Forum Discussion

Altostratus

Oct 27, 2023

Want to block URI containing # special character but the irule doesnt work

Hi Gents, If some experts can help me to find the reason that why the below URI are not blocking using the irule below. What I understand till now that "#" in the URI doesnt match the irule conditio...

MVP

Hi,

Yes, you're completely right, these links that contain a hash sign are not being forwarded from the browser to the server. But the solution below might help you out. The iRule below needs to be attached to a virtual server with the STREAM-profile enabled. It wil inject a little bit of javascript that inspects all links that are being clicked. When the link contains a hash sign, it will redirect the browser back to the F5.

when HTTP_REQUEST {
    # Disable the stream filter by default   
    STREAM::disable 
 
    # LTM does not uncompress response content, so if the server has compression enabled
    # and it cannot be disabled on the server, we can prevent the server from
    # sending a compressed response by removing the compression offerings from the client
    HTTP::header remove "Accept-Encoding"
    
    if { [HTTP::uri] starts_with "/f5/anchor_link_redirect" } {
        set href [b64decode [URI::query [HTTP::uri] href]]
        HTTP::respond 200 content "<html><head><title>Anchor Link Redirect</title></head><body>User clicked on link that contains a hash sign: $href</body></html>"
    }
}
	
when HTTP_RESPONSE {
    if { ([HTTP::header "Content-Type"] starts_with "text/html") } { 
        STREAM::expression {@</title>@</title>
    <script>
    document.addEventListener(`click`, e => {
      const origin = e.target.closest(`a`);

      if (origin && origin.href.indexOf('#') > -1) {
        const base64_href = btoa(origin.href);
        window.location.href = '/f5/anchor_link_redirect?href=' + base64_href;
      }
    });
    </script>@}
        STREAM::enable
    }
}

The iRule will show the following output, when a link with a hashtag is clicked.