Rewrite Existing Client Cookie

I think something like this would allow you to change the cookie value. Sorry, I don't have a good way to test this out at the moment.

when HTTP_REQUEST {

 Check if the cookie exists in request
if { [HTTP::cookie exists "cookie-name"] } {

 Change cookie's value
HTTP::cookie [value]  [string]
   }
}

Posted By naladar on 08/09/2010 11:42 AM

I think something like this would allow you to change the cookie value. Sorry, I don't have a good way to test this out at the moment.

when HTTP_REQUEST {

 Check if the cookie exists in request
if { [HTTP::cookie exists "cookie-name"] } {

 Change cookie's value
HTTP::cookie [value]  [string]
   }
}

Since this is in the HTTP_REQUEST event, this would just be replacing it from the F5 to the pool member, right?

That is correct. To modify the cookie coming from the server going to the client you would have to use when HTTP_RESPONSE. Here is a good URL for a Wiki article talking about encrypting cookies, in which they describe how to change the values of the cookies.

Posted By naladar on 08/09/2010 12:19 PM

 

That is correct. To modify the cookie coming from the server going to the client you would have to use when HTTP_RESPONSE. Here is a good URL for a Wiki article talking about encrypting cookies, in which they describe how to change the values of the cookies.

 

 

I think you may have forgotten the link. :-P

From RFC2109:

 

 

 

4.3.3 Cookie Management

 

 

 

If a user agent receives a Set-Cookie response header whose NAME is

 

the same as a pre-existing cookie, and whose Domain and Path

 

attribute values exactly (string) match those of a pre-existing

 

cookie, the new cookie supersedes the old. However, if the Set-

 

Cookie has a value for Max-Age of zero, the (old and new) cookie is

 

discarded. Otherwise cookies accumulate until they expire (resources

 

permitting), at which time they are discarded.

 

 

 

So you can overwrite an existing cookie value by setting a new cookie with the same name, domain and path as the prior cookie. You can do this in HTTP_RESPONSE using HTTP::cookie insert name < name > value < value >.

 

 

Aaron

Posted By hoolio on 08/09/2010 02:49 PM

From RFC2109:

4.3.3 Cookie Management

If a user agent receives a Set-Cookie response header whose NAME is

 

the same as a pre-existing cookie, and whose Domain and Path

 

attribute values exactly (string) match those of a pre-existing

 

cookie, the new cookie supersedes the old. However, if the Set-

Cookie has a value for Max-Age of zero, the (old and new) cookie is

discarded. Otherwise cookies accumulate until they expire (resources

permitting), at which time they are discarded.

So you can overwrite an existing cookie value by setting a new cookie with the same name, domain and path as the prior cookie. You can do this in HTTP_RESPONSE using HTTP::cookie insert name < name > value < value >.

Aaron

Thanks as always! I'm currently doing just this but have noticed my browser showing multiple cookies and as I use the "expire at browser close" default, I wasn't entirely sure how the F5 would handle a user with 2 "example" cookies. So, if I have an iRule like the following:

when HTTP_REQUEST {
if {  [HTTP::cookie "example"] eq 1 } {
pool 1 
} elseif { [HTTP::cookie "example"] eq 2 } {
pool 2 } 
}

and the user has 2 "example" cookies, with the most recently inserted being "2", it would send the user to pool 2?

Based on a little experience with this and reading the RFC, if you're setting the cookie correctly from LTM, it should overwrite the pre-existing cookie with the new value. If that's what you want to happen and it's not, I'd try investigating that issue further rather than try to determine which cookie in the request is the "correct" one.

 

 

With HTTP::cookie, it doesn't seem like there is a simple way to handle two different cookies with the same value. With headers you can use 'HTTP::header values $header_name' to get the values for multiple instances of the same header. It's also worth noting that you can't differentiate between two cookies set with a different path or domain on requests as the client only includes the cookie name and value--not any of the properties that the cookies were set with.

 

 

Aaron

Hi Aaron, HTTP::cookie insert name < name > value < value >

 

That will insert a new cookie name and it will not over write the existing one.

 

~Rami