[plt-scheme] Cookies to web servlet getting lost when __utmz cookie present

Fri Apr 30 12:33:54 EDT 2010

On Fri, Apr 30, 2010 at 10:12 AM, Nadeem Abdul Hamid <nadeem at acm.org> wrote:
> Thanks, Jay.
>
> That's kind of annoying though -- I mean I can't do anything about the
> cookies that Google requests the browser to set when other pages on
> the domain are visited. And I tried different browsers -- the same
> problem. Why would Google Analytics be setting invalid cookies? (A
> search doesn't seem to turn up any relevant hits, or anyone else every
> experience this issue.)

I don't know why they write buggy programs. I've submitted a bug
report the last time this exact problem came up.

> So basically, I need to parse the headers for cookies in my own program?

It's not that bad. Here's something that does what Ruby does for
parsing cookies. [Note that Ruby allows a value like the one've sent
to be interpreted as a cookie, even though it is not.]

#lang scheme
(define ex #"teaching-order=course;
__utmz=165257760.1272597702.1.1.utmcsr=(direct)|utmccn=(direct)|utmcmd=(none)\r\n")

(define (not-cookie-parse s)
  (for/fold ([cookies (make-immutable-hash empty)])
    ([key*val (in-list (regexp-split #rx"[;,][ \t]*" s))])
    (match-define (list _ key val) (regexp-match #rx"^([^=]*)=(.*)$" key*val))
    (hash-update cookies key
                 (curry append (regexp-split #rx"&" val))
                 empty)))

(not-cookie-parse ex)
=>
#hash((#"teaching-order" . (#"course")) (#"__utmz" .
(#"165257760.1272597702.1.1.utmcsr=(direct)|utmccn=(direct)|utmcmd=(none)\r\n")))

Jay

>
> --- nadeem
>
>
> On Fri, Apr 30, 2010 at 12:26 AM, Jay McCarthy <jay.mccarthy at gmail.com> wrote:
>> Hi Nadeem,
>>
>> The problem is that this:
>>
>> "teaching-order=course;
>> __utmz=165257760.1272597702.1.1.utmcsr=(direct)|utmccn=(direct)|utmcmd=(none)\r\n"
>>
>> is not a valid cookie. In particular, the characters to the right of
>> the second "=":
>>
>> "165257760.1272597702.1.1.utmcsr=(direct)|utmccn=(direct)|utmcmd=(none)\r\n"
>>
>> should be a VALUE, which is a value, which is either a token or a quoted-string.
>>
>> It is not a token because it contains "(", ")", and "=".
>>
>> It is not a quoted-string because it is not wrapped in "".
>>
>> The Web Server does not throw an exception when it is asked to parse
>> an invalid cookie string, instead it returns the empty list of
>> cookies. You can look at the request's headers directly to do
>> something to this header, but since it is not a cookie, the Web
>> Server's cookie parsing cannot do anything with it.
>>
>> For Reference:
>>
>> http://tools.ietf.org/html/rfc2965 [for VALUE and value]
>> http://tools.ietf.org/html/rfc2616 [for token and quoted-string]
>>
>> Jay
>>
>> On Thu, Apr 29, 2010 at 10:05 PM, Nadeem Abdul Hamid <nadeem at acm.org> wrote:
>>> Hello all,
>>>
>>> I've been experimenting with a simple servlet to drive my website, but am having a strange problem with cookies not getting through when a Google Analytics cookie (__utmz) is present in the browser's request to the servlet. I've included a step-by-step trace below, but briefly, here's the problem: Starting from an empty browser cache of cookies, I request a page from my servlet that sets a cookie; when I then request a page again, I see that the cookie is sent by the browser and received by the servlet. However, then I visit another web page on the same domain as my servlet, which sets a __utmz (apparently a Google Analytics cookie). After this cookie is set, when I request pages from my servlet, I see that the browser is sending all the cookies, but none are getting through to the servlet! If I clear the __utmz cookie from the browser, and then request pages from the servlet, the servlet receives the cookie again.
>>>
>>> So, I haven't peeked into the webserver code (no time yet), but the question is: is there some reason that the __utmz cookie (and not any other __utma, __utmc, cookies) seems to cause interference with all other cookies getting through to it?
>>>
>>> Below are the steps that I take to replicate this problem, as well as snippets from my code. I added some terminal output to the servlet dispatch function that is passed to serve/servlet so that it displays the cookies it receives and the URL being requested before doing anything else.
>>>
>>> I appreciate any help/insight. Thanks,
>>>
>>> --- nadeem
>>>
>>>
>>> **************************************************************
>>> (Step 1)
>>> Browser request (sniffed using Wireshark):
>>>   GET /~nhamid/teaching/ HTTP/1.1\r\n
>>>   (no cookies sent)
>>>
>>> Servlet output:
>>>   ()/~nhamid/teaching/
>>>
>>>
>>> (Step 2)
>>>   request page that sets a cookie (and redirects to /~nhamid/teaching/course…)
>>>
>>>
>>> (Step 3)
>>> Browser request:
>>>   GET /~nhamid/teaching/course HTTP/1.1\r\n
>>>   Cookie: teaching-order=course\r\n
>>>
>>> Servlet output:
>>>   ((teaching-order course #f #f))/~nhamid/teaching/course
>>> (See the cookie is received.)
>>>
>>>
>>> (Step 4) visit another page (www.berry.edu) -- sets __utmz (google analytics cookie) and a bunch of others, which I cleared out, except for the __utmz one.
>>>
>>>
>>> (Step 5)
>>> Browser request:
>>>   GET /~nhamid/teaching/ HTTP/1.1\r\n
>>>   Cookie: teaching-order=course; __utmz=165257760.1272597702.1.1.utmcsr=(direct)|utmccn=(direct)|utmcmd=(none)\r\n
>>>
>>> Servlet output:
>>>   ()/~nhamid/teaching/
>>> (Note: no cookies received at all!)
>>>
>>>
>>> (Step 6) delete the __utmz cookie from the browser. This is the *only* thing I change.
>>>
>>>
>>> (Step 7)
>>> Browser request:
>>>   GET /~nhamid/teaching/ HTTP/1.1\r\n
>>>   Cookie: teaching-order=course\r\n
>>>
>>> Servlet output:
>>>   ((teaching-order course #f #f))/~nhamid/teaching/
>>> (Cookie is received again!)
>>>
>>> **************************************************************
>>>
>>> Scheme code:
>>>
>>> (serve/servlet my-dispatch
>>>               #:listen-ip #f
>>>               #:launch-browser? #f
>>>               #:servlet-path "/nhamid/index.ss"
>>>               #:servlet-regexp #rx""
>>>               #:extra-files-paths (list htdocs)
>>>               #:stateless? false)
>>>
>>> (define-values (web-dispatch web-url)
>>>  (dispatch-rules
>>>   [("~nhamid" "index.ss") render-home]
>>>   [("~nhamid") render-home]
>>>   [("~nhamid" "") render-home]
>>>   [("~nhamid" "editlinks") render-editlinks]
>>>   [("~nhamid" "teaching" "") render-teaching]
>>>   [("~nhamid" "teaching" "semester") render-teaching-by-semester]
>>>   [("~nhamid" "teaching" "course") render-teaching-by-course]
>>> ))
>>>
>>> (define (display-cookies req)
>>>  (let ([cookies (request-cookies req)])
>>>    (display
>>>    (map (lambda (c) (list (client-cookie-name  c)
>>>                           (client-cookie-value c)
>>>                           (client-cookie-domain c)
>>>                           (client-cookie-path c)))
>>>         cookies))))
>>>
>>> ;; my-dispatch : request -> response
>>> (define (my-dispatch req)
>>>  (display-cookies req)
>>>  (display (string-append (url->string (request-uri req)) "\n"))
>>>  (web-dispatch req))
>>>
>>>
>>> _________________________________________________
>>>  For list-related administrative tasks:
>>>  http://list.cs.brown.edu/mailman/listinfo/plt-scheme
>>>
>>
>>
>>
>> --
>> Jay McCarthy <jay at cs.byu.edu>
>> Assistant Professor / Brigham Young University
>> http://teammccarthy.org/jay
>>
>> "The glory of God is Intelligence" - D&C 93
>>
>
>
>
> --
> Nadeem Abdul Hamid
> Assistant Professor, Computer Science
> Berry College
> PO Box 5014
> 2277 Martha Berry Hwy NW
> Mount Berry, GA 30149-5014
> (706) 368-5632
> http://cs.berry.edu/~nhamid/
>

-- 
Jay McCarthy <jay at cs.byu.edu>
Assistant Professor / Brigham Young University
http://teammccarthy.org/jay

"The glory of God is Intelligence" - D&C 93