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6 points by pg 4535 days ago | link | parent

Why don't you try it and see?

12 points by mr-anonymous 4535 days ago | link

Step 1: figure out where/what "MzScheme" is. Google is my friend, but a link to the site wouldn't hurt.

Step 2: figure out how to get the right version. Not hard, but a step.

Step 3: get the right architecture. Also not hard.

Step 4: run $RIGHT_PATH/bin/mzscheme -m -f as.scm

Step 5: figure out how to run "webapp.arc".

Step 5a: First attempt: "mzscheme -m -f as.scm webapp.arc" doesn't work.

Step 5b: Read documentation (what, I'm supposed to read it first?) and see pointer to "blog.arc"

Step 5c: Read header at top of blog.arc which says to run '(load "blog.arc")' followed by '(bsv)'. Okay, I can do '(load "webapp.arc")'

Step 5d: Figure out that '(bsv)' is the function name to start the server, and is specific to that blog code. I need to '(asv)' instead. w00t!

Step 5e: Go to localhost:8080 and find "it's alive". Figured out that I need to go to "localhost:8080/said" to get the web interface.

Step 6: Go to newly started server. Input my home town (contains a diacritic). Oops! The diacritic disappeared. The english spelling of the city's name is not the same as the real name minus the diacritic! Try it out yourself with "Espana" - including the tilde over the n (which you won't see here because this server stripped it away). The english name for spain is not "espana".

(Step 7: Mutter when repeated ^C don't kill the program; did a ^Z; kill %% rather than the (tl) (quit) needed to exit more gracefully.)

I tried various other special characters: the symbol for British pounds (GBP) gets turned into "GBP", the Japanese yen symbol (JPY) gets turned into "JPY". A grep finds this conversion done in "latin1-hack", which is indeed a hack.

Yet upper case sigma (∑) comes back without a problem, as does the traditional Chinese for China (中國). These are encoded through '&' escapes. So why do the Latin-1 hack at all?

Hmm, and the server doesn't specify a charset ... and it doesn't escape embedded text, so if I write "<b>this is not bold</b>" the HTML tags get interpreted.

In summary, the specification says that the final page displays "whatever [was] put in the input field". Yet the given solution does not display "A <GBP>" (that's "A-with-a-circle less-than-sign British-pound-sign greater-than-sign") correctly. The output is "A<GBP>" and the unknown HTML tag is not displayed, so I only see "A".

P.S. This server's session timed out before I finished typing in all of the above so I had to start a new comment and copy&paste from the old. Somewhat annoying.


3 points by mr-anonymous 4531 days ago | link

I take it that none of the arc people are worried that the arc solution to the challenge doesn't work? I can't write the symbol for the British pound or other high Latin-1 characters, and it doesn't escape correctly for display in HTML.

So far I've only seen a couple of people mention the lack of proper Unicode support and the huge XSS hole, and these were people who implemented the complete problem using some other language.

When will there be an arc program which implements the arc challenge?


1 point by jmatt 4531 days ago | link

PG has already addressed character sets. arc only supports ascii.

For further information see:



1 point by mr-anonymous 4531 days ago | link

Yes, I read those. But the point of the challenge is that the last page displays "whatever he put in the input field". I tried out the supposed arc answer to the challenge and it doesn't actually display what I put into the input field.

Try writing "The first conquistador in what is now the US was Juan Ponce de Leon and the last was Don Juan de Onate Salazar." There's an o-with-acute-accent in Leon, and there's an n-with-tilde in Onate).

Try writing "Noroveirusyking a HliX", which is a headline from today's MorgunblaXiX (a newspaper in Iceland).

Try writing "Don't use the <blink> element!"

Or try writing some of the other problems I pointed out earlier. (A parent to this comment.)

  * They do not work. *
If the challenge was "... as long as the input is in ASCII and doesn't include the '<' and '>' and '&' characters" then that's different. But that's not the challenge.

At the very least, raise an exception for out-of-range characters. The current code hacks some Latin-1 characters to ASCII, others to "X", and encodes characters >= 256 to &# escape codes. This is wrong.

To which kens added that because the server doesn't set the content-type encoding, if the browser autodetects the ASCII as being utf-7 then there's another possible attack.


1 point by mr-anonymous 4530 days ago | link

Now I should be able to speak properly.

XSi! Antligen! Tschuss!