[plt-scheme] Cookies to web servlet getting lost when __utmz cookie present
Thanks, Jay and Todd. Very helpful.
It would certainly be nice if (request-cookies ...) didn't throw away all the cookies just because one of them has an ill-formed value.
--- nadeem
On May 3, 2010, at 10:09 PM, Todd O'Bryan wrote:
> Nadeem,
>
> You might try get-cookie from the net/cookie module.
>
> #lang scheme
> (require net/cookie)
> (require web-server/http/request-structs)
>
> (get-cookie "teaching-order" (headers-assq* #"cookie"
> (request-headers/raw req)))
>
> It looks like it works for your cookie, but it doesn't do so well with Google's.
>
> While I sympathize with Jay's desire to be true to the spec, it seems
> like there should be some way to deal with evil, non-compliant
> cookies, especially given that you have no control over them.
>
> Maybe use request-cookies first and then, if that ends up empty, check
> to see if there's a Cookie header and try a more forgiving parsing
> algorithm like the one Jay provided. If you come up with something
> that doesn't feel terribly hacky, please share!
>
> Todd
>
> On Fri, Apr 30, 2010 at 12:33 PM, Jay McCarthy <jay.mccarthy at gmail.com> wrote:
>> 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
>> _________________________________________________
>> For list-related administrative tasks:
>> http://list.cs.brown.edu/mailman/listinfo/plt-scheme
>>
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