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Gurdip_Sira_172's avatar
Gurdip_Sira_172
Icon for Nimbostratus rankNimbostratus
May 05, 2016

Embedding javascript into pages help required

Hi,

 

I have a small javascript that I'd like to embed onto every page of my web application (SharePoint 2013). The js is to monitor the application end user experience. I've tried a number of approaches, like using stream profiles, iRules, etc, but it just does not seem to work (i.e. the result should be that in fiddler I see traffic to the management server). I've seen such strange behaviour such as the js is displayed on the page itself.

 

What's the best way to do this?

 

The script itself is this:

 

when RULE_INIT {
      set static::jscript {
          insert javascript code here
      }
}

when HTTP_REQUEST {
       Explicitly disable STREAM and COMPRESS by default for each request so it doesn't stay enabled for subsequent HTTP requests on the same TCP Connection
       Stream will be enabled explicitly upon JavaScript insertion
      STREAM::disable
      COMPRESS::disable

       If using F5 TM v 10.0 - 10.2.0, please comment out the HTTP::path line and uncomment HTTP:uri line to bypass a known issue where the query string is truncated if present 
       Logged with F5 as CR142756
       HTTP path is more efficient to use as HTTP uri includes the query string, so it is the default way to obtain the HTTP path

       set page_extension [string tolower [HTTP::uri]]
      set page_extension [string tolower [HTTP::path]]

    }

    when HTTP_RESPONSE {
          if { [HTTP::status] == 200 } {
                if {[HTTP::header value Content-Type] contains "text"} {
                      set stream_find ""
                      set stream_find_lower ""
                      set stream_repl ""
                      set insertJscript 1

 Do not allow the Javascript insertion if the pages end with the following
                  switch -glob $page_extension {
                        "*.ashx*" -
                        "*.asmx*" -
                        "*.axd*" -
                        "*.js*" {
                              set insertJscript 0
                        }
                        default {
                              if { [HTTP::payload] contains "META HTTP-EQUIV=\"Refresh\""} {
                                    set insertJscript 0
                              }
                        }
                  }

                  if {$insertJscript == 1} {
                        append stream_repl $static::jscript
                        append stream_expression "@$stream_find@$stream_find$stream_repl@"
                        append stream_expression "@$stream_find_lower@$stream_find_lower$stream_repl@"

                        STREAM::expression $stream_expression
                        STREAM::enable

                        set stream_expression ""

                  }
            }
      }

}
application delivery
iRules
LTM

1 Reply

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  • IanB's avatar
    IanB
    Icon for Employee rankEmployee
    May 12, 2016

    It looks like you've taken the script at https://devcentral.f5.com/codeshare?sid=741 and then removed the two patterns that are used to identify where the new content should be inserted.

    The important lines in that script are:

    append stream_repl $static::jscript
append stream_expression "@$stream_find@$stream_find$stream_repl@"
append stream_expression "@$stream_find_lower@$stream_find_lower$stream_repl@"

STREAM::expression $stream_expression

    This builds up a string containing "@pattern1@replacement1@pattern2@replacement2@", which tells it to find pattern1 and replace it with replacement1, and also find pattern2, and replace it with repalacement2.

    In the original script, pattern1 was $stream_find, which has a value of "". pattern2 was $stream_find_lower, with a value of "". The purpose of this was to locate the "" of the document, and replace it with "somereplacementvalue". It repeated this for the lower case,

    With your modifications:

    set stream_find ""
set stream_find_lower ""
set stream_repl ""

    The script is now looking for nothing, and trying to replace it. It doesn't find nothing, so this never matches. This can be trivially demonstrated as below:

    rule stream_test:

    when HTTP_RESPONSE {
    replace nothing with 'something'
   STREAM::expression "@@something@"
}

when STREAM_MATCHED {
   log local0. "[IP::client_addr]:[TCP::local_port]: matched: [STREAM::match]"
}

    If I apply that rule to a virtual server, and request a document, the document remains unchanged:

     curl http://172.16.218.100/test.html

HTML Document
This is an HTML document

    If I then modify the rule to replace the word 'Document' with the word 'Elephant', and request the same page, we see that the word Document is changed to Elephant (and 'document', with a lower case L is not changed). 

    STREAM::expression "@Document@Elephant@"


 curl http://172.16.218.100/test.html

HTML Elephant
This is an HTML document

    In addition, the log statement in the STREAM_MATCHED event also shows us in /var/log/ltm that the match was successful

    May 12 01:14:55 ltm-1200-211 info tmm1[8886]: Rule /Common/stream_test : 172.16.218.211:50937: matched: Document

    So in short, it's not matching because you can't match an empty string.