isn't needed (it's the default anyway).

    Having said all of that, your issue may be relate to this note, found in the reject explanation:

     

    Subsequent code in the current event in the current 
iRule or other iRules on the VS are still executed 
prior to the reset being sent.

     

    I recommend putting a return after the reject.

     

ekaleido's avatar
ekaleido
Icon for Cirrus rankCirrus
Jul 28, 2016

You need an datagroup that is essentially a whitelist. Host headers are user submitted, so the user can manipulate what is sent in. Try something like this..

datagroup would be a string type and would contain something like this:

www.example.com := www.example.com_pool

 

    when HTTP_REQUEST {
            set hostpool [class match -value [string tolower [HTTP::host]] equals datagroup_name
            if { $hostpool ne "" } {
                            pool $hostpool
                            HTTP::header replace Host [HTTP::host]
            } else {
                            discard
            }
     }