Forum Discussion

Vadym_Chepkov's avatar
Vadym_Chepkov
Icon for Nimbostratus rankNimbostratus
Mar 05, 2021

How to preserve HTTP headers for HTTP::respond

I need to preserve HTTP headers for HTTP::respond, I tried the following approach when HTTP_RESPONSE { if {[HTTP::has_responded]} {return} catch { unset hdrs } foreach header [HTTP::header ...
application delivery
iRules
Simon_Blakely's avatar
Simon_Blakely
Icon for Employee rankEmployee
Mar 08, 2021

Vadym,

HTTP::respond does not allow variables to be expanded and evaluated in the context of the command execution.

You will need to use eval. However, this introduces the risk of a TCL injection vulnerability. 

when HTTP_RESPONSE {
  if {[HTTP::has_responded]} {return}
  catch { unset hdrs }
  foreach header [HTTP::header names] {
    lappend hdrs $header "[HTTP::header $header]"
  }
  log local0. "Headers: $hdrs"
  eval HTTP::respond 301 -version auto $hdrs
}

You may also need to play with quoting the values.

  • Vladimir_Akhmarov's avatar
    Vladimir_Akhmarov
    Icon for Cirrus rankCirrus
    Aug 08, 2023

    Hello Simon

     

    Tried this approach for modified Exchange iRule to logout user and sometimes I caught connection reset inside browser (but there is no TCL error inside LTM logs). So I cannot understand why "eval {}" with variable leads to connection errors compared with regular HTTP::respond header1 value1 header2 value2 ...

    My code

    when RULE_INIT priority 500 {
    set static::hdrs [list \
        "\"Location\" \"/vdesk/hangup.php3\"" \
        "\"Content-Type\" \"text/html\"" \
        "\"Cache-Control\" \"no-cache, must-revalidate\"" \
        "\"Set-Cookie\" \"MRHSession=deleted;expires=Thu, 01-Jan-1970 00:00:00 GMT;path=/;secure\"" \
        "\"Set-Cookie\" \"LastMRH_Session=deleted;expires=Thu, 01-Jan-1970 00:00:00 GMT;path=/;secure\"" \
        "\"Set-Cookie\" \"cadata=null;Expires=Thu, 01-Jan-1970 00:00:00 GMT;path=/;secure\"" \
        "\"Set-Cookie\" \"ClientId=null;Expires=Thu, 01-Jan-1970 00:00:00 GMT;path=/;secure\"" \
        "\"Set-Cookie\" \"UC=null;Expires=Thu, 01-Jan-1970 00:00:00 GMT;path=/;secure\"" \
        "\"Set-Cookie\" \"X-BackEndCookie=null;Expires=Thu, 01-Jan-1970 00:00:00 GMT;path=/;secure\"" \
        "\"Set-Cookie\" \"X-OWA-CANARY=null;Expires=Thu, 01-Jan-1970 00:00:00 GMT;path=/;secure\"" \
    ]
}

when HTTP_REQUEST priority 500 {
    ...
    eval {HTTP::respond 302 -version 1.1 noserver "[join $static::hdrs]"}
    ...
}

when ACCESS_SESSION_STARTED priority 500 {
    ...
    eval {ACCESS::respond 302 -version 1.1 noserver "[join $static::hdrs]"}
    ...
}

     

    Do you know maybe there are some gotchas that should be included in the code?